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G12 HL Biology – Topic 3 Exam Review Questions
KNOWLEDGE /27
1.
UNDERSTANDING /30
Which of the following could cause denaturation of an enzyme?
A.
Substrate concentration
B.
A competitive inhibitor
C.
High temperature
D.
Low salt concentration
(1)
2.
What effect do enzymes have on the activation energy of exergonic and endergonic reactions?
Activation energy of Activation energy of
exergonic reactions endergonic reactions
A.
increases
increases
B.
decreases
decreases
C.
increases
decreases
D.
decreases
increases
(1)
3.
Consider the metabolic pathway shown below.
A
1
B
2
C
3
D
4
E
If there is end-product inhibition, which product (B to E) would inhibit which enzyme (1 to 4)?
Product
Enzyme
A.
C
4
B.
B
3
C.
B
4
D.
E
1
(1)
1
4.
In the enzyme controlled pathway shown below, which compound is most likely to inhibit
enzyme (w)?
Precursor
A.
I
B.
II
C.
III
D.
IV
enzyme
w

enzyme
x
I

enzyme
y
II

enzyme
z
III

IV
(1)
5.
The graph below shows the effect of changing the substrate concentration on an enzyme
controlled reaction.
40 % substrate
20 % substrate
10 % substrate
Amount of product formed
5 % substrate
2.5 % substrate
0 % substrate
Time
What is the correct interpretation of these data?
A.
The rate of reaction increases continuously with increase in substrate concentration.
B.
The rate of reaction decreases continuously with increase in substrate concentration.
C.
The rate of reaction increases up to a point and then remains constant.
D.
The rate of reaction is not affected by any change in the substrate concentration.
(1)
6.
Which two colours of light does chlorophyll absorb most?
A.
Red and yellow
B.
Green and blue
C.
Red and green
D.
Red and blue
(1)
2
7.
Pigments are extracted from the leaves of a green plant. White light is then passed through the
solution of pigments. What effect do the leaf pigments have on the white light?
A.
Green wavelengths are absorbed and red and blue wavelengths are transmitted.
B.
Red and blue wavelengths are absorbed and green wavelengths are transmitted.
C
Blue wavelengths are absorbed and green and red wavelengths are transmitted.
D.
Green and red wavelengths are absorbed and blue wavelengths are transmitted.
(1)
8.
What is needed in photosynthesis to convert carbon dioxide into organic molecules?
A.
Light and hydrogen from the splitting of water
B.
Light and oxygen from the splitting of water
C.
ATP and hydrogen from the splitting of water
D.
ATP and oxygen from the splitting of water
(1)
9.
How is the proton gradient generated in chloroplasts during photosynthesis?
A.
Flow of electrons from carrier to carrier in the thylakoid membrane causes pumping of
protons across the thylakoid membrane.
B.
Light causes protons to flow through protein channels in the thylakoid membrane.
C.
Light splits water molecules in the stroma, causing the release of protons.
D.
Protons are pumped across the thylakoid membrane using energy from ATP.
(1)
10.
Why is the action spectrum for photosynthesis similar to the absorption spectra of photosynthetic
pigments?
A.
Photosynthetic pigments have the same optimum temperature as the enzymes used in
photosynthesis.
B.
Plants absorb the same photosynthetic pigments for use in photosynthesis.
C.
Only wavelengths of light absorbed by pigments can be used in photosynthesis.
D.
The amount of energy absorbed by photosynthetic pigments is equal to the activation
energy for photosynthesis.
(1)
3
11.
How many molecules of acetyl CoA (ethanoyl CoA) does the oxidation of the fatty acid stearic
acid produce?
CH 3
CH 2
CH 2
CH 2
CH 2
CH 2
CH 2
CH 2
CH 2
CH 2
Stearic acid
CH 2
CH 2
CH 2
CH 2
CH 2
CH 2
CH 2
COOH
A.
2
B.
6
C.
9
D.
18
(1)
12.
Of the following products, which is produced by both anaerobic respiration and aerobic
respiration in humans?
I.
Pyruvate
II.
ATP
III.
Lactate
A.
I only
B.
I and II only
