Lab. No.2 Respiration 1

Cellular Respiration * Cellular respiration is the name given to metabolic pathways in which cells harvest the energy from the metabolism of food molecules. * These reactions proceed the same way in plants and animals. Overall Reaction: C6H12O6 + 6O2 → 6CO2 + 6H2O

* Both cellular respiration and fermentation are catabolic pathways, breaking down organic molecules like glucose.

Cellular Respiration 1. Aerobic Cellular Respiration 2. Fermentation

Aerobic Cellular Respiration C6H1206 + 6O26CO2 +6H20 + ENERGY Stages: * Glycolysis in cytosol. * Kreb’s cycle in mitochondrial matrix. * Electron Transport Chain, the break down of 6-carbon glucose molecule into two 3-carbon molecules called pyruvate.

Glycolysis

Glycolysis * Occurs in the cytoplasm. * During glycolysis, glucose,6 carbon-sugar, is split into 2, 3-carbon sugars. * Net yield of glycolysis is 2 ATP and 2 NADH/glucose. * Glycolysis occurs whether O2 is there or not So it can run under aerobic or anaerobic conditions.

Glucose activation Energy harvest

Kreb Cycle

Kreb Cycle * Completes breakdown of glucose to single carbon molecules. * The process is aerobic (requires oxygen).

Step 1

Electron Transport Chain

Electron Transport Chain * The energy needed to do this is supplied by electrons carried by NADH.

Summarize

Fermentation

Fermentation * Fermentation is a pathway for the oxidation of glucose that produces ATP in the absence of oxygen. Fermentation is similar to respiration because it begins with glycolysis. Fermentation differs from respiration because it does not involve the Krebs cycle or an electron transport chain.

Fermentation yields waste products other than CO2 and H2O * Fermentation yields waste products other than CO2 and H2O. In humans, fermentation yields lactic acid and in yeast fermentation yields ethyl alcohol in addition to CO2. * Since fermentation lacks a Krebs cycle and an electron transport chain, the only energy products come from glycolysis. The 2 NADH are used to produce the alcohol or lactic acid. The total amount of ATP produced from one molecule of glucose is 2.

Alcohol Fermentation * Pyruvate is converted to ethanol in two steps.

Lactic Acid Fermentation * Pyruvate is reduced directly by NADH to form lactate. Lactic acid fermentation by some fungi and bacteria is used to make cheese and yogurt.