ME01 - Cellular Transport & Signaling Flashcards
Lipid- soluble and Water-soluble on membrane transport
Lipid-soluble substances diffuse easily
Water-soluble substances pass through transport proteins
Complete Table (TRANSPORT)
PASSIVE ACTIVE
Conc. gradient
Carrier-mediated
Energy Expenditure
Movement
MotionPASSIVE ACTIVE
Conc. gradient Downhill Uphill
Carrier-mediated Yes or NO YES
(Yes) Fac Diffusion
Energy Expenditure NO YES
Movement Random Uniform
through spaces or With carrier CHON
in comb. of carrier CHON
Motion Normal kinetic motion Requires addtl energy
Complete Table
Gradient Carrier Energy Na Grad Inhibit Na-K
pump
Simple Diffusion
Fac. Diffusion
Osmosis
1˚ Active Transport
2˚ Active Transport
Co-transport
Counter-transportGradient Carrier Energy Na Grad Inhibit Na-K
pump
Simple Diffusion Downhill None No No No effect
Fac. Diffusion Downhill Yes No No No effect
Osmosis Uphill No No No No effect
(Use Aquaporins)
1˚ Active Transport Uphill Yes Yes Yes Inhibited
2˚ Active Transport
Co-transport Uphill Yes Yes Yes Inhibited
(same direction)
Counter-transport Uphill Yes Yes Yes Inhibited
(opposite direction)
Types of Passive Transport
Diffusion
Facilitated Diffusion
Osmosis
[SIMPLE DIFFUSION]
Occurs ________ from an electrochemical gradient
Via membrane opening or _____________________
_______________ with carrier proteins
downhill
intermolecular spaces
No interaction
Factors that determines the rate of diffusion
by the amount of substance
velocity of kinetic motion
number and sizes of openings
Governs the rate of diffusion
Fick’s Law of Diffusion
Predicts the rate of diffusion of molecules across a biological membrane
Fick’s Law of Diffusion
Fick’s Law of Diffusion is
Directly proportional to:
Indirectly proportional to:
Directly proportional to: Difference of concentration, Permeability coefficient, Area
Indirectly proportional to: Thickness
Physiologic implications of Fick’s Law of Diffusion
Diffusion is FAST at higher concentration gradient
Diffusion is INCREASED at higher permeability
Diffusion is INCREASED at higher areas for diffusion
Diffusion is SLOW when diffusing membrane is thicker
Paths for Simple Diffusion
- Interstices of the lipid bilayer (through the pores) - High lipid solubility
- Through watery channels (AQUAPORINS) - discriminatory in terms of size and charge
Important characteristics of Simple Diffusion through PROTEIN CHANNELS
- Selectively permeable
2. Voltage or Ligand gated channels - “all-or-none” action
Molecular conformation of the gate or of its chemical bonds respond to the electrical potential across the cell membrane
Voltage-gated Channels
Examples: Na-K Channel
“Chemically-gated”
Channels are opened by a chemical substance with the protein
Causes conformational/structural change in the channel
Ligand-gated Channel
Example: Acetylcholine Channel
Rate of transport of molecules can never be greater than the rate of conformational change
True
Uniport Occurs Downhill from an electrochemical gradient More rapid than simple diffusion (CARRIER-MEDIATED) Process NOT GOVERNED by Fick's Law of Diffusion
Facilitated Diffusion
Example of Facilitated Diffusion
Transport of Glucose in Skeletal muscle via Glut4 transporters
Net movement of water through a semi-permeable membrane caused by a concentration
Osmosis
A _______ undergoes OSMOSIS from an area of low solute concentration to an area of high solute concentration
SOLVENT (water)
A _________ undergoes DIFFUSION from an area of high solute concentration to an area of low solute concentration
SOLUTE
Homogenous mixture composed of 2 or more substances
Solution
Parts of a Solution
Solute - substance dissolved
Solvent - substance that dissolves the solute
Concentration of all osmotically active particles per L of Solution
Osmolarity
Method to measure Osmolarity
Freezing point of depression
Concentration of all osmotically active particles per KG of SOLVENT
Osmolality
Determines osmotic pressure between solutions
Osmolality
Two solutions have the same osmolarity
Isoosmotic
Solution with higher osmolarity
Hyperosmotic
Solution with the lower osmolarity
Hypoosmotic
Exact amount of pressure required to stop Osmosis
Osmotic Pressure
Pressure which needs to be applied by a solution to prevent the inward flow of water across a semi permeable membrane
Osmotic Pressure
How do you calculate Osmotic Pressure
Van’t Hoff’s law
Physiologic Implications of OSMOTIC PRESSURE
Osmotic pressure is HIGHER with higher osmolality
