IB Biology HL C1.2 Cell Respiration Questions

Practise IB Biology HL C1.2 with pathway diagrams and data questions covering glycolysis, link reaction, Krebs cycle, chemiosmosis, anaerobic respiration and ATP yield.

Exam points

Explain ATP energy transfer through hydrolysis and regeneration, linking ATP production to cellular work.
Define cellular respiration and relate oxygen, carbon dioxide and ATP across its stages.
Compare human aerobic and anaerobic respiration using lactate, oxygen debt and exercise data.
Interpret variables and design rate experiments affecting respiration.
Explain NAD/NADH and glycolysis ATP investment, payoff and reduced NAD.
Compare lactate formation in humans with yeast fermentation, explaining NAD regeneration and limited ATP.
Explain the link reaction, acetyl-CoA formation and mitochondrial location.
Trace Krebs-cycle location, reactions, carriers and carbon dioxide release.
Trace the ETC, proton pumping, chemiosmosis and ATP synthase in oxidative phosphorylation.
Explain oxygen as the terminal electron acceptor and account for water formation.
Compare lipids and carbohydrates as respiratory substrates.

Covered syllabus points

C1.2.1—ATP distributes energy C1.2.2—Life processes using ATP C1.2.3—ATP ↔ ADP interconversions C1.2.4—Cell respiration system C1.2.5—Anaerobic vs. aerobic respiration in humans C1.2.6—Variables affecting rate C1.2.7 (HL)—NAD as hydrogen carrier C1.2.8 (HL)—Glycolysis C1.2.9 (HL)—Pyruvate → lactate C1.2.10 (HL)—Anaerobic respiration in yeast C1.2.11 (HL)—Link reaction C1.2.12 (HL)—Krebs cycle C1.2.13 (HL)—Electron transport chain C1.2.14 (HL)—Proton gradient generation C1.2.15 (HL)—Chemiosmosis C1.2.16 (HL)—Oxygen as terminal electron acceptor C1.2.17 (HL)—Lipids vs. carbohydrates as substrates

[Maximum number: 3]

All cells require a supply of energy and can transform the energy that they obtain in different ways.

Explain the properties of ATP that make it useful for distributing energy within cells.

[Maximum number: 5]

Monosaccharides can be used to make polysaccharides, and can also be combined with other types of carbon compound to form molecules such as nucleotides.

Outline, with examples, the wide range of uses of adenosine triphosphate (ATP) in cells.

[Maximum number: 1]

Which reaction does not cause a net release of energy?

ADP combines with inorganic phosphate to form ATP

ATP releases inorganic phosphate to form ADP

Loss of hydrogen from reduced NAD

Oxidation of reduced FAD

[Maximum number: 1]

What occurs during the stages of respiration?

Stage of respiration

Decarboxylation

Reduced NAD produced

Glycolysis

Link reaction

Yes

Krebs cycle

Yes

Electron transport chain

Yes

[Maximum number: 5]

Distinguish between aerobic and anaerobic respiration.

cell respiration is the controlled release of energy from organic compounds to form ATP;

aerobic	anaerobic
requires $\mathrm{O}_{2}$	does not require $\mathrm{O}_{2}$ ;
in (cytoplasm and) mitochondrion	in cytoplasm;
$\mathrm{O}_{2}$ reduced	pyruvate reduced;
high yield of ATP	low yield of ATP;
high yield of NADH $\left(+\mathrm{H}^{+}\right) /$ FADH ${ }_{2}$ produced	low/er yield of NADH $\left(+\mathrm{H}^{+}\right)$ / no $\mathrm{FADH}_{2}$ ;
end products $\mathrm{CO}_{2}$ and $\mathrm{H}_{2} \mathrm{O}$	end products ethanol and $\mathrm{CO}_{2}$ (yeast/plants) / lactate (animals/humans);
can use fats/proteins (or sugars)	can only use sugars;
involves oxidative phosphorylation/electron transport chain	does not involve oxidative phosphorylation/electron transport chain;
involves Krebs cycle	does not involve Krebs cycle;

[Maximum number: 1]

Proteasomes are a group of proteins that destroy unwanted proteins in the cell, thereby maintaining cell health. However, chemical inhibitors can block the action of proteasomes, resulting in a build up of unwanted proteins with negative consequences for the cell.

Rat heart cells were incubated at different concentrations of a proteasome inhibitor in order to test its toxicity. The bar graph shows the percentage survival of these cells compared to untreated control cells.

Anticancer Therapeutic Agent Bortezomib', with permission from Elsevier.]

Describe the effect of the two treatments with proteasome inhibitor on mean oxygen consumption.

[Maximum number: 2]

Succinate is industrially produced by continuous fermentation. It is used as a raw material in the production of flavour enhancers, drugs and industrial chemicals. One method of increasing the production of succinate is to genetically modify E. coli to express high levels of formate dehydrogenase (FDH1). This results in the production of higher concentrations of NADH. The engineered pathway is shown as a bold dotted line in the image.

(a)

Using the diagram, suggest a reason for high concentrations of NADH favouring the production of succinate.

[ 1 ]

(b)

Predict one metabolite other than succinate that will be produced in greater amounts if the amount of NADH available is increased.

[ 1 ]

a	lactate/ethanol
b	$\mathrm{CO}_{2}$ «favoured by high FDH1 levels»

[Maximum number: 3]

Glucose is converted to pyruvate during the glycolysis stage of respiration.

