Cellular Respiration 8.3

Main Idea: Living organisms break down organic molecules (food) in the presence of oxygen during cellular respiration to get energy. C6H12O6 + 6O2 -> 6CO2 +6H2O + Energy Know this equation! What are the reactants and what are the products?

2 Main Parts: Anaerobic (without oxygen) Glycolysis Lactic Acid Fermentation Alcohol Fermentation Aerobic (with oxygen) Krebs Cycle Electron Transport

Let’s start with Glycolysis What is glycolysis? Breakdown of glucose in the cell’s cytoplasm Page 229 in your book- Figure 8.12 Glucose is broken down into 2 three-carbon molecules. (2 ATP are used) NAD+ becomes NADH (electron carrier) 2 three-carbon molecules become 2 pyruvate and 4 ATP are produced.

What are the net products of glycolysis? 2 Pyruvate 2 ATP Why not 4 ATP? Because 2 ATP are used to start the reaction so only a net of 2 ATP are produced.

Krebs Cycle Pyruvate converted to CO2 in the mitochondrial matrix. ATP, NADH, and FADH2 are produced. Page 230 Figure 8.13 Acetyl CoA formed Acetyl CoA moves to mitochondrial matrix and combines with a 4-carbon compound: Citric Acid made Citric Acid Broken down Acetyl CoA and citric acid are generated and the cycle begins again.

Remember For every glucose molecule there is 2 turns of the Krebs cycle. What is the net yield of products of the Krebs cycle? 6 CO2 2 ATP 8 NADH 2 FADH2

Electron Transport Final Step in breakdown of glucose Happens in the mitochondrial membrane Page 230 figure 8.14 NADH and FADH2 release electrons & H+ becoming NAD+ and FAD H+ is pumped into the intermembrane space across the inner membrane H+ diffuses back across membrane into matrix (chemiosmosis) O2 is the final electron receptor Protons and e- are transferred to oxygen to form H2O

In Eukaryotes 1 molecule of glucose gives us 36 ATP From what cycles are these ATP produced and how many are produced in each cycle? Glycolysis 2 ATP Krebs 2 ATP Electron Transport 32 ATP ATP is used to provide energy for the cell

In Prokaryotes cellular respiration No Mitochondria so there are differences Electron transport happens in the cellular membrane Because we don’t have to move pyruvate to the mitochondria in prokaryotes 2 ATP are “saved”. Net total ATP = 38 Why are 2 more ATP produced in prokaryotic cellular respiration than in eukaryotic cellular respiration?

Anaerobic Respiration Without oxygen Glycolysis Lactic Acid Fermentation Alcohol Fermentation

Fermentation Occurs in the cell’s cytoplasm It regenerates ATP and produces small amount of ATP Lactic Acid Fermentation Pyruvate converted to lactic acid with help of enzymes Skeletal muscles produce lactic acid when O2 supply is low Some microorganisms produce lactic acid -> used in cheese, yogurt, sour cream Alcohol Fermentation: pyruvate converted to ethyl alcohol and CO2