Cell Membranes

Question 1

What are cell membranes also known as?

Answer 1

Plasma membranes.

Question 2

Membranes let some molecules through, but not others. What is this called?

Answer 2

Partially permeable.

Question 3

What are the three methods that substances can move across the membrane by?

Answer 3

1) Diffusion 2) Osmosis 3) Active Transport

Question 4

Name tthree reasons why a membrane can be found around organelles?

Answer 4

1) Acts as a barrier between the cytoplasm and organelle. As a result, this makes different functions more efficient. 2) They can control what substances enter and leave because they are partially permeable. 3) Membranes can form vesicles to transport substances between different areas of the cell.

Question 5

What term was suggested in 1972 to describe the arrangement of molecules in the membrane?

Answer 5

Fluid mosaic model.

Question 6

Name 5 membrane componants.

Answer 6

1) Phospholipids 2) Cholesterol 3) Proteins 4) Glycolipids 5) Glycoproteins

Question 7

What two TYPES of water soluble molecules are unable to pass through the phospholipid bilayer?

Answer 7

1) Ions 2) Polar

Question 8

What role do proteins play in the cell membrane?

Answer 8

Control what enters and leaves the cell.

Question 9

Define diffusion.

Answer 9

The net movement of particles (molecules or ions) from and area of higher concentration to an area of lower concentration.

Question 10

What is the path of higher concentration to lower concentration known as?

Answer 10

Concentration gradient.

Question 11

Diffusion requires no energy for it to happen. What sort of process is this?

Answer 11

Passive.

Question 12

Define osmosis.

Answer 12

The diffusion of water molecules accross a partially permeable membrane down a water potential gradient.

Question 13

What does the term isotonic mean?

Answer 13

The two solutions have the same water potential.

Question 14

What is a hypotonic solution?

Answer 14

A solution with a higher water potential than that of the cell.

Question 15

What is a hypertonic solution?

Answer 15

A solution with a lower water potential than that of the cell.

Question 16

What two types of proteins are used in facilitated diffusion?

Answer 16

1) Carrier proteins 2) Channel proteins

Question 17

When are carrier proteins used and how do they work?

Answer 17

Used to move large molecules (polar and ions) from a high concentration to a low concentration (down a concentration gradient). 1) Molecule attaches to carrier protein 2) Protein changes shape and releases the molecule on the other side.

Question 18

Describe how channel proteins work.

Answer 18

They form pores in the membrane for smaller ions and polar molecules.

Question 19

(Complete the sentence) Different channel proteins…

Answer 19

…facilitate the diffusion of differently charged particles.

Question 20

Why does active transport exist?

Answer 20

To move molecules against the concentration gradient.

Question 21

Used on large molecules. Cell sourrounds the molecule with a section of its plasma membrane. It is then pinched off to form a vesicle for transport inside the cell. Name the process.

Answer 21

Endocytosis.

Question 22

Used for some substances that need to be released from the cell. Vesicles fuse with the plasma membrane and release their contents outside of the cell. Somtimes some substances are insserted into the plasma membrane. Name the process.

Answer 22

Exocytosis.

Question 23

Define facilitated diffusion.

Explain the process of facilitated diffusion.

Answer 23

1) Net movement of particles from an area of higher concentration to an area of lower concentration.
2) Carrier proteins are used to aid the diffusion of large molecules through the plasma membrane.

Question 24

Name a solvent.

What is its effect on the cell membrane?

Answer 24

Ethanol.

Can dissolve the lipids in the cell membrane causing it to lose its structure and become more permeable.

Question 25

What effect does temperature have on phospholipids?

Answer 25

Increases the movement of the bilayer thus affecting the structure and permeability of the membrane.

Question 26

How do cells communicate with each other?

Answer 26

Cell signalling using messenger molecules.

Question 27

What happpens to messenger molecules when they reach there destination?

Answer 27

Bind to membrane-bound receptors.

Question 28

What two things bind to receptors?

Answer 28

Drugs and Hormones