6 — transport in humans

Question 1

Measures to prevent Tissue Rejection

Answer 1

• the immune system may recognise a donated organ or blood as foreign tissue and cause tissue rejection.
• Tissue matching avoids tissue rejection -> Donor and recipient should be genetically close
• The use of immunosuppressive drugs that inhibit the immune system to reduce risk of tissue rejection (side effect: lowered resistance to infections

Question 2

Blood clotting (coagulation) [4]

Answer 2

Damaged tissues, blood vessels and platelets release thrombokinase. [1]
Thrombokinase catalyse and converts prothrombin in blood plasma to thrombin in the presence of calcium ions. [1]
Thrombin catalyses and converts soluble fibrinogen to insoluble fibrin threads to [1]
entangle red blood cells and blood platelets to form a scab or a clot to seal the wound, thus preventing foreign pathogens and microorganisms from entering the wound causing infections / disease. [1]

functions of blood clotting [2]:
To prevent excessive/further loss of blood/ reduce blood loss; [1]
Seals the wound to prevent entry of microorganisms/ pathogens into the blood/body; [1]

Question 3

Plasma appearance + function

Answer 3

• Contains mainly water (90% of plasma volume)
• Yellowish liquid in blood
• consists of 55% of blood

Function
Transports dissolved substances in blood such as
- excretory products to excretory organs for removal (e.g. urea, creatinine, uric acid)
- Nutrients from SI such as glucose, amino acids, fats
- Blood cells around the body
- Hormones from endocrine glands to target organs

Question 4

Red blood cells adaptations + functions

Answer 4

Adaptations
- Contains haemoglobin that can combine reversibly with oxygen to form oxyhaemoglobin to release O2 to tissue cells
- Has circular biconcave shape to ^SA:V -> ^diffusion of O2 rate into + out of cell
- Absence of nucleus to max space available for haemogoblin
- Flexible and can change into a bell-shaped structure so that they can flow easily through narrow capillaries. Slows down due to tumbling action hence more time for absorption or release of oxygen.

Function
Transport oxygen from the lungs to other parts of the body

Question 5

White blood cells structure + function

Answer 5

Phagocytes:
- carry out phagocytosis to engulf and ingest foreign particles such as bacteria
Phagocytosis is the process by which a white blood cell engulfs and ingests foreign particles such as bacteria.

Lymphocytes:
produce antibodies that:
- cause pathogens to agglutinate (clump together) for easy engulfing and ingestion by phagocytes
- neutralise toxins produced by bacteria (antitoxin function)

Question 6

Platelets structure + function

Answer 6

Structure:
Fragments of cytoplasm. They contain an enzyme that catalyses the conversion of fibrinogen to fibrin threads.

Function:
Promotes blood clotting (coagulation) to prevent excessive blood loss n entry of harmful organisms into bloodstream

Question 7

Explain why heart rate increases during exercise. [3]

Answer 7

1. Vigorous contraction of muscles require increasing energy demand. [1]
2. More blood transported to muscles to supply more oxygen and glucose [1]
3. for aerobic respiration to release more energy to meet energy demand [1]

Question 8

Antigens definition (blood + pathogen)

Answer 8

Identifiable surface features on pathogens that WBCs learn to recognise

Blood:
special proteins found on surface of RBCs

Question 9

Why is blood type O the universal donor

Answer 9

Blood type O is the universal donor: no antigens on the donor’s red blood cells -> antibodies in recipient’s blood plasma will not react with the red blood cells.

Question 10

Why is blood type AB the universal acceptor

Answer 10

Blood type AB is the universal acceptor -> no blood type antibodies in the blood plasma -> no agglutination of red blood cells in donor’s blood will occur.

