chapter 2b

BRAZOSPORT COLLEGE - BIOL 2301 ANATOMY & PHYSIOLOGY I: CHEMISTRY COMES ALIVE (BIOCHEMISTRY)

OVERVIEW OF BIOCHEMISTRY

  • Key components of biochemistry include:
      A. Carbohydrates
      B. Lipids
      C. Proteins
      D. Nucleic Acids: DNA & RNA
      E. Adenosine Triphosphate (ATP)

LIVING ORGANISMS AND ORGANIC COMPOUNDS

  • Living organisms primarily consist of carbon-based compounds.
      - Carbon:
        - Unique property of forming covalent bonds with up to four other atoms.
        - Acts as a “backbone” for many large molecules.
        - Allows formation of a wide variety of molecules =
          - Variation in carbon chain lengths
          - Combination of other atoms: Carbon (C), Oxygen (O), Nitrogen (N), Sulfur (S), Phosphorus (P), and Hydrogen (H).
  • Major classes of organic compounds =
      - Carbohydrates, Lipids, Proteins, Nucleic Acids, serving various essential functions in the cell.

FORMATION AND BREAKDOWN OF MACROMOLECULES

  • Anabolism (Building up):
      - Formation of large molecules by linking small subunits.
      - Reaction involves
        - Combining the hydrogen from one group with the hydroxyl (-OH) from another.
      - Monomers form polymers:
        - Polymer: A large molecule made up of repeated similar units (monomers).
        - Analogy: Pearls on a string or railroad cars linked together.
        - Monomer: Small, similar chemical subunits.

  • Catabolism (Breaking down):
      - Reverse of dehydration synthesis, this involves the breakdown of polymers into monomers.
      - One part gains hydrogen (-H) while the other gains a hydroxyl (-OH).

CARBOHYDRATES

  • Definition: Molecules composed of carbon (carbo-) and water (-hydrate).
  • Very polar due to O-H bonds.
  • Covalent bonds of Carbon-Hydrogen (C–H) hold much energy, making it suitable for energy storage.
  • Types of Carbohydrates:
      - Monosaccharides (Simple Sugars):
        - Comprise as few as three to as many as seven carbons.
        - The most essential in humans are those with six carbons (e.g., Glucose, Fructose, Galactose).
        - Isomers: Same molecular formula but different 3D structures.
        - Examples:
          1. Glucose: Blood sugar, major nutrient for cells.
          2. Important 5-carbon monosaccharides include Ribose and Deoxyribose, crucial for RNA and DNA structure.
      - Disaccharides:
        - Consist of two monosaccharides linked together via dehydration synthesis.
        - Too large to pass through cell membranes, serve sugar transport roles.
        - Examples:
          1. Sucrose: Glucose + Fructose
          2. Lactose: Glucose + Galactose
          3. Maltose: 2 Glucose
      - Polysaccharides:
        - Composed of multiple monosaccharide units. Formed through dehydration synthesis.
        - Typically less soluble in water.
        - Types:
          1. Glycogen: Animal starch used for energy storage in animal tissues (skeletal muscles and liver).
          2. Starch: Plant energy storage.
          3. Cellulose: Plant structural component, indigestible by humans, forms dietary bulk.

LIPIDS

  • Definition: Hydrophobic molecules that form fats and membranes.
  • Major components include carbon (C), hydrogen (H), oxygen (O), with minor components like phosphorus (P) and nitrogen (N).
  • Unlike carbohydrates, lipids have lower oxygen to carbon ratios, making them less polar and often insoluble in water.
  • Major Classes of Lipids:
      A. Triglycerides (Neutral Fats)
      B. Phospholipids
      C. Steroids
      D. Eicosanoids

FUNCTIONS OF LIPIDS

  • Primary functions include:
      A. Protection: Surround and protect organs.
      B. Insulation: Fat under the skin prevents heat loss and myelin sheaths insulate neuronal axons.
      C. Hormonal Regulation: Steroid hormones regulate physiological processes.
      D. Nutritional Role: Fat-soluble vitamins (e.g., A, D, E, K) are involved in various body functions.
      E. Membrane Structure: Phospholipids and cholesterol are critical for cell membrane structure.
      F. Energy Storage: Provide more energy on breakdown compared to carbohydrates or proteins.

CLASSIFICATION OF FATS

  • Saturated Fats:
      - Higher melting point, primarily of animal origin, solid at room temperature (examples: animal fats, butter).
  • Unsaturated Fats:
      - Have one or more double bonds causing kinks, preventing tight packing.
      - Lower melting point, usually liquid at room temperature, of plant origin (e.g., olive oil is monounsaturated; canola oil is polyunsaturated).

