cell bio exam 3 Flashcards


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1

top 3 leading cancer related deaths

result from proto-oncogene activation and TSG inactivation

lung

breast/prostate

colorectal

2

minimum amount of DNA alterations needed for a cell to become malignant

6

3

process of a normal cell evolving into a highly malignant cell

tumor progression

4

transcription factor, most frequently mutated gene in cancer, guardian of the genome, regulates at G1- growth arrest and apoptosis, suffers from point mutation which inactivates it -resulting in no DNA repair

p53

inactivated in 50% of all cancers

5

genes that are like the car brakes, help regulate cell growth, gives loss of function to mutant genes

TSG

tumor suppressor genes

6

cell dividing out of control, mutant form of normal has genes, dominant genes, code for RTK, G proteins, transcription factors, Ras gene, classified as

oncogene

7

normal cell division like a gas pedal on a car, but has the potential for a gain-of-function in cancer, these genes are

proto-oncogene

8

signaling that effects the same cell

autocrine

9

signaling that effects neighboring cells, even of a different type

paracrine

10

long distance signaling that is able to signal the whole body, usually through the circulatory

endocrine

11

high-affinity cell surface receptors for many polypeptide growth factors, cytokines, and hormones, key regulators of normal cellular processes but also to have a critical role in the development and progression of many types of cancer

enzyme-coupled receptors

Receptor tyrosine kinases (RTK)

12

how does the G-protein coupled receptor work

Binding of an agonist results in a conformation change in the receptor that is transmitted to the bound α subunit, the α subunit exchanges GTP in place of GDP which in turn triggers the dissociation of it from the βγ dimer and from the receptor. The dissociated α subunit interacts with other intracellular proteins to continue the signal transduction cascade

13

a large protein family of receptors that sense molecules outside the cell and activate inside signal transduction pathways and, ultimately, cellular responses. They are called seven-transmembrane receptors because they pass through the cell membrane seven times, ligands that bind and activate these receptors include light-sensitive compounds, odors, pheromones, hormones, and neurotransmitters, and vary in size from small molecules to peptides to large proteins. They are involved in many diseases, and are also the target of approximately 40% of all modern medicinal drugs

G-protein coupled receptor

guanine nucleotide

14

general name for a group of more that 100 diseases in which cells in a part of the body begin to grow out of control

cancer

15

Conversion of an impulse or stimulus from one physical or chemical form to another. In cell biology, the process by which a cell responds to an extracellular signal.

signal transduction

16

Protein that recognizes and responds to a specific signal molecule.

receptor

17

A set of proteins and small-molecule second messengers that interact with each other to relay a signal from the cell membrane to its final destination in the cytoplasm or nucleus.

intracellular signaling pathway

18

Extracellular signal molecule that is secreted and transported via the bloodstream (in animals) or the sap (in plants) to target tissues on which it exerts a specific effect.

hormone

19

The molecular mechanisms by which cells detect and respond to external stimuli and send messages to other cells.

cell signalling

20

what do vSNARES do

SNAREs on the vesicle compliment the target tSNAREs

21

in order to use protein translocators, is the protein folded or unfolded?

how about a nuclear pore?

unfolded to go through the membrane

folded to go through the nucleus

22

Which of the following is true of lysosomes?

A. The products of digestion in lysosomes leave the lysosome by transport vesicles.
B. Most of the lysosomal membrane proteins have glycosylated regions on the cytosolic side of the membrane.
C. Lysosomal enzymes are optimally active in the acidic conditions maintained within lysosomes.
D. Lysosomes form from vesicles that pinch off from the endoplasmic reticulum

c

23

Proteins destined for regulated secretion:

A. have special surface properties that cause them to form aggregates that are packaged into secretory vesicles.
B. have a series of amino acids that act as a tag that marks them for packaging into secretory vesicles.
C. are cleaved from membrane domains in the Golgi apparatus prior to being packed into secretory vesicles.

a

24

Which type of protein binds to improperly folded or improperly assembled proteins in the ER, holding them there until proper folding occurs?

