1.3 & 1.4 Membrane structure

Question 1

Phospholipid bilayer

Answer 1

Tails are hydrophobic (Non polar)

Head is hydrophylic (polar)

Can be saturated or unsaturated

unsaturated has a bend

Question 2

Bilayer

Answer 2

prevents macromolecules and polar molecules form getting into the cell

Question 3

Types proteins imbedded in the phospholipid bilayer

Answer 3

Can be intergral, channel or peripheral proteins

peripheral = on sides of bilayer

Channel = through and acts as channel

Intergral = permanantly imbeded and goes through bilayer or on one side

Question 4

Roles of membrane proteins

Answer 4

• Hormone binding sites
• enzymes
• e^- carriers
• channels for passive transport
• Cell to cell regognition
• receptors for neurontransmitters

Question 5

Glycolipids

Answer 5

Carbohydrates attatched to a lipid with a glycocidic bond (covalent bond of a carbohydrate to another molecule)

Allows cell to cell recognition or to attatch and form tissues

Question 6

Cholesterol

Answer 6

Needed in cells to regulate fluidity of membrane (Not too stiff, not too liquidy)

• Too liquid allows too many things into and out of the cell

Is a steroroid

Only in animal cells

Question 7

Singer- Nicholson (Fluid mosaic model)

Answer 7

Question 8

Florescent antibody tagging

Answer 8

Florescent markers attatch to antibodies to identify specific cells when they combine

Question 9

Dave-Danelli model

And the freezing bit

Answer 9

Black outside & inside layer are proteins

Inside the black is a phospolipid bilayer

There were pores inbetween that allowed substances to diffuse into and out of the cell.

FREEZING:

• When the cell was frozen, bumps were shown, these bumps were proteins and showed an irregular surface

Question 10

Why is SA/V important

Answer 10

smaller the object, the larger the SA/V ratio

Question 11

Simple Diffusion vs Facilitated Diffusion

Answer 11

High concentration to low concentration

Rate of diffusion is impacted by temp. pH. and size of molecule being dissolved.

Simple = passive (down conc. gradient)

Facilitated = Passive transport for larger molecules

Question 12

Osmosis

Answer 12

When the solute is too large to pass through the membrane to create equilibrium

Lower solute to higher solute

No energy needed (passive)

Higher solute to solvent ratio = Hypertonic

Less = Hypotonic

If equal = Isotonic

Question 13

Tonicity

Answer 13

The relative amount of solute in the solution, used to compare solutions

Question 14

Passive and Active transport

Answer 14

Passive = no energy

Active = energy required, against concentration gradient (uses ATP)

Channel proteins allow passive diffusion

Intergral proteins change shape when protein changes shape, is active transport

Question 15

Sodium potassium pump

Answer 15

Uses 3 sodium ions to allow 2 potassium ions in, and vice verca

Also uses ATP

Question 16

Bulk transport

Answer 16

Requires ATP

Mass movement of:

Endocytosis = Into cell

Exocytosis = Exit cell

Phagocytosis = eat a whole

Pinocytosis = drink/ engulf a liquid

Question 17

Amphipathic properties

Answer 17

phospholipids have hydrophilic and hydrophobic properties

Question 18

Evidence from electron microscopy that led to the proposal of the Davson-Danielli model

Answer 18

• When viewed under a transmission electron microscope, membranes exhibit a 3 layer appearance.
• proposed a model whereby two layers of protein flanked a central phospholipid bilayer
• The model was described as a ‘lipo-protein sandwich’, as the lipid layer was sandwiched between two protein layers

Question 19

falsification of the Davson-Danielli model that led to the Singer-Nicolson model

Answer 19

Evidence:
- Membrane proteins were discovered to be insoluble in water (indicating hydrophobic surfaces) and varied in size
- Fluorescent antibody tagging of membrane proteins showed they were mobile and not fixed in place
- Freeze fracturing was used to split open the membrane and revealed irregular rough surfaces within the membrane