USMDO Comprehensive Study Guide Flashcards

A Comprehensive study guide set covering Cell Biology, Genetics, Human Physiology, and Human Disease for the USMDO examination.

Why are lipids notably excluded from the category of biological polymers?

Lipids do not possess a repeating monomer unit linked by covalent bonds in a chain.

What are the specific glycosidic linkages found in starch, glycogen, and cellulose?

Starch contains $\alpha$-1,4 linkages; glycogen contains $\alpha$-1,4 and $\alpha$-1,6 (branched) linkages; cellulose contains $\beta$-1,4 linkages.

Which organelle is responsible for the assembly of ribosomal subunits and the synthesis of $rRNA$?

The nucleolus (located inside the nucleus).

What is the arrangement of microtubules in centrioles compared to cilia and flagella?

Centrioles have a $9+0$ triplet arrangement, while cilia and flagella have a $9+2$ arrangement (9 doublets and 2 central).

In the fluid mosaic model, what is the specific role of cholesterol within the phospholipid bilayer?

Cholesterol acts as a fluidity buffer, preventing the membrane from becoming too fluid at high temperatures or too rigid at low temperatures.

What is the net movement of water when a cell is placed in a hypotonic solution?

Water moves into the cell toward the higher solute concentration, causing the cell to swell or lyse.

During primary active transport via the $Na^+/K^+$ ATPase, what is the ratio and direction of ion movement per $ATP$ hydrolyzed?

$3\,Na^+$ ions are pumped out of the cell and $2\,K^+$ ions are pumped into the cell.

How does a noncompetitive inhibitor affect the kinetic parameters $V_{max}$ and $K_m$?

A noncompetitive inhibitor decreases $V_{max}$ but does not change the $K_m$ (it binds to an allosteric site).

Which molecule acts as the final electron acceptor in the Electron Transport Chain ($ETC$)?

Oxygen ($O_2$), which is then reduced to form $H_2O$.

What is the function of the second messenger $IP_3$ in the Phospholipase C pathway?

$IP_3$ triggers the release of $Ca^{2+}$ from the endoplasmic reticulum.

Which specific features of Prophase I are unique to meiosis and do not occur in mitosis?

Synapsis (pairing of homologous chromosomes), tetrad/bivalent formation, and crossing over at chiasmata.

According to Chargaff's rules, how many hydrogen bonds form between Guanine ($G$) and Cytosine ($C$)?

$3$ hydrogen bonds.

Which enzyme is responsible for relieving torsional strain and supercoiling ahead of the replication fork?

Topoisomerase.

What is the difference between Southern, Northern, and Western blotting?

Southern blot detects $DNA$; Northern blot detects $RNA$; Western blot detects proteins.

Which cell types are classified as nervous tissue rather than connective tissue?

Glial cells (glia), such as astrocytes, oligodendrocytes, microglia, and ependymal cells.

Which cells in the stomach are responsible for secreting hydrochloric acid ($HCl$) and intrinsic factor?

Parietal cells.

What is the primary mechanism for transporting carbon dioxide ($CO_2$) in the blood?

Approximately $70\%$ of $CO_2$ is transported as bicarbonate ions ($HCO_3^-$).

Which hormone is produced by the kidney in response to low oxygen levels to stimulate red blood cell production?

Erythropoietin.

Which specialized immune cells are NOT classified as phagocytes but instead release histamine during inflammatory responses?

Mast cells.

Which germ layer gives rise to the nervous system, tooth enamel, and the epidermis of the skin?

Ectoderm.

How does the cause of Williams syndrome differ from that of Down syndrome?

Williams syndrome is caused by a microdeletion on chromosome 7, whereas Down syndrome is caused by aneuploidy (trisomy 21).

What is the underlying cause of the Warburg effect in cancer cells?

Cancer cells favor glycolysis and fermentation for energy production even when oxygen is present.

Which autoimmune disease is characterized by the destruction of the myelin sheath produced by oligodendrocytes in the $CNS$?

Multiple sclerosis ($MS$).

What is the shared mechanism of action for Tetanus and Botulinum toxins?

They act as proteases that cleave $SNARE$ proteins, thereby blocking the release of neurotransmitter vesicles.

How does the specific action of Cholera toxin affect $cAMP$ levels?

Cholera toxin locks the $G_s$ protein in the "on" position, leading to a constant activation of adenylyl cyclase and massive increases in $cAMP$.