Download Core G 1 4 7 8 9 11

G (MAMMALS) QUESTION 4
(a) Background: Figure 4.1 shows the left side of the heart. The bicuspid valves are shut,
meaning atrial systole has happened. Ventricle blood pressure is higher than atrial
blood pressure, hence closing of bicuspid valves.
Answer:
- ventricle contracts or ventricular systole
- blood is forced through the opened semi-lunar valves
- into aorta
- atrio-ventricular valves closed since blood pressure is higher in ventricles
compared to atrium
(b) Background: You need to explain which part of the heart and how this part allows
blood to flow in one direction.
Answer:
- valves close to prevent backflow of blood
- atrial systole forces the bicuspid valves to open
- since there is higher blood pressure in the atrium than in the ventricles
- ventricular systole forces the bicuspid valves to shut
- and the semilunar valves of the aorta to open
- after ventricular systole, semilunar valves are forced shut to prevent backflow
- tendons and papillary muscles contract to ensure that the bicuspid valves do
not open upwards
(c) Background: Explain why blood pressure in the left ventricle falls to zero in the
cardiac cycle. Explain why blood pressure in the arteries only reach a minimum of
10kPa, but not zero.
Answer:
- pressure falls to zero as ventricles pump out all of the blood during ventricle
systole
- pressure only falls to 10kPa in arteries as arteries have elastic fibres so there
will always be pressure in the arteries
- arteries have small diameters that makes them resistant to blood flow, so
there must be some pressure in the arteries to keep the blood flowing
(d) Backgroud: You MUST mention the components in tobacco smoke and what their
roles are in causing cardiovascular diseases.
Answer:
- nicotine causes reduction in arteriole lumen diameter. This increases blood
pressure.
- nicotine stimulates secretion of adrenaline hormone. This increases heart rate.
- nicotine reduces blood flow to extremities of body. This reduces oxygen
supply.
- nicotine increases “sticky-ness” of blood platelets. This increases chances of
blood clotting and forming thrombus.
- carbon monoxide reduces oxygen transport by forming carboxyhaemoglobin.
- nicotine and carbon monoxide both damages the artery linings
G (MAMMALS) QUESTION 1
(a) Background: Talk about the structure of haemoglobin. Relate structure that enables it
to take up oxygen in the lungs.
Answer:
- four polypeptide chains
- outwardly pointing hydrophilic R-groups maintain solubility (to allow
haemoglobin to be soluble in red blood cells)
- each polypeptide has one haem group
- iron ion forms part of te haem group
- each iron ion can temporarily attach to one oxygen molecule (NOT oxygen
binds to haem)
- with four haem groups, four oxygen molecules can be carried by a
haemoglobin molecule
- to form oxyhaemoglobin
(b) Background: Read off values from graph given.
Answer:
- 12-14
- 5
- 20
(c) Background: Explain how in the presence of carbon dioxide, haemoglobin will
release the oxygen molecule(s) it is carrying.
Answer:
- carbon dioxide reacts with water to form carbonic acid
- this reaction is catalysed by carbonic anhydrase enzyme
- carbonic acid dissociates into hydrogen carbonate and hydrogen ions
- hydrogen ions combine with haemoglobin
- to form haemoglobinic acid
- this stimulates release of oxygen from haemoglobin
G (MAMMALS) QUESTION 8
(a) Background: Important to know the parts of your heart (for your exams, at least).
Answer:
- P: right atrium (important to put in the word ‘right’)
- Q: aorta
(b) Background: Chamber S is left ventricle. Chamber R is left atrium. Explain why left
ventricle has a much thicker wall than the left atrium.
Answer:
- more muscle fibres in left ventricle wall
- left ventricle needs to pump blood to all parts of the body (except lungs)
- left atrium only need to pump blood into the ventricle, over a short distance
(c) Background: Describe the functions of the SAN, AVN and Purkyne tissues in relation
to initiation and coordination of heart contraction.
Answer:
- heart mucles are myogenic
- SAN natural pacemaker that sends out excitation waves/impulses that causes
atrial muscle contraction
- AVN delays contraction of ventricles
- by about 0.1seconds in order to allow ventricles to fill up with blood
- then transmits the impulses to Purkyne tissue
- Purkyne tissue conducts the impulse down the septum to apex of the heart
- ventricles contract
- blood is forced into the arteries
(d) Background: state the effects of atherosclerosis on blood flow through coronary
arteries and the effect on the heart itself.
Answer:
- fat/cholesterol deposited in lining of coronary arteries
- and causes lumen of artery to narrow
- leads to reduced blood flow in coronary arteries
- creating higher blood pressure
- less (NOT “NO”) oxygen is supplied to heart muscles
- less waste materials removed
- heart muscles contract less strongly
- leading to heart failure/heart attack/myocardial infarction
- risk of thrombosis/blood clot also increases
- cardiac muscles may die
G (MAMMALS) QUESTION 11
(a) Background: You need to understand the graph – should be very simple for an A
Level student! (1 mark)
Answer:
- A: ventricular systole (reason: ventricular pressure exceeds atrial pressure)
- B: complete cardiac diastole (reason: both ventricular and atrial pressures are
low)
(b) (i) Background: Popular/Easy question to answer. (1 mark)
Answer:
- thicker cardiac muscle layer/thicker wall to generate high pressure. This
allows blood to be pumped to all parts of the body (except the lungs).
