SCIENCE BIOLOGY_Sec3 (Chpt 2): Movement of Substances

Question 1

Diffusion (def)

Answer 1

• net movement of particles (atoms, molecules or ions) from a region of higher concentration to a region of lower concentration, down a concentration gradient
• partially permeable membrane not needed

Question 2

concentration (def)

Answer 2

refers to the amount of particles per unit volume

Question 3

concentration gradient (def)

Answer 3

difference in concentration between two regions over a given distance

Question 4

diffusion [4pts]

Answer 4

• caused by random, constant movement of particles
• possess movement (kinetic) energy
• random movement: will move down concentration gradient until evenly spread out in all regions after some time
• passive transport: does not require energy to take place

Question 5

equal concentration of particles in all regions

Answer 5

concentration gradient is no longer present –> no net movement of particles between these regions anymore

Question 6

rod increases with [5pts]

Answer 6

1. steeper conc. gradient
2. shorter dist. for substance to travel
3. larger surface area to volume ratio
4. smaller particles of substance
5. higher temp.

Question 7

factors affecting rate of diffusion [3pts]

Answer 7

1. surface area-to-volume ratio
2. diffusion distance
3. concentration gradient

Question 8

surface area-to-volume ratio [3pts]

Answer 8

• SA:volume ratio –> amount of surface area per unit volume of an object
• greater SA:volume ratio of a substance, higher rod of substances in and out of it
• two cells with same volume: one with larger SA enables substances to diffuse in and out of cell faster –> higher rod of substances in and out of it

Question 9

surface area-to-volume ratio [adaptation example]

Answer 9

long narrow protrusions, folds or finger-like projections
- increase SA:volume ratio
- rod of substances in and out of them is higher
- e.g. root hair cells, epithelial cells

Question 10

root hair cell SA:volume ratio adaptation [3pts]

Answer 10

• long narrow protrusion
• increases SA:volume ratio of cell membrane - absorb water and minerals more efficiently

Question 11

epithelial cells SA:volume ratio adaptation [3pts]

Answer 11

• numerous tiny, finger-like projections: microvilli
• increase SA:volume ratio of cell membrane of epithelial cells in small intestine
• allow digested food molecules to diffuse into it faster

Question 12

diffusion distance [3pts]

Answer 12

• refers to the distance between two regions of different concentrations of particles
• diffusion dist. decreases: rod increases
• particles take less time to move through shorter distance (vice versa)

Question 13

diffusion distance adaptations

Answer 13

help decrease diffusion distance in order to increase rod

Question 14

diffusion distance adaptations [human blood capillaries]

Answer 14

• reduce diffusion distance and speed up movement of oxygen and carbon dioxide into and out of cells
• human blood capillaries and alveolus (air sac) in lungs are only one cell thick

Question 15

diffusion distance adaptations [root hair cell]

Answer 15

• cell wall and cell membrane of root hair cells are very thin
• shortens diffusion distance
• increases rod of water and minerals from soil into cells

Question 16

concentration gradient

Answer 16

greater difference in concentration between two regions, higher rod

Question 17

conclusion (SA:voume ratio)

Answer 17

smaller size of an object: greater SA:volume ratio –> hence faster movement of substances in and out of object –> faster rod

Question 18

osmosis (def)

Answer 18

• net movement of water molecules from region of their higher concentration (higher water potential) to a region of their lower concentration (lower water potential), through a partially permeable membrane

Question 19

osmosis (transport) [2pts]

Answer 19

• passive transport
• does not consume energy

Question 20

water potential (def)

Answer 20

measure of tendency of water to move from one place to another

Question 21

dilute solution

Answer 21

• solution with a lower concentration of solute
• more water molecules per unit volume than concentrated solution

Question 22

all regions have same water potential

Answer 22

no net movement of water molecules

Question 23

solute (def)

Answer 23

substance that is dissolved in another substance

Question 24

solvent (def)

Answer 24

substance that dissolves another substance

Question 25

solution (def)

Answer 25

evenly mixed of different substances where solute is evenly distributed throughout the solvent

Question 26

osmotic changes in cells - red blood cell (example of animal cells) - effect in concentrated solution [5pts]

Answer 26

- crenation occurs - water leaves cell - membrane of cell forms little spikes - cell shrinks and becomes dehydrated - cell dies

Question 27

osmotic changes in cells - red blood cell (example of animal cells) - effect in dilute solution [5pts]

Answer 27

- haemolysis occurs - water enters the cell - animal cells do not have cell walls to prevent over expansion of cell membrane - cell bursts - cell dies

Question 28

osmotic changes in cells - leaf cell (example of plant cells) - effect in concentrated solution [4pts]

Answer 28

- plasmolysis occurs - water leaves cell - cell and vacuole decrease in size and becomes flaccid or limp - cytoplasm shrinks away from cell wall and cell is plasmolysed

Question 29

osmotic changes in cells - leaf cell (example of plant cells) - effect in dilute solution [5pts]

Answer 29

- turgor pressure - water enters cell - vacuole increases in size - cellulose cell wall prevents over expansion of cell membrane by exerting opposing pressure - when cell if fully turgid, further entry of water is prevented

Question 30

turgor pressure (def)

Answer 30

force exerted when plasma membrane pushes against cell wall

Question 31

turgor pressure [4pts]

Answer 31

- crucial role in maintaining shape of soft tissues (e.g. leaves, stems) - turgor pressure present: cells of herbaceous (herbs) and non-woody plants able to remain firm and erect - if cells lose too much water: lose their turgidity and plants will wilt - changes in turgor: e.g. opening and closing of stomata caused by changes in turgor of guard cells

Question 32

too much fertiliser [5pts]

Answer 32

- plant cells undergo plasmolysis and become plasmolysed - excessive fertiliser causes soil to become very concentrated - allows water molecules to move from inside the plant cells to in the soil - water leaves plant cells, vacuoles (responsible for maintaining turgor pressure) start to shrink - cell membrane and cytoplasm start to pull away from cell wall, causing plant cells to become flaccid or wilted

Question 33

active transport (def)

Answer 33

movement of substances across a cell membrane against a concentration gradient, using energy from cellular respiration (only takes place in living cells --> carry out respiration)

Question 34

importance of active transport [1pt]

Answer 34

allows cells to obtain nutrients that are low in concentrations outside of cell

Question 35

active transport: root hair cells [2pts]

Answer 35

- high ion concentration - many mitochondria to release energy to carry out active transport of ions into cells