Chapter 2: Movement Of Substances🧪

Question 1

Diffusion

Answer 1

Net movement of particles from a region of higher concentration to a region of lower concentration, down a concentration gradient

Question 2

Concentration gradient

Answer 2

Different between concentration between two regions

Question 3

Factors affecting rate of diffusion

Answer 3

1. Temperature (higher temp, faster diffusion)
2. SA to vol ratio (larger ratio, higher diffusion)
3. Concentration gradient (stepper gradient, faster diffusion)
4. Size/ mass of particles (smaller, diffuse faster)
5. Diffusion distance (shorter distance, faster diffusion)
6. Diffusion medium (solid; slowest, liquid; faster, gas; fastest)

Question 4

SA to volume ratio adaptations

Answer 4

Greater SA to volume ratio, faster the rate of diffusion

Increased SA to volume ratio in cells function in absorption (eg Root hair cell, epithelial cell)

Question 5

Diffusion distance

Answer 5

Time taken for a substance to move from point point to another

Shorter diffusion distance, less time needed for substances to travel, increased rate of diffusion

Question 6

Facilitated diffusion

Answer 6

Net movement of ion and polar (water soluble) molecules through cell membranes using specific protein channels or carriers down a concentration gradient

(Passive process, only relies on kinetic energy of molecules)

Question 7

Osmosis

Answer 7

Net movement of water molecules from a region of higher water potential to a region of lower water potential through a ppm

Question 8

Water potential

Answer 8

Measure of tendency of water molecules to enter/leave solutions by osmosis

Potential of pure water: 0

Question 9

Comparing water potential

Answer 9

• Hypotonic: less (solute)
• Isotonic: equal
• Hypertonic: more

Terms are used relative to another solution

Question 10

Solution with higher water potential (plant cell)

Answer 10

Expand/ swell: protected by inelastic cell wall

1. Cell sap has a lower water potential than solution
2. Water enters via osmosis through the partially permeable cell membrane
3. Cell expands and swells. Cell becomes turgid.
4. Water molecules enter, vacuole size increases and pushes against the cell wall.

Question 11

Turgor

Answer 11

Turgidity of cell with water

Question 12

Turgor pressure

Answer 12

Pressure by water in vacuole

Question 13

Solution with higher water potential (animal)

Answer 13

Cell swells and may burst as there is no cell wall to protect it

Water potential is higher than that of the cytoplasm

Question 14

Same water potential

Answer 14

Same movement of water molecules in both directions

No net movement of water molecules in and out of cell

Question 15

Solution with lower water potential (plant)

Answer 15

1. Cell sap has higher water potential than solution
2. By osmosis, water molecules leave vacuole and cytoplasm via ppm
3. Cell decreases in size and becomes flaccid/limp.

Question 16

Solution with lower water potential (animal)

Answer 16

Cell loses water and shrinks
Spikes appear: crenation
Cell becomes dehydrated and eventually dies

Question 17

Turgor in plants

Answer 17

Maintains shape word soft tissue: remain firm
If not, cell loses turgidity and plant wilts

Question 18

Active transport

Answer 18

Energy from respiration is used to move particles of a substance across a membrane, against the concentration gradient: region of lower concentration to region of higher concentration

Question 19

Mechanisms of active transport

Answer 19

Bulk transport of materials

Carrier protein molecules

Question 20

Bulk transport

Answer 20

Endocytosis and exocytosis:
Movement of large molecules (like proteins) in and out of cells

Question 21

Endocytosis definition

Answer 21

Uptake of materials into cell but inward foldings of cell surface membrane

Question 22

Endocytosis process

Answer 22

Sac of membrane are formed that surround a large molecule or even an entire cell from the extracellular environment
Membrane pinches off and forms vesicle in cell
ATP energy is used to move around cytoplasm
Vesicle can fuse with other special vesicles with enzymes to digest its contents
Endocytosis may involve uptake of liquids (pinocytosis) or solid particles (phagocytosis)

Question 23

Exocytosis definition

Answer 23

Materials exported out of the cell via secretory vesicles

Question 24

Exocytosis process

Answer 24

Golgi apparatus packages large molecules into secretory vesicles which travel and fuse with cell surface membrane
ATP energy is used to move cytoplasm around
Exocytosis is important in removal of waste material out of cell and secretion of cellular products (eg digestive enzymes like proteins or hormones like proteins and fats)

Question 25

Active transport in living things

Answer 25

Uses energy released in respiration

Human:
Epithelial cells’ glucose uptake by microvilli
Kidney tubules into blood capillaries

Plants:
Root hair cells: mineral salts (depending on their concentration)