1.3 membrane structure

Question 1

Amphipathic

Answer 1

Molecule that has hydrophobic and hydrophilic regions.

Question 2

Permeability

Answer 2

The rate of passive diffusion of molecules through the membrane, which depends on the electric charge, size, and polarity of the molecule.

Question 3

Davson-Danielli model

Answer 3

Model of the cell membrane in which the phospholipid bilayer is between two layers of protein.

Question 4

Fluid mosaic

Answer 4

Current model of membrane structure that incorporates a ‘fluid mosaic’ structure in which the phospholipids are free to move in each of the two layers of the bilayer, the proteins are also able to move.

Question 5

Singer-Nicolson model

Answer 5

A model conceived by S.J. Singer and Garth Nicolson in 1972 to describe the observed structural features of biological membranes.

Question 6

Fluidity

Answer 6

Refers to the viscosity of a lipid bilayer of the membrane that allows the phospholipids to flow over each other.

Question 7

Glycoproteins

Answer 7

Proteins that contain oligosaccharide chains.

Question 8

Hormone-binding sites

Answer 8

Proteins on the outside of the membrane that allow specific hormones to bind.

Question 9

Hydrophilic

Answer 9

Molecules that are attracted to water.

Question 10

Hydrophobic

Answer 10

Molecules that are not attracted to water but are attracted to each other.

Question 11

Integral proteins

Answer 11

Proteins embedded in the phospholipid bilayer.

Question 12

Peripheral proteins

Answer 12

Proteins on the surface of the plasma membrane.

Question 13

Phospholipid bilayer

Answer 13

Two layers of phospholipids arranged so that their hydrophobic tails are projecting inwards while their polar head groups are on the outside surfaces.

Question 14

Phospholipids

Answer 14

A lipid consisting of a glycerol bound to two fatty acids and a phosphate group.

Question 15

Transport pumps

Answer 15

Proteins in the plasma membrane use energy to transport substances across the membrane against the concentration gradient.

Question 16

Bilayer

Answer 16

Two rows of phospholipids, with the fatty acids pointing towards each other and the phosphates on the outside.

Question 17

Freeze fracture

Answer 17

When cells are rapidly frozen and then fractured to split the membrane between the bilayer.

Question 18

Cholesterol

Answer 18

A lipid that reduces membrane fluidity and permeability to some solutes.

Question 19

Electron carriers

Answer 19

Proteins arranged in chains on the membrane to allow the transfer of electrons from one carrier to another.