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Cell Structure and Function > Final Exam New Material > Flashcards

Final Exam New Material Flashcards

1
Q

triplet code

A

what we use to specify amino acids

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2
Q

degenerative code

A

an amino acid can be specified by more than one triplet

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3
Q

nonoverlapping code

A

reading frame is 3 nucleotides at a time

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4
Q

umabigous code

A

each codon only codes for one thing

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5
Q

start codon

A

AUG

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6
Q

stop codon

A

UAA, UAG, UGA

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7
Q

ribosome

A

polypeptide synthesis
- rRNA and protein
- large and small subunits
- mRNA binding site, A, P, and E

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8
Q

tRNA

A

align amino acids in correct order
- amino acids linked by ester bond
- named after aa it carries
- anticodon region that recognizes and pairs to complementary mRNA codon

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9
Q

aminoacyl-tRNA synthetase

A

attach amino acid to corresponding tRNA
- one for each amino acid
- catalyze attachment with ATP hydrolysis
- proofread final product

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10
Q

aminoacyl tRNA

A

tRNA and amino acid
- tRNA charged
- amino acid activated

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11
Q

mRNA

A

encode amino acid sequence
- tRNA binds complementary codon
- 5’ and 3’ untranslated regions

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12
Q

monocistronic

A

eukaryotes, encode one polypeptide

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13
Q

polycistronic

A

bacteria/archaea, encode multiple operons

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14
Q

protein factor

A

facilitate some translation steps

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15
Q

wobble hypothesis

A

3rd base codon is the wobble position (can change and not affect the codon)

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16
Q

Bacterial Translation Initiation (3 steps)

A
  1. initiation factors (IF1, IF2, IF3) bind to small ribosomal subunit
  2. Shine-delgarno sequence allows mRNA and tRNA to bind properly
  3. IF3 is released, small and large subunits form the 70S initiation complex
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17
Q

Eukaryotic Translation Initiation

A
  1. eLF2-GTP binds initiator tRNA Met, this binds to sm subunit with other eIFs
  2. mRNA binds to complex, 5’cap recognized and recruits eIF to regulate translation
  3. complexes join
  4. eLF2 hydrolyzes GTP and allows several eIF to leave
  5. translation starts, Kozak sequence: common start sequence
  6. large subunits join, GTP hydrolyzation and eIFs are released
    - poly(A)-binding protein
    - internal ribosome entry sequence
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18
Q

Elongation (3 steps)

A
  1. aminoacyl tRNA binds to ribosome, new amino acid is in position to be added to chain
    - as aminoacyl tRNA is transferred to ribosome, GTP is hydrolyzed then regenerated for the next cycle
  2. peptide bond formation linking it to chain
    - no energy needed
  3. mRNA is advanced 3 nucleotides via translocation
    - next codon is now in position for translocation
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19
Q

elongation factors

A

EF-Tu and EF-Ts, coupled with GTP hydrolysis

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20
Q

translocation

A

peptidyl tRNA moves from A to P site and empty tRNA moves to E site

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21
Q

polysibosome or polysome

A

mRNA being read by many ribosomes at the same time

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22
Q

stop codons are recognized by ______ _______ ______ not tRNA

A

protein release factors

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23
Q

release factors

A

end translation by releasing polypeptide from P site tRNA

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24
Q

missense

A

codes for wrong amino acid

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25
Q

non-stop

A

codes a (wild type) stop codon into an amino acid

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26
Q

nonsense

A

converts an amino acid codon into a stop codon

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27
Q

frameshift mutation

A

insertion/deletion of base pairs (not multiples of 3)

