Cell Membranes and Transport Flashcards
Key word to describe cell surface membrane + why it’s called that
‘Fluid mosaic’
Fluid - phospholipid molecules can move relative to one another
Mosaic - embedded proteins vary in size and shape, scattered randomly throughout membrane
Fluid mosaic model labels
- hydrophilic phosphate head
- hydrophobic fatty acid tails
- phospholipid
- phospholipid bilayer
- intrinsic protein
- extrinsic protein
- cholesterol
- glycoproteins
- channel protein
- carrier protein
Function of cell membrane
Take up nutrients and other requirements, secrets chemicals, cell-cell recognition
Factors affecting permeability of plasma membrane
- membrane acts as a barrier = semi-permeable
- non-polar molecules/small uncharged molecules pass through by diffusion
- polar molecules/large charged molecules pass through by facilitated diffusion
Diffusion definition
Movement of molecules/ions from high to low concentration (down a concentration gradient)
Factors that affect diffusion
- concentration gradient
- thickness of membrane/diffusion distance
- surface area
- temperature
- lipid solubility
- size of molecule
Facilitated diffusion definition
Diffusion (high to low concentration) where charged atoms/molecules (ions) and large molecules move through membrane through intrinsic proteins
Ions travel through…
Channel proteins
Glucose/amino acids travel through…
Carrier proteins
Osmosis definition
Diffusion of water molecules from high to low water potential through a semi permeable membrane
Water potential definition
‘Tendency of water molecules to leave a system’
Water potential measured in
kPa
Pure water has highest water potential which is
0kPa
Water potential equation
Water potential (0 or -) = solute potential (-) + pressure potential (+)
Isotonic
No net movement
Hypertonic
High water potential in cell
Hypotonic
Low water potential in cell
Turgid
No more water can enter cell
Plasmolysed
Cell loses water, cell membrane pulls away from cell wall
Incipient plasmolysis
50% turgid
50% plasmolysed
Cytosis for
Bulk transport
2 types of endocytosis
Pinocytosis
Phagocytosis
Pinocytosis definition and what happens?
Bulk transport of fluids
Fluid reaches cell membrane, invagination, vesicles pinches off and brings contents into cell
Phagocytosis definition and what happens?
Bulk transport of solid particles
Solid particle reaches cell membrane, engulfed, vesicles pinches off and brings contents into cell
Exocytosis definition and what happens?
Bulk transport our of cell (secretion)
Vesicle from Golgi body migrates to cell membrane
Vesicle fuses with cell membrane, contents released
Active transport definition
Movement of ions/molecules from low to high concentration (against concentration gradient) which requires energy from ATP (made by mitochondria from aerobic respiration)
Cyanide effect on active transport
Inhibits aerobic respiration, no ATP produced, no active transport as no energy from ATP
Graph for diffusion
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Graph for facilitated diffusion
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Graph for active transport
(Addition of cyanide causes drop)
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