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1.5 Structure and Function of Biological Macromolecules

#disaccharides

#polysaccharides

#proteins

#denaturation

⏱️  2 min read

written by

Danna Esther Gelfand

danna esther gelfand

May 29, 2020


Disaccharides

Disaccharide – two monosaccharides joined together by a covalent bond through dehydration synthesis (Di - two).

Most Common Disaccharides

  • Maltose - disaccharide of two glucose monosaccharides combined together by dehydration synthesis.

  • Sucrose - disaccharide of glucose monosaccharide and a fructose monosaccharide combined together by dehydration synthesis.

  • Lactose - disaccharide of glucose monosaccharide and a galactose monosaccharide combined together by dehydration synthesis.

Polysaccharides

The covalent bond that the monosaccharides are joined together by is called a glycosidic bond, it forms both disaccharides and polysaccharides.

Polysaccharides - polymers of sugars that have functions of storage and structure which are determined by the positions of the glycosidic bonds and the monomers in the sugar polymers. (macromolecules that hold between 100-1000 monomers)

Most common types of Polysaccharides and Their Functions

  • Starch – stores energy in plants

  • Glycogen – stores energy in animals. Usually stored in muscle and liver cells.

  • Cellulose – structural Polysaccharide. An important part of the cell wall in plants.

  • Chitin – structural Polysaccharide. Found in exoskeletons of arthropods and cell wall of fungi.

Varied Functions of Proteins

Varied functions of proteins include, but are not limited to: structural, catalytic, signaling, defense, and transport within cells. Functioning as: enzymes, hormones, storage, transport (through membranes), defense proteins, receptor proteins.

Levels of Protein Structure

  1. Primary Structure – a sequence of amino acids, peptide bonds.

  2. Secondary Structure– the result of hydrogen bonding between the components of the polypeptide backbone, the carboxyl and amino functional groups along the peptide chain-forming alpha helix or beta-pleated sheet

  3. Tertiary Structure – the result of interactions between the alpha-helix and Beta pleated sheet (interactions of the same polypeptide chain) (van der Waals forces, hydrophobic interactions, hydrogen bonding, disulfide bridges, etc. cause its formation).

  4. Quaternary Structure – interactions between two or more polypeptide chains forming the multi-subunit protein. (common examples you will come across: DNA polymerase, hemoglobin)

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Image courtesy of LumenLearning.

Denaturation

Denaturation - proteins are broken down by heat, acids, and high ion concentrations such as that of sodium (Na+), therefore an inactive form of protein because it loses its structure.

**Important connections to other units: - Sickle-cell disease, an inherited blood disorder is caused by a single amino acid substitution in the protein hemoglobin.

Species that share a common ancestor have some similar structured proteins and their amino acids correspond to each other.

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