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17 Cards in this Set
- Front
- Back
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Define active transport. |
AT is the movement of molecules or ions into or out of a cell from a region of lower concentration to a region of higher concentration. |
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What does the process of AT require? |
Energy and carrier proteins. |
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Why is energy needed in active transport? |
As the particles are being moved up a concentration gradient in the opposite direction to diffusion. |
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What is metabolic energy supplied by in active transport? |
ATP. |
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What do the carrier proteins do in active transport? |
The proteins span the membranes and act as pumps. |
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Describe the general process of active transport. Six steps. |
1. The molecule or ion to to be transported binds to receptors in the carrier or channel protein outside of the cell. 2. Inside of the cell the ATP binds to the carrier protein and is hydrolysed to ADP and phosphate. 3. The protein changes shape because the phosphate molecule binds to the carrier protein - this opens up the inside of the cell. 4. The molecule or ion is released to the inside of the cell. 5. The phosphate molecule is released from the carrier protein and recombines with ADP to from ATP. 6.The carrier protein returns to its original shape. |
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The process of active transport is selective, why? |
Specific substances are transported by specific carrier proteins. |
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What is another form of active transport? |
Bulk transport. |
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What is bulk transport? |
Large molecules such as enzymes , hormones and whole cells like bacteria are too large to move through channel or carrier proteins so they are moved into and out of the cell by bulk transport. |
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Define endocytosis.
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The bulk movement of materials into cells. |
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There are two types of endocytosis. What are they and state what they are for. |
Phagocytosis for solids and pinocytosis for liquids - the process is the same for both. |
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Describe the process which is the same for both endocytosis and exocytosis. |
The cell-surface membrane first invaginates (bends inwards) when it comes into contact with the material to be transported. The membrane enfolds the material until eventually the membrane fuses, forming a vesicle. The vesicle pinches off and moves into the cytoplasm to transfer the material for further processing within the cell. Example - vesicles containing bacteria are moved towards lysosomes where the bacteria are digested by enzymes. |
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What is exocytosis? |
The reverse of endocytosis - vesicles move towards and fuse with the cell surface membrane - the contents of the vesicle are then released outside of the cell. |
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Where are vesicles usually made? |
Golgi apparatus. |
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In active transport what is energy in the form of ATP required for? |
he movement of vesicles along the cytoskeleton, changing the shape of cells to engulf materials and the fusion of cell membranes as vesicles form or as they meet the cell-surface membrane. |
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What is one similarity between active transport and facilitated diffusion? |
They both use carrier proteins. |
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What is one difference between active transport and facilitated diffusion? |
Facilitated diffusion occurs down a concentration gradient therefore does not require energy. |
