Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Biology > Plasma Membranes > Flashcards

Plasma Membranes Flashcards

1
Q

Name 4 roles of cell-surface membranes

A

1- Compartmentalisation
2- Chemical reactions
3- Cell signalling
4- Controls which molecules can enter or leave a cell/organelle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is compartmentalisation?

A

The formation of separate membrane bound area
It’s vital in order to:
- Separate ant reactions that are incompatible
- Allows for formation of specific conditions within the area surrounded by the membrane
- Allows for the creation of chemical gradients
- Protects cell components

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is cell signalling?

A
  • Cells in multicellular organisms need to communicate to coordinate their response
  • Protein has a specific tertiary (3’) structure, e.g. hormones
  • Protein bonds to specific receptor with complementary tertiary structure on cell membrane
  • Activate a response
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is the structure of cell-surface membranes?

A
  • Formed from a phospholipid bilayer: hydrophilic phosphate heads form both the inner and outer layer of a membrane, the fatty acid tails form a hydrophobic core inside the membrane
  • Cells normally exist in aqueous environments. Phospholipid bilayers are perfectly suited as the hydrophilic heads can interact with water
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What molecules can diffuse through the phospholipid bilayer?

A

Small, non-polar molecules, e.g. CO2, O2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Describe and explain the ‘fluid mosaic model’ of membrane structure

A
  • The phospholipids are free to move within the layer relative to each other (they are fluid), giving the membrane flexibility
  • The proteins embedded in the bilayer vary in shape, size and position (in the same way as mosaic tiles)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What are intrinsic proteins?

Give 2 examples

A

Transmembrane proteins that are embedded through both layers of a membrane
Channel and carrier proteins

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What are channel proteins?

A
  • A transport protein
  • Allows passive movement of small polar molecules down a concentration gradient
  • E.g. ions, Na+, K+, Ca+
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What are carrier proteins?

A
  • A transport protein
  • Allows passive and active movement of large molecules
    E.g. carbohydrates
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What are glycoproteins?

A
  • Intrinsic proteins
  • They are embedded in the cell-surface membrane with attached carbohydrate chains
  • Cell signalling
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What are glycolipids?

A
  • Lipids with attached carbohydrate chains

- These molecules are called cell markers and can be recognised by the cells of the immune system as self or non-self.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What are extrinsic proteins?

A

Present in the one side of the bilayer

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is cholesterol?

A
  • A lipid
  • Binds to hydrophobic tails
  • Makes membrane more rigid/less flexible
  • Strength and support (animal cells don’t have a cell wall)
  • It regulates the fluidity of membranes
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

How does temperature affect membrane structure?

A

Freezing: -10°C

  • Carrier proteins + protein channels lose shape and open
  • Cell membrane damaged by ice crystals
  • Membrane is very permeable

Cold: 0°C

  • Low KE
  • Phospholipids close together
  • Membrane is stiff
  • Least permeable

Warm: 20°C

  • phospholipids have more KE
  • More movement
  • More space between them
  • More permeable

Hot: 40°C +

  • Carrier proteins + protein channels denature
  • Open
  • Phospholipid bilayer melts
  • Membrane is very permeable
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

How do solvents affect membrane structure?

A
  • Some solvents can dissolve the phospholipids in the membrane
  • E.g. ethanol
  • Loses it’s structure
  • Increases it’s permeability
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is simple diffusion?

A

Net movement of molecules from high to low concentration down a concentration gradient

17
Q

What factors affect the rate of diffusion?

A
  • Temperature

- Concentration difference

17
Q

How does temperature affect the rate of diffusion?

A
  • Higher temps increase KE
  • More movement
  • Increases rate
19
Q

How does concentration gradient affect the rate of diffusion?

A

The steeper concentration gradient, the faster the rate of diffusion

20
Q

What factors affect the rate across membranes?

A
  • Surface area

- Diffusion distance (thickness of membrane)

21
Q

How does SA affect the rate of diffusion across membranes?

A

The larger the surface area, the faster the rate of diffusion

22
Q

How does the thickness of the membrane affect the rate of diffusion across a membrane?

A

The shorter the diffusion distance the faster the rate of diffusion

23
Q

What is facilitated diffusion?

A

Net movement of molecules from high to low concentration down a concentration gradient through a channel protein

24
Q

What is active transport?

A

The net movement of particles from an area of low concentration to an area of high concentration against a concentration gradient requiring ATP and using carrier proteins

25
Q

What is cotransport?

A
  • Transport via a carrier protein
  • Moves 2 molecules at once
  • One goes down it’s concentration gradient
  • One goes against its concentration gradient
26
Q

What is bulk transport?

A

Another form of active transport
- Large molecules such as enzymes, hormones and whole cells like bacteria are too large to move through channel or carrier proteins, so they are moved into and out of the cell by bulk transport

27
Q

What is endocytosis?

A
  • A type of active transport when large molecules are absorbed into cells
  • E.g. Phagocytosis (solids)
  • Object is engulfed in cel membrane
  • Taken into cytoplasm
  • Object is surrounded by membrane forming a vesicle
  • Active, uses ATP
28
Q

What is exocytosis?

A
  • A type of active transport when large molecules are released outside the cell
  • E.g. neurotransmitters
  • Vesicles fuse with cell membrane
  • Contents are released outside cell
29
Q

What is osmosis?

A

The passive movement of water molecules from a high water potential to a low water potential across a partially permeable membrane

30
Q

What is water potential?

A
  • The pressure exerted by water molecules as they collide with a membrane or container
  • Units = pascals (Pa) or kilopascals (kPa)
  • High = higher % of water molecules, low % solute
  • Low = lower % of water molecules, high % solute
31
Q

What is hydrostatic pressure?

A

The pressure exerted by a fluid at equilibrium at any point of time due to the force of gravity

32
Q

Describe an isotonic cell

A
  • No net movement of water by osmosis

- No change in shape or size

33
Q

Describe a hypertonic cell

A
  • Very low water potential
  • Cytoplasm has a higher water potential than its surroundings
  • Water moves out of the cell down the water potential gradient by osmosis
Plants:
- Cytoplasm and cell membrane shrink away from cell wall
- Cell becomes flaccid
Animals:
- Cytoplasm and cell membrane shrink
- Cell becomes flaccid
34
Q

Describe a hypotonic cell

A
  • Very high water potential
  • Cytoplasm has a linear water potential than its surroundings
  • Water moves into cells down water potential gradient by osmosis

Plants:
- Strong cellulose cell walls don’t burst/lyse
Animals:
- Weak cel surface membrane so burst/lyse
(Osmotic lysis)

35
Q

Describe a practical investigation into the factors affecting the diffusion rates in model cells

A
  • Model cell = starch solution
  • Potassium iodide surrounding it will diffuse into model cell
  • Time colour change (clear —> blue/black)
  • Repeat at a range of: temps, SA, thickness, conc
  • Minimum of 3 repeats
  • Calculate mean/stats test
36
Q

Describe a practical investigation into the permeability of cell membranes

A
  • Use a colourful tissue, e.g. beetroot
  • Wash thoroughly
  • Range of at least 5: water baths, solvent conc, e.g. alcohol
  • Control all other variable, e.g. time, size of beetroot
  • Measure volumes, e.g. volumetric pipette
  • Coloure is determined using a colorimeter set to absorb ace
  • Use a distilled water blank
  • Repeat at least 3 times
  • Take mean values
37
Q

Describe how molecules are actively transported across a membrane

A

1-

Biology (19 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions