Saccharides are also called carbohydrates and are macromolecules consisting only of carbon (C), hydrogen (H) and oxygen (O) atoms.
Carbohydrates are sources of energy and, in the form of sugar (saccharine = sugar) and starch, provide the main part of the energy that we need for our daily metabolism.
The most elementary carbohydrate is glucose, also known as dextrose. Unlike plants, which can synthesize glucose from photosynthesis, humans cannot meet their energy needs from self-made carbohydrates. In addition to proteins and fats, he must also consume carbohydrates, including glucose, through his diet.
The following applies: 1g of carbohydrates = approx. calorific value of 4kcal
Mono-, di-, tri- and polysaccharides
Glucose isn’t the only carbohydrate out there. There is a division of carbohydrates into categories that differ in the number of monosaccharides linked together.
The individual sugar molecules are connected to each other by glycosidic bonds.
Simple sugars (monosaccharides)
Monosaccharides are those saccharides that are made up of only one type of sugar. That is why one speaks in this context of the so-called simple sugar.
Examples of monosaccharides are:
- glucose
- fructose (fruit sugar)
- Galactose (sugar mucus)
Double sugars (disaccharides)
Disaccharides are double sugars. This means they are composed of two monosaccharides or simple sugars. Examples of disaccharides are:
triple sugars (trisaccharides)
Simultaneously to the double sugar, the so-called trisaccharides, also called triple sugars, are composed of three simple sugars.
A common example of a triple sugar:
Multiple sugars (polysaccharides)
Polysaccharides are carbohydrates made up of at least ten simple sugars. If these monosaccharides have the same structure, they are called homoglycans (homo = same). If the simple sugars differ from each other, they are called heteroglycans (hetero=unlike). Examples of polysaccharides are:
The more complex a carbohydrate, the longer it takes the body to break it down.
- Simple carbohydrates: readily available as an energy carrier → quick breakdown and processing
- Complex carbohydrates: need time before they work as energy carriers → by being broken down in stages, they can enter the blood stably over a longer period of time → longer feelings of satiety
Which foods contain carbohydrates?
Basically, carbohydrates are found in most foods. The most common examples of foods that are very high in carbohydrates/saccharides are:
grain/grain
vegetables
Other
Excess carbohydrates are converted into beneficial storage material: fat.
Why? Because fats have a higher energy value with the same storage volume:
1g fat = approx. 9 kcal
Fehling sample
The so-called Fehling test can be used to detect reducing agents in chemical substances. Reducing agents are understood to mean, inter alia, aldehydes and reducing sugars. This proof was named after Hermann Fehling in 1848 after he had demonstrated that the concentration of sugar in urine can be determined quantitatively using the titration method.
isomerism
Compounds of two or more chemical compounds are called isomers if they have the same molecular formula and molecular mass, but differ in the way their atoms are linked or arranged in space. Accordingly, isomers can be represented by different structural formulas. Isomerism mainly occurs in organic compounds, although sometimes also in inorganic coordination compounds. In isomerism there are the following areas:
stereoisomers
Stereoisomers are isomers that have identical chemical bonds but differ in the spatial arrangement of their atoms. A distinction is made between two forms of stereoisomers: the conformational isomers and the so-called configurational isomers.
Configurational isomerism in turn includes enantiomers and diastereoisomers, which we will explain to you in more detail below.
enantiomers
Enantiomers are stereoisomers that have the same constitution, i.e. are identical. In their spatial structures, enantiomers are related to a counterpart like the corresponding mirror image (non-superimposable). Enantiomers are therefore often also called mirror image isomers. This relationship is visually illustrated in the graphic above.
diastereoisomers
Diastereoisomers are stereoisomers that are chiral or achiral. Usually, diastereoisomers differ in physical and chemical properties.
What does chirality mean?
In stereochemistry, chirality means a spatial arrangement of atoms in a molecule. Chirality is found in the diastereoisomers.
Fischer projection
With the help of the Fischer projection, the spatial structures of linear, chiral chemical compounds can be clearly mapped in two dimensions. This method was developed by Emil Fischer and is often used for molecules with several adjacent stereocenters such as sugars.
Saccharides – the most important things at a glance
Finally, we have summarized the most important things for you:
- Carbohydrates (saccharides) serve as energy sources in the body (1g = 4 kcal)
- Sugar (sucrose) and starch are among the most well-known carbohydrates
- Humans have to get carbohydrates from their food, such as pasta, rice, corn or bread
- Saccharides are divided into categories: According to the number of monosaccharides linked together
- Isomers are molecules that have the same molecular formula but differ in structure. A classification of these are the stereoisomers (enantiomers and diastereoisomers)
Well done! After diligently reading through everything, you should now know everything about saccharides. Keep it up!