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Foundation (Membrane transport (-Individual lipids undergo fast lateral…
Foundation
Membrane transport
Plasma membrane::
-Cont membrane, no pores
-single unit
-semi permeable, proteoplasm
Nuclear membrane:
-discontinuous, complex membrane , surrounds nuclues
-two unit membrane
-disappears cell division
-material, nucleoplasm and cytoplasm
Membranes:
-lipid based, sheets
-lipids and proteins
-glycosylated
more fluidity: shorter and more unsat fatty acids
-Individual lipids undergo fast lateral diffusion within the leaflet
-lateral:fast, flip flop :slow
flippases: catalyze transverse diffusion
Flippases: use energy of ATP to move lipids against conc grad
-Small, non-polar passively diffuse
-passive diffusion polar molecules: desolvation: high activation barrier
-Transport facilitated by transporters
Cell signalling:
Receptors::membrane-bound soluble protein or protein complex, exerts physiological effect after binding its natural ligand
GPCR: epinepherine
Enzyme-linked: insulin
Ligand-gated ion
channel: Nicotinic acetylcholine
Other: integrin
Nuclear: steroid
Ligands:
Small ions: feric ion
Organic molecule: adrenalin
Polysaccharides: heparin
Peptides: insulin
Protein:Vas endo GF
Secondary messenger
-Cyclic AMP, Calcium
-Intracellular signalling released by cell
G protein has GDP bound to it which iis turned into GTP
-Initiate signal transduction cascade
-Calcium ions: muscle contraction + fertilization
-Cyclic AMP: G proteins activate adenylyl cyclase in plasma membrane
-Protein Kinase: enzyme, modifies other proteins, adds phosphate group
Adrenalin:
-Activation GPCRs leads to activation of few adenylyl cyclase enzymes
-Every adenylyl cyclase enzyme makes 7ral cAMP molecules
-PKA enzymes activated
-Activate glycogen degrading enzymes in liver tissue
Glucose mols relases
Released Ca2+ binds to and activates regulatory protein calmodulin
-activates protein kinases, directly or indirectly effector proteins
Homeostasis
Blood brain barrier
-No proteins
-Most small molecules blocked
-H2O, salts etc: aquaporins:
allow rapid water passage
-
Transporters:
-Simple diffusion
-Facilitated diffusion
-Primary active
transport
-Ionophore
transport
-Ion channel
-secondary active transport
Ion Channels:
- carbonyl oxygens of peptide backbone interact with K+, not Na+
- Ion selectivity
ABC transporter: ATP hydrolysis to drive transport of substrates
P-gp: exports hundreds of chemically unrelated toxins
ATPase::
-Energy of ATP hydrolysis: drive protons through membrane
-pH control F-type ATPase
Energy of proton grad used to synthesize ATP
-ATP hydrolysed on beta subunits F1
-
Gated ion channels respond to:
- Changes in memb potential
- Ligand binding to specific receptor sites