Mitochondrial Synthesis of ATP (Bioenergetics)

Where is most (95%) of ATP produced?

mitochondria

Describe the permeability of the outer membrane of the mitochondria:

freely permeable to small molecules and has no ionic or electrolyte gradients

What is the inner mitochondrial membrane folded into?

christae

Describe the permeability of the inner membrane of the mitochondria:

permeable to a small number of molecules via specific transporters and is a good electrical insulator

True or false: the inner membrane and christae of the mitochondria contain more proteins than lipids

true

What is the area inside the inner membrane of the mitochondria called?

matrix

What does the matrix of mitochondria contain?

a wide range of enzymes involved in the Krebs cycle, fatty acid oxidation and the urea cycle as well as other proteins, cofactors, lipids, ribosomes and DNA

Where does the link reaction take place?

mitochondrial matrix

What enzyme catalyses the link reaction?

pyruvate dehydrogenase

Give two examples of cofactors used by pyruvate dehydrogenase during the link reaction:

1) Mg2+

2) lipoic acid

Give the equation for the link reaction:

Pyruvate + NAD + CoA -> Acetyl CoA + reduced NAD + CO2

What vitamin is pyruvate dehydrogenase reliant on?

vitamin B2/ thiamine

When is pyruvate dehydrogenase inhibited?

when energy levels are high

How many molecules of NADH are produced by the Krebs cycle per molecule of glucose?

6

How many molecules of FADH2 are produced by the Krebs cycle per molecule of glucose?

2

How many molecules of CO2 are produced by the Krebs cycle per molecule of glucose?

4

How many molecules of ATP are produced by the Krebs cycle per molecule of glucose?

2

What is the input molecule in the Krebs cycle?

Acetyl CoA

What are the two main stages of the Krebs cycle?

1) synthesis of a 6-C compound (citrate) into a 4-C compound (succinyl CoA)

2) oxidation of a 4-C compound to regenerate oxaloacetate which initiates another round of the cycle

What controls the Krebs cycle?

the amount of energy found in the cell indicated by levels of ATP, acetyl CoA and NADH

Describe how ATP metabolism differs in diabetic individuals:

they cannot use glucose effectively in the absence of insulin so glycolysis is inhibited. Therefore, pyruvate levels are low and instead, malate and oxaloacetate are removed from Krebs to form glucose. Additionally, fatty acids are mobilised from adipose tissue and are oxidised to acetyl CoA. Ketones also have to be synthesised

What are the two stages of oxidative phosphorylation?

1) electron transport

2) ATP synthesis

Where does oxidative phosphorylation occur?

inner mitochondrial membrane

Where are electrons in the electron transport chain derived from?

NADH and FADH2

What are the names of the 4 proteins in the electron transport chain?

complex I, II, III and IV

How do electrons move down the electron transport chain?

from one protein complex to the next

What happens to electrons once they reach complex IV?

they are donated to oxygen, reducing it to H2O

How is energy produced by the electron transport chain?

each reduction at each complex releases energy

What is the energy produced by the electron transport chain used for?

pumping protons across the inner mitochondrial membrane

Fill in the gaps: from each pair of electrons from NADH, a total __ H+ are translocated

10

How many protons can move through complexes I and III at once?

4H+

How many protons can move through complex IV at once?

2H+

How is ADP transported into the mitochondria?

antiporters in the inner mitochondrial membrane move it into the matrix

How are phosphate molecules transported into the mitochondria?

antiporters paired with H+

How many protons have to move across the inner membrane for the synthesis of 1 ATP molecule?

4

How is NADH moved across the inner membrane of the mitochondria?

it is oxidised to NAD+ and later reduced in the matrix back to NADH

What are uncouplers?

weak acids that can associate with protons in the inter-membrane space and can dissipate the H+ gradient so electron transport can continue without ATP synthesis

Where are uncouplers found in new-borns?

brown adipose tissue (as thermogenin)

Describe how thermogenin is activated in low temps:

when temperature drops, noradrenalin leads to increased concentrations of free fatty acids in cytosol which activates thermogenin

How does thermogenin increase temperatures?

it acts as an uncoupler, keeping the electron transport chain going to produce heat, uncoupled from ATP synthesis