1
PCB 3023 Exam Questions and Correct
Answers Graded A+
1. cross-linking - ANSWER disulfide bonds form between adjacent cysteine
residues.
they can link two domains of the same polypeptide or different polypeptide chains
2. denaturants - ANSWER can unfold (denature) a polypeptide by breaking
noncovalent interactions between amino acids. (e.g. urea or heat)
3. reducing agents - ANSWER can break disulfide bonds. (e.g. beta-
mercaptoethanol)
4. urea - ANSWER produced in the liver of mammals as a way to excrete
ammonia (a toxic metabolic waste product). can reversibly break
noncovalent interactions between amino acids.
5. fibrillar collagens - ANSWER the major structural proteins of connective
tissues. build of triple helices of procollagen polypeptides.
6. prions - ANSWER proteinaceous infectious particle. infectious agent.
7. protein-only hypothesis - ANSWER diseases are caused by incorrectly
folded versions of the prion protein
8. TSE - ANSWER family of fatal brain diseases characterized by lesions that
appear as small cavities (spongy appearance) caused by protein aggregates
9. Regulation of gene expression - ANSWER determines the amount of protein
produced by the cell by limiting transcription and/or translation
10.regulation of protein function - ANSWER the protein is synthesized but its
activity is restricted according to needs of the cell.
11.What is a Ligand? - ANSWER a molecule that binds to receptrors
12.What is an agonist? - ANSWER A ligand that binds to a receptor to initiate a
response
, 2
13.What is an antagonist? - ANSWER A ligand that binds to a receptor to
prevent a response
14.What are intracellular signaling molecules? Provide an example - ANSWER
Seconds messengers.
ie. cAMP
15.What are effector proteins? What can they do? - ANSWER The target
proteins in a pathway. Can mediate cell responses
16.Signals can act over short range OR long range. T/F? - ANSWER True
17.Where are extracellular signaling molecules secreted? - ANSWER Outside
of the cell. Example: into the bloodstream
18.What is an endocrine cell? Provide an example - ANSWER A cell that
produces long range hormones and secretes them into the blood stream to
affect a target cell.
Example: insulin
19.What is a paracrine cell? Provide two examples - ANSWER A cell that
releases signal molecules that diffuse locally.
Example: Cytokines regulate local inflammation. Growth factors
20.What is an autocrine cell? Provide an example - ANSWER A cell that
depends on its own signaling molecules
Example: cancer cells
21.What are synaptic cells? Provide an example - ANSWER Cells that secrete
neurotransmitters from their axons terminal
22.What is a synapse? - ANSWER the junction of the nerve cell (neuron).
Delivers chemical signal to adjacent neuron
23.What is a contact-dependent cell? Provide an example - ANSWER A cell
that does not depend on secreted signaling molecules. The cell must make
direct physical contact through ligand and receptor, both of which are
located in plasma membrane.
Example: Some signaling in embryonic development.
, 3
24.Some signal molecules (Ligands) can induce different responses in different
target cells by affecting different receptors OR by resulting in different
products T/F? - ANSWER True
25.After acetylcholine is secreted from cells, it is long-lived, because it has to
reach target cells all over body. T/F? - ANSWER False. Acetylcholine
would be short-lived
26.Where are receptors usually located? - ANSWER They can be at the cell
surface (plasma membrane) OR, if the ligand is small and hydrophobic,
within the cell.
27.Describe the steroid hormone cortisol as a ligand. - ANSWER Cortisol is
able to diffuse through the plasma membrane and bind with a nuclear
receptor protein (which later acts a a transcription regulator). It can then
move through a nuclear pore channel and bind to the regulatory region of a
targeted gene, leading to transcription and translation.
28.What response does exposure to extracellular signals in an intracellular
pathway produce? Does this pathway occur fast or slow? - ANSWER
Alteration of free-floating ribosome and protein function. Occurs fast
29.What response does exposure to extracellular signals in an nuclear signaling
pathway produce? Does this pathway occur fast or slow? - ANSWER
Alteration of DNA transcription and eventually mRNA and protein
synthesis. Occurs slowly.
30.Signaling molecules are amplified and integrated by multiple factors. T/F? -
ANSWER True. Primary transduction typically amplifies the signal.
