Biology Flashcards
(147 cards)
1
Q
How does the motor end /neuromuscular junction depolarise the muscle fibre ?
A
When action potential arrives at the synapse they cause calcium ions to leak/enter into the synaptic knobs
Causes release of acetylcholine from the synaptic knobs
Attaches to receptions on sarcolemma
Making it permeable to sodium ions
Rush into fibre causing depolarisation
2
Q
Explain briefly how part G depolarises the muscle fibre.
A
when action potentials arrive at the synapse they cause calcium ions to leak/enter into the synaptic knobs; (this) causes release of acetylcholine from the synaptic knobs;
this attaches to receptors on the sarcolemma;
making it permeable to sodium ions;
so that they rush into the fibre causing depolarisation;
3
Q
State one function of each of the parts labelled Dendrite, Myelin sheath and Schwann Cell
A
A- receives action potentials from preceding/relay/intermediate/connector neurones;
B- insulates axon causing saltatory conduction;
C -secretes the myelin;
4
Q
Distinguish between parts Grey matter (A) and White matter (B)
A
A consists of non-myelinated relay neurones running across the spinal cord; B consists of myelinated relay neurones running up and down the spinal cord;
5
Q
What neurones carry impulses to muscles and glands
A
Motor
6
Q
What neurones carry impulses from receptors to the central nervous system
A
sensory
7
Q
In resting nerve fibre what is there a lower concentration of?
A
Sodium ions
8
Q
Low sodium levels is a result of what?
A
due to the actions of a sodium pump in its membrane
9
Q
How is the resting potential described at rest in comparison with the outside?
A
Negative resting potential
10
Q
When does depolarisation occur
A
Depolarisation occurs when the membrane permeability is changed by a stimulus allowing sodium ions to flood in
11
Q
when will the depolarisation be propagated along the fibre?
A
If the depolarisation reaches a threshold value
12
Q
In some fibres an insulating layer of myelin allows the depolarisation to jump between …………………………………………..
A
Nodes
13
Q
Impulses are propagated across synapses by release of …………………………………..
A
acetylcholine
14
Q
acetylcholine release is triggered by an inflow of …………………………………….. ions
A
Calcium
15
Q
How is a resting potential generated
A
axon membrane is impermeable to sodium ions but permeable to potassium ions;
sodium pumped out of axon to surrounding tissue fluid;
thus there is a lack of positive ions within the axon which tends to draw potassium ions in; this inflow of potassium is also supplemented by a weak potassium pump;
however, inflow of potassium ions cannot quite catch up with outflow of sodium ions;
and so inside stays negative with respect to outside;
ATP required to allow pumps to work;
16
Q
Where are paccinian corpuscles found?
A
Under skin
17
Q
Where are beta cells found?
A
Islets of Langerhan
18
Q
What are found in islets of langerhan
A
Beta cell
19
Q
What do Beta cells do?
A
raise blood glucose level
20
Q
What is the threshold stimulus
A
the smallest stimulus that is capable of setting up an action potential;
21
Q
Describe what is happening when potential difference in increasing
A
stimulus makes axon membrane become permeable to sodium ions; these flood into the axon along the diffusion gradient;
thus polarity of membrane reverses to give action potential;
22
Q
What happens when the potential difference begins to fall again?
A
too many positive ions are inside the axon at this stage;
membrane is now super permeable to potassium which floods out of axon along (electrical) gradient;
thus potential across membrane reverses back to resting value, (although correct ionic balance is not yet restored);
23
Q
Describe how action potentials are propagated along the axon during nerve impulse transmission.
A
propogated by local currents;
electron flow occurs at margins of depolarised (+) and resting/repolarised (-) regions;
these currents make next bit of axon membrane permeable to sodium ions and so region of depolarisation spreads;
24
Q
Why do synaptic knobs contain many mitochondria?
A
provide ATP;
to provide energy for active absorption of acetate/choline into the knobs;
for combining acetate and choline/to make acetylcholine/synthesis of acetylcholine;
25
Briefly describe how the arrival of an impulse at the synapse causes depolarisation of the post-synaptic membrane.
calcium ions enter synaptic knobs;
and attract vesicles to the pre-synaptic membrane;
these fuse with the membrane and release acetylcholine;
this attaches to receptors on post synaptic membrane;
making it become permeable to sodium ions;
these rush into the muscle fibre along the concentration gradient;
this alters the potential across the sarcolemma/membrane resulting in an action potential;
26
(iii) How does the post-synaptic membrane become repolarised?
acetylcholine esterase enzyme is released as soon as the muscle is depolarised; this removes the acetylcholine from the receptors;
by hydrolysing/splitting it into acetate and choline;
thus membrane of muscle reverts to being impermeable to sodium ions;resting potential is restored;
27
How does an adrenergic synapse differ from a cholinergic synapse?
the transmitter substance is nor-adrenaline;the enzyme which removes it from the receptors is mono-amine oxidase;
28
(ii) Where are adrenergic synapses found in the body?
