Biology: Classification

Explain the meaning of the term species

- members of a population that can interbreed

- to produce fertile offspring

- they occupy a particular niche

Methods of determining the species which can be used to interbreed

- Morphological - structural features (easiest and quickest to compare but can not cataegorise based on this alone)

- Physiological - they way the body works

- Biochemical - includes the sequence of bases in DNA and the sequence of amino acids in proteins

- Behavioural

Classification: the process of sorting living things into groups

Taxonomy: the study of the principles of classification

Phylogeny: the study of the evolutionary relationships between organisms

Why do we classify things?

• To put things in order to sort them out
• there are nearly 2 million different species of living organisms
• Each species must be placed in a group of similar organisms
• It is for our convenience
• to make the study of living organisms more manageable
• to make it easier to identify organisms
• to help us see the relationship between the species

Classification

Domain        Eukaryotae       Few feautures in common

Kingdom      Animalia            members show more diversity

Phylum        Chordata

Class            Mammalia

Order           Primate

Family          Hominidae

Genus          Homo

Species        Sapiens              more features in common - member shows similarities 

Taxonomy

• A 'taxon' is a unit of classification
• A 'species' is the smallest taxon = basic unit of classification
• Groups of similar species form the next taxon 'genus'
• Groups of similar genera form a 'family'
• Etc. up to the largest taxon, domain.

Difference between phyla are major - easy to decide which one organisms belong to

Chordata - central bundle f nerves running along back

Arthropods - have hard exoskeleton

                 - are subdivided into classes e.g. class insects

The species are classified based on the evolutionary relationships, they are grouped together based on shared, homologous features

These features are similar enough that they have to come forma  similar design e.g. vertebrates have similar limb bones, 1 bone in upper limb, 2 bones in lower limb

AS Biology F212: Smoking and Heart Disease

Cigarette smoke contains over 4000 different chemicals, many of them are toxic. Three main components posing a danger to human health: Tar, Carbon Monoxide and Nicotine.

Tar

• Tar coats the airways and alveoli
• it can cause allergic reactions which narrows the airways
• it also destroys the cilia on the surface
• mucus cannot be moved
• tar stimulates production of extra mucus
• bacteria get stuck in the mucus and multiply in the airways
• the smoke has an increased risk of infection

• chronic bronchitis
• this is the disease caused by the inflammation of the airways
• accompanied by mucus collecting in the lungs
• symptoms
• irritation
• continual coughing
• coughing up mucus
• risk of lung infection
• long term effects
• frequent infections damages the lining of lungs
• white blood cells are attracted
• have to make their way from blood to airways
• use enzymes to dissolve their way through
• elastase enzyme dissolved the elastic tissue
• airways no longer recoil properly
• bronchioles collapse trapping air
• alveoli burst due to pressure of trapped air 

• Emphysema
• disease caused by alveoli bursting
• lungs have less surface area
• so can do less gas exchange
• healthy lungs contains large quantities of elastic tissue, mostly made up of the protein elastin.
• this tissue stretches when we breathe and in and springs back when we breathe out.
• in emphysematous lungs, the elastin has become permanently stretched and the lungs no longer able to force out all the air from the alveoli
• the surface area of the alveoli is reduced and they sometimes burst
• as a result, little if any exchange of gases can take place across the stretched and damaged air sacs.
• symptoms
• shortness of breath - results from difficulty in exhaling air due to the loss of elasticity in the lungs
• if the lungs cannot be empties much of their air, then it is difficult to inhale fresh air containing oxygen so patient feels breathless
• the smaller the alveolar surface area leads to reduce levels of oxygen in the blood and so patient tries to increase oxygen supply by breathing more rapidly
• chronic coughs - consequence of lung damage and the body's effort to remove the damaged tissue and mucus that cannot be removed naturally because the cilia on the bronchi and  bronchioles has been destroyed
• bluish skin colouration is due to low levels of O2 in the blood as a result of poor gas diffusion in the lungs

• Asthma
• common allergen which can trigger an asthma attack: pollen, dust mites, mould, pet dander
• asthma is an example of localised allergic reaction
• it can also be triggered or made worse by a range of factors, including air pollutants e.g. sulphur dioxide) exercise, cold air, infection, anxiety and stress.
• one or more of these allergens causes white blood cells on the lining of the bronchi and bronchioles to release a chemical called histamine
• effects of histamine - the lining of these airways become inflamed
• the cells of the epithelial lining secret larger quantities of mucus and enter the airways
• the muscle surrounding the bronchioles contracts and so constrict the airways.
• symptoms:
• difficulty in breathing - due to constriction of bronchi and bronchioles, their inflamed linings and the additional mucus and fluid within them
• a wheezing sound when breathing is caused by air passing through the very constricted bronchi and bronchioles
• a tight feeling in chest - consequence of not being able to ventilate the lungs adequately because of constricted bronchi and bronchioles
• coughing - reflex response to obstructed bronchi and bronchiole in effort to clear them

Chronic obstructive pulmonary disease

• combination of diseases including emphysema, chronic bronchitis and asthma

Lung Cancer

• cancers are caused carcinogens
• cigarette smoke contains many carcinogens
• carcinogens are present in tar
• they enter the cells of the lungg tissue
• they mutate the DNA in their nuclei
• if the gene for the cell division is mutate then uncontrolled cell division takes place - this is cancer
• lung cancer can take up 20-30 years to develop to a size to cause problems
• symptoms
• coughing up blood
• persistent cough
• weight loss
• shortness of breath
• chest pains
• Nicotine and Carbon monoxide
• these two chemicals can be absorbed in the lungs and enter the blood
• here they cause cardiovascular disease
• Nicotine
• causes addiction
• causes release of adrenaline
• thus increased heart and breathing rate
• increased force of contraction of the heart
• constriction of arterioles
• hypertension
• increases stickiness of platelets
• chance of thrombus (clotting)
• increased blood cholesterol and LDLs
• Carbon monoxide
• combine with haemoglobin
• forms carboxyhaemoglobin
• haemoglobin has higher affinity for CO than O2
• this is irreversible
• reduces O2 carrying ability of haemoglobin
• decrease in oxygen transported
• tissues starved of oxygen
• also damages lining areteries

