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20 Cards in this Set
- Front
- Back
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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 |
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Which forms of transport are passive (don't require energy)? |
Diffusion, osmosis, facilitated diffusion. |
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Which forms of transport do require energy? |
Active Transport, Endocytosis and Exocytosis |
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Which form of transport requires carrier proteins and channel proteins? |
Facilitated diffusion |
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Which form of transport involves the use of only carrier proteins/pumps? |
Active transport |
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What is osmosis? |
The net movement of water molecules from a high concentration to low concentration through a partially permeable membrane. |
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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. |
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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. |
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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. |
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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. |
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What are carrier proteins in active transport also referred to as? |
Active transport pumps |
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Why does active transport require energy from ATP? |
Moves molecules and ions against a concentration gradient (Low to high). |
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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. |
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What is Exocytosis? |
The bulk transport of molecules out of cells. |
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What is Endocytosis? |
The bulk transport of molecules into cells. |
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When is Exocytosis used? |
• When substances produced by the cell (e.g. hormones, digestive enzymes, lipids ect...) need to be released from the cell. |
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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. |
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Why are some substances moved into cells by endocytosis? |
• Too large to be taken into the cell by carrier proteins. |
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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. |
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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. |