(ii) in the sympathetic nervous system;
29
(ii) Distinguish negative feedback control from positive feedback control.
negative feedback control is when a varying physiological value is returned to its mean value by the controlling mechanism (credit example. eg. sweating to reduce body temperature);
positive feedback control is when a physiological value is pushed above its mean value by the controlling
mechanism (credit example eg. increased uterine contractions in birth);
30
Give one example of negative feedback control and one example of positive feedback control in mammals
-ve : normal body temperature/blood pressure/blood osmotic pressure/blood pH/ventilation rate/any correct eg;
+ve : oxytocin release during birth/oxytocin release in suckling/body temperature during fever/any correct eg;
31
(iv) What do you understand by the term ‘damping’?
the reduction or suppression of a feedback control mechanism when the required physiological value is reached; (usually feedback control mechanisms are not completely turned off)
32
Describe the roles of the thermoreceptors
thermoreceptors in skin sense surface/shell temperature;
thermoreceptors in hypothalamus sense core/blood temperature;
relay nerve impulses to heat gain/heat loss/thermoregulatory centres in hypothalamus;
33
Baroreceptors are...
baroreceptors sense blood pressure;
situated in walls of arterial arches/bases of great veins/aortic and carotid bodies;
relay nerve impulses to vasomotor centre in brain/medulla (to regulate cardiac output/blood pressure);
34
glucoreceptors..
glucoreceptors sense blood glucose concentrations;
situated on cell membranes of alpha and beta cells of the islets of Langerhans;
if blood glucose concentration rises beta cells stimulated to release insulin to lower it
/if blood glucose concentration falls alpha cells stimulated to release glucagon to raise it;
35
proprioceptors...
proprioceptors are tension and pressure receptors;
situated in muscles and tendons/ ligaments/joint capsules;
send nerve impulses to cerebellum to regulate muscle tone/enable balance/coordinated movements;
36
what happens when blood glucose levels fall?
glucose absorption from gut to blood is reducing/stopping; β-cells release more insulin;
α-cells release less glucagon;
conversion to glycogen for storage is faster than absorption;
37
what happens when blood glucose levels increase?
glucose being absorbed from gut (into blood stream); faster than it is being converted to glycogen;
and stored in liver/muscles;
under the influence of insulin;
38
Regulators are
regulators are organisms that regulate or control their physiological values within narrow limits; any one of: mammals/birds/flowering plants/specific example of these;
39
Non regulators
non regulators do not control their physiological values within narrow limits;
any one of: cnidarians/algae/specific example of these;
(most other organisms are regulators for some values and non regulators for other values)
40
The presence or absence of ADH in the blood is controlled by .....................................................
negative feedback
41
Receptors in the .......................................... sense an increase in the ................................................ of the blood plasma
hypothalamus, osmotic pressure
42
Hypothalamus transmit nerve impulses to the ................................................................ which releases ADH into the blood
posterior pituitary body
43
posterior pituitary body releases ADH into the blood by
| ....................................
neurosecretion;
44
ADH attaches onto target receptors on the ............................................................. cell membranes
collecting duct;
45
ADH has the effect of making these membranes ........................................
water permeable;
46
WATER PERMEABILITY allows water to be............................................... .
reabsorbed
47
Hormone - Breakdown of glycogen in the liver
glucagon/adrenaline;
48
Hormone - Non shivering thermogenesis
adrenaline;
49
Hormone - Lowering of blood glucose concentration
insulin;
50
Hormone -Acceleration of heart beat
adrenaline/thyroxine;
51
Hormone -Reduction of water loss in urine
antidiuretic hormone;
52
Hormone -Increase in flow of gastric juice
gastrin
53
Hormone -Increase in antibody release by plasma cells
interleukin;
54
Why must water gain be balanced by water loss?
so that water content of body is maintained at constant level/no dehydration/ no over dilution;
so that blood concentration/osmotic pressure/volume/blood pressure can be kept constant;
55
What is the counter current principle in the loop of henle?
