BIO 120 cell and tissues



LESSON-27

ENERGY METABOLISM: THE PHOTOTROPHS

CARBON FIXATION: THE CALVIN CYCLE

A. Objectives

- State the energy problem of the phototroph; explain why phototrophs are C(carbon) -autotrophs;

- Give an overview of the Calvin cycle; tell what happens during a single turn of the Calvin cycle; explain the synthesis of glucose by the Calvin cycle; make a balance sheet of the synthesis of glucose by the Calvin cycle and note the origin of the substrates.

- List the balance sheet for photosynthesis; discuss short-comings of photosynthesis of plants; explain differences between C-3, C-4, and CAM plants.

B. Lecture outline

1. PROBLEMS OF PHOTOTROPHS: C-autotrophs

2. REDUCTION OF CARBON DIOXIDE: THE CALVIN CYCLE

Read: The carbon fixation reactions (SBMp202-204)

a. key reactions of the Calvin cycle

b. synthesis of a 6-C sugar

c. balance sheet

3. ENERGY METABOLISM OF PLANTS

a. structure and functional relationship of chloroplasts

b. C3, C4, and CAM plants.

Read: Photorespiration reduces photosynthesis efficiency (SBM p204)

The initial carbon fixation step differs in C4 and CAM plants (SBM p204-206)

- the problem of ribulose-l,5-diphosphate carboxylase,

- photorespiration losses in C3 plants,

— C4 plants concentrate carbon dioxide,

— carbon fixation in succulents (CAM).

