2.3 Plasma membrane: composition and surface area, and 2.4 Transport across the plasma membrane

Question 1

What is the environment of living cells?

Answer 1

A layer of fluid in contact with the outer plasma membrane.

Question 2

What is the plasma membrane?

Answer 2

Controls the movement of substance between the extracellular fluid outside and the intracellular fluid (cytosol) inside the cell.

Question 3

What conditions can unicellular organisms regulate and give an example for each:

Answer 3

• Temperature (pant, shiver, lose fur)
• Oxygen concentration (breathing in)
• Carbon dioxide concentration (breathing out)
• pH (acidity or alkalinity)
• Osmotic pressure (concentration of salts/ions)
• Nitrogen waste concentration
• Glucose concentration (store it in the body for when it is needed)

Question 4

What is the phospholipid bilayer?

Answer 4

A double layer of phospholipids which makes up the plasma membrane.

Question 5

What are the 2 functions of the phospholipid bilayer?

Answer 5

Acts as a flexible boundary of the cell

-Restricts what chemicals/substances can come in and out of the cell

Question 6

What are the 2 types of membrane proteins?

Answer 6

• Integral proteins (permanents part of the membrane)

- Peripheral proteins (temporary)

Question 7

List the 6 functions of membrane proteins:

Answer 7

• Transport substances across the membrane
• Secure the cytoskeleton to the membrane
• Enzymes (catalysts for reactions by lowering energy)
• Receptors
• Cell to cell adhesion
• Identity markers

Question 8

What is a solute?

Answer 8

A substance dissolved into a liquid

Question 9

What is a solvent?

Answer 9

A liquid

Question 10

What is a solution?

Answer 10

A solute and a solvent

Question 11

What is a concentration?

Answer 11

The amount of solute dissolved in an amount of solvent or solution

Question 12

What is diffusion?

Answer 12

The passive net movement of a substance from an area of high concentration to an area of low concentration.
-Diffusion is very fast over small distances, while it is very slow over long distances.

Question 13

What is a concentration gradient?

Answer 13

The difference between solute concentrations

Question 14

When is diffusion fastest?

Answer 14

• There is a high concentration difference

- Heat is applied

Question 15

What are the 2 molecules which cannot readily cross the phospholipid bilayer?

Answer 15

• Non-polar, uncharged hydrophobic molecules

- Small, polar uncharged hydrophilic molecules

Question 16

What are the 2 molecules which cannot diffuse across the phospholipid bilayer?

Answer 16

• Larger (> 5 carbon atoms) uncharged polar molecules

- Ions (charged)

Question 17

What is the function of channels in the phospholipid bilayer?

Answer 17

Provide a route for diffusion of substance that cannot penetrate the lipid bilayer

Question 18

What are the principles of diffusion?

Answer 18

• The smaller the object, the greater the diffusion (large SA:V)
• The larger the object, the lower the diffusion (small SA:V)

Question 19

What is osmosis?

Answer 19

The movement of free-water molecules through a semi-permeable membrane from an area of high water concentration to low water concentration across a select semi-permeable membrane.

Question 20

What is a hypertonic solution?

Answer 20

A solution that contains a high concentration of solute compared to the other side of a semi-permeable membrane.

Question 21

What is an isotonic solution?

Answer 21

A solution that has an equal solute concentration compared to the other side of a semi-permeable membrane.

Question 22

What is a hypotonic solution?

Answer 22

A solution that contains a lower concentration of solute compared to the other side of the semi-permeable membrane.

Question 23

What is exocytosis in bulk transport?

Answer 23

Transport out of a cell, where vesicles transporting molecules fuse to the membrane to release their contents.

Question 24

What is endocytosis in bulk transport?

Answer 24

Transport into the cell, which has 3 types.

Question 25

What is active transport?

Answer 25

The active net movement of a substance from an area of low concentration to an area of high concentration through a membrane via a carrier protein.

Question 26

What is facilitated diffusion?

Answer 26

The passive net movement of a substance from an area of high solute concentration to an area of low solute concentration through a membrane via a specific protein channel.