Keywords

Question 1

Plasma Membrane

Answer 1

Membranes consisting of a phospholipid bilayer found around and within all cells. The cell surface membrane is the plasma membrane that surrounds cells.

Question 2

Phospholipid

Answer 2

Triglyceride in which one of the three fatty acid molecules is replaced by a phosphate molecule. Phospholipids are important in the structure an functioning of plasma membranes

Question 3

Bilayer

Answer 3

A membrane consisting of two layers of phospholipids

Question 4

Channel Protein

Answer 4

A protein completely spanning the phospholipid bilayer which forms water-filled tubes to allow water-soluble ions to diffuse across the membrane.

Question 5

Carrier Protein

Answer 5

A protein completely spanning the phospholipid bilayer which bind to ions or molecules then change shape in order to move these molecules across the membrane.

Question 6

Glycoprotein

Answer 6

Carbohydrate chains attached to a protein (often extrinsic) which are part of the cell surface membrane. They act as recognition sites, help cells to attach to one another and allows cells to recognise one another

Question 7

Glycolipid

Answer 7

A carbohydrate covalently bonded with a lipid. They act as recognition sites, help maintain stability of the embarked and help cels attach to one another

Question 8

Cholesterol

Answer 8

Lipid that is an important component of cell - surface membranes because it adds strength. Excess in the blood can lead o atheroma

Question 9

Permeability

Answer 9

How permeable a substance is depends on the size, polarity and charge of the molecule. If it is small, non-polar and a fat soluble it is very permeable and can pass through the cell membrane

Question 10

Fluid Mosaic Model

Answer 10

The arrangement of the various molecules of the cell surface membrane. Fluid because the individual phospholipid molecules can move relative to one another and mosaic because the proteins vary in shape, size and pattern

Question 11

Diffusion

Answer 11

The net movement of molecules from a region of high concentration to a region of low concentration. It is passive (does not require energy)

Question 12

Facilitated Diffusion

Answer 12

Diffusion involving the presence of carrier proteins to allow the passive movement of substances (normally large, polar or charged molecules) across plasma membranes

Question 13

Osmosis

Answer 13

The passage of water from a region where there is a higher water potential to a region where there is a lower water potential through a partially permeable membrane

Question 14

Water Potential

Answer 14

The pressure created by water molecules. It is the measure of the extent to which a solution gives out water. The greater the number of water molecules present, the higher (less negative) the water potential. Pure water has a water potential of zero.

Question 15

Isotonic

Answer 15

A solution which has the same water potential as the cell within it

Question 16

Active Transport

Answer 16

Movement of a substance from a region where it is in a low concentration to a region where it is in a high concentration. The process requires the expenditure of metabolic energy in the form of ATP

Question 17

Co Transport

Answer 17

The transport of one substance coupled with the transport of another substance across a plasma membrane in the same direction through te same protein carrier.