2A Cell Membranes

Question 1

When does passive transport take place?

Answer 1

When there is a connection, pressure or electrochemical gradient, and no energy from the fell is involved

Question 2

Active transport

Answer 2

• involves moving substances across cell membranes using adenosine triphosphate which is produced during cellular respiration
• it always involves carrier proteins

Question 3

Give 2 examples of particles that diffuse across membranes by diffusion

Answer 3

• oxygen
• carbon dioxide

Question 4

cell membrane

Answer 4

the selectively permeable membrane which surrounds the cytoplasm of a cell, acting as a barrier between the cell contents and their surroundings

Question 5

phospholipids

Answer 5

chemicals in which glycerol bonds with two fatty acids and an inorganic phosphate group

Question 6

hydrophilic

Answer 6

a substance with an affinity for water that will readily dissolve in or mix with water

Question 7

polar lipids

Answer 7

lipids with one end attached to a polar group so that one end of the molecules is hydrophilic and one end is hydrophobic

Question 8

hydrophobic

Answer 8

a substance that tends to repel water and that will not mix with or dissolve in water

Question 9

monolayer

Answer 9

a single closely packed layer of atoms or molecules

Question 10

micelles

Answer 10

a spherical aggregate of molecules in water with hydrophobic areas int eh middle and hydrophilic ares outside

Question 11

endocytosis

Answer 11

the movement of large molecules into cells through vesicle formation (active transport)
- phagocytosis
- pinocytosis

Question 12

exocytosis

Answer 12

the movement of large molecules out of cells by fusing of a vesicle containing the molecules with the surface cell membrane

the process requires ATP

Question 13

osmotic concentration

Answer 13

a measure of the concentration of the solutes in a solution that have an osmotic effect

Question 14

isotonic solution

Answer 14

a solution in which the osmotic concentration of the solutes is the same as that in the cells

Question 15

hypotonic solution

Answer 15

a solution in which the osmotic concentration of solutes is lower than that in the cell contents

Question 16

hypertonic solution

Answer 16

a solution in which the osmotic concentration of solutes is higher than that in the cell contents

Question 17

turgor

Answer 17

the state of a plant cell when the solute potential causing water to be moved into the cell by osmosis is balanced by the force of the cell wall pressing on the protoplasm

Question 18

hydrostatic pressure

Answer 18

the pressure exerted by a fluid in an equilibrium

Question 19

incipient plasmolysis

Answer 19

the point at which so much water has moved out of the cell by osmosis that turgor is lost and the cell membrane begins to pull away form the cell wall as the protoplasm shrinks

Question 20

plasmolysis

Answer 20

the situation when a plant cell is placed in hypertonic solution when so much water leaves the cell by osmosis that the vacuole is reduced and the protoplasm is concentrated and shrinks away form the cell walls

Question 21

solute

Answer 21

a substance that can be dissolved in a solution by a solvent

Question 22

carrier protein

Answer 22

protein that moves a substance through the membrane in active transport using energy from the breakdown of ATP or in facilitated diffusion down a conc. gradient

Question 23

phagocytosis (cell eating)

Answer 23

the active process when a cell engulfs something relatively large such as a bacterium and encloses it in a vesicle

Question 24

pinocytosis (cell drinking)

Answer 24

the active process by which cells take in tiny amounts of extracellular fluid by tiny vesicles