Identify the increased probability of an obese person having hypertension relative to someone who has normal weight.

Explain how the administration of a drug that stimulates the leptin receptors in the hypothalamus could help treat obesity.

24%

a. appetite control (centre) is located in the hypothalamus

b. leptin is a hormone made by fat/adipose cells

c. to inhibit appetite/feeling of hunger
OR
promotes feeling of satiety/fullness

d. the drug mimics the action of leptin

e. (reduced hunger) leads to less food intake/weight loss

Calculate how many grams of protein should be consumed each day. Working is not required.

State one function of sodium in the diet.

Identify, with a reason, which milk provides more energy in a 250 g serving.

Suggest, with reasons, which milk would be recommended for someone with osteomalacia.

50 «g»

water balance/osmoregulation/transmit impulses along nerves/muscle contraction/blood pressure/ sodium potassium pump/sodium-glucose cotransporter / sodium-amino acid cotransporter

whole milk because it contains more fat/energy

Reason is required.

a. skimmed milk has more calcium so better

b. both milks have the same amount of vitamin D so no difference between the two.

Skimmed milk alone is worth no marks. Two reasons are required for both marks. 

Identify cell X shown in the diagram.

Outline the role of the cell in recycling iron in the body.

Explain reasons for the dual blood supply to the liver.

Kupffer cell ✔

a. ingests red blood cells by phagocytosis ✔

b. splits the hemoglobin into heme «and globin»
OR
heme group broken down into iron «and bilirubin»
OR
hemoglobin broken down into iron ✔

c. releases iron for transport ✔

a. the dual supply is the hepatic artery and the hepatic portal vein ✔
Both needed

b. blood in «hepatic» artery provides oxygen to the liver «tissues» ✔

c. the «hepatic portal» vein carries blood from the gastrointestinal tract/intestines ✔

d. the «hepatic portal» vein carries blood rich in nutrients ✔

e. this allows the nutrients to be stored/processed
OR
sugar/glucose/glycogen is stored and released in response to hormones ✔

f. prevents osmotic imbalance due to absorbed nutrients in the blood ✔

Osteomalacia is a condition that can be caused by Vitamin D deficiency. Outline one effect of osteomalacia.

Outline the relationship shown in the graph.

Suggest reasons for this relationship.

Compare and contrast the two ECG traces.

Outline one event that occurs in the heart during the T wave.

softened/weakened bones/bone pain/increased fractures/difficulty walking/stunted growth ✔

a. direct relationship/positive correlation ✔ 

b. increased latitude, higher mortality from falls ✔

Or vice versa

a. higher latitude, lower levels of sunlight ✔

b. less uptake of calcium
OR
less vitamin D ✔

c. higher incidence of osteomalacia leads to higher risk of broken bones/mortality ✔

compare:
a. no difference in the P wave/QRS wave
OR
both traces have all 4 waves/PQRST ✔

contrast:
b. delayed T wave
OR
T wave is shorter/higher in hypocalcemia ✔

Allow reference to events in the cardiac cycle for mpa or mpb

Allow converse statements for mpb.

a. repolarization of ventricles ✔ 

b. ventricles are in diastole/relaxation ✔

Osteomalacia producing weak bones was a common answer. Low calcium levels were also mentioned but this is a cause not an effect of osteomalacia.

Nearly all candidates recognized a positive correlation.

Lack of sunlight leading to less Vitamin D was the most common answer here. Calcium was rarely mentioned.

A difference between the traces was more often seen than a similarity, although many candidates gained the two marks.

Many candidates did not know that ventricular diastole occurs during the T wave.

Outline one consequence for the heart of the eating disorder anorexia nervosa.

The micrograph shows cardiac muscle.

[Source: https://commons.wikimedia.org/wiki/File:Musculocardiaco.jpg by Goyitrina,
licensed Creative Commons Attribution-Share Alike 3.0]

The structure labelled X in the micrograph is a junction between two cardiac muscle cells. Identify the structure labelled X.

breakdown/weakening of heart muscle
OR
electrolyte imbalance affecting the cardiac cycle
OR
low blood pressure/heart rate ✔

intercalated disc ✔

Some answers on the effects of anorexia nervosa on the heart were too vague to receive credit.

Very few candidates recognised an intercalated disc.

