Final Exam New Material Flashcards
1
Q
triplet code
A
what we use to specify amino acids
2
Q
degenerative code
A
an amino acid can be specified by more than one triplet
3
Q
nonoverlapping code
A
reading frame is 3 nucleotides at a time
4
Q
umabigous code
A
each codon only codes for one thing
5
Q
start codon
A
AUG
6
Q
stop codon
A
UAA, UAG, UGA
7
Q
ribosome
A
polypeptide synthesis
- rRNA and protein
- large and small subunits
- mRNA binding site, A, P, and E
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
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
10
Q
aminoacyl tRNA
A
tRNA and amino acid
- tRNA charged
- amino acid activated
11
Q
mRNA
A
encode amino acid sequence
- tRNA binds complementary codon
- 5’ and 3’ untranslated regions
12
Q
monocistronic
A
eukaryotes, encode one polypeptide
13
Q
polycistronic
A
bacteria/archaea, encode multiple operons
14
Q
protein factor
A
facilitate some translation steps
15
Q
wobble hypothesis
A
3rd base codon is the wobble position (can change and not affect the codon)
16
Q
Bacterial Translation Initiation (3 steps)
A
- initiation factors (IF1, IF2, IF3) bind to small ribosomal subunit
- Shine-delgarno sequence allows mRNA and tRNA to bind properly
- IF3 is released, small and large subunits form the 70S initiation complex
17
Q
Eukaryotic Translation Initiation
A
- eLF2-GTP binds initiator tRNA Met, this binds to sm subunit with other eIFs
- mRNA binds to complex, 5’cap recognized and recruits eIF to regulate translation
- complexes join
- eLF2 hydrolyzes GTP and allows several eIF to leave
- translation starts, Kozak sequence: common start sequence
- large subunits join, GTP hydrolyzation and eIFs are released
- poly(A)-binding protein
- internal ribosome entry sequence
18
Q
Elongation (3 steps)
A
- 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 - peptide bond formation linking it to chain
- no energy needed - mRNA is advanced 3 nucleotides via translocation
- next codon is now in position for translocation
19
Q
elongation factors
A
EF-Tu and EF-Ts, coupled with GTP hydrolysis
20
Q
translocation
A
peptidyl tRNA moves from A to P site and empty tRNA moves to E site
21
Q
polysibosome or polysome
A
mRNA being read by many ribosomes at the same time
22
Q
stop codons are recognized by ______ _______ ______ not tRNA
A
protein release factors
23
Q
release factors
A
end translation by releasing polypeptide from P site tRNA
24
Q
missense
A
codes for wrong amino acid
25
non-stop
codes a (wild type) stop codon into an amino acid
26
nonsense
converts an amino acid codon into a stop codon
27
frameshift mutation
insertion/deletion of base pairs (not multiples of 3)
28
silent mutation
changes a base pair but not the amino acid it codes for
29
duplication
tandemly repeated a DNA sequence
30
translocation
DNA sequence is moves to a different place in the genome
31
inversion
DNA sequence is reversed
32
suppressor tRNA
nullifies effect of mutation
33
nonsense mediated decay
breakdown of mRNAs containing premature stop codons
34
nonstop decay
breakdown of defected RNA that has no stop codons, enzyme binds to A site
35
preinsulin
removal of N-terminus amino acids dubbed "pre" to produce proinsulin
36
proinsulin
removal of amino acids that intervene with disulfide bonds to produce insulin
37
cotranslational import
transfer of polypeptides to the ER, directly coupled to the translation process
38
postttranslational import
uptake of completed polypeptides by organelles, requires target sequence
39
proteins destined for endomembrane system
- 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
40
unfolded protein response (UPR) and ER-associated degradation...
