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Neuro 1 Midterm > Biochemistry > Flashcards

Biochemistry Flashcards

0
Q

What vision receptor is responsible for dim light and black/white?

A

Rods (100 million)

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1
Q

What vision receptor is responsible for bright light and color vision?

A

Cones (3 million)

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2
Q

TQ: The tissue that has the highest respiratory quotient (uses the most oxygen) in the entire body is the:

A

Retina

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3
Q

The inner segment of a Rod cell contains a lot of:

A

Mitochondria

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4
Q

In the dark, the Na+ channels are open and the Rod cell is ________.

A

Depolarized

-The signal is an inhibitory signal to make sure the brain doesn’t receive anything

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5
Q

In the light, the Na+ channels are closed and the Rod cell is ________.

A

Hyperpolarized (only a little NT is released)

-No NT … no inhibition … signal to the brain

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6
Q

The intermediate between the light coming in a causing some change in the Outer Segment of a Rod cell and the closing/opening of channels is:

A

cGMP (second messenger)

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7
Q

The disc membrane of the Outer Segment of Rod cells functions via what type of receptor?

A

G protein-coupled receptor system

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8
Q

Mutation in rhodopsin kinase or peripherin may result in:

A

Retinitis Pigmentosum (RP)

  • Deposits in the back of the eye and vision loss
  • Result of a misfolding event of protein
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9
Q

What ion channel is on the surface membrane of the outer segment of the Rod cell?

A

Na+ channels (Na+/Ca++ exchanger

  • Dark = open all the time (“tonic depolarization” … high cGMP)
  • Light = cGMP decreases, then Na+ channels close
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10
Q

Describe the photoreceptor protein.

A

7TM Receptor (rhodopsin and B2-adrenergic are similar) in the disc membrane of the outer segment of a Rod cell

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11
Q

Extradiscal (cytoplasmic) space on rhodopsin has a binding region for: (3 proteins)

A
  • Transducin
  • Rhodopsin kinase
  • Arrestin (beta-arrestin involved in recovery of that signal)
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12
Q

Retinal is a derivative of vitamin __, and contributes to the mature structure of rhodopsin.

A

Vitamin A

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13
Q

Retinal is linked to lysine 296 in opsin by a Schiff-base linkage.
-In the resting state of rhodopsin, the Schiff base is (protonated/unprotonated).

A

Resting state = rhodopsin is protonated

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14
Q

The 500-nm absorption maximum for rhodopsin strongly suggests that the Schiff base is (protonated/unprotonated)

A

500-nm absorption maximum –> protonated

-protonated Schiff base absorbs at 440 nm or longer wavelengths

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15
Q

What happens to 11-cis-retinal when met with a photon?

A

Change in configuration (converts to all-trans), resulting in the shutting down of channels and hyperpolarization

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16
Q

What two color photoreceptor proteins are on the same X chromosome?

A

Red opsin and green opsin

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17
Q

Recombination pathways (crossing over on chromosomes) lead to:

A

Color blindness

-typically on the C-terminus end

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18
Q

Very small AA changes between red, green, and blue opsins contribute to their:

A

Specificity

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19
Q

Continuous renewal of:

A

Outer segment

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20
Q

Dystrophic diseases, such as Retinitis Pigmentosa, occur due to the:

A

Inability to have decent renewal proteins in the outer segment
-related to diet/nutrition

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21
Q

Macular carotenoids (technically, xanthophylls): (2)

A
  • Lutein

- Zeaxanthin

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22
Q
  • Night blindness (retinal)
  • Xerophthalmia (inability to produce tears)
  • Keratinization of epithelium in GI, resp & genitourinary tract
  • Skin becomes dry and scaly
A

Vitaman A deficiency

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23
Q

Best way to increase vitamin A is via:

A

Diet

-orange vegetables

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24
Q

What two segments are involved in the retinoid cycle?

A
  1. Rod outer segment

2. Retinal Pigment Epithelium (RPE)

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25
Q

TQ: After photon converts 11-cis-retinal to an all-trans version in the outer segment, what happens in the RPE?
Why is this important clinically?

A
  • all-trans retinol –(LRAT)–> all-trans retinyl ester –(RPE65)–> 11-cis retinol (leaves RPE back to Rod outer segment)
  • problems with LRAT and RPE65 contribute to Retinitis Pigmentosa and Labor Congenital Amaurosis
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26
Q

TQ: Principles of signal transduction:

A 
Signal -> 
Reception -(Amplification)->
Transduction ->
Response(s)
-Feedback pathways regulate the entire signaling process
-Think about this in terms of vision
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27
Q

Describe the event when a photon reaches retinal on a photoreceptor cell.

