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Lecture 7

BIOB10H3 Lecture Notes - Lecture 7: Atp Synthase, Isoleucine, Cytosol

Biological Sciences
Course Code
Tanya Da Sylva

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Mitochondria evolution
Arose from phagocytosis of aerobic prokaryote
Can divide in the cell
Mitochondrial fission
powerhouse of the cell
Site of aerobic respirations
Mitochondria functions
Site of aerobic respiration
Utilizes oxygen to extract energy from macromolecules and converting it to
-Primarily from glucose: ATP production.
Mitochondria ATP production
We use 2 X 1026 molecules of ATP a day
-ATP: cells energy source: energy is released when ATP is hydrolyzed to ADP
Amount of mitochondria in cells depends on energy needs
many mitochondria in: muscle cells, liver cells, fat cells, plant cells & sperm
Mitochondria Structure
Usually sausage-shaped but can be spherical (early embryos) or elongate,
threadlike (fibroblasts)
-0.2 -2 um in cross-sectional diameter & 1-4 um in length (similar in size to
Size and number of mitochondria reflect energy needs of the cell
Dynamic structures

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Change shape, move from place to place in cytoplasm
Mitochondria can fuse with one another, or split in two.
The balance between fusion and fission is likely a major determinant of
mitochondrial number, length, and degree of interconnection.
Inner and outer mitochondrial membranes enclose two spaces
-The matrix and the Intermembrane space
Outer mitochondrial membrane is outer boundary
Inner mitochondrial membrane subdivided into 2 interconnected domains
Inner boundary membrane
Cristae: where the machinery for ATP is located
Phase-contrast light microscope can be picked up
Bright field stain:
To see inner membrane structure light microscope is not enough:
Outer Mitochondrial Membrane (OMM)
~ 50% protein: very porous
Porin proteins large channels : Bacteria-like Beta pleated sheets.
Allows very large molecules in
Inner Mitochondrial Membrane (IMM)
~ 75% protein
Unusual lipid composition
-No cholesterol, rich in cardiolipin: typical of bacterial plasma membranes
-like bacterial plasma membranes

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Highly impermeable
Requires channels and pumps
Over 100 different proteins
Electron transport chain (ETC)
-IMM forms cristae-many thin folds to increase the surface area
Mitochondrial Matrix
Gel-like, from high protein concentration
Contains circular DNA molecule(s), ribosomes and tRNA
Mitochondrial DNA encodes for 37 genes
However, mitochondrial function requires 3000 proteins
Mitochondria proteins are completely translated on free ribosomes in cytosol
Proteins must then be imported into the mitochondria
Posttranslational uptake of proteins into mitochondria
IMM integral proteins: includes all the proteins of the ETC and the ATP synthase.
Matrix proteins: includes all the enzymes of the Krebs / citric acid cycle.
How do mitochondria make ATP?
Start with Glucose (or amino acids, or glycerol and fatty acids)
Series of chemical reactions
-Performed by enzymes (proteins)
Acts on substrates (targets) to produce a chemical change in the substrate
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