F211 1.2 - Cell Membranes

Question 1

Active transport

Answer 1

Movement of substances across membranes against their concentration gradient, requiring the use of energy in the form of ATP. Active transport usually involves the use of transport proteins.

Question 2

Affinity

Answer 2

An attractive force between substances or particles.

Question 3

Antigen

Answer 3

A foreign molecule (which may be protein or glycoprotein) that can provoke an immune response. Organisms have antigens on their plasma (cell surface) membranes.

Question 4

Carrier protein

Answer 4

A protein found in membranes, which is capable of carrying a specific molecule or ion through the membrane by active transport.

Question 5

Cell signalling

Answer 5

Processes that lead to communication and coordination between cells. Hormones binding to their receptors on the cell surface membrane are an example.

Question 6

Cell surface membrane

Answer 6

The membrane that surrounds every cell, forming the selectively permeable boundary between the cell and its environment. It is made up of a double layer of phospholipids with embedded proteins.

Question 7

Channel protein

Answer 7

A protein pore that spans a membrane, through which very small ions and water soluble molecules may pass.

Question 8

Cholesterol

Answer 8

A lipid molecule (not a triglyceride) found in all cell membranes and involved in the synthesis of steroid hormones.

Question 9

Cohesion

Answer 9

The attraction between water molecules due to hydrogen bonding.

Question 10

Concentration gradient

Answer 10

The difference in concentration of a substance between two regions.

Question 11

Cotransporter protein

Answer 11

A protein in a cell membrane that allows movement of one molecule when linked to the movement of another molecule in the same direction by active transport.

Question 12

Crenation

Answer 12

State of animal cells when they have been immersed in a solution of lower water potential and have lost water by osmosis. They become shrivelled.

Question 13

Cytokines

Answer 13

Hormone-like proteins produced by vertebrate (including mammalian) cells, which are used for communication between cells, allowing some cells to regulate the activities of others.

Question 14

Diffusion

Answer 14

The net movement of molecules or ions in a gas or liquid from an area of high concentration to an area where they are less concentrated.

Question 15

Diffusion gradient

Answer 15

The gradient in molecular concentration (the difference in concentrations) that allows diffusion to occur.

Question 16

Endocytosis

Answer 16

The process of taking materials into a cell by surrounding them with part of the plasma membrane, which then pinches off to form a vesicle inside the cell. This is an active process requiring ATP.

Question 17

Exchange surface

Answer 17

A specialised area adapted to make it easier for molecules to cross from one side of the surface to the other.

Question 18

Exocytosis

Answer 18

The process of removing materials from the cell by fusing vesicles containing the material with the plasma membrane (cell surface membrane).

Question 19

Facilitated diffusion

Answer 19

The passive movement of molecules across membranes down their concentration gradient, which is aided by transport (carrier) protein molecules. No metabolic energy is required.

Question 20

Flaccid

Answer 20

A term used to describe plant tissue where the cells have lost turgor and are not firm.

Question 21

Fluid mosaic (model)

Answer 21

The model of cell membrane structure proposed by Singer and Nicholson – a phospholipid bilayer with proteins ‘floating’ in it.

Question 22

Gaseous exchange

Answer 22

The movement of gases by diffusion across a barrier such as the atreous wall.

Question 23

Gated channels

Answer 23

Protein channels found in cell membranes, which can be opened or closed in response to cell signals.

Question 24

Haemolysis

Answer 24

(First observed in red blood cells.) The rupturing of animal cell surface membranes and subsequent release of their contents, when animal cells are placed in a solution of higher water potential and water enters by osmosis.

Question 25

Hormone

Answer 25

Chemicals made in endocrine glands that are carried in the blood to target cells/tissues/organs. They act as chemical messengers and are associated with developmental changes of the organism. Most are polypeptides but some are steroids.

Question 26

Hydrogen bond

Answer 26

A weak bond formed when partially positively charged groups come close to partially negatively charged groups. It is seen in water molecules, and in the secondary and tertiary structure of proteins.

