Trabsport In And Out Of Cells Flashcards
Improvements for osmosis experiment
Use intermediate conc of sucrose solution to obtain more accurate value that gives no change in mass
Carry our repeats to allow mean to be calculated
Use same cork borer to get same diameter
Blot directly to remove excess liquid
Use same type of sample as water potential may differ
Risks in osmosis experiment
Cork borer - cut away from you or downwards onto tile
Broken glass- keep test tubes away from edge of desk
Why is % change calculated
To allow comparison despite diff starting masses
Why is sample kept in solution for 24 hours
The mass will of sample become constant
Why each test tube covered with bung
To prevent evaporation of water from sucrose solution
Will result in decreasing water potential
How to find equilibrium of osmosis
Graphs % change on y axis against sucrose conc x axis
Find sucrose conc where there is 0 mass chbange
Find out water potential
Why’s plasma membrane important
Forms a boundary between cytoplasm and environment
Controls movement of substances in and out of cell
Allows different conditions to be established
Structure of plasma membrane
Glycolipid =embedded in
Cholesterol = completely in
Integral protein
Extrinsic protein
Carbohydrate above
Phospholipids
Hydrophilic head with phossphoester bond
Glycerol
Hydrophobic fail with fatty acid and ester bond
Why do phospholipids form a bilayer
polar phosphate group is hydrophilic and will face tissue fluid and cytoplasm
• fatty acid tails non-polar and hydrophobic and will face towards centre of membrane and away from tissue fluid and cytoplasm
• As both tissue fluid and cytoplasm is aqueous
• Phospholipids must form two layers with the hydrophobic tails facing inward and hydrophilic phosphate groups outwards interacting with the aqueous environment
What can pass through bilateral
Small
Non polar
Lipids soluble
Function of proteins in membrane
To allow certain substances to move in and out of the structure
Provides structural support
Provides channels for passive transport
Allow AT
Form recognition sites
Act as hormone binding site
Intrinsic protein
Completely span bilayer
Act as carries to transport water soluble
Can act as enzymes
Extrinsic proteins
Bound to surface partially embedded
Give mechanical support
Work with glycolipids as cell receptors
Cholesterol function
Restrict movement of other molecules
Adds strength
Fluid mosaic
Fluid : moving and not fixed
Mosaic : proteins embedded and vary
Define diffusion
Passive net movement of particles from area of high conc to area or low conc down a conc gradient
Factors affecting rate of diffusion
SA : larger sA = faster
Conc gradient : bigger the diff the faster
Thickness of exchange surface : thinner
Temp
Size of molecule
Nature of molecules : fat soluble faster
Facilitated diffusion
Involves proteins that recognize a specific molecule and help it move across membrane passively
Uses channel (allow one type) and carrier (rotate) proteins
Define osmosis
Passive net movement of water molecules for high WP to low WP across partially permeable membrane
Define water potential
Pressure created by water molecules
Always moves towards more negative wp
KPa
Hypertonic
Higher solute conc inside than outside
Hypotonic
Less solute conc inside than outside
Osmosis in RBC
Shrivels if higher WP inside
Bursts if lower WP inside
Osmosis in plant cells
Plasmolyzed = hypertonic
Isotonic = flaccid
Turgid = hypotonic
Define active transport
Movement of molecules from area of low concentration to area of height conc against conc gradient using energy from ATP and using carrier proteins
How does AT use ATP
Used directly by carrier proteins
By using conc gradient that’s already been set up
Process of AT
Molecule or ion attaches to receptor on carrier protein
ATP binds to carrier protein
ATP undergoes hydrolysis forming ADP and phosphate
The phosphate attaches to carrier protein causing it to change shape
Shape change causes carrier protein to transport molecule to other side of membrane where it’s released
Phosphate now leave carrier protein
ADP and phosphate will later form ATP during respiration
