1. UNIT III – CELLULAR ENERGY
Big Campbell ~ Ch 9, 10 1

2. I. ♪ ♫ THE CYCLE OF LIFE ♪ ♫ 2

3. II. ENERGY IN THE CELL Catabolic Pathway
Breakdown of molecules that releases stored energy; exergonic rxn
_____________________ – partial breakdown of sugars w/o O2
___________________________ – breakdown of sugars w/ O2
Similar to a car burning gasoline
Although much energy is lost as heat, some can be used to generate ATP by phosphorylating ADP
Oxidation-Reduction Reactions (Redox)
Energy produced in catabolism comes from transfer of e-
Movement of e- releases chemical energy of molecule
Released energy is used to attach Pi to ADP to form ATP
1 molecule loses an e- and a 2nd molecule gains an e- 3

4. II. ENERGY IN THE CELL, cont
Oxidation-Reduction Reactions, cont
_________________ – Loss of e-
_________________ – Gain of e-
_________________ agent - e- donor
_________________ agent - e- acceptor
Sometimes there is a complete transfer of e- and other times there is a change in the degree of e- sharing in covalent bonds
Inorganic Example: Na + Cl  Na+ + Cl-
Organic Example: 4

5. II. ENERGY IN THE CELL, cont
Importance of Electron Carriers
Energy contained in molecules (ex: glucose) must be released in a series of steps
Electrons are released as hydrogen atoms with corresponding proton (hydrogen's are “clipped” off)
Hydrogen atoms are passed to an _________________
Electron carriers are coenzymes
“Carry” ______ electrons in the form of H-atoms
Only 1 proton & 2 electrons are delivered
One H+ is released into the surrounding solution
Allow for max energy transfer, minimum energy loss 5

6. II. ENERGY IN THE CELL, cont
Electron Carriers
(oxidative states)
_________
e- acceptor in cellular respiration
Becomes NADH when reduced
Yields about ____ ATP
__________
e- acceptor in Krebs
Cycle / TCA Cycle / Citric Acid Cycle
e- acceptor in light
reaction of photosynthesis
Not used in cellular
respiration 6

7. II. ENERGY IN THE CELL, cont
A Closer Look at Electron Carrier Function in Cellular Respiration
Reduction of NAD+
___________________ oxidizes substrate by removing 2 H-atoms
NAD+ is reduced, creating NADH + H+
NADH shuttles electrons to ___________________________________________________. Electrons “fall” down to _______________ in a series of steps, each releasing energy in small amounts. 7

8. III. CELLULAR RESPIRATION OVERVIEW8

9. III. CELLULAR RESPIRATION OVERVIEW, cont’d
Cellular process to convert chemical energy in ___________ (and other molecules) into ________
Primarily takes place in ___________________ of eukaryotic cells
Overall Reaction
____________________________________________________
Steps in Cellular Respiration
Glycolysis – occurs in cytosol
“Splitting of sugar”
Initial breakdown of glucose to pyruvate, some ATP
Citric Acid Cycle – occurs in mitochondria
Completes oxidation of glucose to CO2
Produces ATP, but more importantly provides high-energy electrons for ETC
Electron Transport Chain – occurs in mitochondria
Oxidative Phosphorylation
Highest ATP yield; uses energy released from downhill flow of e- to generate ATP
Citric Acid Cycle + Electron Transport Chain = Oxidative Respiration 9

10. IV. GLYCOLYSIS 10 steps Occurs in cytosol of cell
Does not require oxygen
1st part of pathway is energy investment phase (5 steps)
2nd part of pathway is energy pay-off phase (5 steps)
Energy Investment Phase 10

11. IV. GLYCOLYSIS, cont
Energy Pay-Off Phase 11

12. IV. GLYCOLYSIS, cont
Summary of Glycolysis 12

13. V. OXIDATIVE RESPIRATION
2 pyruvates formed from glycolysis still contain a tremendous amount of chemical energy
If oxygen is available, pyruvate enters mitochondrion for citric acid cycle and further oxidation
Upon entering mitochondrion but prior to entering citric acid cycle
“Grooming” Step
Carboxyl group of pyruvate is removed, given off as CO2
Remaining 2-C molecule is oxidized to acetate → NAD+ reduced to NADH + H+
Acetate binds to molecule known as Coenzyme A to form acetyl CoA 13

14. V. OXIDATIVE RESPIRATION, cont
Grooming Step 14

15. V. OXIDATIVE RESPIRATION, cont
In the citric acid cycle (AKA…Krebs cycle or TCA Cycle), 2 3-carbon molecules go through a series of redox rxns.
Occurs in mitochondrial matrix
Produces NADH, FADH2, ATP, and CO2.
CoA is not actually a part of the reaction it is recycled remember, it is an enzyme! 15

16. V. OXIDATIVE RESPIRATION, cont16

17. V. OXIDATIVE RESPIRATION, cont
Electron Transport – Oxidative Phosphorylation
Traditionally called Electron Transport, now more commonly called ________
________________________.
Occurs in inner mitochondrial membrane
Membrane organized into cristae to ________________
__________________________
Two components to Oxidative Phosphorylation
_________________________ 17

18. V. OXIDATIVE RESPIRATION, cont
Electron Transport Chain
Collection of molecules, each more electronegative than the one before it
Molecules are reduced, then oxidized as electrons are passed down the chain
__________ is ultimate electron acceptor
Purpose is to establish H+ gradient on two sides of inner mitochondrial membrane
Energy from “falling electrons” used to pump H+ from matrix into intermembrane space 18

19. V. OXIDATIVE RESPIRATION, cont
Chemiosmosis
Enzyme complexes known as _________________ located in inner mitochondrial membrane
H+ electrochemical gradient provides energy
Known as _________________
Movement of H+ ions through membrane rotates enzyme complex
Rotation exposes active sites in complex
ATP is produced from ADP and Pi 19

20. V. OXIDATIVE RESPIRATION, cont
A summary of electron transport . . . 20

21. VI. CELLULAR RESPIRATION – A SUMMARY
Total ATP Gain in Cellular Respiration =
___ (glycolysis) + ____ (citric acid cycle) + ____ (oxidative phosphorylation) = _____ ATP / glucose 21

22. VII. CELLULAR RESPIRATION & OTHER FOOD MOLECULES22

23. VIII. METABOLIC POISONS
Blockage of Electron Transport Chain
Inhibition of ATP Synthase
“Uncouplers”
Prevent creation of H+ ion gradients due to leakiness of mitochondrial membrane 23

24. VIII. METABOLIC POISONS, cont24

25. IX. FERMENTATION Anaerobic pathway Occurs in cytosol Purpose
In glycolysis, glucose is oxidized to 2 pyruvate, 2 NAD+ are reduced to 2 NADH, and there is a net gain of 2 ATP
In oxidative respiration, NADH is oxidized back to NAD+ in electron transport chain
If oxygen is not present, another mechanism must be available to regenerate NAD+ or glycolysis cannot continue
In fermentation, pyruvate is reduced thereby oxidizing NADH to NAD+
Allows glycolysis and net gain of 2 ATP per glucose to continue 25

26. IX. FERMENTATION, cont 26

27. IX. FERMENTATION, cont 27