1. Respiration.....
It ain't just breathin'
anymore!!

2. How Do Organisms Supply Themselves With Energy?

3. Key Questions How do organisms supply themselves with energy?
How do organisms extract energy from glucose?
How is the energy in glucose used to make ATP?

4. How Do Organisms Supply Themselves With Energy?
All organisms need energy
Ultimate source of energy on the Earth is the sun
Autotrophs make their own food;
examples: plants, some bacteria
Heterotrophs obtain chemical energy from other organisms
Examples?

5. Energy Currency Adenosine Triphosphate or ATP
Cellular respiration produces ATP
Aerobic versus anaerobic

6. Cellular Respiration

7. Steps of Cellular Respiration
Step 1: glycolysis
Step 2: acetyl-CoA formation
Step 3: citric acid cycle
Step 4: electron transport and oxidative phosphorylation

8. Cellular Respiration — Chemical Equation
C6H12O O2
Glucose Oxygen
6CO H2O + ATP
Carbon Water Energy
Dioxide

9. What Is Oxidation?
Oxidizing agent or electron acceptor accepts an electron
Reducing agent or electron donor donates an electron
Oxidation and reduction always go hand in hand
Examples of acceptors: O2, NAD+, FAD

10. Step 1: Glycolysis Occurs in Cytoplasm
Part 1: 6 carbons are split into 3-carbon molecules and are phosphorylated; uses ATP
Part 2: Phosphates and electrons are removed; electrons added to NAD+ to make NADH; produces 2 ATP

11. Step 1: Glycolysis Cont. Part 3:
More electrons and phosphates are removed from the 3-carbon molecules;
phosphates are added to ADP to make ATP

12. Glycolysis Overview
Breaks glucose into 2 molecules of pyruvate, generating 2 molecules of ATP and 2 molecules of NADH
Aerobic or anaerobic?
The pyruvate enters a cell’s ______.
When compounds are reduced, they ___ electrons.
When compounds are oxidized, they ___ electrons.
Which molecules/coenzymes from Glycolysis accept electrons?
ANAEROBIC
MITOCHONDRIA
DONATE
ACCEPT
NAD+

13. Step 2: Acetyl CoA Occurs in ______
MITOCHONDRIA
Oxygen needed for this reaction; aerobic
Pyruvate loses a carbon and 2 oxygens in the form of CO2
Enzymes link coenzyme A to the acetate
CoA synthesizes fatty acids.

14. Step 3: Citric Acid Cycle Overview
High energy electrons are captured in the form of NADH and FAD
Occurs in the matrix of the mitochondria
With each turn of the cycle, citrate loses a total of 8 electrons to electron acceptors such as NAD+

15. Step 3: Citric Acid Cycle
3 parts
Part 1: 6-carbon citrate and isocitrate formation
Part 2: conversion of isocitrate into a 4-carbon compound
Part 3: production of another molecule of OAA, which starts the cycle over again

16. Citric Acid Cycle

17. What If There Is No Oxygen?
After glycolysis, if there is no oxygen, fermentation will occur
Cells must regenerate more NAD+ from NADH
Yeast — form ethanol (terminal reaction produces CO2 )
Animals — form lactic acid (ouch)

19. Biochemical Pathway Intersections
Figure 6-7
Catabolism — breakdown of complex molecules such as food; produces energy, involves oxidation
Anabolism — synthesis of complex molecules; uses energy

20. How Do Other Food Molecules Enter Metabolism?
Fat, carbohydrates and proteins enter the cellular respiration pathway at different points
The most likely point is at acetyl CoA

21. Electron Transport Chain

22. Step 4: Electron Transport & Oxidative Phosphorylation
The pathway of electrons from one carrier to another is called ____ ____ _____;
Each electron carrier passes its electrons to the next carrier (bucket brigade)
Most of the electrons to the electron transport chain are received from what cycle?
A reduced carrier becomes oxidized when it gives up its electrons (forms ATP from ADP)
Oxygen accepts electrons
ELECTRON TRANSPORT CHAIN
KREB’S

23. How Do Cells Harvest Energy?
Proton gradient — flow of electrons through the electron transport chain creates this gradient (ATP is made from this gradient)
Chemiosmosis — harnessing of the energy stored in the chemical gradient; some machinery in the membrane must do this process

24. Generating a Proton Gradient
Mitochondria — inner and outer membrane
Intermembrane space — space between 2 membranes
Matrix — space within the inner membrane; makes up about 2/3 of the volume; ETC is embedded in this inner membrane

25. Pumping Protons pH & cytochromes assist w/ transport of electrons.
Gradient is produced when…..

26. ATP Synthase Proton complex
Protons flow through these channels back into the matrix
Works like a turbine
Uses energy to make ATP

27. Key Concepts
Cellular respiration converts the chemical energy of food molecules into the chemical energy of ATP
Most cells can use glycolysis to obtain energy
ATP production from cellular respiration depends on oxidative phosphorylation