Gastric juice is secreted by the wall of the stomach. Explain how the timing of secretion is controlled, with reference to the content of the juice.

a. nervous and hormonal control ✔

b. impulses from sight/smell of food stimulates brain to send nerve impulses ✔

c. impulses cause cells in stomach lining/ parietal cells to secrete acid/gastric juice ✔

d. food entering the stomach stimulates the chemoreceptors/stretch receptors ✔

e. chemoreceptors/stretch receptors send impulses to the brain ✔

f. vagus nerve/brain sends a nervous impulse to endocrine cells in wall of stomach ✔

g. endocrine cells release gastrin into the blood ✔

h. gastrin induces the release of gastric juice to digest proteins ✔

i. secretin/somatostatin decrease gastrin secretion ✔

Most candidates described the function of gastric juice rather than the control of its secretion. There was confusion regarding the different pathways and the responses for this question were very often badly structured and missed out details. For example, candidates often stated things like "the sight/smell of food triggers release of gastric juice" missing out some of the key steps in the pathway. So, although many candidates had a good understanding of the digestive processes in the gut, they could not express the pathways involved in the control of the timing of secretions in sufficient detail to gain full marks. Many students described the content of the juice or the enzymes involved in digestion and fails answer the question satisfactorily.

State one role of fibre in the diet.

Outline control of digestive juice secretion so that digestive juices are only secreted into the gut when there is food present.

Outline the role of intestinal villi.

aids peristalsis / reduces risk of intestinal disorders/cancer/constipation / reduces hunger

a. combination of nervous AND hormonal control 

b. food in stomach stimulates chemoreceptors/stretch receptors / stretches the wall 

c. causes production of gastrin 

d. arrival of chyme to the small intestine triggers the release of hormones/secretin 

e. volume and composition of gastric juices are controlled

a. villi/microvilli provide large surface area 

b. capillary network for absorption and transport 

c. lacteal for absorption and transport of lipids/fatty acids/glycerol / bile resorption 

d. mitochondria in epithelial cells provide energy for absorption

Explain the possible health risks of being overweight.

a. increased risk of hypertension/high blood pressure

b. high cholesterol/LDL

c. «circulatory problems such as» atherosclerosis/plaque/thrombosis/stroke/heart disease

d. increased chance of type II diabetes

    OR

    unable to control blood sugar level

e. possibly develop osteoarthritis/trouble with joints

f. higher risks of cancers

g. overconsumption of fats/sugars leads to the under consumption of essential nutrients

h. gallstones/gall bladder disease

[Max 4 Marks]

Describe the relationship between the maternal blood vitamin D levels and the incidence of seizures.

Deduce the reason for rickets in these infants.

Identify the reason for vitamin D not being considered to be a typical vitamin.

Outline the reason for some amino acids being classified as essential amino acids.

infants from mothers with low levels of vitamin D have an increased chance of developing seizures

Accept answers in the converse.

lack of vitamin D in breast milk OR lack of vitamin D leads to lack of bone mineralization/calcium uptake

it can be synthesized by humans «in skin»

a. they cannot be synthesized by humans 

b. they must be present in the diet

The diagram shows the use of a sphygmomanometer in the measurement of blood pressure.

Identify the systolic pressure and diastolic pressure for this adult male.

Systolic pressure (mm Hg):

Diastolic pressure (mm Hg):

Explain the meaning of systolic and diastolic pressure.

The photomicrograph shows cardiac muscle. Label the structures I and II.

systolic: 115 

diastolic: 77 «mmHg»

Both needed for the mark.

a. «systolic/diastolic» pressure is the force of blood on arteries 

b. systolic pressure is measured when the ventricle contracts
OR
systolic pressure is when blood is being pumped out of the heart 

c. diastolic pressure is measured when the ventricles are filled with blood
OR
heart is at rest/relaxed

I: nucleus 

II: intercalated disc

Explain the heart sounds. 

a. «heart sounds» produced by the closing of the valves ✔

b. first sound «lub» is due to «closure of» the atrioventricular valves ✔ Accept bicuspid/mitral and tricuspid.

c. second sound «dup» is due to «closure of» the semilunar valves ✔ Accept pulmonary/aortic valves.

d. sequence of sounds is lub dup ✔ OWTTE

Using the bar chart, determine the percentage of the recommended daily target of protein consumed by the student.

Suggest which essential dietary requirement might be missing if insufficient protein is consumed by the student.

The tracker indicated that the student had exceeded the recommended intake of dietary sodium. Overconsumption of dietary sodium can lead to hypertension. Explain what is meant by hypertension, referring to specific diastolic and systolic values.

The recommended daily intake of vitamin D is 15 μg. This student consumed just 4 μg. State two potential health consequences of vitamin D deficiency.