ascending limb of loop of Henle is always impermeable to water;
but has a very powerful active transport mechanism for pumping Na+/Cl- out of tubule (into interstitial fluid); this lowers the concentration as tubular fluid rises up ascending limb;
Na+/C1- diffuse into descending limb (from higher concentration in surrounding interstitial fluid);
raising concentration of tubular fluid as it passes down the decending limb;
56
(ii) What are the functions of the counter current principle in the loop of Henle.
maintains a high salt concentration in the medulla/interstitial fluid;
this enables water reabsorption from the collecting ducts (when ADH is present);
57
(i) Negative feedback: ....................................................................................................................................
when for instance, blood volume varies above or below its norm;
a mechanism is operated to bring the varying value back to the norm;
58
Neurosecretion
(iii) when a hormone is secreted as a result of nervous stimulation; 1
59
(c) Explain why a rise in blood pressure will increase urine production.
Any four of:
increased blood pressure increases glomerular blood pressure/
increases ultrafiltration/
thus a larger volume of glomerular filtrate is formed (per unit time)/
raised blood pressure inhibits ADH release/
thus collecting ducts become impermeable to water/
thus no water reabsorbed from urine so urine volume increases;;;; 4
60
(ii) Explain why there is an increase in pulse rate as a result of exercise.
additional activity/use of muscle uses more energy; respiration increases to supply additional energy/ATP; increased circulation supplies additional oxygen/glucose; removes carbon dioxide/heat/lactic acid;
61
Mark is a professional footballer. Paul writes software for computer games. How could this account for Mark’s lower resting pulse rate and smaller increase in pulse rate after exercise?
(ii)
mean increase in pulse rate = 35.4, mean pulse rate = 72; = 35.4 × 100 = 49.2 % ;
72
additional activity/use of muscle uses more energy; respiration increases to supply additional energy/ATP; increased circulation supplies additional oxygen/glucose; removes carbon dioxide/heat/lactic acid;
regularexerciseimprovesheartperformance/efficiency; increased heart force/stronger beat/greater stroke volume; more blood circulates per beat so rate falls;
muscles work more efficently so require less O /glucose;
62
(i) During exercise the volume of oxygen used by the tissues increases.
muscle contraction requires more ATP;
produced by oxidative phosphorylation;
aerobic respiration/respiratory chain/electron transport chain require more oxygen;
63
(ii) Following exercise the tissues continue to use a greater than usual volume of oxygen.
must restore oxygen debt;
by re-oxidising accumulated lactic acid;
oxygen content of haemoglobin/myoglobin is restored; ATP/creatine phosphate stores built up;
increased temperature causes increased metabolic rate;
64
(a) Explain how exercise could have caused the change in the oxygen dissociation curve.
exercise caused increased temperature (which shifts curve to the right);
increased CO concentration at tissue level (due to greater respiration); 2
decreased CO
causes shifts in blood pH/Bohr shift/to pH 7.6 in lungs/pH 7.2 in tissues; (thus) curve moves to the right in tissues/to the left in lungs;
65
(ii) cardiac output. ...........................................................................................................................................
the volume of blood (in dm3) pumped out of the heart/ventricles per minute;
66
(c) Suggest explanations for the differences in cardiac efficiency of the athlete and non-athlete.
cardiac efficiency greater in athlete/converse;
training develops more/stronger cardiac muscle/converse;
coronary circulation becomes more efficient in athlete/no plaques/reductions in arteriole diameter due to lipid deposits/converse; more efficient ventilation/breathing in athlete means CO chemoreceptors do not increase cardiac output as much (by
negative feedback);
67
(a) State where in the cell this stage(cell respiration) would take place.
cytoplasm
68
(c) In aerobic conditions what will be the immediate fate of the pyruvate?
enters mitochondrion;
| converted to acetylcoenzyme A;
69
(d) Outline the role of coenzymes in aerobic respiration.
```
Any three of: NAD/FAD/
receive electrons / H+/ are reduced/
coenzymes are reoxidised in the electron transport chain/
generating ATP/
by oxidative phosphorylation;;;
```
70
(i) Suggest why ADP and ATP are effective energy carrier molecules.
intermediate position;
| means that they can accept or donate (energy rich) phosphate;
71
(ii) Suggest why high levels of creatine phosphate are found in striated muscle tissues.
