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General Biology: Molecules of Cells

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  • What defines an organic compound in biology?
    An organic compound is a carbon-based molecule essential for life, capable of forming large complex structures.
  • How many bonds can a carbon atom form and why?
    Carbon has 4 valence electrons, allowing it to form up to 4 covalent bonds with other atoms.
  • What are isomers in organic chemistry?
    Isomers are molecules with the same chemical formula but different arrangements, affecting their properties and functions.
  • What are functional groups and their importance?
    Functional groups are specific chemical groups attached to carbon skeletons that affect molecule function by participating in chemical reactions.
  • What are macromolecules and how are they formed?
    Macromolecules are large molecules formed by joining smaller molecules called monomers into polymers via dehydration synthesis.
  • What is dehydration synthesis?
    A chemical reaction that joins two monomers by removing a water molecule (H₂O), forming a covalent bond.
  • What is hydrolysis in biological molecules?
    Hydrolysis is the process of breaking polymers into monomers by adding water, reversing dehydration synthesis.
  • What are monosaccharides and their role?
    Monosaccharides are simple sugar monomers like glucose, serving as the main fuel for cellular work and raw materials for other molecules.
  • How are disaccharides formed?
    Disaccharides form when two monosaccharides join via dehydration synthesis, e.g., maltose from two glucose units.
  • What functions do polysaccharides serve?
    Polysaccharides serve as energy storage (starch in plants, glycogen in animals) or structural components (cellulose, chitin).
  • What distinguishes starch and glycogen?
    Both are glucose polymers; starch stores energy in plants, while glycogen stores energy in animals.
  • What is cellulose and its biological role?
    Cellulose is a glucose polymer forming plant cell walls, providing structural support and is difficult to digest.
  • What are lipids and their key characteristics?
    Lipids are hydrophobic molecules mainly of carbon and hydrogen, important for long-term energy storage and cell membranes.
  • What are the three main types of lipids?
    Fats (triglycerides), phospholipids, and steroids are the three important lipid types.
  • What is the structure of a triglyceride?
    A triglyceride consists of one glycerol molecule linked to three fatty acids via dehydration reactions.
  • How do saturated and unsaturated fats differ?
    Saturated fats have no double bonds and are solid at room temperature; unsaturated fats have one or more double bonds causing kinks and are liquid.
  • What is the role of phospholipids in cells?
    Phospholipids form the cell membrane bilayer, with hydrophilic heads and hydrophobic tails creating a selective barrier.
  • What defines steroids structurally?
    Steroids have a carbon skeleton of four fused rings and include hormones like cholesterol, testosterone, and estradiol.
  • What are proteins and their general functions?
    Proteins are polymers of amino acids involved in catalysis, transport, defense, signaling, structure, and storage.
  • What determines a protein's function?
    A protein's function depends on its specific 3D shape, which is determined by its amino acid sequence.
  • What is a peptide bond?
    A peptide bond is a covalent bond formed between amino acids by a dehydration reaction linking the carboxyl group of one to the amino group of another.
  • What are the four levels of protein structure?
    Primary (amino acid sequence), secondary (alpha helices and beta sheets), tertiary (3D folding), and quaternary (multiple polypeptides).
  • What causes protein denaturation?
    Denaturation occurs when a protein loses its shape and function due to changes in pH, salt concentration, or heat.
  • What are nucleic acids and their types?
    Nucleic acids are polymers of nucleotides; DNA stores genetic information, and RNA helps synthesize proteins.
  • What are the components of a nucleotide?
    A nucleotide consists of a five-carbon sugar (ribose or deoxyribose), a phosphate group, and a nitrogenous base.
  • What nitrogenous bases are found in DNA and RNA?
    DNA has adenine (A), thymine (T), cytosine (C), guanine (G); RNA has adenine (A), uracil (U), cytosine (C), guanine (G).
  • How are DNA strands held together?
    DNA strands form a double helix held by hydrogen bonds between complementary base pairs: A pairs with T, C pairs with G.