3.2.3.1 - Cell Membrane Structure and Function Flashcards Preview

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Flashcards in 3.2.3.1 - Cell Membrane Structure and Function Deck (30):
1

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

plasma membranes

2

What do we call the plasma membrane that surrounds cells?

Cell-surface membrane

3

What is the function of a cell surface membrane?

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

4

Name the components of a cell surface membrane.

  • Phospholipids
  • Proteins (intrinsic and extrinsic)
  • Glycoproteins
  • Glycolipids
  • Cholesterol

5

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

Amphipathic

6

What is a polar molecule?

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

7

What is a non-polar molecule?

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

8

Phospholipids are made form which 3 molecules?

Phosphate

Glycerol

Fatty acid 'tails' x 2

9

Describe the phosphate head of a phospholipid.

  • Polar
  • Hydrophillic - water loving

10

Describe the fatty acid 'tails' of a phospholipid.

  • Non-polar
  • Hydrophobic - 'water hating'

11

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

  • 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.

12

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

Intrinsic or extrinsic

13

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

Q image thumb

Phospholipid bilayer

Cholesterol molecule (green)

A image thumb
14

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

Q image thumb

Phospholipid bilayer

2 x extrinsic proteins (carriers)

A image thumb
15

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

Q image thumb

Phospholipid bilayer

Glycolipid molecules x 2

A image thumb
16

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

Q image thumb

Phospholipid bilayer

Glycoproteins x 2

A image thumb
17

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

Q image thumb

Phospholipid bilayer

Intrinsic proteins x 2 (channel and carrier)

A image thumb
18

What are the funcitons of proteins in the cell membrane?

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

19

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

  • 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

What is a glycolipid?

A carbohydrate (polysaccharide) covalently bonded to a lipid.

21

What are the functions of glycolipids?

  • 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

What is a glycoprotein?

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

23

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

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

24

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

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

 

25

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

  1. Glucose
  2. Ions
  3. Proteins
  4. Urea

26

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

so that rate of diffusion remains constant

no change in fluidity of phosopholipids

no denaturation of membrane proteins

27

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

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

maintain concentration/diffusion gradient

28

name the type of molecules that can diffuse through the membrane

lipid soluble

small

non-polar

 

29

during cell fractionation a detergent can be used - why?

cell mebranes made of phospholipids

detergent dissolves membranes

releasing cell contents 

30

How does ultracentrifugation work to seprate cell organelles?

spin supernatent at low speed initially

then gradually increase the speed

separating organelles out based on their size/density