Lesson 3: Introduction to biological macromolecules

• cations - positive ions formed by losing electrons
• anions - negative ions formed by electron gain
• anions are named using the ending -ide
• electron transfer - when one atom loses an electron and another atom gains that electron
• ionic bonds - bonds formed between ions with opposite charges
• electrolytes - ions that are necessary for nerve impulse conduction, muscle contractions, and water balance (e.g. sodium, potassium, calcium)
• covalent bonds - bonds between atoms in which involves electron sharing
• nonpolar covalent bond - form between two atoms of the same element, or between atoms of different elements that share electrons more or less equally. e.g. O2, CH4
• polar covalent bond - bond wherein electrons are unequally shared by the atoms and spend more time close to one atom than the other. thus, slightly positive (δ+) and slightly negative (δ–) charges develop in different parts of the molecule. e.g. H2O
• Identify the bond type and the corresponding molecular shape.

  A) polar covalent

  B) bent

  C) nonpolar covalent

  D) tetrahedral

  
• Two types of weak bonds:

  • hydrogen bonds
  • london dispersion forces
• van der waals : weak electrostatic forces that attract neutral molecules to one another and do not involve covalent bonds or ions
• hydrogen bond - a polar covalent bonding containing hydrogen, wherein the hydrogen is δ+ because a more electronegative element is pulling away its electron. e.g. O-H in water molecules
• individual hydrogen bonds are weak, but many hydrogen bonds together can be strong
• london dispersion forces - weakest intermolecular force/weak attractions between molecules, but unlike hydrogen bonds, it can occur between two adjacent atoms or molecules of any kind forming temporary dipoles
• Identify the corresponding type, electronegativity difference, and species

  A) transfer

  B) sharing

  C) >1.7

  D) <1.7

  E) ions

  F) molecules

  
• Identify the types of bond

  A) nonpolar covalent bond

  B) polar covalent bond

  C) ionic bond

  
• ionic bonds - electron transfer between ions (cation + anion) with large electronegativity difference. e.g. Alkali (1ve-) & Halogens (7ve-). Na1+Cl1-
• ions - charge particles by losing or gaining electrons resulting unequal number of protons & electrons
• covalent bonds involve electron sharing by one, two, or three electrons forming single, double, & triple bonds, respectively
• Identify the types of intermolecular force/bonds

  A) van der waals

  B) hydrogen bonds

  C) london dispersion forces

  
• ROLES OF CHEMICAL BONDS IN THE CELL

  • Strong covalent bonds - hold together the chemical building blocks of DNA strand
  • Weaker hydrogen bonds - hold together the two DNA strands of the double helix; making it stable but still allows opening for copying & used by the cell
• Four major types of large biological molecules/macromolecules:

  1. carbohydrates
  2. lipids
  3. proteins
  4. nucleic acids
• • macromolecules - make up majority of the cell dry weight
  • water - makes up majority of the wet weight
• macromolecules - large, organic molecule such as carbohydrates, lipids, protein, and nucleic acids
• monomer - building block for larger molecules
• polymer - large molecule made of repeating subunits
• lipids - not usually polymers and are smaller than the other three, so they are not considered macromolecules by some sources 
• Identify the corresponding building blocks of the following biological macromolecules

  A) monosaccharides

  B) fatty acids and glycerol

  C) amino acids

  D) nucleotides

  
• carbohydrates - store fuel for future energy needs; provide cells with quick/short-term energy, source of dietary fiber. e.g. glucose, sucrose, starch, cellulose, chitin
• lipids - key structural components of cell membranes; provide cells with long-term energy. e.g. fats, phospholipids, waxes, oils, grease, steroids
• proteins - broadest range of functions: structural support, catalyzing metabolic reactions, receiving & transmitting chemical signals. e.g. keratin, hormones, enzymes, antibodies, insulin, hemoglobin, keratin
• nucleic acids - store and transfer hereditary/genetic information. e.g. DNA, RNA
• Reactions that assemble monomers into polymers, wherein monomer forms a covalent bond to another monomer, releasing water molecule

  A) dehydration synthesis

  
• Reactions that turn back polymers into monomers by bond breaking thru the addition of water molecule

  A) hydrolysis

  
• OVERALL: dehydration synthesis build molecules, use energy, and release water, while hydrolysis breakdown molecules, release energy, and use water.
• enzymes - catalyze/speed up both dehydration synthesis & hydrolysis rxns
• enzyme involved in forming bonds are called -ase (suffix)