Revision Flashcards
1
Q
What kind of DNA molecules could serve as an effective template for DNA synthesis?
A
partial double-stranded DNA
2
Q
What is a nucleoside?
A
Sugar + Nitrogenous base
3
Q
What type of replication results in one duplex containing both parental strands and the other duplex containing two new strands of DNA after the two parental strands had served as templates for the two daughter strands?
A
conservative replication
4
Q
What is a DNA nucleotide?
A
Sugar + Nitrogenous base + Phosphate group
5
Q
The backbone of a DNA molecule is ______ ?
A
It is made up of alternating phosphate and sugar groups
6
Q
The information encoded in DNA resides in _____ ?
A
DNA base sequence
7
Q
What is an advantage of making mRNA copies of genes?
A
- The genetic information can be stored relatively safely in the nucleus while mRNA is a working copy.
- mRNA is smaller than DNA and easier to move out into the cytoplasm where proteins are made.
- Making multiple copies of mRNA allows an amplification of synthetic output over what could be made from one gene in DNA.
- mRNAs have short half-lives allowing a cell to change its responses to the environment efficiently.
8
Q
The enzyme that is responsible for the synthesis of RNA from a DNA template is called _____ ?
A
DNA-dependent RNA polymerase
9
Q
What kind of enzyme is the RAS gene product, the Ras protein?
A
a GTPase
10
Q
In what ways do RNAs differ from DNA?
A
- RNAs often have nonstandard mismatched base pairs.
- RNAs often have modified nitrogenous bases.
- RNAs have an extra oxygen atom on the pentose sugar of their nucleotides.
- The nitrogenous bases of RNA are adenine, guanine, cytosine and uracil instead of the adenine, guanine, cytosine and thymine of DNA.
11
Q
What are the nitrogenous bases of a nucleic acid?
A
- Adenine
- Cytosine
- Guanine
- Thymine
- Uracil
12
Q
What is the conditions required for the initiation of each fragment on the lagging strand?
A
- Must wait for the parental strands to separate
- Requires exposure of more template
- Requires movement of the replication fork
- Is carried out by primase
13
Q
What is the minimum number of tRNAs that a cell could have?
A
20
14
Q
Which of the following is an ability possessed by a tRNA?
A
- Each tRNA can be linked to a specific amino acid.
2. Each tRNA is able to recognize a particular codon.
15
Q
What is the significance of the variability of the third nucleotide in a codon?
A
The same tRNA can recognize more than one codon.
16
Q
What are the two sites within a cell at which protein synthesis is generally thought to occur?
A
- cytosolic surface of RER
2. free ribosomes
17
Q
Which part of the cell cycle is the most variable?
A
G1 phase
18
Q
Why can cancer cells proliferate in the absence of serum?
A
The cell cycle of cancer cells does not depend on signals transmitted from serum growth-factor receptors located at their surface.
19
Q
If a cell loses pRb activity because it does not have a normal copy of the RB gene, what happens?
A
- pRb cannot inactivate E2F transcription factors.
- pRb cannot bind to the E2F transcription factors.
- The cell would tend to pass to S phase much more easily than normal and would lack all or part of the regulation normally present at the G1 – S transition.
20
Q
Sometimes an enzyme is activated by a receptor and brings about the cellular response by generating a second messenger. Such an enzyme is called _____ .
A
Effector
21
Q
Where is the guanine nucleotide-binding site of the G protein located?
A
on the G-alpha subunit
22
Q
State the two types of nitrogenous base and their differences.
A
- Pyrimidines - one carbon-nitrogen ring and two nitrogen atoms.
- Purines - two carbon-nitrogen rings and four nitrogen atoms
23
Q
List the complementary nitrogenous bases.
A
- A - T (adenine-thymine)
- A - U (adenine-uracil)
- G - C (guamine-cytosine)
24
Q
How many types of purines are there?
A
- Cytosine
- Thymine
- Uracil
25
How many types of pyrimidines are there?
1. Adenine
| 2. Guamine
26
The phosphate group of a nucleotide is usually attached to the ___-carbon of the
sugar?
5' (note it's not 5 !)
27
According to the rules of the wobble hypothesis, what codons could
pair with the anticodon 3'-GGU-5'?
1. 5'-CCA-3'
| 2. 5'-CCG-3'
28
The greatest similarities among codons specifying the same amino acid occur _____ ?
