Chapter 3: Carbohydrates: Structure, Function, and Metabolism

Carbohydrates

Compounds of carbon, hydrogen, and oxygen.

Monosaccharides

Single sugar units; examples include glucose.

Disaccharides

Two sugar units linked together.

Polysaccharides

Complex carbohydrates with 10+ monosaccharides.

Glycogen

Animal carbohydrate storage form, found in liver.

Starch

Plant carbohydrate storage, exists as amylose and amylopectin.

Fiber

Nondigestible plant parts; supports structure.

Condensation

Process forming disaccharides; releases water.

Hydrolysis

Splitting disaccharides; adds hydrogen and hydroxyl.

Simple Carbohydrates

Contain one or two sugar molecules.

Complex Carbohydrates

Contain hundreds to thousands of sugar molecules.

Glucose

Blood sugar; major energy source.

Fructose

Sweetest natural sugar; found in fruits.

Galactose

Milk sugar; combines with glucose in lactose.

Maltose

Disaccharide of two glucose units.

Sucrose

Table sugar; glucose and fructose combined.

Lactose

Milk sugar; glucose and galactose combined.

Oligosaccharides

Carbohydrates with 3 to 10 monosaccharides.

Raffinose

Oligosaccharide of galactose, glucose, and fructose.

Stachyose

Oligosaccharide of two galactose, one glucose, and one fructose.

Dietary Fiber

Nondigestible plant parts; supports plant structure.

Functional Fiber

Nondigestible carbohydrates with health benefits.

Total Fiber

Sum of dietary and functional fiber.

Soluble Fiber

Dissolves in water; slows nutrient absorption.

Insoluble Fiber

Does not dissolve; increases fecal bulk.

Energy Yield

Monosaccharides provide 4 kcal/g.

Protein-Sparing

Carbohydrates preserve protein for tissue repair.

Brain Energy Source

Carbohydrates are primary energy for brain.

Fat Metabolism Regulator

Carbohydrates prevent incomplete fat oxidation.

Mastication

Mechanical breakdown of food mixed with saliva.

Salivary Amylase

Enzyme that breaks down starch into sugars.

Absorption

Process of nutrients entering the bloodstream.

Pancreatic Secretions

Contain enzymes for carbohydrate digestion.

Liver Conversion

Galactose and fructose converted to glucose.

Insulin

Hormone that promotes glucose uptake by cells.

Blood Glucose Levels

Normal range is 70-130 mg/dL.

Glucagon

Hormone that raises blood glucose levels.

Cortisol

Hormone that promotes gluconeogenesis.

Epinephrine

Hormone that stimulates glycogen breakdown.

Growth Hormone

Acts as an insulin antagonist.

Thyroxine

Regulates insulin destruction and epinephrine release.

Glycogenesis

Formation of glycogen from glucose.

Glycogenolysis

Breakdown of glycogen to glucose.

Gluconeogenesis

Synthesis of glucose from non-carbohydrate sources.

Glycolysis

Breakdown of glucose to pyruvate.

Krebs Cycle

Aerobic process producing ATP and CO2.

Dental Caries

Tooth decay caused by high sugar intake.

Obesity

Excess fat accumulation from high carbohydrate intake.

High Blood Triglyceride Levels

Increased triglycerides from high carbohydrate diets.

Hyperactivity

Potential link to carbohydrate consumption in children.

Flatus

Gas formation from indigestible carbohydrates.

Cancer

High fiber diets may reduce cancer risk.

Marasmus

Severe undernutrition with weight loss and muscle wasting.

Diabetes

High fiber delays glucose absorption; sugar promotes obesity.

Nutrient Deficiencies

High carbohydrate diets may displace nutritious foods.

Artificial Sweeteners

Substitutes for carbohydrates; include saccharin and aspartame.

Glycemic Index

Measures food's effect on blood glucose levels.

Aspartame

What artificial sweetener must patients with PKU avoid?

Saccharin and Acesulfame-k

Have been associated with cancer, but studies have shown that they are safe for use.