C.
I, II and III
D.
II and III only
(1)
4
13.
Which of the following produce ATP in mitochondria?
A.
The movement of protons from the matrix to the intermembrane space
B.
The movement of protons from the intermembrane space to the cytoplasm
C.
The splitting of water molecules and the movement of electrons to oxygen
D.
The movement of protons from the intermembrane space to the matrix
(1)
14.
Which way do the protons flow when ATP is synthesized in mitochondria?
A.
From the inner matrix to the intermembrane space
B.
From the intermembrane space to the inner matrix
C.
From the intermembrane space to the cytoplasm
D.
From the cytoplasm to the intermembrane space
(1)
15.
What is the sequence of stages during the conversion of glucose into pyruvate in glycolysis?
A.
lysis
phosphorylation of sugar
B.
lysis
oxidation
C.
phosphorylation of sugar
lysis
D.
phosphorylation of sugar
oxidation
oxidation
phosphorylation of sugar
oxidation
lysis
(1)
16.
What accumulates in the inter-membrane space of the mitochondrion during electron transport?
A.
ATP
B.
Electrons
C.
Protons (hydrogen ions)
D.
Oxygen
(1)
17.
Which is not a product of the Krebs cycle?
A.
CO2
B.
NADH + H+
C.
Pyruvate
D.
ATP
(1)
5
18.
How many ATP molecules (net yield) are produced per molecule of glucose as a direct result of
glycolysis?
A.
2
B.
4
C.
10
D.
38
(1)
There are many abiotic factors that affect the rate of photosynthesis in terrestrial plants. Wheat is
an important cereal crop in many parts of the world. Wheat seedlings were grown at three
different concentrations of carbon dioxide (in parts per million) and the rate of photosynthesis
was measured at various light intensities.
Rate of photosynthesis / l CO 2 min –1
19.
50
40
30
key:
20
1300 ppm CO2
500 ppm CO2
280 ppm CO2
10
0
0
5
10
15
20
Light intensity / × 10 3 lumen m –2
[Source: Adapted from J P Kimmins, Forest Ecology, (2nd edition) page 161]
(a)
Describe the relationship between the rate of photosynthesis and light intensity for wheat
seedlings grown at a CO2 concentration of 500 ppm.
rate of photosynthesis increases (rapidly) /
directly proportional;
rate of photosynthesis levels off /
increases slightly after 10000 lumen m–2;
(2)
(b)
Outline the effect of CO2 concentration on the rate of photosynthesis of the wheat
seedlings.
maximum photosynthetic rate is highest with highest
CO2 concentration;
at low light levels, higher CO2 slightly increases the
photosynthetic rate;
at low CO2 / 280 ppm, the photosynthetic rate reaches its
maximum at low light levels / constant over most light intensity /
at 280 ppm CO2 concentration limits photosynthesis;
6
at 500 and 1300 ppm CO2 the curve is the same shape
but with different maximum rates /
each higher light intensity requires a higher CO2 concentration
to reach maximum rate;
maximum rate of photosynthesis from 280 to 500 ppm /
increases 5 to 6 times
while 500 to 1300 ppm increases 1.5 times;
(3)
(c)
The normal atmospheric concentration of CO2 is 370 ppm. Deduce the effect of doubling
the CO2 concentration to 740 ppm on the growth of wheat plants.
the rate of photosynthesis will increase (over the rate at 370 ppm);
the photosynthetic rate will at least double (but less than 5–6 times);
not linear;
bigger plants / more growth / more grain / greater yield;
(2)
Leaf area and chlorophyll levels were measured in sun leaves and shade leaves of Hedera helix
(English Ivy) and Prunus laurocerasus (Cherry Laurel). Sun leaves developed under maximal
sunlight conditions while shade leaves developed at reduced sunlight levels in the shadow of
other leaves.
Species
Leaf Type
Ivy
Laurel
Chlorophyll/
g ml-1
Leaf Area/
cm2
Shade
4.3
72.6
Sun
3.8
62.9
Shade
4.7
38.7
Sun
4.2
25.7
[Source: D Curtis, Plant Ecology independent project, 1990]
(d)
Calculate the percentage increase in the amount of chlorophyll in shade leaves of ivy
compared to sun leaves of ivy

