CELLULAR RESPIRATIONand FERMENTATION

Energy Harvest Fermentation – partial breakdown w/o

oxygen Cellular Respiration – most efficient,

oxygen consumed, mitochondria Cells recycle ATP Redox reactions (oil/rig); reducing agent –

electron donor; oxidizing agent – acceptor Cell Resp: glucose oxidized – H removed;

oxygen reduced – accepts H

ATP – adenosine triphosphate

ATP CYCLEATP + H20↔ ADP + Pi + energy

Energy flow and chemical recycling in ecosystems

NAD+ electron shuttle

Nicotinamide adenine dinucleotide

Coenzyme, oxidizing agent, reduced form NADH

NADH shuttles electrons to ETC

ETC – proteins, cytochromes in cristae, series of smaller steps, stores released energy to make ATP, oxygen combines w/ electrons and proton

Glycolysisglucose pyruvate; cytosol

Krebs cyclemitochondrial matrix, pyruvate acetyl CoA

& CO2

PHOSPHORYLATION

• OXIDATIVE – ATP synthesis powered by redox

reactions– Electron transport chain– Requires oxygen (final electron acceptor)

• SUBSTRATE LEVEL– ATP synthesis from transfer of phosphate

group from substrate to ADP– Glycolysis and Krebs cycle

Substrate level Phosphorylationin glycolysis

GLYCOLYSIS

• Splitting of glucose

• C6H12O6 → 2 C3H3O3

• Uses 2 ATP’s

• Makes 4 ATP’s

• Net 2 ATP’s

• 2 NADH & 2 H+

← SUMMARY

GLYCOLYSIS

Glucose → 2G3P → 2 PGA → 2 pyruvates ↑ ↑ ↑ requires 2 NAD+

generates 2 ATP’s reduced 4 ATP’s

2 NADH

Oxidation of Pyruvate•Occurs in mitochondrion, requires transport protein & coenzyme A•Yields Acetyl CoA, 1 NADH & 1 H+

from each pyruvate (2 total)•Waste – carbon dioxide

KREBS CYCLE Occurs in mitochondrial

matrix

1 cycle/pyruvate 2 cycles/glucose

Acetyl CoA (2-C) + oxaloacetate (4-C) → citrate (6-C)

7 more steps: 2CO2 removed, 3NADH & H+, 1FADH2

1 ATP – substrate phosphorylation

Oxaloacetate4-C

Citrate6-C

ELECTRON TRANSPORT

Cristae of mitochondrion – foldings ↑ surface area

Electron carriers (proteins) embedded in membrane

NADH “delivers” electrons to first molecule in chain (3 ATP’s); FADH2 adds electrons at lower level (2 ATP’s)

Last cytochrome passes electrons to ½O2 + H2 → H2O

CHEMIOSMOSIS Energy coupling ATP synthase

Generates ATP Molecular mill Powered by proton flow

Uses exergonic flow of electrons to pump H+ (protons) from matrix into intermembrane space, they flow back through ATP synthase

H+ gradient couples redox reactions of ETC to ATP synthesis

SUMMARY

FERMENTATION

Anaerobic glycolysis followed by break down of pyruvates

Substrate level phosphorylation Regenerates NAD+ from NADH Alcoholic: yeast, bacteria, produces – 2 ATP, 2

CO2 & 2 ethanol from pyruvates Lactic acid: fungi, human muscle cells, bacteria,

produces – 2 ATP & 2 lactates from pyruvate Acetic acid: bacteria, 2 ATP, 2 CO2 & 2 acetic

acids from pyruvates

Fermentation vs Respiration

Both oxidize glucose in glycolysis Pyruvate & 2 ATP’s NAD+ accepts electrons

Key difference: Oxidation of NADH (NAD+ required to

sustain glycolysis) Final e- acceptor (organic molecule vs

O2) 2 ATP’s vs 38 ATP’s

Facultative anaerobes

•Yeast•Bacteria•Human muscle cells

Evolutionary significance of glycolysis?

Other metabolic pathways

Versatility of catabolism Biosynthesis Anabolic pathways may

use intermediates & consume ATP

FEEDBACK

MECHANISMS

CONTROL

CELLULAR RESPIRATION