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NS - Biochemistry
The brain represents approximately what percentage of body weight?
5%
10%
2%
20%
The brain consumes approximately what percentage of total body glucose?
5–10%
10–15%
15–18%
20–25%
Neurons rely mainly on which factor for continuous energy supply?
Fatty acids
Glycogen
Continuous glucose and oxygen
Ketone bodies only
Interruption of neuronal energy supply leads to:
Slow degeneration
No effect
Rapid dysfunction
Increased ATP
Which process is ATP-intensive in neurons?
Protein synthesis
Na⁺/K⁺ ATPase activity
DNA replication
Fatty acid oxidation
Astrocytes store energy mainly in the form of:
Triglycerides
Ketone bodies
Glycogen
Lactate
Astrocytes supply neurons with which metabolite during high activity?
Glucose
Pyruvate
Lactate
Alanine
Which neurotransmitters are cleared from synapses by astrocytes?
Dopamine and serotonin
Glutamate and GABA
Acetylcholine and histamine
Norepinephrine and epinephrine
Glucose crosses the blood–brain barrier via:
GLUT3
GLUT4
GLUT1
SGLT
Neuronal glucose uptake occurs mainly via:
GLUT1
GLUT2
GLUT3
GLUT4
Brain glucose transport is:
Insulin-dependent
Insulin-independent
Hormone-dependent
Calcium-dependent
During fasting, the brain can use which alternative fuel?
Fatty acids
Amino acids
Ketone bodies
Lactate only
The majority of neurotransmitters belong to which group?
Neuropeptides
Steroids
Small nitrogen-containing molecules
Gases
Which neurotransmitter is NOT stored in vesicles?
Dopamine
GABA
Nitric oxide
Acetylcholine
Neuropeptides are synthesized initially as:
Active peptides
Pro-peptides
Prepropeptides
Amino acids
Neuropeptides are stored in which vesicles?
Synaptic vesicles
Small clear vesicles
Large dense-core vesicles
Endosomes
Neuropeptide release usually requires:
Low-frequency stimulation
No calcium
High-frequency stimulation
Sodium influx
Neuropeptide receptors are mainly:
Ion channels
G-protein coupled receptors
Enzyme-linked receptors
Nuclear receptors
Neuropeptides are mainly cleared by:
Reuptake transporters
Diffusion only
Extracellular peptidases
Renal excretion
Substance P is mainly involved in:
Appetite regulation
Pain transmission
Sleep regulation
Memory
Glutamate is the major:
Inhibitory neurotransmitter
Excitatory neurotransmitter
Monoamine
Neuropeptide
Which enzyme converts glutamine to glutamate?
Glutamate dehydrogenase
Glutaminase
Transaminase
Decarboxylase
Which vitamin is required for transamination in glutamate synthesis?
Vitamin B1
Vitamin B2
Vitamin B6 (PLP)
Vitamin B12
GABA is the major ______ neurotransmitter of the CNS.
Excitatory
Modulatory
Inhibitory
Peptidergic
GABA is synthesized from glutamate by:
Deamination
Transamination
Decarboxylation
Oxidation
The enzyme for GABA synthesis requires which cofactor?
BH4
NAD⁺
PLP (Vitamin B6)
FAD
In the GABA shunt, GABA is first converted into:
Succinate
α-ketoglutarate
Succinate semialdehyde
Glutamine
Catecholamines are synthesized from:
Tryptophan
Tyrosine
Histidine
Glutamate
Phenylalanine is converted to tyrosine by:
Transamination
Decarboxylation
Hydroxylation
Methylation
The coenzyme required for phenylalanine hydroxylase is:
PLP
FAD
BH4
NADPH
Dopamine is formed from DOPA by:
Hydroxylation
Methylation
Decarboxylation
Oxidation
Norepinephrine is formed from dopamine by:
COMT
MAO
Dopamine β-hydroxylase
Tyrosine hydroxylase
Epinephrine synthesis requires which methyl donor?
NADPH
SAM
BH4
FAD
Catecholamines are transported into vesicles by:
DAT
NET
VMAT2
GLUT3
The terminal metabolite of norepinephrine is:
HVA
VMA
5-HIAA
Citrulline
Serotonin is synthesized from:
Tyrosine
Histidine
Tryptophan
Phenylalanine
The rate-limiting enzyme in serotonin synthesis is:
DOPA decarboxylase
Tryptophan hydroxylase
MAO
COMT
The final metabolite of serotonin degradation is:
HVA
VMA
5-HIAA
Melatonin
Histamine is synthesized from:
Tyrosine
Histidine
Tryptophan
Glutamate
Histidine decarboxylase requires which cofactor?
BH4
PLP
FAD
NAD⁺
In the brain, histamine acts mainly as a:
Hormone
Neurotransmitter
Enzyme
Coenzyme
Acetylcholine is synthesized from choline and:
Pyruvate
Acetate
Acetyl-CoA
Citrate
Acetylcholine is degraded by:
MAO
COMT
Acetylcholinesterase
Choline acetyltransferase
Sarin gas causes paralysis by inhibiting:
MAO
COMT
Acetylcholinesterase
VMAT
Aspartate is synthesized from which TCA intermediate?
Succinate
Citrate
Oxaloacetate
α-Ketoglutarate
Aspartate is classified as a(n):
Inhibitory neurotransmitter
Excitatory neurotransmitter
Neuropeptide
Monoamine
Glycine is an inhibitory neurotransmitter synthesized from:
Alanine
Serine
Glutamate
Aspartate
Nitric oxide is synthesized from:
Glutamate
Arginine
Tyrosine
Tryptophan
Nitric oxide activates which enzyme in smooth muscle?
Adenylate cyclase
Phosphodiesterase
Guanylate cyclase
Acetylcholinesterase
Nitric oxide signaling from postsynaptic to presynaptic neuron is called:
Anterograde signaling
Endocrine signaling
Retrograde signaling
Autocrine signaling