In the first two nucleotides of the triplet
29
The _______ strand fragment grows away from the replication fork toward the ___-end of the previously synthesized fragment to which it is subsequently linked.
1. lagging
| 2. 5'
30
Each replication fork corresponds to a site where the _____ .
1. parental double helix is undergoing strand separation
2. DNA is polymerized
3. nucleotides are being incorporated into the newly synthesized complementary strands
31
Is cytosine and ribose a RNA nucleoside?
yes
32
Is thymine, ribose and phosphate group a RNA nucleotide?
no
33
Is uracil and ribose a DNA nucleoside?
no
34
Strand initiation during replication is carried out by an enzyme that makes a short RNA molecule that is used as a primer; the enzyme is a distinct type of RNA polymerase, called _______.
primase
35
What is the result of a nonsense mutation?
premature termination of the protein chain
36
The DNA strand growing away from the replication fork grows _______ in a 5'—>3'
direction and is called the ________.
1. discontinuously
| 2. lagging strand
37
What is responsible for degrading misfolded proteins in the cytoplasm?
proteasomes
38
What are ribosomes are made of?
1. Proteins
| 2. rRNA
39
What is the most prominent type of endoplasmic reticulum found in cells that secrete large amounts of protein?
rough endoplasmic reticulum (RER)
40
What disease can be defined as resulting from a breakdown in a cell's ability to regulate its own division?
Cancer
41
What happens if functional p53 protein is not present in the cells?
1. The cell makes no p21 inhibitory protein.
2. The cell proceeds to S phase before it is ready and before DNA repairs are completed.
3. Cancer may arise.
42
How is signaling by an activated G-alpha subunit terminated?
The bounded GTP is hydrolyzed to GDP.
43
How is RAS activity turned off?
It is turned off by hydrolysis of its bounded GTP to GDP.
44
Taxol inhibits the disassembly of microtubules. How does this harm the cells?
The cell cannot assemble new and needed structures containing microtubules.
45
What is a function of membranes?
1. compartmentalization
2. selectively permeable barrier
3. mediates intercellular interactions
4. helps cells respond to external stimuli
46
Along which pathway do materials or the membrane surface move into the cell from the outside to cytoplasmic compartments?
biosynthetic pathway
47
Cells that have stopped dividing and are arrested in a stage preceding the initiation of DNA synthesis are said to be in a ______ state.
G1 phase
48
What is (are) made on free ribosomes?
a. proteins that are to remain in the cytosol
b. peripheral proteins of the inner cell membrane surface
c. peripheral proteins of the outer cell membrane surface
d. proteins to be transported to the nucleus
a. proteins that are to remain in the cytosol
b. peripheral proteins of the inner cell membrane surface
d. proteins to be transported to the nucleus
* free ribosomes produce proteins for the cell, while bound ribosomes produce proteins that are transported out of the cell.
49
What happens to receptors that carried lysosomal enzymes once they have delivered their cargo to late endosomes?
They are recycled back to the TGN.
50
What is p53?
1. Is a transcription factor that activates expression of many other genes involved in cell cycle regulation and apoptosis
2. activates the transcription of p21 mRNA
3. leads genetically damaged cells along the pathway leading to apoptosis
51
What kind of forces are thought to hold microtubular structure together?
noncovalent interactions
52
Along which structure do membranous vesicles typically engage in local movement in the cell periphery of an animal cell?
microtubules
53
Once a sensor detects the presence of a defect, it triggers a response that temporarily arrests further progress of the cell cycle. What is the reason for the delay?
1. The delay allows the cell time to repair any damage or correct a defect before the cell cycle continues.
2. If mammalian cells divide without fixing genetic damage, they can be transformed into cancer cells.
54
What oncogenes do?
1. encode proteins that promote the loss of growth control
2. encode proteins that promote the conversion of a cell to the malignant state
3. may act as accelerators of cell proliferation and tumorigenesis
55
What type of replication results in two duplex containing one parental strand and one new strand of DNA after the one parental strand had served as templates for the two daughter strands?
Semi-conservative replication
56
Under the same conditions that lead cultured normal cells to exhibit decreased growth rates, what happens to malignant cells?
1. They continue to grow and divide.
2. They pile on top of one another forming clumps.
3. They fail to respond to the types of signals that cause normal cells to cease growth and division.
57
What generally happens if cells that have been transformed into cancer cells in culture by carcinogenic chemicals or viruses are introduced into a host animal?
