BIOC 212 Lecture Notes - Lecture 48: Intermembrane Space, Malate Dehydrogenase, Enzyme
29 May 2018
School
Department
Course
Professor
Metabolism X
Active Transport
• Pyruvate importer focused on extensively
o Comes into the mt by protein complexes that use active transport
o Pyruvate requires active transport to the mitochondrial matrix
• Lots of different ways in which active transport can work
o Pumps using ATP (Na/K pump) to push both substrates across
o Symporters or antiporters
• Use one gradient to move other ion against [c] gradient
o Use some component of electrochemical gradient in the membrane
• Turn chemical energy from glycolytic products into energy for feeding
electrochemical gradient on the mt inner membrane
• Pyruvate and other soluble molecules that cannot cross the inner membrane on
their own require protein transporters to pump them into the matrix
• The pH gradient drives pyruvate and phosphate importers, while the voltage
gradient is required to exchange ATP for ADP
o pH gradient requires for driving pyruvate & phosphate into the mt inner
matrix
o Voltage gradient needed for permitting exchange ATP --> ADP
• ATP is more negatively charged than ADP
• Exchange across membrane where outside of membrane is + is
favorable for the more negatively charged ATP vs. less negatively
charged ADP
• Balancing out membrane potential more efficiently by exporting ATP
and importing ADP
o As soon as include reagents that disrupt the electric gradient across
membrane, lose pressure to diffuse ATP out of the mt
• Stop being able to use ADP in the cytosol
• Compounds that make membrane permeable to protons, but will maintain the
potential gradient
o Shown that the electric gradient on its own is not required for pyruvate
import, but the pH gradient is
NADH
• NADH is transported in a different way
o NADH & NAD+ are not known to be able to cross biological membranes at
all
o No known protein transporters for them
o Not enclosed in vesicles