A
  • Photon interacts with retinal, changing from 11-cis to all-trans conformation
  • Opsin therefore undergoes a conformational change
  • Opsin activates Transducin (G protein), which then activates Phosphodiesterase (PDE)
  • PDE breaks down cGMP, therefore Na+ channels close
  • -> Hyperpolarization
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28
Q

Cone cells are different from Rod cells in that instead of having discs, they have:

A

An invagination of their surface membrane

-The signal transduction event occurs simultaneously as Rods

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29
Q

Light-induced lowering of Ca++ levels coordinates:

A

Recovery

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30
Q

Describe the steps for signal termination.

A
  1. Rhodopsin kinase phosphorylation the C-terminus of rhodopsin at serine and threonine online residues.
  2. Arrestin (inhibitory protein) then binds phosphorylated rhodopsin and prevents additional interaction with transducin.
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32
Q

Activation: [cGMP] _______ -> ion channels closed ->
Recovery: [Ca++] decreases -> guanylate cyclase activity increases -> [cGMP] _______

A

Activation: [cGMP] decreases -> ion channels closed ->
Recovery: [Ca++] decreases -> guanylate cyclase activity increases -> [cGMP] increases

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33
Q

How many transducin does rhodopsin activate?

A

1 rhodopsin activates 500 transducin

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34
Q

Amplification steps in energy transduction:

A
  • 1 rhodopsin activates 500 transducin

- PDE has a good turnover as it breaks down cGMP to GMP (rapid break down)

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35
Q

(high/low) K+ and (high/low) Na+ inside neurons generates a membrane potential

A

HIGH K+ and LOW Na+ inside neurons generates a membrane potential

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36
Q

catecholamines (dopamine, norepinephrine, epinephrine) all start from what AA?

A

L-tyrosine

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37
Q

L-tyrosine is also synthesized in the liver from what AA?

what enzyme is used?

A
  • phenylalanine

- phenylalanine hydroxylase

38
Q

what enzyme and cofactor participate in the conversion of L-tyrosine to Dopa?

A

tyrosine hydroxylase and tetrahydrobiopterin (cofactor)

39
Q

what enzyme converts Dopa to dopamine?

A

dopa decarboxylase

40
Q

what enzyme converts dopamine to norepinephrine?

A

dopamine beta-hydroxylase (DBH)

41
Q

what enzyme converts norepinephrine to epinephrine?

A

phenylethanol-amine N-methyl-transferase

42
Q

name the correct chemical process sequence of catecholamine synthesis

A
  1. hydroxylation
  2. decarboxylation
  3. hydroxylation
  4. methylation
43
Q

what transporter takes up NTs into storage vesicles?

A

vesicle monoamine transporter 2

VMAT2

44
Q

granules of NT that form a complex with ATP and acidic proteins

A

chromogranins

45
Q

inactivation (degradation) of catecholamines by way of two enzymes:

A
  • catechol-O-methyltransferase (COMT)

- monoamine oxidase (MAO)

46
Q

COMT requires SAM, which uses what two vitamins?

A

B12

folate

47
Q

dopaminergic neurons present chiefly in the: (3)

A
  • ventral tegmental area of the midbrain
  • substantia nigra pars compacta
  • arcuate nucleus of the hypothalamus
48
Q

selective death of dopaminergic neurons describes what disease?

A

Parkinson’s disease (PD)

49
Q

dopamine functions in the brain: (name a few)

A
  • behavior and cognition
  • motivation and reward
  • sleep
  • mood
  • attention
  • learning
50
Q

Parkinson’s dz is assoc with deficiency in what? where?

A

deficiency in tyrosine hydroxylase in the substantia nigra

51
Q

how is PD treated? (3)

A
  • L-DOPA
  • deep brain stimulation
  • stem cell therapy
52
Q

what is the marker used for PD?

A

low levels of tyrosine hydroxylase in the substantial nigra (incapable of converting L-tyrosine to dopamine)

53
Q

excessive production of catecholamines leads to what type of tumor?

A

pheochromocytoma (tumors in adrenal medulla)

-very fast incr in BP

54
Q

Norepinephrine-serotonin reuptake inhibitors (SNRIs) are used as:

A

antidepressants

55
Q

norepinephrine (incr/decr) BP when released from sympathetic ganglia

A

increases BP

56
Q

appetite, mood, and sleep are controlled by what NT?

A

serotonin

57
Q

bananas, dates, and papayas affect serotonin levels with a good ratio of:

A

tryptophan to phenylalanineto leucine

58
Q

serotonin is derived from:

A

tryptophan

59
Q

what enzyme converts tryptophan into 5-hydroxytryptophan?

what cofactors are involved? (2)

A
  • tryptophan hydroxylase

- tetrahydrobiopterin and NADPH (cofactors)

60
Q

what enzyme converts 5-hydroxytryptophan in 5-hydroxytryptamine (serotonin)?
what cofactor is involved?

