IB DP Physics Option D: Human physiology (Core topics) :D.3 Functions of the liver HL Paper 3

Date	November 2017	Marks available	2	Reference code	17N.3.HL.TZ0.21
Level	Higher level	Paper	Paper 3	Time zone	TZ0
Command term	Distinguish	Question number	21	Adapted from	N/A

Question

Jaundice causes a yellow discolouration of the skin, mucous membranes and sclera of the eyes. State the bile pigment causing this discolouration.

[1]

a.i.

Explain how the normal production of bile pigments changes with the development of jaundice.

[4]

a.ii.

Distinguish between the structure of liver sinusoids and capillaries.

[2]

Markscheme

bilirubin

a.i.

normal production: [2 max]

a. red blood cells/erythrocytes/hemoglobin broken down «in the liver»

b. hemoglobin/heme «from red blood cells» is converted to bilirubin/bile pigment

c. bilirubin/bile pigment transferred to bile and «normally» eliminated in the feces

change with jaundice:

d. «in jaundice» liver does not excrete/eliminate bilirubin/bile pigments

e. caused by immaturity/dysfunction/disease «of the liver»

blockage of bile ducts

increase in red blood cells breakdown

f. therefore bilirubin/bile pigment accumulates in the blood

[Max 4 Marks]

a.ii.

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/wider than capillaries

[Max 2 Marks]

Date	May 2017	Marks available	6	Reference code	17M.3.HL.TZ1.22
Level	Higher level	Paper	Paper 3	Time zone	Time zone 1
Command term	Explain	Question number	22	Adapted from	N/A

Question

Explain the process of erythrocyte and hemoglobin breakdown in the liver.

Markscheme

a. erythrocytes rupture when they reach the end of their life span / after 120 days

b. «erythrocytes» absorbed by phagocytosis

c. Kupffer cells ingest/take in erythrocytes

d. Kupffer cells in sinusoids in the liver

e. hemoglobin split into globin and heme groups

f. amino acids from the globin are recycled

g. heme group is further broken down into iron and bilirubin / bile pigment

h. iron stored in liver / transported to bone marrow/spleen

i. bilirubin released into alimentary canal/becomes part of bile

Date	May 2017	Marks available	2	Reference code	17M.3.HL.TZ1.21
Level	Higher level	Paper	Paper 3	Time zone	Time zone 1
Command term	Explain	Question number	21	Adapted from	N/A

Question

The graph below shows the oxygen dissociation curve at a low CO2 concentration.

Outline the main changes in the lungs that occur in patients with emphysema.

[2]

a.i.

State a treatment for emphysema.

[1]

a.ii.

An increase in metabolic activity results in greater release of CO2 into the blood. On the graph, draw the oxygen dissociation curve during intense exercise when the CO2 concentration of the blood is high.

[1]

b.i.

Explain how the increase in CO2 concentration affects the release of oxygen to respiring cells.

[2]

b.ii.

Markscheme

a. air sacs/alveoli break down/rupture

b. creating one larger air space instead of many small ones / reduces the surface area of the lungs

c. loss of elasticity of lung tissue

a.i.

supplemental oxygen / breathing techniques / bronchodilators / inhaled steroids / lung surgery to remove damaged tissue / lung transplant

a.ii.

curve has to be towards the right and starting together

Must start together but can finish slightly below the original curve.

b.i.

a. increased levels of CO2 lower the pH of the blood

b. «which results in» decreased affinity of the hemoglobin for oxygen / greater release of oxygen

c. this shifts the oxygen dissociation curve to the right/Bohr shift

b.ii.

Date	November 2016	Marks available	6	Reference code	16N.3.HL.TZ0.23
Level	Higher level	Paper	Paper 3	Time zone	TZ0
Command term	Explain	Question number	23	Adapted from	N/A

Question

Explain, using an oxygen dissociation curve, how hemoglobin supplies oxygen to respiring tissues and how the Bohr shift increases the supply.

