Page 93 - First Aid for the USMLE Step 1 2020, Thirtieth edition [MedicalBooksVN.com]_Neat
P. 93
BIOCHEmISTRY ``BIOCHEMISTRY—CEllUlAR BIOCHEmISTRY ``BIOCHEMISTRY—CEllUlAR SECTION II 49
Cilia structure 9 doublet + 2 singlet arrangement of Kartagener syndrome (1° ciliary dyskinesia)—
microtubules A . immotile cilia due to a dynein arm defect.
Basal body (base of cilium below cell Autosomal recessive. Results in male and
membrane) consists of 9 microtubule female fertility due to immotile sperm and
triplets B with no central microtubules. dysfunctional fallopian tube cilia, respectively;
Axonemal dynein—ATPase that links peripheral risk of ectopic pregnancy. Can cause
9 doublets and causes bending of cilium by bronchiectasis, recurrent sinusitis, chronic
differential sliding of doublets. ear infections, conductive hearing loss, and
Gap junctions enable coordinated ciliary situs inversus (eg, dextrocardia on CXR C ).
movement. nasal nitric oxide (used as screening test).
(Kartagener’s restaurant: take-out only; there’s
no dynein “dine-in”.)
A B C
Dynein
arm R L
Microtubule
A
Microtubule
B
Nexin
Sodium-potassium Na -K ATPase is located in the plasma Pumpkin = pump K in.
+
+
+
pump membrane with ATP site on cytosolic side. Ouabain (a cardiac glycoside) inhibits by
+
+
For each ATP consumed, 3 Na leave the cell binding to K site.
+
(pump phosphorylated) and 2 K enter the Cardiac glycosides (digoxin and digitoxin)
+
+
cell (pump dephosphorylated). directly inhibit the Na -K ATPase, which
2+
Plasma membrane is an asymmetric lipid leads to indirect inhibition of Na /Ca
+
2+
bilayer containing cholesterol, phospholipids, exchange [Ca ] i cardiac contractility.
sphingolipids, glycolipids, and proteins.
Extracellular 3Na + 2K +
space
Plasma
membrane
P
Cytosol 2K +
3Na + ATP ADP P
FAS1_2019_01-Biochem.indd 49 11/7/19 3:16 PM