help prevent the accumulation of unfolded proteins
41
proteins destined for nuclear interior, mitochondria, and chloroplasts, peroxisomes
- synthesized on cytosolic ribosomes
- send to target organelle after translation is complete
- contain target sequences that promote uptake
42
proteins destine for mitochondria/chloroplasts
usually require more than one signal, can include an N-terminal transit sequence as well as hydrophobic sorting signal
43
neurons
send and receive electrical impulses
44
sensory neurons
a diverse group of cells specialized for the detection of various types of stimuli
45
motor neurons
transmit signals from the CNS to the muscles or glands they innervate
46
innervate
make synaptic connections
47
interneurons
process signals received from other neurons and relay the info to other parts of the nervous system
48
microglia
phagocytic cells that fight infections and remove debris
49
oligodendrocytes and Schwann cells
form insulating myelin sheath around neurons of the CNS and PNS repectively
50
astrocytes
control access of blood-borne components into the extracellular fluid surrounding nerve cells thereby forming the blood-brain barrier
51
processes
extensions off of neurons
52
two types of neuronal extensions
- those that receive signals and combine them with other signals
- those that conduct signals, sometimes over long distances
53
dendrites
neuron extensions that receive signals
54
axons
neuron extensions that conduct signals
55
axoplasm
cytosol within an axon
56
myelin sheath
vertebrate axons are surrounded by this, a discontinuous insulator of segments between nodes
57
synaptic boutons
responsible for transmitting the signal to the next cell
58
synapse
junction between two synaptic cells
59
membrane potential
fundamental property of all cells, results from an excess of negative charge on one side of the membrane
60
electrical excitability
certain types of stimuli trigger a rapid sequence of changes in the membrane potential
61
during an action potential
membrane potential changes from negative to positive, and back again VERY quickly
62
leak channels
channels that are not gated, they are always open
63
On average, what does the Na/K pump transport?
three sodium out and two potassium into the cell for every one molecule of ATP
64
steady state
an equilibrium is reached in which the forces of attraction due to the membrane potential balances out
65
voltage-gated ion channels
respond to changes in the voltage across a membrane
66
ligand-gated ion channels
open when a particular molecule binds to the channel
67
channel gating
open or closed, gates do not appear to remain partially open
68
channel inactivation
voltage-gated channels can adopt a second type of closed state, cannot reopen immediately even if stimulated to do so
69
inactivating particle
inactivate voltage-gated channels
70
action potential
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
propagation
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
Hodgkin cycle
the relationship between depolarization, the opening of voltage-gated sodium channels, and an increase in sodium current
73
subthreshold depolarizations
levels of depolarization that are too small to produce an action potential
74
hyperpolarization or undershoot
the membrane potential briefly becomes even more negative than it normally is at rest, occurs because of the increased potassium permeability
75
absolute refractory period
milliseconds after an action potential where it is impossible to trigger another, sodium channels are inactivated and cannot be opened
76
relative refractory period
during undershoot, it is possible but difficult to trigger action potential
77
passive spread of dedpolarization
a wave of depolarization spreads passively away from the site of origin, decreasing in magnitude as it goes
78
axon hillock
base of the axon, region where action potentials are initiated most easily
79
capacitance
ability of the neuronal membrane to retain electric charge
80
nodes of Ranvier
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
criteria for a neurotransmitter
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
acetylcholine
most common neurotransmitter for synapses between neurons outside the CNS
83
cholinergic synapses
ones that use acetylcholine as their neurotransmitter
84
catecholamines
dopamine, norepinephrine, epinephrine
85
adrenergic synapses
synapses that use catecholamines as their neurotransmitters
86
glutamatergic neurons
release glutamate as it's neurotransmitter
87
neuropeptides
short chains of amino acids that exhibit similar characteristics to neurotransmitters but have lasting effects (enkephalins)
88
endocannabinoids
inhibit the activity of presynaptic neurons, THC
89
release of calcium within the synaptic bouton has two main effects on neurosecretory vesicles
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