They generally cause tumors in the host animal.
58
What is the most important property of a cancer cell, whether it is in the body or the culture dish?
its loss of growth control
59
What is similar about the abilities of normal cells and cancer cells to grow and divide when cultured under conditions favorable for cell proliferation?
Malignant and normal cells grow and divide at similar rates.
60
What do all of the environmental agents that can cause cancer have in common?
They can all alter the genome.
61
Why do tumor viruses transform normal cells into cancer cells?
They carry genes whose products interfere with the cell's normal growth-regulating activities.
62
What cells possess unlimited proliferation potential, have the capacity to produce more of themselves and can give rise to all of the cells of the tissue?
stem cells
63
Another word for malignant transformation is _____ .
tumorigenesis
64
What happens if one culture’s cells from a tumor lacking a functional RB gene after reintroducing a wild-type copy of the gene into those cells?
The cancer phenotype disappears.
*phenotype = set of observable characteristics resulting from the interaction of its genotype with the environment
65
What part of the cell cycle does the pRB protein help to regulate?
the G1 - S transition
66
What happens to a cell that is carrying damaged DNA if both of its TP53 alleles become inactivated?
1. It lacks the genetic integrity required for controlled growth.
2. It fails to be destroyed.
67
What condition is indicative of healthy G1 cells?
The p53 protein is found at very low levels.
68
What happens at the G1 phase if a cell sustains genetic damage?
1. The p53 protein concentration rises very rapidly.
2. There is no increased expression of the p53 gene.
3. The p53 protein exhibits an increase in stability.
69
Under what circumstances are tumor cells likely to undergo apoptosis when they have sustained damage to DNA?
if they have a functioning TP53 gene
70
What would result from a lack of a functional TP53 gene?
1. prevents a cell carrying damaged DNA from being destroyed
| 2. will allow genetically unstable cells to continue to divide
71
What is the oncogene that is most often mutated in human tumors and what does it encode?
RAS gene, a GTP-binding protein that serves as an on-off switch for a key cell signaling pathway that controls cell proliferation
72
The genes involved in tumorigenesis constitute a specific subset of the genome whose products are involved in what activities?
1. progression of a cell through the cell cycle
2. adhesion of a cell to its neighbors
3. apoptosis
4. repair of DNA damage
73
How do cells in the body of a multicellular organism usually communicate with each other?
electrical signals between cells
74
No matter how the signal initiated by the binding of a ligand is transmitted (via a second messenger or by protein recruitment), what is the outcome of that signal?
A protein at the top of an intracellular signaling pathway is activated.
75
What is not the characteristics of the pathways activated by second messengers?
Each protein in the pathway typically acts by altering the conformation of the previous (upstream) protein in the series, an event that activates or inhibits the protein.
76
What kind of response is not initiated when signals traveling down signaling pathways reach their target proteins, which are usually involved in basic cellular processes?
cessation of DNA synthesis and degradation of DNA
77
The low-molecular-weight building blocks of polymers are called _____ .
monomers
78
What biomolecule is not a macromolecule formed by polymerization?
lipids
79
How do amino acids like hydroxylysine and thyroxine, which are not among the 20 amino acids that are inserted into proteins, get into proteins?
They are the result of the alteration of R groups of the 20 amino acids after their incorporation into the polypeptide.
80
Membrane-associated carbohydrates exhibit a major asymmetry in their distribution. What is it?
1. Membrane-associated carbohydrates face toward the outside of cells into the extracellular space.
2. Internal cellular membrane carbohydrates face the organelle interior and away from the cytosol.
81
What organelle is fluid-filled, membrane-bound spherical vesicles surrounded by a single, continuous lipid bilayer, resembling a natural membrane. It is hoped that these structures loaded with DNA or an anticancer drug may be useful in treating cancer or some other disease.
Liposome
82
What kinds of molecule could be placed in liposome walls to get them to bind selectively to surface of the correct target cell?
1. Antibodies
| 2. Hormones
83
What kind of membrane protein penetrates into the hydrophobic part of the lipid bilayer?
Integral proteins
84
What kind of membrane protein does not penetrates into the hydrophobic part of the lipid bilayer?
Pheripheral proteins
85
What kind of membrane protein is found entirely outside the bilayer on the extracellular or cytoplasmic surface? These proteins are associated with the membrane surface by noncovalent bonds.
