Topic 3 review Name ____________Key_______________________________

Respiration

1. What is a catabolic pathway?______ The breakdown of organic molecules is exergonic

2. What are two catabolic pathways? _____fermentation, aerobic respiration, anaerobic respiration, cellular

respiration__________

3. Why is cell resp also called aerobic resp? _________________________________________________________

Aerobic respiration consumes organic molecules and O2 and yields ATP. Oxygen is required

4. Write the equation for resp. ____________________________________________________________

5. What type of reaction is cell resp? _______redox (oxidation – reduction reaction), exergonic__________

6. In the space below, draw a flow chart of glycolysis to explain what goes in, what comes out, and what is made in

the process.

Glucose (6C) is split into 2 molecules of pyruvate (ionized form of pyruvic acid) (3C) in a 10 step process each controlled

by a specific enzyme

For each glucose molecule entering glycolysis the end products are:

a. Net gain of 2 ATP

b. 2 NADH produced

c. 2 molecules of pyruvate

Summary equation for glycolysis:

C6H12O6 + 2NAD+ + 2ADP + 2Pi 2C3H4O3 (pyruvate) + 2NADH + 2H+ + 2ATP + 2H2O

7. Explain why there is a discrepancy in the gain and net gain of ATP. 2 ATP are used in Energy Investment Phase

8. After glycolysis, if oxygen is present, what happens? ______ ____The citric acid cycle, also called the Krebs cycle,

takes place within the mitochondrial matrix.

9. Where does the pyruvate go? __________________ pyruvate enters the mitochondrion where enzymes of the

citric acid cycle complete the oxidation of glucose to carbon dioxide ____ In the presence of O2, pyruvate enters

the mitochondrion. Before the citric acid cycle can begin, pyruvate must be converted to acetyl CoA, which links

the cycle to glycolysis. The cycle oxidizes organic fuel derived from pyruvate, generating 1 ATP, 3 NADH, and 1

FADH2 per turn. ___

10. How does it get there? ___transport protein__ pyruvate must be converted to acetyl CoA, which links the cycle

to glycolysis. ___

11. What happens to the pyruvate before it enters the CAC? What is made during the process? _________

Junction between glycolysis and the Citric Acid Cycle. As pyruvate enters the mitochondria by active transport,

a multienzyme complex modifies the pyruvate into acetyl CoA which enters the Citric Acid Cycle in the matrix.

Requires 3 rxns:

a. A carboxyl group is removed as CO2.

b. A pair of electrons is transferred to NAD+ to form NADH.

c. The oxidized fragment, acetate, combines with coenzyme A to form acetyl CoA.

12. What is the CAC also known as? _____Krebs Cycle________________________________

13. Why does the CAC require two turns? _____because glucose yields two pyruvates____

14. What is the total amount of products made (per glucose) in the CAC? 2 CO2,3 NADH, 1 oxaloacetate, 1 ATP, 1

FADH2

15. What are the two ways ATP can be made? ___oxidative phosphorylation, substrate-level phosphorylation_____

16. Which way does glycolysis and CAC make it? __________ substrate-level phosphorylation __________________

17. After the CAC, which electron carriers enter the ETC? _______ NADH and FADH2 ___________________

18. Which enters at the beginning of the chain? _____ NADH ______________________________________

19. The energy of moving electrons pumps ___H+____ out of the mitochondrial matrix.

20. Hydrogen ions are also called ___protons_____.

21. What acts as the final electron acceptor at the end of the ETC? ________O2________________________

22. When it accepts those electrons, what is made? ___Water_____________________

23. What has been formed by pumping protons out of the mitochondrial matrix? _________proton gradient__

24. How do they get back in the matrix? _______ATP synthase which harnesses proton motive force________

25. What is that process called and what does that process make? _ATP synthase harnesses the proton motive force

– the gradient of hydrogen ions – to phosphorylate ADP, forming ATP. The proton moive force is in place

because the inner membrane of the mitochondria is impermeable to hydrogen ions. . Electrons are held behind

the inner membrane with their only exit ATP synthase. This is called chemiosmosis – which is an energy coupling

mechanism that uses energy stored in the form of an H+ gradient across a membrane to drive cellular

work_______________

26. What are the ETC and chemiosmosis called together? _Oxidative phosphorylation____________

27. Where is most ATP made? ___Oxidative phosphorylation, specifically Chemiosmosis__________________

28. According to your review book, what is the maximum ATP output? _36 - 38_ What was it according to your

textbook? _____________

29. If oxygen is not present after glycolysis, what happens in yeast cells? What about muscle cells? __anaerobic

respiration – fermentation which consists of glycolysis and reactions that regenerate NAD+. In glycolysis oxygen

is not needed to accept electrons; NAD+ is the electron acceptor.

