Chapter 9: Cell Membrane and Transport Processes

Question 1

What is the fluid mosaic model?

Answer 1

Describes the membrane as having the ability to flow and change shape, and having specialised protien molecules embedded in the membrane in various pattens.

Question 2

Explain the phospholopid bilayer.

Answer 2

Is a selectively perbiable membrane made of a double layer of phospholipids, with a hydrophilic phosphate head and 2 hydrophobic fatty acid tails.

Question 3

What are the 4 types of protiens in the cell membrane?

Answer 3

• Transport protiens
• Receptor protiens
• Recognition protiens
• Adhesion protiens

Question 4

What are the 2 types of transport protiens?

Answer 4

• Channel protiens
• Carrier protiens

Question 5

What is a channel protien and what is its function?

Answer 5

It is a type of transport protien that catalyses the movement of ions and simple molecules down their electro chemical gradient. It uses facilitated diffusion by opening and closing the channels to let substances through.

Question 6

What is a carrier protien and what is its function?

Answer 6

It is a type of transport protien that binds to molecules on one side of the membrane, changes its shape and releases molecules the other side the membrane. Many use active transportto move substances against their concentration gradient, some use passive.

Question 7

What is the function of adhesion protiens?

Answer 7

To link cells together to maintain structure, and the normal functioning of tissues.

Question 8

What is the function of receptor protiens?

Answer 8

To bind hormones that cause a change in the cells activities.

Question 9

What are 3 passive transport processes?

Answer 9

• Simple diffusion
• Facilitated diffusion
• Osmosis

Question 10

What are 3 active transport processes?

Answer 10

• Actice transport
• Endocytosis
• Exocytosis

Question 11

Give 4 examples of molecules that can pass through the cell membrame with simple diffusion?

Answer 11

• Oxygen (O2)
• Water (H2O)
• Carbon dioxide (CO2)
• Ethanol

Question 12

Why can alchohols easily diffuse across the cell membrane?

Answer 12

They are non-polar, meaning they are soluble in lipids and not repelled by the lipid tails.

Question 13

What is facilitated diffusion and what substances move across the cell membrane with it?

Answer 13

It is a form of diffusion the requires a substance to bind to a carrier protien to move across the cell membrane, down a concentration gradient. Charged particles and larger molecules such as glucose.

Question 14

What is osmosis?

Answer 14

The diffusion of water through a semipermiable membrane, down its concentration gradient.

Question 15

What is a hypotonic solution?

Answer 15

Lower solute concentration (more water) outside the cell compared to inside the cell, water moves into the cell, down the concentration gradient.

Question 16

What is an isotonic solution?

Answer 16

Same concentration of solutions inside and outside the cell, no net movement of water.

Question 17

What is a hypertonic solution?

Answer 17

Higher solute concentration (less water) outside the cell compared to inside the cell, water moves out of the cell, down the coincentration gradient.

Question 18

What is active transport?

Answer 18

The process where cells use ATP to transport substances across the cell membrane against their concentration gradient.

Question 19

What is endocytosis? And what are the names for solids and liquids?

Answer 19

Is the process of moving large molecules such as polysaccharides across the cell membrane into the cell.
- Phagocytosis > engulfing solids
- Pinocytosis > engulfing liquids

Question 20

Give an example of when human cells use phagocytosis and pinocytosis.

Answer 20

• Phagocytosis > white blood cells defending the body against disease
• Pinocytosis > Cell membrane engulfs fat droplets in small intestine

Question 21

What are the 4 factors that affect the exchange of materials across the cell membrane? Explain what they mean and how they affect the exchange.

Answer 21

• Chemical properties of a substance: if the molecules are charged or not will determine if it can diffuse straight through the membrane, or if passive transport or facilitated diffusion is needed
• Physical properties of a substance: the size and shape of a molecule will determine if it can diffuse straight through the membrane, or if passive transport, active transport, endo cytosis or exocytosis is needed
• Concentration gradient: How high or low the concentration of the substance is on both sides of the membrane will affect how easily a substance will diffuse from one side to the other
• Size and shape of cells: The greater distance a substance has to travel, the slower the rate of diffusion. If there is a high surface to volume ratio, the uptake of nutrients is higher and the removal of wastes is faster

Question 22

What is a recognition protien, and what is its function?

Answer 22

Protiens that act as a marker on the membrane. It allows the immune system to recognise its own cells from foriegn ones