1
Q
The Nuclear Pore Complex (NPC) spans the entire?
A
nuclear envelope
2
Q
The NPC consists of?
A
- 2 parallel rings with 8 subunits outlining the rings
- central granule (transporter)
3
Q
What is the function of the NPC?
A
- transport macromolecules across the nuclear envelope
- important nuclear proteins: nucleoplasmin and exportins/importins
4
Q
What is chromatin?
A
complex of DNA and protein in chromosomes
5
Q
What are two types of chromatin?
A
- euchromatin
- heterochromatin
6
Q
Euchromatin
A
- less dense
- highly active DNA
- only type in prokaryotes
7
Q
Heterochromatin
A
- tightly packed, condensed
- less likely to undergo transcription
- often peripheral in nucleus
8
Q
Functions of heterochromatin?
A
- gene regulation
- chromosome protection
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
10
Q
What is the function of histones?
A
allows DNA to fit in nucleus
11
Q
What is a nucleosome?
A
bead like structures created by spools of DNA
12
Q
What are two important types of nucleic acids?
A
- DNA
- RNA
13
Q
What is the process that makes DNA from DNA?
A
replication
14
Q
What is the process that makes mRNA from DNA?
A
transcription
15
Q
What is the process that makes protein from mRNA?
A
translation
16
Q
What are the two types of nitrogenous bases in DNA and RNA?
A
- purines: double ringed
- pyrimidines: single ringed
17
Q
What are the two purines in DNA?
A
- adenine
- guanine
18
Q
What are the two purines in RNA?
A
- adenine
- guanine
19
Q
What are the two pyrimidines in DNA?
A
- cytosine
- thymine
20
Q
What are the two pyrimidines in RNA?
A
- cytosine
- uracil
21
Q
What is the structure of DNA?
A
- 2 strands twisted in a double helix
- linear arrangement of nucleotides
22
Q
What is the base pairing in DNA?
A
A-T and G-C
23
Q
What is the base pairing in RNA?
A
A-U and G-C
24
Q
How do the two base pairs join together?
A
weak H bonds
25
How many H bonds in A-T?
2 H bonds
26
How many H bonds in G-C?
3 H bonds
27
DNA is always replicated:
3' ----- 5' (template/sense strand)
28
New DNA strand is always:
antiparallel to template/sense strand
| -will grow 5'-------3'
29
What is the start codon?
- DNA: TAC
| - RNA: AUG
30
What is the amino acid the start codon codes for?
methionine
31
What are the three stop codons in DNA?
- ATT
- ATC
- ACT
32
What are the three stop codons in RNA?
- UAA
- UAG
- UGA
33
What is a codon?
3 bases of DNA/RNA that code for a specific amino acid
34
What are the three types of RNA?
- mRNA (messenger)
- tRNA (transfer)
- rRNA (ribosomal)
35
What is the function of mRNA?
carry genetic information from the nucleus to the cytoplasm for protein synthesis
36
What is the function of tRNA?
-decode (translate) mRNA base sequences into a specific amino acid sequence (5'----3')
37
What is the function of rRNA?
-binds mRNA to ribosomes
38
What part of tRNA does mRNA bind?
anticodon
39
What part of tRNA does the amino acid bind?
3' OH end
40
What is a ribosome?
RNA + proteins
41
What indicates the size of a ribosome?
S-values
42
What are the two parts to a ribosome?
- small subunit (40S)
| - large subunit (60S)
43
What are the four binding sites on the ribosome?
- mRNA binding site
- A site (aminoacyl tRNA)
- P site (peptide site)
- E site (lounge site)
44
Where is the mRNA binding site on the ribosome found?
in small subunit
45
Where is the A site found and what is it responsible for?
- on large subunit
| - brings in new a.a. during translation
46
Where is the P site found and what is it responsible for?
- on large subunit
| - carries growing polypeptide chain
47
Where is the E site found and what is it responsible for?