Cardiovascular Disease

• atherosclerosis
• nicotine and CO damages artery walls
• hypertension contributes to the damage
• this attracts phagocytes to repair the damage
• these encourage the growth of smooth muscles and deposition of fatty substances
• fatty deposits are laid down when repaired including cholesterol
• these atheromas form plaques
• these narrow artery
• also make it rougher
• this reduced blood flow
• thrombosis
• blood flows slower past plaques
• combined with stickier platelets from nicotine - blood clots can form
• these block narrow arteries
• this may result in formation of blood cot, or thrombus, in a condition aka thrombosis
• this thrombus may block the blood vessel, reducing or preventing the supply of blood to tissues beyond it
• the region of tissue deprived of blood often dies as a result of the lack of oxygen glucos and other nutrients blood normally provides
• embolism is when the thrombus is carried from its place of origin and blocks another artery
• coronary heart disease
• when the atherosclerosis occurs in the coronary arteries and reduces/stop oxygen supply to the cardiac muscle for respiration
• Angina: severe chest pain due to lack of oxygen
• Heart attack: death of part of the heart muscle due to a blockage of artery
• Heart failure: heart stops pumping due to lack of oxygen by a blockage of major coronary artery
• Risk factors
• age - older 
• sex - male
• diet high in saturated fats causes more LDLs
• plaque formation
• blood cholesterol 
• high salt intake
• hypertension
• low fibre
• obesity
• heavy alcohol consumption
• and more
• stroke
• death of part of the brain
• due to blood clot forming in artery supplying brain
• artery supplying brain bursts (aneurysm)
• aneurysm
• atheromas that lead to the formation of a thrombus also weaken artery walls
• these weakened points swell to form a balloon-like blood filled structure -  aneurysm
• frequently burst leasing to haemorrhage and therefore loss of blood to the region of the body served by that artery
• a brain aneurysm is know as a stroke

Cardiovascular diseases

• great cause of premature death
• CHD and stroke often result from atherosclerosis
• this can start in adolsescence

Treatment

• is expensive
• long term drug treatment to reduce blood pressure and cholesterol
• surgery
• therefore reduction in atherosclerosis through the reduction of risk factors is important

immunity

Person gets a splinter
- triggers a non specific inflammatory response in the region on puncture
- histamine chemical is released
- dilate the capillary in diameter and it becomes leaky
- tissue around the splinter becomes red and swollen as plasma leak in tissues

Damaged or infected tissue release proteins and other chemicals
- attracts phagocytes to the area
- advantage of leaky capillaries - white blood cells (phagocytes/neutrophils) leave capillaries easily
- phagocytes engulf the dead cell and bacteria

Cells of the immune system

• All orignate from the bone marrow
• All are leukocytes = white blood cells
• 2 main groups:
• phagocytes - neutrophils an macrophages
• lymphocytes - B and T lymphocytes
• Phagocytes - engulfs dead cells and invading micro-organism
• Neutrophils
• short live
• smaller than macrophages
• travel around the body in the blood
• squeeze through walls of capillaries
• have a lobed nucleus
• Monocytes/macrophages
• large and long lived
• circulate in blood as monocytes which then settles in organs such as lungs lymph nodes
• develop into macrophages that remain in the organ
• remove foreign matter from organs
• initiate specific immune response

Immune system

2 Parts:

• Non specific immunity
• 2nd line of defence
• immediate attack against a variety of 'attackers'
• present from birth
• does not distinguish between different pathogens
• same response each time
• e.g. phagocytosis (engulfing) and inflammation
• specific immunity
• 3rd line of defence
• body's response is tailored for a specific 'attacker'
• involves lymphocytes and antibodies
• response is slow when it meets the pathogen for the first time
• involves white blood cells particularly B lymphocytes which produce chemicals called antibodies which target specific pathogens

Antigens

• all cells have surface markers called antigens
• antigens are molecules that stimulate an immune response causing the production of antibodies 
• antibodies are specific to antigen
• the body can recognise antigen as self or non-self (foreign)
• our own antigen do not stimulate a immune response

Antibodies

• Y shaped molecules
• made of 4 polypeptide chains held together by disulphide bridges
• 2 identical short or light chains
• 2 identical long or heavy chains
• consists of two regions
• constant region - same in all antibodies
  enables antibodies to attach to phagocytes and helps in the process of phagocytosis
• variable region, differs from one type to another - result of amino acid sequence which is complementary to shape of antigen
• hinge region allows the molecule to bend so the branches of the Y shaped molecule can move further in order to allow attachment to more than one antigen

Lymphocytes

• involved in specific immune response
• have a large nucleus which fills most of the cell
• 2 types:
• B lymphocytes
• matures in the bone marrow
• T lymphocytes
• mature in the Thymus gland
• both must be mature before they can take part in the immune response.
• during maturation both B and T lymphocytes  develop receptors on their cells surface membrane.
• these specific receptors are able to combine with specific antigen in much the same way that an enzyme combines with a specific substrate
• Humans can produce several million different types of B and T cells (initially only a few of each types)
• B and T cells circulate between the blood and lymph so are distributed around the body where they may come in contact with antigens

Maturation of B and T cells

• In the bone marrow immature B and T cells divide by mitosis
• B cells matures in the bone marrow
• mature B cells each with a different antibody receptor on cell membrane
• T cells mature in the thymus
• mature T cells each with a different T cell receptor on the membrane

B lymphocytes

• many different types of each capable producing an antibody (=protein) that acts against a particular antigen
• when a pathogen enter the body, B cells with the appropriate receptors bind to the antigens = clonal selection.
• causing them to divide rapidly by mitosis to form a large clone of identical cells = clonal expansion.
• The selected B cells differentiate into 2 types of cells
• plasma cells
• produce antibodies, several thousand/second
• antibodies are secreted into the blood
• plasma cells are short lived (several weeks)
• memory cells
• long live (several years)
• remain dormant in the blood
• ready to respond immediately to further attacks by antigen
• providing an immunological memory.

The cells of the immune system originates from bone marrows where stem cells divide by mitosis to produce cells that differentiate into lymphocytes and phagocytes. Immature T lymphocytes migrate to the thymus gland where they mature. Mature B lymphocytes and mature T lymphocytes circulate and enter lymph nodes. During an immune response some B lymphocytes differentiate into plasma cells and secrete antibodies.

