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Lecture 7

Biology 2601A/B Lecture Notes - Lecture 7: Superoxide, Reactive Oxygen Species, Electron Transport Chain

Course Code
BIOL 2601A/B
Jennifer Taylor

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Lecture 7: Mitochondria
Roles of Mitochondria
“Powerhouses” of the cell
Regulation of metabolism
Cell cycle control
Immune response
Cell signaling
Mitochondrial Structure
Pores let molecules in and out
Inner membrane has lots of folds, because the enzymes involved in mitochondrial
metabolism are found here
- More folds means more surface area, so more room for the enzymes to be
Inner space is the matrix
Ribosomes for translation of gene products and proteins
Freeze-fracture in yeast reveals mitochondrial “reticulum”
- Mitochondria can fuse together to form a network of tubes
- Purpose is more efficiency
Mitochondrial DNA
Encodes 37 genes in humans (nuclear DNA has more genes)
Mitochondria has a separate genome from the nuclear genome
It’s a circular plasmid
All genes it encodes are used in mitochondrial metabolism
Endosymbiotic Theory
Where did mitochondria come from?
Ancestral cells didn’t have mitochondria
This theory states that all old cells aren’t capable of aerobic metabolism (since
they don’t have mitochondria)
There’s a separate bacterium (one that looks like mitochondria)
The cell with no mitochondria engulfs the bacterium, and membrane folds around
it, becoming an organelle
This is a symbiotic relationship between the cell without aerobic respiration and
the bacterium resembling mitochondria

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The cell is now able to do oxidative metabolism due to the mitochondria
This is why mitochondria has its own genome  it evolved separately from the cell
Role of Mitochondria
Primary role is to produce ATP
ATP is energy that can be transported anywhere
It’s a high energy molecule because you can break off one phosphate
Before mitochondria, cells relied on anaerobic metabolism, which was glycolysis
This wasn’t very efficient
You an investment of 2 ATP, and produce 4 ATP net production is 2 ATP
Total products: 2 ATP, 2 NADH, 2 pyruvate
The Citric Acid Cycle (TCA)
Take products from glycolysis and creates ATP
Uses pyruvate and in one cycle makes 4 NADH and 1 ATP
Electron Transport Chain
Found in the mitochondria
Composed of subunits (separate proteins) that are encoded by separate genes
Complex III and IV have proteins encoded by mitochondrial DNA
Substrates are oxidized in the first two complexes as NADH it turned to NAD+
- Electrons are transported from electron donors to acceptors, releasing energy
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