1. Riveting Respiration
Chapter 9
So Why do we Breathe????

2. I. Setting the Stage Sun – Ultimate energy source for ecosystems
ATP – Usable cellular energy
Chemical Energy – Energy stored in chemical bonds
Fermentation – Partial breakdown of sugar WITHOUT using Oxygen

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4. II. Cellular Respiration
Complete degrading (breakdown) of sugar using Oxygen (catabolic process)
Uses energy stored in food to make ATP
C6H12O6 + 6O2  6CO2 + 6H2O + Energy (ATP + heat)
5G = -686 kcal/mol – WOW!!!
ATP will be used to drive other processes that need energy through Phosphorylation

5. Redox Reactions (oxidation-reduction)
Chemical reaction where one or more electrons are transferred from one reactant to another
Oxidation – loss of electron from substance
Reduction – Addition of electron to another substance

6. Redox Reactions Complete transfer of electrons Na + Cl Na+ + Cl –
Partial transfer of electrons
CH4 + 2O2 CO2 + Energy + 2H2O

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8. Redox Reactions
When an electron is transferred from a less electronegative atom to a more electronegative atom, ENERGY is released that can be used to do work

9. Redox Reactions For respiration C6H12O6 + 6O2  6CO2 + 6H2O
Glucose is oxidized and oxygen is reduced releasing lots of energy (remember oxygen is VERY electronegative)

10. IV. Respiration
Performed mainly on carbohydrates and fats, but we will focus on GLUCOSE
Activation energy prevents these high energy goods from breaking down spontaneously – so we will need ENZYMES to make respiration happen
Glucose is broken down in a series of steps. Each step has its own enzyme

11. Respiration
Hydrogens are not transferred directly to Oxygen, but are first passed to a Coenzyme called NAD+
NAD+ + electrons NADH
H+ (proton) is transferred to the solution
NADH will carry the electrons to an Electron transport chain and will be used to make ATP (more on this soon!!)

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13. Exciting Electron Flow
Overall flow of electrons in respiration:
FoodNADHelectron transport chainOxygen

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15. 3 Main Steps to Cellular Respiration
1. Glycolysis – happens in the cytosol. Breaks glucose into smaller compound (pyruvate)
2. Citric Acid (Krebs) cycle – happens in the matrix of the mitochondria. Breaks down pyruvate to CO2
3. Electron transport chain – happens in the inner mitochondrial membrane. Generates ATP using electrons from steps 1 and 2

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17. VII. Glycolysis
Splits glucose (6 Carbons) into two molecules of pyruvate (3 C each)
No oxygen required (yet)

18. Glycolysis A. Energy Investment Phase
2 ATP are USED to phosphorylate glucose and convert it into two pyruvates
B. Energy Payoff Phase
After a series of enzyme catalyzed reactions: 4 ATP are produced by Substrate level phosphorylation (using a substrate to make ATP)
2 NADH are produced by transferring electrons to NAD+

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20. C. Summary of Glycolysis
Total Input
Glucose, 2ATP, 2NAD+
Total Output
2 Pyruvate, 4 ATP, 2NADH
Net ATP produced = 2

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22. Got Oxygen???
If oxygen is present – pyruvate moves into the mitochondria
Pyruvate is converted to Acetyl CoA in a series of 3 reactions (all with enzymes)
CO2 is released
NAD+ gains an electron NADH
Acetyl CoA enters the Krebs cycle

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24. VIII. Citric Acid (Kreb’s) Cycle
Occurs in mitochondria matrix
Cycle has 8 total steps (each catalyzed by different enzyme)
Step 1 – Acetyl CoA combines with Citrate (citric acid cycle)
Cycle happens 2 times (one for each Acetyl CoA)

25. Citric Acid Cycle For Each Acetyl CoA 3 NAD+  3 NADH + 3H+
1 FAD  1 FADH2
1 ATP is produced (substrate level phosphorylation)
2 CO2 are produced

