Download 2. Citric acid cycle

Lecture 2 Outline (Ch. 7)
I.
Overview of Cellular Respiration
II.
Redox Reactions
III. Steps of Respiration
IV. Cellular Respiration
A. Glycolysis
B. Coenzyme Junction
C. Citric Acid Cycle (aka Krebs/TCA cycle)
D. Electron Transport Chain (ETC)
E. Chemiosmosis
V. Anaerobic respiration
VI. Respiration using other biomolecules
Cellular Respiration
Overall purpose:
• convert fuels to
energy
• animals AND plants
• complementary to
photosynthesis
Cellular Respiration
Cellular Respiration:
(Exergonic)
• catabolizes sugars to CO2
• requires O2
• at mitochondrion
Redox Reactions
• as part of chemical reaction, e- are transferred
• e- transfer = basis of REDOX reactions
(reduction) (oxidation)
Redox Reactions
• follow the H, e- w/them
Redox Reactions
Equation for respiration
Redox Reactions
• transfer of e- to oxygen is stepwise
Redox Reactions
• e- moved by NAD+ (niacin)
• when “carrying” e- (& H+), NADH
• gained e- (& H+), reduced
Where do e- come from? • food (glucose)
Where do e- go?
• glucose
NADH
ETC
O2 (H2O)
Steps of Respiration
• Steps of respiration:
1. glycolysis
Coenzyme Junction
2. Citric acid cycle
3. ETC
4. Chemiosmosis
Cellular Respiration
• Stages of respiration:
1. Glycolysis – prep carbons
Cellular Respiration
1. Glycolysis
• 1 glucose (6C)
2 pyruvate (3C)
• key points: - inputs
- ATP
- NAD+/NADH
- CO2 and H2O
- outputs
• eukaryotes AND prokaryotes
Glycolysis
Cellular Respiration
-inputs:
-outputs:
Where do they go?
Cellular Respiration
Coenzyme Junction • 2 pyruvate (3C)
• pyruvate joins coenzyme A (vitamin B)
• 2 C lost (as CO2)
• 2 NAD+  NADH
2 Acetyl CoA (2C)
Steps of Respiration
• Stages of respiration:
2. Citric acid cycle
e- transfer: redox
Cellular Respiration
2. Citric acid cycle
• few ATP so far
• mitochondrial matrix
• 2 Acetyl CoA (2C) join
oxaloacetate (4C)
• 2 citrate (6C)
converted several steps,
4C lost (CO2)
• e- to carriers
(NAD+, FAD)
Citric acid cycle
-inputs:
-outputs:
Where do they go?
Self-Check
Step of
Respiration
Inputs
Outputs
CO2/H2O
ATP
produced
e- carriers
loaded
Glycolysis
1 glucose
2 pyruvate
2H2O
2 net
2 NADH
Coenzyme
Junction
Citric Acid Cycle
Electron
Transport Chain
Oxidative
phosphorylation
Fermentation
Steps of Respiration
• Steps of respiration:
1. glycolysis
- cytosol
Coenzyme Junction
2. Citric acid cycle
- mitochondrial
matrix
3. ETC
- inner
mitochondrial
membrane
4. Chemiosmosis
- inner membrane to intermembrane space
Steps of Respiration
• Stages of respiration:
3. ETC
Proton
Motive
Force
Substrate-level phosphorylation
Phosphate group moved from substrate to ADP  yields ATP
Cellular Respiration
3. Electron transport
chain (ETC)
• lots of energy
harvested
• released in stages
• so far, 4 ATP –
substrate P
• many ATP – oxidative phosphorylation
Cellular Respiration – mitochondria revisited
Cellular Respiration
Electron transport chain (ETC)
• ETC  e- collection molecules
• embedded on inner
mitochondrial membrane
• accept e- in turn
• e- ultimately accepted by O2
(O2 reduced to H2O)
Electron transport chain (ETC)
-inputs: per glucose,
-outputs:
Where do they go? H+
NAD+/FAD
Steps of Respiration
• Stages of respiration:
4. Chemiosmosis
ATP produced!
Cellular Respiration
4. Chemiosmosis
• ATP synthase: inner mitochondrial membrane
• energy input ATP – H+ gradient
• chemiosmosis – ion gradient to do work
Cellular Respiration
4. Chemiosmosis
• Four parts to ATP synthase:
Rotor, Stator, Rod, Knob
• H+ must enter matrix here
• Generates 1 ATP per ~3.4 H+
Cellular Respiration
Summary of respiration
• Cells convert ~ 40% of energy in glucose to energy in ATP
• Most fuel efficient cars convert only ~ 25% of gasoline energy
Cellular Respiration - anaerobic
• no O2 – no oxidative
phosphorylation
• fermentation
- extension of glycolysis
• substrate-level
phosphorylation only
• need to regenerate
e- carrier (NAD+)
Cellular Respiration - anaerobic
Cellular Respiration - anaerobic
• Types of fermentation 1. alcohol
• pyruvate
converted to
acetaldehyde
• acetaldehyde
accepts e• ethanol produced
Cellular Respiration - anaerobic
• Types of fermentation 2. Lactic acid
• pyruvate
accepts e-
• lactate
produced
Cellular Respiration - anaerobic
• inputs/outputs
• alcohol
• pyruvate in
• CO2 and EtOH out
• brewing & baking
• lactic acid
• pyruvate in
• lactate out
• muscle fatigue
Cellular Respiration
• pyruvate - junction
• O2 present –
citric acid cycle
• O2 absent fermentation
Self-Check
• Comparison of aerobic vs. anaerobic respiration:
Aerobic
• ATP
made by:
• ATP per
glucose:
• initial eacceptor:
• final eacceptor:
Anaerobic
Cellular Respiration – other biomolecules
• Glucose catabolism
= one option
• Proteins:
– amino group removed
– a.a. enter Krebs Cycle
Cycle can run
in reverse!
Cellular Respiration – fats
• Fats:
Glycerol in at glycolysis
- becomes pyruvate
Fatty acids at coenzyme junction
- becomes Acetyl CoA 2 carbons
at a time via β-oxidation
A fatty acid chain of 16 C is energetically
equivalent to how many glucose molecules?
Self-Check
Step of
Respiration
Inputs
Outputs
CO2/H2O
ATP
produced
e- carriers
loaded
Glycolysis
1 glucose
2 pyruvate
2H2O
2 net
2 NADH
Coenzyme
Junction
Citric Acid
Cycle
Electron
Transport Chain
Oxidative
phosphorylation
Fermentation
Lecture 2 Summary
1. Respiration Overview (Ch. 7)
Purpose
Redox reactions
Electron carriers & final electron acceptors
2. Locations of respiration steps, inputs/outputs, purpose, description (Ch. 7)
Glycolysis
Coenzyme Junction
Citric Acid/Krebs Cycle
ETC & Oxidative Phosphorylation [chemiosmosis]
3. Differences with anaerobic respiration (Ch. 7)
Purpose
Location
Inputs/outputs
4. Catabolism of other biomolecules (Ch. 7)
Proteins
Fats