Unit 2 Review

1. Unit 2 Review Chapter 5 - 7

2. Checkpoint • How can an object at rest have energy? 2. Describe the energy transformations that occur when you climb to the top of a stairway. 3. Which form of energy is the most randomized and the most difficult to put to useful work? 4. Explain how ATP powers cellular work. 5. What is the source of energy for regenerating ATP from ADP? Where in the cell does this take place?

3. Answers • Potential energy = location or arrangement of its atoms 2. Convert chemical energy of food to the kinetic energy of your upward climb; at the top some of the energy has been stored as potential energy because of your higher elevation. The rest has been converted to heat 3. Heat energy 4. ATP transfers a phosphate group to other molecules, increasing the energy content of those molecules 5. Chemical energy harvested from sugars and other organic fuels via cellular respiration in the mitochondria.

4. Questions 6. What effect does an enzyme have on the activation energy of a chemical reaction? 7. How does an enzyme recognize its substrate? 8. How does the antibiotic penicillin work? 9. Explain why it is not enough just to say that a solution is hypertonic? 10. What is the usual energy source for active transport? 11. What is the primary difference between passive and active transport in terms of concentration gradient.

5. Answers 6. An enzyme lowers the activation energy of a chemical reaction. 7. The substrate and the enzyme’s active site are complementary in shape and chemical nature. 8. It inhibits an enzyme that certain bacteria use to make their cell walls. 9. Relative terms – depends on the solution and solute(s) 10. ATP 11. Passive – moves atoms or molecules along the concentration gradient (higher to lower), while active transport moves them against the concentration gradiens.

6. Questions 12. ___ is the capacity to perform work, while ___ is a measure of randomness. 13. A __ __ __ is a process that links the reception of a cell signal to a response within the cell. 14. Why does removing a phosphate group from the triphosphate tail in a molecule of ATP release energy? 15. How can an inhibitor disrupt an enzyme’s action without binding to the enzyme’s active site. 16. Which cellular transport require(s) energy? a) faciliated diffusion b) active transport c) osmosis

7. Answers 12. Energy; entropy 13. signal transduction pathway 14. Negative charged phosphate groups crowded together in the triphosphate tail repel each other. Release of a phosphate group makes some of this potential energy available to cells to perform work. 15. An inhibitor binding to another site on the enzyme can cause the enzyme’s active site to change shape. 16. Active transport

8. ATP Power P = phosphate group (a phosphorus bonded to oxygen atoms) Triphosphate tail is unstable, partly because of repulsion between the P groups which have a negative charge The P at the end tends to break away and bond to other molecules; this transfer, catalyzed by enzymes, provides energy for cellular work- ADP leftover Figure 5.5

9. The ATP Cycle 10 million ATP molecules spent and regenerated per second per cell • Cells spend ATP continuously – renewable resource • ATP is restored by adding a P group back to ADP • Mitochondria harvest energy from carbohydrates and lipids • Energy coupling: transfer of energy from processes that yield energy, breakdown of organic fuels  metabolic processes

10. Activation Energy – Jumping Bean Analogy a) a chemical reaction requires activation energy to break the bonds of the reactant molecules – the jumping beans represent reactant molecules that must overcome the barrier of activation b) an enzyme speeds the process by lowering the barrier of activation energy Fig 5.8

11. Sucrase is receptive for its substrate molecule • Substrate has the correct shape to fit the active site • Enzyme catalyzes the chemical reaction - hydrolysis of sucrose • Products – glucose and fructose, exit the active site Figure 5.9

12. Figure 5.10a, b

13. a) Cytoskeleton elements may bond to membrane proteins – proteins can adhere to the fibers of the ECM to coordinate EC and IC changes b) Cell signaling – protein with a binding site that fits the specific shape of a chemical messenger, such as a hormone (chemical messenger) c) Enzymatic activity – an enzyme with its active site exposed to its substrate Fig 5.11

14. d) Transport – a protein that spans the membrane may provide a selective channel for a particular solute e) Intercellular joining – proteins of adjacent cells may be hooked together to form various kinds of junctions f) Cell-cell recognition – proteins with short chains of sugars serve as ID tags

15. Each solute will diffuse down its own concentration gradient Membrane -permeable to dye molecules, diffuse down their concentration gradient; at equilibrium molecules are still restless, but rate of transport is equal in both directions Fig 5.12