AS Biology F212: Vaccines

A vaccine is a preparation containing antigenic material (e.g. antigens)

Vaccination confers artificial active immunity. (Entry of antigenic material into the body stimulates an immune response, memory cells are produce)

Types of vaccination

1. Live vaccine e.g. Smallpox
   The live vaccine - less harmful pathogen but with similar antigens and can still be induce active immunity
2. Harmless vaccine e.g. measles, TB
   Harmless or attenuated version of the pathogen
3. Dead vaccine e.g. Cholera vaccine
   the pathogen has been killed either by exposure to or chemicals
4. Antigens e.g. hepatitis B
   Preparation of antigens from a pathogen
5. Toxoid vaccine e.g. tetanus
   vaccine consists of harmless form of toxin produced by the pathogen

Herd vaccination

• providing immunity to almost all of the population at risk
• with enough people immune the disease cant spread
• level of immunity needed varies depending on the disease (80-85% for small pox, 95% for measles)

Ring vaccination

• used when a  new case s reported
• vaccinate everyone in the immediate vicinity (house, village, or town)

AS Biology F212: Immunity

Primary defences

• These prevent the pathogen from entering the body
• These mechanisms have evolved through selection and are considered as adaptations

Barriers to entry

• The skin
• the skin covers the body surface providing a physical barrier that most pathogens find hard to penetrate
• Keratinocytes
• cells produced by mitosis at the base of the epidermis
• they migrate to the skins surface
• they dry out and the cytoplasm is replaced by keratin = keratinisastion
• this prcess take about 30 days
• by the time they reach the surface they are dead and everntally slough off
• Mucous membrane
• produced by the epithelial layer traps pathogens
• epithelial layer contains goblet cells
• these produce mucus that lines the airways trapping pathogens
• ciliated cells move the mucus up the oesophagus so it can be swallowed
• pathogens are killed by the acidity of the stomach (pH 1-2) which denatures their enzyme
• Mucus membranes are also found in the gut, ears and nose
• Hydrochloric acid in the stomach provides a low pH that the enzymes of most pathogens are denatured and therefore the organisms are killed

Secondary Defence

• Phagocytes (non-specific)
• Neutrophils - most common
• have multi-lobed nucleus and are produce in the bone marrow
• they are found in the blood and tissue fluid and may also be found on epithelial surfaces such as the lungs
• short lied but are released in large numbers
• Macrophage - larger than neutrophils
• manufactures in the bone marrow
• travels in the blood as monocytes
• they tend to settle in the body organs particularly the lymph nodes
• here they develop into macrophages
• they plan an important part in specific response to pathogens
• The role of macrophages
• infected cells release histamine
• this attract neutrophils
• it also causes capillaries to become more leaky
• as a result more fluid leaves the capillaries in the area of infection
• so more fluid passes the lymphatic system
• this leads the pathogen towards the macrophages in the lymph nodes
• How phagocytes work
• they engulf and destroy pathogenic cells
• these have chemical markers on their outer membranes = antigens
• these are recognised as non-self or foreign
• these are specific to pathogen
• Phagocytosis
• once bound the phagocytes envelopes the pathogen by folding its membrane inwards
• the pathogen is trapped within a phagosome
• lysosome fuse with phagosome and release enzymes lysins
• these digest the pathogen producing harmless products that can be absorbed

Specific immune response

T and B lymphocytes

• these have receptors that are complementary to the foreign antigen
• this antigen may be attached to the pathogen or on the surface of the host cell
• when antigen is detected, the lymphocyte is activated

"Describe the changes that occur to T lymphocytes during an immune response. Explain the roles of T lymphocytes in fighting infection by a pathogen, such as a virus"

• reference to antigen presentation - described
• receptors on T cell surface or complementary to the antigen
• reference to specificity in context of T cells
• clonal selection - described
• clonal expansion/T cells divide by mitosis
• T helper cells release cytokines
• stimulates B cells to divide/clone/differentiate
• stimulate macrophage to carry out phagocytosis
• T/Killer cells search and kill infected host cells
• secrete enzymes
• named enzyme
• active immunity
• memory T cells/immunological memory
• secondary response - more rapid

Antigen

• Usually large proteins or glycoproteins
• specific shape
• the antigen is specific to the pathogen
• a foreign antigen stimulates the production of antibodies = an immune response
• there is one type of antibody for one type of antigen

Antibodies

• produced by lymphocytes (WBC)
• are large proteins also known as immunlglobulins
• they have specific shape tat is complementary to particular antigen
• these antibodies are specific to the antigen
• therefore the antibody is specific to the pathogen
• antibodies attach to antigens and render them harmless

Antibody structure

• the constant region is the same on all antibodies
• this allows the attachment of phagocytic cells during phagocytosis 
• the variable region has a specific shape and differs from one type of antibody to another
• this is due to its amino acid sequence
• this makes it complementary to a particular antigen
• this allows it to bind to the antigen
• the hinge region allow flexibility 

Antigens, antibodies and phagocytosis

• the presence of a foreign antigen can trigger the production of antibodies
• antibodies (proteins) in our blood attach to foreign antigens (antigen-antibody complex)
• phagocytes have membrane bound receptor proteins
• these can bind to the antibody antigen complex
• allows the recognition of the pathogen

How antibodies work - neutralisation

• the antigen in the pathogens cell surface membrane may be used as a binding site
• this would allow it to bind to host cells
• if the antibody blocks this binding site then the pathogen cannot bind to the host cell
• this is called neutralisation 

Agglutination

• some antibodies are larger than those previously described
• they resemble several Y shaped molecules attached together with many specific variable region
• each one can bind to an antigen on a pathogen
• the attachment to many pathogens at the same time is called agglutination
• the pathogens cannot enter host cells

Producing antibodies

• Infection = antibody production
• It takes a few days before antibody levels are high enough to successfully combat the infection
• This is the primary immune response
• antibodies do not stay in the blood
• if the body is infected a second time by the same pathogen, the antibodies must be made again
• however, the production is faster and the concentration is higher
• this is the secondary immune response

Communication between cells

Cell signalling

• Communication is achieve through sell surface molecules and through the release of hormone like chemicals called cytokines
• the target cell must have a cell surface receptor

What information is communicated

• Identification - the pathogen carries antigen that identify it as foreign 
• Distress signals - these are produce when a cell becomes infected by a pathogen
• lysosomes breaks down the infecting pathogen
• parts of the pathogen end up attached to the host cells plasma membrane (antigen presentation)
• these can act as a distress signal that can be detected by other cells
• or they can act as markers so the infect host cell can be destroyed by T killer cells
• Antigen presentation
• macrophages engulf pathogens by phagocytosis
• they do not fully digest them
• they incorporate the antigen into their cell surface membrane 
• they become known as antigen-presenting cells
• its function is to find the lymphocyes that can neutralise that particular antigen
• Instructions
• chemicals called cytokines act as instructions to target cells
• they bind to specific receptors
• this causes the release of second messengers inside the cells
• e.g. macrophages release monokines to attract neutrophils
• macrophages release monokines to stimulate B lymphocytes to release antibodies
• T and B lymphocytes release interleukins which stimulate the proliferation and differentiation of T and B lymphocyte
• Many cells release interferon which can inhibit virus replication and stimulate killer T cells