Markscheme

How hemoglobin supplies oxygen to respiring tissues

a. properly labelled axes showing % saturation hemoglobin and partial pressure of oxygen

b. correct/sigmoid shape of «normal» oxygen dissociation curve

Do not accept concave curves. Curve should start at origin.

c. tissues use O2 for «cellular» respiration thus lowering pO2 at tissue level
OR
respiring tissues produce CO2

d. O2 dissociates more at lower pO2 from Hb «than at higher pO2» thus providing O2 to «respiring» tissues/OWTTE

How Bohr shift increases the supply

e. CO2 is converted to hydrogen carbonate ions/HCO3− and H+

f. increase in H+ lowers blood pH

g. H+ combines with Hb / conformational change in Hb «in red blood cell» freeing some O2

h. shifts the oxygen dissociation curve to the right «Bohr shift»
OR
shift to the right shown on diagram labelled Bohr shift

i. oxygen dissociation curve steeper at lower pO2 «corresponding to respiring tissues»

j. lowers the affinity of hemoglobin for oxygen

k. means less oxygen can be carried for same pO2 «as normal»
OR
«even» more oxygen available for respiring tissues for same pO2

Accept any of the marking points in a clearly annotated diagram. Values not required.

Date	November 2016	Marks available	3	Reference code	16N.3.HL.TZ0.21
Level	Higher level	Paper	Paper 3	Time zone	TZ0
Command term	Describe	Question number	21	Adapted from	N/A

Question

Describe how the liver regulates nutrient levels.

Markscheme

a. storage of glucose as glycogen
OR
breakdown of glycogen to glucose

Do not accept “sugar”.

b. deamination/breakdown of «excess» amino acids

c. storage/recycling of iron/copper

d. produces/eliminates cholesterol «as necessary»

e. storage of vitamin A/vitamin D/vitamin B12/vitamin K

Date	May 2016	Marks available	6	Reference code	16M.3.HL.TZ0.22
Level	Higher level	Paper	Paper 3	Time zone	TZ0
Command term	Outline	Question number	22	Adapted from	N/A

Question

Outline the ways in which the liver regulates the chemical and cellular composition of the blood.

Markscheme

Stores glucose as glycogen
OR
Releases glucose from glycogen

Under influence of insulin/glucagon «respectively» depending on blood glucose levels

Some nutrients in excess can be stored in the liver (Accept vitamin A or D stored)

The liver detoxifies blood
OR
The liver removes/breaks down toxins/alcohol/drugs «from the blood»

Kupffer cells engulf bacteria

Kupffer cells breakdown erythrocytes/red blood cells/hemoglobin by phagocytosis

Hemoglobin is split into heme and globin

Iron from heme/hemoglobin breakdown is carried to the bone marrow «to produce new hemoglobin in new red blood cells»
OR
Excess iron stored in liver

Surplus cholesterol is converted to bile salts
OR
Cholesterol is synthesized

«Hepatocytes» produce plasma proteins (Accept specific plasma proteins such as albumin)

Date	May 2015	Marks available	1	Reference code	15M.3.HL.TZ1.14
Level	Higher level	Paper	Paper 3	Time zone	Time zone 1
Command term	State	Question number	14	Adapted from	N/A

Question

State one mechanism the ileum uses to absorb digested food into the bloodstream.

[1]

a (i).

State the role of the hepatic portal vein.

[1]

a (ii).

Label the line that represents the ventricle.

[1]

b (i).

Estimate the total time the atrioventricular valves are open.

[1]

b (ii).

Although some CO2 entering the blood simply dissolves in the plasma, most enters the erythrocytes (red blood cells).

Outline how CO2 interacts with hemoglobin once it enters erythrocytes.

[1]

c (i).

Describe the formation of HCO3– in erythrocytes.

[2]

c (ii).

Markscheme

active transport/facilitated diffusion/endocytosis

a (i).

transports blood from (capillaries of) small intestine to (capillaries/sinusoids of) liver

a (ii).

label should connect to solid line on graph.
Candidates should not use region with overlap of dotted and solid lines.

b (i).

0.4 (s) (allow 0.38 to 0.43)

b (ii).