Yeast – alcohol fermentation – pyruvate is converted to ethanol, releasing CO2 and oxidizing NADH in the process to

create more NAD+

Humans – lactic acid fermentation – pyruvate is reduced by NADH (NAD+ is formed in the process), and lactate is

formed as a waste product

30. Explain the products and byproducts of both of these processes. ___

Alcoholic Fermentation

Carried out by bacteria and yeast

Produces 2 CO2, 2 ATP, and 2 molecules of ethanol (C2H6O)

Regenerates NAD+

Lactic Acid Fermentation

Carried out in muscle cells of animals under anaerobic conditions

Produces 2 ATP and 2 molecules of lactic acid (C3H6O3)

Regenerates NAD+

Lactic acid produced by muscle cells causes “muscle fatigue” and is toxic to cells

Lactic acid is carried to liver and converted back to pyruvate when O2 is available.

31. The importance of fermentation is that __ NAD+. ____ is regenerated for further use in glycolysis.

32. How much ATP is made in the one process of fermentation including glycolysis? _2

33. What is the difference between facultative and obligate anaerobes? _____

Obligate Anaerobes- organisms that cannot survive in the presence of oxygen. Carry out only fermentation or

anaerobic respiration.

Facultative Anaerobes- organisms that can survive using fermentation or respiration.

34. What acts as a regulator of respiration? _____ Cells respond to changing metabolic needs by controlling rxn

rates. Feedback inhibition is the most common mechanism for control. If ATP concentration begins to drop,

respiration speeds up; when there is plenty of ATP, respiration slows down. Control of catabolism is based

mainly on regulating the activity of enzymes at strategic points in the catabolic pathway

Phosphofructokinase—regulating enzyme of glycolysis

-pacemaker of glycolysis and respiration

-stimulated by ADP or AMP

Photosynthesis

35. What is the difference between autotrophs and heterotrophs? ___autotrophs – producers, make their own

food, self- feeders, sustain themselves without eating anything derived from other organism

heterotrophs – consumers, live on compounds produced by other organisms, _______________________

36. Draw a chloroplast and correctly label the parts.

37. What is the most important pigment in photosynthesis? ___chlorophyll_____________

38. Where are most chloroplasts found? in cells of the mesophyll, the interior tissue of the leaf

39. What is the function of stomata? ______ . CO2 enters and O2 exits the leaf through microscopic pores ______

40. What is the equation for photosynthesis? ___ 6 CO2 + 12 H2O* + light energy C6H12O6 + 6 O2* + 6H2O

Simplest photosynthetic equation:

CO2 + H2O [CH2O] + O2

41. What do pigments do? ____ Pigments are substances that absorb visible light

Different pigments absorb different wavelengths

Wavelengths that are not absorbed are reflected or transmitted

Leaves appear green because chlorophyll reflects and transmits green light

42. Which colors of light are most effective in driving photosynthesis? ___ Chlorophyll a is the main photosynthetic

pigment and absorbs best in the red and blue wavelengths, and least in the green.

Accessory pigments, such as chlorophyll b, broaden the spectrum used for photosynthesis

Accessory pigments called carotenoids absorb excessive light that would damage chlorophyll

-known as photoprotective

43. What is carbon fixation? ________when CO2 from the air is incorporated into organic molecules_______

44. What is photophosphorylation? _______the process in which light reactions also generate ATP, using

chemiosmosis to power the addition of a phosphate group to ADP__________

45. What two products are made in the light reactions and used in the calvin cycle? ___NADPH and ATP______

46. What product of the light reactions is released? ______O2_____________________

47. What are the major parts to photosynthesis? ______light reactions and Calvin cycle (Dark Reactions)_________

48. What are the two major parts to the light reactions? ______photosystems and Electron transport chains

3. Photosystems have two parts – light harvesting complex_ consists of a reaction-center complex (a type of

protein complex) surrounded by light-harvesting complexes. The light-harvesting complexes (pigment molecules

bound to proteins) funnel the energy of photons to the reaction center. A primary electron acceptor in the

reaction center accepts an excited electron from chlorophyll a. Solar-powered transfer of an electron from a

chlorophyll a molecule to the primary electron acceptor is the first step of the light reactions

49. What are photosystems? How many are there? Which comes first? ___groups of pigment molecules in the

thylakoid membrane of chloroplasts, 2 of them, PS II comes first___

Photosystem II (PS II) functions first (the numbers reflect order of discovery) and is best at absorbing a wavelength of

