Glycolysis, Kreb’s, and ETC Cellular Respiration
Jan 02, 2016
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 C3H6O6
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 CycleFigure 9.6 Homework
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