Osmotic pressure is HIGHER with high temperature
Higher the osmotic pressure, the GREATER the tendency for water to flow into the solution
Measure of the osmotic pressure of two solutions separated by a semipermeable membrane
Tonicity
Factor that can influence the TONICITY of a solution
Solutes that cannot cross the membrane
TONICITY and Osmolarity
Osmolarity NOT = TONICITY
Osmolarity accounts for ALL solutes
Tonicity accounts for only NON-PERMEATING solutes
Types of Tonicity
Isotonic - equal
Hypertonic - higher
Hypotonic - lower than the cytosol
Transport of glucose, amino acids, and other polar molecules through the membrane
Carrier-Mediated Transport
Example of Carrier-Mediated Transport
Facilitated Diffusion
Primary Active Transport
Secondary Active Transport
Characteristics of Carrier-Mediated Transport
Stereospecificity - specialized to transport specific substance
Saturation - transport rate increases as solute conc increases until all carriers are saturated (T max)
Competition - Structurally related solutes compete for transport sites on carrier molecules Ex. Galactose competes with glucose in the small intestins
Types of ACTIVE TRANSPORT
1˚ Active Transport
2˚ Active Transport - Co-transport/Countertransport
Occurs uphill against an electrochemical gradient
Requires direct-input of metabolic energy (active)
Carrier-mediated transport that exhibits stereospecificity, saturation and competition
Primary Active Transport
Examples of 1˚ Active Transport
Na+/K+ ATPase in all cells
Ca2+ ATPase in sarcoplasmic reticulum
H+/K+ ATPase in parietal cells of stomach
H+-ATPase in intercalated cells of the kidney
Transport NA+ from ICF to ECF and K+ from ECF to ICF against electrochemical gradient
Na+/K+ ATPase
Energy provided: ATP
Stoichiometry - 3Na/2K+
Functions of Na+/K+ ATPase
Control of Cell Volume
*Na+/K+ ATPase promotes net loss of ions out of the cell which
initiates osmosis of water rather than into the cells
*Any form of cellular swelling activates Na+/K+ ATPase
*Somehow negates the negative env’t inside the cell
Electrogenic Nature
*Net of 1 POSITIVE CHARGE is moved from the interior to the
exterior of the cell for each cycle of the pump
*Creates an electrical potential across the cell membrane
Basic requirement in nerve and muscle fibers for transmitting nerve and muscle signals
Electrical potential
Transport of two or more solutes is COUPLED
One of the solutes (Na+) is transported “downhill” and provides the energy for the “uphill” transport of other solute
2˚ ACTIVE TRANSPORT
Energy is provided indirectly from the Na+ gradient
Inhibition of Na+/K+ ATPase inhibits the secondary active transport. True or False
TRUE. Because Secondary Active Transport utilizes energy from NaK ATPase Transport
Types of 2˚ Active Transport
Co-Transport
Counter-transport
Differences of Co-transport and Counter transport
Co-transpor Counter transport
“symport” “antiport/exchange transport”
occurs if solutes move the same occurs if solutes move in opposite
directions across cell membrane directions across cell membrane
Use ATP does not use ATP
Na+ glucose transport in intestines Na+-Ca2+ in all cells
Na+/K+/2Cl- in loop of Henle Na+/H+ in proximal tubule
Na+/Cl- in distal convoluted tubule
Multiple, hierarchal steps
Amplification of hormone-receptor binding event
Signaling Pathways
Functions involved in Signaling Pathways
Activation of multiple pathways
Regulation of multiple cellular functions
How to antagonize/oppose Signaling Pathway
By constitutive and regulated feedback mechanisms
Identify Signaling Molecules Peptides and Proteins - Catecholamines - Steroid Hormones - Iodothyronines Eicosanoids - Small molecules -
Peptides and Proteins - INSULIN
Catecholamines - EPINEPHRINE, NOREPINEPHRINE
Steroid Hormones - ALDOSTERONE, ESTROGEN
Iodothyronines
Eicosanoids - PROSTAGLANDINS, LEUKOTRIENES, THROMBOXANES, PROSTACYCLINS
Small molecules - Amino acids, Ions, Gases - NO and CO2
Types of Cellular Communication
Endocrine Signaling Neurocrine Signaling Paracrine Signaling Autocrine Signaling Juxtacrine Signaling
Transport of hormones along blood stream to a distant organ
Endocrine Signaling
Signaling that is also called synaptic transmission
Transport of neurotransmitters from presynaptic cell to a postsynaptic cell
Neurocrine Signaling
Release and Diffusion of local hormones with regulatory action on neighboring cells
Paracrine Signaling
A cell secretes hormones or chemical messengers that bind to the SAME cell.
