Biochem Flashcards
Why are the nucleolus and mitochondria so prominent in metabolically active cells?
Nucleolus- site of ribosome manufacture
Mitochondria- have own DNA and prot- site of respiration
What are the 3 proteins making up the cytoskeleton?
Micro filaments, intermediate and microtubules
What are the 3 types of cell junctions and their purpose?
Desmosomes- micro filament belts, protect vs shearing forces, anchorage
Tight junctions- form seals, make cells impermeable, limit protein movement in cm and leakage of substances between cells
Gap junctions- large prot channels, communication betw cells
What is interstitial fluid?
Fluid surrounding cells
What are the 4 types of ion channels
Ungated (leak)
Voltage-gated
Mechano-gated
Ligand-gated
What is the difference between primary active transport and secondary active transport?
Primary- carrier prot hydrolysed ATP and uses some of the e for transport
Secondary- used potential e stored by conc diff of ion (one ion trans up grad, the other down)
What are the two types of exocytosis?
Constitutive
Regulated
What are the 4 types of Endocytosis?
Pinocytosis
Receptor-mediated endocytosis
Transcytosis
Phagocytosis
What is the difference between autocrine and paracrine cells?
Autocrine- messenger acts on secretory cell itself
Paracrine- adjacent cells affected
What is a ligand?
A chem messenger than binds to prot mols in membrane, cystol or nucleus
What is the association constant?
When rates of association and dissociation are at equilibrium
What is down regulation?
Memb receptor number decrease in response to increased ligand conc
Removed from cm via receptor-mediated endocytosis
Therefore cells less sensitive to ligand when ligand levels high
What does adding a high energy phosphate group to a receptor and why does it happen?
Kinases phosphorylate protein and phosphorylase enzymes reverse process
Either desensitises or sensitises receptor (ie either decreases or increases affinity for ligand)
What is the action of tyrosine kinase?
It is activated on the cytoplasmic side of the membrane if a certain receptor is activated- then activated enzyme to phosphorylate tripsine to give yield to ATP and protein
What happens when an agonist bonds to a GPCR?
Activates g-protein- affinity for GTP increases (normally binds to GDP)- dissociates from receptor inside the cell-> can associate with other membrane-bound signal transduction molecules
GTP-ase activity inactivated and so re-associates with membrane receptor
