8.3 photosynthesis past paper Q's

What occurs during the light-independent reactions of photosynthesis? A. ATP is produced. B. Ribose reacts with carbon dioxide to form glucose. C. Energy for the cycle is provided by the light-dependent reaction. D. Darkness stimulates the conversion of glucose to starch.

C

Describe the process of photolysis in photosynthesis

a. water is split/breaks b. using energy from light c. electrons «from photolysis» pass to photosystem II d. oxygen is a «waste» product e. hydrogen ions/protons are produced Allow answer given as an equation

Explain the effect of light intensity and temperature on the rate of photosynthesis.

(chlorophyll/antenna) in photosystem II absorbs light; absorbing light/photoactivation produces an excited/high energy/free electron; electron passed along a series of carriers; reduction of NADP+ / generates NADPH ++ H+ ;absorption of light in photosystem II provides electron for photosystem I; photolysis of water produces H+/O2 ;called non-cyclic photophosphorylation; in cyclic photophosphorylation electron returns to chlorophyll; generates ATP by H+ pumped across thylakoid membrane / by chemiosmosis / through ATP synthetase/synthase;

Where is chlorophyll found in a plant cell? A. Thylakoid membranes B. Stroma C. Matrix D. Cristae

A

State two products that pass from the light-dependent to the light-independent stages of photosynthesis. 1. .................................................................. 2. .................................................................. .

ATP and NADPH2/NADPH+ H+ (both needed)

Where is ATP synthase located?

B

Explain the effect of light intensity and temperature on the rate of photosynthesis 8M

both light and temperature can be limiting factors;other factors can be limiting;graph showing increase and plateau with increasing light / description of this;graph showing increase and decrease with increasing temperature / description of this; light: affects the light-dependent stage; at low intensities insufficient ATP; and insufficient NADPH ++ H+ produced; this stops the Calvin cycle operating (at maximum rate); temperature: affects light-independent stage / Calvin cycle; temperature affects enzyme activity; less active at low temperatures / maximum rate at high temperatures; but will then be denatured (as temperature rises further);

State the role of ribulose bisphosphate (RuBP) carboxylase in the Calvin cycle. 1M

fixes/adds carbon/CO2 to RuBP

Explain the light-independent reactions of photosynthesis. 9M!!

take place in the stroma of the chloroplast; produce carbohydrates; ribulose bisphosphate/RuBP is a five carbon compound; carbon dioxide fixed/added to RuBP / carboxylation; by RuBP carboxylase (enzyme)/Rubisco; forms unstable six carbon compound; this splits into (two molecules of) glycerate-3-phosphate/GP; ATP and NADPH produced in light-dependent reaction; ATP provides the energy; GP reduced to triose phosphate/TP; NADPH provides hydrogen; some three carbon sugars go to form hexose sugars; some go to making more RuBP; called the Calvin (Benson) cycle;

Where are the light-dependent and light-independent reactions taking place in the diagram below?

A

Where in the cell does the Calvin cycle take place? A. Stroma of chloroplast B. Mitochondrial matrix C. Cytoplasm D. Inside thylakoid

A

Which process occurs during the light-dependent reaction of photosynthesis? A. ATP, CO2 and H2O are produced. B. CO2 is used to produce carbohydrates. C. ATP and O2 are produced. D. RuBP is phosphorylated.

C

The electron micrograph shows part of a plant cell. Where do the light-independent reactions of photosynthesis take place?

B

Where are complex carbohydrates made in the chloroplast? A. In the intermembrane space B. In the stroma C. On the inner membrane D. In the thylakoid space

B

Which molecule would first contain 14C if the alga Chlorella was grown in the presence of light and radioactive CO2? A. Glycerate 3-phosphate B. Glucose C. Rubisco D. Ribulose bisphosphate (RuBP)

A

What is a function of Y? A. Carbon fixation B. Absorption of light C. Storage of glucose D. Production of ATP What is the structure labelled X? A. Stroma B. Granum C. Crista D. Starch granule

A B

Explain chemiosmosis as it occurs in photophosphorylation.

