Organic Compounds

Organic Compounds and biomolecules

The chemical compounds associated to life processes are known as organic compounds. Among the organic compounds, the most known belong to four categories:

1- CARBOHYDRATES2- LIPIDS3- PROTEINS4- NUCLEIC ACIDS

Carbon is the Basic Element of Biomolecules

Carbon is the Basic Element of Biomolecules

A single bacterial cell may contain up to 5000 different biomolecules, plants and animals even more.All the organisms in the side picture use a different carbohydrate as structural molecule.

This variety of biomolecules is given by the complex chemistry of carbon

Organic Compounds and biomolecules

Carbon is the Basic Element of Biomolecules

Organic Compounds and biomolecules

Carbon needs four electrons to complete its outer electronic shell. Hence every single carbon can share electrons with as many as four other atoms like in the octane molecule.

Furthermore the carbon-carbon bond is a covalent and stable bond, so it can form very long and strong carbon chains.

C

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Carbon is the Basic Element of Biomolecules

Organic Compounds and biomolecules

The great variety of biomolecules is given by the functional groups that confer typical features to the molecules.

Func t iona l g roups a re specific combinations of atoms that always react in the same way.

A single functional group can change the chemical properties of the whole organic molecule

Carbon is the Basic Element of Biomolecules

Organic Compounds and biomolecules

Macromolecules are large molecules (polymers) composed by molecular subunits (monomers) linked together.

*The biggest macromolecules are polymers, large molecules composed of repeating structural units (monomers), normally connected by covalent bonds

MACROMOLECULESMACROMOLECULESMACROMOLECULES

Category Example Subunit(s)

Carbohydrates* Sugar Monosaccharide

Lipids Fats Glycerol and fatty acids

Proteins* Polypeptide Amino acids

Nucleic acids* DNA or RNA Nucleotide

Carbon is the Basic Element of Biomolecules

Organic Compounds and biomolecules

In the synthesis of a polymer, cells use enzymes to attach monomers to one another such as wagons to a train. This reaction is named dehydration as a molecule of water is freed.

Carbon is the Basic Element of Biomolecules

Organic Compounds and biomolecules

The opposite reaction is the degradation of a polymer. During this process, called hydrolysis, a molecule of water is used to separate the two molecules.

Almost all organisms use carbohydrates as sources of energy. In addition, some carbohydrates serve as structural materials.

Carbohydrates are molecules composed of Carbon (C), Hydrogen (H) and Oxygen (O). The ratio of hydrogen atoms to oxygen atoms is 2:1. In few words for every two H there is an atom of O.

Simple carbohydrates, commonly known as sugars, can be monosaccharides if they are composed of a single molecule, disaccharides if composed of two molecules, polysaccharides if they are composed of several monosaccharides.

CARBOHYDRATES

Sun light

6CO2 6H2O+ +C6H12O6 6O2

The most important carbohydrate is the glucose and is a monosaccharide with the molecular formula C6H12O6. Glucose is the final product of the photosynthesis and is metabolized by the animals to release its energy (during the respiration).

Photosynthesis reaction

WaterCarbon dioxide Glucose Oxygen

CARBOHYDRATES MONOSACCHARIDES

Glucose

There are 3 important disaccharides in living organisms.Maltose is a combination of two glucose units covalently linked.

Sucrose (also known as saccarose) is the common table sugar and is found in plants. It is formed by linking the two monosaccharides glucose and fructose.

Lactose is composed of glucose and another monosaccharide, the galactose. Lactose is a kind of sugar produced in the milk.

CARBOHYDRATES DISACCHARIDES

Sucrose

Glucose Fructose

Maltose

Glucose Glucose

Lactose

Glucose Galactose

Starches are among the most important polysaccharides. They represent a sugar reserve in plants and are composed of hundreds and hundreds molecules of glucose, linked to one another. Much of the world’s human population satisfies its energy needs with the starches contained in rice, wheat and potatoes.

Glycogen is the main sugar reserve in animals and as the starch is composed of hundreds molecules of glucose, but bonded in different ways.

Cellulose is used primarily as structural carbohydrate in plants (cell wall). It is composed of glucose units. The cellulose chain can be decomposed only by a few species of microorganisms. Wood is composed of dead cellulose (lignin). Cotton and paper are commercial products of cellulose.

Chitin is a substance consisting of polysaccharides as the cellulose and forming the major constituent in the exoskeleton of insects and the cell walls of fungi.

CARBOHYDRATES POLYSACCHARIDES

Monosaccharides(Cn(H2O)n)

Disaccharides Polysaccharides

Glucose: sugar with 6 atoms of Carbons (C6H12O6)

Sucrose: common table sugar, is composed of one molecule of glucose a n d o n e o f f r u c t o s e . I s t h e carbohydrate contained into plants.

Starch: supply sugar contained in plants

Fructose: sugar produced in fruits with similar formula as glucose

Lactose: composed of glucose and galactose, is the sugar contained in the milk

Cel lu lose : s t r uc tu re su g a r contained in plants

Glycogen: supply sugar contained in animals and fungi.

