Its all about the movement of substances across the plasma membrane. students may get the information about the passive and active transport in detail..

2. The movements of soluble
subtances across plasma
membrane through:
a) Passive transport
• Simple diffusion
• Facilitated diffusion
• Osmosis
b) Active transport

3. Simple diffusion
0 Molecules move randomly from a region of higher
concerntration to a region of lower concerntration.
0 Occur 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

4. 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.

6. Facilitated diffusion
0 The transport of molecules by a process that involves
carrier protein or channel protein within cell membrane.
0 Substances such as glucose, amino acids, proteins and
nucleic acids.

8. Osmosis
0 The passage of water molecules from a dilute solution to a
more concerntrated solution across semi permeable
membrane.
0 Water continue to pass through until the solute
concerntration are the same in both region.
0 Example: root hair
- Are elongated epidermis cell that project into the soil.
Root hairs increase the surface area of the root, to absorb
water.

10. Question
and
answer
section

11. 1. Simple diffusion is defined as the movement of
A) 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.

12. 3 The rate of diffusion is affected by which of the
following?
A) temperature
B) size of molecules
C) steepness of the concentration gradient
D) A and B
E) A, B and C
4 The molecules in a solid lump of sugar do not move.
A) True
B) False
5 Diffusion is one of the processes whereby materials
are exchanged between a cell and its environment.
A) True
B) False

13. 6. Facilitated diffusion requires
A) enzymes.
B) carrier proteins.
C) lipid carriers.
D) carbohydrate carriers.
E) lipid or carbohydrate carriers.
7. Facilitated diffusion occurs
A) 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.

14. 8 Facilitated diffusion is used to transport
A) 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) True
B) False
10 Facilitated diffusion requires a specific transporter for a
specific molecule.
A) True
B) False

15. 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 molecules
B) small nonpolar molecules
C) large polar molecules
D) large nonpolar molecules
E) large neutral molecules

16. 13 A red blood cell placed in a hypertonic medium will
A) 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) True
B) False
15 If a cell is placed in an isotonic medium, there will be no
net movement of water.
A) True
B) False

17. b) Active transport
0 Is the movement of particles across the plasma
membrane against the concerntration gradient
(from region of low to higher concerntration)
0 Also called as sodium- potassium pump.
0 Requires an input of energy provided by ATP.
0 Requires specific carrier protiens that bind to the
substances to be transported.
0 carrier protein refers as biological pumps

19. 1 The sodium-potassium pump functions to pump
A) 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 ATP
B) formation of ATP
C) transport of ATP by the pump
D) breakdown of GTP
E) 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+.

20. 4 The sodium-potassium pump is a trans-membrane
protein.
A) True
B) False
5 The binding and release of sodium or potassium ions
are due to conformational changes in the protein.
A) True
B) False