O que seria um carboidrato?

What Is a Carbohydrate?

Carbohydrates are sugars. They're the primary energy storage molecule for life on Earth. They have a simple chemical ratio of 1 carbon to 2 hydrogen to 1 oxygen atom. This is often written as $CH_{2}O$.

Plants perform photosynthesis to make these sugars by using a water molecule, $CO_{2}$ (carbon dioxide), and energy from the sun.

The simplest carbohydrates are called monosaccharides. A monosaccharide is the monomer, or building block, for all other types of carbohydrates. Glucose is the most important monosaccharide and is used by organisms in cellular respiration to produce usable energy for the body.

When two monosaccharides bond together, they are called a disaccharide. (It helps to remember that di means two and mono means one.) Examples of disaccharides include sucrose and lactose. These are easily broken down by animals and bacteria to get glucose, which is then used for cell functions.

Large strings or clusters of monosaccharides are called polysaccharides (poly means many). They are used either as energy storage molecules or as structural molecules.

Examples include glycogen, cellulose, starch, and chitin. Glycogen stores energy for humans (in the liver), while starch performs the same function in plants. Cellulose makes up plant cell walls, giving them their square shape. Finally, chitin is what makes up the hard exoskeletons of insects.

To summarize, carbohydrates are efficient at energy storage. Plants form them through photosynthesis, and animals eat plants to access the energy trapped in them.

Key Vocabulary:

1. Carbohydrate
2. Polysaccharide
3. Monosaccharide
4. Disaccharide
5. Glucose

Simple Sugars and Polysaccharides

Carbohydrates are molecules that are made of two or more simple sugars. They are polymers made of a ratio of 1 carbon, 2 hydrogen, and 1 oxygen atom. They are the main source of energy for most living things.

You're probably wondering, "Well, what is a simple sugar?" They are small sugar molecules which are also called monosaccharides. You've probably heard of a few kinds of simple sugars before such as glucose and fructose.

Regular table sugar, sucrose, is a compound made from both glucose and fructose. This type of sugar is called a disaccharide, which is a compound made by joining two simple sugars together.

Polysaccharides are macromolecules formed from monosaccharides. These are called complex carbohydrates.

Animals use a polysaccharide called glycogen (sometimes called animal starch) to store excess sugar. If your blood sugar ever gets too low, glycogen will be broken down into glucose molecules for more energy.

Plants also use polysaccharides (starch) for storing excess sugars. They use a complex carbohydrate called cellulose for structural strength. Large amounts of cellulose are present in wood and paper.

$$\color{#8925AE}{\text{Vocabulary Review:}}$$

$\color{#8925AE}{\text{Monomer}}$ : Any molecule that can react with other molecules of the same or different makeup to form a chain, or polymer

$\color{#8925AE}{\text{Polymer}}$ : A chain of monomers made of a specific type of compound

$\color{#8925AE}{\text{Macromolecule}}$ : A polymer that has a large (macro) molecular mass. There are four main types in organisms: carbohydrates, proteins, lipids, and nucleic acids

$\color{#8925AE}{\text{Monosaccharide}}$ : The most basic types of sugars, called simple sugars

$\color{#8925AE}{\text{Polysaccharide}}$ : A polymer of simple sugars

$\color{#8925AE}{\text{Carbohydrate}}$ : A polymer of sugars or starch monomers

The Main Energy Source

Carbohydrates are the main energy source for living organisms. Also known as sugars, they are made up of the monomer monosaccharides. These monomers bond together to make polysaccharides, which are polymers. The terms monomer and polymer can be confusing. It might help to think of monomers as one bead and then polymers as a whole bracelet.

Carbohydrates are made of carbon, hydrogen, and oxygen atoms. The hydrogen bonds between the hydrogens and oxygens typically make them dissolve easily in water. These hydrogen bonds also make hydrolysis reactions possible. Hydrolysis reactions are where the carbohydrates react with water to break down into smaller molecules. This allows them to be used as a source of energy.

Carbohydrates are also really important in a process called cellular respiration. This is where glucose or other sugars are broken down to form more energy as ATP.

Carbohydrates are found in a variety of different foods and are necessary for survival.

(Video) Biological Molecules - You Are What You Eat

by CrashCourse

You've probably seen the word carbohydrates on food labels before, but why exactly are they so important? This clip from Crash Course goes through their structures, what they're used for, and some common examples of them.