6. active transport

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6 Terms

1
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ACTIVE TRANSPORT- DEFINITION

  • movement of molecules against a concentration or electrochemical gradient

  • requires energy

<ul><li><p><span>movement of <mark data-color="red" style="background-color: red; color: inherit">molecules </mark>against a concentration or electrochemical gradient</span></p></li></ul><p></p><ul><li><p><span>requires <mark data-color="red" style="background-color: red; color: inherit">energy</mark></span></p></li></ul><p></p>
2
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ACTIVE TRANSPORT

  • molecule (e.g. glucose) binds to receptor site on the carrier protein

  • the molecule must be the correct shape to ‘fit’ the receptor to be transported

  • ATP (from respiration) attaches to the membrane protein on the inside of the cell

  • ATPase catalyses the hydrolysis of ATP into ADP which releases energy

  • this causes a change in shape of the protein

  • the molecule can now get in but not out

    ​

3
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ACTIVE TRANSPORT- IMAGE

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ACTIVE TRANSPORT- EVIDENCE

active transport requires energy in the form of ATP from cellular respiration

evidence for active transport comes from linking these two processes together i.e. showing that without ATP active transport can’t take place

  1. active transport only takes place in living things

  1. rate of active transport is dependent on temperature and oxygen conc-these affect respiration so ATP production

  1. cells known to carry out lots of active transport contain many mitochondria – site of cellular respiration

  1. poisons that stop respiration or prevent ATPase working also stop active transport

5
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ENDOCYTOSIS

  • materials can be surrounded by and taken up into membrane bound vesicles by endocytosis

  • this can happen on a large scale such as when WBCs ingest bacteria (phagocytosis)

  • can also happen on microscopic level when tiny amounts of surrounding fluid are taken into minute vacuoles (pinocytosis)

  • electron microscopes have shown this is very common as cells take in extracellular fluid as a source of nutrients and minerals

6
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EXOCYTOSIS

  • term for emptying of a membrane-bound vesicle at cell surface

  • e.g. in cells producing hormones, secretory vesicles from golgi containing the hormone fuse with the cell surface membrane releasing their contents

  • both endocytosis and exocytosis are made possible by the fluid nature of the cell membrane- formation of vesicles and fusing with cell membrane are active processes so ATP is required