Remember, up to TWO "quality of construction" marks per essay. a. photophosphorylation is the production of ATP; b. (some of the) light absorbed by chlorophyll / photosystem II; c. photolysis/splitting of water separation of hydrogen ion from its electron; d. the electron transport system moves the electrons through a series of carriers; e. (electron transport system occurs) in the thylakoid membrane; f. electron transport linked to movement of protons into thylakoid space; g. a proton gradient builds up (in the thylakoid space); h. small thylakoid space enhances the gradient; i. hydrogen ions move by diffusion through the ATP synthase; j. ADP + inorganic phosphate (Pi) forms ATP; k. (the kinetic energy from) movement of hydrogen ions (through ATP synthase) generates ATP; l. ATP synthase is a protein complex in the thylakoid membrane; m. formation of proton gradient / ATP synthesis linked to electron transport is chemiosmosis; Award marks for a clearly drawn correctly annotated diagram.

What is the advantage of having a small volume inside the thylakoids of the chloroplast? A. High proton concentrations are rapidly developed. B. High electron concentrations are rapidly developed. C. Photosynthetic pigments are highly concentrated. D. Enzymes of the Calvin cycle are highly concentrated.

A

Draw a labelled diagram showing the structure of a chloroplast.

Award [1] for each of the following clearly drawn and correctly labelled. a. outer and inner membranes; b. stroma; c. thylakoid; d. granum; e. (70S) ribosomes / (naked) DNA; f. starch granules;

In a chloroplast where are the enzymes of the Calvin cycle located? A. Thylakoid membranes B. Stroma C. Grana D. Outer membrane of chloroplast

B

What process occurs during the light-independent reactions of photosynthesis? A. Oxygen is released into the atmosphere. B. Protons are pumped from the thylakoid space to the stroma. C. RuBP is carboxylated then regenerated in the Calvin cycle. D. Triose phosphate is converted to glycerate 3-phosphate.

C

The following is an electron micrograph of a chloroplast. Label I and II. I. .................................................................. II. .................................................................. [1] Explain the relationship between chloroplast structure and its function.

I. granum / grana II. stroma(both needed) large surface area of grana/thylakoids for light absorption/electron transport chains; (small) space inside thylakoids for accumulation of protons; (fluid) stroma contains enzymes/chemicals for light-independent reactions; presence of DNA/ribosomes means production of specific proteins possible; different photosynthetic pigments absorb different wavelengths of light; starch grains store excess carbohydrates from photosynthesis;

1. State the site of the light-independent reactions of photosynthesis. 2. Explain the relationship between the structure of the chloroplast and its function.

1. large surface area of thylakoids/grana for light absorption/electron transport chain; (small) space inside thylakoids for accumulation of protons; 2. (fluid) stroma for enzymes in Calvin cycle/light independent reactions; arrangement of photosystems to allow electron transport to take place; double membrane on the outside allows separation from rest of cell; presence of DNA/ribosomes for protein synthesis; starch grains store carbohydrate (from photosynthesis);

In the light-dependent reactions of photosynthesis what supplies low energy electrons to photosystem II? A. Photolysis of water B. Reduction of NADP+ C. Chemiosmosis D. Photosystem I

A

The image shows a chloroplast. During photosynthesis, what happens in the chloroplast at the location labelled lumen? A. Protons accumulate. B. Pyruvate undergoes decarboxylation. C. NADH is oxidized. D. Oxygen is produced.

A

What products of the light-dependent reactions are used in the light-independent reactions? A. ATP and NADPH B. NADPH and ribulose bisphosphate (RuBP) C. CO2 and ATP D. ATP and O2

A

Which of the following is a role of ATP in photosynthesis? A. It provides the energy to make carbohydrate molecules. B. It splits water molecules to form oxygen and hydrogen. C. It breaks down pyruvate into carbon dioxide. D. It converts light energy into chemical energy.

