Lec 04

Question 1

Physiological signals

Answer 1

-Electrical signals
Changes membrane potential
-Chemical signals
Molecules secreted by cells into ECF
Bind to specific receptor on or in target cells

Question 2

Communication method between cells

Answer 2

1- Local(gap junction, autocrine(myself), paracrine(neighbor))
2- Long distance (neuronal, endocrine)

Question 3

Autocrine and Paracrine examples

Answer 3

Hormones
Neurotransmitter

Question 4

Hormone are secreted by endocrine into —

Answer 4

Blood. Only target cells with receptors for the hormone will respond

Question 5

Endocrine hormone example

Answer 5

Insulin secreted from pancreatic betta cells and binds to insulin receptors throughout body enable glucose enter these cells

Question 6

Neurotransmitters

Answer 6

-Long distance
-Secreted by neurons that Diffuse across a small gap to the target cell

Question 7

Neurotransmitter example

Answer 7

Acetylcholine that elicit skeletal muscle contraction

Question 8

Neurohormones

Answer 8

Chemicals released by neurons into blood for action at distant targets

Question 9

Neurohormones examples

Answer 9

Oxytocin is released by posterior pituitary gland into blood and stimulates (Uterus smooth muscles) uterine contractions during labor

Question 10

Major classes of chemical signals

Answer 10

Amino acids — glutamate, glycine
Amines — epinephrine, norepinephrine, dopamine
Peptides — insulin, glucagon
Steroids — derived from cholesterol, estrogen

Question 11

Receptor Location

Answer 11

Intracellular signal receptors:
— receptor in cytosol or nucleus
— SLOWER RESPONSE
Extracellular signal receptor:
— cell membrane receptor
— RAPID CELLULAR RESPONSE

Question 12

Membrane receptors categorize

Answer 12

1- channels
2- Enzyme(receptor)
—— insulin
3- G protein (receptor)
4- Anchor protein (integrin)
—— adherents junctions

Question 13

Signal transduction

Answer 13

1- Signal molecule (hormone/neurotransmitter) binds to membrane receptors proteins
2- Which activates intracellular signal molecules
3- which alter target protein
4- create response

Question 14

Signal transduction

Answer 14

1-Signal molecule bind to membrane receptor
2- Initiate signal transduction by proteins
3- amplifier enzymes produce second messenger molecules
**4.1- protein kinases or phosphatases
**4.2- increase intracellular ca ion
***4.3- MAYBE alter ion channels
5- cell response

Question 15

Kinases

Answer 15

Phosphorylate protein

Question 16

Phosphatases

Answer 16

Dephosphorylated proteins

Question 17

Signal amplification two key factors

Answer 17

1- volume
2- sensitivity

Question 18

Cascade

Answer 18

Tightly regulated to not accidentally turn on safety

Question 19

Enzyme-linked receptors

Answer 19

Ligands binds to receptor, which activates associated enzyme
Ex. Insulin receptors

Question 20

G protein coupled receptors

Answer 20

-Ligand binds to receptor that is physically coupled to a Guanosine nucleotide-binding (G) protein
-Largest family of cell surface receptor
-G protein made up three subunits: alpha, betta, gamma
-After activation they may:
—— directly alter ion channel
——alter activity of another enzyme
-Type of G protein will determine which intracellular cascade is initiated

Question 21

GS

Answer 21

GPCR—adenylyl cyclase—produce cyclic cAMP shows us —activates protein kinase A—phosphorylated protein—cell response

Question 22

GI

Answer 22

GPCR—GI(inhibitory)—inhibit Adenylyl cyclase—cyclic cAMP level decrease—kinase activity fall

Question 23

Gq

Answer 23

Gq activates phospholipase C—(break triphospholipid)—IP3 (O-head) AND DAG (tail)—DAG activates PKC (protein kinase c) that will phosphorylated proteins— IP3 will open ligand-gated ca ion channels in ER

Question 24

Gq

Answer 24

1- Signal molecule activates receptor and associated G protein.
2- G protein activates phospholipase C (PLC), an amplifier enzyme.
3- PLC converts membrane phospho- lipids into diacylglycerol (DAG), which remains in the membrane, and IP3, which diffuses into the cytoplasm.
4- DAG activates protein kinase C (PKC), which phosphorylates proteins.
5- IP3 causes release of Ca2+ from organelles, creating a Ca2+ signal.

Question 25

Ligand-gated channel

Answer 25

Ligand binds to its receptor. Receptor is ion channel that is gated by ligand binding

Question 26

Ion channels can be activated during gpcr by ——

Answer 26

Camp,Ca ion,G protein
Indirect gating
Slower change

Question 27

Ca ion can enter the cell via

Answer 27

1- voltage-gated channel
2- ligand-gated channel
3- mechanically-gated channel
4- released from stores by secondary messengers

Question 28

When Ca ion conc. in cytosol Increase

Answer 28

Ca ion binds to protein:
Calmodulin — alter protein activity
Other proteins — Exocytosis/movement