4 Aug 2015
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CHM 115 - Lecture 26 - Biochemistry
Carbohydrates
● Carbohydrates are the most abundant class of biological molecules
● Carbohydrates are built through photosynthesis
○ Photosynthesis uses light energy to combine CO2 and H2O molecules into
carbohydrates
○ General reaction: nCO2 + nH2O + light energy --> CnH2nOn + nO2
● Carbohydrates are useful for:
○ Energy storage (sugars and starches)
○ Structural material (cellulose)
○ Component of ATP (energy transfer molecule)
○ Component of recognition sites on cell surfaces
○ Part of backbone of RNA and DNA
● Sugars are the smallest carbohydrate molecules
○ The preferred structure of sugars is 5-6 membered rings that may be
joined together
○ Glucose:
○ Lactose:
○ Sugars are carbohydrate monomers
● Sugar monomers may be joined into chains to form carbohydrate polymers such
as cellulose and starch
○ Cellulose (top) and starch (bottom)
Amino Acids
● Amino acids are the building blocks of proteins
● Amino acids consist of a central carbon bonded to an amine group, a carbon with
a carboxylic acid group, and one of 20 side groups, denoted as ‘R’
● Peptide bonding occurs between amino acids
○ Peptide bonds are the bonds between amine groups and carboxylic acid
groups
● Inside the cell, the pH is at a level such that amino acids exist in their ionized
forms
● Amino acids have different properties depending on the chemistry of their side
chains