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

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 → 2PGAL → 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

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

• Other metabolic pathways

• Versatility of catabolism

• Biosynthesis

FEEDBACK

MECHANISMS

CONTROL

CELLULAR RESPIRATION