Physiology Ex 1 - Ion Gradients and Transport Flashcards
How long do each of the 1 billion ATP molecules in the cell last?
less than one minute and 70% is used to pump Na+/K+
What is ADP to ATP conversion used for?
Glycolysis
Oxidative metabolism
What is ATP to ADP conversion used for?
Membrane transport
Anabolism
Catabolism
Mechanical work
Etc
What is required for the efficient production of ATP by cells?
A hydrogen ion gradient across the mitochondrial inner membrane
ATP synthase uses the energy of hydrogen ions diffusing down the gradient to produce?
ATP
Electron Transport Chain proteins use energy derived from metabolism to?
Pump hydrogen ions across the inner mitochondrial membrane
What does the metabolic poison 2,4-Dinitrophenol (DNP) do?
Uncouples oxidative phosphorylation (inhibits ATP production) by acting as a proton ionophore carrying protons across the mitochondrial membrane and decreasing the proton gradient.
Why was DNP discontinued from use as a diet pill in the 1930’s?
Because of the risk of fatal hyperthermia and development of cataracts
What does the metabolic poison Sodium Azide do?
Inhibits cytochrome oxidase by binding irreversibly to the heme cofactor (similar to cyanide poisoning). It affects organs that undergo high rates of repiration, such as the heart and brain. It inhibits growth of bacteria and fungi and is an airbag explosive.
What types of transport down a concetration gradient do not require added energy?
Simple diffusion
Facilitated diffusion (vmax)
What types of transport down a concetration gradient require added energy?
- Active transport - Na/K ATPase, Ca ATPase, P-glycoprotein
- Secondary active transport
- Endocytosis and Exocitosis
Which types of molecules can diffuse across the membrane without a carrier?
Small lipid soluble molecules
Which molecules require a carrier or channel to diffuse across the membrane?
Hydrophilic molecules
Which are the membrane proteins that enable or facilitate passage of molecules across the membrane?
Channel proteins
Carrier proteins (passive, active)
How does Vmad limit the rate of transport (or diffusion)
Facilitated diffusion is driven by the concentration gradient across the membrane but limited by the number and function of the transporters
Does transporter-mediated diffusion require energy(net diffusion down a concentration gradient)?
No, however the rate of diffusion is NOT exclusively concentration-dependent unlike simple diffusion - the max rate of transport (Vmax) is related to the number of carrier molecules in the membrane and the speed with which the transporter protein can transport the molecule.
What is the main use of facilitated diffusion?
To transport glucose and most amino acids into cells
What is the specificity of the channel (channel proteins) determined by?
The size of the passageway and the charge of properties of the amino acids that make up the passageway
What causes the net movement through a channel (channel proteins)?
An electrochemical gradient
What are aquaporins?
Water channels
Name some ion channels
K+
Na+
Ca++
Cl-
monovalent
divalent
etc
Who discovered aquaporins?
Peter Agre (2003)
Which channels are always open?
Pores
Leak channels
Which channels are gated?
Gated channel
What are the types of gated channels?
- Ligand-gated channel (triggered by binding of specific molecules to the channel)
- Phosphorylation-gated channels (function altered by phosphorylation/dephosphorylation)
- Voltage-gated channels (triggered by change in membrane potential)
- Mechanically-gated channels (triggered by mechanical stress to membrane)
What type of gated channel are Nicotinic Cholinergic receptors?
Ligand-gated ion channels. 2 acetylcoline binding sites-binding of Ach opens the channel and allows Na+ ions to cross the membrane
What are carrier proteins?
Membrane proteins that transport molecules in one or both directions
Some molecules are transported by both carriers and channels. T/F?
True
Oxygen enters cells by
Simple diffusion
Sodium ions enter cells by
Primary active transport