Question 27

Hydrophilic

Answer 27

Associating with water molecules easily (water-loving).

Question 28

Hydrophobic

Answer 28

Water-repelling (water-hating).

Question 29

Hydrostatic pressure

Answer 29

Pressure created by a fluid pushing against the sides of a container.

Question 30

Interferon

Answer 30

A group of factors with non-specific antiviral activity. They also affect the immune system.

Question 31

Interleukin

Answer 31

Cell-signalling chemicals. Some are involved in activating cells of the immune system.

Question 32

Ion

Answer 32

An atom (or group of atoms) carrying a positive or a negative charge.

Question 33

Ionic bond

Answer 33

Attraction between oppositely charged ions.

Question 34

Monocytes

Answer 34

Large, phagocytic white blood cell.

Question 35

Monokines

Answer 35

Chemical produced by monocytes to signal to other cells. Also called lymphokines.

Question 36

Neutrophils

Answer 36

Phagocytic white blood cells. They engulf and digest bacteria. Neutrophils have a many-lobed nucleus, and a granular cytoplasm due to the large numbers of lysosomes present.

Question 37

Osmosis

Answer 37

The movement of water molecules from a region of higher water potential to a region of lower water potential across a partially permeable membrane.

Question 38

Partially permeable membrane

Answer 38

A membrane that will allow some molecules to pass through but will not allow some others to pass through.

Question 39

Phagocyte

Answer 39

A cell that can carry out phagocytosis and ingest bacteria or small particles. Macrophages and neutrophils are phagocytes.

Question 40

Phagosome

Answer 40

A vacuole inside a phagocyte which is created by an infolding of the plasma (cell surface) membrane to engulf a foreign particle. The foreign particle is held inside the phagosome.

Question 41

Phospholipid

Answer 41

A molecule consisting of a glycerol molecule, two fatty acid molecules and a phosphate group covalently bonded together. Phospholipids form the basis of cell membranes.

Question 42

Pinocytocis

Answer 42

The process of endocytosis involving the bulk movement of liquids into a cell.

Question 43

Plasma membrane

Answer 43

The membrane that surrounds every cell, forming the selectively permeable boundary between the cell and its environment. It is made up of a double layer of phospholipids with embedded proteins.

Question 44

Plasmolysis

Answer 44

Detachment of the plasma membrane from the cell wall as the cytoplasm shrinks when water is lost from a plant cell.

Question 45

Receptor sites

Answer 45

Protein or glycoprotein molecules on cell surfaces, used for attachment of specific substances such as hormones or viruses.

Question 46

Secretion

Answer 46

The release of a substance made inside the cell using the process of exocytosis.

Question 47

Simple diffusion

Answer 47

The movement of molecules from a region of their higher concentration to a region of their lower concentration.

Question 48

Solute

Answer 48

A solid that dissolves in a liquid.

Question 49

Solute potential (φs)

Answer 49

The component of water potential that is due to the presence of solutes – the potential energy of a solution provided by the solutes.

Question 50

Solution

Answer 50

Liquid with dissolved solids.

Question 51

Solvent

Answer 51

A liquid that dissolves solids.

Question 52

Surface tension

Answer 52

The ‘skin’ on the surface of water formed as a result of hydrogen bonding in water molecules pulling the surface molecules downwards.

Question 53

Surfactant

Answer 53

A chemical that can reduce the surface tension of a film of water.

Question 54

Turgid

Answer 54

Describes a cell that is full of water as a result of entry of water due to osmosis. When the pressure of the cell wall prevents more water entering, the cell is said to be turgid.

Question 55

Water potential (ᵩ)

Answer 55

A measure of the ability of water molecules to move freely in solution. Measures the potential for a solution to lose water – water moves from a solution with high water potential to one of lower water potential. Water potential is decreased by the presence of solutes.