Fundamentals of gas exchange and SA:V ratio

What is gas exchange in the simplest sense?

The physical process by which gases move passively by diffusion across a surface.

What is gas exchange in a biological sense?

The process through which gases are transferred across cell membranes to either enter or leave the body of an organism.

What gases are exchanged in humans?

Oxygen enters and carbon dioxide leaves the body.

Where does gas exchange occur in humans?

First in the lungs and then in individual cells.

Why is gas exchange essential for living organisms?

It is necessary to capture and use energy required for life processes.

Name two metabolic processes that require gas exchange.

Respiration and photosynthesis.

Give two additional reasons why gas exchange is important in living organisms.

Waste removal and homeostasis.

How does surface area to volume ratio affect organism size?

As size increases, surface area to volume ratio decreases, limiting gas exchange efficiency.

Why does increased organism size limit gas exchange?

Greater diffusion distances and higher metabolic demand from increased volume.

How does metabolic rate change as organism size increases?

Metabolic rate per gram of body weight decreases as size increases.

What gas exchange mechanism do unicellular organisms use?

Diffusion across the cell membrane.

Why can unicellular organisms rely on diffusion for gas exchange?

They have a high surface-area to volume ratio.

How do insects carry out gas exchange?

Using a tracheal system of tubes that deliver oxygen directly to tissues.

What structures provide gas exchange in large organisms?

Specialised structures such as gills, lungs, and spongy mesophyll.

Why do large organisms need specialised gas exchange surfaces?

They have small surface-area to volume ratios.