Question 11

Explain why it is impossible for a person of blood type A to receive B type blood during blood transfusion. [3]

Answer 11

• Blood type A has A antigen on the surface of the RBC, thus the blood plasma contain B antibodies [1].
• Blood type B has B antigen on the surface of the RBC, upon transfusion, the B antibodies in plasma will bind with the transfused B antigen RBCs and cause agglutination. [1].
• Agglutination of RBCs will cause blockage in blood vessels resulting in heart attack / stroke / organ failure. [1]

Question 12

Adaptations and functions of arteries

Answer 12

Functions: Transports oxygenated blood (except pulmonary arteries) from the heart to other parts of the body

1. Walls r thick muscular and elastic to withstand the high blood pressure flowing within
2. recoil and stretching of the elastic artery wall helps maintain the pressure of the blood and push blood forward as it travels further away from heart.

Question 13

Adaptations and function of blood capillaries

Answer 13

Functions: To facilitate exchange of substances between blood and tissue cells in the body

1. One-cell thick endothelium, – minimize diffusion distance for faster rate of exchange of substances via diffusion.
2. Partially permeable endothelium that allows only smaller molecules to pass thru n not the larger ones
3. Numerous branches of capillaries ->
   ^surface area for exchange of substances betw blood n tissue cells, ^total cross-sectional area of the blood vessels, lowering the blood pressure and thereby slowing blood flow to give more time for exchange of substances
4. Narrow lumen, lowering the blood pressure and thereby slowing blood flow to give more time for exchange of substances via diffusion
5. Continuous blood flow thru capillaries: maintain steep conc gradient for ^rate of exchange of substances
6. They have very large total cross-sectional SA, lowering blood pressure and slowing blood down to increase time for diffusion to occur.

Question 14

Adaptations of and functions of veins

Answer 14

Functions: Transport deoxygenated blood (except pulmonary veins) back to the heart.

Blood in vein has lower pressure and speed, thus blood tends to backflow -> have valves to prevent backflow of blood.

In the veins, blood lower in pressure n spd compared to in the arteries -> walls of veins are relatively thinner and LESS ELASTIC compared to the walls of the arteries.

Question 15

Tissue fluid

Answer 15

Colourless liquid present in tiny spaces betw tissue cells that transports dissolved substances betw tissue cells n the blood capillaries.

Question 16

Compare and contrast between the structures of artery and vein. [4] (2S2D)

Answer 16

Similarities:
- Muscular and elastic tissue present [1]
- One cell thick endothelium present [1]

Differences:
- Vein has wider lumen but artery has narrower lumen [1]
- Vein has valves but artery don’t have valves [1]
- Vein has thinner, less muscular tissue but arteries have thicker muscular tissue [1]
- Vein has less elastic tissue but arteries have more elastic tissue [1]

Question 17

Describe how a molecule of oxygen is transported from the alveoli to the heart muscles. [6] + O2 from lungs to kidneys [4] + blood from right ventricle to kidneys [4]

Answer 17

1. Molecule of oxygen dissolves in the layer of moisture on the surface of the alveolus and diffuse from alveoli through the alveolar wall into blood capillaries down the concentration gradient. [1]
2. Binds with haemoglobin in the red blood cells to form oxyhaemoglobin and transported in the blood capillaries. [1]
3. Oxygenated blood from the blood capillaries surrounding the lungs enters the left atrium and left ventricle through the pulmonary veins via passive filling. [1]
4. Atrial systole, muscles in left atrium contracts forcing more oxygenated blood into left ventricle. [1]
5. Ventricular systole, muscles in left ventricle contracts and pressure in the ventricle becomes higher than in the aorta, forcing open the semi-lunar valve and forces oxygenated blood into the aorta. [1]
6. The oxygenated blood flows into coronary artery to supply the heart muscles with oxygen. [1]