A. Tethering proteins
B. Glycosylating proteins
C. Chaperone proteins
D. Antibody proteins

c

25

Vesicle budding is driven by the assembly of a protein coat.

A. True
B. False

a

26

The ER signal sequence on a growing polypeptide chain is recognized by a signal recognition particle (SRP) in the cytosol. This interaction:

A. causes the polypeptide chain to dissociate from the ribosome.
B. causes the ribosome to return to the pool of free ribosomes in the cytosol.
C. guides the ribosome and its polypeptide to the ER membrane.
D. speeds the synthesis of the polypeptide chain

c

27

Which of the following is true?

A. A special class of ribosomes embedded in the ER translates the proteins destined for that organelle.
B. A common pool of ribosomes is used to synthesize both the proteins that stay in the cytosol and those that are destined for the ER.
C. All ribosomes are attached to the ER when they are synthesizing a protein.

b

28

Which of the following statements is NOT true of mitochondrial proteins that are synthesized in the cytosol?

A. The proteins are unfolded as they are transported into the mitochondria.
B. The proteins cross both the inner and outer mitochondrial membranes as they are imported.
C. The proteins are transported across the mitochondrial membranes while being synthesized.
D. Chaperone proteins help draw the proteins inside the mitochondrion.
E. The proteins usually have a signal sequence at their N-terminus.

c

29

Which proteins bind to nuclear localization signals on newly synthesized proteins?

A. Nuclear pore proteins
B. Nuclear transport receptors
C. Signal-recognition particles

b

30

The interiors of the ER, Golgi apparatus, endosomes, and lysosomes communicate with each other in which of the following ways?

A. By small vesicles that bud off of one organelle and fuse with another
B. By open pores that allow ions to exit and enter the organelles
C. They do not communicate with one another.
D. By excreting hormones and other small signaling molecules

a

31

Which organelle is essentially a small sac of digestive enzymes that functions in degrading worn-out organelles, as well as macromolecules and particles taken into the cell by endocytosis?

A. An endosome
B. The Golgi apparatus
C. A lysosome
D. The endoplasmic reticulum
E. A peroxisome

c

32

Which organelle sorts ingested molecules and recycles some of them back to the plasma membrane?

A. An endosome
B. The Golgi apparatus
C. A lysosome
D. The endoplasmic reticulum
E. A peroxisome

a

33

Which organelle receives proteins and lipids from the endoplasmic reticulum, modifies them, and then dispatches them to other destinations in the cell?

A. A mitochondrion
B. An endosome
C. The Golgi apparatus
D. The nucleus
E. A peroxisome

c

34

what signals for proteins to have parts of them embedded in the membrane ER

stop transfer sequence

start transfer sequence

both hydrophobic

35

two protein components help guide ER signal sequences to the ER membrane

signal recognition particle (SRP) in the cytosol binds with the ribosome and the signal sequence

SRP receptor embedded in the ER membrane recognizes the SRP

36

2 kinds of proteins transferred from the cytosol to the ER

water soluble completely translocated

prospective transmembrane partly translocated ( embedded in membrane )

37

small membrane enclosed organelles that contain several enzymes that produce hydrogen peroxide and have a variety of other functions, derived from the endoplasmic reticulum or replicate by fission- it also transports proteins via translocation

peroxisome

38

main site of lipid synthesis

ER

39

how do proteins know to go to the mitochondria

signal sequence at their N-terminus recognized by a chaperone protein that grabs it, unfolds it, the folds back once entered, requires ATP

use a translocator channel- similar to a nuclear pore, but instead of one big pore, it is one in each bi-layer

40

how are mitochondria and chloroplasts similar to nucleus

double phospholipid bi-layer

own DNA and therefore own proteins

recognize signal sequence- positive charge hydrophobic AA

41

what brings proteins to the nucleus

importin- nuclear import receptors

take the protein in its 3 prime shape unlike other oraganelles

42

how do proteins get to where they need to go

signal sequence- nuclear localization signal

positive charged hydrophobic lysine and arginine

binds to the nuclear import receptor to bring it in - requires GTP for energy

43

nuclear pores are made of

30 proteins complex, act as a gate for proteins to enter and RNA to exit

44

inner nuclear membrane conatins

membrane most similar to the cell membrane and is continuous with the membrane of the ER

