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54 Cards in this Set
- Front
- Back
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What is the plasma membrane? |
the boundary that separates the living cell from its surroundings |
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The plasma membrane exhibits selective permeability, which is what? |
allows some substances to pass more easily than others |
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What does the cellular membrane consist of? |
fluid mosaics of lipids and proteins |
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what are the most abundant lipid in the plasma membrane? |
phospholipids |
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phospholipids are are amphipathic molecules containing what |
hyrdophilic and hydrophobic regions |
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what does the fluid mosaic model state? |
a membrane is a fluid structure with a mosaic of various proteins embedded in it |
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What happens as temperatures fluxuate |
lipids expand as temperate increases. lipids condense when temperatures decrease. |
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what are the six major functions of membrane proteins? |
transportation, enzymatic activities, signal transduction, cell to cell recognition, intercellular joining, attatchment to cytoskeleton and ECM |
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what is diffusion? |
moving from high concentration t low concentration |
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what is passive transport? |
Diffusion of a substance across a membrane with no energy investment |
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how do substances diffuse |
down their concentration gradients the region along which the density of a chemical substance increases or decreases |
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why is diffusion of a substance passive transport? |
no energy is require by the cell |
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what is osmosis |
diffusion of water across a selectively permerable membrane |
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how does solute concentration become equal on both sides of the cell? |
water diffuses across a membrane from the region of lower solute concentration to the region of higher solute concentration |
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what is tonicity? |
the ability of a surrounding solution to cause a cell to gain or lose water |
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what is an isotonic solution? |
solute concentration is the same as that inside the cell; no net water movement across the plasma membrane |
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what is a hypertonic solution? |
solute concentration is greater than that inside the cell; cell loses water |
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what is a hypotonic solution? |
solute concentration is less than that inside the cell; the cell gains water |
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what can create osmotic problems for organisms? |
hypertonic or hypotonic enviornments create problems in the control of solutes |
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what happens in facilitated diffusion? |
transport protiens speed the passive movement of molecules across the plasma membrane. |
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what do channel proteins provide and include? |
they provide corridors that allow a specific molecule or ion to cross the membrane. they include aquaporins for facilitated diffusion of water and ion channels to open and close in response to stimuli |
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what uses energy to move solutes against their gradient |
active transport |
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why is facilitated diffusion still passive |
because the solute moves down the concentration gradient requiring no energy |
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what is active transport? |
moves substances against their concentration gradients |
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what does active transport require? |
energy, usually in the form of ATP
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what is active transport performed by? |
specific protiens embedded in the membranes |
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what does active transport allow cells to do? |
maintain concentration gradients that differ from their surroundings. |
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what is one type of active transport system |
the sodium potassium pump |
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what is cotransport? |
coupled transport by a membrane protien |
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when does cotransport occur |
when active transport of a solute indirectly gives transport of other solutes |
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what is an example of cotransport? |
plants commonly use the gradient of hydrogen ions generated by protein pumps to drive active transport of nutrients into the cell |
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how does bulk transport across the plasma membrane occur? |
endocytosis and exocytosis |
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how do small molecules and water enter or leave the cell |
lipid bilayer or via transport protiens |
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how do larger molecules such as polysaccharides and proteins cross the membrane in bulk |
via vesicals |
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does bulk transport require energy? |
yes |
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what does the sodium potassium pump do? |
uses atp, changes protiens through binding, pumps against concentration gradient |
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what is a gradient? |
ratio concentration of a component |
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what changes the shapes of proteins? |
positive and negative charges |
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what charge does sodium have |
positive |
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what charge do phosphate have |
extremely negative |
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what are the three divisions of endocytosis? |
phagocytosis, pinocytosis, receptor-mediated cytosis |
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what does phagocytosis do? |
takes in large food molecules |
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what does pinocytosis do? |
takes in extracellular fluid |
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what does receptor mediated endocytosis do? |
binds to receptors |
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what fuses with food molecules to digest |
lysosomes |
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what does exocytosis do? |
gets rid of waste and transports something made inside the cell |
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what is a target molecule/ligant? |
any molecule that binds specifically to a receptor site of another molecule |
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what isthe intermembrane system |
all the organelles in the cell that have a phospolipid bilayer |
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what does cholesterol do? |
helps keep fluidity |
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what do protiens change shape? |
ions interact with proteins polar portions, because amino acids are polar |
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proteins changing shape is known as what |
electrostatic interaction |
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atp becomes what |
adp + phosphate (which is extremely negative) |
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with more salt, what is needed |
more water |
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in a single cell eukaryotic organism, what would be the major problem for a fresh water peramesiam |
too much water, a vacuole would be necessary to push out water |
