Week 4 (carbohydrate metabolism) Flashcards
How much ATP per hour is used when sleeping?
2-3kg
How much ATP is stored in the muscle?
~95g
How much ATP is used per second during exercise?
53g
How many times is an ATP molecule recycled per day?
1000-1500
Describe substrate-level phosphorylation
Does not require oxygen
Small contribution to total ATP
Describe oxidative phosphorylation
Requires oxygen
Involves respiratory chain (electron transfer)
Main contribution to total ATP.
Name and describe the two coupled processes in oxidative phosphorylation
Electron transport
- transport of electrons through the respiratory chain
- achieved by redox reactions
- formation of water
Phosphorylation
- formation of ATP by ATP synthase
- achieved by proton gradients across membrane
Where does oxidative phosphorylation take place?
Cristae of mitochondria
Each electron transport train contains multiple redox centres; what do these redox centres consist of?
Flavin mononucleotide
Cytochromes (a, b or c)
Iron sulphur cluster
What is flavin mononucleotide?
The initial electron acceptors for complex I and complex II.
It can carry two electrons by transferring one at a time.
What are cytochromes?
One electron carriers.
Iron coordinating porphyrin ring derivatives.
a, b or c differ by ring additions.,
What is coenzyme Q/ubiquinone?
A lipid soluble compound that readily accepts electrons.
A mobile electron carrier transporting electrons from complexes I and II to complex III.
Upon accepting two electrons, it picks up two protons to give an alcohol, ubiquinol.
Ubiquinol can freely diffuse in the membrane, carrying electrons with protons.
What delivers electrons to the electron transport chain?
NADH
FADH
What is the electron transport chain?
A chain of redox reactions that combine electrons and protons with oxygen to form water.
What is required to maintain a proton gradient?
An intact inner mitochondrial membrane.
What is ATP synthase?
Acts as a point of re-entry for hydrogen ions across proton gradient.
Convert osmotic energy to chemical energy.
How many protons (H+) are needed for the synthesis of 1 ATP?
4
What happens as a result of uncoupling of respiration?
Allows the passage of protons across the membrane.
Decreases proton concentration gradient.
What are the three main roles of uncoupling proteins (UCP)?
Cold acclimatisation (heat generation)
Facultative diet induced thermogenesis.
Energy homeostasis.
Name the uncoupling proteins
UCP1 (found in brown adipose tissue)
UCP2 and UCP3 (more widely distributed e.g. muscle)
What do cyanide and carbon monoxide inhibit?
Electron transfer between complex III and IV.
What does the ETC generate?
A proton gradient across the inner mitochondrial membrane (i.e. a charge)
What is potential energy converted into?
Chemical energy (ATP)
What does ATP synthase allow protons to do?
Move back through the inner mitochondrial membrane.
Describe uncoupling proteins
Sit on the inner mitochondrial membrane.
Allow free passage of protons.
Name the order of carbohydrate metabolism
- glycolysis
- pyruvate dehydrogenase
- TCA cycle
- Oxidative phosphorylation
Describe the malate/aspartate shuttle
Enables the NADH produced in the cytosol to enter the matrix of the mitochondria.
Involves the movement of a proton back into the matrix.
There is 1 less proton for ATP synthase for every NADH carried.
Describe the phosphate carriage.
Enables the conversion of GTP to ATP.
GTP produced via the TCA cycle in the mitochondrial matrix leads to ADP phosphorylation to ATP in the cytosol.