adenine; 1
ribose;
intermediate position;
means that they can accept or donate (energy rich) phosphate;
Any two of:
(very) high energy content/
allows rapid/sudden contraction/ since ATP synthesis is relatively slow;;
72
Name product that enter kreb cycle
(a) X pyruvate/acetyl coenzyme A;
73
Name product that leaves at beginning
CO2
74
where does kerb cycle occur
matrix of mitochondria
75
(ii) electron carriers are situated. ................................................................................................................ [1]
(ii) cristae/inner membrane of mitochondria;
76
(c) Explain the term ‘coupled redox reaction’.
carriers are alternately reduced and oxidised;
gain of electrons/hydrogen = reduction/loss of electrons/hydrogen = oxidation; linked to ATP synthesis/oxidative phosphorylation;
77
(d) Suggest why cyanide poisoning victims suffer from severe ATP shortage.
cyanide stops the flow of electrons/blocks the electron transport chain/blocks cytochrome oxidase;
prevents regeneration of NAD/FAD from NADH/FADH or prevents reoxidation of NADH/FADH/cytochromes; thus ATP synthesis is inhibited;
78
What enter beginning of glycolysis
ATP
79
(c) Use the information in the diagram to explain the term ‘feedback inhibition’.
high levels of ATP;
| inhibit conversion of intermediate 1 to intermediate 2; prevents excess production of ATP;
80
(b) Explain why ATP molecules are used in the first stage of glycolysis.
(b) provides activation energy/makes glucose more reactive;
81
(c) What type of chemical reaction is involved in the conversion of triose phosphate to pyruvate?
(c) dehydrogenation/oxidation/redox reaction/(if say reduction must specify NAD → NADH);
82
(d)How is NADH reoxidised in anerobic conditions in:
hydrogen from NADH used to reduce pyruvate to lactate; (ii) hydrogen from NADH used to reduce pyuvate to ethanol;
83
(e) Outline the process of oxidative phosphorylation.
hydrogen/electrons removed from substrate/intermediate/named intermediate; reference to carriers/NAD/FAD;
passed to successively lower energy levels;
energy released used to convert ADP into ATP/ phosphorylate ADP;
84
What Happens? Glycolysis
Glucose is converted to pyruvic acid; Hydrogen is removed and is passed to the electron carriers.
85
What Happens? Link Reaction;
Pyruvate enters mitochondrion, is decarboxylated, dehydrogenated and combines with coenzyme A to give acetyl coenzyme A. The hydrogen which is removed is passed to the electron carriers.
86
What Happens? Kreb’s Cycle;
A cyclical series of reactions during which hydrogen is passed to the electron carriers, carbon dioxide is removed and a starting reactant is regenerated.
87
What Happens? Electron Transfer Class
The hydrogen from the respiratory reactions is split to release electrons. These pass through carriers and generate ATP;. The hydrogen reforms and is combined with oxygen to release water.
88
(a) Outline how pyruvate is produced in glycolysis.
Any three of:
glucose phosphorylated/activated/
using ATP/
split into 3C/triose phosphate/ oxidation/dehydrogenation of trioses yields pyruvate;;;
89
What do phosphorllyase enzymes do
Adds phosphate to ADP to produce ATP
90
dehydrogenase enzymes
remove hydrogen from substrates/oxidise substrates/pass hydrogen to acceptors;
91
(c) Briefly explain why anaerobic respiration produces much less ATP than aerobic respiration.
without oxygen there is no final acceptor for electrons/hydrogen from electron transport chain; hence no regeneration /reoxidation of coenzymes;
thus Krebs cycle stops;
electron transport chain and Krebs cycle provide most of the ATP;
92
coenzyme
organic molecules necessary for enzyme function;
not permanently attached to the enzyme;
involved in transfer of hydrogen/electrons/acetate groups/energy/any other correct example;
93
(ii) What is meant by the term ‘prosthetic group’?
(ii) similar to coenzyme but tightly bound to one specific enzyme;
94
(b) Suggest why individuals who are deficient in B complex vitamins may suffer from a lack of energy.
vitamin B complex/nicotinic acid/riboflavin is required for synthesis of NAD/FAD; pantothenic acid/coenzyme A required to produce acetyl CoA from pyruvate;
less acetyl CoA means less substrate for the Krebs cycle;
NAD/FAD are hydrogen acceptors in respiration;
if deficient electron transport chain may be impaired so less ATP produced;
95
(i) the name of one process by which glucose enters cells.
facilitated diffusion/active transport;
96
(i) why glucose is first converted into glucose-6-phosphate.
