Plasma Membrane, CH 3 Flashcards
What are the 7 roles Proteins play in the plasma menbrane
- Water filled channels (leak or gated) allow water and ions through. 2. Carrier or transport molecules which transport specific larger molecules that otherwise couldn’t pass the membrane. 3. Inner membrane docking-marker acceptors for secretory vesicles. 4. membrane bound enzymes that control chemical reactions. 5. receptors for responding to chemical messengers (ie hormones) 6. Cell adhesion molecules (CAMs). 7. Glycoproteins help cells recognize “self”
myasthenia gravis
Channel protein pathophysiology myasthenia gravis- weakened muscles due to nonbinding of neural transmitter acytle choline to muscle
Membrane protein pathophysiology of enzymes
proximal RTA (renal tubular acidosis). Kidney can’t properly remove acids from the blood into the urine. Occurs when bicarbonate is not properly reabsorbed by the kidney’s filtering system. Caused by Cystinosis (body is unable to break down the substance cysteine)
Membrane protein pathophysiology of Receptor proteins
Diabetes mylitus II is when the patient has enough insulin but the receptor doesn’t recognize insulin so it cant enter the cell. The receptor changes shape and cant recognize insulin. Related to obesity
Membrane protein pathophysiology of anchor proteins
Hereditary spherocytosis, red blood cells are sherical not biconcave
Membrane protein pathophysiology of Carrier proteins
Diabetes Mylitus is a reduced number of carriers which causes more glucose to stay in blood.
3 types of Cell to Cell adhesion
- CAMS (integrins and cadherins) 2. Extracellular matirx or ECM 3. Cell junctions
What are the 4 types of fibers in the ECM
collagen, elastin, fibronectin, reticular
What is the ECM
Intricate mesh of fibers in a gel like substance (interstitial fluid) of complex carbohydrates
Collegen
ECM protein that forms flexible nonelastic fibers or sheets that provide tensile strength.
Reticular is a branched form of collegen
Elastin
ECM protein which allows tissues to stretch and then recoil
Fibroconectin
ECM protein promotes cell adhesion and holds cells in position
Desmosomes
Cell junction which is abundant in tissues that are subject to stretching like the heart, skin and uterus. acts like velcro and is the strongest cell junction. Connects two adjacent nontouching cells.
what are the two components of desomosomes
- Plaques (cytoplasmic thickening on the innermembrane. 2. Cadherin (CAM) filaments to connect the two plaques.
Tight Junctions
When adjacent cells adhere at the point of direct contact to prevent the passage of material between cells. Primarily in sheets of epithelial tissues. Materials have to move transcellularly (through the cells) not between.
What are Claudins (occludin)
Strand proteins that create kiss sites for epithelial near intestinal lumen to prevent leakage of digestive fluids
what are Gap Junctions and where are they found
Small tunnels formed by proteins called connexons.
Abundant in cardiac and smooth muscle
What is the role of gap junctions
Permit unrestricted passage of small nutrient molecules between cells and block larger molecules.
Allow direct transfer of small signaling molecules from one cell to another.
Action potentials and glucose in muscle tissue use gap junctions
What two properties affect the permeability of a substance?
Size and lipid solubility. Highly lipid-soluble particles dissolve in the lipid bilayer and pass through the membrane. Non-lipid soluble particles require assisted transport to move across the membrane.
What are two examples of particles that use assisted transport
Charged particles (ions) and polar molecules (glucose)
Unassisted Membrane Transport
Particles that can penetrate the plasma membrane on their own are passively driven across the membrane by diffusion down a concentration gradient or movement along an electrical gradient.
What is the passage of molecules unassisted across a membrane or within a cell from high to low concentration until equilibrium is reached
diffusion
What types of molecules use simple diffusion
Nonpolar molecules cross the membrane by dissolving in and through the bilayer down concentration gradients.
Small ions can move down electrochemical gradients through open protein channels.
What is Ficks law of diffusion?
Factors that influence the rate of net diffusion across a membrane. Concentration gradient, membrane surface area, and lipid solubility are directly proportional. Molecular weight and thickness of the membrane are indirectly proportional.
How do ions move across the membrane?
Ions move across the membrane through protein channels. Ions move through channels: down their concentration gradient or down the electrical gradient.
Channels are specific to one ion. Channels can be either opened or closed.
define osmosis
Water moves passively down its own concentration gradient, through a semi-permeable membrane, to an area of higher concentration of non-penetrating solutes.
How does water pass through a membrane?
Can easily pass through the membrnae through spaces between tails of phospholipids or through water channels called aquaporins.
