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energy II Flashcards

1
Q

what are the key properties of aerobic respiration

A
  • Occurs only in the presence of oxygen
  • Yields more ATP than is produced in glycolysis.
  • Requires the TCA cycle and oxidative phosphorylation
  • Takes place in the mitochondria
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2
Q

what does acetyl co)A) react with to form citrate ?

A

Oxaloacetate

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3
Q

the TCA cycle - lead to the synthesis of ATP

A

does not directly

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4
Q

acetly coA can also be the entry point for what?

A

the breakdown products of both fatty acids and proteins.

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5
Q

what is the net result for each glucose molecule that enters glycolysis and then the tca cycle

A

o 6 NADH + 2NADH are formed as pyruvate is converted to acetyl co A.
o 2 FADH2
o 2 GTP
o 4 C02. + C02 as pyruvate is converted to acetyl co A.

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6
Q

where does the TCA cycle take place?

A

mitochondrial matrix

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7
Q

is the tca cycle aerobic or anerobic

A

aerobic unlike glycolysis

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8
Q

what does the tca cycle oxidise acetly coA to generate

A

NADH, FADH2, GTP and CO2

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9
Q

what is the aim of the kreb cycle

A

producing NADH, FADH2 which become substrates for the electron transport chain

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10
Q

what regulates entry into the TCA cycle

A

pyruvate dehydrogenase. It regulates the conversion of pyruvate to acetyl Co A.
• Inhibited by its products NADH and Acetyl CoA
• Also regulated through phosphorylation by a kinase and a phosphatase

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11
Q

How is pyruvate dehydrogenase regulated

A
  • In the inactive form, the enzyme is phosphorylated.
  • In the active form, the enzyme is dephosphorylated.
  • Phosphorylation occurs through pyruvate dehydrogenase kinase and the removal of the phosphate by pyruvate dehydrogenase phosphatase.

-• Build up of NADH and acetyl CoA informs the enzyme that the energy needs of the cell are being met or that fatty acids are been broken down to produce NADH and acetyl CoA. This has the effect of sparing glucose.

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12
Q

how is pyruvate dehydrogenase stimulated in the muscle

A

• In muscle pyruvate dehydrogenase phosphatase is stimulated by Ca2+ this is because calcium is involved in muscle contraction. Muscle contraction requires ATP, so in the absence of phosphate, the pyruvate dehydrogenase enzyme will be active, allowing ATP to be synthesised.

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13
Q

How is calcium increased in the liver ?

A

• In liver adrenalin increases Ca2+ through the activation of alpha-adrenergic receptors and IP3

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14
Q

In the liver and adipose tissue how is pyruvate dehydrogenase stimulated ?

A

• In liver and adipose tissue, insulin (which signifies the fed state) stimulates the phosphatase which funnels glucose to Fatty Acid synthesis

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15
Q

explain how the tca cycle is regulated

A
  1. Pyruvate dehydrogenase which regulates the entry into the TCA cycle. It is inhibited by NADH, ATP, acetyl CoA. It is stimulated by ADP(reductionofATP) and pyruvate.
  2. Citrate synthase – first point within the cycle itself . It is negatively regulated by its product citrate
  3. Isocitrate dehydrogenase and alpha-ketoglutarate dehydrogenase. Isocitrate dehydrogenase is inhibited by NADH and ATP, and is stimulated by ADP.
    Alpha-ketoglutarate dehydrogenase – inhibited by NADH, ATP, and its product succinyl CoA.
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16
Q

which 2 control points integrate the CAC with other pathways. explain what those pathways are.

A

Inhibition of isocitrate dehydrogenase and keto glutarate dehydrogenase leads to the build up of citrate. Citrate is transported out of the mitochondria where it inhibits PFK which stops glycolysis. The citrate will also act as a source of acetyl CoA for FA synthesis

17
Q

what is beriberi

A
  • Is a deficiency in thiamine (Vit B1)
  • Common where rice is a staple
  • Characterised by cardiac and neurological symptoms as glucose is the most common substrate for neuronal tissue.
  • Thiamine is a prosthetic group for pyruvate and a-ketoglutarate dehydrogenase
  • Neurological problems are common as glucose is the primary source of energy
18
Q

in aerobic respiration, what does the flow of electrons terminate with?

A

molecular oxygen being the final electron acceptor, generating water

19
Q

what forms an electrochemical gradient

A
  • Flowing from complex 1 to 4 there is a reduction in energy, which means the electrons flow from a high energy state to a low energy state.
  • This imparts energy to the transport of protons across the inner mitochondrial membrane.
  • This forms an electrochemical gradient which can be used to generate ATP.
20
Q

in the etc what do electrons pass through ?

A

cytochromes

21
Q

what is used to generate ATP

A
  • The proton gradient
22
Q

how does ATP Synthase generate ATP?

A
  • As electrons are passed down the ETC, protons are pumped from the matrix to intermembrane space and then forms a gradient.
  • The gradient of protons is dissipated by the passage of protons through the enzyme ATP synthase.
  • Atp synthase is a molecular engine and as protons pass through it, ATP is formed.
  • Thus the process relies on the fact that the inner mitochondrial membrane is very impermeable to many molecules.
23
Q

describe a circumstance when ETC generation of protein gradient and atp synthesis is not tightly linekd

A
  • In the normal white fat, the majority of the space within the cell is filled with lipid.
  • In the brown fat, the predominant feature is the large number of mitochondria present. These mitochondria, because they contain cytochromes and cytochromes are coloured due to the heme they contain, gives the lipid a brown colour.
    Its used to generate heat as infants have not developed the shivering reflex. HOW?
  • in brown fat, they express a protein called uncoupling protein 1, UCP-1. UCP-1 diverts the flow of protons away from the generation of ATP to the generation of heat.
  • So it dissipates the gradient and generates heat
24
Q

what are the oxphos diseases

A
  • Common degenerative diseases
  • Caused by mutations in genes encoding proteins of ETC
  • Symptoms, including fatigue, epilepsy, dementia
  • Dependent on the mutation, symptoms may be evident near birth to early adulthood
  • Metabolic consequence can be congenital lactic acidosis
25
Q

what leads to the generation of heat?

A

regulated uncoupling

26
Q

what does pyruvate dehydrogenase do and what is it inhibited and stimulated by?

A

→converts Pyruvate to Acetyl CoA
→ inhibited by NADH, ATP, Acetyl CoA -

→stimulated by ADP and Pyruvate

27
Q

what does citrate synthase do and what is it inhibited by?

A

→joins Oxaloacetate and Acetyl CoA to make Citrate

→ inhibited by citrate

28
Q

what does isocitrate dehydrogenase do and what is it inihbited and stimulated by

A

→it converts Isocitrate to α-ketoglutarate
→inhibited by NADH and ATP

→ stimulated by ADP

29
Q

what does α ketoglutarate dehydrogenase do and what is it inhibited by?

A

→catalyses the conversion of α-ketoglutarate to succinyl-CoA

→inhibited by NADH, ATP and Succinyl CoA

flc (29 decks)

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