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Lecture 7

BIOC 3300 Lecture Notes - Lecture 7: Electrochemical Gradient, Permease, Membrane Transport Protein


Department
Biochem & Molecular Biology
Course Code
BIOC 3300
Professor
Mc Leod Roger
Lecture
7

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1. What is the overall
permeability of the
IMM?
Permeable to small,
uncharged, and hydrophobic
molecules (Water, O₂ and CO₂
pass easily)
2. What is the overall
permeability of the
OMM?
Leaky, no appreciable barrier
3. What about carboxylic
acids allows them to
pass through the
membrane more easily?
They have high pKa's,
meaning that they are usually
protonated at physiological
conditions = can pass
through the membrane more
easily
4. What is the degree of
difference in membrane
diffusion between
monocarboxylates and
di/tricarboxylates?
monocarboxylates are 100-
1000X faster diffusers
5. What keeps TCA
intermediates within
the mitochondrial
matrix?
Most intermediates are
di/tricarboxylates (which very
slowly diffuse across the
membrane, so stay in matrix)
6. How can ion transport
across membranes
creating a charge and
osmotic gradients be
overcome?
By co-transporting an ion of
opposite charge or couter-
transporting an ion of like
charge
*COUNTER TRANSPORT IS
PREFERRED SOLUTION*
7. What will the charge
species of phosphate
be at neutral pH?
HPO₄²/ H₂PO₄⁻
8. What will be the species
and mode of transport
for influx of H₂PO₄⁻
into the matrix?
HPO₄in and OH out
9. What will be the species
and mode of transport
for influx of HPO₄²
into the matrix?
HPO₄²and 2Hin
10. Why does the presence
of a proton gradient
favour influx of
phosphate into the
mitochondrial matrix?
Because exported hydroxyl
will be trapped as water in the
intermembrane space
(neutralizing the proton
gradient)
11. What is the most
abundant
mitochondrial
membrane transporter?
Adenine nucleotide
transporter (translocase)
12. How is Adenine
Nucleotide
Transporter regulated,
and what uptake
mode does it favour?
Membrane potential; favours
uptake of ADP and export of
ATP
13. What are the two
different states of
Adenine Nucleotide
Transporter, and what
uptake modes do they
favour?
*'m' state* -- ADP release and
ATP uptake
*'c' state* -- ATP release and
ADP uptake
*c IS GOOD FOR ATP RELEASE*
14. For monocarboxylates,
what determines the
speed of passive
diffusion?
overall size and overall charge
15. What is the
mechanism of
pyruvate permease
transport?
*Symport* -- via a proton
gradient
16. What is the
mechanism of
malate/succinate
permease transport?
*Antiport* -- uptake of
malate/succinate and release of
HPO₄²(which then reenters the
matrix via phosphate
transporter in exchange for
OH)
17. What ensures no net
movement of
phosphate?
export by malate/succinate
permease transporter and α-
ketoglutarate transporter, and
then immediate import by the
phosphate transporter back into
the matrix
18. What makes the
matrix [oxaloacetate]
very low?
*There is no oxaloacetate
transporter*, and its constant
usage in the TCA cycle
19. What is exchanged for
α-ketoglutarate
through the α-
ketoglutarate
permease transporter?
Malate
20. What 3 compounds
does the citrate
permease transporter
transport, and what is
it dependent on?
citrate, isocitrate, and cis-
aconitate
Dependent on phosphate
transporter
21. What is exchanged for
glutamate through
the glutamate
permease transporter?
Import of glutamate in
exchange for OH
Lecture 7 - Mitochondrial Transporters
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