to make glucose reactive/phosphorylation gives energy of activation/keeps glucose inside cell/there are no carriers for glucose-6-phosphate in the cell membrane/keeps concentration of free glucose inside cell low so maintains concentration gradient;
97
(ii) why this stage is vital in red blood cells.(glycolysis)
they lack mitochondria;
| therefore rely on glycolysis to provide energy;
98
(a) (i) Where does this process mainly occur in the body? (removal of amino acids )
liver
99
In which organ of the body does this process mainly occur? ............................................................... [1](ornithine)
liver
100
(ii) What type of pumps are the electron chain carriers? Explain why.
proton pumps;
| because they move hydrogen ions which are protons;
101
(iii) What are the functions of ATPase?
proton pumps;
| because they move hydrogen ions which are protons;
102
State two ways in which the structure of the wall of the bronchus would be different in a long-term smoker.
cilia, destroyed / damaged; R cilia not working
(epithelium replaced by) scar tissue / scarring;
(smooth) muscle becomes thicker;
mucous glands enlarge / larger goblet cells / more goblet cells; R more mucus secreted
inflammation of connective tissue;
AVP; idea of tumour if it describes a structural change
103
One feature of the disease emphysema is that the alveoli lose their elasticity.
Explain the effects of this loss of elasticity on the gaseous exchange system of a person with emphysema.
tidal volume is reduced / less air inhaled and exhaled / residual volume is larger / air trapped in alveoli / vital capacity smaller; more difficult to exhale;
(as) alveoli cannot, stretch / recoil;
rapid / shallow, breathing / breathlessness / wheezing; alveoli may burst;
leaves gaps in tissue / larger air spaces / AW;
less surface area (for gaseous exchange);
blood / haemoglobin, less well oxygenated / less carbon dioxide removed;
104
At a certain point, the student was asked to breathe in as deeply as possible and then breathe out as much as possible. The resulting change in the trace is shown in the diagram as X.
(ii) vital capacity;
105
(iii) State two features of a gas exchange surface, such as the lining of the alveolus.
```
large surface area; permeable;
thin / short, diffusion path;
moist;
good blood supply / close to blood;
well ventilated / in contact with respiratory medium;
```
106
Explain what is meant by a double circulatory system.
(blood flows) twice through the heart / AW;
for one circuit / cycle (of the whole body) / AW; A for one heart beat ref pulmonary and systemic systems / to lungs and to (rest of) body; R systematic
107
Explain, with reference to its function, why the wall of left ventricle is much thicker than the walls of chambers D and E.
provides more, force / pressure, to pump blood around body;
longer distance compared with distance right ventricle has to pump blood; or right atrium;
AVP; e.g. detail of pulmonary circulation
108
Haemoglobin, a pigment found in the blood of mammals, has an important role in the transport of respiratory gases. Each haemoglobin molecule contains haem groups. In the lungs, oxygen binds with the atom of .............................. in each haem group. The maximum number of molecules of oxygen that can be carried by one molecule of haemoglobin is .............................. . In areas like muscle tissue where the partial pressure of oxygen is low, oxygen dissociates from the haem group. This dissociation is increased by the presence of carbon dioxide; this is called the .............................. .............................. . Most of the carbon dioxide produced in respiring tissues diffuses into the red blood cells where the enzyme .............................. ........................ catalyses a reaction leading to the production of hydrogen ions and hydrogen carbonate ions. The hydrogen ions combine very readily with haemoglobin to form a compound known as .............................. .............................. . The effect of this is to increase the release of oxygen from haemoglobin.
iron / Fe; four / 4;
| Bohr, effect / shift; carbonic anhydrase; haemoglobinic acid;
109
Name two white blood cells and their functions
Neutrophil/phagocyte - engulfing/phagocytosis
Lymphocyte - produce/release, antibodies
110
(ii) Explain how the lumen of the artery has become narrowed at point Y.
high concentration of, cholesterol / LDL, in blood; endothelium / lining damaged;
deposition (fat / cholesterol) in wall of artery; R “on artery” ref to plaque / atherosclerosis / atheroma;
111
Suggest how doctors might treat a patient with narrowing of the arteries that supply the heart muscle.
ref to suitable drug; e.g. anticlotting, blood pressure reducing, diuretic bypass operation;
stents fitted;
angioplasty / balloon on catheter;
AVP; e.g. name of drug
extra detail about a named drug or one of above procedures
112
Suggest two pieces of advice that a doctor might give to such a patient to try to reduce the likelihood of further narrowing of the arteries.
avoid, saturated / animal, fats; A cholesterol
eat, unsaturated fats / polyunsaturated fats / plant oils / fish oils; qualified ref to, more / regular, exercise;
avoid smoking;
avoid stress;
eat more, fruit / vegetables / antioxidants; A moderate intake of red wine reduce weight;
reduce alcohol intake;
eat more soluble fibre;
ref to vitamin D production / exposure to sunlight;
113
The diagram shows that the pressure rises and falls in the arteries.