AS Biology F212: Malaria

Malaria is caused by the protoctist Plasmodium. The vector for malaria is female Anopheles mosquitoes

Transmission

• Mosquitoes takes a blood meal from an infect person who has the parasites in their blood
• Then they feed on an uninfected person
• The parasites are present in the saliva of the mosquito
• Causes of illness
• red blood cells break open and release parasites into the bloodstream
• the person then has symptoms such as chills, fever and headache.
• then the person starts sweating and their body temperature falls
• cycle of symptoms repeats every 48 to 72 hours, following the life cycle of the parasites
• each cycle worsens the person's anaemia or lack of red blood cells
• less and less oxygen reaches the brain and other organs
• so the symptoms are:
• fever, anaemia, headaches, shivering, sweating, nausea

Distribution

• Fighting malaria
• best method of prevention is to get rid of the mosquitoes
• either use insecticides or get rid of breeding grounds
• some success with this method - malaria eliminated from some parts of the world
• Difficulties
• Mosquito - can become resistant to insecticides and chemicals used to contorl
• they breed very quickly
• breeds in the smallest bodies of water
• especially in rainy seasons of tropics
• difficult to drain water to prevent egg laying
• increasing areas with global climate change
• Plasmodium
• drugs are used to fight it but they can also ecome resistance to drugs
• people do not take the drugs for a long period of time so it comes back
• different strains (4 specials)
• different stages to life cycle
• complex organism so difficult to target drugs
• inside the RBC and liver cells - hard to get them as they are inside delicate cells
• No vaccine

AS Biology F212: Disease

Health is a state of mental, physical and social wellbeing - NOT just absence of diesease.
If one is in good health they are:

• able to carry out normal mental and physical tasks
• well fed with a balanced diet
• usually happy with a positive outlook
• suitably housed with proper sanitation
• well integrated into society
• free from diseases

What is disease?

• Disease is a departure from good health caused by malfunction of the mind or body
• symptoms can be physical, mental or social
• those caused by living organisms are called infectious diseases - usually physical 

Parasites and Pathogens

• Parasites
• Live on (external) or in (internal) another living thing (host)
• they cause harm to the host by taking nutrients
• they may live all or part of their life on the host
• they can overburden the host and make it more susceptible to secondary infections
• Pathogens
• this is an organism that causes disease
• they live by taking nutrition from their host and cause damage in the process
• includes a wife range of bacteria, fungi, protoctist and viruses

• Bacteria - cholera
• caused by bacterium Vibrio cholerae
• it is a water-borne disease and spreads through contaminated water, food or shell fish
• they act on the walls of the small intestine causing diarrhoea, dehydration and weakness.
• Tuberculosis
• aka TB is an infectious disease that can affect any part of the body although it is usually found n the lungs as these are the first site of infection
• it kills approx 2 million people each year - more than any other infectious disease
• tuberculosis is caued by one of two species of rod shaped bacteria
• Mycobacterium tuberculosis
• Mycobacterium bovis
• Fungi - Athletes foot and ringworm
• Caused by Tinea fungus
• many different species that causes these diseases
• they live in the skin
• cause redness and severe irritation
• Viruses - TMV and HIV
• TMV - tobacco mosaic virus - affects plants
• HIV - human immunodeficiency virus - affects humans 
• also more common diseases such as colds and flu.
• take over the cells genetic machinery and organelles to allow it to reproduce
• Protosctist
• Amoeboid dysentery 
• Malaria
• enter cells and feed on the contents as they grow

TRANSMISSION OF DISEASE

For a micro-organism to be considered a pathogen they must

• travel from one host to another
• gain entry to the host's tissues
• reproduce
• resist the defences of the host
• cause damage to the host's tissues

Forms of transmission

• by the means of a vector (carrier)
• by physical contact
• by droplet infection

• Malaria
• caused by eukaryotic Plasmodium
• Plasmodium falciparum is the most common
• spreads by the female Anopheles mosquito
• these feed on blood
• the parasite lives in the red blood cells and feed on the haemoglobin
• HIV/AIDs
• The HIV virus enters the body and may remain inactive
• This is known as being HIV positive
• once active, the virus attacks and destroys T helper cells in the immune system
• these cells help to prevent infection
• their destruction reduces the person's ability to resist infection
• EFFECT
• you are unable to defend yourself against any pathogen that enters your body
• these are known as opportunistic infections
• it is the effect of these that eventually kills as person with HIV
• AIDS stands for acquired immune deficiency syndrome
• Transmission
• Exchange of bodily fluids such as blood-to-blood contact
• unprotected sex
• unscreened blood transfusions
• use of unsterislised surical equipment
• sharing hypodermic needles
• accidents such as 'needle-stick'
• across the placenta or during childbirth
• from mother to baby during breast feeding
• Tuberculosis (TB)
• TB is an infectious disease that can affect any part of the body although it is usually found in the lungs as these are the first site of infection
• Pulmonary tuberculosis is spread through the air by droplets containing the bacteria, released into the air when infected individuals cough, sneeze or even talk.
• normally takes close contact with an infected person over a period of time rather than a causal meeting in the street to transmit the bacteria
• Symptoms (droplet infection)
• the symptoms of pulmonary tuberculosis initially include a persistent cough, tiredness, and loss of appetite that leads to weight loss.
• As the disease develops, fever and coughing up of blood may occur
• Risks
• some groups are at greater risks of contracting TB than others.
• people who are in close contact with infected individuals over long period e.g. living and sleeping in overcrowded conditions
• work or reside in long term care facilities where relatively large numbers of people live close together e.g. old people's home, care homes, hospital or prisons
• people from countries where TB is common
• have reduced immunity such as
• the very young or very old
• those with AIDS
• people with other medical conditions that make the body less able to resist disease e.g. diabetes, or lung disease such as silicosis
• those undergoing treatment wit immunosuppressant drugs eg. following a transplant surgery
• the malnourished
• alcoholics or injecting drug-users
• the homeless

The World Health Organisation (WHO)

• WHO states that good health is a human riht
• poor health causes a lot of suffering
• Ill health has an economic cost as a result of medical provision and loss of productivity
• worldwide, many peopl have no access to the basic requirements for good health
• contributing factors
• poverty
• lack of proper shelter
• lack of purified water
• poor nutrition
• poor hygiene
• lack of government investment
• poor/inadequate education on disease, it causes and transmission
• civil unrest or warfare

