Animal Structure and Function

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Gaseous Exchange

Gaseous Exchange

The alveoli are adapted for important gas exchange via diffusion between air in the lungs and blood in capillaries.

Do you remember what the composition of inhaled and exhaled air is? Choose the right values from the options provided.

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Why is there more oxygen in the air we breathe in than in the air we breathe out, and why is it the other way around for carbon dioxide? Pick the most correct option.

Where do you think gaseous exchange takes place? Pick all the options you think are correct.

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Gaseous exchange in the lungs takes place in the alveoli

The surface that gases move across should be very thin (a single layer of cells, usually), be moist, have a large surface area and it should have a good transport system that carries gases to and from the exchange surface.

Air enters the alveolus

We breathe in air with a high $O_{2}$ concentration and low $CO_{2}$ concentration. Some of the $O_{2}$ and $CO_{2}$ dissolves in the water, lining the inside of the alveoli.

Where do you think the $O_2$ concentration is higher?

A) In the blood in the capillary on the outside of the alveoli B) In the water, lining the inside of the alveoli

The movement of oxygen

$O_{2}$ moved from the higher concentration in the water that lines the alveoli to the lower concentration in the blood in the capillary on the outside of the alveoli.

What do we call the process where particles and substances move from higher to lower concentration, like the $O_{2}$ that moves from the water lining to the blood in the alveoli?

The movement of carbon dioxide.

$CO_{2}$ is a waste product of cellular respiration. The blood carries it from the cells to the capillaries around the alveoli. It diffuses in the opposite direction to $O_2$ because the concentration of $CO_{2}$ in the blood is higher **** than the concentration in the water lining the alveoli.

Select all the characteristics needed for an effective gas exchange surface.

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When the concentration of particles in one area is higher than the concentration in another area, it is known as a ....

The alveoli have adapted to make the rate of diffusion of $O_2$ and $CO_2$ as effective as possible.

A large surface area

The more space there is for molecules to move from one place to another, the quicker they can move.

A short diffusion distance

The walls of the alveoli and surrounding capillaries are each only one cell thick. Molecules can diffuse quicker if they don't have too far to move.

A steep concentration gradient

A concentration gradient is when there's a difference between two concentrations. If this difference is large, substances will diffuse faster.

We use the word _______ to refer to the amount of substance in a defined space.

Would you say the relationship between distance and the rate of diffusion is directly or inversely proportional?

Fick's law of diffusion states that $rate\enspace of\enspace diffusion\enspace {\displaystyle \propto } \frac{surface\enspace area \times concentration\enspace difference}{thickness\enspace of\enspace membrane}$

What do you think would happen to the rate of diffusion if the thickness of a membrane doubled?