- exit binding site
| - tRNA binds here after it releases the amino acid
48
Where is rRNA created?
in nucleolus
49
Where are membrane-bound ribosomes attached to?
rough endoplasmic reticulum (RER)
50
Where are proteins found?
in cytoplasm
51
Where is the complete ribosome formed?
cytoplasm
52
rRNa in large subunit will act as what?
a ribozyme
53
What is the function of a ribozyme?
join a.a.'s with peptide bonds
54
How many ribosomal sites can hold tRNAs at one time?
only 2
55
What is the purpose of transcription?
to make RNA
56
What are the building blocks for transcription?
ribonucleotide triphosphates (ribose, base, + phosphate groups)
57
DNA template/sense strand runs?
3'-------5'
58
Compliment strand runs?
antiparallel; 5'---------3'
59
Where is RNA Polymerase II found?
in nucleoplasm
60
What is the function of RNA Polymerase II?
enzyme needed to join nucleotide triphosphates to make RNA
61
What is the promoter site?
tells which DNA strand will be the template/sense strand
62
Is the poly A tail a part of DNA?
no
63
Where is the poly A tail found?
on 3' end of transcribed RNA
64
What is the function of the poly A tail?
- 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
What are the expressions regions that do code for sequences of amino acids called?
exons
66
What are the intervening sequences which are non-coding sequences of nucleotides founds in between exons called?
introns
67
What is splicing?
removal of introns
68
Where does splicing occur?
in the nucleus
69
What is the function of splicing?
to leave a continuous sequence of exons
70
What is a spliceosome?
a protein complex and small nuclear RNAs
71
What is another name for spliceosome?
snurps (small nuclear ribonucleo-proteins)
72
When do you only have true mRNA?
only after splicing
73
What are chaperones?
cytoplasmic proteins that aid in the correct assembly or disassembly of new proteins
74
What are the two functions of chaperones?
- fold proteins
| - assemble another protein or protein complex
75
What are the chaperones role in protein folding?
to prevent:
- misfolding
- formation of aggregates or tangles
76
What happens to unassembled or misfolded proteins?
they are transported out of the ER to the cytosol for degradation
77
What are two types of chaperones?
- heat shock proteins: bind and stabilize unfolded proteins
| - chaperonins: small chambers where unfolded proteins are sequestered for proper folding
78
What is enzyme induction?
where a molecule (INDUCER) initiates production of an enzyme
79
What is enzyme repression?
prevent making of an enzyme
80
What does enzyme repression operate on?
feedback inhibition
81
What is the mechanism of enzyme repression?
- repressor often combines with another molecule to block the operator
- therefore blocks binding of RNA Polymerase
- therefore no transcription
82
What is an operon?
a group of closely related genes that can be turned "on" and "off" as a single unit
83
True/False: Each tRNA is specific for a different amino acid.
True
84
There are only a half number of tRNAs (31) due to:
wobbling
85
What permits the flexibility in the pairing between the 3rd base of mRNA codon (inosine) and its complementary base in the anticodon?
wobbling
- I (inosine) can bind with either U, C or A
- therefore fewer tRNAs for some amino acids
86
Where does the combination of a.a. and tRNA occur?
in the cytoplasm
87
What is the combination of a.a. and tRNA mediated by?
aminoacyl synthetase
88
Where does transcription occur?
nucleus
89
Where does activation occur?
cytoplasm
| -tRNA combines with a.a.
90
Where does initiation occur?
- P site on ribosome (in cytoplasm)
| - translation occurs 5'-----3'
91
Where does elongation occur?
- A site on ribosome (cytoplasm)
- growing polypeptide chain occurs on P site
- translation and peptide bond formation occurs 5'-----3'
92
Where does termination occur?
- A site on ribosome
| - stop codon located here
93
What are the two types of protein modifications?
- co-translational (during protein synthesis)
| - post-translational (after protein synthesis)
94
What are the 5 types of co-translational modification?
- deformylation
- a.a. cleavage
- side chain alteration
- disulfide bridge formation
- tertiary folding
95
What are the 2 types of post-translational modification?
- peptide cleavage (ie. proinsulin)
| - addition of prosthetic group (ie. heme to globin)
96
Outline the steps of protein targeting.
- 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
What happens once protein synthesis is completed?
- protein is released in the ER lumen
- protein is transported from ER to Golgi complex
- protein is exported before secretion can occur
98
What is epigenetics?
altering gene function without altering DNA structure
Cell Physiology
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