45

inner layer of nuclear membrane conatins

proteins and binding sites for chromosomes

nuclear lamina for structural support

46

how many membranes of the nuclear envelope, aka nuclear membrane

4

double phospholipid bi-layer

inner and outer

47

The lac operon:
A. is found in eukaryotic cells
B. codes for the sequence of amino acids in lactase
C. regulates translation of mRNA
D. regulates transcription by turning on or off the production of a repressor protein
E. regulates DNA replication by turning on or off the production of an inducer protein

d

48

At the E site

A)transfer RNA is released

B)anticodons match with codons

C)peptide bonds are formed between amino acids

D)transcription occurs

a

49

An activator must react with its substrate before it can bind to DNA.

A)True

B)False

a

50

Negative control occurs when a repressor is inactivated by an inducer.

A )True

B)False

a

51

In regulation by induction

A)an inducer inactivates the repressor so transcription can proceed

B)an inducer inactivates the repressor so transcription is stopped

C)an inducer activates the repressor so transcription can proceed

D)an inducer activates the repressor so transcription is stopped

a

52

In regulation by repression

A)a sugar, such as lactose, acts as an inducer and combines with the repressor to prevent transcription

B)an inducer activates the activator so that it binds to DNA and prevents transcription

C)an amino acid activates the repressor so that the repressor binds to the operator and prevents transcription

D)an amino acid binds to the operator, blocking the repressor, allowing transcription to proceed

c

53

Transcription is turned off by

A)induction

B)repression

C)activation

D)all of the above

d

54

how does the cell know what proteins go where

1. signal patches made of amino acid residues that are distant to one another in primary form but are close together in tertiary structure

2. sorting signal made of amino acid sequences

no signal= stays in cytosol and functions there

55

proteins transported to the nucleus are completely synthesized in the cytosol and ______ before import, unlike other organelles

correctly folded

56

three ways proteins are transported throughout the cell

1. through nuclear pores from cytosol into nucleus

2. across organelle membranes via protein translocators

3. by transport vesicles through plasma membrane to outside of cell

57

two ways cells can isolate and organize their chemical reactions

aggregate different enzymes

confine different metabolic processes within different membrane enclosed compartments (organelles)

58

large protein complexes found in the cytosol and nucleus that have protease activity

proteosomes

59

enzymes that degrade proteins by a process known as proteolysis (hydrolyzes peptide bonds)

proteases

60

regulatory RNA's work by

base pairing with complementary sequences within target mRNA's, leading to mRNA degradation and inhibition of translation

61

two key aspects of eukaryotic translation are regulated by phosphorylation- same as effects in DNA transcription

1. recognition of the mRNA by ribosome can be inhibited by PO4

2. 5' cap binding proteins can be bound by non-PO4 binding proteins

62

proteins that block the translation of mRNA because they prevent the attachment of ribosomes by binding to specific nucleotide sequences in the 5' untranslated region (promoter)

translation repressor

63

translation of mRNA is regulated by regulatory proteins that are needed so ribosomes can translate mRNA are called

translation factors

64

three chemical modifications to histones to regulate transcription

1.activator- histone acetyltransferases (nucleosomes loosened)

2.repressor- histone deacetylases

3.repressor- histone methyltransferases

65

two ways transcription regulators act

1.directly effect the assembly process that require RNA polymerase and transcription factors at the promoter- histone proteins

2.modify the chromatin structure of promoter regions- DNA itself

66

cell defense mechanism that destroys foreign RNA, man made, double stranded

siRNA

67

controls gene expression, single stranded, regulate our own genes, base pairs with specific mRNA

miRNA

68

in the absence of lactose, the lac repressor

A)binds to the operator and prevents transcription

B)binds to the CAP site and prevents transcription

C)binds to the CAP site and facilitates transcription

D)binds to the operator and facilitates transcription

a

69

The main regulatory gene that acts on the lac operon is a

lac repressor with no lactose and CAP activator with no glucose

repressor binds to the lac operon operator, where it blocks RNA polymerase from transcribing the lac operon

