B1 Diffusion Osmosis Active Transport

Question 1

Diffusion

Answer 1

The spreading out of particles from an area of higher concentration to an area of lower concentration

Question 2

Why does diffusion only happen in solutions and gases

Answer 2

The particles in these substances are free to move randomely

Question 3

Factors which affect rate of diffusion

Answer 3

Temperature

Concentration gradient

Surface area

Question 4

How does temperature increase rate of diffusion

Answer 4

Particles have more energy

Question 5

How does concentration gradient affect the rate of diffusion

Answer 5

The greater the concentration gradient, the quicker diffusion takes place

When there is large difference in concentration between 2 regions particles will move more quickly from area of high concentration to area of low concentration

Question 6

How does surface area affect rate of diffusion

Answer 6

As the surface area of the membrane increases, the rate of diffusion also increases

As there is more space for molecules to diffuse across the membrane

Question 7

How to predict which way substances will move across a cell membran

Answer 7

Molecules travel across the membrane in the direction determined by their concentration gradients

Question 8

Osmosis

Answer 8

The movement of water molecules across a partially permeable membrane from a region of higher water concentration to a region of lower water concentration

Question 9

Why is diffusion important

Answer 9

So particles can move from 1 side of the room to another

Question 10

Why is it important for multicellular organisms to have exchange surfaces and transport systems

Answer 10

In order for substances to pass in and out of the cells

Question 11

How are exchange surfaces adapted for sufficient molecules to be transported in and out of cells

Answer 11

Large surface area

Question 12

Why is diffusion passive process

Answer 12

No energy is needed

Question 13

Concentration gradient

Answer 13

A difference in concentration between 2 areas

Question 14

What happens to surface area to volume ratio as object gets bigger

Answer 14

Decreases

Question 15

How do root hairs take in water from soil

Answer 15

Osmosis

Question 16

What happens to a plant cell when it is placed in a more DILUTE solution?

Answer 16

The cell gains water by osmosis but does not burst
This cell is now turgid

Question 17

What happens to an plant cell when it is placed in a more CONCENTRATED solution

Answer 17

Cell loses water by osmosis

Cell membrane pulls away from the cell wall

This is is called plasmolysis.

Question 18

What happens to an animal cell when it is placed in a more DILUTE solution

Answer 18

The cell gains water by osmosis and may burst. This is called lysis.

Question 19

What happens to an animal cell when it is placed in a more CONCENTRATED solution

Answer 19

The cell loses water by osmosis shrivels. This is called crenation.

Question 20

Why does a plant cell not burst when it is placed in a more dilute solution

Answer 20

The plant cell has a cell wall

Question 21

Differences between osmosis and diffusion

Answer 21

Diffusion is movement of particles and osmosis is movement of water

Diffusion does not require a membrane osmosis does

Diffusion driven by concentration gradient of particles but osmosis driven by concentration gradient of water

When they reach equilibrium

Question 22

Isotonic solution

Answer 22

A solution which has same concentration of solutes as the inside of a cell

Question 23

What happens when a cell placed us isotonic solution

Answer 23

No net movement of water across cell membrane as concentration of solutes equal inside and outside the cell

Water moves in and out of cell at same rate so cell’s size remains stable

Question 24

Hypotonic solution

Answer 24

Solution with a lower solute concentration compared to the inside of the cell

Question 25

What happens when cell placed in hypotonic solution

Answer 25

Water will move into the cell as concentration of water is higher outside the cell and lower inside the cell Cell could burst (lyse) if too much water enters

Question 26

Hypertonic solution

Answer 26

Solution with a higher solute concentration compared to the inside of the cell

Question 27

What happens when cell placed in hypertonic solution

Answer 27

Water will move out of cell as concentration of water is lower outside the cell and higher inside the cell As water leaves cell shrinks (crenate in animals or plasmolyze plant cells) as loses water

Question 28

Movement of water isotonic, hypotonic and hypertonic solution

Answer 28

Isotonic - No net water movement, cell remains the same size Hypotonic - Water enters the cell, causing it to swell Hypertonic - Water leaves the cell, causing it to shrink

Question 29

What happens to animal cells when they lose or gain too much water

Answer 29

They stop working properly

Question 30

Why maintaining constant internal conditions in living organisms is important

Answer 30

Enzymes only function properly under a small range of certain conditions, such as preferred pH and temperature If enzymes cannot function this could cause organism to die

Question 31

What happens if plant loses too much water

Answer 31

They become soft

Question 32

Use osmosis to explain the effect of placing plant tissue in salt or sugar solutions

