Cellular Respiration 2 Structures and functions

Respiration Three step process: Glycolysis (all living cells) Krebs cycle (higher animals) Electron transport chain (higher animals)

Glycolysis = to split sugar Does not need oxygen Occurs in cytoplasm Only releases ¼ of glucose energy C 6 sugar = 2 C 3 sugars 2 C 3 pyruvate Energy captured via 2 ATP H + released may be captured by NAD in higher cells

Catabolic = energy releasing reactions to produce pyruvate from glucose Proteins CarbohydratesFats Amino acidsGlucose Fatty acids Glycerol Pyruvic acid (Pyruvate) Glycolysis In cytoplasm

Mitochondrion

Getting into the mitochondrion Via Link reaction 3 Carbon Pyruvate 2 Carbon Acetyl coenzyme A attaches to pyruvate can be re-used Transport protein in the membrane uses ATP Release of CO 2 Cytoplasm Mitochondrion Mitochondrial membrane

Inside the mitochondrion Where O 2 is present, further processing can occur by: – Krebs cycle (in membrane space) – Electron transport chain (on cristae) – Energy requirements of a cell (eg muscle) indicated by: Number of christae Number of mitochondria

Krebs cycle Needs oxygen Controlled decomposition of pyruvate Releases carbon as CO 2 H + ions captured by NAD Releases 2 ATP Provides > 20 proteins for metabolic processes Refer to p127 in Biozone Look at position on flowchart

Electron transport chain Needs oxygen Located on christae Complex series of reactions Releases energy to give 34 ATP Uses oxidation product of ½ O 2 Uses H+ ions from NADH Releases H 2 0 as final product.

But what happens when oxygen is not available? Anaerobic respiration Is a relatively wasteful process: – In plants it produces toxic wastes like alcohol – In animals lactic acid must be removed to the liver, and converted back to glucose. Synthesises no more ATP It does allow the glucose to pyruvate reaction to continue

Cellular Respiration Summary In cytoplasm Glucose (6 carbon sugar) broken into 2 x 3 carbon sugars by GLYCOLYSIS 2 ADP 2 ATP H + in NAD Through the Mitochondrial membrane by Transport protein in the LINK REACTION (uses ATP ADP) oxygen present In the matrix of the mitochondrium KREBS CYCLE 2 ADP 2 ATP 2 ATP H + in NAD

On the christae of the mitochondrium ELECTRON TRANSPORT CHAIN 34 ADP 34 ATP H2OH2O without oxygen Where no oxygen is present muscle cells undergo ANAEROBIC RESPIRATION producing lactic acid and allowing further glycolysis to occur BUT NO MORE ATP is produced. Lactic acid can be metabolised back to glucose in the liver Anaerobic respiration also used by yeasts and simple organisms eg bacteria producing often toxic wastes like alcohol Total ATP per glucose: 2 from Glycolosis 2 from Krebs Cycle 34 from Electron Transport Chain