14/15 «%»

«essential» amino acids

a. hypertension is high blood pressure 

b. systolic is when the heart is contracting and diastolic is relaxing 

c. systolic pressure higher than 120/130/140 «mmHg in an adult» 

d. diastolic pressure higher than 80/90 «mmHg in an adult»

For answers c. and d. the units are not required.

Accept 12/13/14 for systolic and 8/9 for diastolic as this is how it is expressed in many countries.

a. poor bone mineralization 

b. rickets/osteoporosis/osteomalacia 

c. poor absorption of dietary calcium

Allow for other verifiable answers.

The liver receives blood from the digestive system via the hepatic portal vein as shown.

Compare and contrast the composition of the blood in the hepatic portal vein with the composition of the blood in the hepatic vein.

Outline how the liver recycles the components of red blood cells.

Compare:

a. both HPV and HV deoxygenated blood
OR
both have high levels of CO₂ 

Contrast:

b. HPV blood richer in nutrients/glucose/amino acids than HV
OR
HV blood lower levels of some toxins
OR
HV blood has higher levels of urea/cholesterol/fatty acids/glycerol/Fe²⁺

Accept converse.

One comparison and one contrast for two marks. 

a. Kupffer cells engulf ruptured red blood cells by phagocytosis 

b. hemoglobin is broken down into component molecules 

c. some iron (from hemoglobin) transported to bone marrow/stored in liver 

d. protein component of hemoglobin converted to amino acids 

e. rest of heme component forms bile pigments

State the relationship between pressure and volume in the left ventricle.

Explain the events that cause the sound shown on the phonocardiogram at the start of systole.

Outline reasons for fitting an artificial cardiac pacemaker.

as pressure increases volume decreases

OR

inverse correlation

Accept reverse argument

Do not accept “inversely proportional”

a. when the ventricle contracts blood presses/pressure acts on the AV valve

b. this closes the AV valve «which causes the sound»

The valve must be identified as the AV or atrioventricular valve

a. required when rate of heartbeat/heart contraction is too slow/irregular

b. produces electrical impulse that stimulates heartbeat/heart contraction

c. needed when SA node is defective

Accept “regulate the heartbeat” for marking point a

[Max 2 Marks]

State two roles of hydrochloric acid in gastric juice.

Role 1:

Role 2:

Pancreatic juice is secreted into the pancreatic duct which carries these secretions to the small intestine.

The hormone secretin is released by the small intestine when hydrochloric acid enters it from the stomach. The data below show the volume of pancreatic juice released after an injection of secretin.

Pancreatic secretions contain sodium hydrogen carbonate, making them basic.

Deduce the significance of the response by the pancreas to secretin.

State one cause of stomach ulcers.

a. activation of enzymes/protease/pepsinogen 

b. bactericidal action / kills pathogens 

c. hydrolysis / breakdown of food

a. secretin stimulates an increase in pancreatic secretions 

b. pancreatic secretions are released rapidly / within 10 minutes 

c. «NaHCO₃ in pancreatic secretions» neutralises stomach acid / HCI 

d. provides optimal conditions for digestion / enzymes «in the small intestine» 

e. by 40 minutes no more hydrochloric acid enters the small intestine

an infection by Helicobacter pylori / H. pylori
OR
overuse of NSAIDs /aspirin / ibuprofen

Compare and contrast the data for the two time periods.

Using the data, evaluate the claim that patients with diabetes have a higher risk of mortality from CHD.

Outline two factors that are related to increased risk of developing CHD.

Compare:

a. all the data has large uncertainty
OR
for both time periods, the largest uncertainty is in the diabetic group
OR
both groups (diabetic and non-diabetic) have greater uncertainty in the
2003–09 time period 

Contrast:

b. higher mortality due to CHD in patients with diabetes in 87–96
OR
higher mortality due to CHD in patients without diabetes in 03–09

One comparison and one contrast for two marks.

Accept converse answers.

a. claim supported for 87–96 data since patients without diabetes have lower mortality rate due to CHD 

b. claim possibly not supported for the 03–09 data since rate of CHD mortality is similar for the two groups 

c. mortality due to CHD in diabetes patients has decreased / mortality for non-diabetics has increased 

d. large variance/error bars/overlapping error bars for 03–09 do not allow firm conclusion 

e. no data on gender/age/obesity, etc.

