1. Biologically Important Molecules
Chapter 1.2
McGraw-Hill Ryerson
Biology 12 (2011)

2. Macromolecules 4 Important macromolecules:
Carbohydrate
Nucleic Acid
Protein
Lipid
Polymers are composed of repeating monomers
Monomer = single unit

3. CARBOHYDRATES Carbohydrates may be classified into 3 main groups:
monosaccharides – simple sugars
oligosaccharides – sugars containing 2 or 3 simple sugars attached by covalent bonds called glycosidic linkages
polysaccharides – polymers composed of several hundred to several thousand monosaccharide subunits

4. Carbohydrate Monosaccharide = one sugar
e.g. Glucose, Fructose, Galactose
The 3 examples above are isomers of each other
Isomers = same molecular formula but different structure
Isomers causes different characteristics, despite same exact molecular formula

5. Carbohydrate Disaccharide = 2 sugars
e.g. Lactose = Glucose + Galactose, Sucrose = Glucose + Fructose
Covalent bond between monosaccharides is called a glycosidic linkage.

6. Carbohydrate Glucose can come in two forms: Alpha glucose Beta glucose
Different forms give rise to different linkage patterns in the polysaccharides
Alpha – allows branching seen in starch and glycogen (energy storage)
Beta – allows linearity as seen in cellulose (structural)

7. Carbohydrate Polysaccharide = many sugars
e.g. Starch, glycogen, cellulose
Many monosaccharides joined together by glycosidic bonds to create long chains

8. Lipids Large amount of carbon-hydrogen bonds Makes it hydrophobic
Many C-H bonds stores lots of energy but less accessible than carbohydrates

9. Lipids Triglyceride = Glycerol molecule with 3 fatty acids
Saturated fatty acids
Carbon chain is fully filled with max number
of Hydrogen atoms (i.e. no double bonds)
Straight chains
Unsaturated fatty acids
Double bonds present
between some carbons
Double bonds causes
kinks in chain leading to
bent shape

10. Lipids
Phospholipid = glyceride with 2 fatty acid chains and a phosphate group
Phosphate group is attached to a polar R group
Thus creates hydrophobic tail and hydrophobic head
Makes up phospholipid bilayer in cell membranes

11. Lipids Steroid = Compound composing 4 carbon-based rings
Examples: Cholesterol, Testosterone, Estrogen
Waxes = lipids with long carbon-based chains
Examples: spermaceti, beeswax, paraffin wax

12. Protein Made up of amino acids
Amino acid is a molecule where a central carbon is attached to an amino group, carboxyl group, a hydrogen atom, and an R group
R group is different for each type of amino acids, giving rise to distinct characteristics

13. Protein

14. Protein Polypeptide = polymers of amino acids
Amino acids are joined by covalent bonds called peptide bonds

15. Protein
Polypeptides are long strands that can take shape due to the interactions of all the amino acids:
Primary structure
Refers to the linear sequence of the amino acids
Secondary Structure
Polypeptides can sometimes coil into an alpha-helix shape
Polypeptides can sometimes fold into a beta-pleated sheet
Tertiary Structure
Combination of different secondary structures gives rise to a three-dimensional shape
Done through folding and interactions of the R groups of different amino acids
Molecular chaperones also facilitate the folding
Quaternary Structure
Amalgamation of many tertiary structures

16. Protein
Proteins’ shape and confirguration of its structures gives rise to unique characteristics and functions:
- Enzymes (biological catalysts)
- Structural support
- Transport
- Enabling mobility
- Regulate Cellular processes
- Provide defence

17. Protein
Proteins’ shape and confirguration of its structures gives rise to unique characteristics and functions
Protein denaturation occurs when the protein is exposed to:
- extreme temperatures
- extreme pH conditions
- extreme salt environments
Can you explain why?
If a protein becomes denatured, can it perform its function?

18. Nucleic Acids
Nucleic acids = macromolecules composed of nucleotide monomers
Nucleotide: a carbon-based sugar attached to both a phosphate group and a nitrogenous base

19. Nucleic Acids 2 types of nucleic acid: DNA: Deoxyribonucleic acid
Nucleotides in DNA contain a deoxyribose sugar
RNA: Ribonucleic acid
Nucleotides in RNA contain a ribose sugar

20. Nucleic Acid
Nucleotides differ from each other according to their nitrogenous base
Do you remember which pair up?

21. Nucleic Acid
Nucleotides polymerize into strands by forming phosphodiester bonds
Phosphodiester bonds are formed between phosphate group of one nucleotide and a hydroxyl group on the sugar of the next nucleotide in the strand

22. Nucleic Acid DNA is made up of two strands of nucleic acid
The two strands wind around and is often referred to as a “double helix”
Double helix structure causes nitrogenous base to be facing each other and bond to each other through hydrogen bonds
Adenine pairs with Thymine
(2 H bonds)
Cytosine pairs with Guanine
(3 H bonds)
The two strands run antiparralel
i.e. they run in opposite directions

23. Nucleic Acid RNA is made up of just one strand of nucleic acid
DNA contains Adenine, Guanine, Cytosine, and Thymine
RNA contains Adenine, Guanine, Cytosine, and Uracil

24. Homework
Pg 31
#1-6, 8, 11, 12