A

Which reaction does not cause a net release of energy? A. ADP combines with inorganic phosphate to form ATP B. ATP releases inorganic phosphate to form ADP C. Loss of hydrogen from reduced NAD D. Oxidation of reduced FAD

A

Which technological advance enabled Calvin to perform his lollipop experiment on the light-independent reactions of photosynthesis in 1949? A. Methods for tracing radioactive carbon incorporated in molecules produced by the alga Chlorella B. Development of electron microscopes enabling the molecules produced by the alga Scenedesmus to be viewed C. Methods for changing the wavelength of light shining on the alga Scenedesmus contained in the lollipop D. Development of X-ray diffraction techniques enabling the molecules produced by the alga Chlorella to be identified

A

What is produced by the light-dependent reactions of photosynthesis and used in the Calvin cycle? A. Hydrogen and oxygen B. ATP and NADPH C. NADPH and oxygen D. ATP and CO2

B

What is used to reduce NADP in the light-dependent reactions of photosynthesis? A. Conversion of ATP into ADP+Pi B. Electrons from Photosystem I C. Protons from the thylakoid space D. Oxygen released by photolysis of water

B

Which of the following factors influence(s) the rate of oxygen production in photosynthesis? I. Temperature II. Wavelength of light III. Number of mitochondria A. I only B. I and II only C. II and III only D. I, II and III

B

What reaction, involving glycerate 3-phosphate, is part of the light-independent reactions of photosynthesis? A. Glycerate 3-phosphate is carboxylated using carbon dioxide. B. Two glycerate 3-phosphates are linked together to form one hexose phosphate. C. Glycerate 3-phosphate is reduced to triose phosphate. D. Five glycerate 3-phosphates are converted to three ribulose 5-phosphates.

C

The diagram below shows the structure of a chloroplast. What is the structure labelled X? A. Ribosome B. Stroma C. Inner membrane D. Thylakoid

D

What happens to triose phosphate (TP) in the light-independent reactions of photosynthesis? A. TP is reduced to glycerate-3-phosphate (GP). B. TP is linked to CO2 by ribulose bisphosphate carboxylase (Rubisco). C. TP is oxidized by NADPH + H+. D. TP is regenerated into ribulose bisphosphate (RuBP).

D

The light-dependent reactions in photosynthesis take place on the thylakoid membranes. Explain the light-dependent reactions.

Remember, up to TWO "quality of construction" marks per essay. a. (chlorophyll/pigments/antenna complex) in photosystem II absorb light; b. light/photoactivation produces an excited/high energy/free electron; c. electrons pass from carrier to carrier/along electron transport chain/e.t.c.; d. protons pumped across thylakoid membrane/into thylakoid space; e. ATP produced (by the light dependent reactions); f. ATP production by chemiosmosis/by ATP synthase/ATP synthetase; g. electrons from photosystem II passed to photosystem I; h. light/photoactivation excites electrons in photosystem I (to higher energy level); i. production of NADPH/reduction of NADP(+) (using electrons from photosystem I); (reject NAD in place of NADP. Accept reduced NADP instead of NADPH) j. electrons from photolysis (needed) for photosystem II; k. oxygen from photolysis is a waste product/by-product/passes out/excreted; l. in cyclic photophosphorylation electrons from photosystem I return to it;

Isoprene is a chemical synthesized and emitted in large amounts by some plant species, especially oak (Quercus sp.) and poplar (Populus sp.) trees. It has been suggested that isoprene increases the tolerance of plants to high temperatures, which can cause a decrease in photosynthesis rates.Black poplar (Populus nigra) plants were subjected to two raised temperatures and to drought. Measurements of photosynthesis and isoprene emission were made during a 35-day-long drought stress (drought period) and 3 and 15 days after re-watering stressed plants (recovery period). The rate of photosynthesis was recorded as the carbon dioxide taken up per unit of leaf area per second. (look at other side for rest of question) a.Suggest one method other than measuring CO2 uptake by which the rate of photosynthesis could have been measured in these experiments. [1] b. Suggest why heat treatment may reduce photosynthesis rates. [2] c.Outline the effect of drought and of re-watering on the rate of photosynthesis. [1] d.Describe the isoprene emissions during the drought and recovery periods at 25°C. [2] e.Compare the effect of the two temperatures on the emission of isoprene. [2] f.State the effect of heat treatment on the rate of photosynthesis. [1] g.Using the results in the graph, deduce the effect of the presence of fosmidomycin on the rate of photosynthesis in the leaves. [2] h.Suggest possible conclusions for this experiment. [2] i.State the difference in percentage recovery of photosynthesis 1 hour after heat treatment between the 22 μL dm-3 isoprene treatment and the 0 μL dm-3 isoprene treatment. [1] j.Explain the evidence provided by the data in the bar chart for the hypothesis that isoprene improves plants' tolerance to high temperatures. [2] k.Suggest two reasons for some plant species synthesizing and emitting isoprene, but not other plant species such as common beans. [2

