Biochemistry Quiz 5

Question 1

What is signal transduction?

Answer 1

cells receive signals from the outside and it is transduced into the inside
-leads to action such as: gene expression, membrane transport, metabolism, cell growth/death
INFORMATION FROM THE ENVIRONMENT TRANSMITTED INSIDE A CELL GENERATES A CELLULAR RESPONSE

Question 2

What is the signal transduction cascade? (3 steps)

Answer 2

3 steps
1. reception
2. transduction
3. response
-often use amplification

Question 3

What are the modes of cell-cell communication?

Answer 3

Juxtacrine signaling (two proteins bind)
Endocrine signaling (hormones secreted into bloodstream; high affinity receptor)
Paracrine signaling (secreted ligands target nearby cells; low affinity receptor)
Synaptic signaling (synapse between neuron and target is short distance; very low affinity receptor)
autocrine signaling (sender and target in same cell; fast response)

Question 4

What is an intracellular receptor?

Answer 4

intracellular receptor
-for steroid hormones (endocrine signaling), thyroid hormone, vitamins
ex. hormonal nuclear receptor (changed cell function); thyroid nuclear receptor (signaling effect is transcription)

Question 5

What is an integral membrane protein?

Answer 5

-embedded in the biological membrane (can be a transmembrane protein)
-leads to activation of effector & other intracellular enzymes
-can also lead to altering receptor activity or changing membrane potential

Question 6

What are the 4 types of cell-surface receptors?

Answer 6

-ligand-gated ion channel receptors
-enzyme-linked or catalytic receptors
-cytokine family receptors
-G-protein-coupled receptors

Question 7

What occurs during first messenger binding?

Answer 7

-generates second messengers
-change plasma membrane potential
-effector/enzyme cascade activation (direct interaction or coupling/transducing proteins)

Question 8

What are second messengers?

Answer 8

-intracellular molecules that transmit and amplify initial signal from the first messenger
ex. ions, cAMP, IP3, DAG, PIP3

Question 9

How is signaling controlled downstream?

Answer 9

-protein phosphorylation (induces conformational changes to increase/decrease enzyme activity; promote/disrupt protein-protein interaction)
-GTP-binding regulatory proteins (constitute a molecular switch between OFF/On states of a signal)

Question 10

What methods allow turning off cell surface receptors to terminate signaling?

Answer 10

-by rapidly reducing the level of message or agonist availability
-receptor loss or desensitization (biological response to a drug diminishes when it is given continuously or repeatedly)

Question 11

describe Ligand-gated ion channels

Answer 11

-transmembrane ion channels
-involved in neuronal signaling
-extracellular and transmembrane domains
ex. serotonin, GABA, glycine, glutamate, nicotinic acetylcholine

Question 12

describe a type of enzyme-linked receptor

Answer 12

-receptor tyrosine kinases
-induces dimerization of whole receptor activating intracellular catalytic activity
-participates in autophosphorylation then sequential phosphorylation
ex. insulin receptor, growth factor receptors

Question 13

What is a receptor Tyrosine Kinase example?

Answer 13

-activates Ras/ MAP kinase signal cascade
-Ras-activating protein is a GEF (guanine nucleotide exchange factor)

Question 14

What is a GEF?

Answer 14

family of proteins that facilitate the release of GDP from the small G-Protein

Question 15

What is Ras?

Answer 15

-membrane bound, monomeric G protein
-cell proliferation, differentiation, adhesion, migration and apoptosis, division
-associated with many cancers

Question 16

What are G-protein-coupled receptors?

Answer 16

-most common target for pharmaceuticals
-hormone and neurotransmitter receptors
-transduce extracellular signals into intracellular responses