topic 1 biology

• Monomers, polymers, and macromolecules:

  • Monomers are simple molecules used as basic building blocks for the synthesis of polymers
  • Polymers are giant molecules made from many similar repeating subunits joined together in a chain
  • Macromolecules are large biological molecules such as proteins, polysaccharides, or nucleic acids
• Carbohydrates:

  • Contain carbon, hydrogen, and oxygen
  • Main source of energy
  • Divided into monosaccharides, disaccharides, and polysaccharides
• Monosaccharides:

  • Simplest carbohydrates
  • Examples: glucose, fructose, and galactose
  • Classified based on the number of carbon atoms (trioses, pentoses, hexoses)
• Disaccharides:

  • Formed by joining two monosaccharides with a glycosidic linkage via condensation
  • Examples: maltose, sucrose, lactose
• Polysaccharides:

  • Polymers of hundreds to thousands of monosaccharides joined by glycosidic linkages
  • Examples: Starch, Glycogen, Cellulose
• Lipids:

  • Water-insoluble but soluble in organic solvents
  • Functions include component of cell membrane, energy storage, insulation
  • Fatty acids are the building blocks of lipids
• Fatty acids:

  • Contain the acidic group -COOH
  • Have long hydrocarbon tails attached to the acid 'head'
• Triglycerides:

  • Consist of one glycerol and 3 fatty acids
  • Joined by ester linkage formed by condensation or esterification reaction
• Phospholipids:

  • 2 fatty acids attached to glycerol and a phosphate group
  • Self-assemble into aggregates with hydrophobic tails pointing inward and hydrophilic heads outward
• Nucleic acids:

  • DNA and RNA are nucleic acids
  • DNA contains essential information for cell activities, RNA stores and transfers information
  • Nucleic acids are polymers made up of nucleotides
• Nucleotides:

  • Made up of a nitrogen-containing base, a pentose sugar, and a phosphate group
  • Condensation occurs between sugar and phosphate group of different nucleotides, forming phosphodiester bond
• DNA:

  • Two polynucleotides held together by hydrogen bonds between bases
  • Complementary base pairing: A-T, C-G
  • Polynucleotide sequences are referenced in the 5' to 3' direction
• RNA:

  • Single-stranded molecule
  • Contains ribose sugar
  • 4 different nucleotide bases: A, G, C, U
• Differences between DNA and RNA:

  • DNA is double-stranded, RNA is single-stranded
  • DNA contains deoxyribose sugar, RNA contains ribose sugar
  • DNA has Thymine (T), RNA has Uracil (U)
• Proteins are large, complex molecules composed of amino acids
• The amino acids are linked together into long chains called polypeptides
• A protein consists of one or more polypeptide chains
• The polypeptide chains fold into complex three-dimensional shapes
• Proteins are one of the three main classes of food that provide energy to the body
• Proteins have various functions as enzymes, in cell movement, hormones, antibodies and structural material
• An amino acid has both an amino group & a carboxyl group
• A central carbon atom is bonded to an amine group, –NH2, and a carboxylic acid group, –COOH
• All parts of an amino acid molecule are covalently bonded to a central carbon atom
• The R group or the side chain determines the classes of each amino acid
• Twenty common amino acids are assembled into the thousands of different proteins in the human body
• Two amino acids can join together to form a peptide bond
• A polymer/polypeptide chain is formed from condensation of amino acids which are joined by peptide linkages/bonds
• The primary structure of a protein is the amino acid sequence of a protein
• The secondary structure of a protein results from hydrogen bonds at regular intervals along the polypeptide backbone
• The tertiary structure of a protein is determined by interactions among R groups and between R groups and the polypeptide backbone
• The quaternary structure of a protein results from the aggregation of two or more polypeptide subunits
• Globular proteins are folded into spherical shapes and are usually soluble
• Fibrous proteins have long parallel polypeptide chains and are usually insoluble
• Collagen is an insoluble fibrous protein found in skin
• Water is essential for all forms of life
• Water consists of an oxygen atom and two hydrogen atoms
• Water is a polar molecule with a net negative charge on the oxygen atom and a net positive charge on both hydrogen atoms
• Water acts as a solvent for various substances and is the transport medium in the blood
• Water has a high specific heat capacity due to hydrogen bonding between its molecules
• Water has a high latent heat of vaporization, requiring high energy to turn liquid water into water vapor