Accept converse answers.

a. high cholesterol/LDL/transfats/saturated fats (may lead to atherosclerosis) 

b. hypertension/high blood pressure (from stress or medical condition) 

c. obesity / lack of exercise / smoking 

d. genetic predisposition

Explain how materials from red blood cells are recycled by the liver.

State a cause and a consequence of jaundice.

Cause:

Consequence:

a. erythrocytes/red blood cells have a lifespan of approximately 120 days ✔

b. erythrocytes/red blood cells taken in by phagocytosis ✔

c. «phagocytosis» by Kupffer cells ✔

d. hemoglobin splits into globin and heme groups ✔

e. iron removed / recycled✔

f. heme without iron becomes bile pigment/bilirubin ✔

g. globin/protein digested/hydrolysed to amino acids ✔

Cause: Do not accept toxins or alcohol
Hepatitis / liver cancer / cirrhosis / parasite infection / excess production of bile pigments/bilirubin / blocked bile ducts / gall stones ✔

Consequence:
yellowing/discoloration of skin/sclera/white of the eye / dark urine / grey feces / brain damage in infants ✔

Discuss the causes and treatments of phenylketonuria.

Causes:

a. phenylketonuria is an inherited / genetic condition / caused by a mutation 

b. enzyme phenylalanine hydroxylase/PAH not present/deficient 

c. phenylalanine is an essential amino acid 

d. inability to convert phenylalanine into tyrosine / phenylalanine builds up in the body 

Treatment:

e. requires diet rich in tyrosine «supplements» 

f. low in phenylalanine 

g. monitor blood phenylalanine levels 

h. monitor growth rates / intellectual development

Hypochlorhydria is a condition whereby patients produce low quantities of stomach acid. Outline the effect this might have on the normal processes within the stomach.

Explain the mechanisms that regulate the composition of gastric juices.

a. reduced resistance to pathogens ✔

b. pH not optimum for pepsin activity ✔

c. activation of enzymes/pepsinogen is reduced ✔

d. reduced food/protein digestion ✔

a. regulated by both hormonal and nervous systems ✔

b. smell/sight of food causes the brain to send nerve impulses ✔

c. via the «vagus» nerve from the medulla «oblongata» ✔

d. «gland» cells in the stomach wall are stimulated to secrete gastric juice ✔

e. chemoreceptors in the stomach wall detect food «and send an impulse to the brain» ✔

f. stretch receptors detect stretching/distension of the stomach «and send impulses to the brain» ✔

g. release of «hormone» gastrin ✔

h. gastrin stimulates secretion of acid
OR
pepsinogen by exocrine gland cells in the stomach wall ✔

i. secretin and somatostatin inhibit gastrin secretion if the pH in the stomach falls too low ✔

This was often answered in terms of the functions of stomach acid rather than hypochlorydria, however this was not penalised. The effect on pathogens and reduced digestion were most often stated, and activation of enzymes very rarely.

There were few excellent answers to this question, perhaps because the wording of the question led some candidates to discuss composition of digestive juices rather than their control. The medulla and gastrin were often mentioned and occasionally chemo- and stretch receptors. Often a mark was awarded from different sections of the answer, as responses lacked clarity.

State the relationship between BMI and age in men.

Evaluate the data to assess whether a high BMI is a risk factor for the development of diabetes.

positive relationship
OR
increases with age ✔

a. higher BMI is associated with diabetes

b. 50th percentile for diabetes are overweight «at all ages»
OR
50th percentile is a higher BMI for diabetics «at all ages»
OR
50th percentile for diabetes is close to the 75th percentile BMI of the entire population
OR
50th percentile for diabetes is higher than 50% percentile for non-diabetic men ✔

c. chances of diabetes increase with age ✔

d. the graph does not show the information for each individual «just the percentiles» ✔

This question relating BMI to age was relatively straightforward for most candidates.

A few candidates found it hard to use the 50th percentile curve in their answers.

Explain the relationship between infection by the bacterium Vibrio cholerae and dehydration.

Severe dehydration can lead to cardiac arrest. Outline the use of defibrillation to treat life-threatening cardiac conditions.

a. V. cholerae releases toxin 

b. chloride channels activated 

c. chloride ions are pumped out of cells 

d. leading to fluid loss from intestine/diarrhea 

e. associated vomiting contributes to dehydration

a. defibrillator is electrodes / a metal paddle or / a pad that is placed on the patient’s chest 

b. the device determines whether fibrillation is happening 

c. a series of electrical shocks are delivered «through the electrodes» 

d. electrical impulse is used to depolarize the heart muscle 

e. to re-establish the function of the SA node / natural pacemaker / natural rhythm «of the heart»

Discuss the causes and consequences of malnutrition in humans.

