CELLULAR RESPIRATION and FERMENTATION. Energy Harvest Fermentation – partial breakdown w/o oxygen...
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Transcript of CELLULAR RESPIRATION and FERMENTATION. Energy Harvest Fermentation – partial breakdown w/o oxygen...
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