Answer 32

The cells will shrink if placed in a solution of sugar or salt in water due to osmosis

Question 33

Explain the mechanisms that lead to turgid or flaccid plant cells and plasmolysis

Answer 33

The pressure created by the cell wall stops too much water entering and prevents cell lysis Cells that are not turgid are flaccid (lacking in stiffness or strength)

Question 34

Explain how a model shows osmosis in a cell

Answer 34

As water moves in by osmosis the vacuole fills up and presses out against the cell wall

Question 35

Write a suitable plan to investigate into the effect of salt or sugar solutions on plant tissue

Answer 35

Prepare samples of potatoes (or other plant tissue) Place in different concentrations of sugar or sodium chloride solution Make measurements of mass and length of your samples before and after soaking them in solutions Calculate the percentage change in mass of plant tissue

Question 36

Active transport

Answer 36

Movement of a substance against a concentration gradient using energy

Question 37

Why active transport is important for living organisms

Answer 37

Crucial for cell survival and rapid nutrient absorption by the cells

Question 38

Why can't root hair cells use diffusion to take up minerals from soil

Answer 38

Concentration of minerals is usually higher in root hair cells than in the soil around them

Question 39

Why do plants need mineral ions

Answer 39

Healthy growth

Question 40

What does active transport need to work

Answer 40

Energy from respiration to make it work

Question 41

Example of how active transport happens in humans

Answer 41

Taking glucose from the gut

Question 42

When is active transport used in the gut

Answer 42

When there is lower concenration of nutrients in the gut but a higher concentration of nutrients in the blood

Question 43

What happens in there's higher concentration of glucose and amino acids in the gut

Answer 43

They diffuse into the blood

Question 44

When would a concentration gradient be the wrong way

Answer 44

When there's a lower concentration of nutrients in the gut than there is blood

Question 45

Urea

Answer 45

Waste product produced from breakdown of proteins

Question 46

Where does urea diffuse from

Answer 46

Liver

Question 47

What does how easy it is for an organism to exchange substances with its environment depend on

Answer 47

Organism's surface area to volume ratio

Question 48

The larger an organism is...

Answer 48

The smaller its surface area is compared to its volume

Question 49

In single celled organisms how can gases and dissolved substances diffuse directly into (or out of) the cell across the cell membrane

Answer 49

They have large surface area compared to their volume

Question 50

Why do multicellular organisms need some sort of exchange surface for efficient diffusion

Answer 50

Substances can diffuse from their outside surface to supply their entire volume.

Question 51

Where does active transport take place

Answer 51

Root hair cells in plants Small intestine Kidneys Nerve cells (neurons)

Question 52

Differences between diffusion, osmosis and active transport

Answer 52

Active transport and osmosis always require a membrane, diffusion occurs with or without a membrane Active transport requires energy, osmosis and diffusion don't Diffusion is high to low gradient, active transport is low to high and osmosis is high water potential to low water potential

Question 53

How does active transport take place

Answer 53

Binding of molecules ATP binding and release Conformational change of transport protein Release of molecule Return to original shape

Question 54

How a cell that carries out active transport is adapted to this function

Answer 54

High number of mitochondria Abundance of transport proteins in membrane Increased surface area of cell membrane Removal of metabolic waste

Question 55

Suggest improvements a representational model that shows active transport

Answer 55

Show energy used Direction of concentration gradients

Question 56

Suggest limitations a representational model that shows active transport

Answer 56

Oversimplification Lack of context

Question 57

Function of exchange surfaces

Answer 57

Allows water and other nutrients to enter the organism, and waste to be exchanged

Question 58

How the effectiveness of exchange surfaces is increased

Answer 58

Large surface area Short diffusion distance Good blood supply

Question 59

link ideas about diffusion to explain how the adaptations of exchange surfaces increases their effectiveness

Answer 59

Large surface area provides space for molecules to diffuse Thin membranes reduces distance over which diffusion must occur

Question 60

What ratio does a single celled organism have

Answer 60

Relatively large surface area to volume ratio

Question 61

Use ideas about surface area to explain the shape of a leaf

Answer 61

Most leaves are broad and so have a large surface area

Question 62

What do cells use diffusion for

Answer 62

To take in substances they need and get rid of waste products

Question 63

When is oxygen and carbon dioxide transferred between cells and environment

Answer 63

During gas exchange

Question 64

Where does gas exchange take place in the lungs

Answer 64

Alveoli

Question 65

How are alveoli adapated for maximise diffusion

Answer 65

Enormous surface area Thin walls Moist lining