Carbohydrates Exam Guide PDF

**Carbohydrates** - Carbohydrates are compounds that provide chemical energy to cells. - They are primarily sugars and starches. - Carbohydrates are a primary energy source for the brain, erythrocytes, and retinal cells. **Carbohydrate Structure and Classification** - Carbohydrates...

**Carbohydrates** - Carbohydrates are compounds that provide chemical energy to cells. - They are primarily sugars and starches. - Carbohydrates are a primary energy source for the brain, erythrocytes, and retinal cells. **Carbohydrate Structure and Classification** - Carbohydrates contain carbon (C), hydrogen (H), and oxygen (O). - \"-ose\" suffix signifies a sugar. - Classification is based on: - Number of sugar units (monosaccharides, disaccharides, oligosaccharides, polysaccharides) - Size of the base carbon chain (trioses, tetroses, pentoses, hexoses) - Location of the carbonyl group (aldehyde or ketone) - Stereochemistry of the compound **Classification of Carbohydrates (continued)** - Trioses - 3 carbons - Tetroses - 4 carbons - Pentoses - 5 carbons (e.g., DNA) - Hexoses - 6 carbons (e.g., glucose) **Location of Carbonyl Group** - Aldose: carbonyl group at end (aldehyde group) - Ketose: carbonyl group in the middle (ketone group) **Number of Sugar Units** - Monosaccharides: one sugar unit (e.g., glucose, fructose, galactose) - Disaccharides: two sugar units (e.g., maltose, lactose, sucrose) - Oligosaccharides: 3-10 sugar units - Polysaccharides: \>10 sugar units (e.g., starch, glycogen, cellulose) **Chemical Properties of Carbohydrates** - Reducing carbohydrates: contain ketone or aldehyde groups (e.g., glucose, maltose) - Non-reducing carbohydrates: do not contain ketone or aldehyde groups (e.g., sucrose) **Carbohydrate Metabolism** - Begins in the mouth with salivary amylase breaking down polysaccharides - Monosaccharides are absorbed by the gut and transported to the liver. - Glucose is the only carbohydrate that is directly used for energy or stored as glycogen. - Pathways of glucose metabolism - Liver and muscle glycogen storage - Conversion to amino acids and proteins - Conversion to fats - Ultimate goal is metabolism to CO₂ and H₂O **Glucose Breakdown (Glycolysis, Glycogenolysis, Glycogenesis)** - **Glycolysis:** Conversion of glucose to lactate or pyruvate, providing energy. - **Glycogenesis:** Conversion of glucose to glycogen for storage (primarily in liver and muscle). Excess glucose is stored as glycogen. - **Glycogenolysis:** Breakdown of glycogen to glucose when blood glucose levels are low. **Glucose Formation (Gluconeogenesis)** - **Gluconeogenesis:** Formation of new glucose from non-carbohydrate sources (e.g., amino acids, glycerol, fatty acids) - Occurs primarily in the liver. - Important in starvation and weight loss - Protects the body, especially the brain. **Carbohydrate Metabolism (Lipolysis, Lipogenesis)** - **Lipogenesis:** Conversion of carbohydrates to fatty acids. Excess glucose is stored as fat. - **Lipolysis:** Decomposition of fat. **Regulation of Plasma Glucose** - **Glycogenolysis:** Released glucose into the blood (quick response). - **Gluconeogenesis, and lipolysis**: Longer response. Release glucose into the blood. - **Glycogenesis:** Liver stores glucose. - **Insulin** decreases glucose levels - **Glucagon** increases glucose levels. - **Epinephrine and Cortisol** increase glucose levels. - **ACTH** increases glucose levels **Hormones Affecting Glucose Levels** - Insulin: decreases blood glucose by facilitating glucose entry into cells and promoting glycolysis. - Glucagon: increases blood glucose by stimulating glycogenolysis and gluconeogenesis. - Epinephrine and Cortisol: increase blood glucose by stimulating glycogenolysis, gluconeogenesis, and lipolysis. - Adrenocorticotropic Hormone (ACTH): increases blood glucose by stimulating the adrenal cortex to release cortisol **Other Hormones Affecting Glucose Levels** - TSH (thyroid-stimulating hormone): increases glucose absorption from intestines. - Somatostatin: inhibits insulin, thus increasing glucose. **Types of Diabetes** - Type 1 Diabetes: Insulin-dependent diabetes mellitus (IDDM), autoimmune destruction of islet beta cells; usually in children and adolescents - Type 2 Diabetes: Non-insulin-dependent diabetes mellitus (NIDDM), insulin resistance; usually in adults; related to obesity, lack of exercise, diet, and genetic factors - Secondary Diabetes: due to other conditions such as genetic defects, pancreatic disease, endocrinopathies or drug-induced - Gestational Diabetes (GDM): glucose intolerance during pregnancy, usually resolves after delivery but increases risk of later diabetes **Diabetes Diagnosis Criteria** - Symptoms of diabetes plus random plasma glucose \>200 mg/dL. - Fast blood glucose \>126 mg/dL - 2-Hour glucose \> 200 mg/dL during an oral glucose tolerance test (OGTT) - Hemoglobin A1c (HbA1c) \> 6.5%. Confirmed on repeat measurement **Prediabetes** - Fasting glucose between 100-125mg/dL - 2-hr GTT results between 140-199mg/dL - HbA1c between 5.7-6.4% **GDM Testing** - Moms screened at weeks 24-28 - 2-hr GTT, fasting, 1 hour, and 2 hours after 75-g glucose load - Diagnosis: Fasting \>92mg/dl, 1 hour \>180mg/dl, and 2 hour \>153mg/dl **Hypoglycemia** - Plasma glucose level falls below 60 mg/dL - Release of glucagon, epinephrine, cortisol, and growth hormone. - Treatment varies with cause (small, frequent meals, low in carbs, high in protein). **Lab Findings for Hypoglycemia** - Low plasma glucose levels - Glucose. - Insulin level **Galactosemia** - Caused by a deficiency in galactose-1-phosphate uridyltransferase. - Results in the inability to convert galactose to glucose or lactose to glucose. - Symptoms: failure to thrive, mental retardation, cataracts, and death. **Laboratory Testing Considerations for Glucose** - Reference values depend on various factors, including the type of specimen (venous/capillary, serum/plasma/whole blood), how it was collected (fasting/random/after meal) - Reference range for glucose (serum/plasma): 74-100 mg/dL. Whole blood is 65-95mg/dl. - Specimen collection methods - Serum, plasma, whole blood - Point-of-care - Results are 10-15% lower for whole blood than serum/plasma due to dilution by cells **Glucose - Specimen Collection and Testing** - **CSF specimens**: Analyzed ASAP; 60-70% of current blood glucose level. - **24-hour urine**: A small amount of glucose is lost daily (\