MCAT® ExamBiological and Biochemical Foundations of Living SystemsMedium
A patient with uncontrolled diabetes mellitus experiences persistent hyperglycemia, leading to the non-enzymatic attachment of glucose to various proteins in the body, such as hemoglobin (forming HbA1c). This process can alter protein function and contribute to long-term diabetic complications. What is the biochemical term for this non-enzymatic modification of proteins by sugars?
- AUbiquitination
- BGlycosylation
- CPhosphorylation
- DAcetylation
Show answer & explanationAnswer & explanation
Correct answer: B. Glycosylation
Glycosylation is the general term for the attachment of carbohydrate moieties to proteins or lipids. Specifically, the non-enzymatic attachment of sugars like glucose to proteins is referred to as glycation, a form of glycosylation. Option B is the best fit.
Why the other options are wrong
- A. Ubiquitination is the attachment of ubiquitin protein, often targeting proteins for degradation.
- C. Phosphorylation is the addition of a phosphate group, typically by kinases, to a protein.
- D. Acetylation is the addition of an acetyl group, commonly affecting gene expression via histone modification.
Protein Glycation
Non-enzymatic attachment of sugars (like glucose) to proteins, forming advanced glycation end-products (AGEs).
- Occurs in hyperglycemia.
- Alters protein structure and function.
- Contributes to diabetic complications.
- HbA1c is an example.
Memory trick: Sugar Sticking is Glycosylation's Gig