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Module 2 > Biological Membranes > Flashcards

Biological Membranes Flashcards

1
Q

Roles of membranes

A

Sites of chemical reactions
Sites of cell communication (signalling)
Partially permeable barriers between
-> the cell and its environment
-> organelles and the cytoplasm and within the organelles

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2
Q

The fluid mosaic model is made up of what components

A
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3
Q

What role do phospholipids play

A

Form bilayer
Hydrophobic tail = inwards
Hydrophilic head = outwards
Act as a barrier to large, polar molecules
Only allow small, non-polar molecules to pass through by diffusion
Provides selective permeability

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4
Q

What role does cholesterol play

A

They fit in between the fatty acid tails within the bilayer
Stabilise the membrane structure
They regulate the fluidity of the membrane

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5
Q

What role do (general) proteins play

A

Forms pores (channels/carriers)
Can be intrinsic (transmembrane) or extrinsic

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6
Q

What role do glycolipids / glycoproteins play

A

Found sticking out of the surface of the bilayer
Act as antigens (recognise cells as self or foreign)
Cell signalling (allow communication across membranes & site of receptors for hormones & medicinal drugs)
Stabilise membrane & cell shape (by attaching to water molecules)
Cell adhesion (holds cells together in a tissue)

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7
Q

What role do membrane bound receptors play

A

Sites where hormones and drugs can bond to

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8
Q

Roles of membranes within cells

A
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9
Q

Role of cell surface membrane

A
  • Control what substances enter & leave the cell
    -> form partially permeable barriers between cell & its environments
  • cell signalling
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10
Q

The process of cell signalling and the role of the cell surface membrane

A
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11
Q

Factors that affect membrane structure / permeability

A

Temperature
Solvent concentration
pH

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12
Q

How does temperature affect membrane structure

A
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13
Q

How does solvent concentration affect membrane structure

A

Increases membrane permeability
1. Dissolve lipids in the membrane
2. Membrane then loses its structure

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14
Q

Different types of movement of molecules across the membrane

A
  1. Osmosis
  2. Passive processes
    -> diffusion
    -> facilitated diffusion
  3. Active processes
    -> endocytosis
    -> exocytosis
    -> active transport
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15
Q

What diffuses

A

Small non polar substances

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16
Q

What undergoes facilitated diffusion

A

This is diffusion using transport proteins (channel/carrier)
-> highly specific to molecules
For large polar molecules or ions

17
Q

How do carrier proteins work

A

Can change shape
Used in active transport

18
Q

How do channel proteins e.g. aquaporins -> allow charged shbstances & ions to diffuse through the cell membrane

A
  • water filled pores
    Used in facilitated diffusion
    Have a fixed shape
    Gated
    Part of the channel protein on inside surface of membrane & can move to close & open the pore
19
Q

How does endocytosis trasnsport LARGE materials INTO cells

A

Material is engulfed, forming small sacs (endocytic vacuole) and then absorbed into the cell
E.g. phagocytosis & pinocytosis
The bulk intake of solid (phago) & liquid materials (pino)

20
Q

How does exocytosis work to transport materials out of cells

A
  • content of vesicle packaged into secretory vesicles
    -> secretory vesicles formed from golgi apparatus
    -> secretory vessel travels to cell surface membrane
    -> vesicle fuses with cell surface membrane
    -> Contents of vesicle discharged to exterior
21
Q

How does active transport work

A

-> movement of substances against the concentration gradient, from low to hifh
-> uses ATP & a carrier protein
(ATP needed for the carrier protein to change shape)

22
Q

What is osmosis

A

The net movement of water across a partially permeable membrane from an area of high concentration to an area of low concentration down the concentration grsdient

23
Q

2 ways water moves through the phospholipid bilayer

A

-> fitting between phospholipids (directly through the bilayer)
-> via protein channels (aquaporins)

24
Q

Hypotonic vs isotonic vs hypertonic

A

Hypotonic -> solute conc outside of cells is lower than inside

Isotonic -> solute conc outside of cell = inside of cell

Hypertonic -> solute conc outside of cell > higher than inside

25
Q

Crenation of animal cell

A
26
Q

Cytolysis of animal cells

A
27
Q

How plant cells befome turgid

A
28
Q

How plant cells become plasmolysed

A
29
Q

How do steroid creams work when applied onto skin

A

Skin has large surface area for absorption
Skin has networks of capillaries
Steroids are non-polar, so can cross phospholipid bilayer

Module 2 (12 decks)

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