Cell Membrane

Question 1

Roles of the membrane

Answer 1

• Partially permeable barriers
• Sites of chemical reactions
• Sites of cell communication within and between cells
• Compartmentalisation
• Provide the structure of organelles

Question 2

What is a phospholipid

Answer 2

• Has a hydrophilic head, made of a glycerol with a phosphate group attached
• Hydrophobic tail made of fatty acids

Question 3

Define the term Hydrophilic

Answer 3

• Uneven charges/polar
• Easily interact with water

Question 4

Define the term Hydrophobic

Answer 4

• Evenly distributed charges
• Repels water molecules

Question 5

Define the term Amphipathic

Answer 5

Some parts charged and some not

Question 6

Components of cells membranes

Answer 6

• Phospholipids
• Channel proteins
• Glycolipids
• Glycoproteins
• Cholesterol
• Extrinsic proteins

Question 7

What are Integral proteins

Answer 7

• Are carrier molecules or channels
• Help transport ions, sugars and amino acids across the membrane
• Some are receptors for hormones and enzymes

Question 8

What are Peripheral proteins

Answer 8

• Free on the membrane surface or bound to integral proteins
• May act as receptors
• Many are glycoproteins

Question 9

What are Glycoproteins and Glycolipids

Answer 9

• Act as a receptor sites
• can assist in binding cells together
• Glycoproteins = carbohydrate + protein
• Glycolipids = carbohydrate + phospholipids

Question 10

What is Cholesterol

Answer 10

• Lipid with a molecular formula C27H470
• controls membrane fluidity and permeability
• More cholesterol the less fluid and less permeable

Question 11

Which Factors affect permeability of the memebrane

Answer 11

• Solvents
• Temperature
• Detergents

Question 12

How do Solvents affect permeability

Answer 12

• Dissolve the lipids in the membrane

Question 13

How does Temperature affect permeability

Answer 13

• Negative temperatures cause ice crystals to form and pierce the membrane, increasing permeability
• High temperatures increase the kinetic energy and phospholipids move further apart. Proteins denature and fall out leaving large gaps

Question 14

What is Cell signalling

Answer 14

• How cells communicate with other cells
• need messenger/ signal molecules
• Needs receptors on cell surface

Question 15

Define Diffusion

Answer 15

• The movement of molecules from a region of higher concentration to a region of lower concentration down a concentration gradient
• Passive process

Question 16

What Factors affect diffusion

Answer 16

• Temperature
• Steepness of gradient
• surface area
• Nature of diffusing molecule

Question 17

Which Particles can diffuse

Answer 17

• Lipid based molecules
• Very small molecules

Question 18

Particles that cant diffuse

Answer 18

• Large molecules
• Charged particles

Question 19

What is Facilitated diffusion

Answer 19

• Passive transport
• Involves channel proteins or carrier proteins
• Occurs down the concentration gradient

Question 20

Define Active transport

Answer 20

Uses energy in the form of ATP to move molecules or ions against a concentration gradient

Question 21

Define Bulk transport

Answer 21

• Uses membranes to transport large amounts of materials
• Needs ATP
• Two types: Endocytosis (Entering) and exocytosis (Exiting)

Question 22

Define Osmosis

Answer 22

The movement of water molecules from a region of higher water potential to a region of lower water potential down a water potential gradient, across a partially permeable membrane

Question 23

What occurs in a Isotonic solution

Answer 23

No net movement

Question 24

What occurs in a Hypotonic solution

Answer 24

• Water moves into the cell
• Animal cell bursts (Lysis)
• Haemolysis
• Plant cell becomes turgid
• Doesn’t burst due to cell wall

Question 25

What occurs in a Hypertonic

Answer 25

• Water moves out the cell
• animal cell shrinks
• crenation
• Plant cell becomes flaccid
• Plasmolysis