a. high/higher than optimum temperatures denature enzymes (of Calvin cycle);ribulose bisphosphate carboxylase/rubisco stops working/does not bind substrate;wilting / withering / loss of water / decrease in turgor / increased transpiration;closure/reduced aperture of stomata;lower CO2 level inside leaf / reduced CO2 diffusion/uptake into leaf; b. rate decreases/drops (to zero) with drought and increases when re-watered/recovering c. slight decrease/constant initially then falls / falls increasingly rapidly / decreases exponentially (in drought/up to Day 35);increases almost to original level/ but doesn't reach original level / rapidly at first then less rapidly / increases then reaches plateau (during recovery/after Day 35); d. higher/greater (emission) at 35°C than 25°C during both drought and recovery;both at (approximately) same level at end of drought period/at 35 days;both increase during recovery but not to original level;less/little difference in emission between temperatures during recovery/after watering / converse; e. decreases (rate of photosynthesis); f. no effect before (the first) heat treatment;lower rate/greater reduction in rate during heat treatments with fosmidomycin;lower photosynthesis/fosmidomycin reduces recovery after heat treatments;Ignore statements that fosmidomycin reduces the rate of photosynthesis if this is not related to heat treatments. g. high temperature/heat stress/treatment reduces rate of photosynthesis;repeated heat treatments cause greater reduction in photosynthesis;isoprene causes less change/less reduction in photosynthesis due to heat/46°C /higher rate of photosynthesis during heat treatment with isoprene (than without);isoprene helps photosynthesis to rise again after heat (treatments); h. 26 (%) (Allow a range of 25 % to 27 %) i. faster recovery with isoprene than without/than with water treatment;recovery faster/better/improved with higher isoprene concentration (than lower);after both time periods / after 24 hours and 1 hour; j. different plants live in/evolved in/are adapted to different temperature regimes;(selective) advantage for plants that produce isoprene in high temperature regions;isoprene synthesis uses energy/materials/only beneficial at high temperatures;some plants do not have the enzymes/genes for making isoprene;

Explain the relationship between the action spectrum and the absorption spectrum of photosynthetic pigments in plants.

a. each photosynthetic pigment has a different absorption spectrum; b. as light of different wavelengths is absorbed differently; c. absorption spectra combine to create the action spectrum / action spectrum shows how much photosynthesis occurs at each wavelength; d. so plant can use a wider range of wavelengths for photosynthesis; e. appropriate labelled diagram of absorption and action spectra; f. action spectrum takes into account "in vivo"/actual environmental conditions;

Explain the light-independent processes of photosynthesis in plants.

a. occurs in stroma (of chloroplast); b. energy/ATP and NADPH provided by the light-dependent reactions; c. Calvin cycle; d. carbon dioxide fixed to RuBP / carboxylation of RuBP/ribulose bisphosphate; e. by RuBP carboxylase/rubisco;f. forms unstable 6C compound / forms 6C compound which splits; g. glycerate 3-phosphate (is produced by carbon fixation); h. (glycerate phosphate) to triose phosphate/3C sugar by reduction/adding hydrogen; i. using NADPH/reduced NADP; j. triose phosphate/3C sugar converted to form hexose/glucose (phosphate); k. most/5/6 of triose phosphate used for regeneration of RuBP; l. ATP used to regenerate RUBP/convert glycerate 3-phosphate to triose phosphate;

