phys exam 1

paracellular

• what is it and what is it limited by

• diffusion between adjacent epithelial cells

• limited by TIGHT JUNCTIONS

where is tight junctions located in epithelial cells

apical membrane

transcellular

• movement through the apical or basolateral membrane

• diffuse across cytosol and exit opposite side

which membrane of the epithelial cell has the Na+/K+ pump

basolateral membrane

which membrane of the epithelial cell has Na+ channel for diffusion?

apical membrane

• e.g. Na+ reabsorption from nephron back into blood

explain reabsorption of glucose in kidney

• Na+/K+ pump on basolateral membrane establish Na+ gradient (low in epithelial cell relative to blood AND lumen

• the Na gradient enables SGLT to do active transport of glucose (cotransport with Na+) to get glucose and Na+ into the epithelial cell

• glucose then enters blood through facilitated diffusion

where is aquaporin located on epithelial cells

apical membrane

transepithelial osmosis

water moving by osmosis across an entire layer of epithelial cells

• through aquaporins and paracellular pathway (tight junctions)

• e.g. if kidney reabsorb Na+, it will also reabsorb water

where does energy for secondary active transport come from?

from electrochemical gradient, but it is still established by Na+/K+ pump that uses ATP

rate of mediated transport depends on

• solute concentration

• affinity of transporter

• number of transporter

• rate of conformational change

hyponatremia

• could be caused by__ and can lead to __

decreased plasma Na+

• could be caused by water intoxication (too much water intake e.g. marathon)

• cause ECF to be hypotonic, brain swell

hypernatremia

• could be caused by__ and can lead to __

increased plasma Na+

• caused by water loss e.g. dehydration, excessive sweat, excessive salt intake

• ECF becomes hypertonic → cell shrink

electrochemical gradient

diffusional gradient + electrical gradient

Fick’s Law

rate of diffusion = (diffusion coefficient x conc gradient x surface area)/distance

where are intracellular receptors located

cytoplasm or nucleus

intracellular receptors is faster/slower than membrane receptors? why?

slower bc they need time for protein synthesis

down regulation of receptor

decreased receptor number when exposed to high conc of messenger

up regulation of receptor

increased receptor number in response to low messenger conc

loss of function of receptor

receptor doesn’t respond to messengers in a normal way

gain of function of receptors

receptors may have overactive response to ligand or act even without binding

what kind of ligand/messenger bind to intracellular receptors

nonpolar messengers like thyroid hormone and steroids

• cortisol

• aldosterone

• testosterone

which type of receptor does insulin have

receptor that has tyrosine kinase enzyme

which type of receptor does cytokines have

cytoplasmic kinases → janus kinase

2 important effector protein in G-protein coupled receptor

• adenylyl cyclase → turns cytosolic ATP into cAMP

• phospholipades C

how is cAMP action terminated/concentration lowered

• phosphodiesterase enzyme terminates its action

• inhibitory G protein receptor also inhibit adenylyl cyclase and lower cAMP level

how does beta 1 receptor work

• G protein receptor

• epinephrine binds to the G protein receptor (beta 1)

• adenylyl cyclase makes cAMP

• cAMP activates protein kinase

• protein kinase cause more Ca2+ to be available for heart contraction

• stronger heart contraction

• heart also relaxes faster

how does ADH increase water reabsorption in kidney

when ECF osmolarity is high/blood volume low → ADH secreted and bind to G protein receptor → activate adenylyl cyclase → makes cAMP → cAMP activates protein kinases → phosphorylate proteins → increase insertion of aquaporins → increase water reabsorption

how does digitalis work

• usually Ca2+ goes out of the cell by secondary active transport (relies on Na+/K+ pump and then Na+/Ca2+ countertransport)

• blocks Na+/K+ pump

• increase intracellular Na+ bc usually 3 Na+ go out but now they can’t

• reduce function of Na+/Ca2+ secondary transporter

• Ca2+ accumulate inside the cell

• Ca/ATPase pump move Ca2+ into SR

• more Ca2+ released from SR after action potential

• increase cardiac force

what is Ca2+ ATPase

• primary active transport

• move Ca2+ from cytosol to extracellular or into organelles

hypokalemia

concentration of K+ outside of cell is low

Nernst equation

Ek=-60 log [K+]i/[K+]o

what happens is extracellular K conc is high

cell becomes more excitable - cardiac arrhythmias and death

how does aldosterone work

• ECF K+ is high

• aldosterone is produced

• aldosterone act on kidney to increase K+ secretion in urine

what’s the point of bulk flow (fluid exchange) between capillary and interstitial fluid

bring glucose and O2 from capillaries to IF and then cells

how can arterial diameter affect filtration

• vasodilation - increase filtration (less resistance → less pressure dropped)

• vasoconstriction - decrease filtration

facilitated diffusion vs ligand gated channels

• for ligand gated, the ligand bind to the receptor and changes its shape, allowing the solute to go in

• for facilitated diffusion, the solute binds to the receptor, changes its shape and then goes in

what linkage between cells for tissue

desmosomes and tight junctions

what linkage between cells form communication

gap junction - linking the cytosol

what is desmosomes made of

intermediate filaments

important example of tight junction

blood brain barrier

intestinal cell

what do peroxisomes do

use O2 to remove H+ from organic molecules

• reaction can form hydrogen peroxide, which is cytotoxic but is destroyed by peroxisomes

protein subunit of microtubule

tubulin

cilia and flagella are made of

microtubule

ribosomes are produced and assembled in

nucleolus

amino acids are made of

carboxyl group (cooh) + amino group (nh2) + side chain

affinity of hemoglobin is inversely proportional to

temperature, DPG, acidity, and CO2

• all increase during exercise - reduce affinity of O2 binding and promote O2 unloading at tissue

saturation of a ligand depends on

• concentration

• affinity

competition of ligand depends on

relative concentration and affinity

cellular metabolism can be regulated by altering

• enzyme concentration

• enzyme activity

• substrate concentration

ATP hydrolysis equation

ATP + H2O → ADP + Pi + H+ + energy

end product of glycolysis + krebs cycle + etc

34-38 ATP + 6CO2 + 6H2O

respiratory vs metabolic acidosis/alkalosis

respiratory depends on CO2, metabolic depends on H+

glycogenolysis

breakdown of glycogen in liver and muscle to glucose

lipolysis

triglycerides in adipose tissue break down into fatty acids and glycerol

glucose sparing

body use fat for energy

• produce ketone from fatty acids to provide energy for tissues including brain

• use fatty acids to produce ATP to provide energy for most tissues except brain

explain how G-protein pathway works (adenylyl cyclase)

• ligand bind to receptor, change shape → activate G-protein

• increase G-protein alpha subunit affinity for GTP (replace GDP with GTP) → alpha subunit+GTP dissociate from beta/gamma subunit]

• alpha subunit activates effector protein (e.g. adenylyl cyclase) → GTP becomes GDP and Pi

• adenylyl cyclase turns cytosolic ATP into cAMP

• cAMP act as second messenger to activate protein kinase

• protein kinase phosphorylates a lot of enzymes

action of cAMP is terminated by

phosphodiesterase

how does phospholipase C work

• ligand binds to receptor, change shape

• increase affinity for alpha subunit…

• alpha subunit activates effector protein (phospholipase C)

• phospholipase C converts PIP2 into second messengers IP3 and DAG

• IP3 acts as a ligand on ER Ca2+ channels

• DAG activates protein kinase C