Biochem- Metabolic Brain Flashcards Preview

Clinical Neuroscience > Biochem- Metabolic Brain > Flashcards

Flashcards in Biochem- Metabolic Brain Deck (55)
Loading flashcards...
1
Q

Which strucutres on the BBB limit stuff from getting in?

A

Tight junctions

2
Q

How can water-soluble species to get into the brain?

A

Specific transport systems

3
Q

How can glucose get into the brain?

A

requires GLUT1 and GLUT3 transporters, which have a low Km to allow a constant, eifficient glucose uptake.

4
Q

How can AA’s get into the brain?

A

4 different kinds (2 basic and 2 neutral)

btw I always make the typo “brian” when I mean “brain.” do parents not realize this when naming their kids? sorry to all you brains out there.

5
Q

True or false: the brain is extremely metabolically active and takes up 15% of the total body metabolism at rest

A

True

6
Q

What is the energy mainly used for in the brain?

A

o Transport processes for ion gradients (Na/K ATPase)

o Synthesis of NT’s and neuromodulators

7
Q

What are the 3 things that glucose is used for in addition to an energy source?

A
  1. Synthesis of acetylcholine
  2. Synthesis of glutamate and GABA
  3. As substrate for the PPP to provide NADPH (for fatty acid synthesis and glutathione reductase defense against ROS)
8
Q

What keeps your glucose levels high in acute hypoglycemia?

A

Glycogenolysis in the liver

9
Q

What is the main source of fuel for your brain during acute hypoglycemia?

A

Glucose

10
Q

What is the main source of fuel for your brain during starvation?

A

ketone bodies

11
Q

What are the 2 types of sphingolipids?

A

sphingomyelin and glycosphingolipids.

12
Q

What is sphingomyelin a major component of?

A

neuronal membranes

13
Q

Neimann-Pick- defect

A

Spingomyelinase

14
Q

Type A Neimann-Pick- characteristics

A

Found in the Ashkenazi Jew population. Have <1% of normal acid sphingomyelinase (ASD) activity. Severe form affects kids which has brain damage and die before 4 years old

15
Q

Type B Neimann-Pick- characteristics

A

Have ~10% of normal ASD activity. Little to no neuronal involvement and may live till adulthood

16
Q

Type C Neimann-Pick- characteristics

A

Due to a defect in lipid transport and this an accumulation of cholesterol. Very rare

17
Q

Neimann-Pick- accumulation

A

sphingomyelin and cholesterol (in C&D)

18
Q

Neimann-Pick- Sx

A

hepatosplenomegaly, retardation (in A)

19
Q

Neimann-Pick- Tx

A

None (but ERT can be for B)

20
Q

Gaucher- defect

A

β-glucosidase

21
Q

Type 1 Gaucher- characteristics

A

Chonic non-neuropathic, most common of the spingolipidosis, variable onset, mild, treatable. Brain is unaffected

22
Q

Type 2 Gaucher- characteristics

A

Acute neuropathic, rapidly progressive with death within 2 years.

23
Q

Type 3 Gaucher- characteristics

A

Subacute neuropathic, presents in childhood and death at 2-60 y/o

24
Q

Gaucher- accumulation

A

glucocerebroside

25
Q

Gaucher- Sx

A

Hepatosplenomegaly

  • Mental retard (2)
  • “crumpled tissue paper” gaucher cells
26
Q

Gaucher- Tx

A

Types 1 and 3 are treatable by the administration of β-glucosidase (this is enzyme replacement therapy/ERT)

27
Q

Krabbe- defect

A

β-galactosidase

28
Q

Krabbe- characteristics

A

Macrophage aggregates in multinucleated cells called globoid cells around blood vessels.

29
Q

Krabbe- accumulation

A

galactocerebroside

30
Q

Krabbe- Sx

A

retardation, no myelin

31
Q

Fabry- defect

A

α-galactosidase A

32
Q

Fabry- inheritance

A

XR

33
Q

Fabry- Accumulation

A

ceramide trihexoside

34
Q

Fabry- Sx

A

skin rash, kidney failure

35
Q

Metachromatic leukodystrophy- defect

A

lysosomal sulphatase

36
Q

Metachromatic leukodystrophy- accumulation

A

Sulphatide

37
Q

Tay-Sachs- defect

A

Hexosaminidase A

38
Q

Tay-Sachs- Accumulation

A

Ganglioside Gm2

39
Q

Tay-Sachs- Sx

A

Mental retard, blindness, death in infacny, red spots on macula

40
Q

What pathway uses B12 in the brain?

A

Methylmalonyl CoA mutase reaction- this is a key step in the catabolism of some branched chain AA’s

41
Q

Which reaction uses B12 for the branched-chain AAs?

A

homocysteine –> methionine using N5-methyl THF –> THF

42
Q

What is it called when there is a deficiency in B12?

A

Pernicious anemia

43
Q

What are the Sx of pernicious anemia?

A

megaloblastic anemia with neurological deterioration.

44
Q

What are the structural defects in pernicious anemia?

A

progressive demyelination because of the accumulation of methylmalonyl CoA. Accumulation of this inhibits malonyl CoA carboxylase (a key step in fatty acid synthesis) and it disrupts myelin structure because it substitutes for malonyl CoA in fatty acid synthesis.

n0w/*a91
]]]]]]]]]

45
Q

Abnormally high levels of ammonia (NH3) can lead to what?

A

Coma and death

46
Q

How does the brain normally remove NH3?

A

glutamine synthase reaction, where glutamate –> glutamine

47
Q

Accumulation of glutamine in the brain can cause what?

A

edema

48
Q

How can very high levels of NH3 cause ATP depletion?

A

it would remove alpha-ketoglutarate from the TCA cycle by transaminating it to glutamate for the glutamate synthetase reaction –> depletion of ATP

49
Q

Congenital hyperammonaemia Type I- deficiency

A

CPS

50
Q

Congenital hyperammonaemia Type I- inheritance

A

AR

51
Q

Congenital hyperammonaemia Type I- clinical significance

A

Lethal neonatal and less severe delayed-onset types

52
Q

Congenital hyperammonaemia Type II- deficiency

A

OTC

53
Q

Congenital hyperammonaemia Type II- inheritance

A

XR

54
Q

Congenital hyperammonaemia Type II- clinical significance

A

Most common urea cycle defect.

Treatable with Arg supplements and low protein diet.

55
Q

Btw all the storage diseases are what type of inheritance (except Fabry)?

A

AR