16. Membrane - separates 2 solutions with different sugar concentrations Water can pass through the membrane, but not sugar molecules Osmosis, the passive transport of water across the membrane, reduces the difference in sugar concentrations and changes the solution volumes Fig 5.13

17. Figure 5.14 Animal and plant cells in different osmotic environments

18. Active Transport Figure 5.16 • Transport proteins -specific in recognition of atoms or molecules • Transport protein - binding site accepts only a certain solute • ATP energy - pumps the solute against its concentraction gradient

19. Figure 5.17a

20. Takes material into the cell within vesicles that bud inward from the PM Figure 5.17b

21. Phagocytosis An amoeba uses a pseudopodium (cellular extension) to engulf food and package it into a food vacuole. A similar process is used by WBCs of your immune system to destroy invaders Figure 5.18

22. Cholesterol Uptake • Cholesterol circulates in the blood in low-density lipoproteins (LDLs) • Proteins embedded in LDLs attach to receptor proteins in liver cell PMs – enables liver cells to take up LDLs and process the cholesterol Fig 5.19

23. Runner ‘psyched up’ for a race- adrenal gland cells secrete epinephrine into the bloodstream • Signal reaches muscle cells and is recognized by PM receptor proteins • Triggers responses (glycogen into glucose) without the hormone ever entering the cell Figure 5.20

24. Chapter 6 Review

25. Questions 1. Although they are ‘self-feeders’ photosynthetic autotrophs are not totally self-sufficient. What chemical ingredients do they require from the environment in order to synthesize sugar? 2. Why are plants called producers? Why are animals called consumers? 3. What is misleading about “plants perform photosynthesis, whereas animals perform cellular respiration.” 4. How is your breathing related to your cellular respiration?

26. Answers 1. CO2 and H20 2. Plants produce organic molecules by photosynthesis. Consumers must acquire organic material by consuming it rather than making it. 3. Cellular respiration does also occur in plants. 4. In breathing, your lungs exchange CO2 and O2 between your body and the atmosphere. In cellular respiration, your cells consume the O2 in extracting energy from food and release CO2 as a waste product.

27. Questions 5. At the ‘downhill’ end of the ETC, when electrons from NADH are finally passed to oxygen, what waste product of cellular respiration is produced? 6. What is the potential energy source that drives ATP production by ATP synthase? 7. Of the 3 main stages of cellular respiration which one uses oxygen directly to extract chemical energy from organic compounds. 8. The oxidation of acetic acid by NAD+ extracts some chemical energy from the acetic acid. How can the cell harness that energy to make ATP

28. Answers 5. Water (H2O) 6. Concentration gradient of H+ across the inner membrane of a mitochondrion. 7. Electron transport 8. NADH can supply electrons to the ETC, which generates an H+ gradient that drives ATP synthesis.

29. Questions 9. Of the 3 stages of cellular respiration, which occurs in the cytosol, outside mitochondria? Which produces the most ATP molecules per glucose. 10. How many molecules of ATP are generated per molecule of glucose during fermentation? How many are generated during cellular respiration? 11. ___ acid is to human muscle cells as ethyl ___ is to yeast. 12. In glycolysis, ___ is oxidized and ___ is reduced. 13. The final electron acceptor of ETCs in mitochondria is ___.

30. Answers 9. Glycolysis; ETC 10. 2; up to 38 11. lactose; alcohol 12. glucose; NAD+ 13. oxygen (O2)

31. Energy flow and chemical cycling in ecosystems • Energy enters as sunlight - exits in the form of heat • Organisms temporarily trap the energy for their work • Photosynthesis in chloroplasts of plants convert light energy to chemical energy • Cellular respiration in the mitochondria harvest the food energy to generate ATP • ATP drives most cellular work • Chemical elements essential for life recycle between cellular respiration and photosynthesis Figure 6.3

32. Figure 6.4

33. The Overall Equation for Cellular Respiration • A common fuel molecule for cellular respiration is glucose – a process that can produce up to 38 ATP per glucose molecule

34. When hydrogen and its bonding electrons change partners, from sugar to oxygen, energy is released Unnumbered Figure 6.2

35. A rapid electron ‘fall’ is an all-at-once redox reaction • Reaction of H2 and O2 to form water, releases a burst of energy Figure 6.5

