2.Crossing the plasma membrane Flashcards
what elements are in lipids
CHO
Lipids vs Carbohydrates
-Lipids contain a lot less oxygens compared to carbohydrates (lipids have long chains made up of C and H entirely)
-Lipids are non polar and insoluble in water whereas carbohydrates are polar and soluble in water
List 3 characteristics of lipids
-exist as fats, oils and waxes
-poor conductors of heats
-good insulators
Examples of triglycerides
Fats
Oils
Subunits of triglycerides
Glycerol and 3 fatty acids
what bonds exist within triglycerides
ester bond between glycerol and fatty acids
What is glycerol
-Glycerol forms the base of triglycerides
-Contain 3 hydroxyl groups (OH)
-Fatty acids attach to the hydroxyl (OH) groups of glycerol
What are fatty acids
-Fatty acids are very long molecules
-They can be hundreds of carbons long (usually 10-100)
-They attach to glycerol via there carboxyl group (COOH)
Saturated vs Unsaturated fats
Saturated fats contain NO double bonds between carbon atoms (hence saturated with hydrogen) whereas unsaturated fats have at least one Carbon carbon double bond.
(mono=one C,C double bond, poly=many C,C double bonds)
List any 4 functions of triglycerides
-Energy source
-Protection of vital organs
-To prevent evaporation in plants
-To insulate the body
-Forms myelin sheath around the axons of neurones
-metabolic water source (as a result of respiration)
what elements are in phospholipids
CHO P
structural components of phospholipids
glycerol, 2 fatty acids and a phosphate head
Cholesterol function
provides stability and flexibility to the plasma membrane
What are steroids
-steroids are lipid based hormones
-steroids are signalling molecules that cause a response within the body
-lipid based hormones (steroids) are lipid soluble, hence can simply cross the phospholipid bilayer and have an intracellular receptor
components of plasma membrane
-two sets of phospholipids (label individual components)
-protein channel
-glycolipid
-protein pump
-cholesterol
-glycoprotein
-
How are phospholipids arranged in the plasma membrane
-polar hydrophilic (water loving) phosphate head faces aqueous solutions
-two non polar/hydrophobic fatty acid tails point towards the centre of the phospholipid bilayer
glycoprotein
carbohydrate chain (hexagonal shape) attached to protein
glycolipid
carbohydrate chain (hexagonal shape) attached to PHOSPHOlipid
Diffusion
the net movement of particles from area of high to low concentration down a concentration gradient.
(passive)
Factors that effect the rate of diffusion
general factors:
-temperature-particles with greater kinetic energy diffuse faster
-particle size-particles with lower mass move with greater kinetic energy (at the same temperature) and can move through smaller pores in the membrane
Specific to movement across the membrane:
-Concentration gradient-greater the difference in concentration on either side of the membrane, diffusion will occur faster
-Diffusion distance-if the semi permeable membrane is thinner, diffusion will occur faster
-surface area- larger surface area means more particles can move across the membrane simultaneously
Fluid mosaic theory
-membranes are made up of small components-mosaic
-components are free to move independently of each other-fluid
what substances can cross directly through the phospholipid bilayer
-Small gases:02,CO2
-Small non polar molecules:urea, ethanol
-Lipid soluble molecules:steroids, vitamin D
-Water
How can you measure diffusion
using a colorimeter, the more pigment that diffuses out into surrounding fluid, the less light that will get through the liquid (more is absorbed) and hence more diffusion.
osmosis
Osmosis- the net movement of water molecules from an area of high water/solvent concentration through a partially permeable membrane to an area of low water/solvent concentration.
solution
solvent + solute
solvent
water- universal solvent
Hypotonic solution
-solution lower in solute and higher in water molecules than the solution being compared to
Hypertonic solution
-solution higher in solute and lower in water molecules than the solution being compared to
isotonic solution
-two solutions of equal solute concentration
(no net movement of water)
animal cell in hypotonic solution
cell lyses/becomes lysed
animal cell in hypertonic solution
cell crenates/ becomes crenated
plant cell in hypotonic solution
cell is turgid
plant cell in isotonic solution
cell is flaccid
plant cell in hypertonic solution
cell is plasmolyzed
Facilitated diffusion
The net movement of particles from high to low concentration down a concentration gradient using a protein channel
Active transport
The movement of DISSOLVED substances ACROSS a membrane from low to high concentration using ATP and a protein pump
Exocytosis
+eg
Bulk movement of large molecules OUT of the cell. Vesicles fuse with the cell membrane and expel their contents out of the cell.
eg release of hormones in glands of the endocrine system
Endocytosis
Bulk movement of large molecules into the cell. Substances hit the cell membrane triggering the formation of vesicles inside the cell
Pinocytosis
+eg
Bulk movement of liquids into the cell
eg how paramecium feeds
Phagocytosis
+eg
Bulk movement of solids into the cell
eg. WBC engulfs a pathogen
Phagocytosis steps
- Phagocyte engulfs pathogen
-vesicle formed around pathogen (phagosome) - Pathogen destroyed
-lysosome and phagosome fuse together (phagolysosome)
-digestive enzymes break down pathogen - Exocytosis occurs
-Phagolysosome fuses with membrane, removing unwanted cellular material
two types of endocytosis
pinocytosis
phagocytosis