• Malaria
• kills around 3 million people peryear
• about 300 million are affected worldwide
• it is limited to were the vector (Anopheles mosquito) can survive
• 90% of sufferers live in sub-Saharan Africa
• It is difficult to control
• mosquito
• resistant to insecticides/pesticides/chemicals used for control
• build up in food chains/kill predators
• breeds quickly/very common/lays many eggs
• breeds in small bodies of water/inaccessible places
• especially in rainy seasons
• difficult drain/spray/cover
• difficult to encourage everyone to use netswide range of increasing because of climate change
• rests and hides in houses
• Plasmodium
• side effects of (e.g. anti-malarial) drugs/people don't take drugs long enough (think they are well but not)
• many strains and species
• resistant to drugs
• inside red blood cells or liver cells
• antigen concealment
• dormant/in body for a long time/symptomless carriers/long incubation
• different stages in life cycle in the body
• no vaccine/difficult to develop vaccine
• people lose immunity if malaria is eradicated
• HIV/AIDS
• Spreading in pandemic proportions (is an epidemic of infectious disease that is spreading through human populations across a large region)
• 45 million people living with HIV/AIDS at the end of 2005 (>half in sub-Saharan Africa)
• 5 million newly infected each year
• at the end of 2006 30 million died as result of HIV/AIDS related disease
• Epidemiology
• = patterns in the occurrence of the disease in the human population 
• it identifies the cause of a disease
• the risk factors associated with the disease
• determines the incidence of a disease
• determines the prevalence of the disease as well as the mortality and morbidity
• study how quickly it's spreading
• identify countries/part of population at risk
• identify a disease as endemic, epidemic or pandemic
• ENDEMIC: always present in a population
• EPIDEMIC: spreading rapidly to a lot of people over a large area
• PANDEMIC: a worldwide epidemic
• they target education programmes at people at most risks
• target advertisements to raise the awareness
• target screening programmes to identify individuals at risk
• provide specialist healthcare in certain areas
• provide vaccination programme for the major disease
• targeting research to find cures for the major disease

AS Biology F212: Balance Diet

Carbohydrates - main source of energy
Proteins - essential for growth and repair of body tissues
Fats - source of energy, insulation, etc.
Vitamins - play important roles in chemical processes inside cells. Water soluble or Fat soluble.
Minerals - inorganic elements, essential for normal functioning of the body
Water - transports substances around the body
Fibre - indigestible part f food needed for healthy digestive system

Correct proportion of the three macro nutrients - those needed in large amounts

• 57% carbohydrates
• 30% fats
• 13% protein

Different people need different amounts of food depending on their, age, level of activity and state of health e.g. pregnancy

Malnutrition: unbalance diet - having too much is as bad as not having enough.

Biggest form of malnutrition is obesity.

Body Mass Index over 30 is classified as obese and a condition where excessive fat deposits impairs health.

Obesity can lead to:

• Cancer
• Type 2 diabetes
• Coronary heart disease 

It is linked to: Gall stones, osteoarthritis, high blood pressure

Diet and Coronary heart disease

• CHD  = coronary heart disease
• a result of atherosclerosis = deposition of fatty substances in walls of coronary arteries
• narrows size of lumen
• restricts blood flow to cardiac muscle
• oxygen starvation
• Diet related risk factors
• unbalanced diet
• diet high in saturated fat (animal fat)
• high salt intake
• low fibre/fruit/vegetables
• obesity
• heavy alcohol consumption
• Salt
• Excess salt decease water potential
• more water in blood stream 
• increase blood pressure
• hypertension
• damages inner lining of arteries  first stage of atherosclerosis 
• Lipids
• Animal fats = saturated fats - more harmful
• Plant oils = unsaturated fats
• Polyunsaturated fats are beneficial to health e.g. olive oil
• Cholesterol
• found in cell membrane and skin
• use to make
• steroid sex hormones
• bile
• not soluble in water
• cholesterol is transport in the blood in form of lipoproteins
• Lipoproteins are made in the liver to transport cholesterol
• Low density lipoproteins - LDL
• Deliver cholesterol to tissue (tissues cells have receptor sites on cell surface membranes)
• atherosclerosis
• >3mmol dm^-3  is dangerous
• High density lipoproteins - HDL
• Removes cholesterol from tissues to liver (liver cells have receptor sites on cell surface membraneto which HDL's bind)
• reduces atherosclerosis
• <1mmol dm^-3 is dangerous
• Saturated fats decreases activity of LDL receptors
• less LDLs removed from blood
• deposited in artery walls = atherosclerosis
• Polyunsaturated fats increases activity of LDL receptors
• decreases concentration of LDLs in blood
• Mono aturated fats removes LDLs from blood
• Prevention of CHD through diet
• low in saturated fats
• high in polyunsaturated fats and monosaturated fats e.g. oily fish
• 
  

AS Biology F212: DNA and RNA

DNA

The DNA needs to be stable and must be replicated accurately so daughter cells have the same genetic makeup.

When a cell divides into two,, the chromosomes have to replicate so hat each other the new cells still contains the original number of chromosome, e.g. 46 chromosomes in humans.

Because each chromosome consists of DNA, the DNA molecule has to REPLICATE. The parent cell produces a set of chromosomes identical to its own set. DNA replicates semi-conservatively.

Semi-conservative replication:

• Each parent strand acts as a template for a new strand
• Each new DNA double helix would then have one parent strand and one new strand 

Stages of DNA replication

• The whole  of the DNA molecule uncoils
• The DNA molecule unzips as the hydrogen bonds between the organic bases break
• The bases are now exposed
• In the nucleus individual DNA nucleotides are activated
• The bases of the free activated DNA nucleotides pair up with the complementary exposed bases on each original DNA strands
• The process of complementary base pairing ensures that C-G, A-T
• Covalent bonds form between the phosphate of one of the nucleotide and the sugar of the next to seal the sugar-phosphate backbone
• The whole process is controlled by the enzyme DNA POLYMERASE
• this continues all along the length of the DNA molecule until two DNA molecules are produced
• Both original strands are copied to give 1 old and 1 new strand.
• Two identical copies f the DNA are produced by the semi conservative method of replication

RNA

• RNA is found in three forms, (mRNA, rRNA, tRNA)

Difference between RNA and DNA

• (RNA
• DNA)

• RNA - found in the nucleus and cytoplasm
• DNA- found in the nucleus (small amounts in mitochondria and chloroplasts)
• Contains bases A, C, G, U
• Contains bases, A, C, G, T
• RNA molecule consists of a single strands
• DNA molecule consists of two strands running in opposite directions, twisted together to form a double helix
• Contains the pentose sugar ribose
• Contains the pentose sugar deoxyribose.