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28
Q

silent mutation

A

changes a base pair but not the amino acid it codes for

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29
Q

duplication

A

tandemly repeated a DNA sequence

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30
Q

translocation

A

DNA sequence is moves to a different place in the genome

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31
Q

inversion

A

DNA sequence is reversed

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32
Q

suppressor tRNA

A

nullifies effect of mutation

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33
Q

nonsense mediated decay

A

breakdown of mRNAs containing premature stop codons

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34
Q

nonstop decay

A

breakdown of defected RNA that has no stop codons, enzyme binds to A site

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35
Q

preinsulin

A

removal of N-terminus amino acids dubbed “pre” to produce proinsulin

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36
Q

proinsulin

A

removal of amino acids that intervene with disulfide bonds to produce insulin

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37
Q

cotranslational import

A

transfer of polypeptides to the ER, directly coupled to the translation process

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38
Q

postttranslational import

A

uptake of completed polypeptides by organelles, requires target sequence

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39
Q

proteins destined for endomembrane system

A
  • have and N terminal ER sequence that sends them to translocon channels while still being synthesized
  • go straight to ER lumen, others have stop sequences that anchor to membrane
  • may stay or transport to golgi, lysosomes, plasma membrane, or secretory vesicles
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40
Q

unfolded protein response (UPR) and ER-associated degradation…

A

help prevent the accumulation of unfolded proteins

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41
Q

proteins destined for nuclear interior, mitochondria, and chloroplasts, peroxisomes

A
  • synthesized on cytosolic ribosomes
  • send to target organelle after translation is complete
  • contain target sequences that promote uptake
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42
Q

proteins destine for mitochondria/chloroplasts

A

usually require more than one signal, can include an N-terminal transit sequence as well as hydrophobic sorting signal

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43
Q

neurons

A

send and receive electrical impulses

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44
Q

sensory neurons

A

a diverse group of cells specialized for the detection of various types of stimuli

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45
Q

motor neurons

A

transmit signals from the CNS to the muscles or glands they innervate

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46
Q

innervate

A

make synaptic connections

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47
Q

interneurons

A

process signals received from other neurons and relay the info to other parts of the nervous system

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48
Q

microglia

A

phagocytic cells that fight infections and remove debris

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49
Q

oligodendrocytes and Schwann cells

A

form insulating myelin sheath around neurons of the CNS and PNS repectively

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50
Q

astrocytes

A

control access of blood-borne components into the extracellular fluid surrounding nerve cells thereby forming the blood-brain barrier

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51
Q

processes

A

extensions off of neurons

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52
Q

two types of neuronal extensions

A
  • those that receive signals and combine them with other signals
  • those that conduct signals, sometimes over long distances
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53
Q

dendrites

A

neuron extensions that receive signals

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54
Q

axons

A

neuron extensions that conduct signals

55
Q

axoplasm

A

cytosol within an axon

56
Q

myelin sheath

A

vertebrate axons are surrounded by this, a discontinuous insulator of segments between nodes

57
Q

synaptic boutons

A

responsible for transmitting the signal to the next cell

58
Q

synapse

A

junction between two synaptic cells

59
Q

membrane potential

A

fundamental property of all cells, results from an excess of negative charge on one side of the membrane

60
Q

electrical excitability

A

certain types of stimuli trigger a rapid sequence of changes in the membrane potential

61
Q

during an action potential

A

membrane potential changes from negative to positive, and back again VERY quickly

62
Q

leak channels

A

channels that are not gated, they are always open

63
Q

On average, what does the Na/K pump transport?

A

three sodium out and two potassium into the cell for every one molecule of ATP

64
Q

steady state

A

an equilibrium is reached in which the forces of attraction due to the membrane potential balances out

65
Q

voltage-gated ion channels

A

respond to changes in the voltage across a membrane

66
Q

ligand-gated ion channels

A

open when a particular molecule binds to the channel

67
Q

channel gating

A

open or closed, gates do not appear to remain partially open

68
Q

channel inactivation

A

voltage-gated channels can adopt a second type of closed state, cannot reopen immediately even if stimulated to do so

69
Q

inactivating particle

A

inactivate voltage-gated channels

70
Q

action potential

A

a brief but large electrical depolarization and repolarization of the neuronal plasma membrane caused by the inward movement of Na and outward movement of K

