1.4 Membrane Transport

Question 1

Essential idea

Answer 1

Membranes control the composition of cells by passive and active transport

Question 2

Diffusion

Answer 2

The net movement of particles from an area of high to low concentration facilitated by kinetic energy of particles

Question 3

Concentration gradient

Answer 3

The difference in concentration between two locations

Question 4

Factors that influence diffusion rates

Answer 4

• temperature (high = fast)
• length of diffusion path (short = fast)
• surface area (more = fast)
• particle size (small = fast)
• concentration gradient (bigger = fast)

Question 5

Active transport

Answer 5

Movement of substances across selectively permeable membrane that involves the use of energy (ATP)

Question 6

Passive transport

Answer 6

The movement of particles through a semi-permeable membrane that does not require energy (e.g diffusion or facilitated diffusion)

Question 7

Osmosis

Answer 7

The movement of water through a semi-permeable membrane from low solute concentration to high solute concentration

Question 8

Process of cellular osmosis

Answer 8

Water cannot diffuse through the cell membrane due to it’s size and the presence of the hydrophobic lipid center, instead water travels through the membrane via the integral protein channel aquaporin

Question 9

Hyper-tonic

Answer 9

A state of osmolarity wherein a cell is plasmalysed due to a high solute concentration and a low water concentration. When cells are hyper-tonic water flows into them

Question 10

Hypotonic

Answer 10

State of osmolarity wherein the concentration of a solute is lower inside the cell than outside the cell, leading the cell to become turgid

Question 11

Isotonic

Answer 11

State of osmolarity wherein the cell is in equilibrium and its solute concentration is balanced in and out of the cell, in this state cells are flaccid

Question 12

Osmolarity

Answer 12

Referring to the concentration of a solution and the number of solute particles per liter of solvent

Question 13

Facilitated diffusion

Answer 13

The movement of large or polar models that can’t pass through the cell membrane via protein channels. The direction of facilitated diffusion depends on the concentration gradient

Question 14

Primary active transport

Answer 14

The movement of large and polar molecules against a concentration gradient that requires the use of carrier proteins and energy

Question 15

Secondary active transport

Answer 15

Transport of molecules using energy derived from primary active transport against concentration gradient

Question 16

Endocytosis

Answer 16

The process by which a cell taken in an external substances by an inward pouching of the membrane to form a vesicle

Question 17

Vesicles

Answer 17

Small spherical packages often found near the RER and Golgi apparatus that carry substances in, out and around the cell

Question 18

Exocytosis

Answer 18

The secretion of a substance from a cell when a vesicle joins with the plasma membrane

Question 19

Consecutive secretion

Answer 19

Secretion that occurs continually to maintain homeostasis

Question 20

Regulated secretion

Answer 20

Secretion of substances that occurs in response to a specific trigger

Question 21

Phagocytosis

Answer 21

Variation of endocytosis where cell takes in solid particles (cell eating)

Question 22

Pinocytosis

Answer 22

Variation of endocytosis wherein a cell takes in extra cellular fluid (cell drinking)

Question 23

Process of endocytosis

Answer 23

• vesicle approaches membrane, the membranes of both are phospholipid bilayers meaning they share the same proteins
• membrane fluidity facilitates the fusion of the cell and vesicle membranes
• a temporary intermediate structure is formed when there is a point of contact consisting of a single phospholipid bilayer
• membrane pores opens, allowing the contents of the vesicle to pass through
• vesicle membrane then joins cell membrane
• at no point is either membrane broken

Question 24

Reasons for membrane transport

Answer 24

• take in molecules like glucose
• expel waste
• cell defense
• cellular homeostasis

Question 25

Tissue and organ storage

Answer 25

Tissue needs to be kept in saline solution for storage. The osmolarity of the saline solution must be identical to the cytoplasm of the tissue so that no water can be absorbed into or out of the tissue, disrupting the homeostasis

Question 26

Process of active transport

Answer 26

• molecule or ion enters open part of carrier protein
• carrier protein is activated by ATP
• protein changes shape to allow molecule to travels through protein
• ADP and molecule/ion is expelled from the protein
• protein changes back to original state and process repeats

Question 27

Process of sodium-potassium ion pump

Answer 27

• pump opens on inside, three sodium ions attach
• ATP triggers protein to reconfigure and expel sodium
• 2 potassium ions attach, triggering the release of the phosphate molecule
• release of phosphate reconfigures protein back to original protein, releasing potassium
• process repeats
• used to maintain resting potential in the cell