Lecture 15: Membranes, cell signaling, and fuel metabolism regulation

plasma membrane

selective barrier

organelle membranes

compartmentalization of biochemical reactions

integral membrane proteins

transverse lipid bilayer

peripheral membrane proteins

have specific interactions through electrostatic or amphipathic domain

how are peripheral membrane proteins anchored?

through covalently attached lipid molecule

what type of FA does cholesterol have the strongest interactions with?

saturated FA

hopenoids

bacteria equivalent of cholesterol (bacteria lack cholesterol)

phospholipase

hydrolyzes phospholipids into FAs

glycerophospholipid

glycerol backbone with FA + phosphate

PS (phosphatidylserine)

kept inside cell - is signal for cell damage

how does glucose cross the cell membrane?

facilitated diffusion (passive)

P-type ATPases

primary active transport; transport ions

V-type ATPases

primary active transport; transport H+

ABC transporters

primary active transport; transport toxic metals, drugs, and lipids

primary active transport

hydrolyze ATP to move against gradient

secondary active transport

against gradient, driven by ion moving down gradient

SGLT1

secondary active transport of glucose in intestinal epithelial cells

cell-to-cell contact signaling example

MHCII - T-cell receptor

protein kinases

use ATP to transfer PO4 group

tyrosine kinase receptor signal transducer

SH2 domain

JAK-STAT receptor signal transducer

STAT

serine-threonine kinase receptor signal transducer

SMAD

what inactivates an activated protein kinase?

protein phosphatase

Ras

tyrosine kinase receptor

activate GTPase when bound to GTP

GEF

turns Ras on

GAP (GTPase activating protein)

turns Ras off

tyrosine kinase receptor pathway

GEF →

IRS (insulin response substrate)

activates PI3 kinase

PI3 kinase

phosphorylates PIP2 → PIP3

PIP3

binds PH domains to signal

cAMP production pathway

ATP → cAMP → 5’-AMP

what do rising AMP levels signal?

low cellular energy

adenylyl cyclase

ATP → cAMP

cAMP phosphodiesterase

cAMP → 5’-AMP

IP3

triggers calcium release for signaling

DAG

paired second messenger with IP3

phospholipase C

hydrolyzes PIP2 → IP3 + DAG

GCPR

activates phospholipase C