Cellular Respiration

C6H12O6 + 6 O2 6 CO2 + 6H2O + 38 ATP

Cellular Respiration: An OverviewProcess by which cells convert the energy in

food (usually glucose) into usable ATP. Terms to Know…

Oxidation = the loss of electrons Compound becomes more positive

Reduction = the gain of electrons Compound becomes more negative

Electrons and protons (H+) travel TOGETHERNAD+ = coenzyme derived from niacin; acts

as a H+ and e- acceptor. AN ENERGY CARRIER!

Cellular Respiration: An Overview

Substrate-Level Phosphorylation

An enzyme transfers a phosphate group directly from an organic molecule to ADP to form ATP

The ATP produced in Glycolysis & the Krebs Cycle is produced by this method.

Oxidative Phosphorylation(ETC + Chemiosmosis) The production of ATP by using energy

derived from the redox reactions of the Electron Transport Chain.

The enzyme ATP synthase is needed to phosphorylate the ADP to produce ATP.

Almost 90% of the ATP produced from cellular respiration is produced this way.

Cellular RespirationGlucose

Anaerobic Respiration(Fermentation)

Aerobic Respiration(Krebs Cycle &

ETC)

Glycolysis

Oxygen Absent Oxygen Present

ATP

ATP

Glycolysis “glucose-splitting” Big Picture:

Glucose (6-C) is broken down into 2 molecules of pyruvate (3-C)

Occurs in the cytosol Occurs with or without oxygen Made up of 2 phases:

Energy investment phaseEnergy yielding phase

Glycolysis: Energy Investment Phase Glucose is converted

into 2 G3P (Glyceraldehyde-3-phosphate)

Requires 2 ATP

Glycolysis: Energy-Yielding Phase

2 G3P are converted into 2 Pyruvate (3C) molecules.

Dehydrogenase enzymes remove H from intermediate compounds and attach them to 2 NAD to produce 2NADH

Net Gain in Glycolysis

2 ATP- 2 ATP (Energy investment phase)+ 4 ATP (Energy yielding phase) + 2 ATP

2 NADHElectron carriersWill be used to make ATP later

Choices, Choices! If oxygen is absent, anaerobic respiration

occursFermentation

Yeast & some bacteria alcoholic fermentation Animal muscle lactic acid fermentation

If oxygen is present, aerobic respiration occursKrebs Cycle and Electron Transport Chain

Cellular RespirationGlucose

Anaerobic Respiration(Fermentation)

Aerobic Respiration

Glycolysis

Oxygen Absent Oxygen Present

ATP

ATP

Fermentation 2 major types:

Alcoholic and lactic acid fermentation NAD+ acts as a hydrogen acceptor during

glycolysis If the supply of NAD+ runs out, then glycolysis

would have to stop.Fermentation occurs as simply a means of

recycling the NAD+, so that glycolysis can occur again.

Alcoholic Fermentation Occurs in some BACTERIA and

YEAST 2 step process:

Carbon dioxide is released from pyruvate (3-C), forming acetaldehyde (2-C)

Acetaldehyde is reduced by NADH (gains an electron), forming ethyl alcohol (ethanol)

NAD+ is regenerated, thereby allowing glycolysis to continue

Used to produce beer and wine

Lactic Acid Fermentation Occurs in ANIMALS 1 step process:

Pyruvate is reduced by NADH (gains an electron), forming lactic acid

NAD+ is regenerated, thereby allowing glycolysis to continue

Occurs in muscle cells, causing muscle pain and fatigue

Cellular RespirationGlucose

Anaerobic Respiration(Fermentation)

Aerobic Respiration

Glycolysis

Oxygen Absent Oxygen Present

ATP

ATP

Aerobic Respiration After glycolysis, most of the

energy from glucose remains “locked” in 2 molecules of pyruvate

If oxygen is present, the pyruvate enters the mitochondrial matrix to complete the Krebs Cycle

Pyruvate (3-C) is converted to Acetyl CoA (2-C) CO2 is released as a

waste product NADH is produced

The Krebs Cycle Yield per pyruvate molecule:

4 NADH 1 FADH2 1 ATP 2 CO2

Yield per glucose molecule (two turns of Krebs Cycle): 8 NADH 2 FADH2 2 ATP 6 CO2

CO2 released as a waste product

Electron Transport Chain The ETC converts the NADH and FADH2

from glycolysis and the Krebs Cycle into ATP Occurs in inner membrane of mitochondrion The energy in each NADH molecule moves

enough protons (H+) into the mitochondrial matrix to create 3 ATP

1 FADH2 2 ATP

The Electron Transport Chain The electrons from NADH and FADH2 are

passed from one electron acceptor molecule to another.

Each electron acceptor is more electronegative than the last.

Oxygen is the final electron acceptore-

ETC

oxygen

Chemiosmosis Similarly to photosynthesis,

the energy the electrons lose along the way moves H+ out of the matrix and into the intermembrane space of the mitochondrion

As H+ ions diffuse through the membrane, ATP synthase uses the energy to join ADP and a phosphate group ATP

Oxidative Phosphorylation: ETC & Chemiosmosis

Aerobic Respiration: Total Energy Yield Glycolysis:

2 ATP (Net)2 NADH 6 ATP

Krebs Cycle:2 ATP8 NADH 24 ATP (ETC)2 FADH2 4 ATP (ETC)

TOTAL:8 ATP + 30 ATP 38 ATP