Cellular Respiration - Lecture notes 9 PDF

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Lecture 9: Cellular Respiration October 1, 2019 During:

I.

I.

Introduction → SEQ, HD general respiration processes and pathway

II.

4 Stages → CC, SEQ, HD steps of respiration

Intro to Cellular Respiration A. Overview of Eukaryotic Respiration

carbs simple sugars proteins → amino acids → bloodstream → cells fats fatty acids

1. Cannot yet do cellular work

2. Respiration: a) E in chem bonds of food → E in ATP (can be used) b) Occurs in all cells c) Aerobic or anaerobic d) Catabolic

3. Review: Redox Reactions a) Start with glucose (1) Low oxidation state (C bound to H and O) b) End with carbon dioxide (1) Highly oxidized (C has given up e-) c) This is combustion, but will be done very slowly

4. Respiration is a series of redox reactions Г becomes oxidized Xe- + Y → X + Ye becomes reduced ↑ Glucose (6 carbon sugar) → 6x CO 2 (1C gas)

H

| C |

OH + NAD+

dehydrogenase ------------------>

| C = O + NADH + H+ |

5. Summary of Metabolic Pathway a) C6H 12O6 + 6O2 → 6CO 2 + 6H 2 O + E (1) Reverse of photosynthesis (2) Exergonic → E released

II.

4 Stages of Respiration -

We Will Follow 1 Glucose - Last last time… - Count carbons - Note ATP production - Follow E stored as e - in e - carriers

A. Glycolysis 1. “Sugar splitting” — break down glucose 2. 1 glucose (6C) → 2 pyruvate (3C) 3. Does not require O 2 4. Occurs in cytoplasm 5. 2 phases: a) E investment - uses ATP b) E payoff - makes ATP 6. Energy Investment Phase a) Endergonic → requires ATP b) 6C → P-6C-P → 2 x 3C-P (G3P)

7. Energy Payoff Phase a) Exergonic → generates ATP and NADH b) Each G3P → P-3C-P → 3C (Pyruvate) 8. ATP Synthesis in Glycolysis a) Via substrate-level phosphorylation b) Enzymatic transfer of phosphate to ADP → ATP 9. Glycolysis Summary a) Start: 1 glucose b) End: 2 pyruvate c) Get: 2 ATP, 2 NADH d) After glycolysis: (1) Aerobic: (a) Pyruvate oxidation (2) Anaerobic: (a) Fermentation B. Pyruvate Oxidation 1. Takes place inside mitochondria 2. Pyruvate Import a) Diffuses through pores in outer membrane b) Active transport across inner membrane 3. Pyruvate Oxidation Reaction a) Catalyzed by pyruvate dehydrogenase (BIG enzyme) b) No ATP used or produced c) 2x per glucose d) Pyruvate + NAD + + CoA → CO 2 + NADH + Acetyl CoA e) By end of this step, 2 of original 6 C released as CO 2

4. So far…

Glycolysis: Pyruvate Oxidation: Net gain: ATP, NADH

IN

OUT

ATP

ATP

—

NADH, CO 2

C. Citric Acid Cycle 1. Takes place in matrix of mitochondria 2. Starts with acetyl-CoA (from pyruvate oxidation) and oxaloacetate (4C) 3. 8 steps, but we will simplify 4. Citric Acid Cycle, Simplified

5. Citric Acid Cycle Summary a) Acetyl-CoA completely oxidized to CO 2 b) 1 glucose → 2 “turns” c) Each turn generates: (1) 2 CO 2 (2) ATP (indirectly!) (3) NADH (4) FADH 2 d) Each glucose generates: (1) 4 CO 2 (2) ATP (indirectly!) (3) NADH (4) FADH 2

6. After Citric Acid Cycle For 1 Glucose IN

OUT

2 ATP

2 ATP 2 NADH

Pyruvate → Pyruvate Oxidation:

—

2 NADH 2 CO2

Acetyl-CoA → Citric Acid Cycle

—

2 ATP 6 NADH 2 FADH 2 4 CO2

Glucose → Glycolysis:

Net gain: ATP, NADH, FADH 2 , 6 CO 2

D. Oxidative Phosphorylation (Electron Transport Chain and Chemiosmosis) 1. Energy stored in NADH and FADH 2 used to create a proton gradient 2. Proton diffusion across inner membrane (chemiosmosis) drives ATP synthesis 3. Electron Transport Chain (ETC) a) Series of e - carriers — inner mitochondrial membrane b) Series of redox reactions c) e- from electron carriers → through ETC → O 2 d) E used to make H + gradient via active transport e) Intermembrane space [H +] > matrix [H+] 4. O 2 is Terminal e - Acceptor Г

becomes oxidized

C6 H12 O6 +

6 O2

→ 6 CO 2 +

6 H 2O

becomes reduced a) This is why we need oxygen b) What’s the point? (1) Proton gradient

↑

+ Energy

5. ETC Energy a) ETC and “slow combustion” of glucose have the same purpose: minimize E lost as heat 6. Chemiosmosis a) E coupling mechanism used to synthesize ATP b) Convert potential E in gradient (proton motive force) to potential E in ATP 7. ATP Synthase a) Protein complex b) Inner mitochondrial membrane c) “Molecular mill” d) H+ diffuse through (exergonic) → causes rotation → E for ATP synthesis 8. ATP Production by Oxidative Phosphorylation a) Glucose → NADH or FADH 2 → ETC → PMF → ATP b) Each NADH: (1) In matrix: 2.5 ATP (2) From cytosol: 1.5-2.5 ATP c) Each FADH2 : (1) In matrix: 1.5 ATP 9. Prokaryotic Respiration a) Same stages as eukaryotes b) No mitochondria → Aerobic respiration in cytosol c) ETC in plasma membrane d) e- carriers don’t need to cross membranes → more ATP 10. Respiration Summary Glucose (6C) → Pyruvate (2x3C) → Acetyl-CoA (2x2C) + CO 2 (2x1C) → CO2 (4x1C) a) E stored in e - (NADH, FADH2 ) b) Used to make H + gradient c) Most ATP via chemiosmosis 11. Big Picture a) Photosynthesis: 6 CO2 + 6 H 2O + E → C 6 H12O 6 + 6 O2 b) Respiration: C6H 12O6 + 6 O 2 → 6 CO 2 + 6 H2 O + E...