Glycolysis, Kreb’s, and ETC

Cellular Respiration

Cellular Respiration How our body turns food and oxygen into

ENERGY called ATP

GlycolysisKreb’s CycleETC (Electron Transport Chain)

Redox ReactionsChemistry review:Oxidation = losing an electronReduction = gaining an electronA redox reaction is a chemical reaction in

which one molecule gains electrons and one loses them

Example of cellular respiration: glucose is oxidized into carbon dioxide, oxygen is reduced to water

GlycolysisGlycolysis is the first step of cellular

respirationIt means “splitting sugar”One molecule of glucose is split in half into

2 molecules of pyruvic acid (pyruvate)C6H12O6 2 C3H6O3

GlycolysisOccurs in the

cytoplasm of cellsIt is a 10 step process

that occurs in 2 phases

It can occur whether or not oxygen is present

GlycolysisInput: glucoseOutput: 2 molecules of

pyruvate, 2 ATP, and 2 NADH

NADH is a molecule that carries electrons from glycolysis and the Kreb’s Cycle to the ETS (it gains electrons = reduced)

Once there, it releases the electrons to make ATP (it is oxidized to NAD+)

Kreb’s CycleStep 2 of Cellular Respiration is called the

Kreb’s Cycle, and is also known as the Citric Acid Cycle

It ONLY occurs in the presence of oxygenIt takes place in the mitochondrial matrix,

the space between the inner folded membranes of the mitochondria

Kreb’s CycleThe 2 pyruvates from glycolysis are converted

to 2 molecules of acetyl coenzyme A (acetyl coA)

This enters the Kreb’s Cycle one at a time.For each original glucose molecule, the Kreb’s

Cycle will spin twice, one for each acetyl coA

Kreb’s Cycle

Kreb’s CycleAcetyl coA undergoes a series of redox

reactions in the Kreb’s cycle, rearranging its formula and transferring electrons

The net output for 2 TURNS of Kreb’s is: 6 NADH, 2 FADH2 (another electron carrier), and 2 ATP

A byproduct, carbon dioxide, is released

Electron Transport ChainThe last step is called the electron

transport chain (ETC) or system (ETS), or oxidative phosphorylation (means losing electrons and adding a phosphate group to ADP to make ATP)

It occurs in the cristae of the mitochondria, on the membranes on the inside

ETCThe NADH and FADH2 molecules made in

glycolysis and Kreb’s are what are used by the ETC to make ATP

ETCThe ETC is a series of

proteins embedded in the cristae like a waterfall

NADH and FADH2 enter the highest protein, and as they “fall” down the waterfall, they pass their electrons down to more electronegative carriers

As this occurs, hydrogen ions (H+), which have lost their electrons, are pumped to the outside of the membrane

ETCAt the end of the chain,

there is a big protein enzyme called ATP Synthase

The H+ ions flow down their concentration gradient through ATP synthase

ATP synthase spins around each time and generates enough energy to add a P to ADP, making ATP

ETC As ADP is getting phosphorylized (called chemiosmosis), the electrons

have reached the bottom of the waterfall The electrons are attracted to a super electronegative atom, oxygen Oxygen is the final electron acceptor. It gains electrons (is reduced)

and joins with the H+ ions coming through ATP synthase to make water

We breathe out the water (along with the CO2 from Kreb’s)

ETCAt the end of the ETC, approximately 34

ATP are generated through the processes of Oxidative Phosphorylation (the electrons moving down the waterfall) and chemiosmosis (the diffusion of H+ ions through ATP synthase)

SummaryOxygen we breathe in becomes waterGlucose we eat is used to make ATP and

CO2 (waste)A total of approximately 38 ATP are made

per glucose molecule