Cell Composition and Organic Molecules Quiz

Cell Composition

• Cells are composed of water (70%), inorganic ions, and organic molecules.
• Water is the most abundant component serving as a universal solvent and playing a crucial role in chemical reactions.
• Inorganic ions, present in small quantities (<1% of cell mass), are vital for various cellular functions and metabolism.
• Organic molecules are macromolecules essential for biological processes that sustain life.

Organic Molecules

• The four main types of organic molecules are:
  • Proteins: Polymers created by joining amino acids through peptide bonds.
  • Carbohydrates: Polymers of sugars like glucose, fructose, and galactose.
  • Lipids: Fats, oils, and waxes primarily composed of carbon and hydrogen.
  • Nucleic Acids: Polymers made of nucleotides that carry genetic information (DNA and RNA).

Dehydration and Hydrolysis

• Dehydration is a chemical reaction that joins two monomers to form a polymer by releasing a water molecule.
• Hydrolysis is the opposite of dehydration, where a polymer is broken down into monomers by adding a water molecule.

Proteins

• Proteins are polymers of 20 distinct amino acids, each with a specific side chain that contributes to their structure and function.
• Proteins are essential for a wide range of cellular functions.
• Functional Proteins: These proteins perform specialized tasks like:
  • Antibodies: Combating disease-causing pathogens as part of the immune response.
  • Enzymes: Catalyzing biological reactions (e.g., amylase, lipase, pepsin).
• Transport Proteins: These proteins facilitate the movement of substances within the cell and body:
  • Hemoglobin : Transporting oxygen throughout the body.
  • Albumin: Transporting fatty acids in the blood.
• Regulatory Proteins: These proteins control cellular metabolism, such as:
  • Insulin: Regulating blood glucose levels.
• Structural Proteins: These proteins provide support and structure to cells and organisms:
  • Keratin: Found in hair and nails.
  • Myosin: Found in muscle tissue.

Testing for Proteins

• Biuret test:
  • Uses a blue reagent containing copper sulfate (CuSO4) and sodium hydroxide (NaOH).
  • Produces a purple color in the presence of proteins.

Carbohydrates

• Carbohydrates include simple sugars (monosaccharides) and complex sugars (polysaccharides).
• Monosaccharides:
  • Glucose, fructose, and galactose are essential cellular nutrients.
• Disaccharides: Form when two monosaccharides join through a glycosidic bond.
  • Maltose: Glucose + Glucose
  • Lactose: Galactose + Glucose
  • Sucrose: Fructose + Glucose
• Polysaccharides: Formed by linking chains of glucose units.
  • Starch: Plants store glucose as starch.
  • Glycogen: Animals store glucose as glycogen.
  • Cellulose: The primary component of plant cell walls.

Testing for Starch or Glycogen

• Iodine Test:
  • Uses a brown iodine solution.
  • Turns a deep purple to black in the presence of starch.

Testing for Glucose

• Benedict test:
  • Uses a blue Benedict reagent containing sodium carbonate (Na2CO3), sodium citrate, and copper(II) sulfate (CuSO4).
  • The color change after heating a solution containing glucose depends on the glucose concentration:
    • Green: Very low concentration.
    • Yellow: Low concentration.
    • Yellow-Orange: Moderate concentration.
    • Orange: High concentration.
    • Orange-Red: Very high concentration.
    • Blue (No change): No glucose present.
    • Benedict reagent also does not react with starch.

Test your understanding of cell composition and the significance of organic molecules in biology. This quiz covers topics such as water's role in cells, the types of organic molecules, and the processes of dehydration and hydrolysis. Perfect for students studying cellular biology!