Pheripheral proteins
86
What kind of membrane protein is not at all embedded within the hydrophobic core of the lipid bilayer?
Pheripheral proteins
87
On average, how many amino acids engaged in α-helices does it take to cross the hydrophobic part of the membrane?
20 - 30 amino acids
88
What are the characteristics of microtubules/microfilaments?
1. polymer of protein subunits
| 2. protein subunits connected to one another by weak, noncovalent bonds
89
What are the advantages of the type of structure displayed by microtubules/microfilaments?
1. It lends itself to rapid assembly and disassembly
| 2. It is dependent upon and responsive to complex cellular regulation
90
What type of cytoskeletal element is characterized as a hollow, rigid cylindrical tube with walls composed of tubulin subunits?
Microtubules
91
What type of cytoskeletal element is described as a solid structure composed of actin subunits?
Microfilaments
92
What activities are identified as functions of the cytoskeleton?
1. a dynamic scaffold that provides structural support that helps to determine cell shape
2. internal framework that positions organelles in cell interior
3. a network of tracks that direct the movement of materials and organelles within the cell
4. a force-generating apparatus
93
What kinds of materials appear to be moved around the cell by the tracks of the cytoskeleton?
1. mRNA molecules
| 2. membranous carriers between the ER and Golgi complex
94
The splitting of a parent cell into two daughter cells is called ______.
Cytokinesis
95
You inject an antibody against the protein actin into a living animal cell. After the injection, the cell begins mitosis and the process proceeds normally until cytokinesis would normally occur. Instead, the contractile ring does not form and cytokinesis does not occur. What do these results mean?
1. Cytokinesis is dependent upon microfilaments.
| 2. A major component of the contractile ring is microfilaments.
96
You inject an antibody against the protein tubulin into a living animal cell. After the injection, the cell begins mitosis but the chromosomes do not become attached to the spindle; in fact, there is no spindle. The contractile ring does form however. What do these results mean?
1. The separation of chromosomes by the spindle is dependent upon microtubules.
2. The spindle is composed, at least in part, by microtubules.
97
You inject a fluorescent antibody against the protein actin into a living animal cell. After the injection, the cell begins mitosis and fluorescence appears over the contractile ring. What do these results mean?
1. The contractile ring contains actin.
| 2. A major component of the contractile ring is likely to be microfilaments.
98
You inject a fluorescent antibody against the protein tubulin into a living animal cell. After the injection, the cell begins mitosis and the spindle fluoresces. What do these results mean?
1. The spindle contains tubulin.
| 2. The spindle is composed, at least in part, by microtubules.
99
What process or processes are included within M phase?
1. cytokinesis
| 2. mitosis
100
What is mitosis?
Separation of duplicated chromosomes into two daughter nuclei
101
What is cytokinesis?
separation of the entire cell and its cytoplasm into two daughter cells
102
When do most of the preparations for mitosis occur, including such activities as DNA replication?
Interphase
103
What is G2 phase?
period in the cell cycle between the end of DNA replication and the beginning of mitosis
104
What is another name for the G1, G2 and S stages of the cell cycle combined?
Interphase
105
What is the stage of the cell cycle in which cells usually arrest when they stop dividing?
G1 phase
106
What is the stage of the cell cycle which cells usually leave when they become cancer cells?
G1 phase
107
What is the stage of the cell cycle which proteins needed for cell division are most likely to be made?
G2 phase
108
What are the DNA building blocks known as?
nucleotides
109
What are the characteristics of the two strands of the DNA double helix?
1. Anti-parallel
| 2. Complementary to each other
110
What gives a DNA molecule its negative charge?
Phosphate group
111
The two chains of the DNA double helix are held together by what interactions?
Hydrogen bonding
112
What is the site on DNA to which RNA polymerases bind before initiating transcription is called?
promoter region
113
What are the proteins that help RNA polymerase recognize promoters called?
Transcription factors
114
Eukaryotes have a requirement for a large variety of accessory proteins to help them carry out the process of transcription. What are these proteins called?
Transcription factors
115
What is the function of the poly(A) tail on most mRNAs?
to prevent premature degradation of the mRNA by exonucleases
116
You have attached synthetic poly(T) to a chromatography column. If you pass a mixture of cellular RNAs through the column, what type of RNA will be selectively retained by the column and of what type of chromatography is this technique an example?
1. mRNAs
| 2. affinity chromatography
117
Why is glucose able to leave the liver cell while glucose-6-phosphate cannot?