680 nm. The reaction-center chlorophyll a of PS II is called P680

Photosystem I (PS I) is best at absorbing a wavelength of 700 nm

The reaction-center chlorophyll a of PS I is called P700

50. Explain the difference between cyclic and noncyclic electron flow?

Linear Electron Flow – the flow of electrons through the photosystems in the thylakoid membrane

During the light reactions, there are two possible routes for electron flow: cyclic and linear

1 - Linear electron flow, the primary pathway, involves both photosystems and produces ATP and NADPH using

light energy

2 - A photon hits a pigment and its energy is passed among pigment molecules until it excites P680

3 - An excited electron from P680 is transferred to the primary electron acceptor

4 - P680+ (P680 that is missing an electron) is a very strong oxidizing agent

5 - H2O is split by enzymes, and the electrons are transferred from the hydrogen atoms to P680+, thus reducing it

to P680

6 - O2 is released as a by-product of this reaction

7 - Each electron “falls” down an electron transport chain from the primary electron acceptor of PS II to PS I

8 - Energy released by the fall drives the creation of a proton gradient across the thylakoid membrane

9 - Diffusion of H+ (protons) across the membrane drives ATP synthesis

cyclic electron flow – uses PS I, but not PSII. Uses a short circuit of linear electron flow by cycling the excited electrons

back to their original starting point in PSI. Cyclic electron flow produces ATP by chemiosmosis, but no NADPH is

produced and no oxygen is released

51. Sunlight stimulates the __chlorophyll a molecule in the P680 reactions center____.

52. What happens to the electrons from photosystem II? ___original excited electron passes from the primary

electron acceptor of PSII to PSI through an electron transport chain___________________

53. What is created in the process? __O2 are formed in the splitting of water molecules.

The energy from the transfer of electrons down the electron transport chain is used to pump protons, creating a

gradient that is used in chemiosmosis to phosphorylate ADP to ATP _________________________________

54. What happens to electrons in PS I? ____10 - In PS I (like PS II), transferred light energy excites P700, which loses

an electron to an electron acceptor

11 - P700+ (P700 that is missing an electron) accepts an electron passed down from PS II via the electron transport chain

55. How does each photosystem replace its electrons? _____electrons just donated by PSI are replaced by the

electrons from PSII, the ultimate source of electrons is water_____________

56. Explain how chemiosmosis occurs. ___Each electron “falls” down an electron transport chain from the primary

electron acceptor of PS I to the protein ferredoxin (Fd). The electrons are then transferred to NADP+ and reduce

it to NADPH. The electrons of NADPH are available for the reactions of the Calvin cycle. In chloroplasts, protons

are pumped into the thylakoid space and drive ATP synthesis as they diffuse back into the stroma. . ATP and

NADPH are produced on the side facing the stroma, where the Calvin cycle takes place. In summary, light

reactions generate ATP and increase the potential energy of electrons by moving them from H2O to NADPH

Calvin Cycle - 3 phases = Carbon fixation, reduction, and regeneration of RuBP

57. What enters the Calvin cycle? ______3 -CO2__________ IT combines with __the enzyme Rubisco and Ribulose

Bisphosphate (RuBP)__ to form ___a shrort-lived intermediate (3 phosphoglycerate)_____. Then _____6 (2 per

CO2)_____ ATP and 6 ___NADPH (2 per CO2)_ are added to make ___6 G3P______, which is the actual final

product of the Calvin cycle.

58. _1__ G3P exits. What happens to the other five? _____to regenerate the 5 G3P___________

59. How is glucose made? ______Two G3P molecules can combine to form glucose_____________

60. What are alternative mechanisms of carbon fixation? ________C4 and CAM Plants___________

61. Explain the difference between the two.

C4 -

1. C4 plants minimize the cost of photorespiration by incorporating CO2 into four-carbon compounds in mesophyll cells

2. This step requires the enzyme PEP carboxylase

3. PEP carboxylase has a higher affinity for CO2 than rubisco does; it can fix CO2 even when CO2 concentrations are low

4. These four-carbon compounds are exported to bundle-sheath cells, where they release CO2 that is then used in the

Calvin cycle

5. Adaptive process which enhances carbon fixation under conditions that favor photorespiration (hot, arid)

6. Occurs in corn, sugarcane, agricultural grasses

CAM-

1. Some plants, including succulents, use crassulacean acid metabolism (CAM) to fix carbon

2. CAM plants open their stomata at night, incorporating CO2 into organic acids

3. Stomata close during the day, and CO2 is released from organic acids and used in the Calvin cycle