3.2.3.1 - Cell Membrane Structure and Function (Unit 2 Cells) Flashcards

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1
Q

All membranes around and within cells (including those surrounding organelles) are called…

A

plasma membranes

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2
Q

What do we call the plasma membrane that surrounds cells?

A

Cell-surface membrane

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3
Q

What is the function of a cell surface membrane?

A
  1. To separate the internal and external environments of the cell.
  2. To control the movement of substances in and out of the cell.
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4
Q

Name the components of a cell surface membrane.

A
  • Phospholipids
  • Proteins (intrinsic and extrinsic)
  • Glycoproteins
  • Glycolipids
  • Cholesterol
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5
Q

Phospholipids have polar and non-polar regions. A molecules that exhibits both of these properties is said to be…

A

Amphipathic

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6
Q

What is a polar molecule?

A

A molecule that does not have an even distriibution of electrons making some regions more negative than others.

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7
Q

What is a non-polar molecule?

A

A moelucle that has an even distribution of electrons, meaning it does not have areas that are more negative than other areas.

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8
Q

Phospholipids are made form which 3 molecules?

A

Phosphate

Glycerol

Fatty acid ‘tails’ x 2

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9
Q

Describe the phosphate head of a phospholipid.

A
  • Polar
  • Hydrophillic - water loving
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10
Q

Describe the fatty acid ‘tails’ of a phospholipid.

A
  • Non-polar
  • Hydrophobic - ‘water hating’
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11
Q

What are the functions of the phospholipids in the cell membrane?

A
  • Allow lipid-soluble (non-polar) substances to enter/exit the cell.
  • Prevent water soluble (polar) substances entering/exiting the cell.
  • Makes the membrane flexible and self-sealing.
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12
Q

Proteins in a cell membrane can either be __________ or _________.

A

Intrinsic or extrinsic

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13
Q

Which components of the cell-surface membrane are visible in this diagram?

A

Phospholipid bilayer

Cholesterol molecule (green)

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14
Q

Which components of the cell-surface membrane are visible in this diagram?

A

Phospholipid bilayer

2 x extrinsic proteins (carriers)

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15
Q

Which components of the cell-surface membrane are visible in this diagram?

A

Phospholipid bilayer

Glycolipid molecules x 2

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16
Q

Which components of the cell-surface membrane are visible in this diagram?

A

Phospholipid bilayer

Glycoproteins x 2

17
Q

Which components of the cell-surface membrane are visible in this diagram?

A

Phospholipid bilayer

Intrinsic proteins x 2 (channel and carrier)

18
Q

What are the funcitons of proteins in the cell membrane?

A
  • Provide structural support
  • Act as channels to transport polar molecules (facillitated diffusion)
  • Allow active transport (carrier proteins)
19
Q

What is the function of cholesterol in cell-surface membranes?

A
  • Reduces lateral movement of molecules that make up the membrane.
  • Acts as a buffer against temp increases/decreases to maintain membrane fluidity.
  • Prevents leakage of water and dissolved ions from the cell.
20
Q

What is a glycolipid?

A

A carbohydrate (polysaccharide) covalently bonded to a lipid.

21
Q

What are the functions of glycolipids?

A
  • Act as cell recognition sites (ABO blood group antigens are glycolipids)
  • Maintain stability of cell surface membrane.
  • Help cells to attach to one another and form tissues.
22
Q

What is a glycoprotein?

A

An extrinsic cell surface membrane prtoein with a carbohydrate covalently bonded to it.

23
Q

What are the funcitons of glycoproteins in the cell surface membrane?

A
  • Act as recognition sites (for hormones and neurotransmitters)
  • Help cells to attach and form tissues.
24
Q

Substances that can readily diffuse through the cell-surface membrane are small polar molecules and non polar molecules such as…

A
  1. Gases like oxygen and CO2
  2. Water
  3. Lipid-based hormones (steroids) e.g. oestrogen
25
Q

Substances that cannot readily diffuse through the cell-surface membrane are large and polar molecules and such as…

A
  1. Glucose
  2. Ions
  3. Proteins
  4. Urea
26
Q

In an investigation about diffusion and plasma membranes (beetroot discs) why would you ensure the temperature remained constant?

A

so that rate of diffusion remains constant

no change in fluidity of phosopholipids

no denaturation of membrane proteins

27
Q

In an investigation about diffusion and plasma membranes (beetroot discs) why would you ensure the the beetroot discs where shaken?

A

To ensure all the discs exposed to water/ all discs fully submerged

maintain concentration/diffusion gradient

28
Q

name the type of molecules that can diffuse through the membrane

A

lipid soluble

small

non-polar

29
Q

during cell fractionation a detergent can be used - why?

A

cell mebranes made of phospholipids

detergent dissolves membranes

releasing cell contents

30
Q

How does ultracentrifugation work to seprate cell organelles?

A

spin supernatent at low speed initially

then gradually increase the speed

separating organelles out based on their size/density

31
Q

How can you monitor the temperature of an experiment to ensure it doesnt change?

A

use a thermometer and monitor/take readings at regular intervals

32
Q

How does increasing temperature affect the plasma membrane?

A

Denatures proteins

damages the membrane

makes the membrane more fluid

33
Q

What is the effect of alcohol on the cell surface membrane?

A

Alcohol is a solvent, it dissolves phospholipids