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Biomolecules: Proteins, Carbohydrates, and Lipids

Proteins

  • Definition: Proteins are a type of macromolecule made from one or more chains of amino acids. They are formed through the creation of dipeptides and polypeptides.

  • Structure:

    • R Group: This is a variable side chain that makes amino acids unique.

    • Key Elements: The key elements in proteins are:

    • Carbon (C)

    • Hydrogen (H)

    • Oxygen (O)

    • Nitrogen (N)

  • Types of Peptides:

    • Dipeptides: Two amino acids joined by a peptide bond.

    • Polypeptides: Chains of many amino acids joined by peptide bonds.

  • Amino Acids:

    • Essential Amino Acids: Cannot be made by the body and must be obtained through diet.

    • There are nine out of 20 amino acids that are classified as essential.

  • Function of Proteins:

    • Digestive Enzymes: Proteins that help to break down food molecules in the digestive system for absorption in the small intestine.

    • Examples of Digestive Enzymes:

      • Lipase

      • Amylase

      • Pepsin

      • Lactase

    • Hormones: Proteins that regulate various functions in the body by traveling in the bloodstream to target organs.

    • Examples:

      • Insulin

      • Glucagon (control blood glucose levels)

    • Structural Proteins: Build cellular structures such as the cytoskeleton.

    • Examples:

      • Actin

      • Keratin

      • Tubulin

    • Storage Proteins: Provide a nutritional source for developing embryos and seedlings in plants.

    • Examples:

      • Albumin found in eggs

Carbohydrates

  • Definition: Carbohydrates contain the elements of Carbon, Hydrogen, and Oxygen (CHO).

  • Function:

    • Serve primarily for energy release and storage in the body.

    • Essential for movement and growth.

    • Types of Carbohydrates:

    • Simple Sugars: Such as glucose that can release energy quickly.

    • Monosaccharides: Simple sugars that are the building blocks of carbohydrates.

      • Definition: The most common monosaccharide is glucose; others include fructose and galactose.

      • Isomers: Monosaccharides can have the same number of atoms but differ in structure, called isomers.

      • Examples: Glucose, galactose, fructose.

    • Monomers and Polymers:

    • Monomers: Single molecules that link to form polymers.

    • Polysaccharides: Comprised of many monosaccharides.

      • Monosaccharides can join to form Disaccharides (two sugars).

      • Examples of polysaccharides include starch and glycogen.

  • Dehydration Synthesis Reaction:

    • A chemical reaction where glucose monosaccharides combine to form larger carbohydrates with water as a by-product.

    • Reaction formula:
      CnH{2n}On + CmH{2m}Om
      ightarrow C{n+m}H{2(n+m)}O{n+m-1} + H2O

Lipids

  • Definition: Lipids are macromolecules that are insoluble in water.

  • Types of Lipids:

    • Triglycerides: Formed by glycerol and three fatty acids.

    • Reaction formula:
      Glycerol + 3 ext{ fatty acids}
      ightarrow ext{Triglycerides} + 3H_2O

    • Structure: Comprises one glycerol molecule and three fatty acids.

    • Function:

      • Long-term energy storage, insulation, and protection in the body.

      • They store a significant amount of energy in their long hydrocarbon tails.

      • Their insolubility in water prevents altering a cell's water potential.

    • Cholesterol:

    • A type of steroid and a crucial component of cell membranes.

    • Types:

      • LDL (Low-Density Lipoprotein): Considered "bad cholesterol" because high levels can lead to health issues such as heart disease.

      • HDL (High-Density Lipoprotein): Considered "good cholesterol" due to its role in removing cholesterol from arteries.

    • High levels of LDL can lead to fatty deposits in arteries and increase the risk of cardiovascular conditions.

    • Dietary measures to control cholesterol include reducing saturated and trans fats.

    • Waxes:

    • Long-chain hydrocarbons that are solid at room temperature and repel water.

    • Functions in nature to protect plants from water loss and in animals for cleaning and protection of fur or ears (e.g., bees use wax to build honeycomb).

    • Steroids:

    • Comprising a basic structure of four connected carbon rings.

    • Hydrophobic and insoluble in water.

    • Precursor for many hormones and neurotransmitters, including testosterone and estrogen.

Health Implications of Lipids

  • Maintaining healthy artery function hinges on balanced cholesterol levels; excessive LDL can lead to serious health problems.