Energy Storage Flashcards

1
Q

List a few cells that are glucose-dependant

A
  • RBCs
  • Neutrophils
  • Kidney medulla cells
  • Lens of the eye
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2
Q

What is glycogen?

A

Glucose stores in the form of granules in muscle and liver

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3
Q

Describe the structure of glycogen

A
  • Chains of glucose residues that is highly branched (through alpha 1-6 glycosidic bonds)
  • Attached to glycogenin (protein dimer) at the centre
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4
Q

Outline the steps of glycogenesis

A

1) glucose —> glucose 6-phosphate
(Hexokinase or glucokinase in the liver)

2) glucose 6-phosphate -> glucose 1-phosphate
(Phosphoglucomutase)

3) glucose 1-phosphate + H2O —> UDP-glucose
(G1P uridylyl transferase)

4) UDP-glucose + glycogen (n residue) —> glycogen (n+1) + UDP
(Glycogen synthase for alpha 1-4
Branching enzyme for alpha 1-6)

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5
Q

Outline the process of glycogenolysis

A

1)Glycogen + Pi —> glucose 1-phosphate + glycogen (n-1)
(Glycogen phosphorylase or debranching enzyme)

2) glucose 1-phosphate —> glucose 6-phosphate
(Phosphoglucomutase)

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6
Q

Compare the uses of glycogen in muscle and liver

A
Liver = blood glucose buffer
Muscle = energy production (no glucose 6-phosphatase)
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7
Q

List the hormones involved in regulation of liver glycogen and what their effect is

A

Glucagon/adrenaline = phosphorylates glycogen synthase or phosphorylase to decrease and increase enzyme activity respectively

Insulin = dephosphorylates glycogen synthase or phosphorylase to increase and decrease enzyme activity respectively

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8
Q

Define what Gluconeogenesis is and list the major precursors

A
Gluconeogenesis is the production of new glucose mainly in the liver but can also occur in kidney cortex.
Major precursors:
-lactate
-glycerol
-amino acids
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9
Q

Why can’t acetyl~CoA can’t be converted to pyruvate?

A

Pyruvate dehydrogenase reaction is irreversible

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10
Q

What are the three key enzymes in Gluconeogenesis?

A

1) Phosphoenolpyruvate carboxykinase (PEPCK)
- oxaloacetate (from pyruvate) to phosphoenolpyruvate

2) Fructose 1-6 bisphosphatase
3) Glucose 6-phosphatase

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11
Q

Which hormones regulate gluconeogensis and what are their corresponding effects?

A

Glucagon/cortisol = stimulate
-by increasing amount of key enzymes

Insulin = inhibit
-by decreasing amount of key enzymes

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12
Q

What is the main lipid molecule used as storage?

A

Triacylglycerols

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13
Q

Where are triacylglycerols stored?

A

Adipocytes in adipose tissue

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14
Q

What is lipogenesis?

A

Fatty acid synthesis

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15
Q

Briefly describe the process of lipogenesis

A

1) Glucose to pyruvate (glycolysis in the cytoplasm)
2) Pyruvate enters mitochondria
3) Pyruvate to Citrate (by adding OAA and acetyl~Coa)
4) Citrate leaves mitochondria and gets cleaved releasing OAA and acetyl~CoA
5) Acetyl~CoA turned to malonyl~CoA by acetyl~CoA carboxylase
6) Malonyl ~CoA turned into fatty acids by fatty acid synthase complex

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16
Q

What is lipolysis?

A

Mobilisation of fat by hydrolysing stores

17
Q

What enzyme is for lipolysis?

A

Hormone sensitive lipase