Module 3 Section 1 - Specialised Exchange Surfaces

Question 1

What do organisms need to do with their environment

Answer 1

They need to exchange substances

Question 2

What do cells need to take in

Answer 2

Things like oxygen and glucose for aerobic respiration and other metabolic reactions

Question 3

What do cells need to excrete

Answer 3

Waste products from metabolic reactions e.g. carbon dioxide and urea

Question 4

What decides how easily the exchange of substances is

Answer 4

The organism’s surface area to volume ratio

Question 5

Multicellular organisms need….

Answer 5

Exchange surfaces

Question 6

In singled celled organisms substances such as glucose and oxygen can…

Answer 6

Diffuse directly into or out of the cell across the cell surface membrane

Question 7

Why is the diffusion rate quick in single celled organisms

Answer 7

Because there is a short distance that the substance have to travel

Question 8

Why is diffusion across the outer membrane of multicellular animals too slow

Answer 8

-some cells are deep within the body, big distance between the cell and outside environment
-larger animals have a low surface area to volume ratio, difficult to exchange enough substances to supply a large volume animal through a relatively small outer surface
-multicellular organism have a higher metabolic rate meaning glucose and oxygen is used up fast

Question 9

What specialised features do exchange surfaces have to improve their efficiency

Answer 9

-Large Surface area
-Thin layers
-Good blood supply and/or ventilation

Question 10

Give an example of an exchange surface with a large surface area

Answer 10

Root hair cells

Question 11

What gives plant roots a large surface area

Answer 11

The cells on the plant roots grow into long hairs which stick out into the soil

Question 12

What is the benefit of having the root hair cells

Answer 12

Gives the roots a large surface area which helps to increase the rate of absorption of water (by osmosis) and mineral ions (by active transport) from the soil

Question 13

Give an example of an exchange surface which is thin

Answer 13

The alveoli

Question 14

The alveoli is the site of what

Answer 14

Gaseous exchange in the lungs

Question 15

What is the alveolus made of

Answer 15

A single layer of thin flat cells called alveolar epithelium

Question 16

What diffuses out of the alveolar space in gaseous exchange

Answer 16

O2 diffuse out of the alveolar space into the blood. CO2 diffuses in the opposite direction

Question 17

How does the alveolar epithelium increase the rate of diffusion

Answer 17

The alveolar epithelium is thin this decreases the distance over which O2 and CO2 diffusion takes place

Question 18

Give examples of exchange surfaces which have good blood supply and/or ventilation

Answer 18

Alveoli
Fish gills

Question 19

How are the alveoli adapted to have a good blood supply

Answer 19

Each alveolus has its own blood supply because they are surrounded by a large capillary network this helps to bring a steep concentration gradient as the blood takes O2 away and brings CO2

Question 20

How are the alveoli adapted to have a good ventilation

Answer 20

The air in the alveoli is constantly being replaced every time you breathe in and out this helps to maintain a steep concentration gradient

Question 21

How are fish gills adapt to have a good blood supply

Answer 21

They contain a large network of capillaries meaning O2 and CO2 are constantly being exchanged which maintains a steep concentration gradient

Question 22

How are fish gills adapted to have good ventilation

Answer 22

Fresh water is constantly being passed over them - this brings a steep concentration gradient