(ii) Background: This is a comparison question; compare blood pressures in left and
right ventricles and then explain why. (2 marks)
Answer:
- oxygenated blood from left ventricle needs to be transported to all parts of
the body (except lungs)
- right ventricle only needs to pump blood to lungs and this is a short distance
(c) (i) Background: Explain what happens in the heart when left ventricle pressure
exceeds aortic/aorta pressure. (2 marks)
Answer:
- semilunar valves of aorta open as pressure in ventricle is higher than pressure
in aorta
- atrioventricular/bicuspid valves closed
- ventricular systole / oxygenated blood is squeezed out of ventricle into aorta
(ii) Background: Be careful when explain how backflow is prevented. (1 mark)
Answer:
- semilunar valves are pushed shut by high pressure in aorta after ventricular
systole/during ventricular diastole
(d) (i) Background: Pressure changes are caused by cardiac muscles and
presence/absence of blood. (2 marks)
Answer:
- contraction of right ventricle wall increases pressure, relaxation causes
decreased pressure
- inflow of blood into right ventricle also causes increased blood pressure
(ii) Background: Explain what is happening in the right atrium when there is lower
pressure in the right ventricle. (2 marks)
Answer:
- tricuspid valve opens
- blood accumulated in the right atrium will passively flow into the right
ventricle
(e) Background: Explain why there is suddenly a small increase and then decrease
(surge) in pressure in the right atrium and right ventricle at X. (2 marks)
Answer:
- (referring to right atrium) atrial systole / right atrium walls contract (pressure
increases), pressure within increases and tricuspid valves open, causing blood
to be conveyed into ventricle (pressure decreases in right atrium)
- (referring to right ventricle) as blood is forced into ventricle, there is a sudden
small increase in ventricular pressure while ventricle is in diastole.
(f) (i) Background: Tricuspid valve is closed when the right ventricle is in systole. (1
mark)
(ii) Background: Pulmonary artery (semilunar) valve is closed when the right
ventricle is in diastole. (1 mark)
G (MAMMALS) QUESTION 7
(a) (i) Background: You should be familiar with the parts (and function) of a
haemoglobin molecule.
Answer:
- X: haem group (Spelling is important, wrong spelling  no mark awarded!)
- haem group transports oxygen
(ii) Background: There are two parts to this question. First explain why haemoglobin
is a globular protein. Then, explain why it has a quaternary structure. To answer, you
must know the definitions of the different levels in protein organization.
Answer:
- globular: the polypeptide chains fold to give haemoglobin a spherical shape
- quaternary structure: haemoglobin made up of 4 polypeptide chains
(b) Background: Be systematic in your answer for this question.
Answer:
- iron is needed in the formation of haem group
- deficiency in iron (DOES NOT MEAN NO IRON – means not enough
iron so there is SOME iron) means less harmoglobin is made
- less oxygen delivered to tissues
- less respiration takes place (since aerobic respiration requires oxygen)
(c) Background: You must know the location of myoglobin.
Answer:
- muscle tissue (e.g. cardiac, skeletal)
(d) (i) Background: This question tests your graph-reading skills.
Answer:
- myoglobin at 2kPa: 90% saturation
- haemoglobin at 2kPa: 23-25% saturation
(ii) Background: Using the answers to the previous part, explain the difference in
percentage saturation.
Answer:
- haemoglobin releases oxygen
- readily at higher partial pressures of oxygen (e.g. in tissues/cells)
- while myoglobin has a higher affinity for oxygen
- acting as an oxygen store
- that will not release oxygen until partial pressure is very low
- especially during strenuous exercise (where oxygen demand exceeds oxygen
uptake)
- so delays anaerobic respiration (respiration process when there is oxygen
shortage)
(e) Background: A bit of knowledge is required to draw the dissociation curve for
haemoglobin when carbon dioxide partial pressure is increased.
Answer:
-
S-shaped curve to the right of curve H
Curve should start at origin (0), level off at between 90-98% saturation, 50%
saturation by 6kPa
G (MAMMALS) QUESTION 9
(a) Background: Popular question. Be careful, as this question requires you to make
comparison statements! Refer to diagram given.
Answer:
- artery wall is thicker than the vein wall, which is thinner
- artery has a smaller lumen relative to wall, compared to vein which has a
larger lumen
- artery wall has more elastic tissue/thicker tunica media compared to vein,
which has less elastic tissue/thinner tunica media
- artery has folded lining/tunica intima, while vein has smooth lining/tunica
intima
- artery has a thicker wall to diameter ratio, while vein has a thinner wall to
diameter ratio
- artery is more circular in shape compared to the irregular shape of vein
(b) Background: Straightforward question regarding role of capillaries in lungs; mention
the structure of capillaries and relate to their roles.
Answer:
- provide large surface area to volume ratio
- for efficient gaseous exchange
- provides short diffusion distance as capillary wall only one cell thick (1-2m)
- small size of capillaries enables blood to be as close as possible to air in
alveolus
(c) Background: Harmful effects of tar on lining of gaseous exchange system.
Answer:
- paralyses cilia
- goblet cells produce more mucus
- tar contains carcinogens that damage DNA of cells in the lining
- cancerous tumours develop due to uncontrolled cell division
- lining is replaced by scar tissue and becomes thick – this decreases lumen
size of airways and leads to breathing difficulties