Lecture 7: Energy Transformation II
Next class bring paper and pen, drawing lots of stuff
Cellular respiration
o Catabolic… exergonic
Convert C-H bonds into ATP
o Carbs, fats, proteins…
Glucose uses the entire cellular respiration pathway
o Need to know where ATP is made, where NADH is made
Know glycolysis
o Where is it found
o What does it do?
o Free energy?
Where does it go?
o Requires O2?
Huge demand for oxygen, but the whole process does not require oxygen
o Where is the carbon?
We start with carbon, where does it end up?
o Compare with photosynthesis
The differences, where they occur, how is Calvin cycle similar and different than
Citric acid cycle, the electron transport chain
Glycolysis
o Splitting of glucose
o Occurs in the cytosol in eukaryotic and prokaryotes
Nothing specific about cellular respiration for eukaryotes
o Nothing catalysis the process, very ancient system
o Did not lose any carbon, did not lose any oxygen
o Reduction of NADH, (from NAD+ reduced to NADH), there is less energy in 2 Pyruvate
because some energy is required to make 2 NADH
o Need to consume 2 ATP, but 4 is generated, so a net of 2 ATP is formed
Energy Coupling
o Glucose catalyzed by Hexokinase, not spontaneous, cannot happen by itself
o Half reactions
Pi + glucose -> glucose – 6 – P delta G = + 3.3 KJ/mol
ATP + H2O -> ADP + Pi delta G = - 7.3 kcal/mol
o Coupled reaction:
ATP + glucose -> ADP + glucose – 6 – P delta G = -4 kcal/mol
o Water cannot access the active site
No real hydrolysis happen, the free energy of the phosphate is transferred to
glucose
o But why?
To phosphorylate glucose? A phosphate group is charged, glucose is not charged, so when we add
an charge, we can keep the glucose in the same compartment
Make the glucose more unstable, more reactive, readily to break apart
Substrate-level phosphorylation
o The phosphate group is transferred from Phosphoenol-pyruvate (PEP)
o PEP is very reactive, readily give up phosphate
o With pyruvate kinase PEP can generate ATP
o Phosphoryl transfer potential, readily releases phosphate group to generate ATP
Mitochondria
o Compare structure to chloroplast
o Structures:
Outer mitochondrial membrane
Inner mitochondrial membrane
Intermembrane space
Matrix
Linking Glycolysis and Citric acid cycle
o Cytosol the pyruvate need to move into mitochondrial matrix
o No free energy in the carboxyl group in the pyruvate
o So that it goes through decarboxylation
Release of the CO2
o Dehydrogenase reduces NAD+ to NADH soon after decarboxylation
o Then it adds Coenzyme A, making it more reactive, Acetyl CoA, easier to react with
enzyme to react
o Pyruvate dehydrogenase complex, deals with pyruvate after its being imported from
cytosol to mitochondria
Citric Acid Cycle (CAC)
o When Acetyl-CoA comes in, it’ll loses the CO2
No more carbon from now on
o Get the remaining energy from the acetyl group and linking it to the NADH and FADH2
Consumes NAD+ to produce NADH
o Oxaloacetate is a 4 carbon molecule
o Oxaloacetate binds with the 2 carbons to form a 6 carbon molecule called Citrate
Oxidative phosphorylation
o There are
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