A. Oxygenated blood from the lungs enters the left atrium of the heart via the pulmonary veins.
B. Pressure in the left ventricle is lower than the pressure in the left atrium, forcing the bicuspid valve to open. [1]
C. Muscles of the left atrium contracts, forcing blood from the left atrium into the left ventricle through the bicuspid valve. [1]
D. Muscles of the left ventricle contract and pressure in the left ventricle rises above the left atrium and forces the bicuspid valve to close to prevent backflow of blood from the left ventricle back to the left atrium. [1]
E. Pressure in left ventricle continues to rise and becomes higher than the aorta, forcing the semi-lunar valve open and oxygenated blood is forced out of the heart into the aorta and transported to the kidneys via renal arteries. [1]

[4]:
Blood is pumped from right ventricle to lungs via the pulmonary artery. [1]
Blood flows from lungs back to the heart via the pulmonary vein into the left atrium. [1]
From the heart, blood is forced out of left ventricle through the aorta.
Blood then flows into the kidneys through the renal artery that branches off from the aorta. [1]
In the kidneys, the renal artery branches into smaller arterioles. The arterioles branch into blood capillaries. [1]

Question 18

Explain how the presence of valves would help in maintaining one directional flow of blood in the heart. [6]

Answer 18

1. The flow is always from the atrium to the ventricle and then out of the heart via the aorta / pulmonary artery. [1]
2. During passive filling, both atrium and ventricle undergo diastole, bicuspid and tricuspid valve are open to allow blood to flow from atria into ventricles. [1]
3. During atrial systole, muscles in atria contracts and pressure increases, bicuspid and tricuspid valve are still open to allow more blood to flow from atria into ventricles. [1]
4. During ventricular systole, the bicuspid and tricuspid valve close to prevent the backflow of blood into the atria when the pressure in the ventricle is higher than that of the atria [1]
5. When the pressure of the ventricle is higher than that of the aorta / pulmonary artery, semi-lunar valve is forced open and blood is forced from ventricles into the aorta / pulmonary artery [1]
6. During ventricular diastole, the semi-lunar valve close to prevent backflow of blood back into ventricle as the pressure in ventricle drops below the pressure of aorta / pulmonary artery [1]
7. When pressure in ventricle drop below the pressure of atria, bicuspid / tricuspid valve open again to allow passive filling taking place for the next cycle. [1]

Question 19

What happens if u hv a hole in median septum

Answer 19

• Hole present in median septum thus blood flow thru hole mostly from LS to RS of heart since pressure in LS > RS, resulting in mixing of oxygenated n deoxygenated blood -> lesser O2 for transportation to body cells for aerobic respiration to release lesser energy for cellular activities.
• Patients may suffer from shortness of breath+ fatigue +/ heart failure

Question 20

Median septum

Answer 20

Muscular wall that separates right n left sides of heart.

Median septum prevents mixing of deoxygenated blood in right side with oxygenated blood in left side to avoid reducing amt of O2 available to be carried to the rest of the body.

Question 21

Tricuspid valve vs bicuspid valve

Answer 21

TV:
- Prevents backflow of blood from RV to RA
- consists of 3 flaps that point downwards into the ventricle n attached to the walls of RV by chordae tendinae (chord-like tendons)

BV:
- Prevents backflow of blood from LV to LA
- Bicuspid valve has 2 flaps that point downwards into LV. Chordae tendinae prevent the flaps from being reverted into the atrium when the LV muscles contract.

Question 22

Cardiac cycle definition

Answer 22

Refers to the sequence of events that takes place in 1 heartbeat.

Question 23

Blood pressure definition

Answer 23

the force that blood exerts on the walls of blood vessels.

