Chapter 7 Cell Communication and Multicellularity

Question 1

Signal transduction pathway

Answer 1

A sequence of molecular events and chemical reactions that lead to a cell’s response to a signal

Question 2

A signal transduction pathway includes

Answer 2

A signal, a receptor and a response

Question 3

In multicellular organisms, chemical signals are often made in one part of the body and arrive at target cells by (3 ways

Answer 3

Local diffusion
Circulation im the blood
Plant vascular system

Question 4

Autocrine signals

Answer 4

Diffuse to and affect the cells that make them

e.g, tumor cells

Question 5

Juxtacrine signals

Answer 5

Affect only cells right next to and in contact with the cell producing the signal

Question 6

Paracrine signals

Answer 6

Diffuse to and affect nearby cells
e.g, histamine, (inflammation when the skin is cut, signals from skin cells are sent to nearby blood cells to aid in healing

Question 7

Hormones

Answer 7

Signals that travel through the circulatory systems of animals or vascular systems of plants are generally called hormones
(Hormones are chemical signals that act on distant cells

Question 8

Crosstalk

Answer 8

Interactions between different signal transduction pathways

Question 9

Ligand

Answer 9

A specific chemical signal molecule that fits into a 3D site on its protein receptor

Question 10

Binding of the signaling ligand causes

Answer 10

The receptor to change its 3D shape, and that conformational change initiates a cellular response (ligand contributes no further

Question 11

The binding is reversible because

Answer 11

Receptors bind to ligands according to chemistry’s law of mass action

Question 12

Why is reversibility important

Answer 12

Otherwise the receptor would be continuously stimulated and the cell will never stop responding

Question 13

Dissociation constant is a measure of

Answer 13

The affinity of the receptor for its ligand

Low Kd, high affinity, bind to ligands at low ligand conc.

Question 14

The change in receptor’s shape may expose

Answer 14

A previously hidden group of amino acids on the protein that participates in a biochemical activity

Question 15

Membrane receptors

Answer 15

Large or polar ligands cannot cross the lipid bilayer
e.g, insulin
Binds to a transmembrane receptor with an extracellular binding domain

Question 16

Intracellular receptors

Answer 16

Small or nonpolar ligand can diffuse across the nonpolar phospholipid bilayer of the cell membrane and enter cell
e.g, the hormone estrogen

Question 17

3 types of cell membrane receptors

Answer 17

Ion channels
Protein kinase receptors
G protein-coupled receptors

Question 18

Ion channels

Answer 18

e.g, acetylcholine (Na+)

Question 20

Protein kinase receptor

Answer 20

e.g, insulin

Insulin is a hormone made by pancreas

Question 21

Adding phosphate

Answer 21

Phosphorylation (v important in biology

Question 22

G protein-coupled receptors

7-transmembrane domain receptors

Answer 22

Many roles including light detection
Detection of odors
Regulation of mood and behavior
e.g, oxytocin, vasopressin

Question 23

Many G proteins have 3 polypeptide subunits and can bind three different types of molecules:

Answer 23

The receptor
GDP and GTP (guanosine diphosphate and triphosphate)
An effector protein

Question 24

Effector protein:

Answer 24

Causes an effect in the cell

Question 25

Intracellular receptors are located

Answer 25

In the cytoplasm of the nucleus

Question 26

Intracellular receptors respond to

Answer 26

Physical signals such as light

Chemical signals that can diffuse across cell membrane (e.g, steroid hormones

Question 27

Many intracellular receptors are transcription factors

Answer 27

After binding to their ligands, these transcription factors move to the nucleus and bind to DNA and alter expression for specific genes

Question 28

Another group of intracellular receptors is always in to nucleus

Answer 28

Ligands must enter nucleus to bind

Question 29

Second messenger

Answer 29

Can amplify signals between receptors and target molecules

Question 30

The balance between the activities of enzymes that activate and inactivate transducers determines the ultimate cellular response to a signal. Cells can alter this balance by

Answer 30

Synthesis or breakdown of the enzymes

Activation or inhibition of the enzymes by other molecules