Describe the composition of the blood.
Made up of liquids and solids:
Solid part (45%):
- Red blood cells (contain haemoglobin, which contains iron)
- White blood cells
- Platelets
Liquid part (55%): -Plasma (made up of water, salts and protein)
What does plasma transport?
- Red blood cells
- White blood cells
- Platelets
- Digested food (e.g. glucose & amino acids) - from gut to all body cells
- Carbon dioxide - from body cells to lungs
- Urea - from liver to kidneys
- Hormones
- Heat energy
What are the adaptations of red blood cells which make them suitable for carrying oxygen?
- Biconcave shape (shaped like a flat disc)= large surface area for absorbing and releasing oxygen.
- Absence of nucleus = creates room inside cell for more haemoglobin, so they can carry more oxygen.
- Contain haemoglobin (a red chemical which contains iron) = in the lungs: reacts with oxygen to form oxyhaemoglobin, in body tissues: oxyhaemoglobin breaks down to haemoglobin, releasing oxygen from the red blood cell to the cells.
- Small and flexible = allows them to pass through capillaries (only one cell thick).
What are the structural adaptations of white blood cells which make them suitable for ingesting pathogens?
They have a lobed nucleus and an irregular shape, which enables them to change shape when they are ingesting pathogens by surrounding and engulfing them until they are completely enclosed.
What are phagocytes and what is their function?
Phagocytes are a type of white blood cells that kill pathogens by surrounding and engulfing them until they are completely enclosed and then digesting them by enzymes. Different types of phagocytes target different types of pathogens (e.g. bacteria, fungi and protoctist parasites).
What are antigens?
Antigens are proteins found on the surface of a substance (often a pathogen) that trigger an immune response. Different antibodies attach to different pathogens, so the body’s immune system can recognise foreign antigens (antigens that are not normally produced by the body, but by pathogens instead).
What are lymphocytes and what is their function?
Lymphocytes are a type of a white blood cell which produce chemicals called antibodies. These are molecules which are shaped to fit onto invaders’ antigens. When a pathogen infects the body, lymphocytes produce antibodies specific to that pathogen. Antibodies stick onto foreign microorganisms in the blood, which either kills the microorganisms or causes them to clump together, making it easier for phagocytes to engulf and destroy them.
What are memory cells?
Lymphocytes produce memory cells. These remain in the blood after a pathogen has been destroyed, sometimes for the rest of a person’s life. Memory cells produce a quick response if the antigen is encountered again.
How do vaccinations work?
- Vaccination is a way of preventing disease by making the body respond as if it has already been infected.
- Vaccine prepared from small amounts of material from the pathogen, which is either dead or weakened so that it cannot cause infection.
- Vaccine put into body, through mouth (polio) or by injection.
- Lymphocytes make antibodies specific to pathogen and memory cells (remain in blood after pathogen = destroyed).
- If you are infected by live pathogen in future, memory cells recognise it very rapidly and stimulate lymphocytes to produce antibodies sooner, faster + in greater quantity.
- This kills off pathogen, often before you develop symptoms + realise you have been infected.
- Rapid response makes you immune to pathogen.
What are platelets and what is their function?
Platelets are small fragments of cells; they have no nucleus and are suspended in the blood plasma.
When the wall of a blood vessel is damaged, platelets clump together to ‘plug’ the damaged area. This is known as blood clotting, which prevents blood loss and the entry of microorganisms into the blood from the wound.
Describe the structure of the heart.
- Inside the heart there are four chambers - two on the left and two on the right.
- The chambers on the left hand side are separated from the chambers on the right hand side by a thick section of cardiac muscle called the septum.
- The top two chambers are called the left atrium and the right atrium.
- The bottom two chambers are called the left ventricle and the right ventricle.
How does the heart function?
1) The right atrium of the heart receives deoxygenated blood from the body (through the vena cava).
