Transport in out and of cells

Question 1

Diffusion is ?

Answer 1

the movement of particles of any substance in solution or particles of gas down the concentration gradient from an area of higher concentration to an area of lower concentration, until equilibrium is reached

Question 2

What 3 factors increase the diffusion rate?

Answer 2

-Bigger concentration gradient: the faster the rate of diffusion because the net movement from one side is greater
-Higher temperature: make diffusion rate faster because particles have more energy, so move around faster
-Larger surface area: faster rate of diffusion because more particles can pass through at once

Question 3

What size of molecules can diffuse through a cell membrane

Answer 3

Small molecules (oxygen, glucose, amino acids, water, glycerol)
Not big molecules(starch, proteins)

Question 4

What is osmosis?

Answer 4

Movement of water molecules from an area of higher water potential to one on lower water potential down the water potential gradient across a partially permeable membrane

Question 5

Name the dependent variables of the potato practical.

Answer 5

length and mass of potato chips

Question 6

Name the independent variable of the potato practical.

Answer 6

concentration of sugar solution

Question 7

Name two control variables for the potato practical.

Answer 7

• cut all chips from the same potato
• keep both at the same temperature.

Question 8

Name three things you can do to prevent error in the potato practical.

Answer 8

• make sure the scale is set to 0 before weighing the chips
• use a vernier caliper to measure the potato chips or use a cork borer to cut them.
• make sure potato cylinders are fully dried, so the excess water will not give a higher ending mass

Question 9

What is the formula for percentage change?

Answer 9

Percentage change= final value-original value/ original value x100

Question 10

What is active transport?

Answer 10

the movement of molecules from an area of lower concentration to an area of higher concentration against the concentration gradient, using ATP or energy

Question 11

Name two places where active transport occurs.

Answer 11

The gut taking in nutrients(glucose, amino acids) from the blood, root hair cells taking in nutrients(water, mineral ions)

Question 12

Why is active transport used in the gut

Answer 12

• there is a lower concentration of nutrient in the gut but a higher concentration of nutrients in the blood
• when there’s a higher concert ration of glucose and amino acids in the gut they diffuse naturally into the blood
• BUT, sometimes there’s a lower concentration of nutrients in the gut than in the blood, so the process of active transport is used.

Question 13

Why is active transport needed in root hair cells

Answer 13

The concentration of mineral is usually higher in the root hair cell than in the soil around them, so active transport is needed because diffusion cant be used to since the concentration area is already higher in the cell.

Question 14

What is a hypertonic solution?

Answer 14

• a solution with a higher concentration of solute dissolve in it.
• Therefore it has a lower water potential.

Question 15

What is a hypotonic solution?

Answer 15

• a solution with a lower concentration of solute dissolved in it.
• Therefore it is has higher water potential

Question 16

Volume=

Answer 16

length x width x height

Question 17

surface area (for a cube)=

Answer 17

length x width x number of sides

Question 18

What is the surface area to volume ratio of a cube which is 1 cm on all sides?

Answer 18

6:1

Question 19

Having a larger surface area to volume means …

Answer 19

More substances can be exchanged more efficiently

Question 20

Do unicellular (single-celled) organisms, gases and dissolved substances diffuse directly into or out of the cell, or do they need exchange surfaces adapted to make them more efficient.

Answer 20

• unicellular cells, gases and dissolved substances diffuse directly into or out of the cell across the cell membrane
• because they have a larger surface area compared to their volume, so enough substances can be exchanged across the membrane to supply the volume of the cell

Question 21

Why cant multicellular organisms not take in their substances via diffusion?

Answer 21

they have too small a surface area compared to their volume
- not enough substance can diffuse from the outside surface to supply their entire volume
- need a special exchange surface for efficient diffusion

Question 22

How are exchange surfaces adapted to maximise effectiveness?

Answer 22

• being thin: substances will have a shorter diffusion distance to travel
• large surface area: lots of substances can diffuse at once
• good blood supply in animals: creates a steep concentration gradient
• ventilation in gas exchange systems in animals: The moving blood and ventilated surfaces mean that a steep concentration gradient can be maintained

Question 23

How are alveoli adapted to maximise efficiency?

