Topic 3- exchange of substances

Question 1

insect tracheoles have thin walls. How does this increase the efficiency of gas exchange?

Answer 1

it means there is a short diffusion distance to cells

Question 2

Insects have a large number of highly branched tracheoles. How does this increase the efficiency of gas exchange?

Answer 2

it means there is a short diffusion distance to cells and a large surface area for gas exchange

Question 3

Insect tracheae are full of air. How does this increase the efficiency of gas exchange?

Answer 3

it means that gases diffuse quickly into tissues

Question 4

Fluid in the ends of tracheoles moves out into tissues during exercise. How does this increase the efficiency of gas exchange?

Answer 4

the final diffusion pathway is gas rather than liquid, so diffusion to the gas exchange surface is faster and the surface area for gas exchange is larger

Question 5

Insects can use their muscles to move air through tracheae. How does this increase the efficiency of gas exchange?

Answer 5

maintains a steep diffusion gradient for oxygen and carbon dioxide

Question 6

define counter-current flow

Answer 6

When two materials flow in opposite directions to maintain a concentration gradient

Question 7

What is a stoma?

Answer 7

A pore, usually found in the lower epidermis of a leaf, through which gases diffuse

Question 8

In the mammalian gas exchange system, what is the trachea?

Answer 8

A flexible airway lined with cells, and supported by rings of cartilage, through which air moves towards and away from the lungs

Question 9

In humans, the trachea and large bronchi are supported by cartilage. How does this adaptation support their function?

Answer 9

It prevents airways from collapsing when air pressure drops when breathing in

Question 10

In humans, the trachea and bronchi are lined with cilia. How does this adaptation support their function?

Answer 10

cilia move mucus towards the throat

Question 11

How are alveoli adapted for efficient gas exchange?

Answer 11

the alveolar epithelium is one cell thick which creates a short diffusion pathway for gas exchange

Question 12

What is maltase?

Answer 12

an enzyme that hydrolyses maltose to form glucose

Question 13

What is an endopeptidase?

Answer 13

an enzyme which acts in the middle of a polypeptide and hydrolyses peptide bonds to produce shorter polypeptides

Question 14

What is an exopeptidase?

Answer 14

an enzyme which acts at the end of a polypeptide and hydrolyses peptide bonds to form dipeptides and amino acids

Question 15

What is a dipeptidase?

Answer 15

an enzyme which acts on a dipeptide and hydrolyses peptide bonds to form amino acids

Question 16

What is haemoglobin and its structure?

Answer 16

A protein enabling transport of oxygen in the blood. It has a quaternary structure and four prosthetic haem groups which are able to bind oxygen.

Question 17

Define myocardial infarction.

Answer 17

Blood flow in the coronary arteries reduces, so the amount of oxygen reaching the heart muscle reduces. So cells respire less and start to die.

Question 17

Blood vessels generally contain an outer layer of collagen. What is its function?

Answer 17

it resists changes in pressure

Question 18

Blood vessels generally contain a muscle layer. What is its function?

Answer 18

to contact to control the flow of blood

Question 18

Blood vessels generally contain an elastic layer. What is its function?

Answer 18

to stretch and recoil to maintain blood pressure

Question 19

Blood vessels are lined with an endothelium layer. How is it adapted to its function?

Answer 19

it is smooth to reduce friction with the blood

it is one layer thick for rapid diffusion

Question 19

How is the muscle layer in arteries adapted to its function?

Answer 19

It is thicker than the muscle layer in veins so that small arteries can constrict and dilate to control the volume of blood passing to the tissue

Question 20

How is the elastic layer in arteries adapted to its function?

Answer 20

it is thicker than the elastic layer in veins to maintain high blood pressure so that blood reaches the extremities. The stretch and recoil of the elastic wall helps to smooth the pressure surges resulting from the heartbeat.

Question 21

How is the artery wall adapted to its function?

Answer 21

it is thick to help prevent the artery bursting under pressure

Question 22

How is the valve system in arteries adapted to its function?

Answer 22

there are no valves in the arteries, as the constant high pressure helps prevent blood from flowing backwards

Question 23

How is the lumen in veins adapted to its function?

Answer 23

it is large so it can carry a large volume of slow-moving blood

Question 24

How is the muscle layer in veins adapted to its function?

Answer 24

It is thinner than the muscle layer in arteries.

Veins carry blood away from tissues and so constriction and dilation can’t affect the volume of blood passing to tissues.

Question 25

how is the elastic layer in veins adapted to its function?

Answer 25

it is thinner than the elastic layer in arteries.

Lower blood pressure reduces the risk of bursting and does not create a recoil action.

Question 26

How is the vein wall adapted to its function?

Answer 26

it is thinner as low pressure reduces the risk of bursting

Question 27

How is the valve system in veins adapted to its function?

Answer 27

valves ensure that, despite low blood pressure, blood does not flow backwards

Question 28

Capillaries are numerous and highly branched. How does this support their function?

Answer 28

provides large surface area for exchange

Question 29

Capillaries have a narrow diameter. How does this support their function?

Answer 29

they permeate tissues, so all cells are close to a capillary, reducing the diffusion distance and increasing the rate of diffusion.

Question 30

Capillaries have a narrow lumen. How does this support their function?

Answer 30

It means that blood cells press against the side wall, reducing the diffusion distance to nearby cells and increasing the rate of diffusion.

Question 31

Capillaries have spaces between endothelial cells. How does this support their function?

Answer 31

It allows white blood cells to escape and tackle infections in nearby tissues.

Question 32

Capillaries have extremely thin walls. How does this support their function?

Answer 32

Reduces the diffusion distance to nearby cells and increases the rate of diffusion.

Question 33

what is the xylem?

Answer 33

dead, hollow, elongated tube which transports water in most plants

Question 34

The xylem contains cells joined end to end with no end wall. Why does this make it a good transport system in plants?

Answer 34

it forms one continuous tube, which is essential for the cohesion-tension theory.

Question 35

the xylem contains dead cells. Why does this make it a good transport system in plants?

Answer 35

The cells do not use metabolic energy to move the water.

Movement of water would be slowed by the membrane and cytoplasm of a living cell.

Question 36

The xylem has thick walls containing lignin. Why does this make it a good transport system in plants?

Answer 36

it helps strengthen the xylem and prevents collapse

Question 37

What is phloem?

Answer 37

A tissue that transports the products of photosynthesis from the leaves to the rest of the plant.