3a; cellular respiration

Lecture 3a:Cellular Respiration

Lecture 3a:Cellular Respiration

Cellular Respiration

This is the reason you breathe

How cells make ATP from carbohydrates

Essentially the reverse of photosynthesis

Helper molecules

Coenzymes: nonprotein helpers that move electrons and H around

NAD+ and FAD+ become NADH and FADH

4 PhasesGlycolysis: Occurs in cytoplasm

Produces 2 ATP and NADH

Breaks glucose in half into 2 pyruvate

Prep reaction: Occurs in matrix

Produces NADH

Breaks pyruvate into 2-carbon acetyl group

Releases CO2

4 PhasesCitric acid cycle: occurs in matrix

Produces more NADH and FADH2

Releases CO2

Produces 2 ATP

Electron transport chain: Occurs in crista

NADH and FADH2 release electrons

Energy released

Produces water

Glycolysis

Occurs outside the mitochondria

Uses 2 ATP, but makes 4, so total gain of 2 ATP per glucose broken

Makes 2 pyruvate from 1 glucose

Preparatory Reaction

Occurs in matrix of mitochondria

Each pyruvate is broken into CO2 and C2 acetyl group, which binds to coenzyme A to produce acetyl CoA

NADH is produced

Citric Acid Cycle

Occurs in matrix of mitochondria

Acetyl CoA is oxidized to CO2

NADH and FADH2 are produced

ATP is produced

Electron transport chainOccurs in cristae of mitochondria

Series of carriers that pass electrons from one to the next

NADH and FADH2 are the sources of the electrons, but the chain does not accept the H+, only the e-

Final acceptor for electrons is the O2 that we breathe in!

Electron transport chain

Energy released as electrons move down the chain is used to make ATPs

NAD and FAD are recycled to be used again

Electron transport chainWhat about the H+?

The energy released by the ETC is used to pump H+ into the inter-membrane space, between inner and outer membranes of mitochondria

This creates a gradient- more H+ in inter-membrane space than in matrix

Electron transport chainLike in photosynthesis, this gradient results in potential energy that can be used

ATP synthase exists in cristae

H+ flows back into matrix through synthase, which makes ATP from the energy

Electron transport chain

Produces 34 ATP from each glucose that originally entered the cycle

ETC ATP plus ATP made earlier= 38 ATP per glucose

This is about 40% of energy in glucose, the rest is lost as heat

FermentationCellular respiration requires O2 as the final acceptor in the electron transport chain, but what if no O2 is available?

Pyruvate is reduced to make lactate, H+ comes from NADH

Only makes 2 ATP- what is the point?

Fermentation

Regeneration of NAD keeps glycolysis going, instead of stalling (=death)

Can create short bursts of energy

Why you are sore after strenuous work

Yeasts use fermentation and generate ethyl alcohol instead of lactate