Topic 2 Flashcards
Proteins, enzymes & membranes
How can proteins be separated?
- Charge: electrophoresis / ion exchange chromatography
- Size: gel filtration
- Solubility: pI precipitation (ppt) / ammonium sulfate ppt
What is the reaction of the enzyme oxidoreductase?
- Catalyse redox reactions
- Transfer of H, O or ē
What is the reaction of the enzyme transferase?
Transfer functional group from 1 molec. to another
What is the reaction of the enzyme hydrolase?
Hydrolyse (break bonds)
What is the reaction of the enzyme lyase?
- Remove/add groups to molec.
- Break bonds, ē arrangem.
What & how do proteins denature?
Loss of structure & function = denaturation
- Organic solvent: disrupt pH bonding
- Detergent: disrupt hydrophobic bonds
- pH extremes: disrupt ionic electrostatic bond
- Heat: increase in KE & disrupt all non-coval. bonds
What is the reaction of the enzyme ligase?
Join molecules
What are the enzyme properties?
- Shape: eg globular vs fibrous
- Disruption of electric charge
- Structure: Stability
- Function: catalysis
What are the 2 models for substrate-enzyme interaction?
Lock & key:
- Only correct shape substrate fits into active site of enzyme
- Key = substrate
- Lock = enzyme
Induced fit model:
- Active site of enzyme changes shape or substrate binds
- Conformational change (improved activity)
How do enzymes function?
E+S = ES = E+P
What are the different types of lipids in the membrane?
- Phospholipids
- Glycolipids
- Sterols
What is the phospholipids in the membrane?
- Backbone & 2 fatty acids (tails)
- -ve charged phosphate w/ charged / polar head groups
eg phosphoglycerides
What is roles of cell membrane?
- Define boundaries of cell
- Serve as sites for biochemical functions ē transport in mitoc. /protein processing
- Provide transport proteins (move molecules in & out)
- Contain receptors for signalling
- Provide mechanisms for cell-to-cell contact, adhesion + communication
What are the major components of the cell membrane?
Fluid mosaic model - structure of plasma membrane, mosaic of components
- phospholipids
- proteins
- membrane proteins
- fatty acids
- carbohydrates
What are the different types of lipids in the membrane?
- Phospholipids
- Glycolipids
- Sterols
What are the glycolipids in the membrane?
- Lipid & carbohydrate chain
eg glycoglycerolipids
What are the sterols in the membrane?
eg cholesterol
What are the proteins in the membrane?
- Integral
- Peripheral
- Lipid-anchored
What is integral proteins in the membrane?
- Hydrophobic regions embedded w/in membrane interior
- V. strong lipids interactions
- Hard to remove & require detergents to disrupt hydrophobic bond in lipid bilayer
What is peripheral proteins in the membrane?
- Extrinsic: lack of hydrophobic sequences
- Loosely attached: separated from membrane by mild treatment & usually soluble in water
What is lipid-anchored proteins in the membrane?
Covalently bound to lipids in bilayer
What is different forms of transport across cell membrane?
Passive: no energy - Simple diffusion - Facilitated diffusion Active: requires energy - Transport
What is active transport in membrane?
Needs energy low => high concentration
- Uniport: Only 1 way transport eg glucose in erythrocytes
- Aniport: 1 in, 1 out transport eg Na+ - K+ pump
- Symport: Both 1 way transport eg sodium glucose
What is simple diffusion in membrane?
- No energy needed
- Flow of molecules from low => high
- Hyper, hypo, isotonic
