Molecules of Life

Polymers Are Built of Monomers

• Organic molecules are formed by living organisms

– have a carbon-based core

– the core has attached groups of atoms called functional groups• the functional groups confer specific chemical

properties on the organic molecules

Polymers Are Built of Monomers

• The building materials of the body are known as macromolecules because they can be very large

• There are four types of macromolecules:1. Proteins2. Nucleic acids3. Carbohydrates4. Lipids

• Large macromolecules are actually assembled from many similar small components, called monomers– the assembled chain of monomers is known as a polymer

Macromolecule Formation

• There are 4 major categories of organic molecules in living organisms:– Carbohydrates– Lipids– Protein– Nucleic acids

Macromolecules

• A macromolecule is built upon repeating subunits called polymers.

• Macromolecules are large and complex.• An organic molecule is based on long

chains of carbon with functional groups on the ends that give the molecule its unique chemical properties.

Macromolecules

• All four macromolecules consist of a covalent bond between two subunits..a hydroxyl group is removed from one end and a hydrogen group from the other end.

• This process is called dehydration.• Dehydration requires the action of an enzyme

to facilitate chemical binding.• Adding of water to the polymer too break them

into subunits is called hydrolysis.

Carbohydrates

• Carbohydrates are energy sources and are made of polymers of simple carbohydrates. – Simple carbohydrates include monosaccharides and

disaccharides.– Complex carbohydrates are polysaccharides formed

from glucose.

• Component of plant cell walls, outer skeletons of insects.

• Ex.: chitin, cellulose, glycogen, starch.

Carbohydrates

• Carbohydrates are monomers that make up the structural framework of cells and play a critical role in energy storage

– a carbohydrate is any molecule that contains the elements C, H, and O in a 1:2:1 ratio

– the sizes of carbohydrates varies• simple carbohydrates – consist of one or two monomers• complex carbohydrates – are long polymers

Carbohydrates

• Simple carbohydrates are small

– monosaccharides consist of only one monomer subunit• an example is the sugar glucose (C6H12O6)

– disaccharides consist of two monosaccharides • an example is the sugar sucrose, which is formed by

joining together two monosaccharides, glucose and fructose

Formation of sucrose

Carbohydrates

• Complex carbohydrates are long polymer chains

– because they contain many C-H bonds, these carbohydrates are good for storing energy• these bond types are the ones most often

broken by organisms to obtain energy

– the long chains are called polysaccharides

Carbohydrates

• Plants and animals store energy in polysaccharide chains formed from glucose– plants form starch– animals form glycogen

• Some polysaccharides are structural and resistant to digestion by enzymes– plants form cellulose cell walls– some animals form chitin for exoskeletons

Carbohydrates and their function

Lipids

• Fats and all other biological materials that are not soluble in water, but are soluble in oil are lipids.

• Used for long term energy storage.• Fats:– Triglycerols are made of glycerol and three fatty

acids.– Fatty acids may be saturated or unsaturated with

hydrogen along the carbon chain.

Lipids

• Fats are used for:– Energy storage;– Components of cell membranes

(phospholipids);– Message transmission (steroids);– Pigmentation.

Lipids

• Fatty acids have different chemical properties due to the number of hydrogens that are attached to the non-carboxyl carbons

– if the maximum number of hydrogens are attached, then the fat is said to be saturated

– if there are fewer than the maximum attached, then the fat is said to be unsaturated

Saturated and unsaturated fats

Proteins

• Proteins may serve as enzymes, play a structural role, and act as chemical messengers.

• They are polypeptides made up of amino acids joined by peptide bonds.

• Act as catalysts.

The formation of a peptide bond

Proteins

• Protein structure:– The sequence of amino acids within the protein is

called the primary structure.– Any folding of the primary chain structure is called

the secondary structure.– Globular shapes are the tertiary structure of a

protein.– When more than one polypeptide chain composes

the protein, it has quaternary structure.– The shape of a protein can be denatured (poor

function results).

Proteins

• There are four general levels of protein structure

1. Primary

2. Secondary

3. Tertiary

4. Quaternary

Proteins

• Primary structure – the sequence of amino acids in the polypeptide chain

• This determines all other levels of protein structure

Figure 4.7 Levels of protein structure: primary structure

Proteins• Secondary structure forms

because regions of the polypeptide that are non-polar are forced together; hydrogen bonds can form between different parts of the chain

• The folded structure may resemble coils, helices, or sheets

Figure 4.7 Levels of protein structure: secondary structure

Proteins

• Tertiary structure – the final 3-D shape of the protein

• The final twists and folds that lead to this shape are the result of polarity differences in regions of the polypeptide

Insert Figure 4.7 from TLW 6e

Proteins

• Quaternary structure – the spatial arrangement of proteins comprised of more than one polypeptide chain

Figure 4.7 Levels of protein structure: quaternary structure

Protein

• The shape of a protein affects its function

– changes to the environment of the protein may cause it to unfold or denature

• increased temperature or lower pH affects hydrogen bonding, which is involved in the folding process

– a denatured protein is inactive

Nucleic Acids

• Nucleic acids (polynucleotides) store information for cells.

• DNA (Deoxyribonucleic acid) exists as a double helix of polynucleotides, using base pairing within the helix.– Base pairing dependent upon hydrogen bonding.– DNA encodes genetic materials and ribonucleic acid

(RNA) is involved in protein synthesis.

The Double Helix

• The reason for DNA to assume its double helix is because only two base pairs are possible: Adenine-Thymine and Guanine-Cytosine.

• The advantage of the double helix is that it contains two copies of the information—one the mirror image of the other.

The DNA double helix