Explain the processes by which light energy is converted into chemical energy. 8M

a. plants/producers/autotrophs convert light to chemical energy by photosynthesis b. chlorophyll/photosynthetic pigments absorb light c. electrons are excited/raised to higher energy level d. excited electrons pass along chain of electron carriers e. energy from electrons used to pump protons across thylakoid membrane/into thylakoid space f. chemiosmosis/proton gradient used to make ATP g. ATP synthase generates ATP h. pigments arranged in photosystems i. electrons from Photosystem II flow via the electron chain to Photosystem I j. electrons from Photosystem I are used to reduce NADP k. ATP and reduced NADP used in the light independent reactions/Calvin cycle l. carbohydrate/glucose/carbon compounds produced containing energy Award marking points for any point made on a clearly annotated diagram.

Some of the water carried to the leaves of a plant is used in photosynthesis. Explain the role of water in the light-dependent reactions of photosynthesis. 8M

a. water only plays a role in non-cyclic photophosphorylation; b. chlorophyll absorbs light/photons and activates electrons of photosystem II; c. excited/active electrons of photosystem II are passed to carriers; d. photolysis is the splitting of water; e. produces O2 and H+/proton and electrons; f. O2 released (as waste);g. electrons (from water) replace lost electrons in photosystem II; h. electrons from photosystem II pass (through carriers) to photosystem I; i. electrons from photosystem I pass to NADP+ (in stroma); j. NADP+ accepts H+/proton (from water) to form NADPH; k. electron flow causes protons pumped across thylakoid membranes/into the thylakoid space; l. creating a proton concentration gradient; m. chemiosmosis couples electron transport to ATP synthesis; n. protons pass through ATP synthase/synthetase; o. NADPH/H+/proton is passed to the light-independent reactions (to fix carbon);

Draw the absorption spectrum of chlorophyll. 4M

labelled x-axis: wavelength / colour;labelled y-axis: absorbance / % absorption; peak between 400 and 500 nm / blue light; peak between 600 and 700 nm / red light; blue peak higher than red peak;

Outline photoactivation of photosystem II in the light-dependent reaction of photosynthesis. 2M

light/photon absorbed by pigment molecules (in photosystem II)/chlorophyll; energy/electrons passed to chlorophyll molecule at the reaction centre; causes electron to be raised to higher energy level / electron is excited; this electron passed along chain of carrier molecules in photosystem II;

Using light as an example, explain the concept of limiting factors in photosynthesis. 3M

limiting factors can determine the rate of photosynthesis / if the level of a factor is changed the rate of photosynthesis changes; only changes to one factor will affect rate of photosynthesis at a particular time; light intensity affects the light-dependent reactions/production of ATP/NADPH; at low light levels the rate of photosynthesis is directly proportional to light intensity/light is limiting; at high light levels there is no further increase in the rate of photosynthesis/some other factor is limiting (e.g. CO2/temperature);Accept the above points illustrated by a suitable correctly sketched graph with both axes labelled and correct shape (see example below).

Suggest how Zostera marina can perform photosynthesis even at very low carbon dioxide concentrations. 1M

uses hydrogen carbonate ions;uses stored carbon dioxide / carbon dioxide from respiration;

Explain the process of photophosphorylation in chloroplasts 8M

using energy from light to provide energy; absorbing light/photoactivation produces an excited/high energy/free electron; absorption of light in photosystem II gives electron to chain of carriers; photolysis; H+ pumped across thylakoid membrane; protons pass through ATP synthetase/synthase;producing ATP; chemiosmosis; (chlorophyll/antenna of) photosystem I absorbs light; cyclic and non-cyclic photophosphorylation; (in non-cyclic photophosphorylation) photolysis of water produces H+/O2/e-; in cyclic photophosphorylation electron returns to photosystem I; Accept any of the above points shown in a clearly annotated diagram.