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20 Cards in this Set

  • Front
  • Back

What are the 6 methods of transport across a cell membrane?

1 - Diffusion

2 - Osmosis

3 - Facilitated diffusion

4 - Active Transport

5 - Exocytosis

6 - Endocytosis

Which forms of transport are passive (don't require energy)?

Diffusion, osmosis, facilitated diffusion.

Which forms of transport do require energy?

Active Transport, Endocytosis and Exocytosis

Which form of transport requires carrier proteins and channel proteins?

Facilitated diffusion

Which form of transport involves the use of only carrier proteins/pumps?

Active transport

What is osmosis?

The net movement of water molecules from a high concentration to low concentration through a partially permeable membrane.

Why is facilitated diffusion necessary when diffusion can already occur?

• Diffusion though the phospholipid bilayer can occur more easily for smaller molecules like O2 and H2O.

Larger molecules like glucose and amino acids, as well as charged particles are insoluble in lipids and so their diffusion through the cell membrane needs facilitating.

How does facilitated diffusion through a carrier protein occur?

• An ion or molecule, in the blood or tissue fluid, bond to a specific site on its complementary carrier protein.

• This causes the protein to change shape and release the ion or molecule into the cell cytoplasm.

How does facilitated diffusion through channel proteins occur?

• Channel protein opens in response a signal (e.g. hormone, voltage change).

• This forms a pore in the cell membrane that allows a specific charged particle to diffuse through.

• Channel protein closes also in response to a signal.

What is ATP, when is it formed and what is it used for?

• Adenine Triphosphate.

Formed during respiration and the breakdown of storage molecules.

hydrolysis of ATP provides an immediate source of energy for all biological processes.

What are carrier proteins in active transport also referred to as?

Active transport pumps

Why does active transport require energy from ATP?

Moves molecules and ions against a concentration gradient (Low to high).

How does active transport occur?

ATP is hydrolysed into ADP and Pi, this releases energy.

This energy forms a bond between the transport molecule and the transport protein.

This causes the transport protein to change shape, releasing the transport molecule into the cell.

What is Exocytosis?

The bulk transport of molecules out of cells.

What is Endocytosis?

The bulk transport of molecules into cells.

When is Exocytosis used?

• When substances produced by the cell (e.g. hormones, digestive enzymes, lipids ect...) need to be released from the cell.

Describe the process of Exocytosis

Vesicles containing substances pinch off from sacs on the Golgi apparatus and are guided towards the cell membrane.

The vesicles fuse with the cell membrane and release their contents outside of the cell, this requires ATP.

Why are some substances moved into cells by endocytosis?

Too large to be taken into the cell by carrier proteins.

Describe the process of Endocytosis?

• The substance interacts with the cell membrane, some substances (like cholesterol) bind to membrane receptors.

• The cell responds by having a section of cell membrane form a vesicle around the substance, this requires ATP.

The vesicle pinches off inside the cell containing the ingested substance.

Give an example of a cell group whos function is primarily to ingest substances?

White blood cells (phagocytes) use Endocytosis to take in microorganisms and dead cell fragments so that they can be digested/destroyed.