Cell Signalling ✅

Question 1

What are the two basic types of cell communication? What is another word for cell communication?

Answer 1

The two basic types of physiological signals (messengers) are:
1) electrical signals
2) chemical signals

Question 2

How do cells have electrical signals? What changes for them to occur?

Answer 2

Electrical signals are changes in a cell’s membrane potential.

Question 3

How do cells have chemical signals? What changes for them to occur?

Answer 3

• cells secrete molecules into the extracellular fluid

Question 4

What are the cells called that receive electrical and chemical signals?

Answer 4

target cells

Question 5

Which form of communication is most frequent?

Answer 5

chemical communication

Question 6

What are the three basic methods of cell-to-cell communication?

Answer 6

1. DIRECT CYTOPLASMIC TRANSFER - electrical and chemical signals through gap junctions that connect adjacent cells.
2. LOCAL COMMUNICATION- by chemicals that diffuse through the extracellular fluid.
3. LONG-DISTANCE COMMUNICATION- through a combination of electrical signals carried by nerve cells and chemical signals transported in the blood.

Question 7

Explain direct cytoplasmic transfer.

Answer 7

DIRECT CYTOPLASMIC TRANSFER of electrical and chemical signals through gap junctions that connect adjacent cells.

Question 8

Explain local communication.

Answer 8

LOCAL COMMUNICATION by chemicals that diffuse through the extracellular fluid.

Question 9

Explain long-distance communication.

Answer 9

LONG-DISTANCE COMMUNICATION through a combination of:
- electrical signals carried by nerve cells
- chemical signals transported in the blood.

Question 10

What is a gap junction? What does it form? Which type of signal passes through them?

Answer 10

• A gap junction is a cytoplasmic connection between adjacent cells
  (Protein channels create cytoplasmic bridges between the cells)

When gap junctions are open, ions and small molecules (eg. amino acids, ATP, AMP) pass directly from one cell’s cytoplasm to the next.

• Gap junctions are the only means by which electrical signals can pass directly from cell to cell,

Question 11

What happens when channels open in the gap junction?

Answer 11

the connected cells function like a single cell with multiple nuclei.

Question 12

How do chemical signals distribute?

Answer 12

by diffusion through the interstitial fluid.

Question 13

How is local communication accomplished?

Answer 13

By the diffusion of paracrines and autocrines.

Question 14

What is a paracrine?

Answer 14

A chemical that is secreted by a cell to act on cells very near it.-
- acts short-distance
- on neighbouring cells

Question 15

What is an autocrine?

Answer 15

A signal molecule that acts on the cell that secreted it.
- cell creates a hormone which later acts on itself

Question 16

Why is the effective range of a chemical signal restricted to adjacent cells?

Answer 16

Because distance is a limiting factor for diffusion.

Question 17

How does the nervous system communicate?

Answer 17

Through chemical and electrical signals.

Question 18

How does the endocrine system communicate?

Answer 18

Through hormones.

Question 19

Explain the long-distance communication endocrine system.

Answer 19

• Hormones are secreted by endocrine glands or cells into the blood (and distributed all around the body).
• Only target cells with receptor for the specific hormone will respond to the signal.

Question 20

What type of signal is for hormones? (specific or non-specific)?

Answer 20

SPECIFIC.

Question 21

Explain the long-distance communication nervous system.

Answer 21

• the electrical signal travels along a neuron until it reaches the end of a cell
• the neuron then releases chemical signals (NEUROTRANSMITTER) that diffuse across the synapse to the target cell.

Question 22

What are the “chemicals” of the nervous system?

Answer 22

neurotransmitters

Question 23

What is the synapse?

Answer 23

A small junction between two neurons, or a neuron and a tissue.

Question 24

Explain the key steps of a signal pathway.

Answer 24

1. RECEPTION (of the extracellular signal by the cell)
2. TRANSDUCTION (of a signal from the outside of a cell to the inside of the cell (often multi-stepped))
3. CELLULAR RESPONSE (is initiated and it occurs entirely within the receiving cell).

Question 25

Why do cells not respond to every signal that reaches them?

Answer 25

The signal molecule only recognises the target cell due to its specific receptors. A cell cannot respond to a chemical if it lack the receptors for that signal.

Question 26

What are all receptors?

Answer 26

proteins

Question 27

What are most signal molecules?

Answer 27

water-soluble and too large to pass through the plasma membrane.

Question 28

How many molecules at a time can one receptor bind to?

Answer 28

one! (1)

Question 29

What does binding of a molecule do to its receptor?

Answer 29

changes its shape

Question 30

What is the specific region called at which the signal molecule joins?

Answer 30

the binding site

Question 31

What are molecules that bind specifically to receptors called?

Answer 31

ligands

Question 32

What is a ligand?

Answer 32

A molecule that binds specifically to a receptor.

Question 33

What type of messenger is a ligand?

Answer 33

the FIRST messenger, as it brings information to the target cell.

Question 34

What is an agonist?

Answer 34

- has an active site of similar shape to the endogenous ligand - binds to the receptor and produces the same effect

Question 35

What else circulates in the blood that is not a ligand?

Answer 35

agonists and antagonists

Question 36

What is an antagonist?

Answer 36

- similar shape of the active site to the ligand - cannot perform the reaction: takes up space and the the endogenous ligand from attaching --> inhibits the reaction from taking place

Question 37

What is an intracellular receptor? Where is it located?

Answer 37

- a receptor for lipid-soluble hormones - located in the cytosol or nucleus

Question 38

What is a membrane receptor? Where is it located?

Answer 38

- a receptor for water-soluble hormones - located on the cell membrane

Question 39

What are the three steps of transferring information mediated by water-soluble substances?

Answer 39

1. FIRST MESSENGER (ligand) recognises the receptor in the target cell membrane 2. LIGAND-RECEPTOR COMPLEX activates a signal transduction system in the membrane. an intercellular signal molecule is released (second messenger). 3. The second messenger TRIGGERS A SEQUENCE OF INTRACELLULAR PROCESSES, resulting in increasing or decreasing protein functions.

Question 40

What are the three parts of membrane receptors?

Answer 40

1) AN EXTRACELLULAR PART (protrudes from the membrane and comprises the binding site for the ligand) 2) A TRANSMEMBRANE PART (consists of one or more segments that transverse the membrane and help to activate the signal transduction system) 3) AN INTRACELLULAR PART (extends into the cytosol and is involved in the activation of the signal transduction system)

Question 41

What are the major classes of membrane receptors?

Answer 41

- ion-channel receptor - 7-helix membrane receptor - enzyme-linked receptors

Question 42

What does the intracellular domain have sometimes?

Answer 42

- an enzyme or enzyme-linked receptor.

Question 43

Why are G-protein receptor systems important?

Answer 43

- they are diverse in their function play an important role in: - embryonic development - sensory systems

Question 44

What interferes with G-function proteins?

Answer 44

several diseases

Question 45

Who discovered G-proteins, and their role in the signal transduction pathway?

Answer 45

Alfred G. Gilman and Martin Rodbell.

Question 46

How is signal amplification achieved?

Answer 46

One extracellular ligand binds to a membrane receptor and initiates a signal cascade. - one ligand is amplified into many second messengers (intracellular signal molecules).

Question 47

What are the steps of a cascade reaction?

Answer 47

1) Initial STIMULUS activated the first step in the cascade. 2) In each step the activated molecule from the previous step converts an inactive molecule into an active one. 3) The final step is the CONVERSION of a SUBSTRATE into a PRODUCT.

Question 48

How many responses can result from the reception of a single ligand?

Answer 48

MORE THAN ONE. (1+)