Gas Exchange

What is gas exchange?

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

Why is gas exchange vital for all organisms?

It is necessary to capture and use energy.

What is gas exchange needed for?

• respiration and photosynthesis

• metabolism

• waste removal

• homeostasis

• survival in various environments

• nutrient transport

• ecosystem balance

What is the relationship between SA:V and size?

It is inversely proportional to size.

What increases when a species increases in size?

The distance from the centre of the organism to its exterior

What decreases when a species increases in size?

Metabolic rate decreases

What do bacteria and protozoa have that aids in gas exchange?

High SA:V for gas exchange through their cell membrane.

What type of respiratory system do insects have?

A tracheal system consisting of a network of tiny tubes that branch through the insects body that deliver oxygen to cells.

What specialized structures do larger organisms have for gas exchange?

Specialized structures with convoluted surfaces such as gills and lungs that provide the large surface area needed for gas exchange.

Gas exchange surface

The surface tissue or membrane at the site of gas exchange in an organism

Gas exchange surfaces have unique features that enable gases to move efficiently:

• permeability

• thickness

• moisture

• surface area

Permeability

They must be selectively permeable to allow gases to pass while preventing fluid loss.

Thickness

Thin tissues minimize barriers for gases, ensuring rapid and efficient diffusion.

Moisture

Gases are more soluble in moist substances, allowing for higher rates of gas movement.

Surface area

Increases surface area allows for more gas molecules to be exchanges simultaneously

In cells - folds, projections

In organs = specialised structures like alveoli

What is the average number of alveoli in an adult human lung?

Between 300-500 million alveoli.