Surface Area to Volume Ratio - Lesson 7

Question 1

Analogy of the Boat and the Island
Square island where a single person lives in every square meter of land and a supply boat can dock at every meter of coastline. Which grows faster - the interior or the coastline?

Answer 1

The interior

Question 2

What challenges are there when the interior grows faster than the exterior coastline in the boat/island scenario?

Answer 2

1. the number of supply boats per person decreases

2. have to spend more energy transporting supplies from the coastline to the “landlocked” inhabitants in the interior

Question 3

What is the relationship of a cell’s volume (internal size) to its cell membrane across which nutrients are exchanged (surface) called?

Answer 3

Surface Area to Volume Ratio - SA/V

Question 4

What two difficulties are faced when cells with a SMALL SA/V ratio (surface area is small in relation to their volume) are trying to sustain their large interiors?

Answer 4

1. Surface area is too small to take in the nutrients required and to remove the large amount of waste.
2. Requires a LOT of energy to distribute nutrients taken in at the cell membrane across the large interior of the cell.

Question 5

Effect of Cell Shape on SA/V Ratio
Some parts of large organisms are designed to maximize the diffusion of materials across cell membranes. What are three types?

Answer 5

1. Aveoli - in the lungs (maximize Oxygen and CO2 exchange)
2. Villi - in the intestines (maximize nutrient exchange into the bloodstream)
3. Root Hairs - on plants (maximizing WATER uptake from the soil)

Question 6

What do the AVEOLI do and where are they found?

Answer 6

Maximize Oxygen and CO2 exchange

Found in the lungs

Question 7

What do the VILLI do and where are they found?

Answer 7

Maximize nutrient exchange into the bloodstream.

Found in the intestines.

Question 8

What do the ROOT HAIRS do and where are they found?

Answer 8

Maximize WATER uptake from the soil

Found on plants.