Protein Structural Levels & Bonds
Secondary structures like the alpha-helix and beta-pleated sheet are primarily stabilized by which type of chemical interaction?
Backbone-to-backbone hydrogen bonds
What is the quaternary subunit architecture of adult human hemoglobin?
Heterotetramer composed of two alpha chains (141 residues) and two beta chains (146 residues) (alpha_2\beta_2)
What specific misfolded protein aggregate forms extracellular plaques in the cerebral brain tissue of Alzheimer's disease patients?
Amyloid-beta (Abeta)
What basic functional components surround the central alpha-carbon in a standard alpha-amino acid?
An amine group, a carboxyl group, a hydrogen atom, and a variable side chain (R-group)
Which organelle acts as the powerhouse of the cell by converting metabolized nutrients into Adenosine Triphosphate (ATP) via cellular respiration?
Mitochondrion
What are the key chemical characteristics of the peptide bond in primary protein structure?
It is a partial double bond with a trans C-N configuration
What central prosthetic component inside each hemoglobin subunit reversibly binds oxygen?
A protoporphyrin IX ring with a central ferrous iron (Fe2+)
In Parkinson's Disease, toxic intracellular aggregates known as Lewy bodies are composed of which misfolded protein?
alpha-Synuclein
How are amino acids categorized based on nutritional essentiality?
Indispensable (Essential), Conditionally Essential (Partially Essential), and Dispensable (Non-Essential)
What structural feature of the mitochondrial inner membrane dramatically increases surface area for housing the Electron Transport Chain and ATP synthase enzymes?
Cristae
Which amino acid residue has a sulfhydryl (-SH) side chain capable of forming interchain or intrachain disulfide (-S-S-) covalent bonds to stabilize tertiary protein structure?
Cysteine
How many total molecules of oxygen (O2) can be bound by a single, fully saturated hemoglobin tetramer?
4
What pathological mechanism underlies Prion diseases such as Creutzfeldt-Jakob Disease (CJD) and kuru?
Misfolded infectious prion proteins converting normal cellular proteins into pathogenic forms
What type of reaction occurs when the alpha-amino group of an amino acid is transferred to an alpha-keto acid to form a new amino acid and a new keto acid?
Transamination
In specialized brown adipose tissue, how do mitochondria generate heat directly (thermogenesis) rather than capturing energy as ATP?
By uncoupling ATP production to release energy directly as heat
How are oligopeptides and proteins classified based on their total number of polymerized amino acid residues?
Dipeptide = 2; Tripeptide = 3; Polypeptide = 10–50; Protein = 50+ residues
Compare the structural and functional properties of hemoglobin's Tense (T) state versus its Relaxed (R) state?
T-state is deoxygenated (Deoxy-Hb) with low O2 affinity (stabilized by intra-subunit salt bridges); R-state is oxygenated (Oxy-Hb) with high O2 affinity (salt bridges rupture)
Amyotrophic Lateral Sclerosis (ALS) involves misfolding, nuclear depletion, and cytoplasmic clumping of which proteins in motor neurons?
SOD1, TDP-43, and FUS
What is the Isoelectric Point (pI) of an amino acid, and what is its net charge state at this specific pH?
The specific pH at which a dipolar zwitterion carries zero net electrical charge
Beyond ATP production, what central role do mitochondria play when a cell undergoes irreversible damage?
Regulating programmed cell death (apoptosis) by releasing signaling proteins like cytochrome c
An investigator synthesizes a peptide containing a free alpha-amino group on the left terminal residue and a free alpha-carboxyl group on the right terminal residue. How are these ends designated, and where is the N-terminal residue written by convention?
N-terminal (free alpha-amino) on the left; C-terminal (free alpha-carboxyl) on the right
A patient exercising heavily produces metabolic byproducts in peripheral tissues. According to the Bohr effect, how do allosteric effectors like H+, CO2, and 2,3-BPG alter hemoglobin's oxygen binding curve?
They shift the curve to the right, stabilizing the T-state to promote oxygen release in active tissues
A 42-year-old patient presents with chorea, severe cognitive decline, and psychiatric disturbances. Genetic analysis confirms an autosomal dominant mutation producing nuclear and cytoplasmic protein aggregates in neurons. Which disease and mutant protein are present?
Huntington's Disease (abnormal, expanded huntingtin protein)
An investigator analyzes a pentapeptide with the sequence Asp-Lys-Gly-Arg-Glu. At physiological pH (pH = 7.0), what is the approximate net charge of this peptide?
0
A neonatal patient presents with severe neurological degeneration and liver dysfunction. Laboratory testing demonstrates a significant systemic accumulation of Very Long Chain Fatty Acids (VLCFAs). Based on the provided material, which organelle is dysfunctional?
Peroxisome