Chapter 7.5 Summary

Cellular respiration converts energy in food to energy in ATP

• Mitochondria's structure key for cellular respiration
• Inner membrane is highly folded to give more room and maximize ATP production
• Metabolism: all a cell's chemical processes
• Cellular respiration consists of a series of reactions - referred to as a metabolic pathway
• Enzymes catalyze each reaction
• Three main stages of cellular respiration: glycolosis, Krebs cycle, electron transport chain
• Glycolysis: breaking down a glucose molecule
• Takes place in the cytoplasm outside the mitochondria
• Glucose is split in two, each molecule with three carbons and one phosphate group
• Each 3-carb molecule transfers electrons and H ions to NAD+
• NAD+ --> 2 electrons + H ion --> NADH
• Four new ATP molecules produced - net gain of 2 ATP molecules
• 3-carb molecule become pyruvic acid
• Krebs cycle takes place within fluid matrix of inner membrane
• Finishes breaking down pyruvic acid into carbon dioxide
• Glycolysis produces 2 pyruvic acid molecules
• Pyruvic acid loses one CO2 molecule and becomes acetyl CoA
• Acetyl CoA enters Krebs cycle and joins a four-carbon acceptor molecule
• Reactions produce 2 CO2 molecules and 2 ATP (one per acetyl CoA)
• NADH and FADH2 trap most of energy
• At the end, the four-carbon acceptor is regenarated and cycle continues
• Electron Transport Chain occurs in inner membranes of mitochondria
• Two parts: electron transport and ATP production by ATP synthase
• NADH transfers electrons from glucose to electron transport chain
• Electron is moved from carrier to carrier and pulled by oxygen at end of chain
• Each transfer releases a small amount of energy
• This energy pumps H ions across the membrane from less concentrated to more concentrated
• This stores potential energy like a dam holding back water
• ATP synthase: protein structures that create ATP from ADP
• Hydrogen ions are rushed back through the ATP synthase
• ATP synthase uses hte energy to convert ADP to ATP
• Generates up to 34 ATP per glucose molecule
• ATP production requires oxygen

Concept Check 7.5

1) How is the mitochondrion's structure suited to its function?

A mitochondrion's inner membrane has many folds in it so that there are more sites for reactions to occur and maximizes ATP production.

2) Identify the three stages of cellular respiration, where in the cell each takes place, and how many ATP molecules it produces.

First, glycolysis takes place in the cytoplasm and produces two ATP molecules. The Krebs cycle takes place in the inner membranes of the mitochondria and produces two more ATP molecules. The electron transport chain and ATP synthase occur further into the mitochondria and produce up to 34 ATP molecules.

3) Summarize the use and production of ATP in one cycle of cellular respiration.

The production of ATP only requires two ATP molecules as an initial energy investment however it produces up to 38 ATP molecules. So you have a net gain of 36 ATP molecules per cycle.