EXAM 2 Flashcards
(108 cards)
1
Q
Useful model for studying membrane structure
A
Erythrocytes
2
Q
outer leaf of membrane
A
phosphatidylcholine + sphingomyelin.
3
Q
inner leaf
A
phosphatidylethanolamine + phosphatidylserine
4
Q
only in outer leaf
A
glycolipids
5
Q
present in same amounts as phospholipids
A
cholesterol
6
Q
Bilayers are _________, not solid.
A
viscous fluids
7
Q
Lipids and proteins are free to ________ within the membrane
A
diffuse laterally
8
Q
Cholesterol and sphingolipids (sphingomyelin and glycolipids) tend to cluster in:
A
small patches or lipid rafts.
9
Q
Most plasma membranes are about 50% _____ and 50% ______ by weight.
A
lipid; protein
10
Q
2 classes of membrane proteins
A
integral and peripheral
11
Q
type of bond associated with peripheral membrane proteins
A
ionic
12
Q
ionic bonds can be interrupted by:
A
polar reagents (salts or extreme pH)
13
Q
body part associated with peripheral membrane proteins
A
cytoskeleton
14
Q
integral membrane proteins can only be disrupted by
A
reagents that disrupt hydrophobic itneractions
15
Q
amphipathic molecules with hydrophobic and hydrophilic groups that can solubilize integral membrane proteins.
A
detergents
16
Q
integral proteins that span the lipid bilayer with portions exposed on both sides.
A
transmembrane proteins
17
Q
proteins are anchored in the plasma membrane by covalently attached lipids or glycolipids - anchor name?
A
GPI anchor
18
Q
carbohydrate coat
A
glyoalyx
19
Q
Apical surface in small intenstine
A
covered in microvilli to increase surface area
20
Q
basolateral surface in the small intestine
A
mediate transfer of absorbed nutrients to the blood
21
Q
separate the apical and basolateral domains.
A
tight junctions
22
Q
transient structures in which specific proteins can be concentrated to facilitate interactions.
A
lipid rafts
23
Q
small lipid rafts that start as invaginations of the plasma membrane, organized by caveolin.
A
Caveolae
24
Q
_______ mediate passage of small molecules, allowing the cell to control the composition of its cytoplasm.
A
Transport molecules
25
bind molecules on one side of the membrane, then undergo conformational changes that allow the molecule to pass through and be released on the other side.
carrier proteins
26
form open pores through the membrane, allowing free diffusion of any molecule of the appropriate size and charge.
Channel proteins
27
Glucose transporters function by alternating between:
two conformational states.
28
Allow water molecules to cross the membrane more rapidly than they can diffuse through the phospholipid bilayers.
Aquaporins
29
open in response to binding of neurotransmitters or other signaling molecules.
Ligand-gated channels
30
open in response to changes in electric potential across the plasma membrane.
Voltage-gated channels
31
use energy from ATP hydrolysis to actively transport ions across the plasma membrane to maintain concentration gradients.
ion pumps
32
inside of the cell is ______ with respect to the outside.
negative
33
nerve impulses
action potentials
34
____ is pumped out of the cell while ____ is pumped in.
Na+; K+
35
_______ of adjacent regions of the plasma membrane allows action potentials to travel the length of a nerve cell.
Depolarization
36
At the nerve end, neurotransmitters are released into the synapse, where they bind to receptors on another nerve cell to open ______-gated ion channels.
ligand
37
Na+ channel pore is too _____ for K+ or larger ions.
narrow
38
Ion channels play critical roles in ______ in all cell types.
signaling
39
transport against concentration gradient
active transport
40
Example of active transport
Ion pumps
41
The Na+-K+ pump (or Na+-K+ ATPase) uses energy from _________ to transport Na+ and K+ against their electrochemical gradients.
ATP hydrolysis
42
The differences in ion concentrations balance the high concentrations of organic molecules inside cells, equalizing osmotic pressure and preventing _______________
the net influx of water.
43
Ion pumps in bacteria, yeasts, and plant cells actively transport _____ out of the cell.
H+
44
H+ is actively pumped out of stomach lining cells, resulting in ______________
the acidity of gastric fluids.
45
Structurally distinct pumps actively transport H+ into _______________
lysosomes and endosomes.
46
two ATP-binding domains and two transmembrane domains.
ABC transporters
47
Uptake of ________________ is an example of transport of two molecules in the same direction.
glucose and Na+
48
the taking in of matter by a living cell by invagination of its membrane to form a vacuole.
endocytosis
49
Endocytosis examples (name 3)
macromolecules,
Fluids,
large particles such as bacteria.
