Classifications of Carbohydrates

Study Notes

Classification of Carbohydrates

Monosaccharides: single sugar molecules, including glucose, fructose, and galactose
Disaccharides: sucrose (glucose + fructose), lactose (glucose + galactose), and maltose (2 glucose)
Oligosaccharides: raffinose and stachyose
Polysaccharides: starch (plant-based), glycogen (stored energy in muscles and liver), and cellulose (plant-based)

Carbohydrate Digestion and Absorption

Amylase in saliva breaks down carbohydrates
Lactase, maltase, and sucrase break down their respective disaccharides into monosaccharides
Carbohydrates are broken down into monosaccharides before being absorbed into the bloodstream

Metabolism of Carbohydrates

Excess glucose is converted to glycogen via glycogenesis, which requires energy and occurs in the liver or muscles
When energy is needed, glycogen is broken down into glucose via glycogenolysis, producing lots of ATP

Blood Glucose Regulation

High blood sugar promotes insulin to stimulate glucose uptake
Low blood sugar promotes glucagon to stimulate glycogen breakdown to form glucose for energy

Choosing a Carbohydrate Source

Nutrient density: the amount of nutrients per amount of food
Glycemic index: measures how quickly a food raises blood sugar levels
Glycemic load: takes into account the amount of carbohydrates consumed
Fructose content: high fructose intake is associated with negative effects
Fibre content: foods high in fibre are lower in GI and reduce the risk of negative effects

Glycemic Index Studies

Low and high GI foods have similar outcomes when caloric intake is controlled
Fibre is a significant confounder
Baseline characteristics and variability in findings affect outcomes
GI studies have limitations, including assessment on an empty stomach and variability in preparation and lifestyle

Fructose Metabolism

Fructose has a different metabolic fate than glucose
Fructose goes straight to the liver to be transformed to glucose via fructolysis
Fructose has no negative feedback loop and can deplete energy stores
Fructose is associated with increased blood pressure, type 2 diabetes, and obesity

Fructose Animal Studies

High fructose intake leads to increased body weight, food intake, blood glucose, and decreased insulin
Fructose intake is associated with increased uric acid and triglycerides

Fructose Survival Hypothesis

Fructose turns on a survival switch to prepare for periods of starvation
Increased fructose intake leads to increased blood pressure, eating, fat storage, insulin resistance, and low-grade inflammation

Fructose Human Studies

High fructose intake increases visceral adiposity and leads to weight gain
Fructose intake is associated with negative health effects, including increased blood pressure, type 2 diabetes, and obesity

Description

Learn about the different classifications of carbohydrates including monosaccharides, disaccharides, oligosaccharides, and polysaccharides. Discover examples of each type and how carbs are transformed into glucose to produce energy.