C. Study Questions.

1. What is the goal of carbon fixation?

A. The incorporation into organic molecule AND reduction of carbon.

B. Reduction of carbon.

C. Oxidation of carbon.

D. Incorporation of carbon in organic molecules.

E. Oxidative decarboxylation of sugar molecules.

2. The dark reactions of photosynthesis are those that

A. convert chlorophylls into enzymes.

B. convert enzymes into chlorophylls.

C. convert carbon dioxide into sugars.

D. convert water into hydrogen and oxygen.

E. go on all night.

2. In photosynthesis, light energy is used to extract hydrogen atoms from

A. carbon dioxide.

B. chlorophyll.

C. citric acid.

D. glucose.

E. water.

4. The overall result of photosynthesis can be expressed as

A. 6 Co2 + 6 H20 ( glucose + 6 O2.

B. CO2 + H20 ( glucose + 02.

C. glucose + 602(6C02+6 H20.

D. carbon dioxide + photons (glucose + oxygen.

E. 6 CO2 + 6 H20 ( 36 ATP + 6 O2.

8. Identify in what step of the Calvin cycle carbon is reduced.

A. ribulose-l,5-diphosphate ( 2 3-phosphoglycerate

B. 3-phosphoglycerate ( 1,3-diphosphoglycerate.

C. l,3-diphosphoglycerate ( glyceraldehyde-3-phosphate.

D. 2 glyceraldehyde-3-phosphate ( glucose.

E. 10 glyceraldehyde-3-phosphate ( 6 ribulose-5-phosphate.

9. How many ATP and reduced coenzymes are consumed to enter and reduce a single carbon into an organic molecule?

A. 1ATP and 1 NADH+H+

B. 2ATP and 2 NADH+H+

C. 3ATP and 2 NADH+H+

D. 6ATP and 2 NADH+H+

E. 12 ATP and 6 NADH+H+

5. When carbon dioxide is added to a molecule of ribulose-1, 6-diphosphate, the first observable product is

A. citric acid.

B. glucose or glucose—6—phosphate.

C. phosphoenolpyruvate.

D. glyceraldehyde-3-phosphate.

E. pyruvate.

6. The cycle of dark reactions that fix CO2 is nanied for its discoverer; it is called the

A. Bridge cycle.

B. Calvin cycle.

C. Krebs cycle.

D. Failey cycle.

E. Hertz cycle.

7. What is NOT a step of carbon dioxide fixation? The

A. introduction of carbon dioxide to ribulose-1, 6-diphosphate.

B. reduction of 1,3-diphosphoglycerate.

C. oxidation of glyceraldehyde-3-phosphate.

D. the formation of a hexose from two trioses.

E. the regeneration of the 5-carbon acceptor.

10. How many times does the Calvin cycle turn to synthesize a molecule of glucose?

A. 1.

B. 2.

C. 3.

D. 4.

E. 6.

11. How many ATP are consumed to synthesize glucose in the Calvin cycle?

A. 2.

B. 4.

C. 12.

D. 18.

E. 36.

12. By what mechanism are the ATP produced that are used in carbon fixation? By

A. chemical oxidation.

B. photophosphorylat ion.

C. reduction of coenzymes.

D. substrate-level phosphorylation.

E. osmosis.

13. Photorespiration is most rapid at A. high temperature.

B. low temperature.

C. high humidity.

D. low humidity.

E. low oxygen tension.

14. How many reduced coenzymes are required to synthesize a molecule of glucose?

A. 4.

B. 6.

C. 8.

D. 10.

E. 12.

15. In bright light the pH of the space enclosed by the thylakoid membrane

A. is more alkaline than the stroma.

B. is more alkaline than the cytoplasm.

C. is acidic.

D. has a lower proton content than the stroma.

E. is the same as that of the stroma.

16. Which of the following pairs is mismatched?

A. chloroplast stroma — Calvin cycle.

B. thylakoid membrane -photophosphorylat ion.

C. thylakoid membrane - harvest of light energy.

D. chloroplast stroma —accumulation of protons.

E. inner mitochondrial membrane —oxidative phosphorylat ion.

17. Embedded in the thylakoid membranes and protruding as knobs on the stromal surface of the thylakoids, there are

A. enzymes that fix carbon dioxide.

B. molecules of chlorophylls and carotenoids.

C. P700 and P680 molecules.

D. specialized mesophyll and bundle sheath cells.

E. transmembrane ATPases.

18. An enzyme that can bind both carbon dioxide and oxygen is

A. CAM carboxylase.

B. carbonic anhydrase.

C. phosphoenolpyruvate carboxylase.

D. ribulose-1, 5-diphosphate decarboxylase.

E. ribulose-1, 5-diphosphate carboxylase.

19. When the first enzyme of the Calvin cycle combines with oxygen, carbon dioxide fixation is reversed, an effect called

A. competitive fixation.

B. carbon dioxide fixation.

C. photorespiration.

D. photooxidat ion.

E. photophosphorylat ion.

20. Identify the raw materials of the Calvin cycle.

A. oxygen and carbon dioxide.

B. ribulose-1, 5-biphosphate, NADH+H+, ATP and CO2.

C. NAD + and water.

D. ATP and NADH+H+.

E. glucose and oxygen.

21. As a result of photosynthetic electron transport, the internal thylakoid space accumulates an excess of

A. H+ ions.

B. ATP.

C. electrons.

D. reduced coenzyme.

E. chlorophyll.

22. Internal chloroplast membranes are organized into flattened sacs called A. basal bodies.

B. photosystems.

C. stromas.

D. thylakoids.

E. central vacuoles.

23. In oxygenic photosynthesis, NADH+H+ is A. a product of the C3 pathway.

B. a product of electron flow.

C. a source of oxygen.

D. the raw material for the 03 pathway.

E. regenerated in the Calvin cycle.

24. In oxygenic photosynthesis, water is A. a product of the C3 pathway.

B. a product of electron flow.

C. a source of oxygen.

D. the raw material for the 03 pathway.

E. regenerated in the Calvin cycle.

25. Isolated chloroplasts are exposed to blue light. In what part of the chloroplast would the proton concentration be greatest?

A. cytoplasm.

B. space between inner and outer membrane of envelope.

C. stroma

D. thylakoid membrane.

E. thylakoid space.

26. Under which conditions would you expect an electron flow in the thylakoid membrane? Chloroplasts exposed to

A. green light.

B. light of low intensity.

C. very low levels of carbon dioxide.

D. blue light. E. very cold temperatures.

27. A geranium plant (A) is placed in the dark for 6 days. A second plant (B) is exposed to continuous blue light for 6 days and a third plant (C) is exposed to green light for the same period of time. All are watered. At the end of the 6 days the carbohydrate content of their leaves is measured. What result do you expect?

