Bio Chapter 7

How does Glucose Oxidation Release Energy?

when glucose is oxidized to CO2 through, combustion (in 1 step) - energy released as heat / light --- metabolism (in many steps) - energy released as heat / ATP--series of metabolic pathways catalyzed by enzymes --- multi-step chemical reactions involve e

How does Glucose Oxidation Release Energy?

Reactions 1 to 3 = Pi from ATP added to carbon 6 and carbon 1 of glucose to form fructose-1,6-bisphosphate/ Reactions 4 to 5= enzyme aldolase splits 6C molecule into two 3C molecules of G3P . Reaction 6= 2 NADH + H+ molecules produced by redox reaction. R

1. In general terms, distinguish between fermentation and cellular respiration

fermentation is anaerobic, cellular respiration is aerobic. Both use glycolysis as provider of starting material

2. Write the summary equation for cellular respiration

C6H12O6 + 6 O2 6 CO2 + 6 H20 + energy-

Define oxidation

- loss of electrons (e-) or H atoms (proton + electron) - exergonic - energy released

Definition reduction

- gain of electrons (e-) or H atoms (proton + electron) - endergonic - energy consumed

Explain in general terms how redox reactions are involved in energy exchanges

energy liberated by oxidation of reducing agent A (= e- donor) is captured in reduction of oxidizing agent B (= e- acceptor)

Describe the role of NAD+ in cellular respiration

coenzyme ---intermediate electron carrier= function of Nd = energy carrier. Oxidized form (NAD+) reduced form (NADH). Oxidation of NADH by O2 highky exergonic.

� 4.1 Glycolysis?

Glycolysis = "splitting of sugar" occurs in the cytoplasm of all cells---common to both anaerobic / aerobic pathways---provides starting materials for[ - fermentation (anaerobic)/- cellular respiration (aerobic)--- glycolysis releases energy by oxidizing

Who is using this metabolic pathway? -IN GLYCOLYSIS-

glucose

Where are reactions taking place? (IN GLYCOLYSIS)

first 5 endergonic reactions(Endergonic reactions coupled to Exergonic ATP hydrolysis overcome activation barrier ), last 5 exergoninc reactions (Exergonic reactions with ATP formed through substrate-level phosphorylation What is are reactants? (IN GLYCOL

3. What are products? (IN GLYCOLYSIS)

pyruvate (2 x 3 C), ATP (total of 4 produced), NADH + H+

5. What is happening to free energy levels? (IN GLYCOLYSIS)

increases, and then decreases which mean releases more energy from the glucose molecule

6. What is happening to ATP? (IN GLYCOLYSIS)

net gain of 2 'new' ATP / glucose molecule

7. What is happening to energy carriers (NAD+ / FAD)? (IN GLYCOLYSIS)

energy is transferred in redox reactions involving intermediate energy carriers like NAD+ and FAD

5. Describe how the carbon skeleton of glucose changes as it proceeds through glycolysis.

The starting molecule for glycolysis is the six-carbon molecule glucose, and its end product is a 3-carbon molecule, pyruvate. Two pyruvate molecules are produced for each glucose molecule that enters the pathway.

6. Explain why ATP is required for the preparatory (initial) steps of glycolysis

Endergonic reaction, required energy

7. Distinguish between the endergonic reactions and exergonic reactions of glycolysis

- first 5 reactions are endergonic (= energy consuming), - last 5 reactions are exergonic (= energy releasing)

8. Identify where substrate-level phosphorylation occurs in glycolysis. Identify where the reduction of NAD+ occurs in glycolysis

SUBSTRATE-LEVEL PHOSPHORYLATION for ATP synthesis = enzyme-catalyzed transfer of phosphate groups from substrate to ADP for ATP synthesis (Reactions 7 and 10 of Glycolysis)--- Pi added to substrates from ATP hydrolysis in endergonic reactions-- Pi is tran

