Properties of Plasma membraneSemi permeable/ partially permeable membrane

The movements of soluble subtances across plasma

membrane through:

a) Passive transport• Simple diffusion• Facilitated diffusion• Osmosis

b) Active transport

Simple diffusion

0Molecules move randomly from a region of higher concerntration to a region of lower concerntration.

0Occur until a dynamic equilibrium is reached, that is the concerntration is the same in all region.

FACTOR AFFECTING THE RATE OF DIFFUSION

a) Temperature - Higher temperature, the particles have more kinetics energy, so diffuse

at higher rate.

b) Surface area - The larger the surface area, higher rate of diffusion.

c) Diffusion medium- Gas > liquid > solid

d) Size of molecules/ ions- Smaller molecules diffuse faster than larger particles.- Lipid soluble molecules (vit A, D, E and K)- Small molecules - Dissolved gases

e) Difffusion gradient- The greater steeper has higher rate of diffusion.

Facilitated diffusion0The transport of molecules by a process that involves

carrier protein or channel protein within cell membrane.

0Substances such as glucose, amino acids, proteins and nucleic acids.

Osmosis 0The passage of water molecules from a dilute solution to a

more concerntrated solution across semi permeable membrane.

0Water continue to pass through until the solute concerntration are the same in both region.

0Example: root hair- Are elongated epidermis cell that project into the soil.

Root hairs increase the surface area of the root, to absorb water.

Question and

answer section

1. Simple diffusion is defined as the movement ofA) molecules from areas of higher concentration to areas of

lower concentration.B) molecules from areas of lower concentration to areas of

higher concentration.C) water molecules across a membrane.D) gas molecules across a membrane.E) gas or water molecules across a membrane.

2 When sugar is mixed with water, equilibrium is reached when

A) molecules of sugar stop moving.B) water and sugar molecules are moving at the same speed.C) the dissolved sugar molecules are evenly distributed

throughout the solution.D) there are the same number of water molecules as dissolved

sugar molecules.E) two tablespoons of coffee are added.

3 The rate of diffusion is affected by which of the following?A) temperatureB) size of moleculesC) steepness of the concentration gradientD) A and BE) A, B and C

4 The molecules in a solid lump of sugar do not move.A) TrueB) False

5 Diffusion is one of the processes whereby materials are exchanged between a cell and its environment.F) TrueG) False

6. Facilitated diffusion requiresA) enzymes.B) carrier proteins.C) lipid carriers.D) carbohydrate carriers.E) lipid or carbohydrate carriers.

7. Facilitated diffusion occursA) into the cell only.B) out of the cell only.C) in either direction depending on the

temperature.D) in either direction depending on the

concentration gradient of the molecule.E) in either direction depending on the size

of the molecule.

8 Facilitated diffusion is used to transportA) sugars and amino acids.B) H2O and O2.C) CO2 and O2.D) CO2 and H2O.E) sugars and H2O.

9 Unlike simple diffusion, facilitated diffusion requires energy expenditure by the cell.

A) TrueB) False

10 Facilitated diffusion requires a specific transporter for a specific molecule.

A) TrueB) False

11. Osmosis is best defined as the movement of

A) molecules from an area of high concentration to an area of lower concentration.

B) molecules from an area of low concentration to an area of higher concentration.

C) water molecules across a membrane from an area of low water to an area of higher concentration.

D) water molecules across a membrane from an area of high water concentration to an area of lower concentration.

E) water molecules inside a container.

12 Which of the following will pass through a cell membrane most easily?

A) small polar moleculesB) small nonpolar moleculesC) large polar moleculesD) large nonpolar moleculesE) large neutral molecules

13 A red blood cell placed in a hypertonic medium willA) expand.B) burst.C) shrink.D) have no change in shape.E) become a white blood cell.

14 A 5% urea solution is hypotonic to a 10% urea solution.A) TrueB) False

15 If a cell is placed in an isotonic medium, there will be no net movement of water.

A) TrueB) False

b) Active transport

0 Is the movement of particles across the plasma membrane against the concerntration gradient (from region of low to higher concerntration)

0Also called as sodium- potassium pump.0Requires an input of energy provided by ATP.0Requires specific carrier protiens that bind to the

substances to be transported. 0 carrier protein refers as biological pumps

1 The sodium-potassium pump functions to pumpA) sodium ions out of the cell and potassium ions into the cell.B) sodium ions into the cell and potassium ions out of the cell.C) sodium and potassium ions into the cell.D) sodium and potassium ions out of the cell.E) sodium and potassium ions in both directions across the cell membrane.

2 What is the source of energy used to power the sodium-potassium pump?A) breakdown of ATPB) formation of ATPC) transport of ATP by the pumpD) breakdown of GTPE) transport of GTP by the pump

3 During one cycle, the sodium-potassium pump binds and moves.A) 1 Na+ and 2 K+.B) 2 Na+ and 2 K+.C) 2 Na+ and 3 K+.D) 3 Na+ and 2 K+.E) 3 Na+ and 3 K+.

4 The sodium-potassium pump is a trans-membrane protein.

A) TrueB) False

5 The binding and release of sodium or potassium ions are due to conformational changes in the protein.

A) TrueB) False