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Level 2 Biology > Passive Transport > Flashcards

Flashcards in Passive Transport Deck (24):
1

Define Diffusion

The net movement of particles from an area of high concentration to an area of low concentration.

2

Define Osmosis

The spontaneous net movement of water molecules across a semi permeable membrane from areas of lower solute concentration to areas of higher solute concentration.

3

Define Semi Permeable Membrane

A semi permeable membrane is a type of biological membrane that will allow certain molecules or ions to pass through it via a transport mechanism (diffusion, osmosis, facilitated diffusion or active transport).

4

Define Tonicity

The relative concentration of solutes dissolved in solution which determine the direction and extent of diffusion.

5

Define Hypotonic

Having a lower osmotic pressure than a particular fluid.

6

Define Hypertonic

Having a higher osmotic pressure than a particular fluid.

7

Define Isotonic

Having the same osmotic pressure as another fluid.

8

Define Osmotic Pressure

The pressure that would have been applied to a pure solvent to prevent it from passing into a given solution by osmosis and is often used to express the concentration of a solution.

9

Define Facilitated Diffusion

Facilitated diffusion is the process of spontaneous passive transport of molecules or ions across a cell's membrane via specific transmembrane integral proteins.

10

Does diffusion require energy to occur?

Because diffusion is a form of passive transport, it does not require energy to occur.

11

Explain the surface area:volume ratio

The smaller an object is, the larger its surface area relative to its volume. Therefore smaller objects have the largest surface area:volume ratio, while larger objects have smallest surface area:volume ratio.

12

Why is diffusion less efficient in large multicellular organisms than in single celled organisms?

Diffusion is only effective over a certain distance. As the distance over which the particles have to diffuse increases, the process becomes less efficient.
Therefore diffusion is much less efficient in large multicellular organisms compared to single celled organisms.

13

What effect does the inefficiency of diffusion in multicellular organisms have on the organism?

The inefficiency of diffusion in multicellular organisms means the process in inadequate for supplying nutrients and removing waste from the cells of such organisms.
Therefore the evolution of multicellular organisms required the development of tissues specialised for supplying nutrients and removing waste from cells.

14

What do specialised transport systems do?

Specialised transport systems (such as the circulatory system, the respiratory system and the digestive system) allow large organisms to exchange substances between their internal and external environment without relying solely on the process of diffusion.

15

Why is osmosis a vital process in biological systems?

Osmosis is the main way in which water is transported into and out of cells. When a cell is submerged in water, the water will move into or out of the cell depending on whether the solute concentration outside the cell is higher or lower than the solute concentration inside the cytoplasm of the cell. This makes osmosis a vital process in biological systems.

16

What does it mean when the a cells external environment is hypotonic relative to the cells cytoplasm?

When a cell is placed in fresh water, the concentration of solutes in the cell's cytoplasm is higher than the external environment. The cell will gain water under these conditions as water moves from an area of low solute concentration to an high solute concentration via osmosis. In this situation we say that the cell's external environment is hypotonic relative to the cell's cytoplasm.

17

What does it mean when the a cells external environment is hypertonic relative to the cells cytoplasm?

When a cell is placed in salt water, the concentration of solutes in the cell's cytoplasm will be lower than the cell's surrounding environment. The cell will lose water under these conditions as water will move from the region with a lower solute concentration (inside the cell) to the region with a higher solute concentration (outside the cell) via osmosis. In this situation we say that the cell's external environment is hypertonic relative to the cell's cytoplasm.

18

What does it mean when the a cells external environment is isotonic relative to the cells cytoplasm?

When a cell is placed in a solution which has the same concentration as the cell's cytoplasm, there isn't an osmotic gradient. In this situation water molecules will pass in and out of the cell at the same rate and there will be no net charge in the volume of the water in the cell. In this situation we say that the cell's external environment is isotonic relative to the cell's cytoplasm.

19

What happens when a plant and animal cell are placed in hypotonic solutions?

When a plant cell is placed in a hypotonic solution it will gain water and expand to become turgid.
When an animal cell is placed into a hypotonic solution it will swell and burst; in red blood cells this is called haemolysis.

20

What happens when a plant and animal cell are placed in hypertonic solutions?

When a plant cell is placed in a solution which is hypertonic, water moves out of the cell causing it to shrink and eventually the cell will become plasmolysed.
When an animal cell is placed in a hypertonic solution the cell will shrink in a process called crenation.

21

What happens when a cell becomes plasmolysed?

The cell membrane separates from the cell wall due to lack of pressure.

22

How does facilitated diffusion differ from simple diffusion?

The key way in which facilitated diffusion differs from simple diffusion is that it requires special carrier proteins to move molecules and ions across a membrane.

23

What aids the transport of large polar molecules and ions?

The transport of large polar molecules and ions are aided by ion channels and carrier proteins which span the cell membrane.

24

What do ion channels and carrier proteins do?

Channels regulate the flow of small polar molecules or ions (eg chloride ions) across the membrane, while large molecules (eg amino acids and glucose) are transported by the transmembrane carrier proteins.