compendium 12

• DNA


  Deoxyribonucleic Acid - in nucleus + mitochondria - constitutes blueprint that codes for protein synthesis
• How much DNA is due to genes?

  1.5% - 98.5% non coding (regulatory sequences, introns, noncoding DNA)
• What is the structure of DNA?

  Double helix model - double-stranded polymer - alternating sugar-phosphate backbone - deoxyribose sugars - complementary nitrogenous bases from runs of the ladder
• What are the nitrogenous bases in DNA?

  Adenine - thymine

  Guanine - cytosine
• How are the nitrogenous bases held together in DNA?

  Hydrogen bonds
• How is DNA organised?

  Double strands of DNA (twisted ladder) - DNA wrapped around proteins (histones) - histones & DNA bundled together (chromatin) - chromatin twists & condense to form chromosomes
• Somatic cells


  A biological cell forming the body of a multicellular organism - most cells - 46 chromosomes said to have the full amount fo DNA (diploid) - mitosis
• Homologous chromosomes


  Pairs of chromosomes - where one is from the father and the other is from the mother
• Germ cell


  Cells that give rise to gametes - located in the gonads (ovaries + testes) - meiosis
• Gametes


  Cells that fuse during sexual reproduction - sperm or egg - 23 chromosomes - half the normal amount of DNA (haploid)
• How many chromosomes do humans have?

  23 pairs of chromosomes, 46 diploid number, 22 pairs of autosomal chromosomes & 1 pair of sex chromosomes (XX or XY)
• Karyotype


  A map of chromosomes in a dividing cell
• RNA


  Ribonucleic acid - single stranded polymer, self complementary sequences form folds, bulges & helices - support DNA - found in nucleus + cytoplasm - alternating sugar-phosphate backbone - ribose sugar - nitrogenous bases
• What are the nitrogenous bases in RNA?

  Adenine - uracil

  Guanine - cytosine
• What are the 3 types of RNA?

  mRNA, tRNA, rRNA
• Proteins


  Long chain of amino acids linked to each other by peptide bonds - bounded by covalent bonds - made from 20 AA, each one having specific properties due to its side chains - each AA has an amine groupe, a carboxyl group, hydrogen atom & side chain
• Side chains


  Part of the amino acid not involved in linking to each other - some are no polar & hydrophobic, others are hydrophilic or positively charged
• How many of each protein is there?

  9 essential AA, 5 non essential AA, 6 conditional AA
• Functions of proteins


  Regulation, transport, protection, contraction, structure, energy
• Regulation


  Enzymes control chemical reactions - hormones regulate many physiological processes
• Transport


  Haemoglobin transports oxygen & carbon dioxide in the blood - plasma proteins transport many substances in the blood - proteins in plasma membrane control movement of materials into & out of cell
• Protection


  Antibodies protect against microorganisms + other foreign substances
• Contraction


  Actin + myosin in muscle are responsible for muscle contraction
• Structure


  Collagen fibres form a structural framework in many parts of the body - keratin adds strength to skin, hair, nails
• Energy


  Proteins can be broken down for energy
• Protein structure (Overall)


  Interactions between side groups in a long chain & peptide bonds affect the way a protein can fold & take shape. Primary - Secondary - Tertiary - Quaternary
• Protein structure - Primary


  Sequence of amino acids linked by peptide bonds
• Protein structure - Secondary

  Proteins fold to form secondary structure (AA have different side chains) - 2 regular folding patterns: alpha helices (keratin) & beta pleated sheets (fibroin, silk)
• Protein structure - Tertiary


  3D shape is determined by folding of secondary structure - a-helices & b-sheet fold to form unique structures which are held together by bonds between AA that may be far apart in actual polypeptide chains
• Protein structure - Quarternary

  Combined 3D structure of 2 or more peptide chains
• What are the 2 types of proteins

  Fibrous & globular
• Fibrous Proteins


  Simple, elongated peptide chains arranged in parallel fashion along a single axis - insoluble in water + stable - provide mechanical support & tensile strength, more structural - less sensitive to changes - abundant outside the cell where they make up a lot of the matrix in between the cells
• What is an example of a fibrous protein?

  Collagen, keratin, myosin
• Globular proteins


  Polypeptide chain folds up into a compact shape - water soluble - mobile, chemically active - play crucial roles in nearly all biological processes, more functional - sensitive to changes
• What is an example of a globular protein?


  Haemoglobin, insulin, antibodies
• Nucleic acids


  Organic macromolecules - main info carrying molecules
• Polynucleotides


  A chain of repeating monomers (nucleotides)
• Nucleotide

  Pentose sugar (deoxyribose, ribose), phosphate group, nitrogenous base (adenine, guanine, cytosine, thymine, uracil) - nucleotide + phosphate group - sequence of nitrogenous bases carries the info
• Nucleoside


  Pentose sugar + nitrogenous base
• Proteome


  All proteins that a cell makes - all cells dont make all proteins - proteome of one cell can be compared to another to see how different they are