Signal Transduction

Question 1

Contact-dependent signaling molecules

Answer 1

Membrane bound signal molecule does not leave the cell and not secreted
Binds to the receptor of the target cell
Immune response

Question 2

Synaptic signaling molecule

Answer 2

Can transmit signal in milliseconds to considerable distances (1)
Electrical signals cause the release of neurotransmitters that act on the target cells

Question 3

Paracrine signaling molecules

Answer 3

Signaling molecule that secretes and acts on nearby cells
Important in inflammation

Question 4

Endocrine signaling molecules

Answer 4

Signals through blood stream and acts on target cells
Long distances

Question 5

How long does epinephrine-mediated heart stimulation take?.

Answer 5

Within seconds to minutes

Question 6

How long does growth-factor mediated cell growth in cell division take?

Answer 6

Hours because it requires expression and synthesis of new proteins

Question 7

What activates a simple intracellular signaling pathway?

Answer 7

An extracellular signal molecule

Question 8

Simple intercellular signaling pathway

Answer 8

① reception (specific) → signal binds to receptors
② transduction → signals bind to various proteins in the cell
③response → proteins respond

Question 9

Messengers of the cell

Answer 9

① first messengers (extracellular → hormones, Gfs, Environmental stimuli)
② second messengers (intracellular → cAMP, cGMP,DAG, IP3
③ effector proteins (cellular and biological responses)

Question 10

Signals

Answer 10

Proteins
Peptides
Steroids
Amino acids
Light
Fatty acid derivatives
Odor/scent
Sound
Gases

Question 11

Cell surface receptors

Answer 11

Signaling molecules - water soluble
Receptor location: cell membrane
Ex: G-protein coupled receptor, ion-channel coupled receptor, enzyme-coupled receptors or enzymes with intrinsic activity

Question 12

Intracellular receptors

Answer 12

Signal molecule lipophilic (hydrophobic) molecules that can diffuse Across the plasma membrane
Receptor location: cytoplasm or nuclear
Ex: receptors for steroid hormones such as estrogen, progesterone, corticosteroids

Question 13

Intracellular signaling proteins

Answer 13

Molecular switches
Enhance speed efficiency, a specificity of the response
Activated by phosphorylation or GTP binding

Question 14

Kinases function

Answer 14

Add phosphate groups to proteins that alters the activity, stability and location of the protein

Question 15

Phosphatases function

Answer 15

Remove phosphate group

Question 16

GTP - binding proteins

Answer 16

Biochemical switches
Inactive when bound to GDP and active when bound to GTP

Question 17

Second messengers

Answer 17

Small intracellular nonprotein molecules that regulate the activity of enzymatic and non-enzymatic proteins
Can bind and alter conformation and behavior of selected signaling proteins

Question 18

Examples of water soluble second messengers that diffuse in cytosol

Answer 18

cAMP
cGMP
and Ca2+

Question 19

What is an example of a lipid soluble second messenger that diffused into plasma membrane?

Answer 19

DAG (diacyglycerol)

Question 20

What are the 4 categories of receptors?

Answer 20

1) GPCRs
2) Ion-channel- coupled receptors
3) Receptors with enzymatic activity
4) Nuclear Receptors

Question 21

What are the largest class of cell surface receptors?

Answer 21

G-protein couple receptors (GPCRs)

Question 22

G-protein coupled receptors (GPCRs)

Answer 22

Span the plasma membrane 7 times
More than 800 GPCRs in human
Hormones, neurotransmitters, sight, smell and taste use them
50% of modern drugs target them

Question 23

Guanine Nucleotide Binding Proteins (G Proteins)

Answer 23

A inactive complex of Ga and Gbg

Question 24

Ga in the inactive complex

Answer 24

Bound to GDP

Question 25

What does the activation of G-proteins cause?

Answer 25

Dissociated of the Ga and Gbg complex
GDP is switched with GTP

Question 26

When can G-proteins have intrinsic GTPase activity?

Answer 26

When ‘on’ state and shut themselves off by hydrating their bound GTP to GDP

Question 27

Ligand-induced activation of effector protein that’s associated with G protein coupled receptors

Answer 27

1. Binding of hormone induces a conformational changed in receptor
2. Activated receptor binds to Ga subunit
3. Binding induces conformational change in Ga; bound GDP disassociates and is replaced by GTP; Ga dissociates from Gbg
4. Hormone dissociates from receptor; Ga binds to effector activating it
5. Hydrolysis of GTP to GDP causes Ga to dissociate from effetcor and reassociate with Gbg

Question 28

Adenylate cyclase

Answer 28

Catalyzes the conversion of ATP to cAMP

Question 29

What does Cyclic AMP dependent protein kinase (PKA) mediate most?

Answer 29

The effects of cyclic AMP

Question 30

PKA

Answer 30

Serine/Threonine Kinase
2 catalytic subunits and 2 regulatory subunits
cAMP binds to regulatory subunits and causing them to dissociate
Released subunits activate to phosphorylate specific target proteins

Question 31

How does epinephrine stimulate heart rate?

Answer 31

Rapidly, releasing the proteins already existing
1) It activates G proteins
2) Ga binds to it and activated adenylate cyclase
3) cAMP increases
4) PKA activates
5) intracellular calcium increases and activates contractile and regulatory proteins
6) rate and force of contraction increases

Question 32

Vasopressin action

Answer 32

Binds and stimulates GPCR resulting in the translocation of a water channel to the membrane in the collecting duct cells of the kidney