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