8: How Cells Communicate with Each Other Flashcards Preview

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Flashcards in 8: How Cells Communicate with Each Other Deck (38):
1

Why do cells communicate?

Cells need to be able to respond as a cell, and as part of a whole tissue
Why do cells communicate?
They respond to signals from other cells and from the environment
These signals are often chemical
Communication can be direct or relayed

2

Direct transport

channels, transporters, may be general or selective, gated or not
A relay of information, usually a
signal cascade

eg.
ligand gated ion channels
voltage gated ion channels

3

“Relayed” signal

A relay of information, usually a
signal cascade
eg.
G protein coupled receptors
tyrosine kinase receptors
intracellular receptors

4

Secreted signals can be ______ or _____ _______

local
long distance

5

Local signaling
Long distance signaling

growth factors such as fibroblast
growth factor – FGF1 (paracrine)
• Neurotransmitters such as
acetylcholine – Ach (synaptic)

6

Long distance signaling

Signals act from a distance
• Hormones produced by specialized cells travel
via circulatory system to act on specific cells
eg. insulin from pancreatic beta cells bind to insulin
receptors (tyrosine kinase type) initiating a cascade
which results in glucose uptake

7

Three main steps of Cell signaling ?

Reception
Transduction
Response

8

1. RECEPTION
_______ protein (primary messenger) binds to a ________protein
Shape + chemical state change in ________ protein
Allows or causes the activation of an _______

Signalling, receptor
receptor
enzyme

9

2. TRANSDUCTION
The activated enzyme can cause a _____of changes to occur
Relay molecules known as “_____ _______”
Multiple other enzymes are activated
Each activated enzyme causes a series of changes, a ______ _________
pathway

relay
second messengers
signal transduction

10

3. RESPONSE
All of the _______ _______ cause one or more functions to occur in the cell
This is where the cell actually does something

activated enzymes

11

Only certain cells at certain times will have
particular _____ _______ , meaning that while
the signal might be widespread the
transmission of the signal will only interact and activate
where it is needed

target receptors

12

Receptors can be:
_______ receptors or
____________/ ___________
receptors:

Intracellular
Membrane- bound/ cell surface

13

Intracellular receptors:
Primary messenger is generally __________and/or small – lipid soluble, can
cross PM
_______common method of signaling
eg. Testosterone, estrogen, progesterone, thyroid hormones bind to receptors in the
cytoplasm and move to nucleus as a complex

hydrophobic
Least

14

Membrane- bound/ cell surface receptors:
Primary messenger is generally ________and/or large – need help to cross PM
______common method of signaling
eg. G Protein Coupled Receptor, Receptor Tyrosine Kinase, ligand-gated ion channel

hydrophilic
Most

15

(G protein coupled receptors) Transmembrane proteins – pass PM how many times?

7 times

16

___________are molecular switches which
are either on or off depending on
whether GDP or GTP is bound

G proteins

17

(GPCRs)
At rest, receptor is unbound and G
Protein is bound to GDP.
The enzyme is in an ____ state.
Ligand binds receptor, and binds the
G protein. ___displaces ___. The
enzyme is still _____.
Activated G Protein dissociates from
receptor. Enzyme is activated to give cellular response
G Protein has GTPase activity,
promoting its release from enzyme,
reverting back to resting state

inactive
inactive
GTP displaces GDP

18

Ligand gated ion channels/receptors contain a ____.Binding of ligand (eg neurotransmitter) at specific
site on receptor rises in change in _____. channel opens /closes as the receptor
changes shape
____ can pass through channel

Gate
shape
ions

19

Receptor:

a molecule/protein which responds to a specific ligand

20

Ligand:

a signalling molecule that binds specifically to another protein

21

Ion channel:

membrane protein through which specific ions can travel

22

Ion channel receptor

membrane protein through which specific ions can travel,
in response to ligand binding (also known as ionotropic receptors)

23

Ligand gated ion channels/receptors.
At rest, _____ is unbound
and gate is closed.
Upon ligand binging, gate
opens, ______ ____ can flow
into cell.
Following _____ _______, gate closes,
back to resting.

ligand
specific ions
ligand dissociation

24

Which body system relies heavily on
ligand gated ion channels?

The nervous system:
– released neurotransmitters bind as ligands to
ion channels on target cells to propagate
action potentials

25

A typical phosphorylation cascade:

______ _________proteins by transfer
of a phosphate group from ATP
Series of protein kinases each adding a
______ to the next kinase
Phosphatases then ________ (remove)
rendering the protein inactive, but recyclable

Kinases phosphorylate
phosphate
dephosphorylate

26

Sometimes another small molecule is included in the cascade, these
are?
What are our 2 examples?

second messengers
cAMP and calcium ions

27

Activated adenyl cyclase converts ___to ____
cAMP acts as a ____ ______ and
activates downstream protein (which could
be the start of a phosphorylation cascade)

ATP
cAMP
second messenger

28

___[Ca2+] inside cell (typically~100nm)
___high [Ca2+] outside the cell
(more than 1000 fold)

Low
Very

29

_________of concentration via
______ ______ important as high [Ca2+]
can damage cells!
-out of cell
-into ER
-into mitochondria

Maintenance
calcium pumps

30

Why so many steps?

Amplifies the response
Provides multiple control points
Allows for specificity of response
temporal
spatial
despite molecules in common
Allows for coordination with other
signaling pathways

31

Examples of a cellular response include activation or regulation of

Gene expression
• Alteration of protein function to gain or lose an activity
• Opening or closing of an ion channel
• Alteration of cellular metabolism
• Regulation of cellular organelles or organisation
• Rearrangement/movement of cytoskeleton
• A combination of any of these

32

Ca2+ and IP3 in GPCR signalling

Here, the activated protein is
phospholipase C which then cleaves PIP2
(a phospholipid) into DAG and IP3
IP3 diffuses through
cytosol and binds to a
gated channel in the ER
Calcium ions flow out of
ER down concentration
gradient and activate
other proteins towards
a cellular response

33

All of the signals are for a limited time: activation usually promotes the start of _______, so that signalling is of short period of time, ensuring
________ __________

deactivation
homeostatic equilibrium.

34

Turning off the response is important so it is ready to respond again
cAMP is broken down by phosphodiesterase (PDE)
______blocks the action of PDE

caffeine

35

cAMP in GPCR signalling. This pathway is disrupted by what?

cholera toxin

36

_______is a long term energy store in
liver and skeletal muscle

Glycogen

37

glycogen breakdown results in?

glucose 1-phosphate

38

glucose 1-phosphate is then converted to glucose
6-phosphate which can be used in _____ to
generate ___

glycolysis
ATP