glucose
Summary
Glucose is a simple sugar (monosaccharide) that serves as the primary energy source for cellular metabolism. Normal blood glucose levels are tightly regulated (70-100 mg/dL fasting) through hormonal control involving insulin and glucagon. Dysregulation leads to diabetes mellitus and associated complications.
Detail
Glucose (C6H12O6) is the most important carbohydrate in human metabolism and the preferred fuel for the brain, which requires ~120g daily. It's absorbed in the small intestine via SGLT1 and GLUT2 transporters, then distributed via circulation. Cellular uptake occurs through GLUT transporters (GLUT1 in brain/RBCs, GLUT4 in muscle/adipose tissue - insulin-dependent). Glucose metabolism includes glycolysis (cytoplasm), citric acid cycle, and oxidative phosphorylation (mitochondria), yielding 30-32 ATP molecules per glucose. Blood glucose regulation involves: insulin (decreases glucose via uptake and glycogen synthesis), glucagon (increases glucose via glycogenolysis/gluconeogenesis), cortisol, epinephrine, and growth hormone. Pathological states include diabetes mellitus (Type 1: autoimmune β-cell destruction; Type 2: insulin resistance), hypoglycemia (<70 mg/dL causing neuroglycopenic symptoms), and diabetic complications (nephropathy, retinopathy, neuropathy, accelerated atherosclerosis). Glucose testing includes fasting glucose, oral glucose tolerance test, and HbA1c for long-term glycemic control.
Sources
- Biochemistry by Lippincott
- Harrison's Principles of Internal Medicine
- First Aid for the USMLE Step 1
- Robbins Basic Pathology
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