Biology Key Concepts Unit 2 Biological Molecules Entry Exam

Biology Key Concepts Unit 2 Biological Molecules Entry Exam. Key concepts in biology Unit 2: Biological Molecules for MDCAT Preparation Important key point notes for part 1 unit 2.

Biology Unit 2 Key Points Notes


  1. Biochemistry is the study of biological molecules.
    » Carbohydrates

Nucleic acid

  1. Approximate chemical percent composition of a bacterial and a Mammalian cell
    Contents Bacterial cell Mammalian cell
    Water 70 70
    Proteins 15 18
    Carbohydrates 3 4
    Lipids 2 3
    DNA 1 0.25
    RNA 6 1.1
    Enzymes, hormones 2 2
    Inorganic ions etc 1 1
  2. Water is a polar molecule due to which it dissolves almost all types of polar substances and is therefore regarded as the universal solvent.
  3. Specific heat is the amount of heat energy required to raise the temperature of one gram of water by one degree Celsius.
  4. Water has high specific heat.
  5. Water also has a high heat of vaporization.
  6. Heat of vaporization of water is the heat required to convert one gram of liquid water into vapors Get its boiling point.
  7. High heat of vaporization helps animals and plants to get rid of excess body heat during sweating and transpiration respectively.
  8. The presence of hydrogen bonds among the water molecules cause water to remain liquid
  9. Without hydrogen bonds, water would boil at -80 “C and would freeze at
    -100 C.
  10. Carbohydrates are polyhydroxy aldehydes or ketones.
  11. Monosaccharide’s are the simplest carbohydrates which cannot be broken down into simpler ones. So they are a unit of carbohydrates.
  12. They contain 3 to 7 carbon atoms
  13. They are the sweetest carbohydrate.
  14. They are easily soluble in water
  15. They are commonly called sugar
  16. Human body can only digest D- sugars (right-handed sugar).

Important Biology Points

  1. Penultimate carbon, a carbon that is adjacent to the last carbon. For
    For example in glucose, it is carbon no S but in ribose, it is carbon no 4.
    22.0ligosaccharide: Carbohydrate which contains 2-10 monosaccharide are called oligosaccharide.
  2. Disaccharides are the most common oligosaccharides.
  3. Most common disaccharide are;
    ” Sucrose = glucose + fructose
    ” Maltose = glucose + glucose
    ” Lactose = glucose + galactose
  4. Oligosaccharides are less sweet than monosaccharides and less soluble than monosaccharides.
    26.Lactose is milk sugar and maltose is fruit sugar and sucrose is present in sugarcane.
  5. Polysaccharides are carbohydrates that contain more than ten monosaccharide units.
  6. Polysaccharide may be heteropolysaccharide which contains different Monosaccharide e.g. hyaluronic acid which is composed of N-acetyl glucosamine and glucuronic acid. Other examples of heteropolysaccharides are chitin, murine and agar and may be homopolysaccharide which contains same monosaccharide unit e.g glycogen.
  7. Polysaccharides are insoluble in water.
  8. They are not sweet in taste therefore called non-sugar.
  9. Glycogen is branched, cellulose is unbranched while Starch may be branched or unbranched.
  10. Animals, bacteria, and fungi store food in the form of glycogen.
  11. Monosaccharide and oligosaccharide are crystalline solid while polysaccharides is amorphous solid. “
  12. Proteins are the most important biological molecules composed of C, H, a N and sometimes sulfur (cysteine) and selenium (selenocysteine) is the most abundant organic biological molecule present inside the cell (18% in the mammalian cell)
  13. Building blocks of proteins are called amino acids.
    37.More than 300 amino acids are found in nature but only 22 of them are responsible for protein synthesis.
    38.Among these 22 amino acids, 20 are common and the remaining 2 i.e. selenocysteine and pyrolysis are called rare amino acids.

39.Simplest amino acid is glycine.
4O.The complex amino acid is tryptophan.

  1. Acidic amino acids are glutamic acid and aspartic acid.
    42.Basic amino acids are lysine: arginine and histidine.
  2. Sulphur contain amino acid are cysteine, methionine.
    44.Aromatic amino acids are phenylalanine, tyrosine, and tryptophan.
    45.1 Amino acid: Amino acids which have an NH2 group on the left side are called L amino acids.
    46.0 Amino acid: Amino acids that have an Nh2 group on the right side are called D amino acid.

47.Human body only synthesizes protein from L amino acid and D amino acid are found in the bacterial cell wall.
48.The only amino acid in which the central carbon is symmetric is glycine.
49.Remaining all amino acids have asymmetric central carbon.
50.A carbon which is attached with at least two same groups is called
symmetric carbon while a carbon that is attached with 4 different groups is called asymmetric carbon.

  1. The only amino acid in which H is found instead of the alkyl group is glycine.
    52.All the amino acid has the same amino, carboxyl alpha carbon, and hydrogen but all amino acids have different alkyl groups.
  2. Two amino acids are linked by peptide bonds.

54.Peptide bond is formed by peptidyl transferees enzyme which is actually rRNA found in the large subunit of the ribosome of both prokaryote and eukaryote and is also called ribozyme.

  1. The name peptide bond is given because it is broken by pepsin.
  2. The bond is formed between the carboxyl group of one amino acid and the amino group of another amino acid.

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