Causes:

a. deficiency in an essential nutrient 

b. excess of a nutrient 

c. may be due to social/socioeconomic/political factors 

d. unbalanced diet can result from malfunction of the hypothalamus 

Consequences:

e. starvation can lead to breakdown of body tissues 

f. obesity can lead to other health problems/diabetes/CHD 

g. anorexia can lead to organ failure/serious health problems 

h. consequence of a named excess/deficiency

Maximum 3 marks if both causes and consequences not mentioned.

Identify the blood vessel labelled B.

Outline the function of the blood vessel labelled B.

Distinguish between the structure of liver sinusoids and capillaries.

«hepatic» portal vein

a. takes blood from intestine/spleen/pancreas/stomach to liver

b. carries digested food/nutrients/glucose

c. prevents glucose entering the general circulation

d. helps maintain osmotic potential of blood

e. allows toxins to be removed

[Max 3 Marks]

a. sinusoids have open pores/fenestrations/discontinuous endothelium and capillary endothelium is continuous/does not contain fenestrations

b. Kupffer cells are located inside sinusoids but not in capillaries

c. sinusoids larger in diameter than capillaries

Accept labelled diagrams

[Max 2 Marks]

Identify the phagocyte labelled X.

Identify the blood vessel labelled Y which brings blood from the intestines.

Explain the function of hepatocytes in protein metabolism.

Compare and contrast the structure of sinusoids and capillaries.

Kupffer (cell);

(hepatic) portal vein/venule;

“Portal” alone is insufficient

a. they produce/secrete plasma proteins;

b. (the plasma proteins) are modified/secreted by the Golgi apparatus;

c. protein/globin is broken down into amino acids;

a. both have walls 1 cell thick/same thickness
OR
both have a basement membrane;

b. sinusoids have pores/holes/fenestrations
OR
sinusoids have a wider lumen;

Most candidates could identify the Kupffer cell (with a variety of spellings), and the hepatic portal vein.

The function of the hepatocytes in protein metabolism was challenging for most candidates despite this being taken directly from an assessment statement.

Comparison of sinusoids and capillaries produced many vague answers. Many candidates failed to treat the question as a ‘compare and contrast’ question which requires giving similarities and differences. Common errors included referring to blood type carried, cell membrane thickness and the position of the vessels in the body.

State the relationship between gastric acidity and GI damage.

GI damage can include ulcers. Outline the treatment of stomach ulcers.

Other than gastric acidity, state a primary cause of stomach ulcers.

probability of GI damage increases with increased «gastric» acidity

OR

positive correlation

OWTTE

Do not accept “directly proportional”

a. proton pump inhibitors reduce stomach acid «production»

b. antacid/medication to neutralize/decrease acidity

c. «lower acidity» allow GI damage/ulcers to heal

d. antibiotics for H. pylori/bacterial infection

e. diet/lifestyle changes/eliminate smoking/alcohol

f. surgery needed with extensive gastric damage

Accept “cauterization” for marking point f

[Max 3 Marks]

a. Helicobacter pylori/H. pylori «infection»

b. use of non-steroidal anti-inflammatory drugs/NSAID/aspirin/ibuprofen

Accept valid examples of NSAID but do not accept trade names

[Max 1 Mark]

State the name of the blood vessel through which lactate from muscles reaches the liver

Compare and contrast the possible metabolic pathways for lactate in hepatocytes and in mitochondria-rich tissue.

List two functions of hepatocytes other than regulating lactate levels in the blood.

1.

2.

hepatic artery ✔

a. both produce pyruvate «from lactate»
OR
both produce CO₂ and H₂O «via acetyl CoA» ✔

b. hepatocytes produce glucose from lactate but mitochondria-rich cells cannot ✔

OWTTE – eg: “only hepatocytes produce glucose” would be acceptable.

a. detoxification ✔

b. production/secretion of bile ✔

c. conversion of cholesterol to bile salts ✔

d. production of plasma proteins ✔

e. nutrient storage ✔

f. glucose regulation «in blood» ✔

g. other function «eg deamination/transamination, conversion of ammonia to urea» ✔

Only two functions are required.

If more than two functions are given, mark only the first two listed.

The data showed possible metabolic pathways for lactate in humans. In (a) many candidates wrongly answered the hepatic portal vein.

Part (b) and (c) were well answered, the main error was confusing the hepatocytes with the Kupffer cells.

