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Biology > Plasma Membranes > Flashcards

Plasma Membranes Flashcards

1
Q

What is the structure of a lipid?

A
  • made of one glycerol and three fatty acids
    -Ester bonds
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2
Q

What is a phospholipids?

A

When the phosphate replaces the fatty acids

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3
Q

What types of membranes do eukaryotes have?

A
  • cell surface membrane
  • membrane bound organelles
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4
Q

What types of membranes do prokaryotes have?

A
  • cell surface membrane
  • no membrane bound organelles
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5
Q

What are the roles of cell membranes?

A
  • compartmentalisation
    - contains reactions in separate parts of cell
    - separates cell contents from environment
    - keeps harmful substances separate
  • cell signalling and recognition
  • control what enter and leaves cell
  • site of chemical reactions- photosynthesis
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6
Q

What are the components of cell membranes?

A
  • phospholipid
    - hydrophilic head
    - hydrophobic tail
  • phospholipid form a bilayer (basic structure of a membrane)
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7
Q

What is in a fluid mosaic model?

A
  • free moving phospholipids within the layer, relative to each other - gives it flexibility
  • proteins are embedded which vary in shape, size and position, like a mosaic
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8
Q

What are the functions of channel protein (intrinsic)?

A

Provides a hydrophilic channel that allows the passive movement of polar molecules and ions down a concentration gradient through membranes

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9
Q

What is the function of carrier proteins (intrinsic)?

A

Passive transport and active transport into cells. Involves shape of protein changing

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10
Q

What is the function of glycoproteins (intrinsic)?

A
  • cell adhesion and as receptors for chemical signals
  • cell communication/ signalling
  • cell to cell recognition
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11
Q

What is the function of extrinsic proteins?

A

To interact with heads of phospholipids or intrinsic proteins

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12
Q

What is an intrinsic protein?

A

When the protein goes through both layers of the bilayer

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13
Q

What is an extrinsic protein?

A

Proteins that only sit in one layer of the bilayer

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14
Q

What is the function of cholesterol?

A
  • regulates fluidity of membrane
  • adds stability without making them rigid
  • prevents them becoming too solid by stopping phospholipids grouping too closely and crystallising
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15
Q

What is the function of glycolipids?

A

Contains cell markers/antigens and can be recognised by cells of immune system as self or non self

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16
Q

All membranes are _______________ permeable?

A

Partially

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17
Q

What is cell signalling?

A

A complex system of intracellular communication

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18
Q

What are the three mechanisms of cell signalling?

A

1) receptor acts as ion channel
2) receptor activates a G protein
3) receptor acts as an enzyme

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19
Q

Signal molecules fit into __________ molecules on the cell surface ___________?

A
  • receptor
  • membrane
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20
Q

What molecules could the signal molecules be?

A

Neurotransmitters

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21
Q

What structures in the membrane could the signalling molecules be?

A

Glycolipids, glycoproteins

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22
Q

What is diffusion?

A

Net movement of particles from an area of high to low concentration until there is an equilibrium

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23
Q

What type of process is diffusion?

A

Passive process

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24
Q

What is a concentration gradient?

A

Difference in concentration between two areas

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25
Q

Why does increasing temperature increase the rate of diffusion?

A

An increase in temperature increases the kinetic energy of the particles which increases collision rate. This increases the rate of diffusion

26
Q

What factors of cells can affect the rate of diffusion?

A
  • surface area- the larger the area if an exchange surface the higher the rate of diffusion
    -thickness of membrane- thicker exchange surface the higher the rate of diffusion
27
Q

What can diffuse through a phospholipid bilayer and why?

A
  • non-polar molecules
  • very small molecules
  • small polar molecules e.g. water as it slowly diffuses through lipid based molecules
28
Q

Why can ions now pass through the phospholipids bilayer?

A

The hydrophobic interior repels ions so they cannot pass through

29
Q

What is facilitated diffusion?

A

The movement of molecules from an area of high to low concentration

30
Q

What factors affect the rate of diffusion?

A
  • temperature- higher temp=faster diffusion
  • surface area- larger surface=faster diffusion
  • concentration gradient- higher gradient=faster diffusion
  • size of particles- smaller particles=faster diffusion
  • diffusion medium- solid=slowest
    - liquid=faster
    - gas=fastest
31
Q

What are some factors that affect the rate of facilitated diffusion?

