1. Cellular Respiration This is the process by which animals process food to obtain the calories needed for energy to do the cellular processes necessary for life.
Watch this:
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2. Photosynthesis vs Cellular Respiration
There is an energy trail: producers (photosynthesizers) consumers (animals) decomposers (bacteria)
A cow eating grass is an example of a consumer eating a producer
Photosynthesis is carried out by plants inside of chloroplasts (organelle)

3. Plants vs Animals
Cellular respiration is carried out in the mitochondria in animals and plants
Plants carry out photosynthesis and therefore have chloroplasts and mitochondria
Besides photosynthesis, they also must break down their products to make ATP for cellular processes

4. Food
The ultimate source of energy in food is “the sun”

5. Cellular Respiration Includes pathways that require oxygen
Glucose directly provides energy for cellular work through cellular respiration!
Glucose is oxidized and O2 is reduced
Glucose breakdown is therefore an oxidation-reduction reaction (redox)
Breakdown of one glucose results in 36 to 38 ATP molecules
THE GOAL IS TO MAKE ATP TO RUN THE PROCESSES OF OUR CELLS.

6. Cell Respiration Overview
Glucose:
Stores energy in the molecule
Cell respiration:
Breaks down the molecules
Extracts the contained energy
Transfers electrons (from glucose)
To electron carriers (e.g., NADH, FADH)
to make ATP
Giving off waste products (CO2 & H2O)
1st stage:
2nd & 3rd stage:
Cytoplasm
Mitochondria

7. Overall Equation for Cellular Respiration
C6H12O O2
YIELDS
6CO2 + 6H ATP’s

8. What Type of Process is Cellular Respiration?
An Oxidation-Reduction Process or REDOX Reaction
Oxidation of GLUCOSE --> CO2 + H2O (e- removed from C6H12O6)
Reduction  O2  to  H2O (e- passed (added) to O2)
Electrons are lost from one substance and added to another substance!

9. Other Cellular Respiration Facts
Metabolic Pathway that breaks down carbohydrates
Process is Exergonic as High-energy Glucose is broken into CO2 and H2O
Process is also Catabolic because larger Glucose breaks into smaller molecules

10. What are the Stages of Cellular Respiration?
1. Glycolysis
2. The Krebs Cycle
3. The Electron Transport Chain (ETC)
REMEMBER THESE STEPS!

11. What this process needs to do is to strip the electrons off of glucose and eventually use them in the electron transport chain to create a proton gradient which, when turned on, allows them to flow through an enzyme (protein) which attaches a high energy phosphate to ADP to form ATP.
So steps 1 and 2 are just electron collecting processes. It does take some work.

12. Cellular Respiration
Glycolysis
Krebs cycle
Electron transport

13. Where Does Cellular Respiration Take Place?
It actually takes place in two parts of the cell:
Glycolysis occurs in the Cytoplasm
Krebs Cycle & ETC Take place in the Mitochondria

14. Review of Mitochondria Structure
Smooth outer Membrane
Folded inner membrane
Folds called Cristae
Space inside cristae called the Matrix
Copyright Cmassengale

15. In A Nutshell…

16. Copyright Cmassengale
Diagram of the Process
Occurs across Cristae
Occurs in Cytoplasm
Occurs in Matrix
Copyright Cmassengale

17. 1st stage:
2nd stage:
3rd stage:
Glycolysis
Krebs cycle (or citric acid)
Electron transport

18. Electrons are the stars!
If we track the transfer of hydrogen from sugar to oxygen, we also follow the transfer of electrons. During cellular respiration, hydrogen and its bonding electrons change partners from sugar to oxygen, forming water as a product. Energy is also released.

19. Glycolysis, occurs in the cytoplasm
Series of steps (but 2 phases) 1.
Glucose
2 pyruvic acid molecules
As bonds in glucose are broken
Electrons (and H+ ions)
NAD+ 2.
NADH
Glucose
Is oxidized
NAD+
Is reduced
Net output is 2 ATP for each glucose molecule
But, most of the released energy carried by NADH

20. Steps of Glycolysis
1. glucose (6 carbon sugar) is broken into two 3 carbon molecules which requires 2 ATP
2. The 3 carbon molecules donate high energy electrons to NAD+ forming NADH (reduction)
3. 4 ATP are produced. Net, 2 ATP
The two 3 carbon molecules are pyruvate and still hold a lot of energy which will be harvested in step 2. the Kreb’s cycle (citric acid cycle)

