MIC 205 - Microbiology Review Atoms, Bonds, and Biological Molecules PDF

MIC 205 - Microbiology Lecture: Atoms, Bonds, and Biological Molecules Ch. 2 The Chemistry of Microbiology These are review materials that are contain in Chapter 2. While this chapter will not be covered during a lecture please understand that the information of this chapter is a prerequisite for...

MIC 205 - Microbiology Lecture: Atoms, Bonds, and Biological Molecules Ch. 2 The Chemistry of Microbiology These are review materials that are contain in Chapter 2. While this chapter will not be covered during a lecture please understand that the information of this chapter is a prerequisite for this course, and therefore your understanding of this chapter is necessary for success in this course and will be fair game on exams. The Atom Matter is composed of very small units called atoms This line (about 3 centimeters) is the same length as 100 million carbon atoms lined up end to end! Atoms are composed of three “subatomic particles” called protons, neutrons, and electrons Protons and neutrons are in the center, or nucleus; electrons are around the outside nucleus MIC 205 – Lisenbee (31-Aug-13) 2 The Role of Electrons An atom’s electrons are involved in combining the atom with other atoms to form chemical bonds – Atoms may share or exchange electrons when they get close to each other – Chemical bonds move atoms to lower, stable energy states – Three types of bonds Ionic bonds Covalent bonds (nonpolar and polar) Hydrogen bonds Electrons hang out in well-defined “energy levels” or “energy shells” around the nucleus Atoms are most stable when their outermost energy shells are completely filled 3 1  4 Ionic Bonds Some atoms are made more stable by exchanging electrons with other atoms to form ions – Cations – – Anions – Cations and anions attract each other to form ionic bonds without sharing electrons Compounds are formed when many positive and negative ions interact – Typically form crystalline compounds known as salts that dissociate in water into their component cations and anions (electrolytes) – Allows for formation of electrical gradients across membranes – Dissociation of hydrogen ions determines cellular pH 5 6 2 Covalent Bonds Some atoms prefer to share electrons with other atoms rather than exchange them The sharing of one or more pairs of electrons between two atoms is called a covalent bond Electronegativity – the relative attraction of an atom for its electrons – The more electronegative an atom, the greater the pull its nucleus exerts on electrons – Determines whether bond will be nonpolar or polar The joining of two or more atoms with covalent bonds forms a molecule 7 Nonpolar Covalent Bonds Atoms with similar electronegativities Shared electrons spend equal amount of time around each nucleus; charged poles do not develop Carbon atoms form four nonpolar covalent bonds with other atoms; critical property for life 8 Polar Covalent Bonds Unequal sharing of electrons due to significantly different electronegativities Most important polar covalent bonds involve hydrogen and oxygen Critically important for establishing the weakly polarized conditions necessary for hydrogen bonding 9 3 Hydrogen Bonds Weak electrical attractions between opposite partial charges of molecules exhibiting polar covalent bonds Weaker than covalent bonds but absolutely essential for living organisms – Determine the physical properties of water, our planet’s universal solvent – Help stabilize the three- dimensional shapes of large molecules – Dictate the interactions of enzymes with substrates, antibodies with targets, etc. 10 Chemical Reactions The making or breaking of chemical bonds Involve reactants and products Three categories of chemical reactions – Synthesis reactions – Decomposition reactions – Exchange reactions 11 Reduction and Oxidation Reactions (REDOX) Cells make ATP by first releasing energy in the form of electrons from organic and inorganic compounds (electron donors) O oxidation I involves L loss of electrons R reduction I involves G gain of electrons These reactions are always coupled/ occur simultaneously Cells use electron carrier molecules to carry electrons 12 4 Organic Macromolecules Large, carbon-containing molecules; carbon and other atoms are combined into certain patterns that lead to specific arrangements of functional groups Four main classes... – Lipids – Carbohydrates – Proteins I should remember – Nucleic Acids this stuff!!! Each of the four main classes is composed of specific monomers (basic building blocks of macro- molecules) 13 Lipids Most lipids are composed of fatty acid monomers that contain mostly carbon and hydrogen Fatty acids are nonpolar, but may be functionalized with other molecules to add special properties Four groups... – Fats – Phospholipids – Waxes – Steroids 14 Fats 15 5 Phospholipids 16 Lipid Bilayer Membrane Structure 17 Waxes and Steroids Waxes – Contain one long-chain fatty acid covalently linked to long- chain alcohol by ester bond – Completely insoluble in water; lack hydrophilic head Steroids – Complex hydrocarbons based upon a sterol ring – not composed of fatty acid monomers – Unique component of eukaryotic cell membranes that changes membrane fluidity (cholesterol) – Important signaling molecules (hormones) 18 6 Carbohydrates Organic molecules composed of carbon, hydrogen, and oxygen (CH2O)n Functions – Long-term storage of chemical energy – Ready energy source – Part of backbones of nucleic acids – Converted to amino acids – Form cell wall – Involved in intracellular interactions between animal cells Types – Monosaccharides – Disaccharides – Polysaccharides 19 Monosaccharides Glucose 20 Monosaccharides Glucose Fructose 21 7 Monosaccharides Glucose N-acetylglucosamine (NAG) 22 Disaccharides 23 Polysaccharides 24 8 Polysaccharides 25 Gram+ Cell Wall and Membrane 26 Gram- Cell Wall and Membranes 27 9 Proteins Chains of amino acid monomers composed of carbon, hydrogen, oxygen, nitrogen, and sulfur Cellular workhorses that perform a variety of essential functions... – Maintain cell and organelle structure – Catalyze enzymatic reactions – Regulate cellular processes – Transport metabolites, ions, etc. – Defend against pathogens 28 Amino Acids The monomers that make up proteins Most organisms use only 21 amino acids to build proteins Amino acid side groups (R) determine the chemical properties of the peptide or protein Peptide bond – covalent bond formed between amino acids 29 Protein Structure 30 10 Protein Structure 31 Nucleic Acids DNA and RNA vital as genetic material of organisms and viruses – Carries instructions for synthesis of RNA and proteins – Controls synthesis of all molecules in an organism RNA helps form polypeptides 32 Nucleotides Nucleotides are the monomers that make up DNA and RNA nucleic acids Composed of three parts – Cyclic nitrogenous base Adenine (A) Guanine (G) 5 Cytosine (C) 1 4 Thymine (T) 2 3 Uracil (U) – Pentose sugar – deoxyribose or ribose – Phosphate group(s) 33 11 Nucleic Acid Structure H bonds form between C and G and between T and A in DNA – U and A in RNA DNA is double stranded in most cells and viruses – Two strands are complementary – Two strands are antiparallel 5’ – C C A T G G – 3’ complementary 3’ – G G T A C C – 5’ 5’ – C C A T G G – 3’ antiparallel 3’ – G G T A C C – 5’ 34 Nucleic Acid Structure 35 12