Ch.3 Movement of Substances In and Out of Cells

Question 1

Define diffusion

Answer 1

The net movement of particles from a region of their higher concentration to a region of their lower concentration, down a concentration gradient, as a result of their random movement.

Question 2

Energy for diffusion comes

Answer 2

The kinetic energy of random movement of molecules and ions

Question 3

Diffusion in living organisms #1

Answer 3

Respiratory system

Diffusion in the alveoli
Carbon dioxide out, oxygen in

Question 4

Diffusion in living organisms #2

Answer 4

Digestive system (small intestine)

In the villus
Dissolved food molecules diffuse from the small intestine into blood

Question 5

Factors affecting diffusion rate

Answer 5

Concentration gradient, temperature, surface area, distance (CT DS - CT does slay)

Question 6

Diffusion - concentration gradient

Answer 6

The higher/steeper the concentration gradient, the faster the rate of diffusion.

Eg gas exchange of oxygen and carbon dioxide

Concentration gradient is the difference in concentration between 2 regions

Question 7

Diffusion - temperature

Answer 7

Higher the temperature, higher the diffusion rate

Heat = kinetic energy, so more collisions hence higher rate of diffusion

Question 8

Diffusion - surface area

Answer 8

The higher the surface area, the higher the diffusion rate

Question 9

Diffusion - distance

Answer 9

The shorter the distance, the higher the rate of diffusion

Eg thin walls of alveoli and capillaries

Question 10

Water

Answer 10

Universal solvent

Question 11

Roles of water as a universal solvent in humans

Answer 11

TRANSPORT nutrients eg glucose and amino acids in blood, sucrose in phloem

EXCRETION - removal of excretory products eg ammonia, urea

DIGESTION - hydrolysis of large biological molecules into their monomers/subunits eg proteins to amino acids

Question 12

Define osmosis

Answer 12

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

Question 13

Types of solutions - Isotonic

Answer 13

• Same concentration of solutions
• No net movement of water across plasma membrane
• Cells maintain normal shape

Question 14

Isotonic - RBC and Plant cells

Answer 14

RBC
- Normal
- Won’t change size or shape

PLANT CELL
- Flaccid
- Shrinks, becomes limp
- No net movement of water

Question 15

Types of solutions - Dilute

Answer 15

Water > solutes
- Higher water potential
- Includes distilled water

Question 16

Dilute - RBC and Plant cells

Answer 16

RBC
- Haemolysed
- Swells, bursts
- No cell wall to protect it from bursting
- Cytoplasm has a lower water potential than outside solution
- Water enters by osmosis

PLANT CELL
- Turgid
- Expands, swells
- Protected by cell wall
- Supported by turgor pressure exerted by water in the vacuole
- Plant remains upright

Question 17

Types of solutions - Concentrated

Answer 17

• Water < solutes

Question 18

Concentrated - RBC and Plant cells

Answer 18

RBC
- Crenated + spikes
- Shrinks and little spikes appear on cell membrane
- Dehydrated and eventually dies

PLANT CELL
- Plasmolysed
- PLASMOLYSIS = Shrinkage of cytoplasm + cell membrane away from the cell wall
- Wilts, eventually dies

Question 19

Plasmolysis 👍

Answer 19

Shrinkage of cytoplasm and cell membrane away from the cell wall

Question 20

Turgor

Answer 20

Maintains the shape of soft tissues in plants

Eg changes in the turgor of guard cells cause the opening and closing of the stomata

Question 21

Active transport

Answer 21

Movement of particles through a cell membrane, from a region of their low concentration to a region of higher concentration, against the concentration gradient of a particle, requiring energy from cellular respiration (ATP)

Question 22

Why shouldn’t we add too much fertiliser around the roots of plants?

Answer 22

• Thin film of water surrounds soil particles containing dissolved mineral ions, aka soil solution
• Too much fertiliser will cause the soil solution to become very concentrated and water will move out of the roots through osmosis

Question 23

Protein carriers in active transport

Answer 23

Move molecules or ions across a membrane during active transport

Question 24

Active transport - root hair cells - adaptations

Answer 24

• Lots of mitochondria which produces energy through cellular respiration
• Large surface area to increase rate of absorption