CAP binds to cyclic cAMP before it can bind to DNA, switches on genes to increase intracellular cAMP

70

In a eukaryote, activating transcription factors may stimulate gene expression by binding to a DNA site called a(n) _____.

enhancers

71

You have inserted the gene for human growth factor into the E. coli lactose operon, replacing the structural genes with the gene for human growth factor. What substance must you add to your culture of bacteria to cause them to produce human growth factor for you?

allolactose

72

In an inducible operon, the inducer is often the _____ in the pathway being regulated; the inducer binds to the _____, thus rendering it _____.

substrate ... repressor ... inactive

73

the genetic information contained within the order of nucleotides in mRNA is interpreted to generate the linear sequence of amino acids

translation

74

which part of the mRNA is used

middle

75

the protein coding region with nonoverlapping string of codons

ORF- open reading frame

76

translation starts at what end

5' to the 3'

77

how many possible codons

3 bases, 4 nucleotides = 43 = 64

61 are translated into AA, the rest are stop codons

78

provides the genetic information template to be translated

mRNA

79

provides the interface between the mRNA and their corresponding AA

tRNA

80

enzyme links AA to their corresponding tRNA, one for each of the 20 AA

aminoacyl-tRNA synthetase

81

coordinates recognition between the mRNA and corresponding tRNA and catalyzes the peptide bond formation between tRNA associated AA

ribosomes

82

does transcription and translation occur at the same time in eukaryotes

no

one is in the nucleus and the other in the cytoplasm

83

three binding sites in the ribosome

A- enters

P- attaches AA

E- exit

84

what determines the start of translation

5' end of ORF is methionine (AUG)

85

base pairing results in structural conformational change which in turn causes some of the bound initiation factors to be

released and new ones bind

86

in addition to codon-anticodon base pairing, the ribosome has additional proofreading mechanisms to ensure

the correct tRNA is brought into the A site

87

stop codons are recognized by proteins called

release factors

activates hydrolysis of the polypeptide from the tRNA

88

an mRNA with multiple ribosomes attached is a

polyribosome

89

Which type of RNA includes the anticodon and brings the amino acids to the site of protein synthesis?

a. mRNA
b. rRNA
c. tRNA
d. DNA
e. mDNA

c

90

Where does translation occur?

A.Cytoplasm

B.Nucleus

C.Mitochondria

D. Ribosome

a

91

Which molecule contains codons?

A)DNA

B)mRNA

C)tRNA

D)rRNA

b

92

What form of RNA binds to both the codon and an amino acid?

A)mRNA

B)tRNA

C)rRNA

D)None of the above.

b

93

What area of a gene does the RNA polymerase bind to?

A)promoter

B)exon

C)intron

D)codon

a

94

RNA is transcribed using the ____ strand of DNA.

A)coding

B)alternate

C)template

D)non-template

a

95

Which of the statements below is FALSE?

A)The genetic code is overlapping.

B)The genetic code is universal.

C)Degenerate codons specify the same amino acids

D)The genetic code is triplet in nature.

a

96

The first mRNA codon to specify an amino acid in a protein sequence is always _____.

A)TAC

B)UAA

C)UAG

D)AUG

d

97

Transfer RNAs bind to messenger RNAs during translation via their _____.

A)codon

B)anticodon

C)template

b

98

Of the ____ different possible codons, ____ specify amino acids and ____ signal stop.

A)20; 17; 3

B)180; 20; 60

C)64; 61; 3

D)61; 60; 1

c

99

An antibiotic interferes with the ability of the ribosome to move. What effect would exposure to this chemical have on a bacterial cell?

A)Protein synthesis will be enhanced.

B)The protein synthesized will be shorter than normal.

C)The protein synthesized will be longer than normal.

