1.4 Membrane Transport

Question 1

What is simple diffusion?

Answer 1

Particles passing between phos. molecules, through the membrane. Non-polar molecules diffuse easily, small polar molecules slower. PASSIVE - no energy required.
Simple molecules (O2, H2O,etc.)

Question 2

What is facilitated diffusion?

Answer 2

Diffusion through protein channels. Channels are specific to certain molecules b/c of size and shape of channel interior. PASSIVE - no energy required.
More complicated molecules, sugars and amino acids

Question 3

What is diffusion (in general)

Answer 3

Movement of particles from an area of high concentration to an area of low concentration. Due to cont. random motion of particles. All diffusion is PASSIVE.

Question 4

What is osmosis?

Answer 4

Diffusion of water across a semi-permeable membrane due to differences in solute concentration. H2O will pass through membrane to dilute solute and make inside and outside of cell equal conc. PASSIVE.

Question 5

What is active transport?

Answer 5

Movement against the conc. gradient (low conc. to high conc.). REQUIRES ENERGY usually in form of ATP. Active transport is carried out by membrane proteins (protein pumps)

Question 6

How do particles move across membranes?

Answer 6

Simple diffusion, facilitated diffusion, osmosis, and active transport

Question 7

How does active transport work?

Answer 7

Particle enters pump from side w low conc.. Particle binds to specific site (only one type can bind). Energy from ATP is used to change shape of pump. Particle released on side w higher conc. and pump returns to original shape.

Question 8

What are the three types of solutions?

Answer 8

Isotonic, hypotonic, hypertonic.

Question 9

What is an isotonic solution?

Answer 9

Equal [solute] on each side of membrane so water flows equally in both directions

Question 10

What is a hypotonic solution?

Answer 10

Lesser [solute] outside cell than inside to water flow into cell to try to equalize it. (Water flows in to dilute [solute] inside cell, cell gets large and might explode)

Question 11

What is a hypertonic solution?

Answer 11

Higher [solute] outside cell than inside so water flows out of cell to try to equalize it. (Water flows out to dilute [solute] outside cell, cell shrinks and shrivels)

Question 12

What type of solution do plant cells need? What type of solution do animal cells need?

Answer 12

Plant cells need hypotonic solutions so that there is enough H2O for the cell. The cell is not at risk of exploding because of the strong cell wall. Animal cells need to be in isotonic solutions since they do not have a cell wall and will explode if too full of H2O.

Question 13

Describe endocytosis.

Answer 13

Endocytosis occurs when a membrane encloses a particle. Fluidity of membrane allows the membrane to move, it sinks inwardly and seals back on itself to create a vesicle. Inner layer of original membrane is outer layer of vesicle and vice versa. Vesicle breaks away and moves to cytoplasm. Requires ENERGY.

Question 14

What is exocytosis?

Answer 14

Movement of particles out of the cell, opposite of endocytosis.

Question 15

How are vesicles used to transport materials secreted by a cell.

Answer 15

Vesicles formed from rER transport proteins to G app. Vesicles fuse w membrane of G app. Proteins processed. Vesicles move through cytoplasm. Fuse w membrane. Exocytosis. Vesicles used to secrete substances such as hormones and digestive enzymes. Can contain cell products other than protein.

Question 16

Distinguish between active and passive movements of materials across membranes, using named examples.

Answer 16

Passive: (facilitated) diffusion, osmosis, does not require energy, down conc gradient, no pump, e.g. oxygen through mem.
Active: active transport, exocytosis, pinocytosis, phagocytosis, requires ATP, against conc gradient, requires pumps, e.g. glucose through active transport

Question 17

What are the types of endocytosis?

Answer 17

Phagocytosis: cell eating, Pinocytosis: cell drinking, Recepto-mediated endocytosis: specific particles

Question 18

Describe how the sodium-potassium pump in neurons works.

Answer 18

Neuron at rest positive outside negative inside. Positives and negatives switch when Na comes in. K goes out to switch them back. Pump then works to replace Na into middle and K into outside. Pump is ACTIVE.

Question 19

How are isotonic solutions used in medical procedures?

Answer 19

IV to rehydrate. Rinse wounds. Keep damaged skin moist prior to skin grafts. Basis for eye drops. Frozen for packing donor organs for transport.