Biochemistry Flashcards
Oxidoreductases
Action?
Example?
Action: Oxidation reduction reactions
Examples: oxidase, dehydrogenase
Transferase
Action?
Example?
Action: Transfers amino, carboxyl, acyl, carbonyl, methyl, phosphate and other groups between molecules
Example: transaminase
Hydrolase’s
Action?
Example
Action: cleavage of bonds coupled with inserting water
Example: Esterase, amylase
Lyases
Action?
Example?
Action: Cleavage of carbon-carbon, carbon-sulfur, and carbon-nitrogen bonds
Example: Decarboxylase
Isomerase
Action?
Example?
Action: Rearrangement of bonds
Example: epimerise
Ligases
Action?
Example?
Action: formation of bonds between C,O,S,N
Irreversible inhibitor action
Bind to enzymes permanently, the cell must produce new proteins to resume function
Reversible enzyme inhibitor action
Can bind and release enzymes, non-covalent bonds.
Includes competitive and non -competitive enzymes.
Competitive inhibitors
Compete with substrate to bind to the active site
Non-competitive inhibitor
Bind at different site from the substrate, changes the shape of the active site
Feedback loops in enzymes
the product of the metabolic pathway often inhibits an enzyme early in the same pathway, preventing waste
Allosteric regulation of enzymes
Allosteric enzymes control key points in metabolism, allosteric inhibitors bind to a regulatory site, altering the enzymes shape
Post-translational modification
enzymes can be chemically modified after synthesis to alter activity, E.G. phosphorylation
Membrane protein roles:
5
- transporters
- channels
- anchors
- receptors
- enzymes
Percentage of membrane weight that is membrane proteins?
20-75%
Membrane protein structure
- most form alpha helices, crossing the membrane
- Membrane inserted part is hydrophobic
membrane permeability
2
- Molecules diffuse from high conc. to low conc.
- Not all molecules can diffuse across the membrane
Transporter protein
3
- switches between two states, open on one side (binding), and open on the other side (releasing)
- also called a pump
- relatively slow, 10^2 - 10^4 molecules
Protein channels (3)
- Only allow active transport
- Can be ligand-gated or voltage-gated
- Much faster than transporter
Protein receptors and ligand examples (2)
- Proteins that bind to signalling molecules (ligands), producing a cellular response
- Ligands include; hormones, cytokines and neurotransmitters
G-protein coupled receptors examples (5)
- Adrenaline receptors
- Glucagon receptors
- Odour molecule receptors
- Acetylcholine receptors
- photoreceptor
G-protein coupled receptor action
- Ligand binding causes activation of the associated G protein, which binds on.
- Activated G-protein stimulates enzymes that produce a secondary messenger, amplifying the signal
cAMP action
cAMP stimulates protein kinases, that phosphorylate various cellular proteins, causing changes in gene expression
Enzyme-coupled receptors (3)
- Ligand binding
- RTK
- Examples
- Ligand binding causes dimerisation and activation of intracellular enzyme
- E.G. RTK phosphorylates proteins on the tyrosine
- Includes receptors for insulin, GH
- Cancer related