1. Chapter 7 – The Working Cell: Energy from Food
College Prep Biology
Mr. Martino

2. 7.1 How Cells Make ATP
Cellular Respiration: harvesting of E from food molecules by cells
2 types of respiration:
Aerobic: requires oxygen (harvests 40% of E in glucose)
Anaerobic: does not require oxygen (harvests 2% of E in glucose)
Evolved about 3.8 billion years ago - before oxygen
C6H12O O CO H2O + E
Glucose is the example carbohydrate

3. Glycolysis: (exergonic) splits glucose into 2 pyruvic acid
Occurs in cytoplasm
Oxygen is final electron acceptor = water
Enzymes catalyze
First stage of all respiration

4. Overview of Aerobic Respiration
Aerobic Respiration is continuous – but occurs in 3 main stages
Glycolysis: (exergonic) splits glucose into pyruvic acid
Occurs in cytoplasm
Kreb’s Cycle: (exergonic) completes glucose breakdown - pyruvic acid becomes CO2
ETC: (endergonic) NADH and FADH2 shuttle e- and generates most of cell’s ATP by chemiosmosis

5. Two Mechanisms Generate ATP
Chemiosmosis: cells use the potential E of concentration gradients to make ATP
Depends upon membranes and ATP synthase
ETC makes this E transport possible
Cells generate most of their E this way

6. Substrate-level phosphorylation: an enzyme transfers a P-group from a substrate to ADP
No membrane involved
Only generates a small percentage of a cell’s ATP

7. 7.3 Second Stage – Pyruvic Acid Conversion and Kreb’s Cycle
2 pyruvate molecules from glycolysis enter mitochondrion
Pyruvic acid from glycolysis does not enter the Kreb’s cycle
1. It is oxidized while NAD+ is reduced to NADH
2. 1 C is released in the form of CO2
3. Coenzyme A + fragment = acetyl CoA
Each glucose produces 2 acetyl CoAs for Kreb’s

8. Kreb’s Cycle Only the acetyl part of acetyl CoA participates
Each turn of Kreb’s produces:
1 ATP by substrate level phosphorylation
3 NADH
1 FADH2
Turns twice per glucose

9. 7.4 Third Stage – Electron Transport System
Final stage of respiration is ETC & ATP formation
The fold of the cristae provide space for many ETC’s and ATP synthases
NADH is shuttled down the e- carriers
Oxygen is the final e- (H) acceptor forming H2O
Proteins shuttle H+ across the membrane
The greater the gradient the more potential E
H+ are passed through ATP synthase which catalyzes the formation of about 34 ATP

12. 7.5 Anaerobic Respiration
2 forms of anaerobic respiration
Alcoholic fermentation: anaerobic respiration in which pyruvic acids form ethyl alcohol
Performed by yeasts and bacteria
Releases CO2
Ethanol is toxic to the organisms who produce it – if too concentrated

13. 7.5 – con’t
Lactic Acid Fermentation: anaerobic fermentation in which pyruvic acids form lactic acids
Used to make cheese and yogurt
Occurs in muscle cells – causing pain and fatigue
No CO2 is released