The liver cell plasma membrane is permeable to glucose but not glucose-6-phosphate.
118
Is peripheral membrane proteins not made on the RER or typically glycosylated and thus
converted to glycoproteins?
Yes, it is not made on RER but rather on Golgi networks.
119
What organelle is responsible for the glycosylation of proteins and hence the conversion to glycoproteins?
Golgi networks.
120
What type of membrane lipids are made by ER membrane proteins?
Phospholipids.
121
The ER reportedly contains sensors that monitor the concentration of unfolded or misfolded proteins in the lumen. One proposal suggests that the sensors are normally kept in an inactive state by what?
Molecular chaperones.
122
What are the two separate categories of uptake of extracellular materials into cytoplasmic vesicles?
1. phagocytosis
| 2. endocytosis
123
What appears to be the purpose of molecular chaperones like BiP?
They bind to unfolded and misfolded proteins and help them regain their native structure.
124
What is the function of the protein coat on budding vesicles?
1. It acts as a mechanical device that helps to form the vesicle.
2. It provides a mechanism for selecting components and cargo to be carried by each vesicle.
125
Which coated vesicles move materials in an anterograde direction (forward) from the ER to the ERGIC
and the Golgi complex?
COPII-coated vesicles
126
Which coated vesicles move materials in a retrograde direction (backward) from the ERGIC and Golgi stack
toward the ER?
COPI-coated vesicles
127
What are the building blocks of a membrane lipid?
glycerol + 1 phosphate group + 2 fatty acids
128
What kind of membrane protein is found entirely outside the bilayer on either the extracellular or cytoplasmic surface? These proteins are covalently linked to a membrane lipid situated within the bilayer.
lipid-anchored protein
129
What word describes the synthesis and secretion of a substance from the cell in a continual, unregulated manner?
constitutive
130
Along which pathway do materials or the membrane surface move into the cell from the outside to cytoplasmic compartments?
endocytic pathway
131
In general, how are proteins targeted to specific destinations?
1. sorting signals located on the proteins
| 2. receptors in transport vesicle walls that recognize them
132
List the 3 molecular motors.
1. Myosins
2. Dyneins
3. Kinesins
133
What cytoskeleton structure serve as tracks for molecular motors?
1. microtubules
| 2. microfilaments
134
Which molecular motors is associated with microtubules?
1. Dyneins
| 2. Kinesins
135
Which molecular motors is associated with microfilaments?
1. Myosins
136
The specific site on the chromosome at which replication begins is called the _________.
origin
137
The sites where the pair of replicated segments come together and join the non-replicated segments are called?
Replication forks
138
The DNA strand growing toward the replication fork grows ______ in a 5'—>3' direction as the replication fork advances and is called the ________.
1. continuously
| 2. leading stand
139
What may be a further advantage of using RNA primers during initiation of a strand in replication?
Using primers may decrease mistakes, since they are more likely resulted during initiation than elongation and are thus removed when the RNA is replaced.
140
Once the signal that directs a cell to move from G1 to S phase has been generated, what must the
cell do?
The cell completes a round of DNA synthesis and continues through mitosis.
141
Cell entry into M phase is initiated by a two-subunit _________ called ____________.
1. protein kinese, maturation-promoting factor
| 2. phosphorylase, maturation-parturition factor
142
What is the regulatory subunit of maturation-promoting factor called?
cyclin (because its concentration rises and falls predictably as the cell cycle progresses)
143
What are the characteristics of malignant cells?
1. ignore inhibitory growth signals
| 2. continue to grow in the absence of stimulatory growth signals required by normal cells
144
Tumor-suppressor genes act ______ and both copies must be _______ before the protective function is lost.
1. recessively
| 2. mutated/deleted
145
What is an accurate description of the E2F-pRb complex?
The E2F-pRb complex is associated with DNA but acts as a gene repressor.
146
What are the functions of p21?
1. inhibits the cyclin-dependent kinase that normally drives the cell through the G1 checkpoint.
