Chemical signaling

Question 1

how can cells exchange information?

Answer 1

via chemical or electrical signaling - example of neurons - both electrical (nerve impulse) and chemical (neurotransmitters) signals

Question 2

endocrine vs exocrine glands

Answer 2

Endocrine glands produce hormones that are released into the blood and exocrine glands like salivary, stomach, and sweat glands release their content into body cavities.

Question 3

ligand

Answer 3

a molecule that binds selectively to a specific site on another molecule

Question 4

ligands are released by a ___ and affect ___

Answer 4

source, target cells

Question 5

how do ligands act/function

Answer 5

1|approaches the binding site of the target cell
2|causes changes in the receptor’s conformation
3|this change is recognized by other processes in the cell, the signal is passed on and the cell changes its behavior (metabolic activity) like, for example, expressing some genes, increasing/decreasing amount of certain proteins
4|ligand dissociates from the binding site

Question 6

types of ligands

Answer 6

hormones, neurotransmitters, cytokines and calcium ions

Question 7

signal transduction pathway

Answer 7

sequence of interactions in cells triggered by ligand binding

Question 8

two types of ligand receptors

Answer 8

transmembrane and intracellular

Question 9

transmembrane receptor transduction pathway

Answer 9

1|reception
2|signal transduction - reactions producing second messengers
3|response - activation of cellular responses

Question 10

intracellular receptor transduction pathway

Answer 10

1|steroid hormone enters the cell (hydrophobic)
2|hormone-receptor complex formed
3|complex travels to the nucleus where it binds to the promotor region on the DNA and directly controls gene expression process

Question 11

what happens to the transmembrane receptor after ligand binding

Answer 11

binding causes a reversible conformational change – becomes catalytically active and causes the production of a secondary messenger within the cell – this conveys the signal to effectors within the cell that carry out the responses

Question 12

ligands chemical nature

Answer 12

1|hormones - amines, peptides, and steroids
2|neurotransmiters - amines, amino acids, gases, and esters
3|cytokines - group of small proteins

Question 13

ligand source

Answer 13

1|hormones - specialized cells in glands
2|neurotransmiters - presynaptic neurons
3|cytokines - wide range of cells
4|Ca ions - cells (pumped out by Ca pumps)

Question 14

where ligands go from the source

Answer 14

1|hormones - into blood capillaries and then to all parts of the body
2|neurotransmiters - across the synapse
3|cytokines - intercellular space
4|Ca ions - diffuse back through voltage-gated or ligand-gated channels

Question 14

ligands’ target cells

Answer 14

1|hormones - all cells (one or multiple TC in one or multiple parts of the body)
2|neurotransmiters - postsynaptic neuron (one specific only)
3|cytokines - cell that produces them or a nearby cell
4|Ca ions - the cell from which they were pumped out

Question 15

how ligands affect their TC

Answer 15

1|hormones - inhibiting/promoting gene expression
2|neurotransmiters - excites/inhibits transmission of an impulse
3|cytokines - changes in gene expression (and cell activity)
4|Ca ions - cause presynaptic neuron to release neurotransmitters

Question 16

longevity of ligands

Answer 16

1|hormones - long-lasting effects (minutes/hours)
2|neurotransmiters - short-lived effects (fraction of a second)

Question 17

examples of different types of ligands

Answer 17

1|hormones - insulin, thyroxin, testosterone
2|neurotransmiters - acetylcholine, norepinephrine, dopamine
3|cytokines - erythropoietin (EPO), interferon, interleukin

Question 18

The requirements for a signaling chemical

Answer 18

1) Distinctive in shape and chemical properties so the receptor can distinguish between it and other chemicals
2) Small and soluble enough to be transported

Question 19

receptors

Answer 19

proteins to which signaling chemicals bind at a specific site - they initiate changes in the target cell in response to binding of the chemical signal

Question 20

neurotransmitters transmit…

Answer 20

signals across synapses - they are secreted when a signal reaches the end of a presynaptic neuron

Question 21

cytokine is unable to…

Answer 21

cross the membrane (because of its hydrophilic nature) so it binds only to transmembrane receptors
cytokines have the most profound effect on the cell out of all other ligands!!

Question 21

cytokine (variability?)

Answer 21

one cytokine may be secreted by different cells (some by almost any)
different cytokines can be secreted by one cell
same cytokines can bind to different receptors on a single cell (producing different effects)

Question 22

what roles does cytokine play in the body

Answer 22

cell signaling roles in:
1|inflammation and other immune system responses
2|cell growth and proliferation control
3|development of embryos

Question 23

what roles do Ca ions play in the body

Answer 23

cell signaling in:
1|neurons - cause presynaptic neurons to release neurotransmitters into the synapse
2|muscles - causes muscle fibers to contract