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Molecular Biology (Carbon compound (Nucleic acids 核酸 (DNA (DNA replication…

- - - - disaccharide: consist of two monosaccharides linked together
      - monosaccharide
        
        single sugar units
        
        examples: glucose, fructose, ribose
      - polysaccharide: consist of many monosaccharides linked together
  - - - liquid at body temperature
      - solid at room temperature
    - - composition (linked by condensation)
        
        three fatty acids
        
        one glycerol (C3H8O3)
    - - at one end of the chain is the acid part_carboxyl group -COOH
      - saturated: single bonds between all the carbon atoms_as much H atoms as possible
        eg. animal fats
      - unsaturated:
        have one or more double bond
        contain less H than they can
        eg. most vegetable oils
        
        monounsaturated: one double bond
        
        polyunsaturated: more than one doble bond
        
        cis-fatty acid (eg. triglycerides): on the same side of the two carbon, usually liquid at room temperature_oil
        
        trans-fatty acid: on the opposite side of the two carbon, don't have bend (less good at packing together), have a higher melting point, solid at room temperature
  - - - chains of amino acids
      - main component of proteins
    - - linked together by condensation to form polypeptides
      - peptide bond: after condensation, a new bond is formed between two amino acid
      - dipeptide: two amino acids link together
      - polypeptide: many amino acids link together
      - composition
        
        amino group
        
        R group (20 different R goups)
        
        carboxyl group
        
        C, H
      - amino sequence
        
        determined by the base sequence of a molecule of RNA
        
        can be linked together in any sequence giving a huge range of possible polypeptides
        
        determines the conformation of a protein
    - - Formation
        
        secondary structure: twist into loops, sheets and coils by hydrogen bond_arise into polypeptide
        
        tertiary structure: fold into a functional domains_pack further_most proteins are folded up to produce a globular shape
        
        quaternary structure: many proteins, including most enzymes, consist of two or more polypeptides
        
        primary structure: the order of a chain of amino acid_ one chain of polypeptide
      - three-dimensional strucutre
      - factors determine the conformation of a protein
        
        amino acid sequence of a protein
        
        its constituent polypeptides
    - - enzyme: a biological catalyst made of globular protein
      - substrate: a reactant in an enzyme-catalysed reaction
      - active site: the region of an enzyme molecule surface whee the substrate molecule binds and catalysis occurs
      - Proteins involved in replication
        
        topoisomerase: releases the strain that develops ahead of the helicase
        
        single-stranded binding proteins: keep the strands apart long enough to allow the template strand to be copied
        
        helicase: unwinds the DNA at the replication fork
        
        RNA primer: starts replication
        
        ① one on the leading strand
        
        ② many on the lagging strand
        
        necessary to initiate the activity of the DNA polymerase
        
        DNA primase: creates one RNA primer on the leading strand and many RNA primers on the lagging strand
        
        DNA polymerase: responsible for covalently linking the deoxyribonucleotide monophosphate to the 3' end of the growing strand
        
        DNA ligase: connects the gaps between fragments
  - - - double-stranded_double helix_run in opposite directions
      - hydrogen bonds between base
        covalent bonds between nucleotides
      - complementary
        base pairing
        
        adenine (A)-thymine (T)
        
        guanine (G)-cytosine (C)
      - the type of pentose is deoxyribose
      - DNA replication
        
        semi-conservative replication
        
        stages of DNA replication
        
        helicase unwinds the double helix and separates the two strands by breaking hydrogen bonds
        
        DNA polymerase links nucleotides togethere to form new strands, using the pre-existing strands as templates
        
        the daughter DNA molecules each rewind into a double helix
        
        RNA primer create a short length of primer, DNA polymerase attach to the 3' end of RNA primer
        
        On the lagging strand, another kind of DNA polymerase replace the primer with nucleotide. The DNA ligase link them together
        
        DNA replication begins at sites called origins of replication
        
        direction of the replication: 5' to 3' direction for the new strand
        
        Okazaki fragments: new fragments created on the lagging strand(short lengths of DNA form between RNA preimers on the lagging strand)
        
        leading strand: DNA polymerases follows the replication fork as it opens
        
        lagging strand: made in fragments moving away from the replication fork
    - - Transcription
      - Translation
        
        Initiation
        
        Elongation
        
        Termination
    - - the monomer of nucleic aicd
      - composition
        
        a sugar (has 5 carbon atoms_pentose sugar)
        
        a phosphate group
        
        a base that contains nitrogen atom (4 types)
    - - help to supercoil DNA
      - Histones are used by the cell to
        package the DNA into structure called nucleosomes
      - the basic component of chromosome
- - - - protein synthesis using ribosomes
      - DNA synthesis during replication
      - Photosynthesis, including the production of glucose from carbon dioxide and water
      - synthesis of complex carbohydrates including starch, cellulose and glycogen
  - - - digestion of food in the mouth, stomach and small intestine
      - cell respiration in which glucose or lipids are oxidized to carbon dioxide and water
      - digestion of complex carbon compound in dead organic matter by decomposers