Biological membranes Flashcards
2.1.5
What are the function of mebranes with cells?
- Site of chemical reactions - provides attachment sites for enzymes and pigments
- Compartmentalisation - isolation of chemical reactions eg lysosome mebranes isolate hydrolytic enzymes
- Provide internal transport system
- Controls the movement of sunbstances into/out organelles
What is the function of cell surface membranes ?
- Selectively permeable barrier
- Cell signalling
- Cell recognition
- cell to cell adhesion to form tissues
- Enzyme attachment
What is the function of cholesterol?
Steriod
* Connect phospholipids
* Reduces movement of phospholipids giving the membrane stability and flexibilty
What is the function of glycocalyx ( glycoprotein + glycolipids)?
glycolipds - carbohydrate attached to phospholipds
glycoproteins - carbohydrate attached to proteins
* Receptor sites - hormones
* cell marker
* Acts as anitgen
* helps cells adhere to one another
* forms hydrogen bonds
What is the function of proteins?
- structural support
- transport
- helps cell adhere together
- receptors for hormones
What is the function of phospholipds?
- Gives membrane fluidity
- barrier to larger water solube molecules
- lipid soluble
What 3 factors affect membrane permeability?
- Temperature: High temperature cause more kinetic energy so the membrane protein denature and the phospholipis move further affect - more permeable
- Ph - changes tertiary structure of membrane proteins
- organic solvent- dissolves the membrane so more permeable
What is diffusion?
Diffusion is the net movement of molecules or ions from a region of their higher concentration to a region of their lower concentration
Name 6 factors that affect diffusion
- Temperature : higher temperatures means more kinetic energy so diffusion happens faster
- Surface area : the greater th surface area thre more molecules that can cross the mebrane at anytime
- Concentration gradient : The bigger difference between thte two sides of the membrane the quicker the rate of diffusion
- Distance : The shorter the distance , the faster the rate of diffusion
- Stirring/ moving : More kinetic energy increase the rate of diffusion
- Type of molecule : larger molecule need more energy to move so they tend to diffuse more slowly and non polar molecules can move through the phospholipds bilayer quickly
What is simple diffusion?
**Net movement of small, lipid solube ** molecules directly through thr bilayer from an area of high concentration to an area of lower concentration down a concentration gradient
Passive process reqiores no energy from ATP
Examples : steriods, fat solube vitamins
What is facilated diffusion?
- Passive movent of molecules orions through a channel protein from a higher to lower concentration
How do channel proteins work?
- ions are charged and have hydrophilic lining
- can sometimes be gated
- specfic for certain ions
- Special channel proteins called aquaporins allow water to diffuse across the membrane
How do carrier proteins work?
- Specific large pola molecules
- glucose and amino acids
- when the specific molecule binds to the protein , it changes shape and allows molecule across the membrane
What is osmosis?
The net movement of water from a region of higher water potential to a region of lower water potential down a water potential gradient across a partially permeable membrane
What is water potential?
- The tendency of water molecules to leave a solution
- pressure created by water molecules in kPa
- the water potential of pure water = 0
- more solute = more negative