How DNA and RNA works together to produce a protein

The sequence of bases on DNA codes for particular polypeptide/protein molecules.

TRANSCRIPTION

• Part of the DNA uncoils and unzips 
• The hydrogen bonds break between the complementary base pairs
• The bases are exposed
• Only 1 of the DNA strand is used
• The particular sequence of bases for that gene form the template
• RNA nucleotide align next to the DNA template strand
• They join up individually using complementary base pairing, A with U, C with G
• A strand of mRNA is made when the backbone for the nucleotides are joined together
• DNA zips back up

AS Biology F212: Nucleic Acids

• DNA is a polynucleotide
• usually double stranded
• made up of nucleotides containing bases adenine, thymine, guanine and cytosine
• DNA is found mainly in the nucleus of cells in chromosomes association with histones.
• Small amounts are found in the mitochondria and chloroplasts
• DNA is built up of units called nucleotides
• a nucleotide is made of three parts:
• a pentose sugar (deoxyribose) (RNA sugar is ribose)
• a nitrogenous base (A, T, C, G)
• a phosphate group

• RNA is a polynucleotide
• usually single stranded
• made up of nucleotides containing the bases adenine, uracil, guanine and cytosine

• RNA molecules exist in three thorms
• messengerRNA (mRNA) - made as a strand complementary to one strand f a DNA molecule
• ribosomalRNA (rRNA) - is found in the ribosomes
• transferRNA (tRNA) - carries amino acids to the ribosomes to form polypeptides.

• Nucleotides are join together by condensation reactions to form a polynucleotide
• they are joined when a covalent bond forms between carbon-3 of the sugar in one nucleotide and phosphate group of the next nucleotide aka PHOSPHODIESTER LINKS
• Too much nucleic acidcauses gout
• uric acid is produces when excess purines are broke down in the liver
• it is excreted in the urine
• some people have too much in their blood
• as it is insoluble at low temperature, crystal form in the joints at extremities e.g. toes
• the toes become swollen and painful - gout

DNA

Structure

• A DNA molecule consists of two polynucleotide strands in the form of a double helix
• two stands of the double helix are held together by hydrogen bonds between the bases on adjacent nucleotides
• there is a specific base pairing A-T, C-G (A-U in RNA)
• 2 H bonds joins A=T and three H bonds joins CºG
• hydrogen bonds are easy to break and make
• In order for the base pairs to form, the polynucleotides has to run in opposite directions, the two polynucleotides strands are described as 'antiparallel'

• GENOME - The genome of an organism is the entire DNA sequence of that organism
• The human genome consists of about 3 billion nucleotide pairs

• DNA replication takes place during interphase
• it creates identical sister chromatids
• this process by which it is carried out is called semi-conservative replication
• Function of DNA
• The double helix gives the molecule stability
• weak hydrogen bonds allow easy unzipping for copying information
• complementary base pairings mean that information can be accurately copied
• the information is in the form of codes to build proteins
• the molecule is long, a large amount of information can be stores
• Each gene is part of a DNA molecule
• a gene is a sequence of DNA bases that determines a polypeptde and a polypeptide is a sequence of amino acids
• the coded information is in the form of a specific sequence of bases aloong the DNA molecule

PROTEIN SYNTHESIS

• takes place in two steps
• transcription
• translation

AS Biology F212: Enzymes

Enzymes are proteins

• These are catalysts of biochemical reactions and speeds up these reactions so they occur at normal body conditions.
• All enzymes are globular proteins, therefore they are soluble.
• The molecule on which the enzyme acts is called the substrate.

Properties of enzymes

• They act as a catalyst
  They speed up a chemical reaction without being used up themselves
• They are high specific
  In general, one enzyme will only catalyse one particular reaction/substrate
• Enzymes are effective in small amounts
• The enzymes do not alter the nature of the products

Active site

• The active site is an area on the surface of the protein where the reaction occurs
• it has a very specific shape that is complementary to that of a substrate

Mechanism of enzyme action

• The enzyme and substrate combine to form a complex (the enzyme-substrate complex)
• The complex then break down to give products and release the enzyme for further use

Enzyme actions

Chemical reactions

• Particles in gases and solutions continually move about and will collide with each other.
• During a chemical reaction two reactants collide and combine to form an intermediate activated complex or transition state, which breaks down to form products.
• In all reactions a certain amount of energy is needed for the reactants to form the transition state
• This energy is known as the activation energy and without it chemical reactions cannot proceed
• The energy comes from maltose which can be boiled in acid - this provides the right conditions for maltose molecule to collide with water molecules energetically enough to hydrolyse

Activation energy

• Before a reaction can occur it must overcome an energy barrier by exceeding its activation energy
• Enzymes work by lowering this activation energy s that the reaction happens more readily
• Enzymes allow reactions to take place at lower temperatures (found in cells)

Lock & Key 

• This idea would explain why enzymes are specific
• The substrate (key) fits the shape of the enzyme (lock)
• Once the products have been made they no longer fit the active site and are released from the enzyme which can react with another substrate because its active site is available once more

Induced fit

• The lock and key model considers the enzyme to have rigid active site and a reaction would depend on the randomly moving substrate molecule entering the active sight in the right orientations
• This is unlikely to happen
• As the substrate collied with the active site - it changes the shape of the enzyme
• This allows the active site to fit more closely around the substrate
• Te substrate is held by the oppositely charged R-groups of the active site
• This is the enzyme-substrate complex
• The product is different shape to the substrate
• They do not fit the active site and are released
• The enzyme is free to catalyse further reactions

Enzymes and temperature

• Temperature and kinetic energy
• Molecules (liquid or gas) move around continually
• This random movement is due to kinetic energy
• Increasing temperature increase this energy
• This increases the frequency and force at which molecules collide
• Enzymes and kinetic energy
• Increased kinetic energy
• Increased number of collisions between active site and substrate
• Increased successful collisions = more enzyme substrate complexes
• Thus, increased rate of reaction
• Temperature
• Increasing temperature increases the rate of reaction up to the optimum temperature.
• Optimum temperature is the maximum rate of reaction
• After this rate of reactions begin to decrease
• Above the optimum the temperature rate of reaction decreases due to the breaking of the bonds that hold the enzymes tertiary structure in place
• This is caused by vibrations of the bonds
• The more that are broken the greater the chance the active site will change
• if this happens the enzyme wills top working - it can't function
• This irreversible change is called denaturation 
• Different enzymes have different optimum temperatures an therefore become denatured at different teoratures

