4.2 Cell transport mechanisms

Question 1

What does a glycoprotein do?

Answer 1

often acts as antigens that are important for cell recognition or as receptors for hormones / neurotransmitters

this sets up a cascade of reactions within the cell

Question 2

What are peripheral proteins?

Answer 2

may be enzymes - can be involved in regulating transport e.g. by cell signaling

Question 3

What are integral proteins?

Answer 3

the main transport system of the membrane forming either hydrophilic channels (permanent pores) or other transport mechanisms

Question 4

What is diffusion?

Answer 4

movement of particles in a liquid or gas down a concentration gradient through random movements

Question 5

What can diffuse through a cell membrane?

Answer 5

small particles e.g. oxygen and carbon dioxide

Question 6

What is facilitated diffusion?

Answer 6

diffusion that takes place through carrier proteins or protein channels

only possible because of the protein lined pores of the cell membrane

Question 7

What is osmosis?

Answer 7

the movement of particles in a liquid (usually water) from an area of high concentration to an area of low concentration, down a concentration gradient, through a partially permeable membrane

Question 8

What is endocytosis?

Answer 8

movement of large molecules into the cell through vesicle formation

Question 9

What is exocytosis?

Answer 9

movement of large molecules out of the cell through vesicle formation

Question 10

What is active transport?

Answer 10

the movement of substances across a cell membrane, against a concentration gradient, using ATP

Question 11

How does the solubility of a molecule affect the way its transported?

Answer 11

substances that dissolve in lipids can easily pass through cell membranes
and water acts as a solvent for ionic species

Question 12

How does the size of a molecule affect the way its transported?

Answer 12

small molecules can freely diffuse across cell membrane
large molecules require facilitated diffusion - channel proteins and carrier proteins

Question 13

How does the charge of a molecule affect the way its transported?

Answer 13

charged particles require specific channel proteins e.g. sodium ion channel
some channels are only open if a specific molecule/electric charge is present

Question 14

What is osmotic concentration?

Answer 14

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

Question 15

What is pressure potential?

Answer 15

a measure of the inward pressure exerted by the plant cell wall on the protoplasm of a cell, opposing entry of water by osmosis - usually a positive value

Question 16

What does isotonic mean?

Answer 16

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

Question 17

What does hypotonic mean?

Answer 17

a solution where the concentration of the solutes is lower than that in cells

Question 18

What does hypertonic mean?

Answer 18

a solution where the concentration of the solutes is higher than that in cells

Question 19

What does it mean if a plant is turgid (turgor)?

Answer 19

state of a plant cell wall 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 20

What is turgor pressure?

Answer 20

unit (P)
a measure of the inward pressure exerted by the plant cell wall on the protoplasm of the cell as the cell contents expands and press outwards, a force opposing the entry of water by osmosis

Question 21

What is incipient plasmolysis?

Answer 21

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

Question 22

What is plasmolysis?

Answer 22

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

Question 23

What is water potential?

Answer 23

unit (Ψ)
a measure of the potential for water to move out of a solution by osmosis

Question 24

What is osmotic potential?

Answer 24

unit (π)
a measure of the potential for a solution to cause water to move into the cell across a partially permeable membrane as a result of dissolved solutes

Question 25

What is the equation for water potential?

Answer 25

water potential (Ψ) = turgor pressure (P) + osmotic potential (π)

Question 26

Describe the role of ATP in active transport?

Answer 26

the enzyme ATPase catalyzes the hydrolysis of ATP into ADP and a phosphate to provide energy

Question 27

How are large molecules transported through vesicle formation?

Answer 27

a form of endocytosis could have occurred:
- phagocytosis - when a cell engulfs something large and encloses it into a vesicle
- pinocytosis - when cells take in tiny amounts of extracellular fluid into vesicles
- exocytosis

Question 28

How does the hydrolysis of ATP provide an accessible energy supply for biological processes?

Answer 28

ATPase catalyzes hydrolysis of ATP
- breaking 1 bond and forming 2 more to provide energy needed to move carrier systems in the membrane or release transported substances

Question 29

What does the phosphorylation of ADP to _ _ _ require?

Answer 29

energy
to form ATP