Exchange

Question 1

What is the environment around cells called?

Answer 1

Tissue Fluid

Question 2

Name two ways exchange can take place

Answer 2

Passively or actively

Question 3

Name five features of a specialised exchange surface

Answer 3

• A large surface area relative to the volume
• Thin
• Selectively permeable
• Movement of the environmental medium
• A transport system.

Question 4

What makes up the network for gas exchange in insects?

Answer 4

Trachea which branch out into tracheoles that extend through the insects body

Question 5

Name three ways gasses move in and out of the tracheal system.

Answer 5

• Along a diffusion gradient,
• Mass transport,
• The ends of the tracheoles are filled with water.

Question 6

How does the ends of tracheoles filing with water increase the rate of gas exchange in insects during a period of major activity?

Answer 6

Muscles around tracheoles respire and produce lactic acid, reducing the water potential. Cells draw in water and this movement causes water to be pulled in though the spiracles.

Question 7

Why do insects keep their spiracles closed most of the time?

Answer 7

To prevent water loss.

Question 8

Describe the structure of the gills in a fish

Answer 8

Made up of gill filaments which are covered in lamellae to increase the surface area.

Question 9

What is counter current flow?

Answer 9

The blood moves in the opposite direction to the flow of water to maintain a constant high concentration gradient.

Question 10

How are gasses transported in plants?

Answer 10

Through diffusion

Question 11

How are leaves of a plant adapted for gas exchange?

Answer 11

• No cell is far from a stomata,
• Numerous interconnecting air spaces in the mesophyll bringing gasses into contact with it throughout the leaf.
• Large surface area of the mesophyll for rapid diffusion

Question 12

What are stomata?

Answer 12

Small pores which occur mainly on the underside of the leaf and is surrounded by a pair of guard cells which control when it is opened and closed.

Question 13

Name three insect adaptations to reduce the loss of water.

Answer 13

• Spiracles
• Waterproof coverings
• Small surface area to volume ratio.

Question 14

What is a xerophyte?

Answer 14

A plant adapted to living in extreme conditions where there is a lack of water.

Question 15

Name 5 adaptations of plants to reduce water loss.

Answer 15

• Thick cuticle,
• Rolling up leaves,
• Hairy leaves,
• Stomata in pits or grooves,
• A reduced surface area.

Question 16

Why are the lungs in mammals located inside the body?

Answer 16

• Air is not dense enough to support their delicate structure,
• We would lose a lot of water otherwise.

Question 17

Describe the human gas exchange system.

Answer 17

The trachea is the tube that air comes through down the throat, this branches off into two bronchi, one going to each lung. These branch out further into bronchioles which end in the alveoli.

Question 18

Why is there collagen and elastic fibres in between the alveoli?

Answer 18

To allow the alveoli to stretch when they fill with air.

Question 19

Describe inspiration.

Answer 19

External ICM contract and internal ICM relax. Rips are pulled up and out. Diaphragm contracts. Air in forced in as pressure decreases in the lungs.

Question 20

Describe expiration.

Answer 20

External ICM relax and internal ICM contract. Rips move own and in. Diaphragm relaxes. Air is forced out as pressure increases in the lungs.

Question 21

State 4 reasons why transfer of oxygen is rapid in the lung.

Answer 21

• Alveoli and capillaries have a very large surface area,
• Red blood cells are slowed as they pass through the capillaries allowing time for gas exchange,
• Short diffusion pathway as alveoli walls are thin and red blood cells are pressed against capillary walls,
• Breathing ensures there is a high concentration gradient maintained as does blood flow through capillaries.

Question 22

What are the two stages of digestion?

Answer 22

• Physical breakdown

- Chemical breakdown.

Question 23

What is the function of amylase?

Answer 23

Breakdown of starch into maltose

Question 24

What breaks down maltose and what does it breakdown into?

Answer 24

Maltase, a-glucose

Question 25

Why is maltase considered a membrane bound disaccharide?

Answer 25

It is part of the membranes of the cells which line the ileum.

Question 26

Describe lipid digestion.

Answer 26

Lipids are broken down into micelles by bile salts produced in the liver. They are then hydrolysed by lipases.

Question 27

Name three proteases.

Answer 27

Endopepdidase, exopeptidase, dipeptidase.

Question 28

How are triglycerides digested?

Answer 28

The micelles break down into fatty acids and monoglycerides which diffuse across the membranes of the cells lining the ileum. They reform into triglycerides at the endoplasmic reticulum then are associated with cholestrol and lipoproteins at the golgi. The they leave the cell.

Question 29

Whats a triglyceride that has been associated with cholesterol and lipoproteins called?

Answer 29

Chylomicrons.