Chapter 6

Question 1

Why do cells communicate?

Answer 1

To stay alive and functioning
To self-destruct
To undergo cell division for growth or repair
To differentiate into a particular cell type
To eliminate a pathogen that has invaded the body
To activate a gene and produce the specific protein encoded by that gene
To silence a gene
To produce an enzyme or a structural protein

Question 2

Homeostasis

Answer 2

The maintenance of a relatively stable internal environment within narrow limits

Question 3

Interstitial fluid

Answer 3

Fluid found on the outside of cells; extracellular

Question 4

Types of signaling molecules

Answer 4

Animal hormones, plant hormones, neurohormones, cytokines, neurotransmitters, pheromones, glucose and ions

Question 5

Animal hormones

Answer 5

Steriods/fatty acids or peptides
Usually produced in endocrine glands or some neurons
Travel via blood or extracellular fluid

Question 6

Neurohormone

Answer 6

Fatty acids/steroids or peptides
Usually produced by neurons of hypothalamus
Travel in blood or extracellular fluid

Question 7

Neurotransmitters

Answer 7

Peptides or modified amino acids
Produced in neurons and stored in synaptic vesicles
Travel across synaptic gaps

Question 8

Cytokines

Answer 8

Mostly peptides, some proteins and glycoproteins
Mainly immune cells of mammals but also others
Travel via blood, lymphatic system or extracellular fluid
Target other immune cells

Question 9

Pheromones

Answer 9

Simple modified hydrocarbons or other more complex molecules
Produced in exocrine glands
Secreted into external environment
Targets other members of the same species

Question 10

Plant hormones

Answer 10

Simple to complex organic molecules
Produced in specialized cells in a variety of plant tissues
Travel via plant’s vascular tissue-ethylene diffuses through intracellular spaces

Question 11

Long distance travel to target cells

Answer 11

Hormones secreted by various endocrine glands travel via the circulatory system over long distance to reach their target cells

Question 12

Travel to nearby cell

Answer 12

Chemical signals diffuse through the extracellular fluid to reach their target cell

Question 13

Cell to cell contact

Answer 13

Signaling molecules move directly from the cytosol of one cell to another
Gap junctions in animal tissues are protein-lined pores; enable small molecules and electrical signals to pass
Plasmodesmata in plant tissues; gaps in the cell wall, plasma membrane is continuous

Question 14

Reception

Answer 14

Signaling molecules bind with their specific receptor and causes change in the receptor’s 3D shape

Question 15

Transduction

Answer 15

A change in the 3D shape of the receptor molecule causes a signal pathway in which a series of steps are triggered

Question 16

Response

Answer 16

The transduction brings about the cell’s response

Question 17

Stimulus response model

Answer 17

Stimulus
Receptor
Signal
Effector
Response

Question 18

Transduction of a Hydrophobic Signal

Answer 18

The binding of the steroid hormone to it’s specific receptor produces a change in the 3D shape of the receptor protein, exposing a region of the receptor that was previously within the molecule
The hormone-receptor complex moves from the cytoplasm into the nucleus
The exposed segment of the receptor protein attaches to a target DNA sequence next to certain genes and activates those genes

Question 19

Secondary messengers

Answer 19

Small molecules which activate a key enzyme at the start of an enzyme relay