Enzymes and pH

• pH is the measure of the Hydrogen ions concentration.
• pH7 is neutral, below is acidic and above is basic.
• The greater the concentration of hydrogen ions the more acidic it is.
• H+ are attracted to the negatively charged parts of molecules and repelled by positively charge parts.
• Proteins (enzymes) rely on interactions between positive and negative regions to maintain its 3D tertiary structure 
• The H+ can interfere with the hydrogen and ionic bonds which alters the tertiary structure - this causes a change in the shape of the active site then it will effect the rate of an enzyme controlled reaction
• Optimum pH
• This is the pH at which the rate of reaction is highest.
• Enzymes work in a fairly narrow range of pH.
• At this value the H+ concentration gives the tertiary structure its best shape
• The active site is most complementary to the substrate  
• An enzymes optimum pH will be related to the pH of the environment in which it is found
• e.g. Pepsin is a protein digesting enzymes found in the stomach and has an optimum pH of 2
• Trypsin is found in the small intestines which has a pH of 7

Effects of concentration

• No substrate = no enzyme-substrate complexes thus no reaction
• more substrate = more collisions = higher rate of reaction
• this continues until a maximum rate is reached =Vmax
• At this point all the active sites are occupied at any one point in time
• therefore increasing the substrate concentration has no further effect
• the enzymes concentration is a limiting factor
• Enzyme concentration increased > more active sites > more enzyme substrate complexes ? rate of reaction increases
• BUT, a point will be reached where all substrate molecules are occupying active sites
• the substrate is sad to be a limiting factor
• if the substrate is in excess (concentration is high) then the rate of reaction can increase
• the substrate is no longer a limiting factor

Initial reaction rate

• The highest rate of reaction will be seen when the enzyme and substrate are first mixed
• As tie asses the substrate concentration will decrease and thus the rate of reaction ill decrease
• The frequency of collisions will decrease
• The highest reaction rate is known as the initial rate

Inhibition

• Some substance can prevent or slow down the action of enzymes
• These are called inhibitors
• Inhibition can be competitive or non competitive 
• Competitive
• Have a similar structure to the substrate
• prevents the substrate from entering
• level on inhibition depends on the relative concentration of substrate and inhibitor
• this because the substrate and inhibitor are competing for active sites
• Non-competitive
• These do not compete for the active site
• they attach at the region away from the active site
• this changes the tertiary structure of the enzyme
• this causes the active site shape to change
• the substrate no longer fits
• enzyme substrate complex cannot form
• If there are enough inhibitor molecules present to bind to all the active site then the reaction will stop.
• Increasing the substrate concentration will have no effect
• Reversible and irreversible
• both competitive and non competitive enzymes can be reversible or irreversible
• this depends on the whether the inhibitor unbinds with the enzyme or not
• if it stays bound then it's irreversible inhibiton and the enzyme can no loner be used

Cofactors

• Non-protein substance needed for enzymes to catalyse a reaction
• e.g. coenzymes, prosthetic groups, inorganic ion cofactors. 
• Coenzymes
• small
• organic
• non-protein
• binds to active site
• takes part in the reaction and are changed like the substrate 
• can be recycled and used again
• Vitamin B3
• This helps the body break down carbohydrates and fats releasing energy
• Needed for the eznyme pryuvate dehydrogenase to function properly
• This is an enzyme needed n respiration
• A disease called pellagra results from absent from diet
• diarrhoea, dermatitis, dementia, death
• Prosthetic groups
• this is a coenzyme that is permanent part of an enzyme
• they contribute to the 3D shape and tare therefore vital to the function
• e.g. Carbonic anhydrase as a zinc based group
• Inorganic ion cofactors
• these can increase the reaction rate
• they combine with either the substrate or enzymes
• it makes the formation of enzyme substrate complex easier
• this is due to its affects the charge distribution and sometime shape of the eznyme

Interfering with enzymes

• Cystic fibrosis
• affects on respiratory system
• also blocks the passage of digestive enzymes produces by the pancreas into the gut
• leads to digestive difficulties
• tablets are prescribed containing enzymes packaged in an acid resistant coat
• Ethylene glycol poisoning
• this product is found in antifreeze
• it is not poisonous but when ingested it gets broken down in the liver
• carried out by the enzyme alcohol dehydrogenase
• this produces oxalic acid which is extremely toxic and can lead to death 
• treatment: large doses of ethanol is given which causes severe alcohol intoxication
• the ethanol is a competitive inhibitor of alcohol dehydrogenase
• Snake venom
• mixture of toxins and enzymes
• Phosphodiesterase interferes with the working of the preys heart
• the inhibitor of the enzyme acetyl cholinesterase - involved in nerve transmission = paralysis
• Antibiotics and bacterial resistance
• some bacteria are resistant to antibiotics because of the mutation in their DNA which results in them being able to produce enzymes that inactivate antibiotics
• many produce an enzyme (beta lactamase) that breaks down penicillin
• this resistance can be passed on when they replicate
• HIV treatment
• this is treated with chemicals that inhibit protease enzymes
• this prevents the virus from replicating
• they are often competitive inhibitors

AS Biology F212: Carbohydrates

Functions of Carbohydrates:

• Energy source (for respiration)
• Energy store (starch and glycogen)
• Structure (cellulose)

Elements of: C, H, and O.

