AAMC1: BBCF Flashcards
endomembrane system
location of post-translational modifications for secreted / membrane proteins
– requires a signal sequence for initial binding of protein to rough ER
modified protein gets sent to the golgi w a second signal sequence that tells it where to go
NAD+ / NADH redox locations
NAD+ is the oxidized form, and NADH is the reduced form of nicotinamide adenine dinucleotide
NAD+ is neither reduced to form NADH, nor is NADH oxidized to form NAD+ specifically during chemiosmosis
Glycolysis and Krebs require the reduction of NAD+ into NADH; ETC requires the oxidation of NADH into NAD+
draw cholesterol
mark as 1 til perfect
When concentrated urine is being produced, in which of the following regions of the kidney will the glomerular filtrate reach its highest concentration?
A. Proximal convoluted tubule
B. Distal convoluted tubule
C. Cortical portion of the collecting duct
D. Medullary portion of the collecting duct
The answer is D because glomerular filtrate is most concentrated in the medullary portion of the collecting duct, compared to the other kidney structures listed.
filtration in the kidney
- 2 types of pressure
begins in the Bowman’s capsule, where blood is filtered from the circulatory system into the tubules through a semipermeable membrane
Hydrostatic pressure is the pressure inside the glomerulus
– if greater than oncotic, will push fluid / ions out
Oncotic pressure (aka osmotic) is the pressure on the glomerulus -- if greater than hydrostatic, will pull fluid / ions in or prevents it from leaving
what maximizes filtration?
maximizing the pressure diff btwn hydrostatic and oncotic
Therefore, a maximally dilated afferent arteriole (brings blood to the glomerulus) and a maximally constricted efferent arteriole (takes blood away from glomerulus) is going to maximize the pressure differential; this yields the greatest net filtration
counter current system
refers to the shape of the loop of henle alongside blood that regulates the concentration of the urine
In the medulla (inside) of the kidney, the interstitial fluid is very concentrated, while in the cortex, (outside), the interstitial fluid is less concentrated.
Because of this, the bottom of the loop of henle can concentrate the urine, while the urine can be diluted/ fine tuned at the tops of the loop.
reabsorption in the nephron
- movement via diffusion
- movement via transporters
- pathway
PASSIVE DIFFUSION: movement of water or ions down their concentration gradients
ACTIVE TRANSPORT: substances are moved up / against their concentration gradient
pathway of reabsorption
- proximal convoluted tubule (early and late)
- loop of henle (proximal straight tubule + thick ascending limb)
- distal convoluted tubule
- collecting duct
pathway of reabsorption
- proximal convoluted tubule (early and late)
EARLY PROX CON: reabs of essential substances (glucose, AA, phosphate, lactate / citrate) via “piggybacking” on sodium co-transporters (sodium in, something else out), thus requires sodium gradient to be maintained in a way that Na+ doesn’t build up inside the tubule
- Na/K ATPase: pulls 3 Na+ out and 2 K+ in
- Na/H+ exchanger: allows for reabs of bicarbonate
LATE PROX CON: now depleted of essential substances; reabs of chloride ions via diffusion into the bloodstream
pathway of reabsorption
- loop of henle
location of countercurrent multiplication / change in blood osmolarity
– regulates body fluid homeostasis via water reabsorption
PROX STRAIGHT: aka thin descending; reabs of phosphate and water
– walls here are permeable to water
THICK ASCENDING: reabs of Na/Cl via three-ion cotransporter (Na actively pumped out while K/Cl diffuse down their gradients)
– walls here are NOT permeable to water
pathway of reabsorption
- distal convoluted tubule
- collecting duct
terminal nephron
DISTAL CON: final official area of reabs of sodium, regulated by Na/K ATPase
COLLECTING DUCT: finetuning to decide how much sodium will be excreted
– acted on by ADH / aldosterone
kinetic v thermodynamic diff
kinetic = determined by reaction rate; can be increased with temperature
thermodynamic = how spontaneous it is; not necessarily related to how fast a molecule is moving
function of Na/K ATPase
Na+K+ ATPase transports 3 sodium ions out of the cell and 2 potassium ions into the cell with each ATP hydrolyzed
Na+K+ ATPase functions to restore the resting membrane potential by moving the ions against their concentration gradients
Also found in nephron (specifically the distal convoluted tubule and collecting duct) for urine concentration
ABC transporter
ABC stands for ATP-binding cassette, thus transporters of this subset require ATP in order to transport their substrates = aka ACTIVE TRANSPORT
lipid raft
provide rigidity to the fluid membrane, especially during higher temperature; they contain cholesterols and sphingolipids
