Chapter 2 : Movement Of Substances

Question 1

Definition of Diffusion

Answer 1

• net passive movement of molecules
• high conc to low conc
• down conc grad

Question 2

Factors affecting Rate of Diffusion (5)

Answer 2

• Particle Size
• Temperature
• Surface area
• Distance between regions
• Membrane thickness

Question 3

Definition of Osmosis

Answer 3

• Net passive movement of water molecules
• from region of high water potential to low water potential
• across a partially permeable membrane
• down water potential gradient

Question 4

What would happen to an animal cell when placed in a
a) hypotonic solution
b) hypertonic solution
c) isotonic solution

Answer 4

a) cell swells and bursts
b) cell shrinks and undergoes crenation
c) cell remains unchanged

Question 5

What would happen to an plant cell when placed in a
a) hypotonic solution
b) hypertonic solution
c) isotonic solution

Answer 5

a) the cell becomes turgid
b) the cell becomes plasmolysed
c) the cell remains unchanged

Question 6

What is turgor pressure ( or turgidity )

Answer 6

The pressure which the cell contents against the cell wall in plant cells

Question 7

Definition of Facilitated Diffusion

Answer 7

• Spontaneous passage of molecules and ions
• bound to specific carrier proteins
• across biological membrane
• down conc gradient

Question 8

How do carrier proteins facilitate diffusion across biological membrane ?

Answer 8

Specific molecule attaches to the carrier protein and induces a conformational change in the carrier protein, ‘delivering’ molecule through the membrane.

Question 9

Definition of Active Transport

Answer 9

• Movement of materials
• through a plasma membrane
• against the conc. gradient

Question 10

Describe the process of active transport with carrier protein

Answer 10

1. Molecule combines with carrier protein
2. ATP attaches with carrier protein, inducing conformational change in protein
3. Molecule is delivered into the cell

Question 11

Factors affecting active transport ? (3)

Answer 11

1. Temperature
2. O2 conc
3. Presence of poisons (cyanide)

Question 12

Similarities and Differences btw Passive and Facilitated Diffusion (4)

Answer 12

Similarities:
1. Both are passive transport processes ( do not need ATP )
2. Equilibrium reached when concentrations are equal

Differences
1. Rate of diffusion in passive diffusion depends on conc grad, specific molecules diffuse faster in facilitated diffusion
2. Passive diffusion can occur in both direction while in facilitated diffusion it is faster in 1 direction

Question 13

Definition of Endocytosis

Answer 13

• Cellular uptake of macromolecules and particulate substances
• by localised regions of the plasma membrane
• surround the substance and pinch off to form an intercellular vesicle

Question 14

Name the 2 types of endocytosis and how are they different

Answer 14

Phagocytosis and Pinocytosis.
1. Phagocytosis is the intake of solid material while pinocytosis is for liquid materials.

Question 15

What’s exocytosis

Answer 15

Reverse of endocytosis
Passage of materials out of the cell in vesicles which fuse with the cell membrane

Question 16

Are exocytosis and endocytosis active or passive transport processes

Answer 16

Active, they require ATP

Question 17

Why is cell size limited

Answer 17

If cells are too big
1. SA : V ratio increases faster than SA, transport of substances in and out of cell would take too long ( ie transport of nutrients into the cell )

If cells are too small
2. Organelles can’t fit and function properly