9. Explain why pyruvate is considered a "key decision point" in energy metabolism

Fate of pyruvate depends on availability of oxygen= Much more ATP from complete oxidation of glucose ---Aerobic=shuttles carry NADH into mitochondria; pyruvate can be oxidized to Acetyl CoA and enter TCA�or Anaerobic: pyruvate reduced by NADH to lactate,

� What are the Anaerobic Pathways?

the production of ATP in absence of O2 by recycling using redox reactions which occurs in the cytoplasm of O2-deprived cells

� 10. State the basic function of fermentation.

derive energy from glycolysis and fermentation through partial oxidation of glucose. re-generates energy carrier NAD+ for glycolysis reactions anaerobically oxidize NADH + H+ from glycolysis to NAD+ for re-use in subsequent glycolysis while reducing pyruv

11. Compare the fate of pyruvate in alcohol fermentation and in lactic acid fermentation

Both energy does not change. Both use are reactants = - pyruvate (3 C) from Glycolysis, - NADH + H+ from Glycolysis. LACTIC ACID fermemtation produces - lactate (3 C) & NAD+. Alcoholic fermentation produces= ethanol (2 C), CO2 , NAD+

What are the Aerobic Pathways?

in presence of O2, Cellular respiration permits complete oxidation of glucose to energy trapped in ATP

12. Name the 3 stages of cellular respiration and state location where pathways occur in cells:

1 pyruvate oxidation= link between Glycolysis and Cellular Respiration occurs only in aerobic pathway occurs in inner mitochondrial membrane (in eukaryotes) occurs in inner plasma membrane (in prokaryotes)/ 2. . Citric Acid Cycle = Krebs Cycle/Tricarboxyl

� 13. Describe where pyruvate is oxidized to acetyl CoA, what molecules are produced, and how this process links glycolysis to the citric acid cycle

occurs in inner mitochondrial membrane (matrix) (in eukaryotes) / occurs in inner plasma membrane (in prokaryotes). multistep reaction catalyzed by an enzyme complex called Pyruvate Dehydrogenase Complex enzyme complex attached to inner mitochondrial memb

- 14. List the products of the citric acid cycle. Explain why it is called a cycle

products = CO2 (2 X 1C per acetyl-CoA. ----NADH + H+ (6 molecules / glucose molecule) --- FADH2 (2 molecules / glucose molecule). It is called citric acid because energy in acetyl CoA (2C) drives reaction of acetate (2C) with oxaloacetate (4C) to produce

15. Describe the point at which glucose is completely oxidized during cellular respiration

glucose is completely oxidized when all the energy is transfer to the 6 NADH & 2 FADH2

� How does Glucose Oxidation Form ATP?

re-cycling process involving electron transfer - oxidizes reduced energy carriers (NADH + H+ / FADH2)

� 16. Explain the role of the electron transport chain in cellular respiration

ATP produced (total of 28 molecules Produced 28 out of the 32 ATP in cellular respiration

17. Explain how the exergonic "slide" of electrons down the electron transport chain is coupled to the endergonic production of ATP by chemiosmosis

involves - 4 large proteins small protein (cyt c) - non-protein = ubiquinone (Q)/ free energy level decreases through ETC/ free energy stored in ATP/ excess electrons accepted by O2 forming H2O.

� 18. Explain where and how the respiratory electron transport chain creates a proton gradient

active transport of H+ out of matrix (against gradient) - creates concentration / charge gradient. couples proton transport to oxidative phosphorylation (reaction). as the electrons move along the respiratory ETC - electrons lose energy - energy captured

19. Distinguish between substrate-level phosphorylation and oxidative phosphorylation

OXIDATIVE PHOSPHORYLATION= PMF causes protons to diffuse back into mitochondrial matrix through membrane channel protein (= ATP synthase) that couples facilitated diffusion to ATP production. substrate-level phosphorylation = direct synthesis of ATP by di

Why does Cellular Respiration Yield More Energy than Fermentation?

End Products of partial oxidation of glucose through anaerobic fermentation still contain unused energy so only small amount of ATP produced NET = 2 ATP / glucose. End Products of complete oxidation of glucose through aerobic cellular respiration converts