Topic 4.1 Cell Transportation Mechanisms Flashcards
Examples of raw materials for reactions
-Glucose
-ATP
-Oxygen
Examples of toxic waste products
-CO2
-Water
-Lactic acid
-Urea
Examples of things transported out of the cell
-Proteins
-Hormones
-Bacteria
Properties of the cell membrane that affect transport
-Permeability of the membrane
-Size of the solute
-Cholesterol (changes the fluidity, thickness, compressibility and water penetration the lipid bilayer)
How does the size of a chemical affect transport?
The smaller the molecule and the less strongly it associates with water, the more rapidly the molecule diffuses
Facilitated diffusion components
-Larger polar molecules
-Require channel proteins
-Down the concentration gradient
-The rate of diffusion is high
Examples of substances that require facilitated diffusion
-Glucose
-Carbohydrates
-Sodium ions
Examples of substances that require simple diffusion
-Oxygen
-Carbon dioxide
-Lipid soluble molecules
Examples of substances that require endo/exocytosis
-Hormones
-Bacteria
-Proteins
Hypertonic solution
-Water only moves out of the cell
-Shrivelled cells
-High concentration of solute, low concentration of of water
Isotonic solution
-Water is moving in and out of the cell
-Normal cells
-Same solute concentration inside and outside of cells
Hypotonic solution
-Water only moves into the cell
-Cells swell and eventually burst
-Low concentration of solute, high concentration of water
Water potential
Water potential is a measure of the potential of water to move out of a solution
What has the highest water potential
Pure water; because water will always move from pure water into any solution on the other side of a partially permeable membrane
What is the maximum water potential?
0kPa ; all other solution have a lower (negative) water potential
Osmosis definition
Osmosis os the net movement of water molecules from an area of higher water potential to an area of lower water potential through a partially permeable membrane
Water potential equation
Water potential = Turgor pressure (Ψp) + Osmotic potential (Ψs)
What is turgor pressure?
Turgor pressure is the pressure generated as the swelling protoplasm pushes against the cell wall in plants
What is the isotonic point?
The point where the concentration of the bathing solution is the same as the concentration of the cell
Factors affecting the rate of active transport
-Oxygen concentration
-Change in pH
-Glucose concentration
-Temperature
Pinocytosis
Refers to the uptake of extracellular fluids and dissolved solutes (is thought as cellular drinking)
-Links to active transport as it requires energy)
Phagocytosis
The ingestion of bacteria or other materials by phagocytes.
How to show osmosis with starch and iodine
-Add starch solution to a visking tube
-Place visking tube into iodine water
-Solution inside the tube turns from colourless o blush/black as the iodine water has moved into the cell
A channel protein
-Acts like a pore in a membrane
-Transmembrane protein
-Involved in both entry and exit of the cell
The two major sodium channels in mammals
-The voltage-gated sodium channel (VGSC)
-The epithelial sodium channel
Voltage-gated sodium ions
-Opens and closes in response to changes in the membrane
-In various cell types
Epithelial sodium channel
Located primarily in the skin and kidney
Protein carriers
-have a binding sites for specific molecules
-Changes shape as transports molecules from one side to the other
-Proteins that carry 2 in the same direction are symporters
-If 2 moves in opposite directions they’re antiporters (requires ATP)
-GLUT 2 is found in plasma membrane in digestive system
Simple diffusion
-Small molecules
-Non polar
-Doesn’t need to occur across a membrane
-Rate of diffusion is low
Passive transport
The movement of particles down a concentration gradient (high to low), meaning no energy is required. Diffusion, facilitated diffusion and osmosis are all passive.
Define facilitated diffusion
The movement of particles from high to low concentration through a carrier protein or channel protein.
(Used by charged substances because the cell membrane repels them).
How might certain properties of a molecule affect how its transported?
-Solubility: lipid soluble molecules pass through membranes more easily
-Size: smaller molecules diffuse faster
-Charge: charged molecules cannot diffuse by simple diffusion
How do large molecules move across a cell membrane?
Requires vesicles
-Endocytosis
-Exocystosis
Active transport definition
The movement of molecules against a concentration gradient (low to high), meaning energy is required. Also uses carrier proteins.
The role of ATP in active transport
ATP binds to the carrier protein, providing enough energy for the protein to change shape, which carries the molecule in or out of the cell.
What is the effect of increasing the temperature on membrane permeability?
-Permeability of membrane increases with temperature gradually, due to increased kinetic energy of pigment molecules
-Then greater after 50°C as then the proteins in cell membrane start to denature and more pigment molecules escape.
-As temperatures increases, the fluidity increases due to movement of phospholipids/reducing bonding attraction between phospholipids