D)No proteins will be produced.

d

100

What sequence on the template strand of DNA corresponds to the first amino acid inserted into a protein?

A)TAC

B)UAA

C)UAG

D)AUG

a

101

Which of the following is an example of the degeneracy of the genetic code?

A)A given amino acid has more than one codon.

B)Each codon specifies more than one amino acid.

C)The first base specifies the amino acid.

D)The genetic code is not degenerate

a

102

During translation, the _____ site within the ribosome holds the growing amino acid chain while the ____ site holds the next amino acid to be added to the chain.

A)A; P

B)P; A

C)A; B

D)B; A

b

103

Translation terminates when _____.

A)the A site is empty

B)a stop codon is present in the A site

C)a release factor is present in the P site

D)translation reaches the end of the mRNA

b

104

what dictates which genes are expressed, where, and when

regulatory mechanisms

105

we rarely use any more of _____ % of our genes at any given time

5-10%

106

all cells have the same DNA and therefore the same

genes

but they are not all expressed- gives specificity to muscle, nerve, skeletal cells

107

all cells require

ATP

108

what events does gene expression control

when and how often a gene is transcribed

how mRNA is spliced

which mRNA is transported

how quickly mRNA is degraded

which mRNA is translated

how quickly protein is degraded

109

what stage is the most regulated

initiation of transcription

110

slight continuous level of expression of a gene

basal level

111

transcription activator proteins bind to the DNA and RNA polymerase near the promoter which brings in the RNA polymerase to the promoter

cooperative binding resulting from recruitment

an indirect mechanism because of the domino effect

112

two proteins acting in one complex, need both of them to be active, one end binds to the DNA binding site, the other end binds to the RNA polymerase

dimer

113

set of three genes plus other things in E. coli involved in the transport and breakdown of lactose into glucose

lac operon

114

what is the lac operon composed of

3 genes- lacZ, lacY, lacA

promoter

terminator

operator

115

what is the lac operon regulated by

availability of lactose and glucose

116

how does a cell use lactose as energy

produces beta-galactosidase to break down lactose into glucose

117

lac promoter directs transcription of all 3 genes as a single mRNA molecule called

polycistronic message

118

what does lacZ do

produces enzyme beta-galactosidase to break down lactose into galactose and glucose

119

what does lacY do

produces the protein lactose permease that transports lactose into the cell

120

what does lacA do

produces the enzyme thiogalactosidase transacetylase to break down the toxic thiogalactosidase that was brought into the cell with lactose

121

when lactose is present and glucose is not then the genes are

expressed

122

regulation in the expression of the lac operon is upstream and controlled by

if or not there is an activator

CAP

lac repressor which is encoded by a gene

123

gene that encodes the lac repressor that binds to the lac promoter region and prevents transcription when there is no lactose

lacI gene and allolactose

124

when glucose is present but there is no lactose, then

A)cyclic AMP is high, the catabolite activator protein (CAP) binds to the activator binding site, and transcription of lactose is turned on

B)cyclic AMP is low, CAP binds to the site activator binding site, and transcription of lactose is turned on

C)cyclic AMP is high, CAP does not bind to the activator binding site, and transcription of lactose is turned on

D)cyclic AMP is low, CAP does not bind to the activator binding site, and transcription is turned off

d

inhibitor activated

lac repressor binds to operator region and prevents RNA polymerase from binding

125

when glucose is absent but lactose is present, then

promoter activated

an allosteric effect on CAP binding site

cyclic cAMP binds to CAP which then binds to the CAP site on mRNA and RNA polymerase then attaches to the promoter site so transcription can occur

126

when both glucose and lactose are present

A)cyclic AMP is high so transcription occurs

B)the lac repressor binds with the lactose and transcription occurs

C)RNA polymerase is able to bind to the operator so transcription occurs

D)transcription is at a minimal level

d

a basal level of transcription occurs

127

protein exerts its effects from a distance away from the promoter region

works by changing the structure of the mRNA so it bends around in a loop,

can activate or repress

enhancer site for binding of an activator protein