OCR ALevel Biology - Module 2 - Definitions - Topic 2.5 : Biological Membranes

Question 1

What is active transport?

Answer 1

The active movement of substances from a low concentration to a higher concentration (up their concentration gradient) with the use of energy in the form of ATP.

Question 2

What does amphipathic mean?

Answer 2

A molecule with both hydrophobic and hydrophilic parts.

Question 3

What is cell lysis?

Answer 3

The bursting of a cell, particularly after the uptake of too much water into an animal cell through osmosis.

Question 4

What is the role of cholesterol in the membrane?

Answer 4

A mostly hydrophobic molecule that sits in the hydrophobic portion of the membrane and regulates membrane fluidity.

Question 5

What is crenation?

Answer 5

The shrinking of a cell when placed in a hypertonic solution due to large amounts of water moving out of the cell through osmosis.

Question 6

What is endocytosis?

Answer 6

The bulk uptake of substances into a cell by invagination of the membrane to form a vesicle trapping the substances inside the cell with the use of energy in the form of ATP.

Question 7

What is exocytosis?

Answer 7

The bulk transport of substances out of a cell using a vesicle that fuses with the plasma membrane using energy in the form of ATP.

Question 8

What is facilitated diffusion?

Answer 8

The net movement of substances from a high concentration to a lower concentration (down their concentration gradient) through transport proteins without the use of energy.

Question 9

What is the fluid mosaic model?

Answer 9

A model that describes membrane structure as a sea of mobile phospholipids studded with various proteins.

Question 10

What does hydrophilic mean?

Answer 10

A molecule which is attracted to water.

Question 11

What does hydrophobic mean?

Answer 11

A molecule which repels water.

Question 12

What is an integral membrane protein?

Answer 12

A type of protein bound to the membrane with strong interactions.

Question 13

What is osmosis?

Answer 13

The net movement of water molecules across a partially permeable membrane from a region of high water potential to a region of lower water potential without the use of energy.

Question 14

What is a peripheral membrane protein?

Answer 14

A type of protein that is weakly bound to the surface of the membrane.

Question 15

What is phagocytosis?

Answer 15

The ingestion of solid material (particularly pathogens and foreign material) by phagocytic cells.

Question 16

What is a phospholipid?

Answer 16

A type of lipid formed by the condensation of one molecule of glycerol, two molecules of fatty acid and a phosphate group.

Question 17

What is pinocytosis?

Answer 17

The bulk uptake of liquids into the cell using energy in the form of ATP.

Question 18

What is plasmolysis?

Answer 18

The effect produced by placing plant cells in a hypertonic solution causing the cell to shrivel from water loss, resulting in the membrane pulling away from the rigid cell wall.

Question 19

What is simple diffusion?

Answer 19

The spreading out of substances from a high concentration to a lower concentration (down their concentration gradient) without the use of energy.

Question 20

What does turgid mean?

Answer 20

A term used to describe a cell that is swollen due to large amounts of fluid uptake.

Question 21

What is water potential?

Answer 21

A measure of the tendency of water molecules to move from one area to another measured in kilopascals (kPa) and given the symbol Ψ.