Cause: Contraction of the muscles of the left ventricle of the heart. [1]

Question 24

Cardiac cycle graph

Answer 24

1. Atrial systole + AVV opened: Atrial muscles contract, pressure^ in atria, forcing blood into ventricles.
2. Ventricular systole, AVV & SLV closed + lub sound: Ventricular muscles contract, pressure in ventricles rise above pressure in atria -> bicuspid n tricuspid valve closes to prevent backflow of blood into atria -> ‘Lub’ sound produced.
3. All valves still closed. No change in blood volume, blood continues to rise.
4. SLV open, blood leaves + passive filling: Pressure in ventricle rises higher than in aorta & PA. Semi-lunar valves open. Blood flows from RV n LV to pulmonary artery n aorta respectively. Passive filling occurs, RA n LA receives blood from VC n pulmonary veins respectively.
5. Ventricular diastole + SLV closed + dub sound: Ventricular diastole occurs, pressure in ventricles falls below that of arteries -> semi-lunar valves close to prevent backflow of blood from PA & A into ventricles -> ‘dub’ sound produced
6. All valves closed. No change in vol of blood
7. AVV open: Bicuspid n tricuspid valve opens when pressure in ventricle is lower than that in atrium.
8. Pressure in ventricle rises as blood continues to enter ventricle from atrium. Whole cycle repeats

[3]:

At the start of the cardiac cycle, the tricuspid valve (Z) is open and blood is passively filling the right ventricle (Y). [1]
Atrial systole occurs next. Muscles of the right atrium contract, blood pressure in the atrium increases and blood is pumped/ force into the right ventricle. The tricuspid valve remains open.[1]
Ventricular systole occurs after atrial systole. Muscles of the right ventricle contract, blood pressure in the right ventricle increases and becomes higher than blood pressure in the right atrium. [1]
The tricuspid valve is forced closed (‘lub’ sound) to prevent backflow of blood from right ventricle into the right atrium. [1]

Question 25

Coronary heart disease — definition + causes + types + risk factors + prevention

Answer 25

Definition:
A condition where the coronary arteries become narrowed or blocked and this reduces the blood supply of oxygen and nutrients such as glucose to heart muscles.

Cause
- Deposits of fatty substances such as cholesterol n saturated fats) on inner surface of coronary arteries (atherosclerosis) -> lumen of arteries narrowed n ^BP ->Blood clot forms in artery -> devs rough inner surface -> Reduced blood flow to heart -> Heart muscle cells receive reduced oxygen for aerobic respiration and glucose supply -> May lead to a heart muscle cell death and heart attack

Explain how coronary atherosclerosis leads to heart diseases. [3]
With coronary atherosclerosis, there will be reduced / no oxygen and glucose transported to the heart/cardiac muscle cells. [1]
Reduced / no aerobic respiration to release energy. [1]
Result in heart attack + cells die. [1]

Types:
- Atherosclerosis: disease where fatty deposits accumulate on inner walls of arteries, narrowing lumen
- Coronary artery: an artery that branches out of the aorta, sending O2 n nutrients to the heart muscles
- Coronary artery disease: when atherosclerosis occurs in a coronary artery

Risk factors:
- Smoking
- Unhealthy diet
- Genetic factors
- Age
- Sedentary lifestyle

Prevention:
- Healthy diet
- Avoid smoking
- Regular physical exercise

Question 26

Coronary artery

Answer 26

an artery that branches out of the aorta, To transport oxygenated blood containing glucose [1] from the aorta to the cardiac/ heart muscle cells for respiration to release energy. [1]

Question 27

Heart attack

Answer 27

• Blood supply to the heart muscles can be greatly reduced due to the blockage of the coronary arteries by accumulation of fatty deposits on the inner wall.
• Blood flow to particular part of heart blocked -> receives insufficient O2 n nutrients -> region of heart muscle dies -> fatal as heart X pump blood to various parts of body

Question 28

Describe movements of substances between capillaries and cells. [3]

Answer 28

Capillaries bring nutrients and O2, which diffuse from the blood plasma to the tissue fluid and into cells. Waste products and CO2 diffuse out of the cells into the tissue fluid, then into the blood plasma of capillaries,

Question 29

Explain how the blood functions to protect the body against infections.
[3]

Answer 29

Lymphocytes produce antibodies [1] to agglutinate pathogens [1] and
neutralise toxins [1] and the phagocytes engulf and ingest pathogens by phagocytosis. [1]

