Carbohydrates and Their Functions

Study Notes

Introduction

Carbohydrates are essential biomolecules for energy storage, structural support, and other biological functions.
They are composed of carbon, hydrogen, and oxygen atoms, typically in a 1:2:1 ratio.
Simple sugars (monosaccharides) are the fundamental building blocks of carbohydrates.

Monosaccharides

Monosaccharides are the simplest carbohydrates, containing a single sugar unit.
Examples of monosaccharides include glucose, fructose, and galactose.
Glucose is a crucial energy source for cells.
Fructose is found in fruits and is sweeter than glucose.
Galactose is part of lactose (milk sugar).
These sugars have different arrangements of hydroxyl groups that affect their properties such as sweetness.

Disaccharides

Disaccharides are formed by the condensation reaction of two monosaccharides.
This reaction involves the removal of a water molecule.
Common disaccharides include sucrose (glucose + fructose), lactose (glucose + galactose), and maltose (glucose + glucose).
Sucrose is table sugar. Lactose is milk sugar. Maltose is found in germinating grains.

Polysaccharides

Polysaccharides are complex carbohydrates composed of many monosaccharide units linked together.
They serve as energy storage and structural components.
Starch is a storage polysaccharide in plants, composed of amylose (linear) and amylopectin (branched) chains of glucose.
Glycogen is a storage polysaccharide in animals, similar to amylopectin but more extensively branched for quicker access to glucose.
Cellulose is a structural polysaccharide in plant cell walls, providing rigidity and strength. It's a linear chain of glucose with different bonding that makes it indigestible by most animals.
Chitin is a structural polysaccharide found in the exoskeletons of insects and crustaceans.

Functions of Carbohydrates

Energy source: Carbohydrates are the primary source of energy for most organisms. Glucose is broken down in cellular respiration to produce ATP, the energy currency of cells.
Energy storage: Starch and glycogen store glucose for later use when energy demand increases.
Structural support: Cellulose provides structural support in plant cell walls, and chitin in exoskeletons of some animals.
Cellular recognition: Carbohydrate molecules can be attached to proteins and lipids on cell surfaces, playing a role in cell recognition and signaling.
Component of other molecules: Carbohydrates are part of other important biological molecules, such as nucleic acids (ribose and deoxyribose).

Classification of Carbohydrates

Based on the number of sugar units: monosaccharides, disaccharides, polysaccharides.
Based on the chemical structure: aldoses (contain an aldehyde group) and ketoses (contain a ketone group).
Based on the role: energy storage (starch, glycogen), structural (cellulose, chitin).

Digestion and Absorption

Carbohydrates are digested in the digestive tract to monosaccharides prior to absorption.
Enzymes like amylase break down polysaccharides into disaccharides, then further into monosaccharides.
Monosaccharides are absorbed into the bloodstream and transported to cells for energy use or storage.

Health and Dietary Considerations

Carbohydrates are a vital part of a healthy diet.
Adequate intake of carbohydrates provides energy for daily activities.
However, excessive consumption of refined carbohydrates can lead to health concerns such as weight gain and an increased risk of type 2 diabetes.
Different types of carbohydrates have different effects on blood sugar levels and overall health. Dietary fiber, part of complex carbohydrates, promotes digestive health.

Description

This quiz explores the structure and types of carbohydrates, focusing on monosaccharides and disaccharides. You'll learn about the essential roles these biomolecules play in energy storage and biological processes, along with examples of each type. Test your knowledge on the properties and functions of these crucial compounds.