Forces Acting Across Membrane

Question 1

Phospholipid bilayer

Answer 1

A semi-permeable membrane. Hydrophilic heads face the ECF and hydrophobic tails face away from the ECF.

Question 2

Cholesterol

Answer 2

Selectively dispersed molecules between phospholipids which help to keep the membrane from becoming stiff by stopping the phospholipids being too close together.

Question 3

Glycolipids

Answer 3

Located on the cell membrane with a carb attached aiding cell recognition.

Question 4

Peripheral membrane proteins

Answer 4

Exterior to and connected to the membrane by interaction with other proteins.

Question 5

Integral membrane proteins

Answer 5

Inserted into the membrane and most pass through with portions on both sides.

Question 6

Structural proteins

Answer 6

Give the cell support and shape

Question 7

Receptor proteins

Answer 7

Help cell communication to the external environment through the use of hormones, neurotransmitters and other signalling molecules.

Question 8

Transport proteins

Answer 8

Transport molecules across the cell membrane through facilitated diffusion e.g. globular proteins

Question 9

Glycoproteins

Answer 9

Cell to cell communication and molecule transport across the membrane.

Question 10

Passive diffusion

Answer 10

The passing of small molecules through the cell membrane down a concentration gradient, no ATP required.

Question 11

Facilitated diffusion

Answer 11

Requires carrier proteins embedded in the membrane to allow specific substances to pass through the membrane.

Question 12

List factors which favour diffusion through the membrane.

Answer 12

1. High to low concentration gradient
2. Small molecules
3. Uncharged molecules
4. Lipid soluble

Question 13

Ion channels

Answer 13

A transmembrane channel responsible for the passive transport of ions.

Question 14

Voltage-gated channels

Answer 14

Transmembrane channels activated by changes in the electrical membrane potential. Typically closed at RMP and open upon depolarisation.

Question 15

Ligand-gated/ionotropic channels

Answer 15

Open to allow ions to pass through in response to the binding of a chemical messenger.

Question 16

Electrochemical gradient

Answer 16

A difference in solute concentration and charge across a membrane. The electrochemical potential for an ion to move across a membrane.

Question 17

Ion balance across the membrane

Answer 17

Cell/ECF
K+/k+
na+/NA+
cl-/CL-
ca2+/CA2+

Question 18

Carrier mediated transport systems

Answer 18

The movement of molecules across the cell membrane via special transport proteins that are embedded within the cell membrane. e.g. active transport or facilitated diffusion.

Question 19

Osmosis

Answer 19

The movement of water from a low concentration to a high concentration. If the concentration is equal water movement will be the same in both directions.

Question 20

Osmolarity

Answer 20

The concentration of solution expressed as the total number of solute particles per litre (Osm/L)

Question 21

Tonicity

Answer 21

The ability of a solution to cause a cell to gain or lose water. Takes into account the number of non-penetrating particles in a solute.

Question 22

Osmolality

Answer 22

A measure of the osmoles of solute per Kg of solvent

Question 23

Effective osmole

Answer 23

An expression of the concentration of effective osmoles in a solution. It contributes to tonicity.

Question 24

Isosmotic

Answer 24

Having the same total osmotic pressure/osmolality as another fluid.

Question 25

Isotonic

Answer 25

Total molar concentration of dissolved solutes is the same in both directions

Question 26

Endocytosis

Answer 26

The taking in of matter by a cell by invagination of its membrane to form a vesicle

Question 27

Exocytosis

Answer 27

Process by which a cell transports secretory products through the cytoplasm to membrane.