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Topic 2B - Cell Membrane > Cell Membrane Structure > Flashcards

Cell Membrane Structure Flashcards

1
Q

Explain why the structure of a membrane is described as fluid-mosaic

A

It is simply just a phospholipid bilayer but contains things like protein for transport and cell recognition

Fluid in the model, phospholipid/proteins that can move freely + structure

mosaic in the model is the cell bilayer composed of different parts e.g proteins

Extrinsic

Intrinsic

Cholesterol presented within bilayer

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2
Q

Give two functions of proteins in plasma membrane

A
  • The channel protein is able to transport ions/water by facilitated diffusion
  • The carrier protein helps to transport two molecules
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3
Q

Give two functions of the hydrophobic tails in phospholipids in cell membrane

A
  • Maintain different concentration gradient
  • Doesn’t pass water-soluble substances through easily
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4
Q

Why can’t an opitcal microscope be used to see plasma membrane?

A

Wavelength of light is too long to define the membrane

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5
Q

Properties of functions:

Proteins

A
  • Act as a hormone receptor
  • Acts as an enzyme
  • Involved in active transport
  • Act in conjunction with glycolipid as receptors
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6
Q

What is channel proteins?

A

Transport ions/water molecules by facilitated diffusion

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7
Q

What is carrier proteins?

A

They will bind to a specific molecule causing it to change shape and release to the other side

facilitated diffusion also ATP for active transport

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8
Q

What does it mean that both channel and carrier proteins are passive?

A

NO ATP

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9
Q

What is liposome?

A

Aqueous filled cavity filled with cytoplasm

has a continous barrier of bilayer

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10
Q

What is the main function of cell membrane?

A

Control the movement of substances in and out of the organelle/cell

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11
Q

What is the phospholipid compromised with?

A

Hydrophilic heads point outwards

Hydrophobic tails point inwards

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12
Q

How is the membrane flexible and self-sealing?

A

The structure of phospholipid

  • Allow lipid soluble molecules to pass through
  • No water soluble molecules
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13
Q

Where can the proteins be located?

A

Integrated through the membrane - intrinsic proteins

OR

On the surface - extrinsic proteins

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14
Q

What are intrinsic proteins?

A

Include carrier proteins

Allow substances to cross the membrane

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15
Q

Why is cholesterol important in cell membrane?

A

Make membrane more rigid

Reduce laternal movement of phospholipid

Prevents leakage of water and dissolved ions from the cell - very hydrophobic

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16
Q

What are glycolipids made from?

A

Made up of a carbohydrate that is bound to lipids

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17
Q

Function of glycolipids

A

Extend from the surface of cell - acts as a cell surface receptor for certain molecules

Allow cells to ahere to one another to form tissues

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18
Q

What are glycoproteins?

A

Carbohydrates that attach to extrinsic proteins

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19
Q

Function of glycoproteins

A

Act as a cell surface receptor and neurotransmitters

Allow cells to recognize one another as well as attach to form tissues

20
Q

What does it mean that the cell membrane is partially permeable?

A

Let some molecules through but not others

21
Q

Why are receptor cells useful?

A

Detect chemicals released from the other cells

They signal the cell to respond in some way

22
Q

Where is cholesterol presented within membrane?

A

Bilayer

23
Q

Properties of phospholipids

A
  • Head is hydrophilic
  • Tail is hydrophobic
  • Molecules automatically arrange themselves into a bilayer - heads face towards water side on either side
  • Centre of bilayer is hydrophobic so membrane doesn’t allow water-soluble substance e.g ions
  • It acts as a barrier for dissolves substances
24
Q

Is cholesterol a type of lipid?

A

Yes

25
Q

Is cholesterol present in all cell membrane?

A

Yes

expect bacterial cell membrane

26
Q

Where is cholesterol held in a membrane?