Question 30

Smoking tobacco can cause the occlusion of the coronary arteries. Suggest effects of occluding of arteries. [3]

Answer 30

Coronary arteries r responsible for transporting oxygenated blood from the aorta to the muscles of the heart.
Occlusion of coronary arteries will cause less blood carrying less oxygen and glucose to flow through to the cardiac/ heart muscle cells. [1]
Rate of respiration in heart muscle cells will be lower and less energy is released. [1]
Cardiac/ heart muscle cells will die as a result and the person will get a heart attack. [1]

Question 31

Small arteries have a larger proportion of muscle fibres than large arteries.
Suggest a role for the muscle fibres in small arteries. [2]

Answer 31

Smaller arteries have larger proportion of muscle fibres which contract during vasoconstriction and relax during vasodilation
[1] to bring about regulation of blood pressure, diverting of blood flow and regulating of blood temperature for homeostatic control. [1]

Question 32

Suggest what causes the fall in blood pressure as the blood passes from aorta to vena cava.

Answer 32

Lumen of vena cava is wider than that of aorta.[1] /Less recoil of walls of vena cava/ loss of pressure due to friction

Question 33

Describe how the breakdown products of excess amino acids are transported in the blood from their site of reduction to their site of removal from the human body. Names of blood vessels r not required.[5]

Answer 33

Excess amino acids are deaminated in the liver cells to produce urea which diffuse from the liver cells into the tissue fluid down the concentration gradient. [1]
The dissolved urea diffuse into the blood capillaries and is transported into the heart by veins and out of the heart via the aorta to the kidneys. [1]
Urea being small molecules are forced out of the blood by high hydrostatic blood pressure during ultrafiltration at the glomerulus across a partially permeable basement membrane into the Bowman’s capsule. [1]
Urea in the glomerular filtrate then flows along the kidney tubules to the collecting duct and into the ureter to the urinary bladder.
[1] and discharged in urine out of the body through the urethra. [1]

Question 34

State 2 visible changes in the alveoli of a long-term smoker and explain how the changes can affect the health of a person. [6]

Answer 34

The alveolar walls in the smoker are broken down/ has holes compared to the healthy individual which is intact. [1]
The number of alveoli are fewer in the smoker than the healthy individual/ The size of alveoli are larger in the smoker than the healthy individual. This results in lesser surface area to volume ratio for the smoker compared to the healthy individual. [1]

Reduced surface area to volume ratio will result in lesser gaseous exchange, with lesser oxygen absorbed into the blood stream. [1]
Lesser oxygen is transported to the tissue cells for aerobic respiration. [1]
Resulting in lower rate of aerobic respiration, lesser energy released [1]

These changes result in emphysema, a condition where decreased SA for gaseous exchange leads to a decrease in amount of oxygen supplied to body cells. Person will suffer from breathing difficulties with wheezing and severe breathlessness [1]
(note: nd mention symptoms of diseases)

Question 35

A patient w lung disease is inactive and consumes too much carbohydrates and fats. Suggest and explain the effect of this behaviour on the patient’s circulatory systems and health. [4]

Answer 35

The person will develop coronary heart disease [1] as fatty substances (cholesterol and fats) are deposited on the inner surface of the coronary arterial walls and narrows the lumen.[1]
This reduces blood flowing to the cardiac tissue/ muscle cells [1] and lesser oxygen and glucose is transported to the cardiac tissue cells for aerobic respiration, resulting in heart attack, increased risk of formation of blood lot within brain arteries, and increased risk of atherosclerosis. [1]

Cardiac tissue/ muscle cells do not receive enough energy and will die, resulting in heart attack. [1]

The person may also develop diabetes mellitus due to high blood glucose as he consumes too much carbohydrates and lesser glucose is used for aerobic respiration due to lesser gaseous
exchange and inactive lifestyle. [1]

Question 36

Describe and explain an advantage of right ventricle having lower pressure than left ventricle [1]

Answer 36

Blood is pumped to the lungs at lower pressure. Blood moves slower past the
alveoli and there is more time for oxygen to diffuse into the blood and carbon
dioxide to diffuse out of the blood. [1]

Question 37

Define atherosclerosis [1]

Answer 37

disease where Fatty substances such as cholesterol and fats [1] are deposited and accumulated on the inner surface of blood vessels and arteries, narrowing lumen. [1]

Question 38

Suggest 1 trigger of heart attack [1]

Answer 38

A blood clot / thrombosis is trapped in a coronary blood vessel affected by
atherosclerosis. [1]

Question 39

Describe the process that generates the pressure in aorta. [1]

Answer 39

Contraction of the muscles of the left ventricle of the heart

Question 40

Describe and explain how blood entering the heart from body organs reach the lungs [4]

Answer 40

Blood enters the right atrium of the heart from the body organs via the vena cava. [1] During ventricular diastole, pressure in the right ventricle is lower than that in the right atrium, forcing the tricuspid valve open, so blood flows from the right atrium into the right ventricle. [1] Muscles of the right atrium contract to force blood into the right ventricle. Muscles of the right ventricle contract during ventricular systole, increasing the pressure in the right ventricle to become higher than that of the right atrium and the tricuspid valve is forced closed to prevent backflow of blood into the right atrium. [1] When the pressure in the right ventricle becomes higher than that of the pulmonary arteries, the semi-lunar valve is forced open and blood is forced out of the right ventricle into the lungs via the pulmonary arteries [1]

Question 41

Describe how toxic components of tobacco smoke that may affect health. [6]

Answer 41

Carbon monoxide [1]:
It binds with haemoglobin irreversibly to form
carboxyhaemoglobin which reduces the oxygen carrying capacity of red blood cells, reducing the amount of oxygen transported around the body. [1] Hence, lesser oxygen is supplied to tissue cells for reduced rate of aerobic respiration to release lesser energy for cellular activities.
It increases the rate of fatty deposits on inner arterial wall and damages lining of blood vessels, increasing the risk of atherosclerosis and blood clotting in arteries. [1]

Tar [1]:
Tar is a carcinogenic chemical which induce uncontrolled cell division of the epithelium, increasing the risk of lung cancer. [1] It paralyzes cilia lining the air passages, hence dust particles and pathogens trapped in the mucus lining the airways cannot be removed. [1]

Nicotine [1]:
It Increase the heartbeat and blood pressure. [1] It also increase the risk of blood clots in blood vessels, reduces blood supply to the heart muscles. [1]/ constriction of blood vessels

Question 42

State one conclusion from this graph and suggest how this is related to drinking and driving [4]

Answer 42

The higher the blood alcohol consumption, the longer the person’s
reaction time. [1] Increasing blood alcohol concentration by 30
mg/100cm3 increases reaction time by 10 milliseconds. [1] Blurred
vision and poor muscular coordination impaired judgement. [1]
Hence drinking alcohol will increase one’s reaction time when
driving; increasing the risk of accidents [1]

Question 43

Describe the pathway of blood from vena cava into pulmonary artery. [4]

Answer 43

Blood enters the right atrium of the heart from the body organs via the vena cava. [1]
During ventricular diastole, pressure in the right ventricle is lower than that in the right atrium, forcing the tricuspid valve open. [1]
Muscles of the right atrium contract to force blood into the right ventricle.
Muscles of the right ventricle contract during ventricular systole, increasing the pressure in the right ventricle to become higher than that of the right atrium and the tricuspid valve is forced closed to prevent backflow of blood into the right atrium. [1]
When the pressure in the right ventricle becomes higher than that of the pulmonary arteries, the semi-lunar valve is forced open and blood is forced out of the right ventricle into the lungs via the pulmonary arteries [1]

Question 44

Using named blood vessels, outline path taken by a molecule of urea before it leaves the body. [4]

Answer 44

Urea molecule leaves the liver via hepatic vein and travels to the heart along inferior vena cava.
From heart, travels to lungs via pulmonary artery
Returns to heart from lungs via pulmonary veins to aorta from heart and into renal artery
To kidney, glomerulus to Bowman’s capsule for excretion.