Part (b) and (c) were well answered, the main error was confusing the hepatocytes with the Kupffer cells.

Outline how the data indicate that protein was being used as an energy source.

Outline the reason for such a high percentage reduction in mass of adipose tissue.

Discuss whether the mass losses shown in the bar chart could be due to anorexia nervosa.

loss of skeletal/heart muscle «containing protein» ✔

a. adipose tissue has a high energy value ✔

b. adipose tissue may be lost before affecting body metabolism/homeostasis ✔

c. body will use up adipose reserves first before using muscle and organs for energy ✔

Accept fat for adipose tissue

a. loss of mass similar in anorexia and starvation ✔

b. loss could also be due to disease/feeding difficulties/other disorder/poverty/social unrest ✔

c. lack of food intake in anorexia nervosa due to emotional disorder
OR
desire to lose weight/refusal to eat characteristics of anorexia nervosa ✔

d. loss of «cardiac» muscle is characteristics of anorexia nervosa ✔

List the two blood vessels that supply the sinusoids.

1.

2.

State one feature in the diagram that identifies the structure as a sinusoid.

Excess nutrients absorbed in the intestine can be stored. State one example of a nutrient stored in the liver.

a. hepatic artery ✔ 

b. hepatic portal vein ✔

a. fenestrations/gaps/holes between cells ✔ 

b. walls are one cell thick ✔

iron/glucose/«fat soluble» vitamins/glycogen ✔

The required words “hepatic” and “portal” were often missing.

Most often the fenestrations or equivalent word were described; “thin walls” was insufficient for walls one cell thick. “Cylinder” was often seen.

Glucose, glycogen or iron were the most common answers. “Glucagon” was often mentioned and could not be accepted for glycogen.

Explain a method to quantify the energy content in food.

a. description of apparatus
OR
drawing
OR
measured with a calorimeter

Allow other correct described method.

b. measure the initial mass/volume of water 

c. measure the initial temperature of the water 

d. measure the mass of the food 

e. ignite the food and place under the container of water 

f. measure the final temperature of the water
OR
calculate the change in temperature of the water 

g. heat gained by the water=heat lost by the food
OR
energy=mass of water temperature rise in water x specific heat capacity of water/mass of food

State how many normal heartbeats are shown in the ECGs.

Outline how a defibrillator is used to restore normal heartbeat.

Explain what is occurring in the heart during the peak of electrical activity as indicated by the R wave on the ECG.

8 ✔

a. «paddles/electrodes/defibrillator» deliver an electric shock to the heart ✔

b. depolarizes cardiac muscle ✔

c. enables the pacemaker/SA node to regain control ✔

a. impulses initiated from the AV node spread across heart ✔

b. impulses travel along Purkinje fibres/across ventricles ✔

c. causing depolarization of the ventricles
OR
that triggers ventricular contraction ✔

State the name of the cells that perform the breakdown of erythrocytes in the liver.

Describe the breakdown of erythrocytes by liver cells.

Outline the fate of the iron from the erythrocytes.

Kupffer

a. cells phagocytose/engulf the erythrocytes 

b. hemoglobin is split into heme group and globins
OR
heme is removed from hemoglobin 

c. globins broken down/hydrolyzed to peptides/amino acids 

d. heme group separated into iron and bilirubin

a. carried to bone marrow 

b. used in the production of hemoglobin/new erythrocytes

Describe the structure of cardiac muscle cells.

State the name of the valves that prevent blood flowing from the arteries back into the heart.

Distinguish between the different phases of the cardiac cycle in the atria and in the ventricular muscle.

Sketch the pattern seen in a typical electrocardiogram (ECG) trace for one complete cardiac cycle, including labels of the main features.

a. cardiac muscle cells are branched ✔

b. rich in mitochondria ✔

c. rich in glycogen granules ✔

d. formed by short cylindrical cells ✔

e. contains intercalated discs ✔

f. has gap junctions ✔

g. «intercalated discs are» transverse cross-bands which represent the attachment site between adjacent cells ✔

Do not accept myogenic as it is not a structure.

semilunar / sigmoid / pulmonary and aortic valve ✔

a. action potential of atrium precedes the ventricle
OR
the phases happen later in ventricle
OR
atrium contracts before the ventricle ✔

b. atrium has a shorter phase 2/longer phase 2 in ventricle
OR
atrium falls abruptly in phase 2/ventricle shows a plateau in phase 2 ✔

c. phase 3 is more distinct/falls more abruptly in ventricular action potential ✔

d. ventricular phase is overall longer than atrial phase ✔

a. sketch with the correct shape ✔

b. P, Q, R, S and T indicated ✔

c. atrial contraction/systole/depolarisation labelled ✔

d. ventricular contraction/systole/depolarisation labelled ✔

e. ventricular relaxation/diastole/repolarization labelled ✔

Correct shape should show peaks at P R and T and dips at Q and S

The stronger candidates could describe the structure of cardiac muscle cells.