HEALTH IMPLICATIONS OF FATS

  • Trans Fats: Artificially created through hydrogenation, can elevate low-density lipoprotein (LDL) levels leading to heart disease risks.
  • Omega Fatty Acids: Essential fatty acids obtained through diet — examples include Omega-3 and Omega-6 fatty acids found in salmon, flaxseed, avocado, etc.

PHOSPHOLIPIDS

  • Composed of glycerol, 2 fatty acids, and a phosphorus-containing group.
  • Have a polar (hydrophilic) head and non-polar (hydrophobic) tails.
  • Fundamental for the structure of cell membranes.

PROTEINS

  • Most abundant organic molecules with diverse functions.
  • Major components: C, H, O, N; minor components include S, P, Fe, I.
  • Functionality of proteins includes:
      1. Structural Support: Collagen in connective tissues, keratin in hair/skin/nails.
      2. Muscle Contraction: Actin and myosin proteins facilitate muscle movement.
      3. Enzymatic Function: Enzymes speed up biochemical reactions.
      4. Transport: Proteins assist in the movement of substances in and out of cells.
      5. Regulation: Enzymes catalyze reactions, hormones regulate physiological activities.
      6. Immune Defense: Antibodies provide protection against pathogens.
      7. Chaperones: Assist in proper protein folding.

AMINO ACIDS

  • Building Blocks of Proteins:
      - Composed of a central carbon, an amine group, and a carboxyl group.
      - Variability in R-group leads to different amino acids.
      - Peptide bonds formed between amine and carboxyl groups link amino acids, leading to polypeptide formation.

PROTEIN DENATURATION

  • Environmental changes may cause loss of protein structure (2° to 4° structural levels).
      - Denaturation can unfold proteins into a linear chain (1° structure) and potentially lead to irreversible damage, including cell death.
  • Digestive enzymes function under highly acidic conditions (pH 2).
  • Fibrous proteins demonstrate more stability than globular proteins.

ENZYMES

  • Definition: Type of globular proteins that act as biological catalysts by lowering activation energy needed for reactions.
  • Activation Energy: The minimum energy required for reactants to initiate a chemical reaction.

NUCLEIC ACIDS

  • Definition: Largest molecules in the body, functioning to store and transmit genetic information.
  • Major components: C, H, O, N, P; minor components include S, P, Fe, I.
  • Made up of polymers of monomers called nucleotides, each consisting of a nitrogen base, pentose sugar, and phosphate group.
  • Major classes:
      - DNA (Deoxyribonucleic Acid):
        - Double-stranded structure resembling a twisted ladder.
        - Nucleotides held together via covalent bonds vertically and hydrogen bonds horizontally between nitrogenous bases.
        - Directionality: 5’ to 3’ on one strand and 3’ to 5’ on the opposite strand.
        - Gene: A sequence of DNA that directs the synthesis of an RNA molecule for protein production.
      - RNA (Ribonucleic Acid):
        - Single-stranded and contains ribose sugar with uracil instead of thymine.
        - Types of RNA include:
          1. mRNA: Messenger RNA, carries genetic information for protein synthesis.
          2. tRNA: Transfer RNA, aids in the translation of mRNA into proteins.
          3. rRNA: Ribosomal RNA, component of ribosomes where protein synthesis occurs.

COMPARISON OF DNA AND RNA (TABLE 2.5)

  • | Characteristic | DNA | RNA |
      -|-----------------------|-----------------------------------------|----------------------------------------|
      -| Major cellular site | Nucleus | Cytoplasm |
      -| Major functions | Genetic material; directs protein synthesis; replicates before cell division | Carries out genetic instructions for protein synthesis |
      -| Structure | Double strand, coiled into a double helix | Single strand, straight or folded |
      -| Sugar | Deoxyribose | Ribose |
      -| Bases | Adenine (A), Guanine (G), Cytosine (C), Thymine (T) | Adenine (A), Guanine (G), Cytosine (C), Uracil (U) |

ADENOSINE TRIPHOSPHATE (ATP)

  • Definition: Molecule that stores and provides energy for all living organisms derived from glucose breakdown.
  • Powers chemical reactions within cells; provides immediate usable energy required for cellular processes.
  • The potential energy is stored in the phosphate group's bond, particularly in the third phosphate group.
  • ATP is often referred to as "Energy Currency" of the cell.