transport across membrane Flashcards

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1
Q

cell surface membrane

A
  • made almost entirely of protein and phospholipids
  • phospholipid molecule has
  • a head: composed of a glycerol to which is attached to a phosphate group (hydrophilic, forms hydrogen bonds with water)
  • 2 fatty acid tails (hydrophobic, comprises of 2, long, fatty acid residues consisting of hydrocarbon chains)
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2
Q

responses to water

A
  • when phospholipid is added to water, the molecules float with their hydrophilic “heads” in contact with the water molecules and their fatty acid tails exposed and away from the water
  • phospholipid molecules arrange these;ves as a phospholipid bilayer with fatty acid tails (hydrophobic) facing each other (within the cell membrane)
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3
Q

protein of membrane

A
  • partially/fully embedded in the lipid bilayer

- superficially attached on either surface of the lipid bilayer

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4
Q

simple diffusion

A
  • form of passive transport
  • from regions of higher concentrations to regions of lower concentrations
  • molecules of non-polar substances (e.g. glycerol, fatty acids
  • phospholipid bilayer fully permeable to non-polar, but forms a barrier to ions, large and polar substances
  • transient pores in phospholipid permits small and uncharged substances (gases) to pass through
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5
Q

facilitated diffusion

A
  • diffusion through cell membranes using specific protein channel/carriers from regions of higher concentration to lower concentration
  • polar molecules (e.g. water in high concentration)
  • channel/carrier proteins are large enough for a specific substances to pass through (inions, large and polar substances)
    e. g. sodium ions, amino acids
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6
Q

osmosis

A
  • net movement of water molecules from a region of a higher to lower water potential through a selectively permeable membrane
  • equilibrium is reached when the water potential is the same in both regions
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7
Q

active transport

A
  • the process in which energy in the form of ATP is used to move substances across a membrane against a concentration gradient (lower to higher)
  • occurs against concentration gradient
  • requires energy in the form of ATP
  • active uptake is a highly selective process, only substances needed are taken up
  • involves a “protein pump’ at membrane (membranes are specific to particular substances)
  • cell surface membrane of root hair cells use active transport to absorb mineral salts needed
  • cell surface membrane of intestinal epithelial cell to absorb nutrients (e.g. glucose and amino acids from intestine)
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8
Q

bulk transport

A
  • occurs by movement of vesicles of matter (solids or liquids) across the cell surface membrane
  • ATP is required
  • exocytosis: process bu which cells export products such as enzymes by means of vesicles
  • endocytosis: substances imported into cells
    2 types of endocytosis
    1. phagocytosis: wholesale import of solid matter
    2. pinocytosisL bulk import of fluids
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