21. With or Without Oxygen aerobic means with oxygen

22. Glucose pyruvic acids
Phase one
3 carbon
6 carbon
3 carbon

23. Glycolysis, phase 1
Some ATP is used to start the ‘breakdown’ of glucose
Mitochondria
Cytoplasm

24. Glycolysis, phase 2 High energy electrons are donated To NAD+
Forming NADH

25. Glycolysis, phase 2
And, phosphate groups are transferred
ATP is made

26. Overall Review of Glycolysis
Notice that two ATPs are used and Four are yielded, resulting in net 2 ATPs produced.

27. Glycolysis Diagram

28. Glycolysis Summary Also produces 2 NADH and 4 ATP
Pyruvate is oxidized to Acetyl CoA and CO2 is removed

29. In-between glycolysis & Krebs
Just before (or as) they enter the mitochondria
1. Pyruvic acid molecules are modified. It loses one carbon
And CO2 is released
The altered molecule is acetic acid
(…vinegar!)
Acetic acid is attached to a carrier molecule
Called coenzyme A one NADH is produced
And forms acetyl CoA
To the mitochondrion

30. Prep for Citric Acid Cycle

31. Krebs cycle, in the mitochondria
Series of reactions
Continues to break down the sugar
Present as acetic acid
Captures more energy
As NADH & FADH2
And more CO2 is released – the first electron acceptor of cellular respiration is NAD+
Net output is 2 ATP for each glucose molecule
But again, most of the released energy carried by NADH

32. A Little Krebs Cycle History
Discovered by Hans Krebs in 1937
He received the Nobel Prize in physiology or medicine in 1953 for his discovery
Forced to leave Germany prior to WWII because he was Jewish

33. Krebs Cycle Summary Requires Oxygen (Aerobic)
Cyclical series of oxidation reactions that give off CO2 and produce one ATP per cycle
Turns twice per glucose molecule
Produces two ATP
Takes place in matrix of mitochondria

34. Krebs Cycle Summary
Each turn of the Krebs Cycle also produces 3NADH, 1FADH2, and 2CO2
Therefore, For each Glucose molecule, the Krebs Cycle produces 6NADH, 2FADH2, 4CO2, and 2ATP

35. Krebs Cycle
ATP
NETS: 3NADH, 1ATP, 1FADH2, & 2CO2

36. What Carries the Electrons?
NAD+ (nicotinadenine dinucleotide) acts as the energy carrier
NAD+ is a coenzyme
It’s Reduced to NADH when it picks up two electrons and one hydrogen ion

37. Are There Any Other Electron Carriers?
YES! Another Coenzyme!
FAD+ (Flavin adenine dinucleotide)
Reduced to FADH2

38. Electron Transport, in the mitochondria
Most of the ATP is produced in the ETC
And, NADH & FADH donate their electrons to the ETC
At the end of the chain of steps
O2 exerts a strong pull on electrons
And combines electrons & H+ ions to form H2O
The ‘downhill’ flow of electrons powers an enzyme
ATP synthase
Which produces ~ 34 ATP

39. Electron Transport An array of molecules (…proteins)
In the inner membrane of the mitochondrion

40. Electrons move from one member to the next
The energy given up pumps H+ to inner space
Matrix
Oxygen captures electrons
Hydrogens are added, water forms

41. The buildup of H+ ions give up energy
When they diffuse through a special protein
ATP synthase
Matrix
ATP synthase captures their energy
To make ATP

43. ATP Synthase

44. ATP Synthase – actual protein

45. Electron Transport Chain Summary
34 ATP Produced
H2O Produced
Occurs Across Inner Mitochondrial membrane
Uses coenzymes NAD+ and FAD+ to accept e- from glucose
NADH = 3 ATP’s
FADH2 = 2 ATP’s
Oxygen is eventually reduced by the electrons to form water!

46. What would happen to the flow of electrons if oxygen were not present?
The flow of electrons would continue but at a slower rate.
The flow would cease and ATP production would stop.
The presence of oxygen would have no effect.

47. Cyanide binds strongly with the last electron carrier in the chain.
How would this affect the flow of electrons?
The flow of electrons would continue but at a slower rate.
The flow would cease and ATP production would stop.
The presence of cyanide would have no effect.

48. Learning check
Of the 3 stages of cell respiration, which produces the most ATP per glucose?
In glycolysis, _______ is oxidized and _______ is reduced.
The final electron acceptor of the electron transport chains in mitochondria is _______.

49. Learning check
Cells can harvest the most chemical energy from which of the following?
An NADH molecule
A glucose molecule
Six carbon dioxide molecules
Two pyruvic acid molecules

50. Fermentation Occurs when O2 NOT present (anaerobic)
Called Lactic Acid fermentation in muscle cells (makes muscles tired)
Called Alcoholic fermentation in yeast (produces ethanol)
Nets only 2 ATP

52. Learning check
This figure represents an overview of the different processes of cellular respiration.
Which of the following correctly identifies the different processes?
1. Glycolysis; 2. Electron transport chain; 3. Krebs cycle
1. Glycolysis; 2. Krebs cycle; 3. Electron transport chain
1. Krebs cycle; 2. Electron transport chain; 3. Glycolysis
1. Electron transport chain; 2. Glycolysis; 3. Krebs cycle