Explain what causes this rise and fall in pressure.
the heart / ventricle / cardiac muscle (involved); peaks coincides, with, systole / contraction; R pump troughs coincide, with, diastole / relaxation / AW; stretch-recoil effect / AW;
must link to rise / fall not just a general statement
114
the rise and fall in pressure seen in the arteries is not evident by the time the blood enters the capillaries
• the pressure is much lower by the time the blood enters the capillaries. Explain what causes the changes described above.
distance (from heart) qualified, e.g. further / around the body / AW; friction / resistance to flow / AW;
less / no, stretch-recoil effect / AW;
increasing volume of, arterioles / capillaries;
A surface area of capillaries / large capillary bed / many capillaries / branching
115
Explain why it is important that the pressure is lower by the time blood reaches the capillaries.
stop damage (to capillaries );
A stop bursting R ‘can’t cope’ A ‘can’t withstand’
lack of (much) elasticity / thin / delicate / fine / one cell thick /
no collagen / no muscle; ora for artery wall
slows flow rate;
allows time (for);
exchange / AW; A one named substance moved, but R “food” oedema risk reduced / high pressure might force out more tissue fluid;
116
Without the Purkyne tissue, blood would not be pumped out of the heart efficiently.
(Purkyne fibres) conduct wave of excitation / AW;
R impulse, signal, pulse
to the, base / apex, of heart;
so contraction occurs upwards / AW; both ventricles contract together;
117
In anaerobic conditions, Pryuvate does not proceed to the link reaction. Describe the fate of compound F during anaerobic respiration in an animal cell and
explain the importance of this reaction.
Award marks from labelled / annotated diagrams – but ensure that mp 2 only awarded if H clearly shown to be accepted by pyruvate
1 (pyruvate / F) converted to lactate;
ACCEPT lactic acid
DO NOT CREDIT if pyruvate → ethanol in the animal is indicated/implied
DO NOT CREDIT wrong reaction type (e.g. oxidation)
2 F / pyruvate, accepts hydrogen (atoms); ACCEPT pyruvic acid
DO NOT CREDIT hydrogen ions (unless also e–) / molecule
3 hydrogen from, reduced NAD / reduced E;
ACCEPT NADH / NADH2 / NADH + H+
4 (catalysed by) lactate dehydrogenase;
for pyruvate → lactate ACCEPT LDH
5 no, oxygen / O2, to act as (final),
hydrogen / electron, acceptor;
6 (so) link reaction / Krebs cycle / ETC, cannot take place;
Needs a clear statement of not taking place
CREDIT no, electron transport chain / electron carrier chain / chemiosmosis / oxidative phosphorylation
7 NAD / E, regenerated / recycled / able to be re-used;
IGNORE reduced NAD, oxidised / reoxidised (as this does not
give the idea of reusing it)
8 allows glycolysis to continue / pyruvate continues to be made; Needs a clear statement
9 limited / small amount of / some, ATP can be produced;
CREDIT 1 ATP (per pyruvate) / 2 ATP (rather than 28-38 per
glucose) / only substrate level phosphorylation IGNORE ‘enough ATP for ...’
118
State what is meant by the term respiratory substrate.
a biological molecule that can be broken down in respiration to release energy;
119
ATP is made directly by substrate level phosphorylation in the Krebs cycle.
State the number of ATP molecules that are made directly per ‘turn’ of the cycle.
1
120
State the number of reduced NAD and reduced FAD molecules that are formed in the Krebs cycle from one molecule of acetyl CoA.
3
| 1
121
State where the reduced NAD and reduced FAD molecules are reoxidised
and describe what happens to the hydrogen atoms.
inner mitochondrial membrane/cristae;
ref to (NADH) dehydrogenase;
3 hydrogen split into protons and electrons;
4 ref to, electron carriers/ETC/cytochromes;
5 energy released from electrons;
6 ref to protons pumped across membrane;
7 protons accumulate in intermembranal space;
8 proton gradient/pH gradient/H+ gradient;
9 protons pass through ATPase; A ATPsynthase/
ATP synthetase/stalked particle
10 ref. to oxygen (final) hydrogen/electron acceptor;
11 formation of water;
122
The liver is responsible for producing enzymes which detoxify alcohol by breaking it down into smaller units. This breakdown by enzymes uses NAD. This means that other reactions that use NAD are less likely to take place. The build up of fats in the liver is one of the first signs of liver damage due to excessive alcohol intake.
