Chapter 4: Membrane Structure and Function

Question 1

What are the parts of a cell membrane?

Answer 1

1. lipids (phospholipids)
2. proteins
3. carbohydrates
4. cholesterol

Question 2

What is the structure of a cell membrane as shown in a fluid-mosaic model?

Answer 2

1. proteins (glycoprotein, integral protein, transmembrane protein)
2. phospholipids
3. hydrophobic and hydrophilic regions
4. carbohydrate side chain

Question 3

What are the functions of the cell membrane?

Answer 3

1. regulates what enters and leaves the cell

2. provides protection and support in the cell

Question 4

What is the permeability of the cell membrane?

Answer 4

selectively permeable–meaning that it differentiates between different types of molecules

Question 5

passive transport

Answer 5

a type of transport that does not require energy; usually involves smaller molecules and moves down the concentration gradient

Question 6

diffusion

Answer 6

the movement of a substance from areas of higher concentration to areas of lower concentration

Question 7

free diffusion

Answer 7

the movement of particles in a random motion through a membrane

Question 8

facilitated diffusion

Answer 8

the movement of particles across the membrane down the concentration gradient assisted by a carrier protein

Question 9

What is the cause of movement in diffusion?

Answer 9

the concentration gradient

Question 10

hypotonic solution

Answer 10

a solution that contains LESS dissolved particles

Question 11

hypertonic solution

Answer 11

a solution that contains MORE dissolved particles

Question 12

isotonic solution

Answer 12

a solution that has EQUAL concentrations of impermeable solutes on either side of the membrane

Question 13

What point is reached in diffusion?

Answer 13

equilibrium

Question 14

equilibrium

Answer 14

the state in which the distribution of a substance is even throughout a region

Question 15

What is the role of proteins in diffusion?

Answer 15

protein channels allow large or polar molecules to pass through the selectively permeable cell

Question 16

osmosis

Answer 16

the diffusion of water molecules through a selectively permeable membrane

Question 17

How does water move in most cell membranes in osmosis?

Answer 17

very rapidly–if water moves too freely, the volume of the cell increases until the cell bursts

Question 18

osmotic pressure

Answer 18

the forces of osmosis moving down the concentration gradient

Question 19

active transport

Answer 19

a type of transport that uses energy; usually helps get large particles in and out of a cell and moves against the concentration gradient

Question 20

How does active transport use energy?

Answer 20

uses energy stored in ATP to fuel transport

Question 21

What is the role of proteins in active transport?

Answer 21

carrier proteins allow chemicals to cross the membrane against a concentration gradient

Question 22

endocytosis

Answer 22

the process of taking in materials by pockets in the cell membrane

Question 23

exocytosis

Answer 23

the process by which large amounts of materials are removed from a cell

Question 24

pinocytosis

Answer 24

the process by which liquid is taken in by endocytosis and pinched off to vacuoles in the cell

Question 25

homeostatsis

Answer 25

the ability to maintain a stable internal condition despite changing external conditions

Question 26

What is the role of homeostasis in the membrane and diffusion, osmosis, and active transport?

Answer 26

membrane: keeps cell contents in and foreign material out and provides controlled pathways for the transportation of fuel, fluids, and waste
diffusion: keeps the cell’s concentration balanced
osmosis: maintains the concentration of solvents and solutes inside cells

active transport: regulates what goes in and out of the cell

Question 27

What are the levels of organization in order?

Answer 27

1. cell
2. tissue
3. organ
4. organ system
5. organism

Question 28

tissue

Answer 28

a group of similar cells performing a particular function

Question 29

organ

Answer 29

a group of tissues that perform a function

Question 30

organ system

Answer 30

a group of organs working together to perform a function