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General Biology: Structure and Function of Large Biological Molecules

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  • What is a polymer in biological molecules?

    A polymer is a long molecule made of many similar or identical building blocks called monomers. Carbohydrates, proteins, and nucleic acids are biological polymers.

  • What are dehydration and hydrolysis reactions in polymer metabolism?

    Dehydration reactions build polymers by removing water to form bonds; hydrolysis breaks polymers by adding water to break bonds.

  • How does a small set of monomers create biological diversity?

    A limited set of monomers can be arranged in countless ways to form diverse polymers, similar to how 26 letters create infinite words.

  • What is the general formula for carbohydrates?

    Carbohydrates have a formula roughly \((CH_2O)_n\), with a carbon:hydrogen:oxygen ratio of about 1:2:1.

  • What are monosaccharides and their role?

    Monosaccharides are simple sugars like glucose that serve as major fuel and raw materials for building larger carbohydrates.

  • What is a glycosidic linkage?

    A glycosidic linkage is a covalent bond formed between two monosaccharides during dehydration synthesis to create disaccharides or polysaccharides.

  • How do plants and animals store excess glucose?

    Plants store glucose as starch (helical polymer), animals store it as glycogen (extensively branched polymer) for energy reserves.

  • Why can't humans digest cellulose?

    Cellulose has β-glycosidic linkages forming rigid microfibrils; most animal enzymes cannot hydrolyze these β bonds, so cellulose passes as fiber.

  • What structural difference distinguishes starch from cellulose?

    Starch has α-1,4 glycosidic linkages causing a helical shape; cellulose has β-1,4 linkages forming straight, rigid chains.

  • What is chitin and its biological role?

    Chitin is a structural polysaccharide with nitrogen-containing groups, forming the exoskeleton of arthropods and fungal cell walls.

  • How does branching in glycogen benefit animals?

    Branching in glycogen allows rapid release of glucose during high energy demand due to many accessible chain ends.

  • What is the amphipathic nature of phospholipids?

    Phospholipids have hydrophilic (polar) heads and hydrophobic (nonpolar) tails, driving spontaneous bilayer formation in water.

  • How do saturated and unsaturated fatty acids differ structurally and physically?

    Saturated fatty acids have no double bonds, straight chains, pack tightly, solid at room temp; unsaturated have cis double bonds causing kinks, preventing tight packing, liquid at room temp.

  • What is the function of triacylglycerols (fats)?

    Triacylglycerols store concentrated long-term energy by linking three fatty acids to glycerol via ester linkages.

  • What is the structural framework of steroids like cholesterol?

    Steroids have a rigid carbon skeleton of four fused rings; cholesterol regulates membrane fluidity and is a precursor for hormones.

  • How do LDL and HDL lipoproteins differ in cholesterol transport?

    LDL transports cholesterol to tissues and can cause plaque buildup (bad); HDL removes excess cholesterol for excretion (good).

  • What determines the primary structure of a protein?

    The primary structure is the linear sequence of amino acids dictated by genetic information.

  • What are the secondary structures of proteins?

    Secondary structure includes α-helices and β-pleated sheets formed by hydrogen bonds along the polypeptide backbone.

  • What stabilizes the tertiary structure of proteins?

    Tertiary structure is stabilized by interactions between R groups: hydrophobic interactions, ionic bonds, hydrogen bonds, and disulfide bridges.

  • What is quaternary protein structure?

    Quaternary structure arises when multiple polypeptide subunits assemble into a functional protein complex.