Biochemistry 1.6 Flashcards Preview

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Flashcards in Biochemistry 1.6 Deck (21)
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1
Q

What fuels brain metabolism?

A

glucose

2
Q

What is the significance of sufficiently low blood glucose?

A

brain death

3
Q

How is glucose transported?

A

facilitated diffusion through GLUT transporters

4
Q

How does glucose get trapped inside of a cell?

A

travel into cells down a concentration gradient without use of energy; cannot go against concentration gradient to leave

5
Q

What is the GLUT receptor(s) of the liver?

A

GLUT2

Km = 300 mg/dL

6
Q

What is the GLUT receptor(s) of adipose tissue?

A

GLUT4

Km = 90 mg/dL

7
Q

What is the GLUT receptor(s) of muscle?

A

GLUT4

Km = 90 mg/dL

8
Q

What is the GLUT receptor(s) of the brain?

A

GLUT1
GLUT3

Km = 20 mg/dL

9
Q

What is Km?

A

Michaelis constant of an enzyme; indicates the concentration of a substrate which is sufficient for the rate of catalysis to be half of the maximum rate of catalysis

10
Q

What are astrocytes?

A

the workhorse cells of the brain, play many roles to support neurons.
Astrocytes absorb glucose directly through the BBB, to make glycogen as an energy buffer for neurons

11
Q

What is the role of glycogen phosphorylase in astrocytes?

A

hydrolyze glycogen to glucose-6-phosphate

12
Q

Why don’t astrocytes release glucose directly, but instead oxidize glucose to lactate?

A

No glucose-6-phosphatase activity

13
Q

Which type of metabolism acts in astrocytes?

A

anaerobic

14
Q

Which type of metabolism acts in neurons?

A

aerobic

15
Q

What is the order of brain metabolism of glucose?

A

1) anaerobic metabolism of glucose to lactate in astrocytes

2) aerobic metabolism of lactate in neurons

16
Q

What can the brain do to compensate during brain starvation?

A

supplement its fuel supply by substituting ketone bodies for glucose (acetoacetate and D-b-hydroxybutarate)

17
Q

How can the brain use fat?

A
  • cannot burn fat
  • fat cannot be converted to glucose
  • fat CAN yield fuel and for 2-C skeletons to produce ketone bodies (soluble in the blood)
18
Q

Where are fatty acids released and converted into ketones?

A

from adipose tissue to liver to brain

19
Q

When fatty acid is oxidized to acetyl-CoA by the liver, why is the product not directly sent to the brain?

A

When in the blood stream, Acetyl-CoA would be altered by other enzymes; actual ketone bodies are de-protonated and soluble in the blood and BBB

20
Q

What is 90% of the fat in the body stored as?

A

triglycerols; lipase converts to glycerol + free fatty acids

21
Q

What is the precursor to cholesterol?

A

3-hydroxy-3-methyl glutaryl CoA (C-C bonds)