MCAT® ExamBiological and Biochemical Foundations of Living SystemsHard
A patient with uncontrolled diabetes mellitus experiences persistent hyperglycemia. Over time, this leads to the non-enzymatic attachment of glucose molecules to various proteins, such as hemoglobin, forming advanced glycation end products (AGEs). This process contributes to many long-term complications of diabetes. What is the biochemical term for this non-enzymatic modification of proteins by sugars?
- AAcetylation
- BPhosphorylation
- CGlycation
- DGlycosylation
Show answer & explanationAnswer & explanation
Correct answer: C. Glycation
Glycation specifically refers to the non-enzymatic attachment of sugars to proteins or lipids, forming products like AGEs. Glycosylation, while also involving sugar attachment, is an enzyme-catalyzed process.
Why the other options are wrong
- A. Acetylation is the enzymatic addition of an acetyl group.
- B. Phosphorylation is the enzymatic addition of a phosphate group.
- D. Glycosylation is the enzymatic addition of carbohydrates to proteins or lipids.
Protein Glycation in Diabetes
A non-enzymatic reaction where reducing sugars (like glucose) spontaneously attach to amino groups of proteins, forming stable adducts and eventually advanced glycation end products (AGEs). This process is accelerated by hyperglycemia and contributes to diabetic complications.
- Non-enzymatic process.
- Involves reducing sugars (e.g., glucose) and proteins/lipids.
- Forms Schiff bases and Amadori products, eventually AGEs.
- Accelerated by high blood glucose (hyperglycemia).
- Contributes to microvascular and macrovascular complications in diabetes.
Memory trick: Glycation: Glucose's 'sticky' non-enzymatic hug.