Week 6: Membrane Transport Flashcards
Delta G Equation
Delta G+RTln(C^cD^d/A^a*B^b)
Delta G*’ Equation
-RTlnK
Rxn graph drawbacks and what it is
Single-molecule consideration
Not good for looking at entire mixtures
Quadratic graph
What does delta G = 0 mean
At equilibrium (minimum of the curve)
(Upside down quadratic)
What does Delta G* mean for difusion
Is not equal to 0
What is the normal ratio for delta G equation
Inside/outside
Why is the ratio inside/outside
You are calculating delta G of flow into cell
If they were switched would be calculating flow out of cell
Movement of molecules down a concentration gradient is what?
Spontaneous
Delta Gt equation
RTln(in/out) + ZFdeltaPsi
Z = the charge on the particle (either - or +)
Delta Psi is calculated by Psi(in)-Psi(out)
Where are cells more negative
On the inside
Secondary Transport
2 different proteins/pumps
One uses ATP
Other uses the concentration gradient created by the first
Sodium Potassium Pump
Use the energy of ATP hydrolysis to pump 3Na+ out of cell and 2+ K into the cell against their concentration gradient
What does all of the work of the Na+-K+ pump
The alpha subunit
4 domains in the alpha subunit
Signaling Proteins Steps
1.) Release of a Primary Messenger
2.) Reception of the primary messenger
3.) Generation of an intracellular 2nd messenger
4.) Activation of effector results in a physiological response
5.) Termination of signal cascade
1.) Release of Primary Messenger
2.) Reception
Ghrelin(hunger, stomach)
Glucagon (Glucose breakdown liver)
Receptor Protein in cell, reversible
3.) Generation of an intracellular 2nd Messenger
Receptors change protein structure
Generates a 2nd messenger in the cell (Ca2+, cAMP)
4.) Activation of effector results in a physiological response
5.) Termination of signal cascade
2nd messenger is going to cause a chemical change that will cause an enzyme to start or stop some metabolic process
Primary Messengers
Hormones
Photons
Neurotransmitters
How many classes of Receptors
3 Major Classes
3 Classes of Receptors
7-Transmembrane-Helix Receptors: Heterotrimeric G-Proteins
Dimeric membrane receptors: Recruit protein kinases
Dimeric protein receptors: Are protein kinases
Secondary Messengers
cAMP
cGMP
Calcium Ion
IP3
Examples of Dimeric membrane receptors that recruit protein kinases
Human Growth Hormone Receptor
Protein Structure of 7TM
Tertiary Structure Change
Protein Structure of Dimeric
Quaternary Structure Change
Dimeric Protein Receptors that are Protein Kinases
Epidermal Growth Factor
Insulin Receptor
RAS Protein
Key Component of EGF Pathway
Member of family of signal proteins called small G proteins or small GTPases
Monomeric (Not Heterotrimeric like normal G proteins)
Active: Bound to GTP
Inactive: Bound to GDP
Has Intrinsic GTPase Activity (Automatically hydrolyze a P off GTP to GDP)
Insulin Signaling
Insulin hormone is secreted from the pancreas when blood glucose level is high
Biochemical signal for fed state
2 polypeptide chains linked by disulfide bonds
Insulin receptor is a receptor tyrosine kinase
Receptor exists as a dimer even in absence of insulin
Kinase Cascade
Insulin Binding to Conformational change(quarternary) to Cross-Phosphorylation of the kinase to phosphorylation of IRSs
Phosphorylated IRSs are adaptor proteins to convey the insulin signal
Phosphoinositide 3 Kinase binds to IRS and catalyzes PIP2 to PIP3
PIP3 activates PIP3 dependent kinase, which activates AKT
AKT phosphorylates enzymes that control the glucose transporter, increasing glucose uptake by cells, as well as enzymes that convert glucose to glycogen
Signal Termination
Protein phosphatases remove P from activated proteins, ending the signal
Lipid phosphatases remove P from PIP3 to PIP2
Steps for Sodium-Potassium ATPase Mechanism
1.) 3 Na ions bind
2.) Phosphorylation of an Asp residue
3.) Conformation change release 3 Na ions outside of the cell
4.) 2 K Ions binds
5.) Release of the phosphate group
6.) 2 K ions are released inside the cell
Steps for G Protein-Coupled Receptor Pathway
1.) Initiation
2.) Ligand Binds to Receptor
3.) Conformational change of the receptor
4.) Dissociation of Beta and Gamma subunits of the G protein
5.) Exchange of GDP for GTP in the G protein
6.) Adenylate cyclase converts ATP to cAMP
7.) Kinase protein is activated to phosphorylate targets
8.) Termination
Activation of a G protein in response to hormone binding requires the binding of what
GTP. to the Alpha subunit
What binds to G-Proteins
GPCR
GDP
GTP
What doesn’t bind to G-Proteins
cGMP
It is a secondary messenger
Not secondary messenger
Epinephrine