31.What is the key mechanism for molecular on/off switches? Why? -
ANSWER Phosphorylation. Presence of a phosphate may turn a factor on or
off. Common because it is reversible
32.What is phosphorylation? - ANSWER The key mechanism for turning
factors on or off. Reversible
33.Describe a general phosphorylation mechanism - ANSWER If a factor is off,
a signal will prompt a protein kinase to convert ATP to ADP. The lone
, 4
phosphate will bind to that factor and turn it on to produce a secondary
signal. A protein phosphatase will remove the phosphate to turn the factor
off
34.What purpose do GTP binding proteins serve? Provide examples -
ANSWER Participate in signal transduction. Similar purpose as
phosphorylation
35.What proteins control GTP Binding proteins? - ANSWER GEF- Guanine
nucleotide Exchange Factor
GAP- GTPase Activating Protein
36.What does GAP- GTPase Activating Protein do? - ANSWER Inactivate
GTPase by promoting GTP hydrolysis
37.What does GEF- Guanine nucleotide Exchange Factor do? - ANSWER
Activates GTPase by promoting the exchange of GDP for GTP
38.Describe a typical signaling by GTP binding protein mechanism - ANSWER
If a monomeric GTPase is inactive, GEF will prompt the exchange of GDP
for GTP, activating the monomeric GTPase. To inactive the monomeric
GTPase, GAP will remove a phosphate from GTP to yield GDP.
39.Describe a G-Protein Coupled Receptor (GPCR) - ANSWER A polypeptide
chain that traverses the plasma membrane as seven alpha helices. It is where
the signal molecules binds and where the receptor is.
40.How many GPCRs does the human genome encode? Where are the majority
located? - ANSWER >700. ~400 are olfactory
41.GPCRs are often targets for pharmaceuticals. T/F? - ANSWER True
42.Describe G-Proteins - ANSWER Anchored at plasma membrane. Binds to
GPCR. Heterotrimeric (3 different subunits)- alpha, beta, gamma.
43.Describe the Alpha Subunit of G-Proteins - ANSWER Is the GTP binding
subunit. Can bind either GTP OR GDP.
44.How does GPCR activate G-Proteins? - ANSWER By inducing the alpha
subunit to associate with GTP
PCB 3023 Exam Questions and Correct
Answers Graded A+
1. cross-linking - ANSWER disulfide bonds form between adjacent cysteine
residues.
they can link two domains of the same polypeptide or different polypeptide chains
2. denaturants - ANSWER can unfold (denature) a polypeptide by breaking
noncovalent interactions between amino acids. (e.g. urea or heat)
3. reducing agents - ANSWER can break disulfide bonds. (e.g. beta-
mercaptoethanol)
4. urea - ANSWER produced in the liver of mammals as a way to excrete
ammonia (a toxic metabolic waste product). can reversibly break
noncovalent interactions between amino acids.
5. fibrillar collagens - ANSWER the major structural proteins of connective
tissues. build of triple helices of procollagen polypeptides.
6. prions - ANSWER proteinaceous infectious particle. infectious agent.
7. protein-only hypothesis - ANSWER diseases are caused by incorrectly
folded versions of the prion protein
8. TSE - ANSWER family of fatal brain diseases characterized by lesions that
appear as small cavities (spongy appearance) caused by protein aggregates
9. Regulation of gene expression - ANSWER determines the amount of protein
produced by the cell by limiting transcription and/or translation
10.regulation of protein function - ANSWER the protein is synthesized but its
activity is restricted according to needs of the cell.
11.What is a Ligand? - ANSWER a molecule that binds to receptrors
12.What is an agonist? - ANSWER A ligand that binds to a receptor to initiate a
response
, 2
13.What is an antagonist? - ANSWER A ligand that binds to a receptor to
prevent a response
14.What are intracellular signaling molecules? Provide an example - ANSWER
Seconds messengers.
ie. cAMP
15.What are effector proteins? What can they do? - ANSWER The target
proteins in a pathway. Can mediate cell responses
16.Signals can act over short range OR long range. T/F? - ANSWER True
17.Where are extracellular signaling molecules secreted? - ANSWER Outside
of the cell. Example: into the bloodstream
18.What is an endocrine cell? Provide an example - ANSWER A cell that
produces long range hormones and secretes them into the blood stream to
affect a target cell.