26. Citric Acid Cycle Total Inputs 2 Acetyl CoA, 6 NAD+, 2 FAD, 2 ADP
Total Outputs
6 NADH, 2 FADH2, 2 ATP, 4 CO2 (released when exhale)

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28. Electron Transport Chain
A. Location-
Inner Mitochondrial Membrane
Series of molecules (mostly proteins) embedded in this membrane
Each part of the chain gets more and more electronegative until the end of the chain
OXYGEN is at the end of the
chain (most electronegative)

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30. Electron Transport Chain How it works?
NADH and FADH2 from glycolysis and the Citric acid cycle carry their electrons to the electron transport chain
NADH releases electrons at the top of the chain. Electrons are pulled down the chain by the increasing electronegativity of each molecule
As the electrons fall, ATP is made through Chemiosmosis (more later)

31. How it works (cont.)
FADH2 carries its electrons to the chain, but donates them a little further down the chain (not at the top)
These electrons are also pulled down the chain, producing ATP as they go
FADH2 starts here

32. C. Chemiosmosis Process that makes ATP
As electrons flow down the ETC, energy is released.
This energy is used to pump H+ (protons) across the membrane leaving a high concentration of H+ outside and a low concentration inside

34. Chemiosmosis
H+ wants to flow back in to the mitochondrial matrix to reach equilibrium
The only way for the H+ to get back in is through the enzyme ATP synthase
ATP synthase is an enzyme located in the inner mitochondrial membrane
As H+ moves through the membrane, it allows ADP to be phosphorylated making ATP (ADP + Pi ATP).
This is called Oxidative phosphorylation (using a redox rxn to make ATP)

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37. D. Net Output of Electron Transport Chain
For each NADH that enters the chain, 3 ATP are produced – Total = 30 ATP
For each FADH2 that enters the chain, 2 ATP are produced – Total = 4 ATP
Water is released by combination of O2 with H+ and electrons H2O

38. Respiration Total ATP Production for Cellular Respiration
2 ATP – Glycolysis
2 ATP – Citric Acid Cycle
34 ATP – Electron Transport
Total = 38 ATP

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40. Fabulous Fermentation
Allows cells to generate ATP without Oxygen (anaerobic). ATP is made only by substrate level phosphorylation
Process involves Glycolysis + reactions to regenerate NAD+ (in respiration NAD+ is regenerated in the ETC)

41. Alcohol Fermentation
After glycolysis, pyruvate is converted to ethanol in order to regenerate NAD+. This allows glycolysis to continue again.
Occurs in Yeast and Bacteria
Used to make Alcohol

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43. Lactic Acid Fermentation
After glycolysis, pyruvate is converted to lactate to regenerate ATP.
Used by Fungi and Bacteria
Important in dairy industry to make cheese and yogurt.
Also occurs in Human Muscle Cells during exercise. Muscles can’t get enough oxygen to keep up with respiration. Lactate
builds up causing muscle cramps
and fatigue.

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45. Evolutionary Significance of Glycolysis
Glycolysis was probably used by the earliest prokaryotes to make ATP before oxygen was present in the atmosphere.
Evidence – Glycolysis occurs in the cytoplasm (not in mitochondria) and it is found in ALL living cells

46. What else can be used for Respiration??
1. Carbohydrates – Broken down into glucose then enter glycolysis
2. Proteins – Broken down into amino acids which can enter the cycle later in glycolysis or in Citric Acid cycle (not normally used – need to use amino acids to make protein)
3. Fats – Glycerol enters the cycle during glycolysis. Fatty acids are broken down into 2 Carbon fragments that enter at Kreb’s cycle

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48. Control of Respiration
Cells do not make more ATP than they need
Cells can switch of respiration, usually by Feedback Inhibition of certain enzymes in the chain.
This prevents making unnecessary ATP and the molecules used in respiration can be used for other processes.

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