Cellular Respiration 7.1 Glycolysis and Fermentation 7.2 Aerobic Respiration

Cell Respiration Living cells constantly use energy for activities such as movement, protein synthesis, active transport and cell division. Most of the energy to power these processes comes from ATP. A cell must constantly replace ATP

The cell does this by breaking down organic food molecules The cell does this by breaking down organic food molecules. Releasing energy that is used to join ADP and phosphate to form ATP The breakdown of food to release energy occurs by 2 kinds of processes: 1. respiration 2. fermentation

Cell Respiration A fuel molecule such as glucose is oxidized to form carbon dioxide and water. Energy is captured through the formation of up to 36 to 38 ATPs per glucose molecule

It is the process by which cells extract fee energy from the energy stored in chemical bonds of food molecules (glucose) This is done in a series of catabolic pathways featuring redox reactions and using oxygen as the final electron acceptor

The energy released is used to regenerate the cell’s supply of ATP ATP donates the energy to various energy requiring processes such as metabolic reactions, active transport, muscle contractions, etc…

3 Metabolic stages of Cell Respiration 1.Glycolysis 2. Kreb Cycle 3. Oxidative phosphorylation

Mitochondria Site of cell respiration Most ATP production occurs here Parts of the Mitochondria: 1. Cristae: folds of mitochondria is where electron transport occurs 2. Matrix: open area of mitochondria, where kreb cycle occurs 3 Cytosol: outside mitochondria , where glycolysis occurs.

d. Outer membrane a. Matrix b. Cristae c. Inner membrane

ATP

Glycolysis Occurs in cytosol outside mitochondria Converts the 6-carbon glucose into 2 3-carbon pyruvic acid molecules 4 ATP are make, but due to a deficiency of 2 ATP, the step generates a positive 2 ATP If oxygen is present then the reaction proceeds to kreb cycle

If oxygen is absent, it will proceed to fermentation Fermentation occurs in the cytosol, has a net gain of 2 ATP per glucose and is only 2.1% efficient Between glycolysis and kreb cycle is a transition reaction in which pyruvate ( pyruvic acid) is converted to acetyl CoA and 2 CO2 are removed

Glycolysis Lactic Acid Fermentation Alcoholic Fermentation Krebs Cycle Electron Transport Chain

Kreb Cycle Is located within the mitochondria matrix Also called Citric acid cycle, or TCA Completes glucose oxidation by breaking down a pyruvic acid derivative (acetyl CoA) into carbon dioxide Is a circular sect of reactions because the reaction is ongoing, never reaching an endpoint.

Requires 2 turns of the kreb cycle per glucose ( each turn releasing 2 carbon dioxides, 3 NADH, 1 ATP, 1 FADH2 NADH and FADH2 are coenzymes (NAH accepts 2 electrons and 1 hydrogen while FAD accepts 2 electrons and 2 hydrogen)

Oxidative phosphorylation Accounts for most ATP produced during respiration (32 to 34) Includes electron transport chain made of electron carriers molecules built into the inner mitochondrial membrane Oxygen pulls energized electrons harvested during glycolysis and kreb cycle down the electron transport chain to a lower energy state.

This exergonic slide of electrons is coupled to ATP synthesis Electron transport accepts electrons from glucose during glycolysis and transition reaction and kreb cycle… usually NAD+ carries these electrons

The electrons then drop off the supply of energy needed to pump the hydrogen ions from the matrix to the intermembrane space of the mitochondria ( this is chemiosmosis) The NAD+ and Fad then return to pick up more hydrogen ( both reusable)

When NADH delivers electrons, it has enough energy to make 3 ATP. When FADH2 delivers electrons, it has enough energy to make 2 ATP Cytochrome: the molecule that helps with electron transport

Chemiosmosis: ability of some members to use hydrogen ion s gradient to drive ATP formation Oxidative phosphorylation: refers to the production of ATP as a result of energy released by electron transport system

Electron Transport Chain of Aerobic Respiration protons protons protons FADH2 NAD+ ADP + Phosphate O2

Electron Transport Chain of Aerobic Respiration protons protons protons FADH2 NAD+ ADP + Phosphate O2

Energy Yield of Aerobic Respiration – * One glucose can generate up to 38 ATP molecules. * 38 x 12 kcal divided by 686 kcal = 66 % efficiency. * About 20 times more efficient than glycolysis alone. * Note: a car engine is only about 25 % efficient.

http://www.sirinet.net/~jgjohnso/cellularresp.html

Photosynthesis and Cellular Respiration (opposite reactions) * The final products of plant photosynthesis (sugar and oxygen) are used by animals for the process called cellular respiration. The products of respiration are carbon dioxide and water, which plants need for photosynthesis. * Since photosynthesis and respiration are opposite processes, they form a cycle that keeps the levels of oxygen and carbon dioxide fairly constant in the atmosphere.

Glycolysis Lactic Acid Fermentation Alcoholic Fermentation Krebs Cycle Electron Transport Chain