A 45-year-old patient presents with progressive muscle weakness, exercise intolerance, and episodes of lactic acidosis. Muscle biopsy reveals decreased ATP production despite adequate oxygen availability. Dysfunction of which cellular organelle most directly explains these findings?
Lysosome
Endoplasmic reticulum
Mitochondria
Golgi apparatus
Peroxisome
The Correct Answer is C
A. Lysosome: Lysosomes contain hydrolytic enzymes responsible for degradation of cellular waste, damaged organelles, and macromolecules. Dysfunction leads to accumulation of cellular debris and lysosomal storage diseases but does not directly impair ATP production or cause lactic acidosis under aerobic conditions.
B. Endoplasmic reticulum: The endoplasmic reticulum (ER) is involved in protein synthesis, folding, and lipid metabolism. ER dysfunction can result in misfolded proteins and stress responses, but it does not directly explain decreased ATP production or exercise-induced lactic acidosis.
C. Mitochondria: Mitochondria are the site of oxidative phosphorylation, generating the majority of ATP in the cell by utilizing oxygen to drive the electron transport chain. Dysfunction impairs aerobic ATP production, forcing cells to rely on anaerobic glycolysis, which produces excess lactate, explaining the patient’s lactic acidosis, muscle weakness, and exercise intolerance.
D. Golgi apparatus: The Golgi apparatus modifies, sorts, and packages proteins and lipids for transport within or outside the cell. While essential for cellular function, Golgi dysfunction does not directly cause a reduction in ATP generation or lactic acidosis.
E. Peroxisome: Peroxisomes contain enzymes for lipid metabolism and reactive oxygen species detoxification. Defects can cause metabolic disorders such as Zellweger syndrome, but peroxisomal dysfunction does not directly impair ATP production in aerobic conditions.
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Related Questions
Correct Answer is A
Explanation
A. Germ Theory: Germ theory is the scientific principle that specific diseases are caused by microorganisms such as bacteria, viruses, fungi, or protozoa. It shifted the understanding of disease from supernatural explanations or miasma theories to evidence-based causation. Germ theory underpins modern microbiology, infection control, and the development of vaccines and antimicrobial treatments.
B. Biogenesis: Biogenesis is the principle that living organisms arise from other living organisms, emphasizing that life does not spontaneously generate from nonliving matter. It relates to the origin of life rather than the cause of disease.
C. Virus: A virus is a microscopic infectious agent composed of nucleic acid and a protein coat that requires a host cell to replicate. Viruses are agents of disease but do not represent the broader concept of disease causation described by germ theory.
D. Scientific Method: The scientific method is a structured approach to investigation involving observation, hypothesis formation, experimentation, and conclusion. While essential to studying microorganisms and disease, it describes a process rather than the principle explaining disease causation.
Correct Answer is A
Explanation
The outer membrane of gram-negative bacteria contains lipopolysaccharide (LPS), a complex molecule with three components: lipid A, a core polysaccharide, and an O-antigen. Lipid A is embedded in the outer membrane and acts as an endotoxin. When released during bacterial lysis or multiplication, lipid A triggers a strong immune response, leading to fever, inflammation, and in severe cases, septic shock. This property makes gram-negative infections potentially life-threatening. The presence of LPS also contributes to the structural integrity of the outer membrane and provides resistance to certain antibiotics.
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