ANAT242 Lecture 2 - Cellular Regulation

Question 1

what is a ligand?

Answer 1

the chemical nature of a signal molecule

Question 2

what are 6 examples of ligands?

Answer 2

proteins
amino acids
steroids
peptides 
amines 
gases

Question 3

what determines how a ligand works?

Answer 3

whether it is water-soluble or lipid-soluble

Question 4

where are water-soluble signals stored?

Answer 4

water-soluble signals are stored within phospholipid vesicles within the signalling cell

Question 5

what composes water-soluble molecules?

Answer 5

water-soluble signals

Question 6

what is exocytosis?

Answer 6

active transport where molecules are secreted out of the cell

Question 7

how are water-soluble molecules transported in the blood and enter the target cell?

Answer 7

water-soluble molecules are carried in the blood bound to a carrier but cannot enter the target cell therefore the message must be transduced through the cell surface receptors

Question 8

are lipid-soluble molecules made on-demand or not and why?

Answer 8

lipid-soluble signals cannot be stored in lipid vesicles as they would leak out of the cell therefore they are made on command

Question 9

what is an advantage and disadvantage of lipid-soluble molecules being produced on command?

Answer 9

production on command is a slower response however the response is long-lasting as it travels the blood bound to a carrier protein and can enter the target cell

Question 10

what is the relationship between a lipid-soluble molecule and the target cell?

Answer 10

lipid-soluble molecules can enter the target cell directly and act on intracellular receptors to directly regulate gene expression

Question 11

what is the function of a carrier protein?

Answer 11

to provide protection for molecules to prevent them from being broken down by enzymes

Question 12

what are the 4 major forms of signalling between cells?

Answer 12

juxtacrine
autocrine
paracrine
endocrine

Question 13

what is juxtacrine cell signalling?

Answer 13

involves direct cell to cell contact of the same cell and is mediated by gap junctions

Question 14

what are gap junctions?

Answer 14

bi-directional channels made up of proteins called connexins that allow the transport of ions and small molecules between cells for rapid communication between cells like cardiac muscle cells or groups of neurons

Question 15

what is autocrine signalling?

Answer 15

involves signalling between nearby cells of the same type and requires the release of a chemical message as one cell signals to many other cells of the same type

Question 16

when is autocrine cells signalling used?

Answer 16

used to coordinate activity between a group of similar cells

Question 17

what is paracrine cell signalling?

Answer 17

used for local signalling between different cell types and requires the release and detection of a chemical message

Question 18

what is an example of paracrine signalling?

Answer 18

endothelial cells communicate with nearby vascular smooth muscle via nitric oxide to regulate blood pressure

Question 19

what is endocrine cell signalling?

Answer 19

involves the signalling between distant cells in the body through chemical signals called hormones which are transported in the blood

Question 20

where are the hormones used in endocrine cell signalling produced?

Answer 20

produced in discrete endocrine glands, tissues and isolated cells

Question 21

how is specificity achieved in juxtacrine cell signalling?

Answer 21

achieved by receptor expression and direct contact. The signalling between adjacent cells involves gap junctions or receptors but unlike other forms of the receptor-mediated cell to cell communication the signalling message is not released

Question 22

what is the notch pathway?

Answer 22

delivers more complex information to the target cell compared to gap junctions and is involved in the development and cancer

Question 23

how is endocrine specificity achieved?

Answer 23

achieved by receptor expression being limited to only target cells

Question 24

how is neuronal specificity achieved?

Answer 24

achieved by precise contacts of rapid removal of neurotransmitters to prevent unwanted diffusion

Question 25

how is autocrine specificity achieved?

Answer 25

achieved by receptor expression and rapid ligand degradation. The signals do not travel as they are broken down by enzymes

Question 26

how is paracrine specificity achieved?

Answer 26

achieved by receptor expression and rapid ligand metabolism