Most could name the semilunar valves.

Part (c) confused many candidates and they did not realise they had to refer to the graphs in their answers. Most scored one mark for stating ventricular contraction occurs after atrial contraction.

In part (d) the better candidates could sketch the pattern seen in a typical electrocardiogram. Some made errors in the shape or letters but could still achieve marks for showing the areas of contraction or relaxation.

On the cladogram, label with an M, the point at which a mutation occurred, preventing the gibbon from synthesizing ascorbic acid.

Outline the reason for ascorbic acid being described as an essential nutrient in the diet of humans.

A small box of orange juice contains these details on the side of the package:

[Source: © International Baccalaureate Organization 2020.]

Calculate the volume of juice needed to obtain the recommended daily requirement of vitamin C.

. . . . . . . . . . . . . . . . . . .mL

The apparatus used to measure energy content of food contains some water. Explain how this water is used when measuring the energy content of a food.

cannot be synthesized by the body;

250 (mL)

a. the volume/mass of water is measured;

b. the energy from the burning food raises the temperature/heats the water;

c. knowing the specific heat of water allows energy of the food to be calculated
OR
4.2J of heat energy causes a 1°C rise in 1g of water;

Most candidates could label the correct point on the cladogram where a mutation occurred and state the reason ascorbic acid is described as an essential nutrient.

The calculation of how much juice was needed was difficult for many candidates. Common incorrect answers were 160 ml and 240 ml.

Stronger candidates could explain how water is used in a calorimeter. Many candidates suggested burning the food in the water and others answered all they knew about calorimeters without answering the question directly.

The table shows the origin and function of gastric secretions in the digestive system.

Identify the missing items by completing the table.

Explain how Helicobacter pylori can cause stomach ulcers.

Secretion: gastrin;
Function: digest proteins;
Secreting cells: parietal;

If more than one answer do not give the mark unless all are correct.

a. H. pylori weakens/degrades the mucous coating;

b. (this) allows acid to get through to the epithelial layer;

c. the acid damages the stomach wall;

Both parts (a) and (b) were good discriminating questions. Weaker candidates could possibly score one mark from three for completion of the table and explaining that acid damages the stomach walls. Weaker candidates said that Helicobacter pylori increased HCl production or attacked the stomach wall.

State one mechanism that controls gastric secretion.

State the type of gland that secretes juices into the digestive system.

State where this type of cell can be found in the digestive system. 

Outline two adaptations of this cell to its function that are visible in this electron micrograph.

sight/smell of food
OR
negative/positive feedback
OR
nervous control/vagus/parasympathetic nerve stimulation
OR
hormonal control / gastrin / secretin / somatostatin ✔

exocrine ✔

Do not accept name of specific digestive gland.

small intestine/duodenum/ileum/jejunum ✔ 

Villi alone not acceptable. Accept intestinal villi.

a. microvilli increase the surface area for absorption ✔ Each adaptation needs function stated. Do not accept villi, microvilli is required.

b. many mitochondria produce ATP/energy «for active transport» ✔

c. vesicles resulting from endocytosis ✔

Using the letters provided, identify the parts of the ECG where the ventricle muscles are contracting.

State what is represented by the period between the points R and R’.

Outline the use of artificial pacemakers for patients with a heart condition.

QRS/ Q to S

one cardiac cycle

a. artificial pacemakers deliver electrical impulses «to heart muscle» 

b. they maintain a regular heart rate / supplement the natural pacemaker 

c. they sense missing heart beats and stimulate the heart
OR
correct malfunction of SAN / sinoatrial node 

d. they coordinate contractions of atria and ventricles / left and right atria

On the diagram, label the epithelial cell layer.

Explain how the epithelial cells are adapted for absorption.

arrow pointing at an epithelial cell ✔

Accept a bracket label to show the epithelium epithelial cell layer

a. microvilli/brush border to increase surface area ✔

b. numerous mitochondria for energy for active transport ✔

c. have transport proteins for specific nutrients ✔

d. single layer of cells/short distance allowing for diffusion ✔

Explanation must be included for each characteristic eg: “glucose, amino acids”

The diagram below shows the liver and main vessels associated with it.

