Microbiology Lecture 3: Chemical Principles

Microbiology Lecture 3: Chemical Principles and Biochem

• This lecture covers chemical principles and biochemistry relevant to microbiology.
• Chapter 2 of the Microbiology textbook (pages 25-35) provides a review of chemical principles.
• This review is useful background information for understanding the chemical basis of biological processes.
• Atoms are the fundamental building blocks of matter.
• Chemical elements are substances composed of atoms of a single type.
• Chemical bonds hold atoms together in molecules. These include ionic bonds, covalent bonds, and hydrogen bonds.
• Chemical reactions involve the breaking and forming of chemical bonds. These reactions can be synthesis (anabolism) or decomposition (catabolism) reactions.
• Important inorganic compounds in cells include water, acids, bases, and salts.
• Organic compounds contain carbon and hydrogen; this is in contrast to inorganic compounds which typically lack carbon. Examples of organic compounds include carbohydrates, lipids, proteins, and nucleic acids.

Important Biological Molecules

• Organic compounds: contain both carbon and hydrogen
• CO2 is usually categorized as inorganic, even though it contains carbon.
• Inorganic compounds typically lack carbon.

Bacterial Cell

• Students will learn about the macromolecules necessary for building a bacterial cell.
• The lecture discusses the cell wall, cell membrane, cytoplasm, and genetic material of a bacterial cell
• The specific organic macromolecules involved in bacterial cell structure and function are further explored.
• The difference is highlighted between eukaryotic and prokaryotic cells through understanding the organic macromolecules that compose them.

Composition of an E. coli Cell

• This table provides data on the composition of an E. coli cell by weight percentage, average molecular weight, and number per cell for each of various components.
  • Water is the most abundant component (70% by weight).
  • Proteins comprise 15% of the cell by weight.
  • Nucleic acids, including DNA and RNA types, make up about 1% of the cell weight, on average

Carbohydrates

• Carbohydrates are important for structural support and energy storage.
• Carbohydrates are made up of carbon, hydrogen, and oxygen. The general formula is (CH₂O)n.
• Monosaccharides are the simplest carbohydrates. These include hexoses (e.g., glucose and fructose) and pentoses.
• Glucose is a common hexose.
• Disaccharides are formed when two monosaccharides combine through dehydration synthesis
• Hydrolysis is the breakdown of disaccharides.
• Oligosaccharides contain 2 to 20 monosaccharides.
• Polysaccharides contain tens or hundreds of monosaccharides linked together.
• Examples include starch, glycogen, dextran, and cellulose
• Chitin is a polymer of two repeating sugars.
• Polysaccharides have a variety of functions, such as energy storage (starch and glycogen) and structural support (cellulose, chitin, peptidoglycan).

Functions of Polysaccharides

• Storage molecules: starch and glycogen
• Structural molecules: cellulose, chitin, peptidoglycans (murein)
• Lubrication: hyaluronic acid (component of extracellular matrix)

Lipids

• Lipids are primary components of cell membranes.
• Lipids are made up of carbon, hydrogen, and oxygen.
• Lipids serve as fuel storage in fat tissue.
• Lipids include vitamins and hormones.
• Lipids are "nonpolar" and insoluble in water.

Simple Lipids

• Called fats or triglycerides
• Contain glycerol and fatty acids
• Formed by dehydration synthesis
• Types of fatty acids: saturated and unsaturated
• Saturated fats have no double bonds in their fatty acids;
• Unsaturated fats have one or more double bonds in their fatty acids and can be cis or trans isomers.

Complex Lipids

• Contain C, H, O, P, N, or S
• Cell membranes are predominantly made of phospholipids.
• Phospholipids have a polar (hydrophilic) head and nonpolar (hydrophobic) tails.
• The structure and properties of phospholipids are important for their role in membranes.

Steroids

• Consist of four fused carbon rings.
• Function as components of cell membranes.

Proteins

• Proteins are made up of amino acids linked together by peptide bonds.
• Amino acids contain an amino group (-NH₂), a carboxyl group (-COOH), and a side chain (R group).
• There are 20 different amino acids.
• Proteins exist as linear polymers.
• Proteins can have different conformations (native shapes)
• Proteins have diverse roles in cells; including structural components, enzymes, and transport proteins.
• Enzymes are proteins that speed up chemical reactions in cells.
• Some bacterial toxins are also proteins.
• Protein structure is described through the concepts of primary, secondary, tertiary, and quaternary structure levels.

Levels of Protein Structure

• Primary structure: linear sequence of amino acids
• Secondary structure: localized folding (alpha helices and beta sheets)
• Tertiary structure: overall 3D shape of a polypeptide chain
• Quaternary structure: interactions between multiple polypeptide chains.
• Protein denaturation describes the loss of the secondary and tertiary structures due to factors like changes in temperature or pH.

Conjugated Proteins

• Conjugated proteins are composed of amino acids and additional organic molecules.
• Examples include glycoproteins, nucleoproteins, and lipoproteins.

Nucleic Acids

• Mononucleotides (eg., AMP, ADP, ATP) function as energy sources and enzyme cofactors (e.g., NAD & FAD).
• Nucleic acids (DNA and RNA) are essential for genetic information.
• DNA is the genetic material
• RNA has multiple roles (structural, enzymatic, informational).
• Nucleic acids contain nucleotides, pentose sugars, phosphate groups, and nitrogen-containing bases.

DNA (Deoxyribonucleic acid)

• DNA is a double helix.
• DNA has deoxyribose sugar.
• DNA has A (adenine), T (thymine), G (guanine), and C (cytosine) bases
• The order of the bases carries genetic information.

RNA (Ribonucleic acid)

• RNA is typically single-stranded.
• RNA has ribose sugar.
• RNA has A (adenine), U (uracil), G (guanine), and C (cytosine) bases
• RNA has various roles in the cell.

ATP (Adenosine Triphosphate)

• ATP stores chemical energy.
• ATP releases energy when phosphate groups are removed through hydrolysis.
• ATP is made via dehydration synthesis.
• Essential for cellular processes.

This lecture focuses on the essential chemical principles and biochemistry pertinent to microbiology. Chapter 2 of the Microbiology textbook provides critical insights into atoms, chemical bonds, and reactions, offering a foundation for understanding biological processes. Learn about the significance of both inorganic and organic compounds within cellular contexts.