71
Q

propagation

A

once an action potential is initiated in one region of the membrane, it will travel along the membrane away from the site of origin

72
Q

Hodgkin cycle

A

the relationship between depolarization, the opening of voltage-gated sodium channels, and an increase in sodium current

73
Q

subthreshold depolarizations

A

levels of depolarization that are too small to produce an action potential

74
Q

hyperpolarization or undershoot

A

the membrane potential briefly becomes even more negative than it normally is at rest, occurs because of the increased potassium permeability

75
Q

absolute refractory period

A

milliseconds after an action potential where it is impossible to trigger another, sodium channels are inactivated and cannot be opened

76
Q

relative refractory period

A

during undershoot, it is possible but difficult to trigger action potential

77
Q

passive spread of dedpolarization

A

a wave of depolarization spreads passively away from the site of origin, decreasing in magnitude as it goes

78
Q

axon hillock

A

base of the axon, region where action potentials are initiated most easily

79
Q

capacitance

A

ability of the neuronal membrane to retain electric charge

80
Q

nodes of Ranvier

A

interruptions in the myelin layer that ensure that the depolarization spreading out from an action potential at one node is still strong enough to bring an adjacent node above its threshold potential

81
Q

criteria for a neurotransmitter

A
  1. must elicit the appropriate response when introduced into the synaptic cleft
  2. must occur naturally in the presynaptic neuron
  3. must be released at the right time when the presynaptic neuron is stimulated
82
Q

acetylcholine

A

most common neurotransmitter for synapses between neurons outside the CNS

83
Q

cholinergic synapses

A

ones that use acetylcholine as their neurotransmitter

84
Q

catecholamines

A

dopamine, norepinephrine, epinephrine

85
Q

adrenergic synapses

A

synapses that use catecholamines as their neurotransmitters

86
Q

glutamatergic neurons

A

release glutamate as it’s neurotransmitter

87
Q

neuropeptides

A

short chains of amino acids that exhibit similar characteristics to neurotransmitters but have lasting effects (enkephalins)

88
Q

endocannabinoids

A

inhibit the activity of presynaptic neurons, THC

89
Q

release of calcium within the synaptic bouton has two main effects on neurosecretory vesicles

A
  1. vesicles held in storage are mobilized for rapid release
  2. vesicles that are ready for release rapidly dock and fuse with the plasma membrane in the synaptic bouton region
90
Q

t- and v-SNARE proteins

A

mediate docking and fusion of neurosecretory vesicles within the plasma membrane of the active zone

91
Q

synaptotagmin

A

binds calcium, involved in docking of vesicles

92
Q

active zone

A

specialized site for docking within the membrane of the presynaptic neuron

93
Q

compensatory endocytosis

A

relies on formation of clathrin-depedent vesicles which allows the recycling of membranes and maintains the size of the nerve terminal

94
Q

kiss-and-run exocytosis

A

a vesicle temporarily fuses with the plasma membrane via a tiny opening, causing the release of some neurotransmitter but then it rapidly reseals without the added step of complete fusion

95
Q

nicotinic acetylcholine receptor (nAchR)

A

when two molecules of acetylcholine bind, the channel opens

96
Q

antagonists

A

bind covalently to the acetylcholine receptor, blocking depolarization

97
Q

agonists

A

also bind to the acetylcholine receptor but mimic acetylcholine and cause depolarization (cannot be rapidly inactivated)

98
Q

GABA

A

a ligand-gated channel, conducts chloride ions, can cause hyperpolarization

99
Q

NMDA

A

ionotropic receptor for glutamate, when it binds the receptor is permeable to cations like Na+ and Ca2+

100
Q

neurotransmitters are removed from the synaptic cleft by two mechanisms

A
  1. degradation into inactive molecules
  2. reuptake
101
Q

acetycholinesterase

A

hydrolyses acetylcholine into acetic acid and choline, neither stimulates the acetylcholine receptor

