2.4 Transport Across Membranes

Question 1

importance of transport

Answer 1

Cells need to transport materials in and out of the cell in order to survive

-wastes need to be removed
-nutrients need to enter the cell
-cells need to communicate via chemicals

Some materials enter passively while others need to be transported using energy

Question 2

passive transport

Answer 2

movement of a substance
across the membrane without using energy

-diffusion drives passive transport
-molecules/ions move from HIGH to LOW concentrations

Question 3

types of passive transport

Answer 3

simple diffusion, facilitated diffusion and osmosis

Question 4

facilitated diffusion

Answer 4

use of proteins to help move substances across the membrane

-uses TRANSPORT PROTEINS which provide pathways for movement across membrane

Channel Protein – hydrophilic pathway through membrane

Carrier Protein – physically binds to molecules to aid in transportation

Question 5

Channel protein

Answer 5

hydrophilic pathway through membrane

-used to transport certain ions (ex. Na, K, Cl)
-involved in nerve signals

Question 6

Carrier protein

Answer 6

physically binds to molecules to aid in transportation

-bind to specific substances (ex. amino acids)
-changes shape to help transport substances

Question 7

osmosis

Answer 7

the passive diffusion of water across a membrane

-always moves from an area of LOWER SOLUTE
CONCENTRATION (high water content) to an area of HIGHER SOLUTE CONCENTRATION (low water content)

-therefore SOLUTE (dissolved substances)
CONCENTRATION determines water movement

-the Concentration of Solutes around cells determines their shape

Question 8

hypotonic solution

Answer 8

low concentration of solutes outside cell = water rushes into cell

Question 9

isotonic solution

Answer 9

equal concentration of solutes inside and outside of cell = no net movement of water

Question 10

hypertonic solution

Answer 10

high concentration of
solutes outside cell = water rushes out of cell

Question 11

active transport

Answer 11

the movement of substances
across the membrane using energy

-movement is AGAINST the concentration gradient
-uses ATP to “pump” substances across

Question 12

primary active transport

Answer 12

Move POSITIVELY CHARGED IONS across
membranes

Generally relies upon ATP

Ex. H+, Ca2+, Na+, K+

Helps establish Electrochemical Gradients which
are important in Nerve Functioning (more on this
later on)

Question 13

secondary active transport

Answer 13

Uses energy from the Concentration Gradient built up by Primary Active Transport to transport substances

Question 14

types of secondary active transport

Answer 14

symport and antiport

Question 15

symport

Answer 15

transported substances move in the same direction as ions

Question 16

antiport

Answer 16

transported substances move in the opposite direction as ions

Question 17

exocytosis

Answer 17

Needed to transport substances larger than amino acids/monosaccharides

transport of substances from inside
the cell to outside of the cell using vesicles

Question 18

endocytosis

Answer 18

transport of substances from
outside the cell to inside the cell using vesicles
in one of three distinct but related pathways

Question 19

types of endocytosis

Answer 19

pinocytosis, receptor-mediated endocytosis, phagocytosis

Question 20

Pinocytosis (cell drinking)

Answer 20

brings in fluid along with any molecules inside the fluid

Question 21

Receptor-mediated Endocytosis

Answer 21

has molecules
bind to receptor proteins on the outer surface
before coming into the cell

Question 22

Phagocytosis (cell eating)

Answer 22

brings in solid materials
like bacteria, dead cells, or other foreign material