How is Osmolarity measured?
Osmolarity of a solution is measured by total number of solute particles per liter.
Osmotic preassure
Osmotic pressure of a solution is the pressure that must be applied to the solution to completely stop osmosis. Therefore a solution with a high concentration of non penetrating solute exerts a greater osmotic pressure that a lower concentration solution
what is tonicitiy and the 3 types
Tonicity of a solution refers to the effect the solution has on cell volume. Hyper, Hypo and isotonic
What happens to a cell in an iso, hypo, and hypertonic solution
Iso stays the same, hypo swells, hyper shrinks
Facilitated diffusion
In facilitated diffusion is passive transport in which the carrier moves the particle down its concentration gradient. ie glucose
Active transport and its two types
Carrier molecule moves it against its concentration gradient. Primary and Secondary.
Primary
Uses ATP to move ions against their gradient. Example sodium potassium pump.
Secondary
Carrier doesn’t split ATP to move the solute, instead the solute moves along with an ion
Major ICF ions
ICF Potassium+, proteins -, phosphate -
Major ECF ions
ECF is Sodium+, CL-, Ca++
what type of transport is carrier mediated transport?
passive facilitated diffusion
What 3 characteristics control the type of material and rate of movement across the membrane in carrier-mediated transport
- Specificity- each carrier protein moves a specific compound.
- Saturation- there are a limited number of carrier proteins so there is a maximum amount that can be moved in a given time.
- competition for sites by similar compounds
What do primary active transport carriers move across the membrane?
positively charged ions. Mainly Na+, K+, H+, and Ca++
What are the two types of secondary active transport?
symport (cotransport) where the ion and solute are moving in the same direction, and antiport (countertransport) where the solute moves in the opposite direction as the ion.
What is an example of symport using Na+ as the driving ion?
Transport of glucose against its gradient into intestinal cells or kidney cells. Na+ is moving along its gradient into the cells and glucose is moving against its gradient
What ions are responsible for resting membrane potential?
Na+, K+, and A- (generic symbol for large anionic intracellular proteins)
What is the concentration and permeability of A-, Na+ and K+ at resting membrane potential
Na+ is concentrated in ECF (150 out, 15 in) and Potassium is concentrated in ICF (150 in, 5 out). A- is concentrated in the ICF (65 in) and is impermeable. Potassium is 25-20x more permeable than Na+ at resting membrane potential.
what is the typical resting membrane potential
-70mV because the inside of the cell is negative compared with the outside.
what is the primary role of the Na+–K+ Pump
to actively maintain Na+ and K+ concentration gradients. It transports 3 Na+ out of the cell for every 2 K+ it pumps in. Cell loses more positive charges than it is gains, so the inside becomes negative compare to outside.
what is it called when membrane potential reaches –70 mV and no further net movement of K+ and Na+ occurs
Cell has reached its resting membrane potential
Define equilibrium potential
A measure of the membrane potential (magnitude of the electrical gradient) that exactly counterbalances the concentration gradient for the ion.
What is the equilibrium potential for K+?
-90mV
What is the equilibrium potential for Na+?
+60mV
If the (EP) for K+ is -90mV and Na+ is +60mv why is the resting membrane potential of a cell -70mV?
because K+ is 25-30x more permeable than Na+
What type of transport pathology is pneumonia?
Diffusion: the fluid in the lungs decreases the rate at which O2 can diffuse across the membrane
tetrodotoxin (puffer fish), saxitoxin (shell fish contamination) cause what type of pathology
Facilitated diffusion: Voltage gated Na+ channel inhibited
The drug digitalis used for chronic heart failure inhibits what form of transport?
Primary active Na+-K+ pump
omeprazole acts on what type of transport
primary Active H+-K+ pump is inhibited. The drug is a proton pump inhibitor drug, that suppresses gastric acid secretion and is used for the treatment of duodenal and gastric ulcers and gastroesophageal reflux disease.
Familial hypercholestrolemia
mutations in LDL receptor protein prevents low density cholesterol from being taken up by cells and it stays in the blood. Causes deposits in the skin
Chronic granulomatous disease
Inability of phagocytes to kill microbes
• The normal functioning reaction is mediated by the phagocyte: Nicotinamide Adenine Dinucleotide Phosphate (NADPH) oxidase also called phagocyte oxidase (phox)—> oxidative burst
Na-glucose co-transporter
in GI mucosa and PCT (proximal convoluted tubule) in the kidneys, causes sever dehydration and diarrhea. oral re-hydration is necessary
furosemide
Generic lasix used to treat congestive heart failure
