Download - Cellular Respiration
Chapter 9
All energy ultimately comes from the sun
Energy flows into an ecosystem as sunlight and leaves as heat
Chemical components are recycled
Energy is released from the transfer of e-’sOxidation is a loss of (hydrogen) e-’sReduction is a gain of (hydrogen) e-’s
Reduce (+) charge of an atom by adding a (-) charge e-
LEO goes GER or OIL RIG
Always occur together
Organic molecules have high abundance of hydrogen Energy released as O2 oxidizes (accepts e-’s
from) H2
e-’s travel with a proton (hydrogen atom) PE lost as e-’s ‘fall’ down an energy
gradient (move towards more EN molecule) Lower energy state from less complex
molecules Enzymes needed to facilitate in animals
because of energy of activation (EA)
Glucose (C6H12O6) is oxidized during cellular respiration
Occurs in steps to effectively access and use energy (avoids explosions)
e-’s transferred to an electron carrier, not directly to O2
Coenzyme NAD+ as an oxidizing agent (e-
acceptor)Dehydrogenase removes a pair of hydrogen
atoms (2 e-’s and 2 protons)
With no intermediates reaction = explosion Little PE lost with e- transfer to NAD+
Each NADH stores energy for ‘fall’ to O2 (final e- acceptor)
Electron transport chain, proteins within inner mitochondrial membrane, controls Each carrier more EN than previous
3 metabolic stagesGlycolysis: in cytosol, breaks down glucose into
pyruvateCitric acid cycle: in mitochondrial matrix,
oxidizes pyruvate to create CO2
Oxidative phosphorylation: mitochondrial matrix, e-’s to O2 and H+ = H2O and synthesizes ATP
Makes 36-38 ATP Glucoses stores 686 kcal/mol of energy in bonds ATP has 7.3 kcal/mol Single, large unit of energy broken into smaller,
more usable forms
Glucose (6C) 2 pyruvate (3C)No CO2 released
Substrate-level phosphorylation
Can occur with or without O2
O2 needed for citric acid cycle
No O2 then fermentation
Pyruvate (3C) acetyl-CoA (2C)High energy product so reacts
exergonicallyDecarboxylation is loss of CO2
‘Grooming’ for citric acid cycle
Within mitochondria
Intermediate steps Acetyl-CoA becomes
citrate CO2 and NADH leave as
number of carbons reduces to 4
FADH2 and an additional NADH leave
Oxaloacetate joins 2nd acetyl-CoA to reform citrate
Cycle repeats 2 turns per 1 glucose
Citrate(6 C’s)
Oxaloacetate(4C’s)
(2 C’s)
(4 C) molecule
Acetyl-CoA ATP + 3 NADH + FADH2 + CO2
2 processes = ETC and chemiosmosis within inner mitochondrial membrane
NADH and FADH2 store most energy till now Hydrogen concentration gradient setup Components are protein pumps
NADH and FADH2 bring e-’s to ETC complexOxidized when they lose e- to a lower neighbor
(higher EN) No direct ATP, control of energy release from
fuel to oxygen (final acceptor)Smaller, more manageable energy sources
FADH2 adds to lower energy levelProduce third less energy for ATP synthesis
Sets up a H+ concentration gradient
Energy stored as H+ gradient across a membrane drives cellular work
H+ ions pumped out by ETCSets up the gradient to drives ATP synthesis
ATP synthase is a protein complex that makes ATP from ADP and Pi
Endergonic reaction of ATP synthesis is coupled with exergonic ETC
C6H12O6 + 6O2 6H2O + 6CO2 + 36-38 ATP + heat1 NADH = 3 ATP1 FADH2 = 2 ATP
Anaerobic respirationETC, but O2 not final e- acceptor
Fermentation Primary purpose is to recycle NADH to NAD+
not ATP production Pyruvate picks up e-’s (reduced)
Glycolysis Occurs because NAD+ is oxidizer, not O2
NAD+ recycling NADH transfers e-’s to pyruvate to recycle NAD+
Alcohol fermentationPyruvate to ethanol
Lose CO2 then reduced by NADH In bacteria and yeast; makes bread, beer, and
wine
Lactic acid fermentationPyruvate directly by NADH to lactate
No CO2 released To make cheese and yogurt