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26 Cards in this Set

  • Front
  • Back
what are the functions of the mitochondria?
produce ATP via aerobic metabolism

sequester calcium, protecting cell from toxic levels

role in cell death via necrosis and apotosis

generate heat in brown fat cells
what is the morphology of a mitochondria?
cytoplasmic organelle w/ double mbn

can change shape (sheprical to filamentous)

can change from orthodox <-> condensed:
-orthodox: low levels of ATP produced, large mtx, small intermbn space
-condensed: high levels of ATP produced, small mtx, large intermbn space
how do mitochondria divide?
by fission; separate from cell mitosis
what is the outer mbn of the mit composed of?
has pores composed of channel-forming protein called porin

highly permeable to <5kDa

has enzymes to break down lipids
what is the inner mbn of the mit composed of?
enriched in unusual lipid (cardiolipin)

highly IMpermeable to macromolecules/ions unless a transporter is present

cristae increase SA, which increases ATP synth; form adhesion sites b/w inner and outer mbns

3 types of proteins: proteins for oxidative rxns of resp chain, ATP synthase, transport proteins
what is in the intermembrane space of the mit?
enzymes that use ATP ot phosphorylate other nucleotides
what is in the matrix of the mit?
enzymes for oxidative metabolism
enzymes of TCA cycle
DNA for mtDNA
mit ribosomes
mit RNAs
calcium granules
how can you stain for mit?
H&E, but nonspecific

acid haematein (LM), specialized

histochemical localization of mit enzymes for both LM and EM (i.e. cytochrome oxidase, succinate dehydrog)
describe oxidative phosphorylation in mit.
1. production of acetylCoA in mtx from pyruvate and fatty acids

2. oxidation of acetyl CoA in TCA -> NADH & FADH2 produced in mtx

3. ETC in inner mbn
a. electron pairs from NADH & FADH2 enter ETC of proteins, finally transfer to O2
b. during e- transport, H+ moved from mtx to intermbn space, creating an electrochem proton gradient (pH increased in mtx)

4. synthesis of ATP from ADP + Pi by ATP synthase of inner mbn, using energy from protons flowing down gradient
how do brown fat cells utilize mit?
uncouple oxidation from ATP synthesis

generates heat

special transport protein allows H+ to move freely down gradient

oxidation occurs more rapidly and energy dissipated as heat
how do symport carrier proteins work?
energy for transport is derived from flow down an electrochem gradient in the SAME direction as transport
how do antiport carrier proteins work?
energy for transport is derived from flow down an electrochem gradient in the OPPOSITE direction as transport
How do proteins get targeted to the outer mbn of the mit?
hydrophobic sequence of protein inserts into membrane, then assumes its final conformation

NO cleavable signal sequence is required (except to mit proteins)
How do proteins get targeted to the matrix of the mit?
Signal sequence is required.

1. proton gradient necessary. ATP hydrolysis provides energy

2. protein entry occurs at contact sites b/w outer and inner mbns, where proteins can cross both at once. proteins cross through translocases:
-TOM complex - in outer mbn
-TIM complex - in inner mbn

3. import requires HSP70 protein and ATP (used to release HSP70 after entry or cause conformational change in HSP70 to pull protein into mtx)
How do proteins get targeted to the inner mbn and intermbn space of the mit?
Requires TWO signal sequences.

1. TOM/TIM23 cleaves 1st signal in mtx, which unmasks the 2nd hydrophobic sequence for the inner mbn

2. protein is released into free mtx and then reinserted into inner mbn OR 2nd seq is a stop transfer seq, leaving protein bound in inner mbn

proteins for intermbn space are first inserted into inner mbn, then cleaved from 2nd signal by protease
what is the mit genome made up of?
circular dsDNA in mtx, usual multiple copies
what does mtDNA code for?
2 rRNAs
13 proteins (subunits of resp enz complexes + ATP synthase)
22 tRNAs
who regulates mtDNA transcription, protein synth, DNA replication, and growth/division of mit?
since there are only 22 mt tRNA's, what does this mean in terms of wobble?
greater wobble because less tRNAs than in cytoplasm
how does the mutation rate compare in mit?"
10x greater mutation rate in mit
what happens to mit in necrosis?
1. calcium levels in cytosol increase, mit takes up calcium and water follows

2. mit swells/bursts, releasing toxic levels of Ca into cyto, activating enz that degrade cellular components

3. porins in outer mbn align with transport proteins in inner mbn, forming a mit permeability transition pore that releases Ca into cytoplasm
what happens to mit in apoptosis?
requires ATP

cytochrome c is released from mit into cyto, forming complex w/ ATP, Apaf-1, and procaspase9

apoptosis triggered when inactive procaspase9 self cleaves to caspase 9
what is parkinsonism?
reduced fxn of respiratory enzyme complex in mit
what is primary hyperoxaluria?
improper targeting of peroxisomal enz to mit
what is the endosymbiotic hypothesis?
early prok cell internalized by anaerobic euk cell
what tissues do heritable metabolic disorders of oxidative phosphorylation affect?
tissues w/ high energy requirements

nervous sys, muscle, liver, kidney