Exam next Friday Proposal: –60 point 4 th exam over chapters 10 (Lipids), 11 (Membranes), 13...

Exam next Friday

• Proposal: – 60 point 4th exam over chapters 10 (Lipids),

11 (Membranes), 13 (Bioenergetics (ATP & redox)

– 140 point final: ~40 points new stuff (general concepts in glycolysis, TCA, electron transport), ~100 points “comprehensive”

– Review sheet (4th exam) this weekend– Review for 4th exam on Tuesday(?)– Review for final ~ couple of days next week

Nutrients:Fats/Carbohydrates/Proteins (highly reduced compounds)

Usable (bioavailable) chemical energy:ATP (other phosphorylated cpds), reducing agents (eg. NADH)

Glycolysis, TCA/Krebs cycle Breakdown of nutrients Harvesting of energy as (some) ATP, lots of reducing power (NADH)

Oxidative phosphorylation (Electron transport) Harvesting of energy from reducing agents Generation of (lots of) ATP

Aerobic respiration of glucose (etc)

• Glycolysis: – Start with glucose (6 carbon)– Generate some ATP, some NADH, pyruvate (2 x 3 carbon)

• TCA cycle– Start with pyruvate– Generate acetate– Generate CO2 and reduced NADH and FADH2

• Electron transport – Start with NADH/FADH2

– Generate electrochemical H+ gradient• Oxidative phosphorylation

– Start with H+ gradient and O2 (and ADP + Pi)– Generate ATP and H2O

Glycolysis• Pathway for D-glucose

degradation• Generation of pyruvate• Anerobic (no O2 required)

– Occurs in most every living cell– Eukaryotes→ in cytosol

• Pyruvate has different fates– Aerobic→CO2→ ATP– Anerobic

• Fermentation to EtOH• Fermentation to lactate

Glycolysis

• 5 step preparatory phase– Energy requiring– 2 ATP invested

1. Phosphorylation

2. Isomerization

3. Phosphorylation

4. Cleavage

5. Isomerization

Why phosphorylation?

1. Coupled transfer of phosphate to/from ATP

2. Intermediates “trapped” within the cell• Energy required to keep ‘naked’ glucose in the cell

(vs. chemical gradient)• Phosphate groups (neg charge) easily retained

3. Binding energy • Enzymes take advantage of negative charge to

increase affinity/specificity

Glycolysis• 5 step payoff phase

– 4 ATP generated (net 2 gained)

– 2 NADH gained– 2 pyruvate– Series of oxidation

and phosphorylation steps

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Step 1: Glucose phosphorylation by hexokinase

Step 2: Conversion to Fructose-6-P

Step 3:Phosphorylation to F-1,6-bisP

phosphofructokinase

*Committed step*Regulatory enzyme

Step 4: Cleavage of F-1,6-bP

6 carbon sugar →Two 3 carbon sugars (triose phosphates)

Step 5: isomerization of dihydroxyacetone

Both 3 carbon sugars arenow the same(glyceraldehyde 3-P)

“Payoff phase”Step 6: oxidation

(phosphorylation) of G-3-P

Step 7: ATP formation

Steps 6 & 7

Overall: transfer of Pi from glyceraldehyde 3-P to ATP with1,3-BPG as an intermediate

“Substrate-level phosphorylation”

Step 8: Rearrangement to 2-phosphoglycerate

Step 9: Dehydration of 2-phosphoglycerate to PEP

Step 10: Phosphoryl transfer to ADP