Simple sugars

• Simple sugars: monosaccharides
• 3 carbon monosaccharides: triose
• 5 carbon monosaccharides: pentose
• 6 carbon monosaccharides: hexose
• Most common monosaccharides are hexoses: glucose, fructose, galactose
• Glucose C6H12O6

Molecular structure of alpha-glucose and beta-glucose

• Glucose is the building block for larger carbohydrates
• This is achieved by joining glucose molecules together using glycosidic bonds
• the bonds form between the C1 on one molecule and C4 on the other

• Two monosaccharides joined by a glycosidic bond is called a disaccharide. 
• eg. glucose + glucose = maltose
• glucose + galactose = lactose (milk)
• glucose + fructose = sucrose

Reducing sugars

• Benedict's reagent: used to test reducing sugars
• Postive test: blue to orange
• Sucrose
• To make sucrose give a positive test with benedict's reagent:
• Sucrose + HCl -biol-benedict's reagent-> positive test (orange)

Polysaccharides

• Three or more monosaccharides make a polysaccharide
• e,g, amylose (starch)
• Glycogen: 
• In animal cells glucose is stored as glycogen
• glycogen is a polymer or alpha-glucose
• basic structure is like amylose but has extra branches
• Starch
• Starch is stored food in plant
• It is made of a alpha-glucose units
• It consists of: Amylose: long unbranched chains with alpha 1,4 glycosidic bonds
• and Amylopection: branched chains with alpha 1,4 and 1,6 glycosidic bonds
• It can be broken down to glucose which can be respired to release energy
• Energy storage
• Compact: more energy in less space than glucose
• Insoluble: doesnt dissolve and change water potential of cell
• Cellulose:
• polymer of beta glucose
• 1, 4 glycosidic and hydrogen bonds
• about 60-70 cellulose molecules become crosslinked by H bonds to form bundles called microfibrils.
• Structural
• Strong: supports the plant, prevents cells from bursting
• Fully permeable: allows water and solutes to reach the cell membrane

AS Biology F212: Biological molecules:Proteins

Metabolism is the total of all the biochemical reactions taking place in the cell of an organism.

There  are two types of metabolic reactions:

1. Catabolism: breaking down larger molecules into smaller molecules. e.g. digestion.
2. Anabolism: building up smaller molecules into larger ones. e.g. photosynthesis. 

Nutrients

• Carbohydrates, fats, proteins are macronutrients - they are are needed in large quantities.
• Vitamins and minerals are micronutrients - they are needed in small quantities.
• Water Makes up 70% of a cell
• Fibre*

Use of chemical groups in the body

• Carbohydrates
  Energy storage and supply, structure (e.g. cellulose)
• Proteins
  Structure, transport, enzymes, antibodies, hormones
• Lipids
  Membranes, energy supply, thermal insulation, protective layers, electrical insulation in neurones, some hormones
• Vitamin and minerals
  Form part of some larger molecules, takes part in some metabolic reactions, acts as co-enzymes
• Nucleic Acid
  Information molecules, carries instruction for life
• Water
  Takes part in  many reactions, support in plants, solvent for most metabolic reactions, transport

*Fibre is a carbohydrate, it does not provide nutrients nor energy, it adds bulk to the diet making it easier for gut muscles to push food along - lower risks of constipation and intestinal cancer.

Proteins

Amino acids

• Proteins are made up of individual molecules (monomers) called amino acids.
• They are joined to forma longer chain called polypeptide - which can be combined to form a protein.
• Polypeptides and proteins are therefore polymers.
• There are 20 different amino acids.

• All amino acids contains: Carbon, Hydrogen, Oxygen and Nitrogen.
• In addition, some contains sulphur.

Structure

• They have an amino group (NH2) and a carboxyl group (COOH)
• These roups along with a H atom are attached to a central carbon atom called the alpha-carbon.
• The alpha-carbon atom has an R group attached to it.
• This R group is a variable group - it's different in each of the twenty amino acids.

Where do animals get their amino acids?

• Animals need proteins in their diet.
• These are digested to amino acids and used to produce proteins.
• Excess amino acids can not be stored as the amino group makes them toxic and thus it is removed my deamination in the liver.

Where do plants get their amino acids?

• Plants make the amino acids they need
• They use nitrate from the soil to produce amino groups
• These are added to the organic groups made from photosynthesis

Formation of a dipeptide

• Amino cids can link together by forming a peptide bond
• A peptide bond is formed when the carboxyl group of one amino acid combines with the amino group of another with the elimination of H2O
• this is called a condensation reaction
• When two amino acids are joined by a peptide bond they form  dipeptide

Making polypeptides and proteins

• Polypeptides and proteins are synthesised on the ribosomes - protein synthesis.
• This process uses mRNA.
• This puts amino acids together in the right order.
• Different mRNA molecules make different proteins.

Levels of Structures

• Primary structure
  This is the sequence of amino acids in a polypeptide molecule.
  The sequence of amino acids is vital because it determines the ultimate shape of the protein and therefore its function.

• Secondary structure
  This refers to the regular arrangement of the polypeptide chain.
  The alpha-helix is where the polypeptide chain is loosely coiled in a regular spiral.
  The beta-pleated sheet is were the polypeptide chains are more extended than in the alpha helix.
  The C=O and N-H groups from the peptide bond regions are held near to each other so that they for many hydrogen bonds.
  These hold the coils of the alpha-helix and the beta-pleated sheets together and make it a stable structure.

• Tertiary structure
  This is the further folding of the secondary structure which gives it a 3D compact shape.
  It depends on the properties of the variable R-groups in the polypeptide chain.

• R-group bonding
  Disulphide bond - the amino acid, cysteine, contains sulphur. where two cysteines are found close together a covalent bond called disulphide bond forms between chains.
  Ionic bonds - occurs between oppositely charged R groups
  Hydrogen bonds - occur between some R groups - these can be easily broken.
  Hydrophobic/philic interactions - hydrophobic amino acids will be most stable if they are held together with water excluded. Hydrophilic amino acids end to be found on the outside of globular proteins.

• Quaternary structure
  Consists of two or more different polypeptide chains which are held together by bonds between the R groups. 

• Globular proteins
• 3D feature: rolls up to form balls (compact)
• Soluble in water - hydrophilic
• Metabolic
• Examples: Enzymes, plasma proteins, hormones, antibodies
• Fibrous proteins
• Forms fibres (long)
• Insoluble - hydrophobic
• Structural
• Examples: Collagen, keratin

The effect of heat 

• Heat increases kinetic energy in a molecule. - causing molecules to vibrate and breaking some bonds maintaining tertiary structure.
• If enough heat is applied the structure can unravel and the protein can no longer function - denatured.
• Even when cooled it will not take on its original shape/arrangement,

Protein hydrolysis

• Protein breakdown is catalysed by enzymes.
• These enzymes are known as protease enzymes.
• Hormone regulation: hormones need to be broke down so that their effect is not permanent.
• Ageing: skin loses elasticity and becomes wrinkled due to inability to rebuild the protein collagen.

• Collagen
• Fibrous protein
• 3 polypeptide chains
• Twisted triple helix
• polypeptides held together by hydrogen bonds between chains
• this forms a collagen fibril
• many fibrils forms a fibre
• Haemoglobin
• 4 polypeptide chains, 2 alpha and 2 beta
• Each one also has an iron prosthetic group attached
• Globular therefore soluble