1.4 Cell transport

Question 1

Simple diffusion

Answer 1

Movement of particles from a region of high concentration to low concentration, down the concentration gradient.

Question 2

Why does diffusion occur?

Answer 2

It is due to the random movement of particles

Question 3

What molecules diffuse simply?

Answer 3

For molecules that are small, uncharged and/or non-polar

Question 4

Does simple diffusion require selectively permeable membrane?

Answer 4

Yes and no. Usually doesn’t but eg. in alveoli it is required for gases

Question 5

Factors that affect simple diffusion

Answer 5

• Temperature: Higher = faster diffusion
• Surface area: Increase allows more molecules to diffuse
• Concentration gradient: Bigger gradient, faster diffusion
• Size of particles: Smaller ones diffuse faster

Question 6

How is facilitated diffusion different?

Answer 6

Requires channel proteins or carrier proteins. Size and shape are specific to molecules being transported. For molecules that are too big, polar or charged

Question 7

Example of facilitated diffusion

Answer 7

Function of neurons: Movement of K+ ions in neurons during generation of an action potential.

Question 8

Osmosis

Answer 8

Passive movement of water molecules from region of lower solute conc. to higher solute conc. across a partially permeable membrane

Question 9

How is osmosis different from diffusion?

Answer 9

Only involves water molecules

Question 10

Why do tissues (eg. transplant operations) need to be kept in saline solutions?

Answer 10

Osmolarity of saline solution must be same as that of cytoplasm in cells of tissue to prevent osmosis that would damage the cells

Question 11

3 terms for differences in solute concentrations between two solutions

Answer 11

Hypertonic, isotonic, hypotonic

Question 12

Hypertonic

Answer 12

When there is higher conc. of solutes

Question 13

Hypotonic

Answer 13

When there is less conc. of solutes (eg. more water, less ions)

Question 14

Relation b/w hypertonic and hypotonic

Answer 14

Relative relationship. Water always moves by osmosis from hypotonic solution to hypertonic solution

Question 15

Isotonic

Answer 15

When conc. of solutes is equal

Question 16

Placing a red blood cell in a hypotonic solution

Answer 16

Water will move into cell and cause it to swell. Eventually it will burst

Question 17

Placing a red blood cell in a hypertonic solution

Answer 17

Water will move out of the cell and it will shrivel up.

Question 18

Placing a red blood cell in an isotonic solution

Answer 18

No net movement of water

Question 19

Active transport

Answer 19

Movement of particles across membranes, using energy in the form of ATP

Question 20

Why is ATP required for active transport?

Answer 20

To move substances against the concentration gradient (lower to higher conc.)

Question 21

Why do roots in plants use active transport?

Answer 21

Minerals are in lower concentration in the soil so they can’t diffuse naturally. Hence roots use energy to move these substances in.

Question 22

Active transport by Na+/K+ pumps

Answer 22

1. Pump opens to inside of axon and three Na+ ions enter pump and attach to their binding sites
2. ATP donates phosphate group causing protein to change shape expelling Na+
3. Two K+ ions attach to pump which releases phosphate
4. Pumps opens to inside of axon again and expels K+
5. Cycle is repeated

Question 23

2 stages of endocytosis

Answer 23

Phagocytosis and pinocytosis

Question 24

Difference between phago/pinocytosis

Answer 24

Pinocytosis is taking in of liquid substances by cells. Phagocytosis is absorption of solids

Question 25

Example of phagocytosis (hint: WBC)

Answer 25

When white blood cell or phagocyte engulfs a pathogenic microbe

Question 26

Endocytosis

Answer 26

Cellular process where cells take in molecules or substances from outside of cell by engulfing

Question 27

Why is endo and exocytosis important?

Answer 27

Critical to survival since many important molecules cannot normally pass through cell’s hydrophobic plasma membrane

Question 28

Exocytosis

Answer 28

Ejection of waste products from inside of cell

Question 29

Can exocytosis also include useful substances?

Answer 29

Yes. One example could be release of hormones

Question 30

2 types of exocytosis

Answer 30

Excretion and secretion

Question 31

Excretion (exocytosis)

Answer 31

Undigested remains after phagocytosis that are not useful are ejected

Question 32

Secretion (exocytosis)

Answer 32

Proteins synthesized by ribosomes on rER are passed to Golgi via vesicles to be processed and packaged before more vesicles fuse with plasma membrane for secretion

Question 33

Role of vesicles

Answer 33

Allows cells to move molecules around inside the cell.

Question 34

IV and DV in a osmosis experiment to test which solution is hypertonic and hypotonic

Answer 34

IV: Concentration of solution (eg. NaCl)
DV: Length or percentage change in mass of eg. plant tissue or potato tube

Question 35

Difference between primary and secondary active transport

Answer 35

Primary requires ATP while secondary uses energy produced when a solute moves down the (electrochemical) concentration gradient