Autocrine Signaling
Signaling also called as contact-dependent signaling
Transmitted via oligosaccharide, lipid or protein components of a cell membrane
Juxtacrine Signaling
In juxtacrine signaling, this is occurred between adjacent cells linked by ________
Gap junctions
Examples of each.
Endocrine Signaling Neurocrine Signaling Paracrine Signaling Autocrine Signaling Juxtacrine Signaling
Endocrine Signaling: Hormones (thyroid, insulin, glucagon)
Neurocrine Signaling: Neuromuscular junction
Paracrine Signaling: Testosterone in spermatogenesis, Retinoic in retina
Autocrine Signaling: IL-1 on monocytes
Juxtacrine Signaling: In Gap junction
Also called as signal transducers
Receptors
Types of Receptors
Membrane receptor
Nuclear receptor
Type of Plasma Membrane Receptors
Ion-channel linked - transports ions (once stimulated, channel will open for ions only)
G-protein coupled receptor - enzyme linked that produce the signaling
Catalytic receptor - Protein Kinase; Inhibits or activates CHON activity
Types of Nuclear Receptor
Hormone-receptor complex binds to DNA and regulates the transcription of specific genes
Receptor for transcription of genes to alter gene expression
Nuclear Receptor
Flow of Nuclear Receptor Signaling
Early primary response»_space; Gene activation to stimulate other genes»_space; Biological effect
Process by which an extracellular signal activates a membrane receptor
Involves SECONDARY MESSENGERS
Signal Transduction
Function of Signal Transduction
Signal amplification
Alteration of intracellular molecules creating a response
Types of Signal Transduction Pathways
G Proteins
Ion Channels
Protein Kinases
- Calmodulin-dependent protein kinases
- cAMP dependent protein kinases
- aNP-guanylyl cyclasesFamily of Integral transmembrane protein that possess seven transmembrane domains
G Protein-Coupled Signal Transduction Pathways
What are the Heterotrimeric complexes of G-protein Coupled Signal Transduction Pathway
∂, ß and y subunits
Linked with more than 10,000 different receptor
G Protein-Coupled Signal Transduction Pathway
Example of G Protein Coupled Signal Transduction Pathway
Adrenergic Receptors
Chemokine Receptors
TSH Receptors
Active vs Inactive G protein-Coupled Signal Transduction Pathway
ACTIVE INACTIVE
GTP w alpha subunit GDP
Activation via guanine nucleotide Inactivation via GTPase-acc.
exchange factors (GEFs) proteins(GAPS) and RGS proteins
Regulation of G protein signaling
Desentization and endocytic
removal (B-arrestins)
Signals involved in G protein Coupled Signal Transduction Pathway
Adenylyl Cyclase
Phosphodiesterase
Phospholipids
Method by which kinase is modified in Protein Kinases
Phosphorylation
Phosphorylation usually results in a ___________ of the target protein
functional change by:
changing enzyme activity
modifying cellular location
associating with other proteins
3 types of Protein Kinases
Calmodulin-dependent Protein Kinases
cAMP-dependent Protein Kinases
cGMP-dependent Protein Kinases
Ion involved in which binding causes conformational alterations in calmodulin on Calmodulin-dependent Protein Kinases
Calcium
Phosphorylates specific serine and threonine residues in many proteins (myosin light-chains)
Calmodulin-dependent protein kinase
Example for types of Protein Kinases
Calmodulin-dependent – Muscle cells
cAMP dependent –
cGMP dependent – ANP, NO
What facilitates in the conversion of ATP to cAMP in cAMP-dependent Protein Kinases
Adenylyl Cyclase
Increased cAMP activates ____________ in cAMP-dependent Protein Kinases
Protein Kinase A
In the Kidney, ANP inhibits sodium and water reabsorption by the collecting duct. What type of Protein Kinase is involved?
cGMP-dependent protein kinase *ANP
Transport proteins involved in Membrane Transport
Channel Proteins - allow free movement of water and selected ions
Carrier Proteins - conformational change to transport molecules