t- and v-SNARE proteins
mediate docking and fusion of neurosecretory vesicles within the plasma membrane of the active zone
91
synaptotagmin
binds calcium, involved in docking of vesicles
92
active zone
specialized site for docking within the membrane of the presynaptic neuron
93
compensatory endocytosis
relies on formation of clathrin-depedent vesicles which allows the recycling of membranes and maintains the size of the nerve terminal
94
kiss-and-run exocytosis
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
nicotinic acetylcholine receptor (nAchR)
when two molecules of acetylcholine bind, the channel opens
96
antagonists
bind covalently to the acetylcholine receptor, blocking depolarization
97
agonists
also bind to the acetylcholine receptor but mimic acetylcholine and cause depolarization (cannot be rapidly inactivated)
98
GABA
a ligand-gated channel, conducts chloride ions, can cause hyperpolarization
99
NMDA
ionotropic receptor for glutamate, when it binds the receptor is permeable to cations like Na+ and Ca2+
100
neurotransmitters are removed from the synaptic cleft by two mechanisms
1. degradation into inactive molecules
2. reuptake
101
acetycholinesterase
hydrolyses acetylcholine into acetic acid and choline, neither stimulates the acetylcholine receptor
102
carbamoyl esters
toxins which inhibit acetylcholinesterase by covalently blocking the active site
103
neurotransmitter reuptake
involves the pumping of neurotransmitters back into the presynaptic axon terminals or nearby support cells
104
PSPs
post-synaptic potentials; incremental changes in potential due to the binding of neurotransmitter
105
excitatory postsynaptic potential (EPSP)
if a neurotransmitter is excitatory, it will cause a small amount of depolarization called this
106
inhibitory postsynaptic potential (IPSP)
if a neurotransmitter is inhibitory, it will hyperpolarize the postsynaptic neuron by a small amount
107
how EPSPs can trigger action potentials
1. temporal summation
2. spatial summation
108
temporal summation
if two action potentials fire in rapid succession at the presynaptic neuron, the post will be more depolarized
109
spatial summation
when signals from many different neurons combine to form a large depolarization
110
endocrine signals
hormones - produced a great distance from their target tissues and carried by the circulatory system
111
paracrine signals
released locally, where they diffuse to act at short range on nearby tissues
112
juxtacrine signals
when signals passed require physical contact between the sending and receiving cells
113
autocrine signals
local mediators act on the same cell that produces them
114
signal transduction
ability of a cell to translate a receptor-ligand interaction to changes in its behavior or gene expression
115
a ligand binding to its receptor can alter the receptor in two ways
1. can induce a change in receptor conformation
2. can cause receptors to cluster together
or both
115
a ligand binding to its receptor can alter the receptor in two ways
1. can induce a change in receptor conformation
2. can cause receptors to cluster together
or both
116
when a ligand binds to a receptor, it is said to be ________
occupied
117
agonists
drugs that activate the receptor to which they bind
118
antagonists
inhibit the receptor by preventing the naturally occuring messenger from binding and activating the receptor
119
cells can shut down signaling in many ways
1. reducing the amount of free ligand
2. reducing sensitivity of the receptor or amount of receptor the cell possesses
120
receptor desensitization
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
receptor-mediated endocytosis
removal of receptors from the cell surface
122
coreceptors
help facilitate the interaction of the receptor with its ligand through their physical interaction with the receptor
123
G protein-coupled receptors (GPCRs)
ligand binding causes a change in receptor conformation that activates a particular G protein
124
G protein
guanine-nucleotide binding protein, olfactory receptors
125
GPCR regulation
phosphorylation of specific amino acids (desensitized)
126
G protein-coupled receptor kinases (GRKs)
act on activated receptors to phosphorylate GPCRs
127
protein kinase A
activated by G protein mediated signaling can phosphorylate other amino acids on the receptor
128
two distinct classes of G protein
large herterotrimeric
small monomeric
129
large heterotrimeric G proteins contain three subunits
Galpha, Gbets, and G gamma
130
heterotrimeric G proteins.......
mediate signal transduction through GPCRs
131
G alpha
largest subunit, binds guanine nucleotide (GDP/GTP) and then detaches from G beta/gamma
132
G beta and G gamma
permanently bound together, when GDP/GTP binds it associates with the receptor
133
regulators of G protein signaling proteins (RGS)
improves efficiency of some G alpha proteins