4.3  3.8
 100  13.16% (Accept 13.2%)
3.8
(1)
(e)
Suggest a reason for the differences in chlorophyll concentration and leaf area in sun and
shade leaves in these two species.
shade leaves receive less light than sun leaves;
to capture sunlight, shade leaves produce more chlorophyll;
to capture sunlight, shade leaves have greater leaf area;
(2)
(Total 10 marks)
7
20.
(a)
State the site of the light-independent reactions in photosynthesis.
stroma (of chloroplast)
(1)
The absorption spectrum of chlorophyll a and chlorophyll b are shown in the graph below.
chlorophyll b
chlorophyll a
Absorbance
400
(b)
500
Wavelength / nm
600
700
On the graph above, draw the action spectrum of photosynthesis for a green plant.
(1)
peak at about 450 and at 650 nm and follows pattern of absorption spectrum
(c)
Explain photophosphorylation in terms of chemiosmosis.
electron transport causes proton/hydrogen ion pumping;
protons inside thylakoids;
accumulation of protons / H+ / drop in pH;
protons leave through proton channel (to stroma);
ATP synthetase / enzyme catalyses phosphorylation of ADP;
(3)
(Total 5 marks)
8
21.
Anaerobic respiration occurs in the absence of oxygen while aerobic respiration requires oxygen.
(a)
State one final product of anaerobic respiration.
ATP;
CO2;
ethanol;
lactic acid;
heat energy;
(1)
(b)
Complete the table showing the differences between oxidation and reduction.
Oxidation
Reduction
Electrons gained or
lost
Loss of electrons
Gain of electrons
Oxygen or hydrogen
gained or lost
Gain of oxygen/loss of
hydrogen
Loss of oxygen/gain of
hydrogen
(2)
(c)
The structure of a mitochondrion is shown in the electron micrograph below.
Name the parts labelled A, B and C and state the function of each.
A – matrix: site for Krebs' cycle / link reaction / ATP synthesis;
B – inner membrane/cristae: site of oxidative phosphorylation / e– transport
chain / increase surface area / ATP synthesis;
C – inter membrane : H+ / proton build up;
or
C – outer membrane: determines which substances enter the mitochondrion;
Award [1 max] if only the three labels are given.
3 max
(3)
(Total 6 marks)
9
22.
(a)
Define the term active site of an enzyme.
the site (on the surface of an enzyme) to which substrate(s) bind / the site (on the
enzyme) where it catalyzes a chemical reaction;
(1)
(b)
Outline how enzymes catalyze biochemical reactions.
bring substrates close together in active site / in correct orientation;
forms enzyme-substrate complex / substrate(s) bind to active site;
lowers the activation energy for the reaction;
weakens bonds in the substrate;
(2)
(c)
Explain the effect of pH on enzyme activity.
enzymes have an optimal pH;
lower activity above and below optimum pH / graph showing this;
too acidic / basic pH can denature enzyme;
change shape of active site / tertiary structure altered;
substrate cannot bind to active site / enzyme-substrate complex cannot form;
hydrogen / ionic bonds in the enzyme / active site are broken / altered;
(3)
(c)
The rate of cellular respiration is controlled by the allosteric inhibition of
phosphofructokinase by ATP. Phosphofructokinase is the first enzyme in the respiration
pathway. Explain the meaning of allosteric inhibition using this example.
ATP inhibits phosphofructokinase at (allosteric) site away from the active site;
inhibition alters the enzymes conformation / structure;
the active site does not accept the substrate molecule;
when respiration increases ATP levels phosphofructokinase is inhibited;
respiration slows down;
phosphofructokinase is the first enzyme in the respiration pathway so
there is no build up of metabolic intermediates;
as ATP is used up by the cell the inhibition of phosphofructokinase is reduced;
respiration speeds up again;
this is an example of negative feedback;
(4)
10
9.
Explain the similarities and differences in anaerobic and aerobic cellular respiration.
(Total 8 marks)
Answers must include both similarities and differences to receive full marks.
aerobic requires oxygen and anaerobic does not utilize oxygen;
similarities:
both can start with glucose;
both use glycolysis;
both produce ATP/energy (heat);
both produce pyruvate;
carbon dioxide is produced;
(both start with glycolysis) aerobic leads to Krebs' cycle and anaerobic
leads to fermentation;
3 max
differences:
anaerobic:
(fermentation) produces lactic acid in humans;
(fermentation) produces ethanol and CO2 in yeast;
occurs in cytoplasm of the cell;
recycles NADH (NAD+);
5 max
aerobic cellular respiration:
pyruvate transported to mitochondria;
further oxidized to CO2 and water (in Krebs' cycle);
produce a larger amount of ATP (36-38 ATP) / anaerobic produces less ATP (2);
can use other compounds / lipids / amino acids for energy;
11