Exchange of Materials

Question 1

What is Osmosis?

Answer 1

The movement of water

From an area of high concentration to an area of low concentration along a concentration gradient

From more dilute solution to higher concentration

Question 2

What does osmosis occur across?

Answer 2

A partially permiable membrane

Question 3

What is the movement of water molecules performing osmosis like?

Answer 3

Random

Question 4

What does osmosis not require from the cell?

Answer 4

Energy

Question 5

Cells may need to absorb substances in short supply. To do this, they may have to absorb susbtances…

Answer 5

…against the concentration gradient

Question 6

What is active transport?

Answer 6

The movement of susbtances across either a cell membrane or against a concentration gradient

It requires energy because of this

Question 7

Where does the energy for active transport come from?

Answer 7

Respiration

Question 8

How do root cells use active transport?

Answer 8

They absorb mineral ions from dilute solutions in the soil

Question 9

How do the kidneys use active transport?

Answer 9

Glucose can be reabsorbed in kidney tubes

Question 10

What specific substance dos active transport use?

Answer 10

A transport protein

It rotates, using energy

Question 11

What happens if you sweat a lot or do not drink enough water? (Or eat a lot of salty food)

Answer 11

You may become dehydrated

Question 12

What do sports drinks contain and why?

Answer 12

• Water to replace water lost by sweating
• Sugar to replace sugar used for respiration in exercise
• Mineral ions to replace those lost by sweating

Question 13

What does isotonic?

Answer 13

Having the same concentration of solutes as another solution

Question 14

What does it mean if a sports drink is isotonic?

Answer 14

The concentration of sugar, water, and mineral ions in the drink matches those in the body

Question 15

For normal levels of exercise, what might be just as effective as a sports drink?

Answer 15

A drink of water

Question 16

What do large organisms need and why?

Answer 16

Exchange surfaces

They need these to obtain all the food and oxygen they require

Question 17

What makes an exchange surface efficient?

Answer 17

• Large surface area
• Thin walls or short diffusion path
• Efficient transport system - bloody supply in animals

Question 18

What form of exchange takes place in the lungs?

Answer 18

The gaseous exchange

Question 19

What are alveoli and how do they make the gaseous exchange more efficient?

Answer 19

Tiny air sacks. They have:

• Thin walls
• Large surface area
• Good blood supply

Question 20

Why are the lungs ventillated and what does this mean?

Answer 20

Air is moved in and out

This maintains a steep diffusion gradient

Question 21

How does oxygen enter/carbon dioxide leave the blood surrounding the alveoli?

Answer 21

They diffuse into the many capillaries surrounding the alveoli

Question 22

Where are the lungs situated?

Answer 22

In the thorax

Question 23

Describe the position of the lungs

Answer 23

In the thorax, inside the ribcage, above the diaphragm

The diaphragm seperates the lungs from the abdomen

Question 24

What happens when we breathe in?

Answer 24

• The intercostal muscles between the ribs + diaphragm contract
• The ribcage moves up + out and the diaphragm flattens
• The volume of the thorax increases
• The pressure of the thorax decreases and air is drawn in

Question 25

What happens when we breathe out?

Answer 25

* The **intercostal muscles** between the ribcage + diaphragm **contract** * The **ribcage moves down + in** and the **diaphragm** becomes **domed** * The **volume** of the thorax **decreases** * The **pressure increases** and **air is forced out**

Question 26

Why might someone not be able to get enough oxygen into their bloodstream?

Answer 26

* The **alveoli are damaged** and the **surface area** for gas exchange is **decreased** * The **tubes leading to the lungs are narrowed** so less air can move through them * The person is **paralysed** so their muscles will not work to pull the ribcage up and out

Question 27

How does the 'iron lung' work?

Answer 27

* Person lay with **chest sealed in a large metal cylinder** * When **air was drawn out of the cylinder**, the person's **chest moved out** and they **breathed in** * The **vacuum** which was formed inside the cylinder created a **negative pressure** * When **air was pumped back in** to the cylinder, it **created pressure on the chest** and **forced air out** of the lungs

Question 28

What is negative pressure?

Answer 28

A system where the **external pressure is lower** than the internal pressure

Question 29

What is positive pressure?

Answer 29

A system where the **external pressure is higher** than the internal pressure

Question 30

Who was the iron lung used for?

Answer 30

People with polio who has been left paralysed as a result of the disease

Question 31

What type of artifical breathing aids use positive pressure?

Answer 31

Breathing aids which force measured amounts of air into the lungs Bags of air linked to masks can force air down the trachea

Question 32

Why might you use a positive pressure aid instead of a negative pressure aid?

Answer 32

* Smaller * Easier to manage in the home * Can be linked to computers for control

Question 33

What is the exchange surface for food molecules in the small intestine?

Answer 33

Villi

Question 34

What are villi and how do they work?

Answer 34

Small, finger-like projections which increase surface area for absorbtion to take place The walls are very thin and have many capilliaries close to them Rich blood supply provides a steep concentration gradient Soluble products of digestion can be absorbed either by diffusion or active transport

Question 35

How do gasses diffuse in and out of leaves?

Answer 35

Through tiny holes called stomata The size of these is controlled by the guard cells which surround them

Question 36

What gases diffuse in and out of leaves?

Answer 36

Oxygen - needed for respiration and a byproduct of photosynthesis CO₂ - Needed for photosynthesis and a waste product of respiration

Question 37

What does the movement of gases in out out of the leaf depend upon?

Answer 37

Which process (respiration or photosynthesis) is taking place the most quickly

Question 38

What do plants also lose through the stomata?

Answer 38

Water vapour due to evaporation in the leaves

Question 39

In what ways are the leaves an efficient exchange surface?

Answer 39

They are very flat and thin so the gases do not need to diffuse very far There are also internal air spaces

Question 40

If plants lose water faster than it is replaced by the roots, what might the stomata do?

Answer 40

Close to prevent wilting

Question 41

How do root hair cells provide an efficient exchange surface?

Answer 41

Increase the surface area of roots for the absorption of water and mineral ions

Question 42

Describe the structure of the leaf and what each layer does

Answer 42

* **Waxy cuticle** on upper epidermis - **waterproof** which stops water loss * Palisade layer * Spongy layer - **Cells not packed tightly**, **air spaces**, **large surface area** for gas exchange * Lower epidermis with **guard cells** - open and close stomata to control water loss

Question 43

What is the transpiration stream?

Answer 43

The movement of water through the plant. Goes from the roots to the leaves as a result of evaportation from the surface of the leaves

Question 44

When is evaportation in plants more rapid?

Answer 44

* Hot * Dry * Windy * Bright Any of these conditions

Question 45

What can be used to show how the uptake of water by a plant changes in different conditions?

Answer 45

A potometer It gives you a good idea of the water lost by transpiration

Question 46

What is wilting?

Answer 46

The process by which plants droop when they are short of water or too hot Reduces further dehydration and prevents cell damage by decreasing surface area