nucleic acids and proteins

• Adenine (A) always pairs with thymine (T), while cytosine (C) always pairs with guanine (G).
• In RNA, uracil complements adenine while in DNA adenine complements with thymine
• Nucleotides are consist of a nitrogenous base, a five-carbon (pentose) sugar called ribose or deoxyribose, and a phosphate group
• Ribonucleic acid (RNA): A single-stranded molecule involved in protein synthesis and other cellular processes.
• Biomacromolecules are large organic molecules that are important for living cells. 
• Proteins are complex macromolecules made up of amino acids linked by peptide bonds.
• Biomacromolecules are large organic molecules consisting of carbon and hydrogen. They can also contain elements such as oxygen, phosphorus and nitrogen.
• Nucleic acid monomers are nucleotides. Carbohydrate monomers are monosaccharides. Lipid monomers are glycerol with fatty acids. Protein monomers are amino acids.
• Four main types of biomacromolecules are nucleic acids, proteins, lipids and carbohydrates. All are formed by condensation reactions which result in bonds forming by the removal of water.
• Nucleic acids, proteins and carbohydrates are polymers.

  A polymer is a molecule made up of many smaller, repeating units linked together. Each of these smaller individual units is called a monomer.
• Nucleic are biomacromolecules that store and transmit inherited characteristics of organisms in their nucleotide sequences. They specifically encode instructions for the synthesis of proteins.
• (Nucleic Acid) condensation polymerisation is when free nucleotides

  (monomers) join together to form a nucleic acid (polymer) Water molecules are produced as a by-product. Free nucleotides can be continuously added to each sugar group forming a long sugar-phosphate backbone, called a polynucleotide.
• Occurs between two nucleotides. A hydrogen ion (H+) attached to the sugar group from nucleotide A, joins with a hydroxyl group (OH-) associated with the phosphate group of nucleotide B, to create water (by-product). The bond created is a phosphodiester bond (a type of strong covalent bond).
• In polynucleotide strands, 5 prime (5’) end = the end that has a free phosphate group on the 5’ carbon of the sugar.

  3 prime (3’) end = the opposite end of the strand which has a free hydroxyl group on the 3’ carbon of the sugar.
• DNA stores information that controls the cell's activities.

  Contains the nitrogenous bases A, T, C and G and deoxyribose sugar. DNA segments that contain a higher percentage of G-C pairs are stronger and harder to break apart. Is double stranded formed by two chains of polynucleotides twisted into a double helix. Hydrogen bonds stabilise the structure.The two strands of a DNA molecule are antiparallel. This means the two strands run in opposite directions.
• RNA is found as a single strand and is much shorter than DNA molecules. Contains ribose instead of deoxyribose sugar.

  Uracil is more stable in single-stranded polynucleotides.
• Three main forms of RNA:

  Messenger RNA (mRNA)

  Ribosomal RNA (rRNA)

  Transfer RNA (tRNA)
• mRNA carries a copy of the DNA’s nucleotide sequence to be translated into a protein. Is formed in the nucleus through the process of transcription.
• Ribosomal RNA forms ribosomes, the site of translation of the mRNA into proteins. Is synthesised in the nucleolus of the cell nucleus.
• Transfer RNA (tRNA) are free to move in the cytoplasm.

  Carry amino acids from the cytoplasm to the appropriate positions on the mRNA in ribosomes. Ensure amino acids are placed in the appropriate order by matching its anticodon sequence to the complementary codon sequence in the mRNA. Responsible for building the polypeptide chain during translation.
• There are 61 different tRNA molecules despite there being 64 possible codons that each code for an amino acid.

  No tRNA recognise STOP codons, therefore translation termination cannot be avoided.
• Proteins each have a unique three-dimensional shape, that enables the protein to carry out its specific function. Proteins are made up of a repeated subunit monomer called an amino acid.
• Each amino acid consists of;

  An amine group (NH2)

  A carboxyl group (COOH)

  A variable R group (side chain)
• In organisms, there are 20 different standard amino acids, each with a different R group.

  R groups have variable properties such as;

  Charged or uncharged

  Polar or non-polar

  Hydrophobic or hydrophilic
• EXTENSION: Determined by their chemical nature, amino acids can be classified as;

  Non-Polar / Polar

  Acidic / Basic
• (protein) condensation polymerisation is the reaction resulting in the removal of water (dehydration) in order to join amino acids together with strong peptide bonds. Requires energy, in the form of ATP to occur.
• Protein Secretory Pathway: Ribosomes ➡️ Rough ER ➡️ Golgi apparatus ➡️ Vesicle ➡️ Exocytosis