CO2 attaches to protein portion (not Fe) in heme/carbaminohemoglobin formed;

c (i).

a. CO2 diffuses into erythrocytes;
b. joins water to form carbonic acid/H2CO3;
c. catalyzed by carbonic anhydrase (inside erythrocytes);
d. H2CO3 dissociates into H+ and HCO3–;

c (ii).

Date	May 2015	Marks available	6	Reference code	15M.3.HL.TZ2.15
Level	Higher level	Paper	Paper 3	Time zone	Time zone 2
Command term	Describe	Question number	15	Adapted from	N/A

Question

Describe how the liver helps to maintain human health.

Markscheme

a. helps regulate blood glucose level / converts glucose to glycogen and back;
b. prevents excess glucose that could damage cells / lack of glucose could limit cell growth/activity / OWTTE;
c. stores/recycles iron;
d. stores vitamin A/vitamin D;
e. synthesizes plasma proteins/cholesterol;
f. provides essential substances for cell growth/hormone production;
g. detoxifies substances / protects the body from damage from toxic substances (as alcohol);
h. breaks down erythrocytes/hemoglobin;
i. production of bile for digestion (of fats);
j. (production of bile) reduces build-up of bilirubin in the blood / prevents jaundice;

Date	November 2015	Marks available	6	Reference code	15N.3.HL.TZ0.15
Level	Higher level	Paper	Paper 3	Time zone	TZ0
Command term	Explain	Question number	15	Adapted from	N/A

Question

Explain the role of the liver in regulating and storing nutrients.

Markscheme

a. all nutrients arrive at the liver (from small intestine) via hepatic portal vein;

b. liver stores (excess) glucose as glycogen and releases it as needed / OWTTE;

c. process is (respectively) under the control of insulin/glucagon;

d. (glucose levels) controlled by negative feedback;

e. amino acids are deaminated in the liver;

f. liver produces plasma proteins/albumin/fibrinogen;

g. synthesizes/stores cholesterol;

h. liver stores iron from the breakdown of hemoglobin in red blood cells;

i. liver stores vitamin A/vitamin D;

Date	May 2013	Marks available	6	Reference code	13M.3.HL.TZ1.14
Level	Higher level	Paper	Paper 3	Time zone	Time zone 1
Command term	Outline	Question number	14	Adapted from	N/A

Question

The liver is a complex organ with a wide range of functions. Outline the functions of the liver.

Markscheme

a. produces bile for digestion/emulsification of fats/lipids;
b. regulates blood glucose level through glucose-glycogen reaction;
c. detoxification/example of detoxification (eg contains catalase for the breakdown of hydrogen peroxide);
d. manufactures plasma proteins/albumins/fibrinogen;
e. manufactures cholesterol;
f. destroys red blood cells by phagocytosis;
g. breaks down haemoglobin from red blood cells;
h. stores iron;
i. stores vitamin A and D;
j. deaminates excess amino acids/formation of urea;

Date	May 2013	Marks available	1	Reference code	13M.3.HL.TZ2.14
Level	Higher level	Paper	Paper 3	Time zone	Time zone 2
Command term	Outline	Question number	14	Adapted from	N/A

Question

Outline how bile helps in lipid digestion.

[1]

Describe how bile pigment is formed.

[3]

Markscheme

bile emulsifies/OWTTE lipids so enzymes can act on them

a. hemoglobin from the red blood cells is absorbed/phagocytosed in the liver/by Kuppfer cells;
b. hemoglobin is broken down into heme and globin groups;
c. iron is removed from the heme groups;
d. (residue from) heme becomes bilirubin/bile pigment (in hepatocytes);

Date	May 2011	Marks available	2	Reference code	11M.3.HL.TZ1.14
Level	Higher level	Paper	Paper 3	Time zone	Time zone 1
Command term	Describe	Question number	14	Adapted from	N/A

Question

The oxygen dissociation curve is a graph that shows the percentage saturation of hemoglobin at various partial pressures of oxygen. Curve A shows the dissociation at a pH of 7 and curve B shows the dissociation at a different pH.

Outline how coronary thrombosis can be caused.

[2]

State the possible cause of the curve shifting from A to B.

