Chemistry and Biochemistry for MicrobiologyPart 2: Macromolecules

By BugLady

CarbonForms up to 4 bonds with other atoms and assembles into large molecules with carbon backbone

Carbon forms nonpolar and polar covalent bonds with other atoms.

oMolecules with nonpolar bonds (hydrocarbons) do not dissolve in water

oMolecules with polar bonds are more water soluble

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Organic Compounds

Organic compounds always contain carbon and hydrogen.

oWhat is CO2? And C6H12O6? What about CaCO3?

Inorganic compounds typically lack carbon.

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Organic CompoundsSmall organic molecules can combine into large macromolecules

Macromolecules are polymers consisting of many small repeating molecules

The smallest molecular unit is called a monomer

An oligomer contains 2-20 repeating units

Monomers join by dehydration (losing water molecules) synthesis or condensation (adding water molecules) reactions

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Proteins are polymers.

Carbohydrates

Consist of C, H, and O with the formula (CH2O)n

Energy sources: glucose, glycogen, starch

Structureo Nucleic acid component

o Cell walls in bacteria and plant cells

o Glycocalyx: slime layers and capsules

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NIH

Wikicommons

CDC

USDA

CarbohydratesOligosaccharides: 2 to 20 monosaccharides.

Polysaccharides: tens or hundreds of monosaccharides joined through dehydration synthesis.

Starch, glycogen, dextran, and cellulose are polymers of glucose.

Polysaccharides are insoluble in water.

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LipidsDefining feature: Insoluble in waterSmallest of the four macromoleculesCan be divided into two general classes

o Simple lipidso Compound lipids

Critical component of the cell membraneHeterogeneous group of molecules

oMade up of different subunits

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Triglycerides

Glycerol is esterified with three fatty acids. It is the main constituent of vegetable oil and animal fats.

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By Wolfgang Schaefer on Wikicommons

Steroids

Unlike other lipids, 4-ring structure

Cholesterol: plasma membrane of animal cells

Ergosterol: plasma membrane of fungi

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Ergosterol (NCBI PubChem)

PhospholipidsDerivative of triglyceride

Two fatty acid hydrophobic tails

One phosphate group

Amphipatic moleculesHead is hydrophilic

Tails are hydrophobic

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By Ties van Brussel Wikicommons

Proteins

Are essential in cell structure and function.

Enzymes are proteins that speed chemical reactions.

Transporter proteins move chemicals across membranes.

Flagella are made of proteins.

Some bacterial toxins are proteins.

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Amino Acid Subunits

There are 20 common amino acidsAll amino acids have

o A carboxyl group (COO-)

o An amino group (NH3+)

o A central carbono A side chain

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Biology.arizona.edu

Amino Acid SubunitsAll common amino acids are L optical isomersD isomers found in cell walls of prokaryotes

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RSC

Levels of Structure: The Primary Structure

Peptide bonds between amino acids are formed by dehydration synthesis.

The primary structure is the sequence of amino acids joined by peptide bonds

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Levels of Structure: The Secondary Structure

The secondary structure occurs when the amino acid chain folds and coils in a regular helix or pleats.

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Hydrogen bondsThese form in all proteins. The hydrogen atom of the peptide link is attracted to the oxygen of another peptide link.

C

NH

O

C

NH

O

peptide chains

RSC

Levels of Structure: The Tertiary Structure

The helix folds irregularly, forming disulfide bridges, hydrogen bonds, nonpolar interactions and ionic bonds between the side chains of amino acids.

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Covalent bondsIn a small number of proteins, sulfur-sulfur covalent bonds (also called cystine bonds or disulfide bridges) are present.

- CH2 – S – S – CH2 -

Ionic bondsIf some of the amino acids in the proteins have carboxylic acid or amine side groups, an ionic bond can form.

- COO- H3N+ - RSC

Protein StructureProteins have four structures

o Primaryo Secondaryo Tertiaryo Quaternary

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National Institute of General Medical Sciences

Protein Denaturation

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Denaturation: shape change causes protein to stop functioning

Can be reversible or irreversible

Heat, acids, bases, heavy metals, some organic solvents cause denaturation

Proteins must have a specific shape to have proper function

Check point

Which of the 4 protein structures is not affected by denaturation?

How is protein denaturation used in microbiology?

Sterilization and disinfection use chemical and physical methods that denature the proteins in microorganisms : heat, alcohol, aldehydes.

Primary Structure

Nucleic Acids

Polymers of nucleotides

Storage of genetic information

Processing of genetic informationApr 11, 2023 20

NHGRI

Deoxyribose (sugar)

Base pairing in DNAo A with T

o C with G

Information storage

Stability

National Institute of General Medical Sciences

DNA

RNAStructureo Usually single-strandedo Ribose (sugar)o A bonds with U and C bonds with G

Different types of RNA omessenger RNA (mRNA)o ribosomal RNA (rRNA)o transfer RNA (tRNA)o small RNAs involved in regulating gene expression.

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NHGRI

DNA vs. RNA

DNA RNA

Deoxyribonucleic acid Ribonucleic acid

Deoxyribose Ribose

Thymine (T) Uracil (U)

Adenine (A), guanine (G), cytosine (C) used in both

2 strands- double helix Single strand

1 form Several forms

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Adenosine Triphosphate

A special nucleotide

Energy currency for cell metabolism

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