Exchanging Substances Pg.20

Question 1

How easily stuff _______ between an ___________ and its environment depends on its surface area to ________ ________.

Answer 1

Moves.
Organism.
Volume ratio.

Question 2

Organisms ________ ________ with their environment.

Answer 2

Exchange substances.

Question 3

Cells can use _______ to take in ________ from the environment, such as _______.

Answer 3

Diffusion.
Substances.
Oxygen.

Question 4

They also use diffusion to get rid of _______ _______ such as:
Carbon dioxide (from ________)
Urea (from the breakdown of _______) - urea diffuses from _____ into the blood plasma. It’s then removed from the body by the ________.

Answer 4

Waste products.
Respiration.
Proteins.
Cells.
Kidneys.

Question 5

You can _________ on organisms surface are to volume ratio.

Answer 5

Calculate.

Question 6

A ratio shows ______ ______ one value is compared to another. So a surface area to ______ ratio shows how big a shapes _______ is compared to its volume.

Answer 6

How big.
Volume.
Surface.

Question 7

The ________ the organism, the _______ it’s surface are is compared to its volume.

Answer 7

Larger.
Smaller.

Question 8

The ________ it’s surface are compared to its volume, the ________ it is for an organism to _________ _________ with its environment.

Answer 8

Smaller.
Harder.
Exchange substances.

Question 9

A bacteria cell can be represented by a 2um x 2um x 1um block.
Calculate the cells surface are to volume ratio.
(The um is menna have a longer part of the left of the u like a p but with a gap in the top).

Answer 9

Surface area:
(2x2) x 2 = 8
(2x1) x 4 = 8
8 + 8 = 16um squared

Volume:
2 x 2 x 1 = 4um cubed
So the surface area to volume ratio is 16 : 4, or 4 : 1.

Question 10

The human body has special surfaces for _______ to make sure that we can take in enough __________.

Answer 10

Diffusion.
Substances.

Question 11

Single-felled organisms have a _____ surface area compared to their volume.

Answer 11

Large.

Question 12

So, they can ______ all the substances they need across their surface ( the ______ _________ ).

Answer 12

Exchange.
Cell membrane.

Question 13

Multicellular organisms (such as animal), have a _______ surface area compared to their _____.

Answer 13

Smaller.
Volume.

Question 14

They can’t normally exchange enough _________ across their outside surface alone.

Answer 14

Substances.

Question 15

Instead,