Suggest advantages of the blood supply from the pancreas passing directly into the liver.

a. the liver can respond quickly to hormones made by the pancreas 

b. the pancreas secretes insulin / glucagon into the blood «traveling directly to the liver» 

c. «the hormones released by the pancreas» stimulate the liver to store / release glucose 

d. allows rapid regulation of blood glucose levels

Using the data, discuss the implications for the advice given by dieticians to patients.

Describe how the energy content of food may be measured by combustion.

State one material not produced by the human body that is egested from the digestive system.

a. increasing the mass of almonds eaten increases the energy content of feces ✔

b. some of the energy consumed in foods may not be absorbed/is lost/egested in feces ✔

c. can’t draw conclusions as the data is incomplete ✔

a. A calorimeter/calorimetry is used ✔

b. food is burned/heated/combusted to release energy/heat ✔

c. the energy/heat is used to heat up water ✔

d. the rise in temperature of the water allows the energy in the food to be calculated ✔

e. energy from the food = specific heat capacity of water x mass of water x temperature rise ✔ Accept alternative correct formula

cellulose/lignin/fibre ✔

Explain the stages involved in the recycling of erythrocytes by the liver.

a. phagocytosis of erythrocytes by Kupffer cells 

b. hemoglobin is split into globin and heme group 

c. globin is hydrolysed to amino acids 

d. amino acids used in protein synthesis 

e. heme group broken down into iron and bilirubin 

f. iron is (carried back to the bone marrow to be) used for production of new erythrocytes 

g. bilirubin is secreted into bile 

In b. both globin and heme required.

In e. both iron and bilirubin required.

Outline the reasons that the female patients with anorexia nervosa have a lower mean ventricle mass than healthy females.

Suggest a reason for the difference in QT interval between females with anorexia nervosa and healthy females.

State the two causes of normal heart sounds.

a. patients with anorexia nervosa do not eat sufficient food/protein/amino acids.  Starving = insufficient food

b. heart muscles used as an energy source

c. reduced body mass reduces requirement for muscle mass in ventricle

decreased left ventricle mass/pressure therefore more time needed to contract

atriaventricular/AV valve closing and semilunar/SV valves closing

Both valves need to be addressed for the mark.

Outline the importance of the proton pumps in the digestion of foods.

Explain the use of proton pump inhibitors to treat patients complaining of stomach pain.

a. pumps protons/H⁺ into the stomach 

b. allows for the production of «hydrochloric» acid 

c. «hydrochloric» acid accelerates digestion/activates enzymes 

d. gives optimal pH for pepsin/enzyme digestion

a. proton pump is a «transmembrane» protein 

b. proton pump inhibitors bind to the proton pump 

c. hydrogen ions are not sent into stomach lumen 
OR 
reduction of «gastric» acid production 

d. increase in pH of stomach 

e. relieve symptoms of acid reflux/gastritis/ulcers

The bar chart indicates that both males and females in the US eat, on average, less fibre than is recommended.

Explain the importance of dietary fibre.

a. ensure correct transit rate / movement of food through the intestines 

b. avoid constipation / difficulty in empty bowels / difficulty in egestion 

c. correct levels of water reabsorbed 

d. avoid overlong exposure to fat soluble chemicals 

e. decreased risk of colon cancer/hemorrhoids/appendicitis 

f. decreases the rate of absorption of glucose 

g. decreases hunger so less obesity/diabetes

The cell labelled X is only found in the liver and is associated with the wall of a sinusoid.

(i) Identify cell X.

(ii) Outline the function of cell X.
 

Explain the importance of bilirubin in the onset of jaundice.

(i) Kupffer cell

(ii)

a. they are macrophages/phagocytes

b. break down red blood cells

c. separates heme (group) from (protein) globin chain

There is no ECF here.

a. «jaundice is» a yellowish pigmentation of the skin/whites of eyes

b. caused by high levels of bilirubin in blood/tissues

Simply stating “caused by high levels of bilirubin” is not enough for marking point b. However “tissues” may be implied as part of the answer to marking point a.

c. comes from breakdown of red blood cells

d. results from the breakdown of the heme group of hemoglobin

e. released into blood when excess is produced

f. released into blood when bile ducts blocked

g. normally excreted with bile

h. jaundice is often seen in liver disease such as hepatitis/liver cancer/chronic alcoholism/cirrhosis
OR
newborn/neonatal jaundice «due to immature liver»