Answer 23

-made up of tiny air sacs: gives lungs enormous surface area
-moist lining for dissolving gases(but doesn’t affect rate of diffusion)
-very thin walls: wall of alveolus is only 1 cell thick. Walls of capillaries also 1 cell thick
-good blood supply: wall off alveoli are covered in capillaries

Question 24

What happens to plant cells in hypertonic solution

Answer 24

• water potential is higher on the inside than on the outside
  -water moves out of the cell down the water potential gradient
  -sap vacuole shrinks. Cell is not longer form
  -cell becomes flaccid, becoming plasmolysed

Question 25

What happens to plant cells in hypotonic solution

Answer 25

-cells have lower water potential than the solution - net movement of water into the cell - cytoplasm and vacuole push against the cell wall -cell swells, becomes **turgid**

Question 26

What happens to plant cells in isotonic solution

Answer 26

* -water potential is equal between cell and solution * -no net movement * -normal cell

Question 27

What happens to animal cells in hypertonic solution

Answer 27

- **water moves out of red blood cell** by osmosis - red blood cell have higher water potential than solution -**net movement of water out of the cell** -**shrivelled cells**

Question 28

Summarise the different types of transport and their differences.

Answer 28

**Diffusion**: * -movement of particles from an area of higher concentration to an area of lower concentration * -doesn’t require energy **Osmosis**: * -movement of water molecules across a partially permeable membrane from a region of higher water concentration to an area of lower water concentration. * -doesn’t require energy **Active Transport**: * -movement of particles against a concentration gradient * - requires energy

Question 29

How are villi adapted to maximise absorption?

Answer 29

- nutrients e.g. glucose and amino arise, are absorbed into the bloodstream from the small intestines - to aid absorption the inside of the small intestines are covered with millions of tiny projection called villi - villi create a **large surface area** (due to larger surface area to volume) so lots of digested food is **absorbed much more quickly into the blood** -They also have: - a **single layer** of surface cells (**shorter diffusion distance**) - a very **good blood supply** to assist quick absorption

Question 30

Where are the villi found?

Answer 30

The inside of the small intestines

Question 31

What gas is needed for photosynthesis?

Answer 31

Carbon dioxide

Question 32

How is the structure of a leaf adapted for the the dissuasion of gases in and out of it? Name 5

Answer 32

- **underneath of leaf is an exchange surface**, it’s covered by little holes called **stomata** - **oxygen** (produced in photosynthesis) and **water vapour** can also diffuse **out of the stomata** (water vapour is actually lost from all over the leaf, but mostly through the stomata) - **size of stomata is controlled by guard cells**: these close of the plant is losing water faster than it is being replaced by the roots. Without guard cells the plant would soon **wilt** - **flattened shape** of leaf increases the surface area of exchange surface so it’s more effective - **wall of the cells** inside the leaf form another exchange surface. **Air spaces** inside leaf increase the area of this surface so there’s more chance for carbon dioxide to enter the cells.

Question 33

Now do the gills work as a gas exchange surface?

Answer 33

1. **Water containing oxygen** enters the fish’s mouth and passes **out** through the **gills** 2. As this happened, **oxygen diffuses** from the **water into the blood** in the gills and **carbon dioxide diffuse out** of the blood into the water. 3. Each gill is made up of lots of thin plates called **gill filaments**: give **large surface area(increase rate of diffusion)** 4.Gill filaments are covered in lots of tiny structure called **lamellae** 5.**Lamellae have lots of blood capillaries** to speed up diffusion between water and blood 6.Lamellae also have **thin surface layer of cells** to minimise the distance the gases have to diffuse. 7. **Blood flows through the lamellae in one direction** and **water flower over in the opposite direction**. This maintains a **large concentration gradient** between the water and the blood 8. Concentration of oxygen in the water is always higher than that in the blood so as much uxygen as possible diffuses from the water into the blood

Question 34

How does temperature affect the rate of diffusion?

Answer 34

- increase temperature on environment —> **increases kinetic energy** of the molecules - molecules move and mix **faster** - **increased rate of diffusion**

Question 35

5 ways the small intestines are adapted to make the absorption of nutrients more efficient

Answer 35

- **thin lining** - reduce diffusion distance - **many capillaries** - increase blood supply + maintains steep concentration gradient - walls form **villi** - increase SA - contains **lacteals** - for absorption of fatty acids + glycerol - **layer of muscle** - allow **peristalsis** to occur to move digested food through small intestine

Question 36

how are fish gills adapted for exchange f oxygen + carbon dioxode

Answer 36

- **many gill filaments** - larger SA - **thin** gills - short diffusion distance - **good blood supply** - maintain steep concentration gradient - **water continuously flows** over gills - maintain steep concentration gradient

Question 37

how are leaves adapted for the exchange of oxygen and carbon dioxide for photosynthesis

Answer 37

- **broad + flat** plant leaves - larger SA - **thin** leaves - shorter diffusion distance

Question 38

funtion of stomata and guard cell

Answer 38

- allow **gas exchange** between atmosphere and air spaces - **water vapour** diffuses **out stomata**