Chitin: structure sugar contained in some animals.

CARBOHYDRATES

Lipids are organic molecules composed of Carbon, Hydrogen and Oxygen with the ratio Hydrogen atoms to Oxygen much higher than in carbohydrates, (this is why lipids contains more energy than carbohydrates).

The most important molecules of lipids are the fats. Fats are composed of a glycerol molecule (that contains hydroxyl group -OH), and one, two or three units of fatty acid tales (a long chain of Carbon atoms with a carboxyl group -COOH)

LIPIDS

LIPIDS

A fat, or an oil, forms through the dehydration reaction of the functional groups of the glycerol (-OH) and the fatty acids (-COOH).

Lipids provide energy storage and protection and are insoluble in water as they are nonpolar molecules.

Some fatty acids have one or more double bonds in their molecules and are so called unsaturated fats.Other fatty acids have no double bond and are called saturated fats.

In most human health diets, the consumption of unsaturated fats is preferred to the saturated ones.Fats do not dissolve in water and are lighter than aqueous solutions. This is why fats as oil tend to lay on the surface of the water.Plants often store fats in their seeds, animals store fats in large, clear globules in the cells of adipose tissue. Lipids in adipose tissue contain much concentrated energy. Hence, they serve as a reserve energy supply to the organisms.

LIPIDS

LIPIDS

Phospholipids are a cell membrane component and are composed of two fatty acids bound to glycerol. A phosphate group replaces the third fatty acid.

Phosphate group is the hydrophilic (polar) “head” while the fatty acid chains are hydrophobic (nonpolar).The cell membrane is composed of a double layer of phospholipids.

LIPIDS

Steroids, as cholesterol, are lipids that serve as a cell membrane component but they also have a hormonal function (i.e. testosterone).

Waxe s a r e s o l i d at am b i e n t temperature and are insoluble in water.For their properties waxes are used to prevent water loss in plants and assist in skin and fur maintenance in animals.

PROTEINSAmong the most complex of all organic compounds, proteins are composed of amino acids.

Proteins are the most abundant and versatile biomolecules. Their functions in animals include:

1.Support: as keratin (in hair and fingernails) and collagen (in ligaments and tendons)

2.Metabolisms: as the enzymes (a particular enzyme catalyzes a specific reaction).

3.Transport: carrier proteins embedded in the plasma membrane allow substances to enter or exit cells

PROTEINS

Amino acids are molecules that contain Carbon, Hydrogen, Oxygen and Nitrogen atoms. Some amino acids also contain Sulfur atoms, Phosphorous or other trace elements as Iron and Copper.Many proteins are immense in size and extremely complex. However all proteins are composed of long chains of relatively simple amino acids.

There are 21 kinds of amino acids.Each amino acid (see on the left picture) has:an amino group (-NH2) a carboxyl group (-COOH) a group of atoms called -R group (radical group).

group -COOHgroup -NH2

group -R

PROTEINS

The 21 different amino acids differ depending on the nature of the -R group.

PROTEINS

Amino acids combine together to form proteins. Small proteins are often called peptides and are composed following 4 consecutive structures: Primary, Secondary, Tertiary and Quaternary.

All living things depend on proteins for their existences. Proteins are the major molecules from w h i c h t h e l i v i n g o r g a n i s m s a r e constructed.

NUCLEIC ACID

Every living species manufactures proteins unique to that species. The information for synthesizing the unique protein is located in the nucleus of the cell. The so-called genetic code (DNA) specifies the amino acid sequence in proteins trough a process called transcription

NUCLEIC ACIDSNucleic acids are biological molecules essential for life, and include DNA (deoxyribonucleic acid) and RNA (ribonucleic acid). Together with proteins, nucleic acids make up the most important and complex macromolecules. Found in abundance in all living things, they have function in encoding, transmitting and expressing genetic information.

Nucleic acids are now known to be found in all life forms, including bacteria, archaea, mitochondria, chloroplasts, viruses and viroids. All living cells and organelles contain both DNA and RNA, while viruses contain either DNA or RNA

The basic component of biological nucleic acids is the nucleotide.Nucleotides are composed of:a nucleobase (nitrogenous base): Purines and Pyrimidinesa five-C sugar (either ribose or 2'-deoxyribose, with formula)one to three phosphate groups.

Nucleotide structure

Phosphate group

Nucleobases

Sugar

NUCLEIC ACIDS

In DNA, the purine bases are adenine (A) and guanine (G), while the pyrimidines are thymine (T) and cytosine (C). RNA uses uracil (U) in place of thymine

NucleobasesLiving organisms have two important nucleic acids. One type is deoxyribonucleic acid (DNA), the other one is ribonucleic acid (RNA).

DNA is found primarily in the nucleus of cells, and is the deposit of the genetic information.

RNA is found in both nucleus and cytoplasm and is responsible, in eukaryotic cells, for transporting the genetic information.

NUCLEIC ACIDS