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Molecular Cell Bio > EXAM 2 > Flashcards

EXAM 2 Flashcards

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Biology 101 flashcards
1
Q

Useful model for studying membrane structure

A

Erythrocytes

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2
Q

outer leaf of membrane

A

phosphatidylcholine + sphingomyelin.

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3
Q

inner leaf

A

phosphatidylethanolamine + phosphatidylserine

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4
Q

only in outer leaf

A

glycolipids

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5
Q

present in same amounts as phospholipids

A

cholesterol

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6
Q

Bilayers are _________, not solid.

A

viscous fluids

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7
Q

Lipids and proteins are free to ________ within the membrane

A

diffuse laterally

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8
Q

Cholesterol and sphingolipids (sphingomyelin and glycolipids) tend to cluster in:

A

small patches or lipid rafts.

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9
Q

Most plasma membranes are about 50% _____ and 50% ______ by weight.

A

lipid; protein

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10
Q

2 classes of membrane proteins

A

integral and peripheral

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11
Q

type of bond associated with peripheral membrane proteins

A

ionic

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12
Q

ionic bonds can be interrupted by:

A

polar reagents (salts or extreme pH)

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13
Q

body part associated with peripheral membrane proteins

A

cytoskeleton

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14
Q

integral membrane proteins can only be disrupted by

A

reagents that disrupt hydrophobic itneractions

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15
Q

amphipathic molecules with hydrophobic and hydrophilic groups that can solubilize integral membrane proteins.

A

detergents

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16
Q

integral proteins that span the lipid bilayer with portions exposed on both sides.

A

transmembrane proteins

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17
Q

proteins are anchored in the plasma membrane by covalently attached lipids or glycolipids - anchor name?

A

GPI anchor

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18
Q

carbohydrate coat

A

glyoalyx

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19
Q

Apical surface in small intenstine

A

covered in microvilli to increase surface area

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20
Q

basolateral surface in the small intestine

A

mediate transfer of absorbed nutrients to the blood

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21
Q

separate the apical and basolateral domains.

A

tight junctions

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22
Q

transient structures in which specific proteins can be concentrated to facilitate interactions.

A

lipid rafts

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23
Q

small lipid rafts that start as invaginations of the plasma membrane, organized by caveolin.

A

Caveolae

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24
Q

_______ mediate passage of small molecules, allowing the cell to control the composition of its cytoplasm.

A

Transport molecules

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25
Q

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.

A

carrier proteins

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26
Q

form open pores through the membrane, allowing free diffusion of any molecule of the appropriate size and charge.

A

Channel proteins

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27
Q

Glucose transporters function by alternating between:

A

two conformational states.

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28
Q

Allow water molecules to cross the membrane more rapidly than they can diffuse through the phospholipid bilayers.

A

Aquaporins

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29
Q

open in response to binding of neurotransmitters or other signaling molecules.

A

Ligand-gated channels

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30
Q

open in response to changes in electric potential across the plasma membrane.

A

Voltage-gated channels

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31
Q

use energy from ATP hydrolysis to actively transport ions across the plasma membrane to maintain concentration gradients.

A

ion pumps

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32
Q

inside of the cell is ______ with respect to the outside.

A

negative

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33
Q

nerve impulses

A

action potentials

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34
Q

____ is pumped out of the cell while ____ is pumped in.

A

Na+; K+

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35
Q

_______ of adjacent regions of the plasma membrane allows action potentials to travel the length of a nerve cell.

A

Depolarization

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36
Q

At the nerve end, neurotransmitters are released into the synapse, where they bind to receptors on another nerve cell to open ______-gated ion channels.

A

ligand

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37
Q

Na+ channel pore is too _____ for K+ or larger ions.

A

narrow

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38
Q

Ion channels play critical roles in ______ in all cell types.

A

signaling

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39
Q

transport against concentration gradient

A

active transport

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40
Q

Example of active transport

A

Ion pumps

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41
Q

The Na+-K+ pump (or Na+-K+ ATPase) uses energy from _________ to transport Na+ and K+ against their electrochemical gradients.

A

ATP hydrolysis

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42
Q

The differences in ion concentrations balance the high concentrations of organic molecules inside cells, equalizing osmotic pressure and preventing _______________

A

the net influx of water.

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43
Q

Ion pumps in bacteria, yeasts, and plant cells actively transport _____ out of the cell.

A

H+

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44
Q

H+ is actively pumped out of stomach lining cells, resulting in ______________

A

the acidity of gastric fluids.

45
Q

Structurally distinct pumps actively transport H+ into _______________

A

lysosomes and endosomes.

46
Q

two ATP-binding domains and two transmembrane domains.

A

ABC transporters

47
Q

Uptake of ________________ is an example of transport of two molecules in the same direction.

A

glucose and Na+

48
Q

the taking in of matter by a living cell by invagination of its membrane to form a vacuole.

A

endocytosis

49
Q

Endocytosis examples (name 3)

A

macromolecules,
Fluids,
large particles such as bacteria.