Using the information in the diagram above, explain why the build up of fats occurs in the liver of an individual who consumes large amounts of alcohol.
fats/fatty acids, not respired;
ref to (β-)oxidation (of fatty acids) requires NAD; NAD used in breakdown of alcohol;
NAD is, limiting/in short supply/AW;
fats formed from fatty acids plus glycerol;
AVP; e.g. further detail of alcohol/fat metabolism
123
With reference to the figure, state the letter, A, B or C, in the glycolytic pathway where the following processes occur.
phosphorylation using ATP dehydrogenation
formation of ATP
splitting of a hexose
A
C
C
D
124
Many chemicals will ‘uncouple’ oxidation from phosphorylation. In this situation, the energy released by oxidation of food materials is converted into heat instead of being used to form ATP. One such compound is dinitrophenol, which was used in munition factories for the manufacture of explosives during the First World War. People working in these factories were exposed to high levels of dinitrophenol.
Suggest and explain why people working in munitions factories during the First World War became very thin regardless of how much they ate.
dinitrophenol in body ; ETC still functioning ;
less ATP formed in respiration ;
food not enough to meet metabolic demands of body / AW ; had to respire, body tissues / food stores ;
AVP ; e.g. heat production increasing metabolic rate
125
Describe two effects of smoking on gas exchange in the alveoli.
soot/tar in alveoli reduce uptake of oxygen and release of carbon dioxide; some carbon monoxide will be absorbed into blood;
126
Chemoreceptors in the body are involved in the regulation of breathing rate. What chemical are they sensitive to?
(ii) hydrogen carbonate ions/dissolved CO2 ;
127
(iii) Name two sites of these chemoreceptors in the body.
carotid bodies/aortic bodies/medulla or brain stem;;
128
(c) (i) The inspiratory and expiratory control centres are in the brain. In which part of the brain are they?
medulla/brain stem; 1
129
With reference to the intercostal muscles, diaphragm and ribs describe the process of inspiration in a human.
Any four of:
external intercostal mucles contract/
internal intercostal mucles relax/
rib cage pulled upwards and forwards/
diaphragm contracts flattening (from a dome shape)/
enlargement of thoracic cavity causes negative pressure in (airtight) pleural cavity/
thus (elastic) lungs inflate with reduced pressure and air is drawn in;;;; 4
130
Respiratory surfaces generally need to be large in relation to the size of the organism. Explain why this is so.
```
to enable absorption of adequate quantities of oxygen/removal of carbon dioxide produced;
to meet (metabolic) needs of the organism/so metabolism is not limited by oxygen supply/carbon dioxide removal;
```
131
Explain the physiological significance of the shift from A to B on the behaviour of haemoglobin in the tissues and alveoli.
during respiration pH of tissues falls/temperature increases/CO 2
tension rises; oxygen tension falls since used up in tissues;
thus release of oxygen from haemoglobin to tissues is made easier/haemoglobin is on curve B in tissues; converse at alveoli/haemoglobin on curve A and so oxygen uptake is easier;
132
(a) Explain why the fetal oxygen dissociation curve lies to the left of the adult curve.
fetal haemoglobin must onload oxygen; from maternal haemoglobin;
across the placenta;
when maternal haemoglobin is offloading oxygen (in placenta);
thus at pO
fetal haemoglobin must be onloading it (in placenta);
133
Describe two other adaptations that enable oxygen to be transported rapidly from maternal blood into the fetal tissues.
erosion/reduction of tissue layers in placenta/between maternal and fetal blood;
increase in maternal blood supply to placenta giving larger exchange surface area;
foramen ovale/hole in wall from right atrium to left atrium (allowing rapid shunting of oxygenated blood from right to left side of fetal heart);
ductus arteriosus/shunt from pulmonary arch to aortic arch (allowing direct passage of oxygenated blood from right side of heart to aorta);
134
Shortly after birth fetal haemoglobin is broken down and replaced by adult haemoglobin. Why is fetal haemoglobin unsuitable for use after birth?
has greater affinity for oxygen than adult haemoglobin; higher oxygen tensions in atmosphere than placenta; thus in air would be unable to unload oxygen to tissues;
135
What important differences, other than oxygen or carbon dioxide content, would be present in the composition of the blood in the following pairs of vessels?
hepatic portal vein and mesenteric/intestinal artery after a meal
hepatic portal vein would contain a higher concentration of absorbed food substances than intestinal artery ; higher concentration of glucose;
higher concentration of amino acids/other valid example;
136
What important differences, other than oxygen or carbon dioxide content, would be present in the composition of the blood in the following pairs of vessels?
hepatic portal vein (B) and hepatic vein(F)
B would have a higher glucose concentration than F (since glucose stored as glycogen in liver); B would have a higher amino acid content than F (since extra amino acids deaminated in liver); F would a higher urea concentration than B (due to deamination)
137
What important differences, other than oxygen or carbon dioxide content, would be present in the composition of the blood in the following pairs of vessels?
