Top Hat Biological Molecules

Introduction to Biomacromolecules

  • All living things are composed of cells; cells contain organelles, which are built from molecules.
  • Macromolecules are large molecules made of many subunits; they include nucleic acids, proteins, and carbohydrates.
  • Nucleic acids are composed of nucleotides and form genetic material DNA, located in the nucleus.
  • Proteins are composed of hundreds to thousands of amino acids; there are 20 different amino acids covalently linked by peptide bonds. Proteins function as enzymes and structural components of cells.
  • Carbohydrates (sugars) can be classified by the number of monomeric units:
    • Monosaccharide: contains one sugar unit.
    • Disaccharide: two monomer units linked by a glycosidic bond.
    • Polysaccharide: many monomer units linked together.
  • Lipids are large biological molecules that are not considered macromolecules in the same sense; they are composed of molecules such as triglycerides, phospholipids, waxes, and steroids. A triglyceride, for example, consists of a glycerol head connected to three fatty acid tails.
  • The glycerol head and three fatty acid tails structure a triglyceride: extTriglyceride=extglycerol+3imesextfattyacidsext{Triglyceride} = ext{glycerol} + 3 imes ext{fatty acids}
  • Real-world relevance: understanding these categories helps explain how cells store energy (carbohydrates and lipids), how information is stored (nucleic acids), and how functions are carried out (proteins).

Macromolecule Categories and Key Features

  • Nucleic acids
    • Made of nucleotide subunits; store and transmit genetic information (DNA).
    • DNA resides in the nucleus of cells.
  • Proteins
    • Built from amino acids (20 types).
    • Covalent linkage via peptide bonds.
    • Typical protein length is hundreds to thousands of amino acids.
    • Functions include catalysis (enzymes), structural roles, transport, signaling, etc.
  • Carbohydrates
    • Simple sugars (monosaccharides) can form larger carbohydrates.
    • Disaccharides formed by linking two monosaccharides via a glycosidic bond (e.g., sucrose, lactose).
    • Polysaccharides are long chains (starch, glycogen, cellulose).
  • Lipids
    • Not traditional macromolecules composed of repeating subunits.
    • Types include triglycerides, phospholipids, waxes, steroids.
    • Example: triglyceride structure with glycerol head and three fatty acid tails; not a macromolecule.

Materials and Reagents Used in the Experiment (Overview)

  • Meat extract: made by blending partially cooked hamburger meat; water added to achieve liquid consistency.
  • Potato extract: made by blending powdered potato; water added for liquid consistency.
  • Animal oil: beef fat cooked for several hours; kept warm to prevent solidification.
  • Additional samples listed (from the lab setup):
    • Onion juice (blended onions) mixed with water.
    • Starch solution (potato-based or prepared from starch powder).
    • Apple juice, sucrose solution (2%), cane sugar, sucrose, glucose solution (2%), dextrose.
    • Protein solutions: egg white albumin (protein), beef meat extract, beef water.
    • Lipid solutions: olive oil, animal oil (beef fat), beef tallow.
    • Carbohydrate/iodine reagents: iodine for starch; Benedict solution for reducing sugars.
    • Biuret reagents for protein testing (or alternatives using NaOH and CuSO4).
    • Testing materials: distilled water, whole milk, test tube rack, sharpie markers, transfer pipettes, glassware (borosilicate tubes), paper bibulous (bibulus) paper, foil, heat source (heat lamp), destaining tray, protective equipment as directed by instructor.
  • Reagents and indicators:
    • Iodine reagent for starch detection.
    • Benedict solution for reducing sugars.
    • Biuret reagent for protein detection (alternative: NaOH + CuSO4 when Biuret reagent unavailable).
    • Sudan IV reagent for lipid detection (red dye in ethanol).
  • Equipment and setup:
    • 11 test tubes labeled at the top.
    • Transfer pipettes; test tube rack; bibulous paper; large protective foil; heat lamp; destaining tray.
    • Temperature considerations: lipid samples may need warming to prevent solidification.

Experimental Setup and Procedure (Overview)

  • Center the workspace: arrange all sample containers in numerical order according to the chosen table for the experiment.
  • Prepare and organize materials to avoid spills and ensure clean transfers.
  • Perform three experiments, testing for two classes of biomolecules: proteins and lipids (with respective reagents).
Protein Testing: Biuret-Based Method
  • Targets: proteins and protein-containing molecules; examples include enzymes (e.g., amylase, pepsin), transport proteins (e.g., hemoglobin), albumin, and structural proteins (actin, myosin).
  • Setup:
    • Label 11 test tubes at the top (as indicated in the protocol).
    • Place in a test-tube rack in the order dictated by the provided table.
    • Into each test tube, add 1extmL1 ext{ mL} of the specified solution (per the table).
  • Reagent addition (to each test tube):
    • Add 55 drops of Biuret reagent to each tube. If Biuret reagent is not available, substitute with 2extmL2 ext{ mL} of NaOH and 55 drops of CuSO$_4$ (copper sulfate) solution, noting this provides the same basic Biuret-like reaction.
    • Do not add reagents to the sides of the glass; drop directly onto the sample.
    • Mix thoroughly after addition (demix thoroughly is likely a misprint for mix thoroughly).
  • Reaction and interpretation:
    • The reaction occurs immediately when proteins are present; a color change indicates a positive result for protein presence.
    • When color develops, the reaction is considered complete.
  • Data collection:
    • Record the observed color (and any other relevant characteristics such as turbidity or odor) for each tube.
Lipid Testing: Sudan IV Method
  • Target: presence of lipids (fats, oils, waxes, certain fat-soluble vitamins).
  • Reagent: Sudan IV (a nonpolar red dye) in ethanol; lipids (being nonpolar) mix with Sudan IV to produce a red stain.
  • Procedure, summarized (refer to steps A–J in the guide):
    • A) Gather a large piece of protective foil and place it at the workstation.
    • B) Place bibulous paper on the foil.
    • C) Number the bibulous paper evenly using a Sharpie to correspond to sample numbers.
    • D) Place a small drop of each testing solution onto the bibulous paper next to its corresponding number.
    • E) Position the bibulous paper under a heat lamp to dry for about ten minutes.
    • F) When instructed by the instructor, place the paper into the Sudan IV solution for staining (duration about five minutes).
    • G) Remove the paper from staining as directed after five minutes.
    • H) Place the stained bibulous paper in a destaining tray until instructed to remove.
    • I) Remove destained bibulous paper and place it on the large protective foil to dry for about five more minutes.
    • J) Record the results.
  • Interpretation:
    • Red stains on the bibulous paper indicate the presence of lipids.
  • Notes:
    • The testing materials are applied to highly absorbent bibulous paper to allow Sudan IV to adhere to lipids.
    • Ensure proper drying and avoid smearing the samples when reading results.

Experimental Controls: Positive and Negative Controls

  • Purpose: a valid experiment requires a control to compare results and to identify potential errors or external factors.
  • Positive control:
    • Demonstrates that the experimental system can produce a positive result under the right conditions.
    • Example (drug testing): testing for drug A (cocaine) in urine first, using a known positive sample, and observing its characteristic color, smell, temperature, turbidity, etc. to establish a reference.
    • If the positive control does not yield the expected result, the experiment is invalid because the system