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cell membranes Flashcards

1
Q

what is the cell membrane made of?

A

a phospholipid bilayer

double layer allows for selective permeability

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2
Q

what does the phospholipid bilayer consist of? (3)

A
  1. cholesterol - binds phospholipids
  2. protein channels
  3. glolipids & glycoproteins - for cell signalling + recognition
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3
Q

describe the tails of a phospholipid?

A
  • 2 tails
  • non-polar
  • hydrophobic
  • made of fatty acids
  • saturated: straight
  • unsaturated: kinked
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4
Q

describe the head of a phospholipid?

A
  • polar
  • hydrophilic
  • made of phosphate
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5
Q

4 functions of cell membrane

A
  1. act as a selective barrier to the passage of molecules
  2. maintain intracellular balance eg. absorb nutrients, expel waste
  3. has receptors to allow cells to respond to signals
  4. barrier separates intra/extracellular contents
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6
Q

4 types of transport across the membrane ?

A
  1. simple diffusion
  2. facilitated diffusion
  3. active transport
  4. osmosis
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7
Q

define simple diffusion

A

The passive movement of particles from a region of a higher concentration to a region of low concentration, through a partially permeable membrane

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8
Q

define facilitated diffusion

A

transport of particles through a partially permeable membrane, down their concentration gradient, by means of a carrier protein .

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9
Q

what are different type of carrier molecules?

A
  • ion channels,

- gated ion Channels (ligand, voltage, receptor)

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10
Q

define active transport

A

transport of particles against their conc. gradient, requiring ATP eg. Na+/K+ ATPase

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11
Q

what does amphipathic means?

A

All lipids in cell membranes are amphipathic - both hydrophilic & phobic

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12
Q

which molecules undergo simple diffusion ?

A
  • hydrophobic eg. O2 & CO2

- small, uncharged, polar eg. urea

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13
Q

which molecules undergo facilitated diffusion?

A
  • charged ions

- large, polar eg. glucose

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14
Q

how does primary active transport work ?

A

uses energy from ATP breakdown

to transport 1 molecule

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15
Q

how does secondary active transport work ?

A

energy is provided by the conc.gradient of the driving ion.

this energy allows driven ion to go against its conc.gradient.

2 types are transported at once

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16
Q

define osmosis

A

whenwater moves from an area of LOW solute concentration (low osmolarity, diluted) to an area of HIGH solute concentration (high osmolarity, more concentrated) through a partially permeable membrane.

via aquaporins

17
Q

what does endocytosis and exocytosis transport?

A

larger molecules that can’t diffuse

18
Q

what is endocytosis?

A
  • molecules bought into cell

- via the cell membrane engulfing the molecule, forming a vesicle, releasing it into the cell

19
Q

what are the 3 types of endocytosis?

A
  1. phagocytosis
  2. pinocytosis
  3. receptor mediated
20
Q

what is exocytosis?

A
  • transporting large molecules out of cell via secretory vesicles
  • a form of active transport
21
Q

what are the 4 main types of membrane receptors?

A
  1. channel linked
  2. enzyme linked
  3. G protein coupled
  4. intracellular
22
Q

what are the 3 main types of cell junctions?

A
  1. occluding
  2. communicating
  3. anchor
23
Q

explain tight junctions

A
  • type of occluding junction
  • seals neighbouring cells together
  • prevents diffusion or leakage between them
  • formed by a complex of proteins connecting the 2 membranes
24
Q

explain a gap junction

A
  • type of communicating junction
  • allows the passage of small water soluble ions and molecules between the 2 cells
  • eg. protein channels
25
Q

what are the 3 main anchor junctions?

A
  1. adherens junctions
  2. desmosomes
  3. hemidesmosome
26
Q

explain adherens junctions

A
  • type of anchoring junction
  • joins actin bundles in 1 cell to the actin bundles of its neighbouring cell
  • actin filaments only
27
Q

explain desmosomes

A
  • type of anchoring junction
  • provides mechanical strength and stability
  • joins intermediate filaments of cell to the intermediate filaments of the next cell
28
Q

explain hemidesmosomes

A
  • type of anchoring junction

- anchors intermediate filaments to the basal lamina of a neighbouring cell

1 IMMS (4 decks)

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