36. Role of oxygen • NADH transfers electrons from food to an e- transport chain • O2 pulls the e- s down the chain • Cells use the stepwise release of energy to make ATP • O2 combine with e- and H from food to produce water Figure 6.6

37. A Road Map for Cellular Respiration Figure 6.14

38. Enzymes split glucose to form 2 pyruvic acid • Energy is stored as ATP and NADH some ATP is used to get glycolysis started • Enzymes attach P groups to fuel molecules during energy investment phase • Glycolysis generates some ATP directly, but also donates high-energy e- to NAD+ to form NADH Figure 6.8

39. ATP synthesis by direct phosphate transfer Glycolysis generates ATP when enzymes transfer phosphate groups directly from fuel molecules to ADP Figure 6.9

40. Link between glycolysis and the CAC- conversion of pyruvic acid to acetyl CoA: 1) each pyruvic acid loses a carbon as CO2 (remaining fuel molecules, each with 2 carbons are acetic acid) 2) oxidation of the fuel generates NADH 3) acetic acid is attached to coenzyme A to form acetyl CoA (CoA escorts acetic acid into the 1st reaction of the CAC) Figure 6.10

41. 1) Acetic acid joins a 4-C acceptor molecule to form a 6-C product called citric acid; for every acetic acid molecule that enters the cycle as fuel, 2) 2 CO2 molecules exit as waste; CAC harvests energy from the fuel, 3) some of the fuel is used to produce ATP directly; 4) most is trapped by NADH; 5) some energy is captured by FADH2 (an e- carrier); 6) all the C atoms that entered the cycle as fuel are accounted for as CO2 4-C acceptor molecule recycled Figure 6.11

42. 1) NADH transfers electrons from food to ETCs; 2) ETCs use this energy supply to pump H+ across the inner membrane of the mitochondrion; the infoldings of the inner membrane increase surface area, maximizing the number of ETCs built into the membrane 3) O2 you breathe pulls electrons down the ETC (cyanide and CO inhibit this step). 4) H+ flows back through an ATP synthase, spinning it like a turbine 5) ATP synthase uses the energy of the H+ gradient to regenerate ATP from ADP Figure 6.12

43. Monomers from carbohydrates, fats, and proteins can all serve as fuel for cellular respiration Figure 6.13

44. Figure 6.15a Glycolysis produces ATP without O2. This requires a continuous supply of NAD+ to accept electrons from glucose. The NAD+ is regenerated when NADH transfers the electrons it removed from food to pyruvic acid, thereby producing a) lactic acid or b) ethyl alcohol

45. Figure 6.15b

46. Chapter 7 Review

47. Questions 1. For chloroplasts to produce sugar from CO2 in the dark, they would require an artificial supply of the molecules ____ and ____. 2. What are the primary inputs and outputs of the Calvin cycle? 3. Why are leaves green? 4. Why is water required as a reactant in photosynthesis? 5. In addition to conveying electrons from the water-splitting photosystem to the NADPH-producing photosystem, the ETCs of chloroplasts also provide the energy for the synthesis of _____.

48. Answers 1. ATP; NADPH 2. Inputs: CO2, ATP, NADPH; output: glucose 3. Chloroplast pigments selectively absorb most wavelengths of light, but green light is reflected 4. It is the splitting of water that provides electrons for converting CO2 to sugar (via electron transfer by NADPH) 5. ATP

49. Questions 6. In terms of the spatial organization of photo-synthesis within the chloroplast, what advantage is it for light reactions producing NADPH and ATP on the stroma side of the thylakoid membrane? 7. What is the function of NADPH in the Calvin cycle? 8. How do special enzymes enable C4 and CAM plants to conserve water during photosynthesis 9. How might the combustion of fossil fuels and wood be contributing to global warming? 10. Light reactions take place in the chloroplast region called the __,while the Calvin cycle takes place in __

50. Answers 6. The Calvin cycle which consumes the NADPH and ATP, occurs in the stroma. 7. It provides the high-energy electrons that are added to CO2 to form sugar. 8. By allowing photosynthesis to continue even when stomata are closed during dry conditions. 9. By raising concentrations of atmospheric CO2 and increasing the greenhouse effect. 10. thylakoid; stroma