Mitochondria and Chloroplasts (2)
Mitochondria
Matrix: enzymes of citric acid cycle, mitochondrial DNA, etc
Inner membrane: electron transfer proteins, ATP synthase, transport
proteins
Outer membrane: has large pores, lipid synthesis, and conversion of lipid
substrates into forms that can be metabolised in the matrix
Intermembrane space: several enzymes that use ATP passing out of the
matrix to phosphorylate other nucleotides
Product yields from glucose oxidation:
In the complete oxidation of glucose the majority of the ATP is generated
by ATP-synthase. The exceptions are the 2 ATP from glycolysis and the 2
GTP (GTP and ATP are equivalent in terms of having high energy
phosphate bonds) from citric acid cycle. NADH and FADH2 feed high
energy electrons into electron transport chain (ETC). The energy from the
electrons is used to pump protons generating the proton gradient. Proton
gradient powers the ATP synthase. Note that the NADH generated in
glycolysis cannot feed electrons directly into the ETC. Transporting these
NADH into mitochondria requires energy so the net ATP yield is lower from
these NADH molecules.
Summary of oxidative phosphorylation:
, Some agents that interfere with oxidative phosphorylation:
Cyanide and carbon monoxide inhibit cytochrome oxidase.
Block the passage of electrons to oxygen.
ATP synthesis grinds to a halt.
Redox potential:
Redox potential increases along ETC. Free energy of electrons decreases.
Chloroplasts:
Function of chloroplasts is to harvest energy from sunlight, convert it to
chemical energy and use this chemical energy to fix carbon from the
atmosphere (CO2) into sugars.
General features of photophosphorylation:
The electrons that get passed along the ETC in chloroplasts come from
water. Unlike NADH, H20 is a poor donor of electrons. Requires energy
input in the form of light to create a good electron donor and extract the
electrons from water.
Generation of proton gradient across the thylakoid membrane:
Again, as in mitochondria, electron transfer is coupled to proton pumping.
Also, protons released upon water oxidation contribute to the
electrochemical proton gradient.
Mitochondria
Matrix: enzymes of citric acid cycle, mitochondrial DNA, etc
Inner membrane: electron transfer proteins, ATP synthase, transport
proteins
Outer membrane: has large pores, lipid synthesis, and conversion of lipid
substrates into forms that can be metabolised in the matrix
Intermembrane space: several enzymes that use ATP passing out of the
matrix to phosphorylate other nucleotides
Product yields from glucose oxidation:
In the complete oxidation of glucose the majority of the ATP is generated
by ATP-synthase. The exceptions are the 2 ATP from glycolysis and the 2
GTP (GTP and ATP are equivalent in terms of having high energy
phosphate bonds) from citric acid cycle. NADH and FADH2 feed high
energy electrons into electron transport chain (ETC). The energy from the
electrons is used to pump protons generating the proton gradient. Proton
gradient powers the ATP synthase. Note that the NADH generated in
glycolysis cannot feed electrons directly into the ETC. Transporting these
NADH into mitochondria requires energy so the net ATP yield is lower from
these NADH molecules.
Summary of oxidative phosphorylation:
, Some agents that interfere with oxidative phosphorylation:
Cyanide and carbon monoxide inhibit cytochrome oxidase.
Block the passage of electrons to oxygen.
ATP synthesis grinds to a halt.
Redox potential:
Redox potential increases along ETC. Free energy of electrons decreases.
Chloroplasts:
Function of chloroplasts is to harvest energy from sunlight, convert it to
chemical energy and use this chemical energy to fix carbon from the
atmosphere (CO2) into sugars.
General features of photophosphorylation:
The electrons that get passed along the ETC in chloroplasts come from
water. Unlike NADH, H20 is a poor donor of electrons. Requires energy
input in the form of light to create a good electron donor and extract the
electrons from water.
Generation of proton gradient across the thylakoid membrane:
Again, as in mitochondria, electron transfer is coupled to proton pumping.
Also, protons released upon water oxidation contribute to the
electrochemical proton gradient.