50
Binding of a particle to receptors on the cell surface triggers extension of pseudopodia, which surround the particle and fuse to form a large vesicle
phagocytosis
51
phagolysosomes
phagosomes and lysosomes fused together
52
types of phagocytes in mammals
white blood cells
53
uptake of extracellular fluids in large vesicles.
Macropinocytosis
54
________ endocytosis is a mechanism for selective uptake of specific macromolecules.
Clathrin-mediated
55
Macromolecules bind to cell surface receptors in specialized regions called:
clathrin-coated pits.
56
Uptake of _____ requires binding to specific receptors in clathrin-coated pits.
LDL
57
After internalization, clathrin-coated vesicles shed their coats and fuse with:
early endosomes.
58
align amino acids from template
tRNA
59
sites of protein synthesis
rRNA
60
viruses containing RNA instead of DNA
retroviruses
61
cleave DNA at specific sequences.
Restriction endonucleases
62
the DNA sequence that signals the host DNA polymerase to start replication.
origin of replication
63
methods of studying gene function (name 3)
-transfection
-direct microinjection into nucleus
-incorporation of DNA into liposomes
64
coding sequences
exons
65
noncoding sequences
introns
66
introns are removed by:
splicing
67
histone genes lack:
introns
68
Introns also allow exons of a gene to be joined in different combinations, resulting in different proteins from the same gene
alternative splicing
69
Five major histone types:
H1, H2A, H2B, H3, H4
70
basic structural unit of chromatin
nucleosome
71
H1 is bound to DNA where it enters the core particle
chromatosome
72
DNA is wrapped around a histone core to form:
nucleosome core particles
73
The nucleosome core particles contain _____ base pairs
147
74
highly condensed chromatin
heterochromatin
75
DNA sequences to which proteins bind, forming a kinetochore.
centromeres
76
determine the lifespan and reproductive capacity of cells.
telomeres
77
direction of RNA polymerase
5 to 3
78
6 nucleotide long gene sequence to which RNA polymerase binds to initiate transcription
promoter
79
During elongation in prokaryote transcription, polymerase maintains an unwound region of about:
15 base pairs
80
RNA synthesis continues until the polymerase encounters a:
stop signal.
81
Transcription of the GC-rich inverted repeat results in a segment of RNA that can form a stable _______ structure.
stem-loop
82
Transcription takes place on:
Chromatin
83
proteins involved in transcription from polymerase II promoters.
General transcription factors
84
resembles the –10 sequence of bacterial promoters
TATA box
85
Transcribes rRNA genes.
RNA polymerase I
86
In eukaryotes, pre-mRNAs are extensively modified ___________ (when?)
before export from the nucleus.
87
The 5′ end of the transcript is modified by addition of a _______
7-methylguanosine cap.
88
At the 3′ end, a ________ is added by polyadenylation.
poly-A tail
89
2 steps of splicing
cleavage at the 5 splice site
cleavage at the 3 splice site
90
Short-lived mRNAs code for:
regulatory proteins
91
long half-lives mRNAs encode:
structural proteins
92
Degradation of mRNAs initiated by:
shortening of poly-A tail
93
Genes encoding these enzymes are expressed as a single unit
operon
94
two loci control transcription
o and i
95
i (not in the operon), encodes a protein that binds to the operator.
i
96
affect expression of linked genes on the same DNA molecule (e.g., the operator).
Cis-acting control elements
97
The lac operon is an example of ______ control
negative
98
Activity of enhancers does not depend on ______ from the transcription initiation site.
distance
99
allows a transcription factor bound to a distant enhancer to interact with proteins associated with the RNA polymerase/Mediator complex at the promoter.
DNA looping
100
2 types of domains
1. DNA binding domain
2. Interactions with other proteins
101
Chromatin can be altered by: (2 things)
histone modification
nucleosome rearrangements
102
____________ neutralizes the positive charge of lysine, relaxing chromatin structure and increasing availability of the DNA template for transcription.
Acetylation
103
Promoters and enhancers are free of:
nucleosomes
104
protein complexes that alter contacts between DNA and histones.
Chromatin remodeling factors
105
Following initiation of transcription, elongation is facilitated by:
elongation factors
106
transmission of information that is not in the DNA sequence.
epigenetic inheritance
107
DNA methylation correlates with:
transcriptional repression
108
the expression of some genes depends on whether they come from the mother or the father.
genomic imprinting