Question 45

Suggest two possible immune responses to the viral ‘spike’ protein. [2]

Answer 45

Lymphocytes secrete antibodies that cause spike proteins to agglutinate;
Phagocytes carry out phagocytosis to engulf, ingest, digest spike proteins;

Question 46

Describe 2 consequences that may result from the production of sickle-shaped RBCs. [2]

Answer 46

Reduce O2 carrying capacity in RBCs
Clogging blood vessels
Damage blood vessels
RBC more fragile and easily broken
Breathlessness
Fatigue

Question 47

Explain how the drug given to the rats was transported to the heart muscle. [4]

Answer 47

Drug will dissolve in the blood plasma [1]
and transported in veins to the heart [1]
and then to the aorta [1]
and then to the coronary arteries to the heart muscles. [1]

Question 48

Suggest how the medicine in the medicine patch reaches the bloodstream. [2]

Answer 48

Medicine diffuses through the epidermis and dermis of the skin [1]
into the blood capillaries [1] in the skin and into the bloodstream

Question 49

State 2 advantages and 1 disadvantage of giving medicines using a patch rather than taking medicines through the mouth. [3]

Answer 49

Drug delivery is targeted before it is circulated in the bloodstream. [1]
Drug takes a shorter time to reach its site of action. [1]
Not all the medicine in the patch might have been delivered. [1]

Question 50

Define Double circulation + give advantages

Answer 50

Process which the blood passes through the heart twice in one complete circuit

Advantages:
During pulmonary circulation, (from heart to lungs to heart) the right ventricle has thinner walls that pumps deoxygenated blood to the lungs at lower pressure, allowing blood to flow thru lungs at lower spd, allowing sufficient time for blood to be fully oxygenated and CO2 to diffuse out before returning to the heart.

In systemic circulation (from heart to rest of the body back to heart), blood is pumped by the left ventricle which has thick walls, at high pressure, ensuring oxygenated blood and nutrients is quickly distributed to all the tissues in the body

Question 51

Phagocytosis

Answer 51

The process of engulfing and ingesting pathogens by phagocytes

Question 52

Blood clots formed in blood vessel can be carried to the brain by blood, blocking arteries in brain. Suggest how this blockage may affect the brain. [3]

Answer 52

As the arteries in the brain become blocked by the clot, less/ no blood flows to the brain cells and the cells do not receive oxygen and glucose [1] for respiration to release energy for cellular activities. [1] As a result, brain cells die, which may result in a stroke/ brain damage [1]

Question 53

Identify and explain why the chambers of the heart have walls of different thickness. [4]

Answer 53

A and B represent the left and right atria while C represents the right ventricle and D represents the left ventricle; [1]
The walls of the left and right atria are 3 mm thick and are thinner than the ventricles as they only have to pump blood to the left and right ventricles respectively which is a short distance away and does not require high pressure; [1]
The wall of the left ventricle is the thickest at 12 mm as a very high pressure is needed to force/ pump blood out of the heart to all the parts of the body; [1]
While the wall of the right ventricle is 5 mm thick as the right ventricle only pumps blood out of the heart to the lungs, which is a shorter distance away and requires a lower blood pressure than the left ventricle; [1]

Question 54

State one possible cause of occlusion of the coronary arteries. [1]

Answer 54

High fat/ cholesterol diet/ smoking [1]

Question 55

Reasons why each substance is transported in blood plasma [2]

Answer 55

Amino acids: transported to body cells for synthesis of proteins
CO2: transported to the lungs to be excreted during exhalation [1]
WBCs/antibodies: circulate in blood to provide defence against disease