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bio-membranes Flashcards

Know the function of biological membranes Know the structure and composition of membranes Know the structure and function of membrane proteins including receptors enzymes, channel proteins and carrier proteins Transport across biological membranes including active and passive transport

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1
Q

what are all bio-membranes composed of?

A
  • lipids and porteins
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2
Q

what can we note about all bio-membranes?

A
  • they have two ‘leaflets’, one faces outwards whilst the other faces inwards. they both have different compositions.
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3
Q

how permeable are bio-membranes?

A
  • selectively semi-permeable
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4
Q

what does the membrane do in cells?

A
  • separates cell from its surroundings.
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5
Q

what are the functions of membranes?

A
  • defines boundaries within cell, retains metabolites and ions within cell
  • provides compartmentalisation within the celll
  • acts as a surface at which bio-chemical reactions can occur, increases the surface area so more reactions can occur.
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6
Q

what else can membranes also allow?

A
  • allows import + export, selective transport of waste products and toxins
  • senses external signals, transmits info into the cell and transmits nerve signals.
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7
Q

Why do nerves rely on membranes?

A
  • they rely on membranes to transmit signals
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8
Q

what is meant by osmosis?

A
  • passive net movement of water through a selectively permeable membrane towards a region of higher solute concentration (diffusion of water)
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9
Q

how does the water move in terms of water potential in osmosis?

A
  • the water moves from areas of high-water potential (low conc of solute) to areas of low water potential (high conc of solute).
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10
Q

what does the membrane bilayer consist of?

A
  • consists of phospholipid bilayer; its hydrophilic head interacts with water and the hydrophobic tails (fatty acid) are packed inside.
  • one layer faces cytoplasm and the other faces the extracellular space or inside of membrane enclosed organelles
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11
Q

what are physical properties of membranes?

A
  • fluid mosaic model (dynamic + flexible)
  • not permeable to large polar solutes and ions
  • is permeable to small polar solutes such as water and ethanol + non-polar compounds
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12
Q

what sterols are in the cell membranes of eukaryotes?

A
  • animal cells –> cholesterol
  • plant cell –> phytosterol
  • fungi –> ergosterol
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13
Q

what do sterols do?

A
  • acts as a buffer; stops membrane from becoming too liquid whilst also stopping it from crystallising when too cold.
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14
Q

key features of the fluid mosaic model?

A
  • integral proteins firmly embedded with the membrane
  • peripheral proteins are weakly attached and can be removed easily
  • some proteins are non covalently attached and some are linked to the membranes lipids
  • called fluid because the lipids , proteins, carbohydrates etc can move within their leaflets.
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15
Q

what are the functions of lipids in membranes?

A
  • intercellular coinage
  • enzymatic activity
  • active + passive transport
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16
Q

What types of proteins are there in terms of the fluid mosaic model/membranes)?

A
  • channel proteins
  • carrier proteins
17
Q

what are the functions of channel proteins in membranes?

A

-like tunnels through the membranes
- can be open or closed
- allows facilitated diffusion; substance moves down its concentration gradient so doesn’t require energy.

18
Q

what are the functions of carrier proteins in membranes?

A

-only open to one side of membrane at a time
- can be uniporters (moves things in one direction only) or co-transporters (symporters/antiporters) – this requires energy whilst uniporters don’t (is passive)

19
Q

what is co-transport?

A
  • moves two substances across the membrane; uses the movement of other substances along its conc gradient, requires ATP.
20
Q

how can you move enzymes through a cell membrane?

A
  • by using endo or exo cytosis.
21
Q

what does a shorter fatty acid tail mean?

A
  • fewer van der walls holding it together therefore membrane is more fluid.
22
Q

what does a longer fatty acid tail (phospholipid) mean?

A
  • more van der walls holding it together therefore membrane is less fluid.
23
Q

how can temperature affect the membrane?

A
  • warmer membrane = more fluid
  • colder membrane = less fluid + phospholipid may crystallise.
24
Q

what is a membrane receptor?

A
  • an integral protein; its job is to receive a signal from outside the cell and signal to make a change inside the cell
25
Q

what are enzymes?

A

= proteins; is a biological catalyst.

26
Q
A

biology (10 decks)

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