A
  • temperature
  • concentration gradient
  • surface area
  • membrane thickness
    -number of channel proteins present
32
Q

What is meant by the term ‘model cell’?

A

A human-made set up that represents a cell

33
Q

Describe the differences between dialysis tubing ans cell membranes with reference to transport across a membrane?

A
  • Dialysis tubing doesn’t have proteins
  • no energy in a model cell
34
Q

Explain why some ions can pass through dialysis tubing by diffusion but can only pass through the cell membrane by facilitated diffusion?

A
  • no hydrophobic interior so cannot repel ions
  • permeability of viskin tubing is determined by the size of the particles
35
Q

What is active transport?

A

The movement of molecules of ions from an area of low to high concentration (against concentration gradient)

36
Q

What uses active transport?

A
  • large and charged molecules
  • anything that needs to go the opposite way
37
Q

What is bulk transport?

A

The movement of large enzymes into or out of the cell

38
Q

What are the four types of bulk transport?

A
  • endo
  • exo
  • pino
  • phago
39
Q

What happens in endocytosis?

A
  • bulk transport into cell
  • cell surface membrane invaginates
  • vesicles are formed
  • vesicles pinched off into the cytoplasm
40
Q

What happens in exocytosis?

A
  • bulk transport out of cell
  • vesicles move to and fuses with the cell surface membrane
  • releases contents to outside of cell
41
Q

Active or passive?:
1) diffusion
2) facilitated diffusion
3) active transport
4) bulk transport

A

1) passive
2) passive
3) active
4) active

42
Q

Is ATP needed?:
1) diffusion
2) facilitated diffusion
3) active transport
4) bulk transport

A

1) no
2) no
3) yes
4) yes

43
Q

Is protein needed?:
1) diffusion
2) facilitated diffusion
3) active transport
4) bulk transport

A

1) no
2) yes
3) yes
4) no

44
Q

what is compartmentalisation?

A

the formation of separate membrane-bound areas in a cell

45
Q

what types of environments do cells usually exist in?

A

aqueous environments

46
Q

why are phospholipid bilayers suited for aqueous environments?

A

the outer surfaces of the hydrophobic phosphate heads can interact with water

47
Q

what do intrinsic proteins contain?

A

amino acids with hydrophobic R-groups on their external surfaces, which interact with the hydrophobic core of the membrane, keeping them in place

48
Q

what are the intrinsic proteins?

A
  • channel proteins
  • carrier proteins
  • glycoproteins
49
Q

what is cell signalling/ communication?

A

when the chemical binds to the receptor, it elicit a response from the cell. this may cause a direct response or set off a cascade of events inside a cell

50
Q

What is the movement of water molecules in osmosis?

A

Random
- move in both directions
- if moving on one side, then the net movement is high to low water potential

51
Q

Why is equilibrium needed in osmosis?

A

To ensure cells are normal so they can function

52
Q

What liquid has the highest water potential?

A

Distilled water

53
Q

What is water potential measured in?

A

Pascals (Pa) - unit of pressure

54
Q

Describe the process of osmosis when a cell is in water?

A

Water moves by osmosis from an area of high water potential outside the cell to an area of low water potential inside the cell- this causes the cell to burst (lyses/lysis)

55
Q

Describe the process of osmosis when the cell is in a solution?

A

Water moves by osmosis from an area of high water potential inside the cell to an area of high water potential outside the cell- causes cell to shrivel

56
Q

What is the definition of osmosis?

A

The net movement of water molecules across a partially permeable membrane from an area of high to low concern traction as a result of random motion

57
Q

What is the term for high solute concentration?

A

Hypertonic

58
Q

What is the term for low solute concentration?

A

Hypotonic

59
Q

What is the term for when the solute is at equilibrium with concentration.

A

Isotonic

60
Q

What is the term for a shrivelled cell?

A

Plasmolyzed

61
Q

What is the term for a cell with water equilibrium?

A

Flaccid

62
Q

What is the term for a cell that’s about to burst/ has burst?

A

Turgid

Biology (8 decks)

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