[1]

b (i).

On the graph, draw the curve for myoglobin.

[2]

b (ii).

Describe the breakdown of hemoglobin in the liver.

[2]

Markscheme

atheroma/fatty deposits in arteries;
hardening of arteries/atherosclerosis/arteriosclerosis;
rough surface causes rupture of platelets;
clots form in coronary artery;

increase in CO2 concentration;
decrease in pH;

b (i).

graph drawn to left of A;
curve not sigmoid;
As shown below.

b (ii).

hemoglobin absorbed by phagocytes/Kupffer cells;
split into heme and globins;
globin hydrolysed/broken down to amino acids;
iron removed from heme group / heme broken down to form bilirubin/bile pigment;

Date	May 2012	Marks available	2	Reference code	12M.3.HL.TZ1.14
Level	Higher level	Paper	Paper 3	Time zone	Time zone 1
Command term	State	Question number	14	Adapted from	N/A

Question

In healthy adults, there are heart sounds during the cardiac cycle. Outline the causes of two of these sounds.

[2]

State two products resulting from the breakdown of erythrocytes (red blood cells) in the liver.

1. …………………………………………………………

2. …………………………………………………………

[2]

Compare gastric juice and pancreatic juice.

[3]

List one material that is egested after human digestion.

[1]

Markscheme

changing pressure of blood in heart automatically opens and closes the valves / the closing of valves generates the heart sounds;
first heart sound (S1) is produced by the closing of the AV valves/mitral and tricuspid valves;
second heart sound (S2) produced by the closing of semilunar valves/aortic and pulmonary valves;

iron;
bile pigments/bilirubin;
globin/amino acids;

Award [1] for each correct row.

cellulose / lignin / bile pigments / intestinal cells / bacteria

Date	May 2012	Marks available	1	Reference code	12M.3.HL.TZ2.13
Level	Higher level	Paper	Paper 3	Time zone	Time zone 2
Command term	State	Question number	13	Adapted from	N/A

Question

In patients with coronary heart failure (CHF), the presence of anemia can increase the risk of mortality. Anemia is a shortage of red blood cells or a reduced concentration of hemoglobin in the blood. Hepcidin is a peptide that is synthesized in the liver to suppress iron absorption in the intestine. The blood hepcidin concentration in CHF patients with anemia and without anemia was measured. The control group did not have cardiac disease or anemia.

State which group has the greatest range of blood hepcidin concentration.

[1]

Calculate the difference in median blood hepcidin concentration for CHF patients with anemia and without anemia, giving the units.

[1]

Using the data, deduce whether the incidence of CHF or the incidence of anemia has a greater effect on the blood hepcidin concentration.

[3]

Iron is necessary for hemoglobin to carry oxygen so low iron levels cause low levels of hemoglobin. Suggest reasons for the levels of hepcidin found in CHF patients with anemia.

[2]

Markscheme

CHF without anemia

9 ng cm–3 (calculation not required, accept answers in the range of 8.5 ng cm–3 to 9.2 ng cm–3)

median of CHF without anemia greater than median of CHF with anemia;
median of CHF without anemia similar to median of control;
median of CHF with anemia lower than median of control;
anemia (with CHF) appears to be more significant than CHF (without anemia) in affecting hepcidin concentrations;
difficult to determine as overlaps of ranges/population sizes not given/no control with anemia;

low hepcidin levels in CHF patients with anemia;
low hepcidin allows more iron intake/absorption;
more iron allows more hemoglobin so less anemia / low iron leads to anemia;
low iron levels exert negative feedback on hepcidin production;

Date	November 2011	Marks available	2	Reference code	11N.3.HL.TZ0.14
Level	Higher level	Paper	Paper 3	Time zone	TZ0
Command term	Explain	Question number	14	Adapted from	N/A

Question

The diagram below shows a section through the ileum.

Outline two important structural features of cell X.

[2]

a (ii).

Explain the role of bile in lipid digestion.

[2]

Explain why trypsin is initially synthesized as an inactive precursor and how it is activated.