2) The deoxygenated blood moves through to the right ventricle, which pumps it to the lungs (via the pulmonary artery).
3) The left atrium receives oxygenated blood from the lungs (through the pulmonary veins).
4) The oxygenated blood then moves through to the left ventricle, which pumps it out round the whole body (via the aorta).
Why does the left ventricle have much thicker and more muscular walls than the right ventricle?
The left ventricle has to pump blood around the whole body, whereas the right ventricle only has to pump it to the lungs. This also means that the blood in the left ventricle is under higher pressure than the blood in the right ventricle.
How does the heart rate change during exercise?
Heart rate increases during exercise in order to pump blood more rapidly around the body. This supplies oxygen and glucose more quickly to respiring cells particularly in the muscles, and removes waste products faster.
How does the heart rate change under the influence of adrenaline?
1) When an organism is threatened (e.g. by a predator) the adrenal glands release adrenaline.
2) Adrenaline binds to specific receptors in the heart. This causes the cardiac muscle to contract more frequently and with more force, so heart rate increases and the heart pumps more blood.
3) This increases oxygen supply to the tissues, getting the body ready for action.
What is coronary heart disease?
- Affects the two coronary arteries branching from the aorta to supply all the muscles of the heart in both the atria and the ventricles.
- Caused by accumulation of atheroma (fatty material consisting of cholesterol [a lipid], dead muscle cells and platelets).
- Build up of atheroma forms deposits called plaques in lining of arteries, which cause artery walls to become less elastic.
- Arteries become narrower + restrict blood flow.
- Blood can no longer flow smoothly and is more likely to clot, forming a thrombus.
- Blood clots can interrupt blood flow even more/completely block artery.
- Heart attack occurs when large branch of coronary artery = obstructed by a blood clot, so muscle around it is starved of oxygen + glucose, meaning it can’t respire, so it dies.
Give some factors that can increase the risk of coronary heart disease.
- Sex: Men are more at risk than women; oestrogen provides some protection in women.
- Age: Risk increases with increasing age; about 80% of people who die of coronary heart disease are 65 or over.
- Body mass: Being overweight or obese increases risk; excess weight puts more strain on the heart.
- High blood pressure: Risk increases with increasing blood pressure.
- Diet: Risk increases with a high intake of saturated fat & salt (found in red meat + processed foods); risk decreases with high intake of fruit, vegetables and fibres, & a moderate intake of unsaturated fats (found in fish).
- Exercise: Lack of exercise increases risk; as more aerobic exercise is taken, risk decreases.
What can be done to reduce the chances of getting coronary heart disease?
- Giving up smoking (and drinking)
- Eating less saturated fat
- Losing weight
- Taking regular aerobic exercise (aim for at least 150 minutes of moderate activity e.g. cycling/fast walking every week).
Name the three types of blood vessel.
Arteries, veins, capillaries
Which vein is the exception to the rule that veins carry deoxygenated blood?
Pulmonary vein
Which artery is the exception to the rule that arteries carry oxygenated blood?
Pulmonary artery
Why do veins contain valves?
Valves prevent the backflow of blood to ensure that it only flows in one direction.
Why do arteries not need valves?
The pressure from the heart is so strong that blood is only able to flow in one direction.
What substances go into the bloodstream and come out of the bloodstream at the capillaries in the lungs?
Oxygen goes into the bloodstream and carbon dioxide comes out of the bloodstream at the capillaries in the lungs.
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Section 1: a) Characteristics of living organisms9
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Section 2: h) (Human) Transport36
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Section 2: d) Movement of substances into and out of cells13
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Section 2: c) Biological Molecules39
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Section 4: a) The organism in the environment & b) Feeding relationships58
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Section 1: b) Variety of Living Organisms24
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Section 2: e) (Human) Nutrition60
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Section 3: a) (Plant) Reproduction53
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Section 3: a) (Human) Reproduction34
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Section 2: a) Level of organisation & b) Cell structure49
