Cellular Respiration

What is Cellular Respiration? Step-by-step breakdown of high- energy glucose molecules to release energy Takes place day and night in all living cells Occurs in stages, controlled by enzymes

Cellular Respiration (cont.) C 6 H 12 O 6 + 6O 2  6CO2 + 6H20 + Energy (ATP) Cellular respiration is the process used by mitochondria to produce energy for the cell. The three stages of cellular respiration are Glycolysis, Kreb’s Cycle, and Electron Transport Chain. Cells need glucose to make ATP.

Review of ATP ATP = Adenosine triphosphate ATP loses a phosphate group when instructed by an enzyme. This releases a lot of energy, which the organism can then use. The product is adenosine diphosphate (ADP) The reverse reaction can also take place, the phosphate group is reattached to the molecule using energy obtained from food or sunlight. ATP + H 2 O → ADP + HPO 4

Where does cellular respiration occur? Glycolysis In the cytoplasm Kreb’s Cycle Matrix of mitochondria Electron Transport Inner membrane of mitochondria

Different types of Cellular Respiration Aerobic respiration  Occurs in the presence of oxygen  When chemically breaking down glucose completely, this process releases large amounts energy Anaerobic respiration  Usually occurs when there is no oxygen available  When partially breaking down glucose, this process releases a very small amount of energy.

Stage 1: Glycolysis means "splitting sugars" ….6 carbon glucose is split into two 3 carbon molecules (pyruvate) Occurs in the cytoplasm of cells With or Without O 2 not required (anaerobic) Requires investment of 2 ATPs Some ATP produced Net yield = 2 ATPs

Chemical reactions that transfer electrons between reactants are called oxidation-reduction reactions, or redox reactions. In oxidation, a substance loses electrons, or is oxidized. In reduction, a substance gains electrons, or is reduced (the amount of positive charge is reduced) Remember “Oil Rig” “Oxidation” is loss (of electrons) “Reduction” is gain (of electrons)

During cellular respiration, the fuel (such as glucose) is oxidized and oxygen is reduced.

The Krebs Cycle (a.k.a. citric acid cycle) Occurs in the matrix of the mitochondria O 2 required (aerobic) CO 2 (waste) Remaining pyruvate combines with coenzyme – Acetyl CoA Some ATP produced Net yield = 2 ATPs

Krebs (cont.) Two cycles occur in which ATP is produced each time. A series of electron carriers (NADH, NAD+, FADH, FAD+) are produced which will be utilized in ETC. Glucose has been oxidized… lost all of its carbons.

Electron Transport Chain series of electron carriers in the inner membrane of the mitochondria O 2 required (aerobic) A lot of ATP produced Net yield = 32 ATPs

ETC (cont.) The two electron carriers (NADH, FADH) donate electrons to the electron transport chain, which powers ATP synthesis. Electron transfer in the electron transport chain causes proteins to pump H+ from the mitochondrial matrix to the intermembrane space. H+ then moves back across the membrane, passing through channels in ATP synthase ATP synthase uses the flow of H+ to drive phosphorylation of ATP

Cellular Respiration Review…... 3 Stages:  Stage 1: Glycolysis O 2 not required (anaerobic) Some ATP produced  Stage 2: Krebs Cycle O 2 required (aerobic) Some ATP produced  Stage 3: Electron Transport System O 2 required (aerobic) Much ATP produced Q. Where does each Stage occur? A. Cytoplasm of the cell A. Mitochondrion Matrix A. Mitochondrial inner membrane 2 ATPs 32 ATPs

Aerobic Respiration Oxygen combines with glucose to convert it into energy Releasing carbon dioxide and water as waste products. glucose + oxygen  carbon dioxide + water + lots of energy

Anaerobic Respiration Occurs if there is a lack of oxygen available for aerobic respiration Glucose is incompletely broken down In this type of respiration a lot less energy is produced and most of it is lost as heat.

Anaerobic Energy Production: Fermentation Lactic Acid  Formed mainly by animal muscle cells  Occurs in some unicellular organisms  Glucose  lactic acid + a small amount of energy Alcoholic Fermentation  Yeast cells, Bacteria  Glucose  alcohol + carbon dioxide + a small amount of energy

Summary: Aerobic & Anaerobic Similarities:  Glucose is broken down.  Carbon dioxide is released.  Energy is liberated. Differences: Aerobic respirationAnaerobic respiration Lots of energy releasedLittle energy is released Water is the end product Lactic Acid or alcohol is the end product Glucose is completely broken down Glucose is partially broken down Is dependent on oxygenIs not dependent on oxygen