Exchanging Substances Flashcards

Flashcards covering gas exchange in fish and plants, surface area to volume ratios, and alveoli in lungs.

What are gills?

The gas exchange surface in fish.

How does gas exchange happen in fish?

Water enters through the mouth and passes out through the gills; oxygen diffuses from the water into the blood, and carbon dioxide diffuses from the blood into the water.

What are gill filaments?

Thin plates that make up each gill, providing a large surface area for gas exchange.

What are lamellae?

Tiny structures covering the gill filaments that increase the surface area even more.

Why do lamellae have lots of blood capillaries?

To speed up diffusion.

Why do lamellae have a thin surface layer of cells?

To minimise the distance that gases have to diffuse.

Why does blood flow through the lamellae in one direction, while water flows over them in the opposite direction?

It maintains a large concentration gradient between the water and the blood, ensuring as much oxygen as possible diffuses from the water into the blood.

Where does carbon dioxide diffuse in a leaf?

They diffuse into the air spaces within the leaf, then into the cells where photosynthesis happens.

What are stomata?

Little holes on the underside of the leaf through which carbon dioxide diffuses in, and oxygen and water vapor diffuse out.

What is the role of guard cells?

These close the stomata if the plant is losing water faster than it is being replaced by the roots.

How does the flattened shape of a leaf aid in gas exchange?

It increases the area of this exchange surface so that it's more effective.

How do the air spaces inside the leaf help with gas exchange?

They increase the area of this surface so there's more chance for carbon dioxide to get into the cells.

What are villi?

Tiny projections covering the inside of the small intestine.

How do villi aid absorption?

They increase the surface area so that digested food is absorbed much more quickly into the blood.

What features do villi have that assist in quick absorption?

A single layer of surface cells, a very good blood supply, and a network of capillaries.

What is diffusion's role in exchanging substances?

Cells can use this process to take in substances they need and get rid of waste products.

What substances are exchanged via diffusion?

Oxygen and carbon dioxide between cells and the environment, and urea from cells into the blood plasma.

What does the ease of exchanging substances depend on?

It depends on the organism's surface area to volume ratio (SA:V).

How does size affect the surface area to volume ratio?

The larger an organism is, the smaller its surface area is compared to its volume.

How do single-celled organisms exchange substances?

Gases and dissolved substances can diffuse directly into (or out of) the cell across the cell membrane.

Why can single-celled organisms rely on diffusion across the cell membrane?

They have a large surface area compared to their volume.

Why do multicellular organisms need exchange surfaces?

Not enough substances can diffuse from their outside surface to supply their entire volume.

How are exchange surfaces adapted to maximize effectiveness?

A thin membrane, a large surface area, lots of blood vessels (in animals), and ventilation (in gas exchange surfaces).

What is the job of the lungs?

To transfer oxygen to the blood and to remove waste carbon dioxide from it.

What are alveoli?

Little air sacs in the lungs where gas exchange takes place.

How are alveoli specialized to maximize diffusion of oxygen and CO2?

An enormous surface area, a moist lining, very thin walls, and a good blood supply.