2. allows the cell time to repair genetic damage before DNA replication is initiated
147
Why can't ataxia telangiectasia sufferers respond properly to DNA-damaging radiation?
a. They lack a protein kinase called ATM, which initiates the events that give the cell time to repair damaged DNA.
b. The p53 protein in ataxia telangiectasia patients is phosphorylated less than normal.
c. The p53 protein in ataxia telangiectasia patients is phosphorylated more than normal.
d. The p53 protein is transported to the cytosol by MDM2 and eventually destroyed.
a. They lack a protein kinase called ATM, which initiates the events that give the cell time to repair damaged DNA.
b. The p53 protein in ataxia telangiectasia patients is phosphorylated less than normal.
d. The p53 protein is transported to the cytosol by MDM2 and eventually destroyed.
148
What are GTP-binding proteins also known as?
G proteins
149
Why are G-protein coupled receptors often known as 7TM receptors?
They have 7 transmembrane a-helices.
150
Place the events below in the correct order.
1 – G protein binds to activated receptor forming a receptor-G protein complex
2 – Release of GDP and then the binding of GTP
3 – Change in conformation of the cytoplasmic loops of the receptor
4 – Binding of GTP by the G protein
5 – Increase in the affinity of the receptor for a G protein on the cytoplasmic surface of the membrane.
6 – Binding of a hormone or neurotransmitter to a G-protein coupled receptor
7 – Conformational shift in the a subunit of the G protein
6 – 3 – 5 – 1 – 7 – 2 – 4
151
How are G proteins held at the plasma membrane?
by covalent interactions with lipid chains attached to the alpha- and gamma-subunits
152
Put the following events in the right order.
1. Glycogen synthase is inactivated and phosphorylase kinase is activated.
2. Receptor activates a Gas subunit.
3. Glycogen phosphorylase is activated.
4. Receptor undergoes conformational shift.
5. cAMP binds to the protein kinase A, activating it.
6. Receptor binds glucagon or epinephrine
7. Adenylyl cyclase converts ATP to cAMP that diffuses rapidly into the cytoplasm.
8. Protein kinase A phosphorylates glycogen synthase and phosphorylase kinase.
9. Adenylyl cyclase effector on inner membrane surface is activated.
6 – 4 – 2 – 9 – 7 – 5 – 8 – 1 – 3
153
Place the following steps in the MAP kinase cascade in the proper order.
1 – Raf is phosphorylated by several protein kinases in a process that is likely to involve protein-protein interactions.
2 - MEK phosphorylates and activates a MAP kinase.
3 – The phosphorylated tyrosine residues of the receptor are bound by the Grb2-Sos complex formed in the cytoplasm, recruiting it to the inner surface of the plasma membrane, close to Ras.
4 – Activated Raf, a serine-threonine protein kinase, phosphorylates the protein kinase MEK.
5 – Ras binds to Raf, a signaling protein.
6 – Sos causes Ras to exchange GDP for GTP, activating it.
7 – MAP kinasemoves into the nucleus where it phosphorylates and activates specific transcription factors.
8 – A mitogen binds to its receptor activating the receptor
8 – 3 – 6 – 5 – 1 – 4 – 2 – 7
154
What molecules bind to an inactive monomeric G protein and stimulate the dissociation of bound GDP, which ultimately results in the G protein being activated?
Guanine nucleotide-exchange factors (GEFs)
155
Which molecules accelerate the ability of monomeric G proteins to hydrolyze GTP to GDP, thus
inactivating the G protein?
GTPase-activating proteins (GAPs)
156
What is the effect of GAPs on the G protein-mediated response?
GAPs dramatically shorten the duration of the response.
157
What function as linkers enabling two or more signaling proteins to be joined together as part of a signaling complex? They contain an SH2 domain and one or more additional protein-protein interaction domains.
adaptor proteins
158
At which site do virtually all of the signals that regulate the activities in which a cell is engaged originate?
At cell membrane
159
The overall process in which information carried by extracellular messenger molecules is translated into changes that occur inside the cell is called ___________.
signal transduction
160
If the receptor is degraded along with its ligand after internalization, what is the effect on the cell's ability to respond to a hormone?
The cell has decreased sensitivity to subsequent stimuli.
161
Proteins interact with one another, or with components of the cellular membrane, by means of _________.
1. specific types of interaction domains
| 2. the SH3 domain
162
What allows receptors for extracellular signaling molecules present on the responding cell's surface to recognize such molecules so readily?
They bind the signaling molecules with high affinity.
163
What is the largest protein superfamily encoded by animal genomes?
G-protein coupled receptors
164
The subunits of the heterotrimeric (a macromolecule composed of three subunits of which at least one differs from the other two) G protein are called ___________ subunits.
1. alpha
2. beta
3. gamma