A

Fits between phospholipids

27
Q

Properties of cholesterol

A
  • Bind to hydrophobic tails of phospholipid causing them to pack more closely together
  • Restricts movement of phospholipids, making membranes less fluid and more rigid
  • Maintain the shape of animal cells, important for cells who aren’t supported by other cells e.g Red blood floating free in blood
28
Q

What are the different conditions that affects permeability of the cell membrane

A
  1. Temperature
  2. Solvent conditions
29
Q

How can you investigate permeability in a more practical sense?

A

Beetroot cells containing coloured pigment that leaks out

Higher permeability of the membrane , more pigment leaks out the cell

30
Q

Instructions of temperature affecting beetroot membrane permeability

A
  1. Use a scapel to carefully cut five pieces of beetroot in euqal sixes
  2. Rinse the pieces to remove pigment while cutting
  3. Add five pieces to five different test tubes containg 5 cm3 of water - use measuring cylinder
  4. Place each test tube in a water bath at different temperatures for same length of time
  5. Remove pieces of beetroot , leaving coloured liquid
  6. Coloirmeter to computer to collect data and draw a graph
31
Q

What is a colorimeter?

A

A machine that passes light through liquid to measure how much light is absorbed

The higher the absorbance , more pigment is released - higher permeability

32
Q

Why you need to be careful with colorimeter?

A

Need 5 minutes to stabilise before using and calibrating at zero

before taking a measurement through pure water

33
Q

What happens to the cell membrane with a temperature below 0 degree Celsius?

A

Phospholipid don’t have much energy so can’t move much

Packed closely together and membrane is rigid

Channel and carrier proteins may deform, increasing permeability of the membrane

Ice crystals may form pierce , higher permeability

34
Q

What happens to the cell membrane with temperature between 0 and 45 degree celisus?

A

Phospholipid can move around and aren’t packed tightly together

The membrane is partially permeable

Temperature increases, phospholipid move more as they have more energy

Increases permeability of the membrane

35
Q

What happens to the cell membrane with temperatures above 45-degree celsius?

A

Phospholipid bilayer start to melt and the membrane becomes more permeable

Water inside the cell expands putting pressure on the membrane

Channel proteins and carrier proteins deform , control what enters or leaves

Increases permeability

36
Q

Why is it important membranes allow recognition by other cells - importance to immune system

A

Use of glycoproteins/glycolipids - identify self cells

White blood cells don’t attack them

Allow identification of foreign cells/pathogens via their antigen

37
Q

Identify two functions of the cell membrane

A
  1. Controls/maintains the two environment
  2. Cell communication - chemical detection via receptors
38
Q

Identify two organelles and important of membrane in them

A
  • Mitochondria - contains enzyme for respiration - increase SA for these reaction
  • Nucleus - allows RNA to leave in transcription
39
Q

The more unsaturated fatty acids present in the membrane the more fluid it is. Cholesterol also affects the fluidity of the membrane.

Why is it key that there isn’t too much or too little cholesterol present in the membrane for optimum cell function?

A

– Too much cholesterol will make the membrane too rigid/less fluid and make exchange less efficient.

-Too little cholesterol will mean that the membrane is too fluid and breaks up/doesn’t provide the necessary structure

40
Q

Identify two types of molecules that can pass directly through the phospholipid bilayer.

A

O2,

CO2,

Uncharged,

Small

41
Q

Identify two types of molecules that cannot pass directly through the membrane and give examples of each

A
  • Large molecules e.g proteins, glucose
  • Charged molecule e.g. Na+ Cl- , K
42
Q

Which molecules can just diffuse straight through the cell membrane?

A

Small non-polar molecules

e.g oxygen and carbon dioxide

43
Q

How is water transported?

A

Water is polar so doesn’t diffuse easily

Move into cells through aquaporins

44
Q

Give one function of X.Y( glycoprotein/glycolipid)

A
  • Surface/extrinsic protein
  • Cell recognition
  • Binding to hormones
  • Identification
45
Q

Explain three features of a plasma membrane adapt for its functions

A

Extrinsic proteins

Glyproteins

Glycolipid

Act as antigens

Act as receptors

Topic 2B - Cell Membrane (4 decks)

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