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Cell Physiology > Exam Two > Flashcards

Exam Two Flashcards

1
Q

The Nuclear Pore Complex (NPC) spans the entire?

A

nuclear envelope

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2
Q

The NPC consists of?

A
  • 2 parallel rings with 8 subunits outlining the rings

- central granule (transporter)

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3
Q

What is the function of the NPC?

A
  • transport macromolecules across the nuclear envelope

- important nuclear proteins: nucleoplasmin and exportins/importins

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4
Q

What is chromatin?

A

complex of DNA and protein in chromosomes

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5
Q

What are two types of chromatin?

A
  • euchromatin

- heterochromatin

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6
Q

Euchromatin

A
  • less dense
  • highly active DNA
  • only type in prokaryotes
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7
Q

Heterochromatin

A
  • tightly packed, condensed
  • less likely to undergo transcription
  • often peripheral in nucleus
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8
Q

Functions of heterochromatin?

A
  • gene regulation

- chromosome protection

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9
Q

What are histones?

A
  • alkaline proteins that act as spools in which DNA winds around
  • primary protein of chromatin that cause chromatin packing and helps in gene regulation, before transcription
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10
Q

What is the function of histones?

A

allows DNA to fit in nucleus

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11
Q

What is a nucleosome?

A

bead like structures created by spools of DNA

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12
Q

What are two important types of nucleic acids?

A
  • DNA

- RNA

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13
Q

What is the process that makes DNA from DNA?

A

replication

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14
Q

What is the process that makes mRNA from DNA?

A

transcription

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15
Q

What is the process that makes protein from mRNA?

A

translation

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16
Q

What are the two types of nitrogenous bases in DNA and RNA?

A
  • purines: double ringed

- pyrimidines: single ringed

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17
Q

What are the two purines in DNA?

A
  • adenine

- guanine

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18
Q

What are the two purines in RNA?

A
  • adenine

- guanine

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19
Q

What are the two pyrimidines in DNA?

A
  • cytosine

- thymine

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20
Q

What are the two pyrimidines in RNA?

A
  • cytosine

- uracil

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21
Q

What is the structure of DNA?

A
  • 2 strands twisted in a double helix

- linear arrangement of nucleotides

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22
Q

What is the base pairing in DNA?

A

A-T and G-C

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23
Q

What is the base pairing in RNA?

A

A-U and G-C

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24
Q

How do the two base pairs join together?

A

weak H bonds

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25
Q

How many H bonds in A-T?

A

2 H bonds

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26
Q

How many H bonds in G-C?

A

3 H bonds

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27
Q

DNA is always replicated:

A

3’ —– 5’ (template/sense strand)

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28
Q

New DNA strand is always:

A

antiparallel to template/sense strand

-will grow 5’——-3’

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29
Q

What is the start codon?

A
  • DNA: TAC

- RNA: AUG

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30
Q

What is the amino acid the start codon codes for?

A

methionine

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31
Q

What are the three stop codons in DNA?

A
  • ATT
  • ATC
  • ACT
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32
Q

What are the three stop codons in RNA?

A
  • UAA
  • UAG
  • UGA
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33
Q

What is a codon?

A

3 bases of DNA/RNA that code for a specific amino acid

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34
Q

What are the three types of RNA?

A
  • mRNA (messenger)
  • tRNA (transfer)
  • rRNA (ribosomal)
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35
Q

What is the function of mRNA?

A

carry genetic information from the nucleus to the cytoplasm for protein synthesis

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36
Q

What is the function of tRNA?

A

-decode (translate) mRNA base sequences into a specific amino acid sequence (5’—-3’)

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37
Q

What is the function of rRNA?

A

-binds mRNA to ribosomes

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38
Q

What part of tRNA does mRNA bind?

A

anticodon

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39
Q

What part of tRNA does the amino acid bind?

A

3’ OH end

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40
Q

What is a ribosome?

A

RNA + proteins

41
Q

What indicates the size of a ribosome?

42
Q

What are the two parts to a ribosome?

A
  • small subunit (40S)

- large subunit (60S)

43
Q

What are the four binding sites on the ribosome?

A
  • mRNA binding site
  • A site (aminoacyl tRNA)
  • P site (peptide site)
  • E site (lounge site)
44
Q

Where is the mRNA binding site on the ribosome found?

A

in small subunit

45
Q

Where is the A site found and what is it responsible for?

A
  • on large subunit

- brings in new a.a. during translation

46
Q

Where is the P site found and what is it responsible for?

A
  • on large subunit

- carries growing polypeptide chain

47
Q

Where is the E site found and what is it responsible for?

A
  • exit binding site

- tRNA binds here after it releases the amino acid

48
Q

Where is rRNA created?

A

in nucleolus

49
Q

Where are membrane-bound ribosomes attached to?

A

rough endoplasmic reticulum (RER)

50
Q

Where are proteins found?

A

in cytoplasm

51
Q

Where is the complete ribosome formed?

52
Q

rRNa in large subunit will act as what?

A

a ribozyme

53
Q

What is the function of a ribozyme?

A

join a.a.’s with peptide bonds

54
Q

How many ribosomal sites can hold tRNAs at one time?

55
Q

What is the purpose of transcription?

A

to make RNA

56
Q

What are the building blocks for transcription?

A

ribonucleotide triphosphates (ribose, base, + phosphate groups)

57
Q

DNA template/sense strand runs?

A

3’——-5’

58
Q

Compliment strand runs?

A

antiparallel; 5’———3’

59
Q

Where is RNA Polymerase II found?

A

in nucleoplasm

60
Q

What is the function of RNA Polymerase II?

A

enzyme needed to join nucleotide triphosphates to make RNA

61
Q

What is the promoter site?

A

tells which DNA strand will be the template/sense strand

62
Q

Is the poly A tail a part of DNA?

63
Q

Where is the poly A tail found?

A

on 3’ end of transcribed RNA

64
Q

What is the function of the poly A tail?

A
  • acts as a signal to allow RNA to move out of nucleus and bind to ribosomes in cytoplasm
  • may increase life-time of the mRNA
65
Q

What are the expressions regions that do code for sequences of amino acids called?

66
Q

What are the intervening sequences which are non-coding sequences of nucleotides founds in between exons called?

67
Q

What is splicing?

A

removal of introns

68
Q

Where does splicing occur?

A

in the nucleus

69
Q

What is the function of splicing?

A

to leave a continuous sequence of exons

70
Q

What is a spliceosome?

A

a protein complex and small nuclear RNAs

71
Q

What is another name for spliceosome?

A

snurps (small nuclear ribonucleo-proteins)

72
Q

When do you only have true mRNA?

A

only after splicing

73
Q

What are chaperones?

A

cytoplasmic proteins that aid in the correct assembly or disassembly of new proteins

74
Q

What are the two functions of chaperones?

A
  • fold proteins

- assemble another protein or protein complex

75
Q

What are the chaperones role in protein folding?

A

to prevent:

  • misfolding
  • formation of aggregates or tangles
76
Q

What happens to unassembled or misfolded proteins?

A

they are transported out of the ER to the cytosol for degradation

77
Q

What are two types of chaperones?

A
  • heat shock proteins: bind and stabilize unfolded proteins

- chaperonins: small chambers where unfolded proteins are sequestered for proper folding

78
Q

What is enzyme induction?

A

where a molecule (INDUCER) initiates production of an enzyme

79
Q

What is enzyme repression?

A

prevent making of an enzyme

80
Q

What does enzyme repression operate on?

A

feedback inhibition

81
Q

What is the mechanism of enzyme repression?

A
  • repressor often combines with another molecule to block the operator
  • therefore blocks binding of RNA Polymerase
  • therefore no transcription
82
Q

What is an operon?

A

a group of closely related genes that can be turned “on” and “off” as a single unit

83
Q

True/False: Each tRNA is specific for a different amino acid.

84
Q

There are only a half number of tRNAs (31) due to:

85
Q

What permits the flexibility in the pairing between the 3rd base of mRNA codon (inosine) and its complementary base in the anticodon?

A

wobbling

  • I (inosine) can bind with either U, C or A
  • therefore fewer tRNAs for some amino acids
86
Q

Where does the combination of a.a. and tRNA occur?

A

in the cytoplasm

87
Q

What is the combination of a.a. and tRNA mediated by?

A

aminoacyl synthetase

88
Q

Where does transcription occur?

89
Q

Where does activation occur?

A

cytoplasm

-tRNA combines with a.a.

90
Q

Where does initiation occur?

A
  • P site on ribosome (in cytoplasm)

- translation occurs 5’—–3’

91
Q

Where does elongation occur?

A
  • A site on ribosome (cytoplasm)
  • growing polypeptide chain occurs on P site
  • translation and peptide bond formation occurs 5’—–3’
92
Q

Where does termination occur?

A
  • A site on ribosome

- stop codon located here

93
Q

What are the two types of protein modifications?

A
  • co-translational (during protein synthesis)

- post-translational (after protein synthesis)

94
Q

What are the 5 types of co-translational modification?

A
  • deformylation
  • a.a. cleavage
  • side chain alteration
  • disulfide bridge formation
  • tertiary folding
95
Q

What are the 2 types of post-translational modification?

A
  • peptide cleavage (ie. proinsulin)

- addition of prosthetic group (ie. heme to globin)

96
Q

Outline the steps of protein targeting.

A
  • signal sequence (SS) which is 20-30 a.a. long is made at the N-term
  • signal recognition particle (SRP) recognizes SS and binds to it, halting translation
  • SS-SRP complex is recognized by SRP docking protein (SRP receptor) on RER membrane
  • SS + ribosome-mRNA complex is inserted through the ER membrane
  • signal peptidase dissociates SRP, separating SS
  • translation resumes
  • protein synthesis is completed
97
Q

What happens once protein synthesis is completed?

A
  • protein is released in the ER lumen
  • protein is transported from ER to Golgi complex
  • protein is exported before secretion can occur
98
Q

What is epigenetics?

A

altering gene function without altering DNA structure

Cell Physiology (1 decks)

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