Example: insulin
19.What is a paracrine cell? Provide two examples - ANSWER A cell that
releases signal molecules that diffuse locally.
Example: Cytokines regulate local inflammation. Growth factors
20.What is an autocrine cell? Provide an example - ANSWER A cell that
depends on its own signaling molecules
Example: cancer cells
21.What are synaptic cells? Provide an example - ANSWER Cells that secrete
neurotransmitters from their axons terminal
22.What is a synapse? - ANSWER the junction of the nerve cell (neuron).
Delivers chemical signal to adjacent neuron
23.What is a contact-dependent cell? Provide an example - ANSWER A cell
that does not depend on secreted signaling molecules. The cell must make
direct physical contact through ligand and receptor, both of which are
located in plasma membrane.
Example: Some signaling in embryonic development.
, 3
24.Some signal molecules (Ligands) can induce different responses in different
target cells by affecting different receptors OR by resulting in different
products T/F? - ANSWER True
25.After acetylcholine is secreted from cells, it is long-lived, because it has to
reach target cells all over body. T/F? - ANSWER False. Acetylcholine
would be short-lived
26.Where are receptors usually located? - ANSWER They can be at the cell
surface (plasma membrane) OR, if the ligand is small and hydrophobic,
within the cell.
27.Describe the steroid hormone cortisol as a ligand. - ANSWER Cortisol is
able to diffuse through the plasma membrane and bind with a nuclear
receptor protein (which later acts a a transcription regulator). It can then
move through a nuclear pore channel and bind to the regulatory region of a
targeted gene, leading to transcription and translation.
28.What response does exposure to extracellular signals in an intracellular
pathway produce? Does this pathway occur fast or slow? - ANSWER
Alteration of free-floating ribosome and protein function. Occurs fast
29.What response does exposure to extracellular signals in an nuclear signaling
pathway produce? Does this pathway occur fast or slow? - ANSWER
Alteration of DNA transcription and eventually mRNA and protein
synthesis. Occurs slowly.
30.Signaling molecules are amplified and integrated by multiple factors. T/F? -
ANSWER True. Primary transduction typically amplifies the signal.
31.What is the key mechanism for molecular on/off switches? Why? -
ANSWER Phosphorylation. Presence of a phosphate may turn a factor on or
off. Common because it is reversible
32.What is phosphorylation? - ANSWER The key mechanism for turning
factors on or off. Reversible
33.Describe a general phosphorylation mechanism - ANSWER If a factor is off,
a signal will prompt a protein kinase to convert ATP to ADP. The lone
, 4
phosphate will bind to that factor and turn it on to produce a secondary
signal. A protein phosphatase will remove the phosphate to turn the factor
off
34.What purpose do GTP binding proteins serve? Provide examples -
ANSWER Participate in signal transduction. Similar purpose as
phosphorylation
35.What proteins control GTP Binding proteins? - ANSWER GEF- Guanine
nucleotide Exchange Factor
GAP- GTPase Activating Protein
36.What does GAP- GTPase Activating Protein do? - ANSWER Inactivate
GTPase by promoting GTP hydrolysis
37.What does GEF- Guanine nucleotide Exchange Factor do? - ANSWER
Activates GTPase by promoting the exchange of GDP for GTP
38.Describe a typical signaling by GTP binding protein mechanism - ANSWER
If a monomeric GTPase is inactive, GEF will prompt the exchange of GDP
for GTP, activating the monomeric GTPase. To inactive the monomeric
GTPase, GAP will remove a phosphate from GTP to yield GDP.
39.Describe a G-Protein Coupled Receptor (GPCR) - ANSWER A polypeptide
chain that traverses the plasma membrane as seven alpha helices. It is where
the signal molecules binds and where the receptor is.
40.How many GPCRs does the human genome encode? Where are the majority
located? - ANSWER >700. ~400 are olfactory
41.GPCRs are often targets for pharmaceuticals. T/F? - ANSWER True
42.Describe G-Proteins - ANSWER Anchored at plasma membrane. Binds to
GPCR. Heterotrimeric (3 different subunits)- alpha, beta, gamma.
43.Describe the Alpha Subunit of G-Proteins - ANSWER Is the GTP binding
subunit. Can bind either GTP OR GDP.
44.How does GPCR activate G-Proteins? - ANSWER By inducing the alpha
subunit to associate with GTP