A. A, B, and C have the same amount of carbohydrates.

B. A will have more carbohydrates than B or C.

C. B will have more carbohydrates than A or C.

D. C will have more carbohydrates than B or C.

E. B and C have the same amount of carbohydrates and more than A.

28. In oxygenic photosynthesis, carbon dioxide is

A. a product of the C3 pathway.

B. a product of electron flow.

C. a source of oxygen.

D. the raw material for the C3 pathway.

E. regenerated in the Calvin cycle.

29. In oxygenic photosynthesis, glyceraldehyde-3-phosphate is

A. a product of the C3 pathway.

B. a product of electron flow.

C. a source of oxygen.

D. the raw material for the C3 pathway.

E. regenerated in the Calvin cycle.

30. In oxygenic photosynthesis, ribose1, 5-diphosphate is

A. a product of the C3 pathway.

B. a product of electron flow.

C. a source of oxygen.

D. the raw material for the C3 pathway.

E. regenerated in the Calvin cycle.

31. Isolated chloroplasts are exposed to a range of monochromatic light waves representing the visible spectrum. What wavelength of light will result in the greatest production of oxygen?

A. blue.

B. green.

C. yellow.

D. orange.

E. red.

32. Which statements are correct for the light-dependent reactions of oxygenic photosynthesis (More than 1 correct choice.)

A. Located in chloroplast stroma.

B. Requires chlorophylls.

C. Fixation of carbon dioxide.

D. Produces ATP and NADH+H+.

E. Releases oxygen.

33. Which statements are correct for the light—independent reactions of oxygenic photosynthesis. (More than 1 correct choice.)

A. Located in chloroplast stroma.

B. Requires chlorophylls.

C. Fixation of carbon dioxide.

D. Produces ATP and NADH+H~.

E. Releases oxygen.

34. Ribulose phosphate is synthesized from:

A. NADP+.

B. pyruvate.

C. G3P.

D. RuBP.

E. CO2.

35. Which of the following is not one of the intermediates or products of the carbon fixation reactions?

A. NADPH

B. phosphogylcerate (PGA)

C. glyceraldehyde 3-phosphate

D. glucose

E. ribulose bisphosphate

36. In C4 plants, reactions that fix CO2 into four-carbon compounds occur in:

A. guard cells.

B. epidermal cells.

C. bundle sheath cells.

D. mesophyll cells.

E. xylem cells.

37. In C3 plants, the ______________ are typically closed at night and open during the daytime to allow for gas exchange.

A. stomata

B. epidermis

C. spongy mesophyll

D. grana

E. cuticles

38. At night, CAM plants incorporate CO2 into ____________, which is stored in the ____________ of their cells.

A. fructose; vacuoles

B. acetyl CoA; mitochondria

C. glucose; starch granules

D. pyruvate; starch granules

E. malate; vacuoles

39. Plants, algae, and certain bacteria are:

A. inorganic synthesizers.

B. consumers.

C. chemosynthetic.

D. independent trophs.

E. producers.

40. All organisms are classified into two general trophic groups. These two groups are:

A. organic and inorganic.

B. consumers and decomposers.

C. autotrophs and producers.

D. autotrophs and heterotrophs.

E. anaerobic autotrophs and aerobic autotrophs.

41. The inputs for __________ are CO2, NADPH, and ATP.

A. cyclic electron transport

B. the carbon fixation reactions

C. noncyclic electron transport

D. photosystems I and II

E. chemiosmosis

42. The Calvin cycle begins when CO2 react with

A. phosphoenolpyruvate

B. glyceraldehydes-3-phosphate

C. ribulose bisphospate

D. oxaloacetate

E. phosphoglycerate

43. The enzyme directly responsible for almost all carbon fixation on Earth is

A. rubisco

B. PEP carboxylase

C. ATP synthase

D. phosphofructokinase

E. ligase

44. In C4 plants, C4 and C3 pathways occur at different ______________; whereas in CAM plants, CAM and C3 pathways occur at different _________________.

A. times of day; locations within the leaf

B. seasons; locations

C. locations; times of day

D. locations; seasons

E. times of day; seasons

45. An organism characterized as a photoautotroph obtains energy from ______________ and carbon from ______________.

A. light; organic molecules

B. light; CO2

C. organic molecules; organic molecules

D. organic molecules; CO2

E. O2; CO2

46. Animals, fungi, and many bacteria that use organic molecules as a source of both energy and carbon are:

A. photoautotrophs.

B. catabolic autotrophs.

C. chemoheterotrophs.

D. photoheterotrophs.

E. chemoautotrophs.

47. Which term is not correctly matched with the appropriate energy source or carbon source?

A. heterotroph—organic energy sources

B. chemotroph—chemical energy sources

C. phototroph—light energy sources

D. autotroph—carbon fixation.

E. All of the choices are correct.

................
................

In order to avoid copyright disputes, this page is only a partial summary.

Google Online Preview   Download