A
  • Dopa decarboxylase

- pyridoxal-P (cofactor)

61
Q

in all catecholamine degradation reactions, what happens overall? (3)

A
  • loss of ammonia
  • formation of aldehyde
  • formation of acid
62
Q

attention-deficit disorder is linked to abnormal levels of:

A

dopamine

63
Q

attention-deficit-hyperactivity disorder and clinical depression linked to low levels of:

A

serotonin

64
Q

more aggression and risky behavior linked to low levels of:

A

serotonin

65
Q
  • inhibitory NT
  • increases permeability of postsynaptic membranes to Cl- leading to inhibition of neurotransmission
  • inhibits over-excitation
  • contributes to motor control, vision, cortical fxns
  • aids in balanced brain fxn
A

gamma amino butyric acid (GABA)

66
Q

GABA receptor is the target of drugs used to treat:

A

insomnia

67
Q

in the short term, ethanol (incr/decr) GABA synthesis

A

increases

68
Q

in the long term, ethanol in heavy drinkers (incr/decr) GABA synthesis

A

decreases

69
Q

converting glutamate to GABA requires what enzyme?

A

glutamate decarboxylase

70
Q
  • neurodegenerative disorder
  • death in the 50s
  • gene IT15 on chr.4
  • gene pdt is huntingtin (has 37-121 glutamine repeats … normal = 11-34)
A

Huntington’s dz (HD)

71
Q

HD initially does what? where?

A

knocks out GABA neurons in the basal ganglia … results in excess motor signals -> random frequent motion

72
Q

brain atrophy occurs in what dz?

A

Huntington’s

25-30% of the brain shrinks

73
Q

where are the cell bodies of histaminergic neurons?

A

posterior basal hypothalamus

74
Q

histamine is (excitatory/inhibitory) NT in brain

A

histamine = excitatory NT in brain

75
Q

what enzyme converts histidine to histamine?

A

histidine decarboxylase

76
Q

what enzymes participate in the degradation of histamine in:
brain: (2)
peripheral tissues: (1)

A

brain: histidine methyl transferase and MAO-B

peripheral tissues: diamine oxidase

77
Q

anti-histamine effect on the brain causes:

A

drowsiness

78
Q

acetyl CoA and choline together form acetylcholine by way of what enzyme?

A

choline acetyltransferase

79
Q

what enzyme degrades acetylcholine by breaking its ester bond?

A

acetylcholinesterase

80
Q

NO synthase catalyzes the conversion of arginine to:

A

citrulline

-NO is a by-product

81
Q

three forms of NOS identified:

A
  1. endothelial (eNOS) - Ca2+ dependent
  2. neuronal (nNOS) - Ca2+ dependent
  3. inducible (iNOS) - in macrophages, neuts, and hepatocytes - Ca2+ INDEPENDENT
82
Q

Mr. X 70 y.o. male retired school teacher diagnosed with Parkinson’s. What cell types in the brain are specifically targeted by this disease?

A

dopaminergic neurons

83
Q

In response to a form of sleep disorder in which individuals tend to suffer from excessive sleep, a pharmaceutical company developed a drug that selectively alleviates this problem blocking the rate-limiting step in the biosynthesis of serotonin. what of the following enzymes catalyze the rate-limiting step?

A

tryptophan hydroxylase

84
Q

L-tyrosine is also synthesized in the liver from what AA?

what enzyme is used?

A
  • phenylalanine

- phenylalanine hydroxylase

85
Q

dopaminergic neurons present chiefly in the: (3)

A
  • ventral tegmental area of the midbrain
  • substantia nigra pars compacta
  • arcuate nucleus of the hypothalamus
86
Q

Parkinson’s dz is assoc with deficiency in what? where?

A

deficiency in tyrosine hydroxylase in the substantia nigra

87
Q

excessive production of catecholamines leads to what type of tumor?

A

pheochromocytoma (tumors in adrenal medulla)

-very fast incr in BP

88
Q

bananas, dates, and papayas affect serotonin levels with a good ratio of:

A

tryptophan to phenylalanineto leucine

89
Q

what enzyme converts 5-hydroxytryptophan in 5-hydroxytryptamine (serotonin)?
what cofactor is involved?

A
  • Dopa decarboxylase

- pyridoxal-P (cofactor)

90
Q

where are the cell bodies of histaminergic neurons?

A

posterior basal hypothalamus

91
Q

anti-histamine effect on the brain causes:

A

drowsiness

Neuro 1 Midterm (5 decks)

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