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HNC Applied Science in Biology and Chemistry > Cell Biology- Outcome 3 > Flashcards

Cell Biology- Outcome 3 Flashcards

Cellular Communication

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1
Q

what factors must be regulated and monitored to regulate a cells internal environment

A
  • nutrition
  • hormone regulation (temperature, metabolism)
  • excretion of waste and toxins
  • repair when damaged
  • identification
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2
Q

what are different ways of cells communicating?

A
  • directly with adjacent cells
  • different mechanisms with cells over a large difference
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3
Q

what are eukaryotic cells separated by?

A

extracellular matrix

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4
Q

what is an example of when cells are pressed together?

A

epithelia tissue

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5
Q

what are examples of junctions between animal cells?

A
  • desmosomes
  • tight junctions
  • gap junctions
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6
Q

describe desmosomes

A
  • localised patches that hold 2 cells together
  • act like rivets and are also known as anchoring junctions
  • tightly joined but there are still gaps between them
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7
Q

how do desmosomes form links between cells and what protein is involved in this?

A
  • through connecting intermediate filaments of the cytoskeleton
  • can be further linked by a family of proteins known as cadherins
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8
Q

how are desmosomes arranged?

A

they are localised along the cell membrane in areas known as plaques

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9
Q

what is the function of desmosomes?

A

to provide strength and stability

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10
Q

where are desmosomes found?

A

in cells subject to stress such as epithelia and cardiac tissue
- where stress can be communicated / shared between cells

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11
Q

what is the function of a tight junction?

A

not directly involved in cellular communication - function as a ‘sealing junction’

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12
Q

what do tight junctions form and what is the effect?

A

leak-proof seal between cells so that material has to enter the cell through transport mechanism

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13
Q

how are the membrane proteins which form at tight junctions arranged?

A

arranged like beads on a string that span the adjacent membranes of each thigh junction

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14
Q

what are examples of cells where tight junctions are found?

A

intestinal cells and bladder cells

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15
Q

describe the composition of gap junctions

A
  • specialised areas of the cell membrane connecting the cytoplasm of adjacent cells
  • intracellular chancels made up of 4 transmembrane protein called connexins
  • 6 connexins make up a connexon channel
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16
Q

how is a gap junction formed?

A

when 2 connexons from adjacent cell membranes ‘dock’ together then a gap junction is formed

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17
Q

what is the function of a gap junction?

A
  • allows passage of ions and small molecules such as amino acids and sugars (means they don’t have to go through plasma membrane)
  • because ions can flow through the junction - allows changes in membrane potential from cell to cell
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18
Q

what do gap junctions allow?

A
  • rhythmic contraction of the heart
  • neurones to communicate impulses
  • during labour - gap junction between smooth muscle allow passage of ions and therefore contractions occur
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19
Q

what is an example of a junction that allows communication between adjacent plant cells?

A

plasmodesmata

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20
Q

describe the arrangement of plasmodesmata and explains what this allows

A
  • cylinder-like bridges connecting one cell with another
  • bridge links the cell walls and is actually lined by plasma membrane

-cytoplasms of neighbouring cells are linked - allows exchange of small molecules such as salt, sugars and amino acids between the cytoplasm of both cells

21
Q

what us cytoplasmic streaming?

A

where the cytoplasms of neighbouring cells are linked and so allows exchange of small molecules between cytoplasm of both cells

22
Q

how can the streaming of molecules in cytoplasmic streaming be regulated?

A

by constricting or dilating the openings at each end of the channel

23
Q

when do cells use extracellular signalling mechanisms?

A

when cells are located at a significant distance away from each other

24
Q

what are the tree main stages of cellular signalling?

A

reception, signal transduction, response

25
Q

describe what happens during the reception stage of cellular signalling

A
  • target cell possesses a receptor molecule on its cell membrane which receives signal and converts it into response
26
Q

what is a signal molecule called and what is its function?

A
  • called a ligand
  • can bind and activate a receptor molecule on the target cell membrane
  • ligand and receptor are a complimentary fit
27
Q

what is a ligand said to be and what may it be?

A
  • ligand said to be first messenger
  • ligand may be a hormone which has been secreted in one part of the body and travel to another organ to perform its function
28
Q

describe what happens during the signal transduction stage of cellular signalling

A
  • binding of ligand results in conformational change in receptor
  • change in shape of receptor triggers intracellular events leading to production of second messengers which amplify the signal
29
Q

what are examples of second messengers during the signal transduction stage?

A
  • cyclicAMP (cAMP)
  • calcium
30
Q

describe what happens during the response stage of cellular signalling

A
  • cellular response depends on signalling molecule and the function of the target cell
  • response may be:
    Gene Regulation
    Inactive to active enzyme
    Enzyme Catalysis
    Muscle cell contraction
    Growth & developmental of the cell
31
Q

what are the two different forms of distance signalling?

A

chemical signalling and electrical signalling

32
Q

what are examples of chemical signalling?

A

insulin signalling and growth hormone signalling

33
Q

what is chemical signalling?

A

chemical messengers are released by specialised cells and have an effect on the target cell

34
Q

what is an example of a chemical messenger?

A

any hormone

35
Q

explain what happens during insulin signalling

A
  • insulin is secreted from Beta cells in the pancreas
  • insulin travels through bloodstream and reaches many target cells such as
    hepatocytes
    muscle cells
    brain cells
    adipocytes
    macrophages
  • each target cell will have receptor protein which is complimentary to shape of insulin
  • once receptor is activated it will initiate a signalling cascade where response will be open to glucose channel - allows entry of glucose inside cell and effectively remove glucose from bloodstream
36
Q

explain what happens during growth hormone signalling

A
  • release of growth hormone from anterior pituitary gland is under control of hypothalamus
  • target cells may be liver as well as cartilage, bone and muscle cells and adipocytes
  • response in target cells is o stimulate cell growth and division
  • at cellular level this can lead to
    actin rearrangement
    increased glucose metabolism
    increase protein synthesis
37
Q

what cells carry out electrical signalling?

A

neurons

38
Q

what are the function of neurones?

A

specialised cells which are capable of transmitting an electrical impulse either to another neurone cell, a muscle cell or endocrine cell

39
Q

what are the function of dendrites?

A

receives electrical signals from receptors

40
Q

what is the function of the cell body?

A

control centre contains nucleus ribosomes and most of the cytoplasm

41
Q

what is the function of the axon?

A
  • propagates signal to synaptic knobs
  • may be myelinated or unmyelinated
42
Q

what is the function of the synaptic terminal?

A

transmit signal via neurotransmitter

43
Q

what is the synapse?

A

functional region between adjacent neurones

44
Q

what is the synaptic cleft?

A

gap between one neurone and another

45
Q

what is the neuro-effector junction?

A

area between motor neurone effecter

46
Q

what is the pre-synaptic neurone?

A

neuron before gap

47
Q

what is the post-synaptic neurone?

A

neurone after gap

48
Q
A

HNC Applied Science in Biology and Chemistry (5 decks)

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