1. Chapter 7 Cellular Respiration

2. Glycolysis and Fermentation
Cellular respiration: cells make ATP by breaking down organic compounds
Both autotrophs and heterotrophs undergo cellular respiration
Break down organic compounds into simple molecules and energy
Some energy used to make more ATP, some is used by the cells to do work

3. Overview of Cellular Respiration

4. Cellular Respiration Overview

5. Overview of Cellular Respiration
1. Glycolysis
Organic compounds are converted into carbon molecules of pyruvic acid, which makes a small amount of ATP and NADH (electron carrier)
Anaerobic process = does not require oxygen
Occurs outside of the mitochondria

6. Overview of Cellular Respiration
2. Aerobic Respiration (oxygen present)
Pyruvic acid is broken down and NADH is used to make a large amount of ATP
Note: pyruvic acid can enter other pathways when no oxygen is present. Glycolysis and other anaerobic pathways = fermentation

7. Overview of Cellular Respiration

8. Glycolysis
Series of chemical rxns catalyzed by specific enzymes to create pyruvic acid from 6-carbon molecules
1. Phosphate groups are attached to glucose to form a 6-carbon molecule

9. Glycolysis 2. 6-carbon molecule splits into two G3P molecules
3. G3P molecules are oxidized and receive a phosphate group
NAD+ to NADH
4. Phosphate groups (4) added in step 1 and 3 are removed, forming pyruvic acid, produce 4 ATP

10. Glycolysis Two ATP molecules used, but four are produced
Glycolysis has a net yield of 2 ATP molecules

11. Fermentation
In anaerobic environments some cells can still produce carbon compounds
Using glycolysis and additional pathways to generate NAD+ is called fermentation
Lactic acid fermentation
Alcoholic fermentation

12. Fermentation
Lactic acid fermentation: pyruvic acid is converted into lactic acid
Involves transfer of one hydrogen atom from NADH and the addition of one proton (H+) to pyruvic acid (NADH  NAD+)
NAD+ is used in glycolysis, and helps keep this process going
Why is this process important?

13. Lactic Acid Fermentation

14. Fermentation
Alcoholic fermentation: converts pyruvic acid into ethyl alcohol
Two steps:
1.) CO2 molecule removed from pyruvic acid
Leaves a two carbon compound
2.) Two hydrogen atoms are added to the two-carbon compound to form ethyl alcohol
The hydrogen atoms come from NADH and H+, and regenerates NAD+ for glycolysis

15. Aerobic Respiraton Aerobic = Uses oxygen Two major stages:
Krebs Cycle
Electron Transport Chain
Krebs cycle involves completing the oxidation of glucose in glycolysis. NAD+  NADH
Electron transport chain uses NADH to make large quantities of ATP

16. Aerobic Respiraton In prokaryotes, occurs in the cytosol of the cell
In eukaryotes, occurs inside the mitochondria
Pyruvic acid produced in glycolysis diffuses across mitochondria’s double membrane and into the matrix

17. Aerobic Respiration
Pyruvic acid enters the mitochondrial matrix and reacts with a molecule called coenzyme A to form acetyl coenzyme A, acetyl CoA

18. The Krebs Cycle
Biochemical pathway that breaks down acetyle CoA, producing CO2, hydrogen, and ATP

19. The Krebs Cycle
1. Acetyl CoA combines with oxaloacetic acid to produce citric acid
Regenerates coenzyme A
2. Citric acid releases CO2 and hydrogen forming a five carbon compound
NAD+  NADH
3. Five carbon molecule releases CO2 and Hydrogen forming a four carbon molecule

20. The Krebs Cycle
4. Four carbon compound from step three creates another four carbon compound by releasing a hydrogen
FADFADH2
5. Step four molecule releases a hydrogen to regenerate oxaloacetic acid to keep krebs cycle going
NAD+ NADH

21. Electron Transport Chain
Second stage of aerobic respiration
Couples with chemiosmosis
ETC and ATP synthase are embedded into the membrane of the mitochondria
In prokaryotes this occurs on the cell membrane
ATP is produced when NADH and FADH2 release hydrogen, regenerating NAD+ and FAD

22. Electron transport chain
1. NADH and FADH2 give up electrons 2. electrons passed down chain, losing energy moving from molecule to molecule 3. energy from electrons pumps protons from the matrix building a concentration gradient between inner and outer membranes

23. Electron transport chain
4. concentration gradients of protons drive the synthesis of ATP by chemiosmosis (same as photosynthesis)
5. Oxygen is the final acceptor of electrons that pass down the ETC
Protons, electrons and oxygen all combine to form water