lec 3- cellular interactions in animals

Question 1

what does the cell surface consist of?

Answer 1

The cell surface consists of the plasma membrane and a protective layer just beyond the plasma membrane made of fibre composites

Question 2

what is the fibre composite that is secreted by most animal cells called?

Answer 2

extracellular matrix (ECM)

Question 3

what is the extranuclear matrix made of?

Answer 3

fibrous part consists of collagen, while the ground part consists of proteoglycans

Question 4

what holds animal cells together?

Answer 4

Animal cells are held together by tight junctions (seals cell together), desmosomes (connect to cytoskeleton of cell), and gap junctions (communication)

Question 5

what are tight junctions made of and what do they do?

Answer 5

Tight junctions are composed of membrane proteins in adjacent animal cells, chains of these proteins line up and bind to each other, resulting in a water tight stitch to occur

Question 6

where are tight junctions found?

Answer 6

Tight junctions are found in epithelia and are dynamic and variable

Question 7

what are desmosomes made of and what do they do?

Answer 7

Desmosomes are composed of proteins that link the cytoskeletons of adjacent cells and they resist pulling/shearing forces

Question 8

where are desmosomes found?

Answer 8

Mainly found in epithelial and muscle tissue

Question 9

what do gap junctions do?

Answer 9

help cells communicate by letting ions and small molecules to pass through channels

Question 10

why are chemical signals different from action potentials?

Answer 10

because chemical signals last longer

Question 11

what are the five categories of chemical signals?

Answer 11

-Autocrine signals
-Paracrine signals
-Endocrine signals
-Neural signals
-Neuroendocrine signals

Question 12

what do an autocrine signals do?

Answer 12

Acts on the same cell that secreted them, eg. of autocrine signals is cytokines

Question 13

what do a paracrine signals do?

Answer 13

Diffuse locally and act on target cells near the source cell, eg. of paracrine signals are insulin and glucagon

Question 14

what do endocrine signals do?

Answer 14

Are carried to distant cells by blood or other body fluids and act upon them

Question 15

what organ makes endocrine signals?

Answer 15

glands

Question 16

what do neural signals do?

Answer 16

The presynaptic neuron releases neural signals (neurotransmitters) that bind to the receptor on the postsynaptic neuron resulting in a change in the membrane potential

Question 17

why are neural signals fast?

Answer 17

Neural signalling is fast because action potentials spread rapidly and have a short distance to diffuse across the synaptic cleft

Question 18

what do neuroendocrine signals do

Answer 18

Hormones released from neurons that are carried by blood or other body fluid to act upon another cell, eg. ADH

Question 19

what are hormones?

Answer 19

Hormones are signalling molecules sent from a cell to another with a distance between them

Question 20

how do integrators send a response to effectors?

Answer 20

by using horomones

Question 21

what molecule does a hormone bind to and what happens to it?

Answer 21

it binds to a receptor molecule and it causes it to change shape and activity

Question 22

what are the three types of hormones?

Answer 22

-Peptides and polypeptides
-Amino acid derivatives
-steroids

Question 23

which hormones bind to outside receptors and inside receptors, as well as which are not soluble, mostly not soluble, and soluble?

Answer 23

-Peptides are not soluble so they bind to surface receptor
-Amino acids are mostly not soluble so they bind to surface receptor
-Steroids are soluble so they bind to inside receptor

Question 24

can signal receptors be blocked?

Answer 24

yes

Question 25

how are lipid-soluble hormones processed?

Answer 25

Lipid binds to receptor inside cell, triggers change in cell activity, the hormone-receptor complex is transported to nucleus, where it alters gene expression

Question 26

where does the hormone-receptor complex bind to?

Answer 26

The hormone-receptor complex only binds to hormone-response element part of DNA

Question 27

how are lipid-insoluble hormones processed?

Answer 27

Hormone binds to plasma membrane receptor, this results in signal transduction where either the signal is amplified and the extracellular signal turns into a intracellular signal with many downstream molecules causing a response, or it is diversified and a cell receives the signal causing it to change several times.

Question 28

what is G-protein coupled receptors?

Answer 28

A type of plasma membrane receptor that works with intracellular G-proteins which trigger a second messenger after being activated by the signal receptor.

Question 29

what is a second messenger?

Answer 29

a non protein, such as other molecule or ions

Question 30

what are the three steps of G-protein coupled signalling?

Answer 30

1. G protein is inactive (bound to GDP) and then signal arrives and binds to receptor
2. Signal-receptor complex changes conformation resulting in G protein binding to GTP (activated) and splitting into two parts
3. Activated G protein binds to enzyme and induces production of second messengers which triggers a response

Question 31

is signal Amplification a 1:1 ratio?

Answer 31

No

Question 32

what happens when glucose is high?

Answer 32

decrease in blood pH and chance for diabetes, so insulin is released to decrease it

Question 33

what happens when glucose is low?

Answer 33

not enough fuel for brain, so glucagon is released to increase it

Question 34

what does GLP-1 do?

Answer 34

GLP-1 increases insulin secretion and inhibits glucagon release, it also lowers appetite

Question 35

what does Ozempic drug do?

Answer 35

binds to GLP-1 to trigger it