Ch7 Membrane Structure and function

Question 1

Plasma membrane is

Answer 1

selectively permeable, allowing some substances to cross more easily than others.

Question 2

Passive transport

Answer 2

diffusion of a substance across a membrane with no energy investment

Question 3

Osmosis

Answer 3

• The diffusion of water across a selectively permeable membrane

Question 4

Water diffuses across the membrane from

Answer 4

• lower solute concentration to higher solute concentration
• higher water concentration to lower water concentration

Question 5

Tonicity

Answer 5

the ability of a surrounding solution to cause a cell to gain or lose water.

Question 6

Isotonic

Answer 6

no net movement of water across the plasma membrane
- o Water diffuses across the membrane, but at the same rate in both directions

Question 7

hypertonic

Answer 7

the cell loses water to its environment, shrivels, and probably dies
- an increase in the salinity (saltiness) of a lake can kill aquatic animals

Question 8

Hypotonic

Answer 8

water enters the cell faster than it leaves, and the cell swells and lyses (bursts) like an overfilled water balloon

Question 9

Cell survival depends on the balance between

Answer 9

water uptake and loss

Question 10

Organisms without rigid cell walls have what problems?

Answer 10

osmotic problems in either a hypertonic or a hypotonic environment.

Question 11

Osmoregulation

Answer 11

the control of water balance
- an adaptation fro animals and other organisms without rigid cell walls living in hypertonic or hypotonic environments

Question 12

Facilitated diffusion

Answer 12

The passive movement of molecules down their concentration gradient with the help of transport proteins

Question 13

What are the 3 types of transport proteins

Answer 13

Channel proteins, aquaporins, carrier proteins

Question 14

Channel proteins

Answer 14

create a hydrophilic channel that some polar molecules and ions can use as a tunnel through the membrane

Question 15

Aquaporins

Answer 15

facilitate the passage of water molecules in certain cells.

Question 16

Carrier Proteins

Answer 16

hold on to their passengers and change shape in a way that shuttles them across the membrane.

Question 17

Diffusion

Answer 17

the movement of particles of any substance so that they spread out into the available space

Question 18

Active Transport

Answer 18

the movement of a substance across a cell membrane against its concentration or electrochemical gradient, mediated by specific transport proteins and require energy (ATP)

Question 19

Exocytosis

Answer 19

cell secretes molecules by the fusion of vesicles
- to export products

Question 20

Endocytosis

Answer 20

cell takes in molecules and particulat matter by forming new vesicles from the plasma membrane