[3]

Markscheme

microvilli/brush border to increase surface area;
enzymes (peptidases and disaccharase) bound to membranes (of microvilli) to complete hydrolysis/digestion;
tight junctions separate fluid of intestinal lumen from intercellular fluid/ impermeable barrier;
large number of mitochondria as high energy demand for active transport;
pinocytotic vesicles formed by endocytosis/uptake of fluid with products of digestion;

a (ii).

bile contains bile salts (and pigments);
bile salt molecules have both a hydrophilic and hydrophobic end;
reduces size of fat/lipid globules / emulsifies fats;
causes increase in total surface area so acted on more effectively by enzyme (lipase);

trypsin is protein-digesting enzyme/protease;
trypsinogen is inactive form produced by pancreas;
produced in inactive form to prevent it digesting cells of pancreas;
converted to active form trypsin in small intestine by enterokinase/ enteropeptidase;
enterokinase/enteropeptidase secreted by intestinal mucosa/wall of small intestine;

Date	November 2012	Marks available	6	Reference code	12N.3.HL.TZ0.15
Level	Higher level	Paper	Paper 3	Time zone	TZ0
Command term	Explain	Question number	15	Adapted from	N/A

Question

Explain how the liver stores and regulates levels of nutrients in the body, including details of the circulation of blood through the liver in your answer. You may use a diagram to illustrate your answer.

Markscheme

(circulation of blood through liver tissues – accept properly annotated diagram)
hepatic artery brings oxygenated blood;
hepatic portal vein brings nutrients (from small intestine);
merge to form sinusoids where liver cells/hepatocytes store and regulate nutrients;
blood leaves through hepatic vein;

(storage and regulation of nutrients)

one named stored nutrient; (e.g. carbohydrates/glycogen / iron / vitamin A/retinol / vitamin D/calciferol)
(award [1 max] for naming nutrients)

hepatocytes regulate blood sugar level by storing glucose as glycogen / releasing glucose from breakdown of glycogen (facilitated by arrival from portal vein);
under influence of insulin/glucagon (respectively) (carried by hepatic artery);
blood lipids/cholesterol synthesized/broken down if required / secreted through bile;
iron stored from breakdown of hemoglobin/released when Po2 is low;

Date	November 2009	Marks available	3	Reference code	09N.3.HL.TZ0.14
Level	Higher level	Paper	Paper 3	Time zone	TZ0
Command term	Outline	Question number	14	Adapted from	N/A

Question

The electron micrograph below shows cells from the intestine.

In the electron micrograph above, state the name of the

(i) structure labelled X.

(ii) type of cells labelled Y.

[2]

Define hormone.

[2]

Outline the circulation of blood through liver tissue.

[3]

Markscheme

(i) microvilli/microvillus

(ii) epithelial cell/enterocyte

chemical (messengers) secreted by (endocrine) glands;

into the blood / transported by the blood;

act on target organs/cells;

hepatic artery carries oxygenated blood;

hepatic portal vein carries blood from gut/deoxygenated blood;

blood from hepatic portal vein and hepatic artery mix;

flows through sinusoids;

hepatic vein carries blood away from liver;

Date	November 2010	Marks available	3	Reference code	10N.3.HL.TZ0.14
Level	Higher level	Paper	Paper 3	Time zone	TZ0
Command term	Label	Question number	14	Adapted from	N/A

Question

Label the section of healthy liver tissue below.

II.

III.

[3]

Outline two roles of the liver.

[2]

List two materials that are not absorbed but are egested by the body.

[1]

State an example of a protein hormone.

[1]

Markscheme

I. hepatic cells / hepatocytes / liver cells / liver tissue;

II. hepatic vein / blood cells;

III. sinusoids;

a. storage of nutrients;

b. detoxification of poisons;

c. breakdown of hemoglobin;

d. production of bile pigments;

e. synthesis of plasma proteins;

f. synthesis of cholesterol;

Award [1] for two of the following.

cellulose / lignin / bile pigments / bacteria / intestinal cells

Do not accept fibre.

insulin / glucagon / prolactin / somatotrophin

Award other suitable examples.