D = renal artery;E = renal vein;
D would have a higher urea concentration than E (since urea is excreted);
D would have a higher uric acid/ammonia concentration than E (due to excretion);
138
One product manufactured using microorganisms is insulin. The process involves genetically engineering bacteria to synthesise human insulin.
(i) Describe how the isolated human insulin gene is inserted into a bacteria plasmid.
plasmid cut by restriction enzyme;
at specific sequence;
same enzyme as used to cut (insulin) gene; sticky ends / described;
ref. complementary sticky ends;
ligase seals (sugar-phosphate) backbone / AW;
139
Suggest two ways in which the bacteria which take up the modified plasmids can be identified.
credit any two from the following:
1 antibiotic resistance (gene) introduced and survivors have plasmid;
2 fluorescent marker (gene) introduced and glowing bacteria have plasmid;
3 identify bacteria producing insulin using antibodies;
140
Suggest one ethical objection to the use of stem cells from human embryos
R questions
embryo, potential human/member of society/right to life/killed/AW;
may be from abortion;
scientist making decision for use of embryo/consent may not be required; parents may not know fate;
religious objection;
may involve cloning;
some stem cells can be obtained instead from umbilical cord;
AVP;
141
Suggest two other medical conditions which could be treated using the embryonic stem cells shown in the figure.
treat/cure for, anaemia/sickle cell anaemia/named blood disease; blood, for transfusion/to replace loss;
treat, immune disorders/SCID/lupus;
treat, non-Hodgkins lymphoma/some types of cancer/leukaemia; treat/cure for, Alzheimer’s disease;
treat/cure for, Parkinson’s disease;
treat paraplegics/repair injury to, nerves/spinal cord;
treat, genetic disorders affecting nerves/Huntington’s/Tay Sachs/Lou
Gehrig’s;
treat multiple sclerosis/motor neurone disease;
AVP; eg. stroke/brain damage/retinal repair
142
Describe how genetic engineering has been used to produce human insulin and the advantages of obtaining insulin in this way.
identify / find, gene (for insulin) / length of DNA coding for insulin;
2 obtain / isolate / extract,
gene / length of DNA (for insulin); obtain / isolate / extract, mRNA (for insulin);
3 restriction enzyme / named e.g.; reverse transcriptase;
4 cut plasmid; cut plasmid;
5 use same restriction enzyme; use restriction enzyme / named e.g.;
[6]
ref to, complementary ends / sticky ends / described;
7 insert, gene / AW, into plasmid;
8 recombinant DNA;
9 plasmid uptake by bacteria;
10 identify those bacteria that have taken up the plasmid;
11 provide with, raw materials / nutrients;
12 fermenter / bioreactor;
13 bacteria produce insulin;
14 extract and purify / downstream processing;
15 A VP; e.g.. detail of uptake by bacteria
method of identifying ththose that took up plasmid
PCR
ligase 7 max
advantage 1; e.g.
17 advantage 2;
more reliable supply
greater / faster, production overcomes ethical problem described less risk of disease
less risk of, rejection / side effects human insulin so more effective
143
Examples of gene mutations
sickle cell anaemia/albinoism/melanism/any other valid example;;(any two)
144
What is Down’s syndrome?
when an individual receives three copies of chromosome 21 instead of two;
reference to non disjunction/translocation;
reference to learning difficulties/thick set bodies/thick necks/infertility/any other correct symptom;
145
(d) When mutations occur they usually cause discontinuous variation. However, continued gene mutation can lead to continuous variation. Explain how this is s
one gene mutation will produce a new character which will thus be a discontinuous variant;
thousands of similar gene mutations will form a wide range of slightly different characters which will give continuous variation;
146
(a) (i) What is meant by the term ‘polyploidy’?
increase in chromosome number;
| either of individual chromosomes or of complete sets;
147
The type of polyploidy illustrated above involves hybridisation. What name is given to this type of polyploidy?
(ii) allopolyploidy;