50
Q

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

A

phagocytosis

51
Q

phagolysosomes

A

phagosomes and lysosomes fused together

52
Q

types of phagocytes in mammals

A

white blood cells

53
Q

uptake of extracellular fluids in large vesicles.

A

Macropinocytosis

54
Q

________ endocytosis is a mechanism for selective uptake of specific macromolecules.

A

Clathrin-mediated

55
Q

Macromolecules bind to cell surface receptors in specialized regions called:

A

clathrin-coated pits.

56
Q

Uptake of _____ requires binding to specific receptors in clathrin-coated pits.

A

LDL

57
Q

After internalization, clathrin-coated vesicles shed their coats and fuse with:

A

early endosomes.

58
Q

align amino acids from template

A

tRNA

59
Q

sites of protein synthesis

A

rRNA

60
Q

viruses containing RNA instead of DNA

A

retroviruses

61
Q

cleave DNA at specific sequences.

A

Restriction endonucleases

62
Q

the DNA sequence that signals the host DNA polymerase to start replication.

A

origin of replication

63
Q

methods of studying gene function (name 3)

A

-transfection
-direct microinjection into nucleus
-incorporation of DNA into liposomes

64
Q

coding sequences

A

exons

65
Q

noncoding sequences

A

introns

66
Q

introns are removed by:

A

splicing

67
Q

histone genes lack:

A

introns

68
Q

Introns also allow exons of a gene to be joined in different combinations, resulting in different proteins from the same gene

A

alternative splicing

69
Q

Five major histone types:

A

H1, H2A, H2B, H3, H4

70
Q

basic structural unit of chromatin

A

nucleosome

71
Q

H1 is bound to DNA where it enters the core particle

A

chromatosome

72
Q

DNA is wrapped around a histone core to form:

A

nucleosome core particles

73
Q

The nucleosome core particles contain _____ base pairs

A

147

74
Q

highly condensed chromatin

A

heterochromatin

75
Q

DNA sequences to which proteins bind, forming a kinetochore.

A

centromeres

76
Q

determine the lifespan and reproductive capacity of cells.

A

telomeres

77
Q

direction of RNA polymerase

A

5 to 3

78
Q

6 nucleotide long gene sequence to which RNA polymerase binds to initiate transcription

A

promoter

79
Q

During elongation in prokaryote transcription, polymerase maintains an unwound region of about:

A

15 base pairs

80
Q

RNA synthesis continues until the polymerase encounters a:

A

stop signal.

81
Q

Transcription of the GC-rich inverted repeat results in a segment of RNA that can form a stable _______ structure.

A

stem-loop

82
Q

Transcription takes place on:

A

Chromatin

83
Q

proteins involved in transcription from polymerase II promoters.

A

General transcription factors

84
Q

resembles the –10 sequence of bacterial promoters

A

TATA box

85
Q

Transcribes rRNA genes.

A

RNA polymerase I

86
Q

In eukaryotes, pre-mRNAs are extensively modified ___________ (when?)

A

before export from the nucleus.

87
Q

The 5′ end of the transcript is modified by addition of a _______

A

7-methylguanosine cap.

88
Q

At the 3′ end, a ________ is added by polyadenylation.

A

poly-A tail

89
Q

2 steps of splicing

A

cleavage at the 5 splice site
cleavage at the 3 splice site

90
Q

Short-lived mRNAs code for:

A

regulatory proteins

91
Q

long half-lives mRNAs encode:

A

structural proteins

92
Q

Degradation of mRNAs initiated by:

A

shortening of poly-A tail

93
Q

Genes encoding these enzymes are expressed as a single unit

A

operon

94
Q

two loci control transcription

A

o and i

95
Q

i (not in the operon), encodes a protein that binds to the operator.

A

i

96
Q

affect expression of linked genes on the same DNA molecule (e.g., the operator).

A

Cis-acting control elements

97
Q

The lac operon is an example of ______ control

A

negative

98
Q

Activity of enhancers does not depend on ______ from the transcription initiation site.

A

distance

99
Q

allows a transcription factor bound to a distant enhancer to interact with proteins associated with the RNA polymerase/Mediator complex at the promoter.

A

DNA looping

100
Q

2 types of domains

A
  1. DNA binding domain
  2. Interactions with other proteins
101
Q

Chromatin can be altered by: (2 things)

A

histone modification
nucleosome rearrangements

102
Q

____________ neutralizes the positive charge of lysine, relaxing chromatin structure and increasing availability of the DNA template for transcription.

A

Acetylation

103
Q

Promoters and enhancers are free of:

A

nucleosomes

104
Q

protein complexes that alter contacts between DNA and histones.

A

Chromatin remodeling factors

105
Q

Following initiation of transcription, elongation is facilitated by:

A

elongation factors

106
Q

transmission of information that is not in the DNA sequence.

A

epigenetic inheritance

107
Q

DNA methylation correlates with:

A

transcriptional repression

108
Q

the expression of some genes depends on whether they come from the mother or the father.

A

genomic imprinting

Molecular Cell Bio (3 decks)

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