Exchange Surfaces - Intro and Lungs

Question 1

define diffusion

Answer 1

the passive net movement of particles from a region of their higher concentration to a region of their lower concentration

Question 2

what factors affect the rate of diffusion

Answer 2

• concentration gradient
• diffusion distance
• surface area
• structure through which diffusion occurs e.g pores and larger pores increase rate
• size and type of molecule e.g small = faster and more soluble = faster

Question 3

what do organisms need a supply of

Answer 3

• oxygen
• nutrients
• water
• carbon dioxide (plants)

Question 4

what do organisms need to remove

Answer 4

• carbon dioxide
• water
• oxygen (plants)
• nitrogenous waste

Question 5

describe the problem of scale

Answer 5

as an organism gets bigger, both its volume and surface area increases, however surface area does not increase by as much as volume, so large organisms need to find ways to increase their surface area for gas exchange

Question 6

describe the relationship between size of an organism and surface area to volume ratio

Answer 6

as size increases, surface area to volume ratio decreases

Question 7

what are the features of a perfect exchange surface

Answer 7

• large surface area
• thin
• maintains concentration gradient
• protected from drying out

Question 8

describe the importance of surface area to a perfect exchange surface

Answer 8

the larger the area across which a substance can diffuse the more substance can cross in a given time

Question 9

describe the importance of being thin to a perfect exchange surface

Answer 9

the shorter the distance for a substance to diffuse the less time it takes

Question 10

describe the importance of maintaining a concentration gradient to a perfect exchange surface

Answer 10

concentration of the substance must be higher on one side than the other for diffusion down a concentration gradient to take place

Question 11

describe the importance of protection from drying out to a perfect exchange surface

Answer 11

in terrestrial animals water vapour diffuses out of cells on the surface, if too much is lost the plasma membrane will lose its structure and cells will die

Question 12

what are the muscles found on the ribs

Answer 12

• external intercostal muscle
• internal intercostal muscle

Question 13

how is an alveolus adapted to fulfil its role

Answer 13

• good blood supply maintains concentration gradient
• thin: 2 cell distance, walls one cell thick, squamous epithelial cells
• ventilation: breathing maintains high concentration gradient for O2 and CO2
• moist: gases diffuse faster in liquids, surfactant
• many alveoli: large surface area

Question 14

what does surfactant mean

Answer 14

reduces surface tension preventing alveolus collapsing

Question 15

what is the role of macrophages in lungs

Answer 15

• patrol alveolar surfaces
• scavenge for any harmful material e.g spores, bacteria, dust
• engulf anything that they find
• some substances cannot be digested e.g asbestos