(a)

On the diagram, label

[ 2 ]

(i)

with P where phosphorylation occurs.

[ 1 ]

(ii)

On the diagram, label with O where oxidation occurs.

[ 1 ]

(b)

State where in the cell glycolysis takes place.

[ 1 ]

[Maximum number: 2]

Glucose is converted to pyruvate during the glycolysis stage of respiration.

Outline how NAD is made available for glycolysis during anaerobic respiration in animal cells.

[Maximum number: 1]

Bread dough is made by mixing flour, water and yeast. If the dough is then kept at about $30^{\circ} \mathrm{C}$ , it expands.

What is the main reason for choosing this temperature?

Carbon dioxide expands at this temperature.

This is the optimum temperature for the enzymes used in aerobic cell respiration.

Lactate produced by anaerobic cell respiration causes the release of carbon dioxide at this temperature.

At this temperature, yeast produces carbon dioxide rapidly by anaerobic cell respiration.

[Maximum number: 1]

Where in the mitochondrion does the formation of acetyl CoA occur?

[Maximum number: 8]

Explain the processes involved in the Krebs cycle.

Krebs cycle only occurs in aerobic conditions;
the Krebs cycle occurs in the mitochondria;
acetyl CoA from the link reaction releases an acetyl group;
$\mathrm{NADH}+\mathrm{H}^{+}$ and $\mathrm{CO}_{2}$ are formed (with each decarboxylation);
decarboxylation/removal of $\mathrm{CO}_{2}$ involves oxidation/oxidative decarboxylation;
and the release of energy;
acetyl group is joined to a 4-carbon molecule/ $\mathrm{C}_{4} /$ oxaloacetate to form a 6-carbon molecule/citrate;
(decarboxylation changes citrate) to 5-carbon molecule/ $\mathrm{C}_{5}$ ;
(decarboxylation changes glutamate) to a 4-carbon molecule/ $\mathrm{C}_{4}$ ;
then converted into the original 4-carbon molecule/ $\mathrm{C}_{4} /$ oxaloacetate and the cycle repeats;
one (molecule) of ATP is made during this step;
reduced H-carriers/ NADH and FADH2 and carbon dioxide are end-products of Krebs cycle;

[Maximum number: 7]

Explain the role of the electron transport chain in the generation of ATP by cell respiration.

[Maximum number: 1]

Where are protons pumped, to allow chemiosmosis in aerobic respiration to occur?

From outside the mitochondrion through the double membranes

From carrier to carrier in the inner mitochondrial membrane

From the matrix of the mitochondrion to the space between the membranes

From the space between the membranes to the cytoplasm outside the mitochondrion

[Maximum number: 4]

The electron micrograph shows part of a cell including a mitochondrion.

Explain how ATP is generated in mitochondria by chemiosmosis.

[Maximum number: 5]

Describe the role of oxygen in aerobic cell respiration.

a. terminal/final electron acceptor

b. at the end of electron transport chain

c. oxygen also accepts protons/hydrogen ions

d. water produced/ $\frac{1}{2}\mathrm{O}_{2} + 2\text{ electrons} + 2\mathrm{H}^{+} \rightarrow \mathrm{H}_{2}\mathrm{O}$

e. helps to maintain proton gradient «across inner mitochondrial membrane by removal of protons from the stroma»

f. oxygen is highly electronegative/electrons strongly attracted to oxygen

g. avoids anaerobic respiration/buildup of lactic acid

h. allows more electrons to be delivered to the electron transport chain

OR allows NAD/FAD to be regenerated/reduced NAD/FAD converted back to NAD/FAD

i. oxygen allows maximum yield of energy «from glucose» allows complete oxidation of glucose/allows fats to be used in respiration

[Maximum number: 2]

A triglyceride is shown.

Displayed triglyceride structure with a three-carbon backbone joined through oxygen-containing links to three long hydrocarbon chains; all tail carbon–carbon bonds are shown as single bonds.

Explain the reason that more energy is released from one gram of triglyceride than from one gram of glucose in respiration.

a. energy released by oxidation reactions;

b. more carbon/hydrogen (per gram) in triglycerides (than glucose)

OR

more C-C/C-H bonds (per gram) in triglycerides (than glucose);

c. triglycerides in less oxidized/more reduced state/ have less oxygen (per gram than glucose);

d. more acetyl CoA formed (per gram) from triglycerides (than glucose)

OR

more $\mathrm{NADH}_{2} /$ reduced NAD (per gram) from triglycerides (than glucose);

Marking guidance:

Allow vice versa in mpb to mpd.

All question bank results loaded

a	NADH is required as a reducing agent/electron donor/hydrogen donor/co-enzyme/limiting factor for the production of succinate
b	high levels of FDH1 produce greater quantities of NADH which is required for conversion of glucose «via intermediates» to succinate

a	NADH transfers electrons to pyruvate OR pyruvate acts as electron acceptor / pyruvate is reduced;
b	(pyruvate) converted to lactate;
c	NADH oxidized/converted to NAD OR NAD available to be reduced/converted to NADH again (in glycolysis);

Covered syllabus points

Question 1

Question 2

Question 3

Question 4

Question 5

Question 6

Question 7

Question (a)

Question (b)

Question 8

Question (a)

Question (i)

Question (ii)

Question (b)

Question 9

Question 10

Question 11

Question 12

Question 13

Question 14

Question 15

Question 16

Question 17