Lecture 6 Outline (Ch. 9)

I. Overview of Respiration

II. Redox Reactions

III. Steps of Respiration

IV. Cellular Respiration

A. Glycolysis

B. Coenzyme Junction

C. Citric Acid Cycle (aka Krebs/TCA cycle)

D. Electron Transport Chain (ETC)

E. Chemiosmosis

V. Anaerobic respiration

VI. Respiration using other biomolecules

VII. Lecture Concepts

Cellular Respiration

Overall purpose:

• convert fuels to energy

• animals AND plants

• complementary to photosynthesis

Cellular Respiration:(Exergonic)

Cellular Respiration

• catabolizes sugars to CO2

• requires O2

• at mitochondrion

Redox Reactions

• as part of chemical reaction, e- are transferred

• e- transfer = basis of REDOX reactions(reduction) (oxidation)

Redox Reactions

• follow the H, e- w/them

Redox Reactions

Equation for respiration

• transfer of e- to oxygen is stepwise

Redox Reactions

• e- moved by NAD+ (niacin)

• when “carrying” e- (& H+), NADH

Where do e- come from?

• gained e- (& H+), reduced

• food (glucose)

Where do e- go?

• glucose NADH ETC O2 (H2O)

Redox Reactions

1. glycolysis

- cytosol

- mitochondrial matrix

- inner mitochondrial membrane

• Steps of respiration:

2. Citric acid cycle

3. ETC

4. Chemiosmosis - inner membrane to intermembrane space

Steps of Respiration

Coenzyme Junction

• Stages of respiration:

1. Glycolysis – prep carbons

Cellular Respiration

1. Glycolysis

• 1 glucose (6C) 2 pyruvate (3C)

• key points: - inputs

- NAD+/NADH

- ATP

Cellular Respiration

- CO2 and H2O

- outputs

• eukaryotes AND prokaryotes

-inputs:

CO2 none

2 H2O

-outputs:

1 Glucose

2 ATP

4 ATP (2 net)

2 NADH

2 pyruvate

Where do they go?

Glycolysis Cellular Respiration

Coenzyme Junction • 2 pyruvate (3C) 2 Acetyl CoA (2C)

Cellular Respiration

• pyruvate joins coenzyme A (vitamin B)

• 2 C lost (as CO2)

• 2 NAD+ NADH

Steps of Respiration

• Stages of respiration:

2. Citric acid cycle e- transfer: redox

Cellular Respiration

2. Citric acid cycle

• 2 Acetyl CoA (2C) join oxaloacetate (4C)

• few ATP so far

• e- to carriers

(NAD+, FAD)

• mitochondrial matrix

• 2 citrate (6C) converted several steps, 4C lost (CO2)

-inputs:

4 CO2

H2O none

-outputs:

2 Acetyl CoA (2C)

2 ATP

6 NADH

2 FADH2

[2 oxaloacetate (4C)]

Where do they go?

Citric acid cycle

Self-Check

Step of Respiration

Inputs Outputs CO2/H2O ATP produced

e- carriers loaded

Glycolysis 1 glucose 2 pyruvate 2H2O 2 net 2 NADH

Coenzyme Junction

Citric Acid Cycle

Electron Transport Chain

Oxidative phosphorylation

Fermentation

1. glycolysis

- cytosol

- mitochondrial matrix

- inner mitochondrial membrane

• Steps of respiration:

2. Citric acid cycle

3. ETC

4. Chemiosmosis - inner membrane to intermembrane space

Steps of Respiration

Coenzyme Junction

Steps of Respiration

• Stages of respiration:

3. ETC

Proton Motive Force

Substrate-level phosphorylation

Phosphate group moved from substrate to ADP yields ATP

Cellular Respiration

3. Electron transport chain (ETC)

• lots of energy harvested

• released in stages

• so far, 4 ATP – substrate P

• many ATP – oxidative phosphorylationoxidative phosphorylation

Cellular Respiration – mitochondria revisited

Cellular Respiration

• ETC e- collection molecules

• embedded on inner mitochondrial membrane

Electron transport chain (ETC)

• accept e- in turn

• e- ultimately accepted by O2

(O2 reduced to H2O)

~100 H+ (stored)

10 H2O

-outputs:

ATP (none yet)

Where do they go?

H+ build up in intermembrane space (potential energy)

Electron transport chain (ETC)

-inputs: per glucose,

10 NADH

2 FADH2

10 H+

Steps of Respiration

• Stages of respiration:

4. Chemiosmosis

ATP produced!

Cellular Respiration 4. Chemiosmosis

• ATP synthase: inner mitochondrial membrane

• energy input ATP – H+ gradient

• chemiosmosis – ion gradient to do work

Cellular Respiration

• Four parts to ATP synthase:

4. Chemiosmosis

• H+ must enter matrix here

Rotor, Stator, Rod, Knob

• Generates 1 ATP per ~3.4 H+

Cellular RespirationSummary of respiration

• Cells convert ~ 40% of energy in glucose to energy in ATP

• Most fuel efficient cars convert only ~ 25% of gasoline energy

Cellular Respiration - anaerobic

• no O2 – no oxidative phosphorylation

• fermentation

• extension of glycolysis

• substrate-level phosphorylation only

• need to regenerate e- carrier (NAD+)

Cellular Respiration - anaerobic

• Types of fermentation -

1. alcohol

• pyruvate converted to acetaldehyde

• acetaldehyde accepts e-

• ethanol produced

Cellular Respiration - anaerobic

• pyruvate accepts e-

• lactate produced

• Types of fermentation -

2. Lactic acid

Cellular Respiration - anaerobic

• inputs/outputs

• alcohol

• lactic acid

• pyruvate in

• CO2 and EtOH out

• pyruvate in

• lactate out

• brewing & baking

• muscle fatigue

Cellular Respiration

• pyruvate - junction

• O2 present – citric acid cycle

• O2 absent - fermentation

Self-Check

• Comparison of aerobic vs. anaerobic respiration:

• ATP made by:

• ATP per glucose:

Aerobic Anaerobic

• initial e- acceptor:

• final e- acceptor:

Cellular Respiration – other biomolecules

• Glucose catabolism – one option

• Proteins:

• Fats:

Catabolized into a.a.

– Enter diff. points – depends on a.a.

Glycerol in at glycolysis

- becomes pyruvate

Fatty acids in before CAC

- becomes Acetyl CoA

Amino group removed

Self-Check

Step of Respiration

Inputs Outputs CO2/H2O ATP produced

e- carriers loaded

Glycolysis 1 glucose 2 pyruvate 2H2O 2 net 2 NADH

Coenzyme Junction

Citric Acid Cycle

Electron Transport Chain

Oxidative phosphorylation

Fermentation

Lecture 6 concepts- Describe in words the purpose of cellular respiration

- Write the equation for cellular respiration

- Given an equation, particularly that for cellular respiration, determine which molecules are oxidized and reduced

- List the steps of cellular respiration and where they occur

- For glycolysis, coenzyme junction, and the citric acid cycle, give inputs, outputs, ATP made/used, e- carriers loaded, water and carbon dioxide molecules produced

- For the electron transport chain and chemiosmosis, give inputs, outputs, ATP made/used, e- carriers loaded, water and carbon dioxide molecules produced

- Keep track of the total number of carbon molecules going in and coming out for each step of respiration

- Compare substrate-level and oxidative phosphorylation

- Compare the e- carriers, final e- acceptors, and ATP made for aerobic respiration and anaerobic respiration

- Write out a list of new terminology and provide descriptions