Module 1.4: Movement Through the Cell Membrane

Question 1

Selective permeability is

Answer 1

characterized by the ability of certain substances to pass through the cell membrane while other molecules cannot.

Question 2

Solute is

Answer 2

the substance being dissolved into another substance

Question 3

Passive transport occurs

Answer 3

when substances move through the membrane without the input of energy.

Question 4

Simple diffusion

Answer 4

best-known passive process

is the tendency for solutes (ions and molecules) to move from an area of high concentration to an area of lower concentration.

Question 5

The concentration gradient refers to

Answer 5

the gradual change in the observed concentration of solutions present between two areas.

Question 6

Osmosis

Answer 6

is the passive diffusion of water (or other solvents) through a selectively permeable membrane.

Question 7

Isotonic

Answer 7

refers to having an equal amount of solute on either side of a membrane.

Question 8

Hypertonic

Answer 8

(the prefix hyper means “above”) solutions contain more solute particles relative to another solution.

Question 9

Hypotonic

Answer 9

(the prefix hypo means “below”) solutions contain fewer solute particles relative to another solution.

Question 10

Filtration

Answer 10

is the movement of fluid through a filtration membrane or small space that contains small openings.

Question 11

Facilitated diffusion

Answer 11

is the diffusion of lipid-insoluble molecules across a membrane.

Question 12

Carrier mediated transport occurs

Answer 12

when a **channel protein **spans the membrane, creating a tunnel like structure that allows specific molecules to pass through via diffusion.

Channel proteins allow polar and charged molecules to bypass the hydrophobic region of the membrane and enter the cytoplasm of the cell.

Question 13

Carrier proteins are

Answer 13

Another example of facilitated diffusion

Question 14

Active transport

Answer 14

occurs when an input of energy is required to move substances through the membrane.

Question 15

The sodium-potassium pump

Answer 15

is an active form of transport used to move sodium ions out of (and potassium ions into) the cell.

Question 16

Secondary active transport

Answer 16

occurs when one molecule, such as sodium, is transported across the membrane thereby providing energy for a second substance, such as glucose, to be transported across the cell membrane.

Question 17

Cotransport is when

Answer 17

the diffusing substance (glucose) moves in the same direction as the transported substance (sodium)

Question 18

Counter transport is

Answer 18

when the diffusing substance moves in the opposite direction as the transported substance (opposite of cotransport)

Question 19

Vesicles

Answer 19

are small membrane-bound organelles used to transport materials within, out of or into a cell.

Question 20

Exocytosis

Answer 20

• (exo- means “going out”)
• requires energy
  *

Question 21

Endocytosis

Answer 21

(the prefix endo means “bringing in”) occurs when a macromolecule outside of the cell is enclosed by a portion of the cell membrane (forming a vesicle) and is transported inside the cell through an energy dependent process.

Question 22

Receptor mediated endocytosis (RME)

Answer 22

involves receptors on the cell membrane binding with specific molecules outside of the cell.

Question 23

Ligands

Answer 23

These external molecules

Question 24

Phagocytosis

Answer 24

is the endocytosis of extremely large objects.

Question 25

Phagosomes

Answer 25

The vesicles formed during phagocytosis

Question 26

Pinocytosis

Answer 26

is the endocytosis of tiny droplets of fluids.

Question 27

Electrical gradients arise from

Answer 27

the electrical charge of the cellular environment created by the repulsion of like charges and the attraction of opposite charges of ions within the environment.

Question 28

This combination of electrical gradients and concentration gradients is called the

Answer 28

electrochemical gradient

Question 29

Membrane channels may be

Answer 29

voltage gated— meaning the electrical potential within the membrane determines whether these channels are open or closed.

Question 30

The resting membrane potential is

Answer 30

when the cell and its extracellular environment are in chemical and electrical equilibrium.

Question 31

Depolarization

Answer 31

a shift in the internal charge to a less negative state