Thermodynamics and Chemical bonds
What are the six primary chemical elements that compose 99% of human body mass?
Oxygen, Carbon, Hydrogen, Nitrogen, Calcium, and Phosphorus
Which mature human cells in systemic circulation completely lack a nucleus?
Mature Red Blood Cells (RBCs)
Which ecto-enzymes are anchored on the outer surface of the plasma membrane?
Nucleotide phosphatase (5'-nucleotidase) and alkaline phosphatase
Approximately what percentage of a cell's total energy expenditure is dedicated to driving active transport?
40%
A 6-year-old boy presents with progressive loss of motor skills, severe neurodegeneration, and adrenal insufficiency. Blood work demonstrates significantly elevated Very Long Chain Fatty Acids (VLCFAs) due to an ABCD1 mutation impairing beta-oxidation. What organelle is deficient in Adrenoleukodystrophy (ALD)?
Peroxisome
According to the Second Law of Thermodynamics, what must occur to the total entropy ($S$) of a system for a reaction to proceed spontaneously?
Total entropy must increase
Where does RNA processing and ribosome subunit synthesis specifically occur within the nucleus?
Nucleolus
According to the Fluid Mosaic Model, how does an increase in membrane cholesterol concentration affect membrane fluidity?
It makes the membrane less fluid on the outer surface, but more fluid in the hydrophobic core (temperature-dependent)
Per ATP molecule hydrolyzed by the primary active Na+/K+ ATPase pump, what ions are transported across the plasma membrane?
3 Na+ ions OUT of the cell, 2 K+ ions INTO the cell
A 20-year-old patient presents with stroke-like episodes, muscle weakness, severe encephalopathy, and lactic acid accumulation. Biopsy confirms a defect in mitochondrial ATP production. What is this condition called?
MELAS Syndrome (Mitochondrial Encephalomyopathy)
Under Gibbs free energy principles (Delta G = Delta H - T\Delta S), which thermodynamic condition defines a spontaneous, exergonic reaction?
Delta G < 0$ and energy is released
What functional feature distinguishes the Rough Endoplasmic Reticulum (RER) from the Smooth Endoplasmic Reticulum (SER)?
RER is studded with ribosomes for protein synthesis/folding; SER lacks ribosomes, synthesizes lipids, and detoxifies compounds
What specialized lipid anchor tethers peripheral membrane proteins to membrane microdomains known as lipid rafts?
Glycosylphosphatidylinositol (GPI) anchor
Differentiate between uniport, symport, and antiport cotransport mechanisms?
Uniport moves 1 solute; symport moves 2 solutes in the SAME direction; antiport moves 2 solutes in OPPOSITE directions
A 29-year-old female presents with acute vision loss (optic neuritis) and transverse myelitis. Diagnostic testing reveals autoantibodies against Aquaporin-4 (AQP4-IgG) at the blood-brain barrier. What channelopathy is present?
Neuromyelitis Optica Spectrum Disorder (NMOSD)
What noncovalent interaction causes nonpolar side chains to aggregate together in aqueous solution by eliminating water molecules rather than dissolving?
Hydrophobic interaction
Which cellular organelle receives proteins from the ER at its cis face, modifies them through its medial cisternae, and packages them at its trans face for destination delivery?
Golgi Apparatus
What flask-shaped invaginations of lipid rafts require the structural protein caveolin for membrane transport and signal transduction?
Caveolae
Antibiotic ionophores facilitate ion movement across membranes[cite: 44]. Which ionophore acts as a mobile ion carrier, and which acts as a channel former?
Valinomycin is a mobile ion carrier; Gramicidin is a channel former
A cancer patient receiving systemic chemotherapy develops multidrug resistance. Tumor biopsy shows overexpression of P-glycoprotein (P-gp). By what mechanism does P-gp cause drug resistance?
Regulating the ATP-dependent efflux of anticancer medicines out of the cell
A bioenergetics researcher measures a metabolic reaction at body temperature and finds that enthalpy change Delta H = +30 kJ/mol and T\Delta S = +10 kJ/mol. What is the calculated Gibbs free energy change (Delta G), and how is this reaction classified?
Delta G = +20 kJ/mol; Endergonic and non-spontaneous (requires energy input)
Peroxisomes contain peroxidases and which primary protective enzyme to destroy unwanted hydrogen peroxide and free radicals?
Catalase
How do prokaryotic cell envelopes differ from animal cell membranes?
Prokaryotes have a cell wall made of repeating NAM-NAG units surrounding their plasma membrane to resist osmotic pressure; animal cells lack a cell wall
What type of ion channel opens in response to a chemical messenger (such as acetylcholine binding at the postsynaptic neuromuscular junction)?
Ligand-gated channel
A 15-year-old girl presents with progressive paralysis of eye muscles (ophthalmoplegia), pigmentary retinopathy, and cardiac conduction blocks. Analysis reveals defects in mitochondrial DNA coding for ATP synthesis enzymes. What is the diagnosis?
Kearns-Sayre Syndrome