102
Q

carbamoyl esters

A

toxins which inhibit acetylcholinesterase by covalently blocking the active site

103
Q

neurotransmitter reuptake

A

involves the pumping of neurotransmitters back into the presynaptic axon terminals or nearby support cells

104
Q

PSPs

A

post-synaptic potentials; incremental changes in potential due to the binding of neurotransmitter

105
Q

excitatory postsynaptic potential (EPSP)

A

if a neurotransmitter is excitatory, it will cause a small amount of depolarization called this

106
Q

inhibitory postsynaptic potential (IPSP)

A

if a neurotransmitter is inhibitory, it will hyperpolarize the postsynaptic neuron by a small amount

107
Q

how EPSPs can trigger action potentials

A
  1. temporal summation
  2. spatial summation
108
Q

temporal summation

A

if two action potentials fire in rapid succession at the presynaptic neuron, the post will be more depolarized

109
Q

spatial summation

A

when signals from many different neurons combine to form a large depolarization

110
Q

endocrine signals

A

hormones - produced a great distance from their target tissues and carried by the circulatory system

111
Q

paracrine signals

A

released locally, where they diffuse to act at short range on nearby tissues

112
Q

juxtacrine signals

A

when signals passed require physical contact between the sending and receiving cells

113
Q

autocrine signals

A

local mediators act on the same cell that produces them

114
Q

signal transduction

A

ability of a cell to translate a receptor-ligand interaction to changes in its behavior or gene expression

115
Q

a ligand binding to its receptor can alter the receptor in two ways

A
  1. can induce a change in receptor conformation
  2. can cause receptors to cluster together

or both

115
Q

a ligand binding to its receptor can alter the receptor in two ways

A
  1. can induce a change in receptor conformation
  2. can cause receptors to cluster together

or both

116
Q

when a ligand binds to a receptor, it is said to be ________

A

occupied

117
Q

agonists

A

drugs that activate the receptor to which they bind

118
Q

antagonists

A

inhibit the receptor by preventing the naturally occuring messenger from binding and activating the receptor

119
Q

cells can shut down signaling in many ways

A
  1. reducing the amount of free ligand
  2. reducing sensitivity of the receptor or amount of receptor the cell possesses
120
Q

receptor desensitization

A

when a ligand is present and receptors are occupied for prolonged periods of time, the cell adapts and no longer responds. to further stimulate the cell, the ligand concentration must increase.

121
Q

receptor-mediated endocytosis

A

removal of receptors from the cell surface

122
Q

coreceptors

A

help facilitate the interaction of the receptor with its ligand through their physical interaction with the receptor

123
Q

G protein-coupled receptors (GPCRs)

A

ligand binding causes a change in receptor conformation that activates a particular G protein

124
Q

G protein

A

guanine-nucleotide binding protein, olfactory receptors

125
Q

GPCR regulation

A

phosphorylation of specific amino acids (desensitized)

126
Q

G protein-coupled receptor kinases (GRKs)

A

act on activated receptors to phosphorylate GPCRs

127
Q

protein kinase A

A

activated by G protein mediated signaling can phosphorylate other amino acids on the receptor

128
Q

two distinct classes of G protein

A

large herterotrimeric
small monomeric

129
Q

large heterotrimeric G proteins contain three subunits

A

Galpha, Gbets, and G gamma

130
Q

heterotrimeric G proteins…….

A

mediate signal transduction through GPCRs

131
Q

G alpha

A

largest subunit, binds guanine nucleotide (GDP/GTP) and then detaches from G beta/gamma

132
Q

G beta and G gamma

A

permanently bound together, when GDP/GTP binds it associates with the receptor

133
Q

regulators of G protein signaling proteins (RGS)

A

improves efficiency of some G alpha proteins

Cell Structure and Function (6 decks)

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