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BIOLOGY A-LEVEL: Transport Across Cell Membranes - Coggle Diagram
BIOLOGY A-LEVEL:
Transport Across Cell Membranes
COMPONENTS
GENERAL: Fluid Mosaic Model// Fluid because the phospholipid layer can move and is flexible, Mosaic because intrinsic and extrinsic proteins are embeded in the bilayer
GLYCOLIPIDS-
GLYCOPROTEINS-
CHOLESTROL- restricts movement of phospholipid membrane
PROTEINS
carrier proteins- can change shape
channel protein
PHOSPHOLIPIDS- has hydrophilic phosphate head pointing outwards, and hydrophobic fatty acid tails pointing inwards making up a bilayer
MOVEMENT OCCURS BY
SIMPLE DIFFUSION across phospholipid bilayer for lipid soluble/ non-polar molecules
root hair cells, epithelial cells
FASCILITATED DIFFUSION by channel proteins
speed of electrical transmission- neurons- nerve impulses muscle cells- muscle contractions, certain kidney cells- aquaporins to reabsorb water into bloodstream
ACTIVE TRANSPORT by carrier proteins and hydrolysis of ATP to release energy more mitochondria would be present in the ileum cells to absorb as many nutrients as possible by AT example: sodium potassium pump
OSMOSIS
DEFINITION: the net movement of free water molecules down a water potential gradient (from an area of high water potential to an area of low water potential) across a partially permeable membrane without energy as it is passive until dynamic equilibrium is reached
water potential = pressure potential + solute potential
RED BLOOD CELLS 1.
hypotonic
swells and bursts called lysis 2.
isotonic
no change 3.
hypertonic
shrinks called crenation
PLANT CELLS 1.
hypotonic
protoplast swells cell becomes turgid 2.
isotonic
incipient plasmolysis protoplast starts pulling away from cell membrane 3.
hypertonic
protoplast shrinks cell becomes plasmolyzed
hypotonic- where extracellular solution has a higher water potential than inside the cell
hypertonic- where extracellular solution has a lower water potential than inside cell
isotonic- where extracellular solution has same water potetial as inside cell so no overall net movement of water
the more negative the water potential, the lower the water potential (the further it is away from pure water which has a water potential of 0 kPa)
CO-TRANSPORT transport of amino acids/glucose from lumen of ileum to bloodstream
Na+ ions in the epithelial cells of the ileum leave by active transport through sodium potassium pump into the blood stream against the concentration gradient. This makes a low concentration of Na+ ions in the epithelial cells of the ileum. This means a large concentration of Na+ ions are in the lumen of the gut so it goes diffuses down the concentration gradient through a channel protein bringing glucose/amino acids with the ion against the concentration gradient. This is called co-transport.
How does the rate of movement across membranes increase?
as the number of carrier/channel proteins increases, as the surface area increases, as the concentration gradient/water potential increases
PRACTICAL 3
Production of a dilution series of a solute to produce a calibration curve (graph) with which to identify the
water potential of plant tissue
METHOD:
Make simple dilution from 1 mol solution of sucrose into 5 different concentrations into 5 tubes of 5cm^3.
Cut the potato cubes (same mass/same surface area)
Place one in each tube for 20 minutes (so it reaches equilibrium)
Dab each potato cube on a paper towel to remove excess water.
Weight mass of each cube on mass balance.
Calculate percentage change in mass (because it allows for comparison between concentrations)
CONTROLS: volume of sucrose solution, size of cubes, time left in solution, dabbing each potato before weighing
DEPENDENT VARIABLE: change in mass
INDEPENDENT VARIABLE: concentration of sucrose solution
On calibration curve- x-intercept tells us isotonic solution.
PRACTICAL 4: Investigation into the effect of a named variable on the
permeability of cell-surface membranes
METHOD
1. Cut beetroot into equal cubes (same size/surface area) using a scalpel.
Place into tubes of distilled water (same volume).
3.Place into 5 different temperature (0,20,40,60,80) and leave for 20 minutes or different concentrations of ethanol.
Filter each solution into a cuvette, add a filter and measure the transmission of light percentage on the colorimeter.
INDEPENDENT VARIABLE: Temperature/Concentration of solvents (ethanol)
DEPENDENT VARIABLE: permeability- concentration of beetroot pigment
HAZARDS: scalpel- sharp, ethanol- flammable/irritant wear eye protection, hot liquid- dangerous
What is the effect of temperature on membrane permeability?
As temperature increases, permeability increases (higher kinetic energy phospholipids not as tightly joined together+ for both specificity of proteins (changing 3D tertiary structure broken bonds from high pH/temp))
What is the effect of ethanol concentration on permeability?
as concentration of a substance increases the permeability increases (larger con gradient)
CONTROLS: temperature/concentration depends on IV&DV, volume of distilled water, time left in water.