Chemical composition of cells

Topics: Protein, Amino acid, Glucose Pages: 3 (593 words) Published: May 26, 2014
Biology Notes :

Chapter 2 :

Organic chemical compounds include : Saccharides, Proteins, lipids and nucleic acid.

Functions of water are :
Acts as a solvent
For excretion of metabolites
Acts as medium of transport
For supporting and maintaining of shapes
Acts as a medium to carry out biochemical reactions.
Helps in lubrication
Maintains body temperature
Has high tension and cohesion
Provides moisture
Maintains osmoic balance and turgidity

Saccharides : (a.k.a Carbohydrates)

It is made up from Carbon, Hydrogen and Oxygen
It is the main source of energy of cells.
It can be divided into 3 groups – Monosaccharides, Disaccharides and polysaccharides.

Monosacharides :
They are known as simple sugars
They cannot be hydrolysed/broken down into smaller units
Eg. Glucose, Fructose, Galactose
They are reducing sugars

Disaccharides :
They are formed by condensation reaction.
Also known as complex sugars
They are water soluble, sweet tasting and can be crystallized. Eg. Glucose + Glucose  Maltose + Water
Eg. Glucose + Fructose  Sucrose + water
Eg. Glucose + Galactose  Lactose + Water
Maltose and Lactose are both reducing sugars while Sucrose is a non-reducing sugar.

* Hydrolysis is a reaction whereby large molecules are broken down into simpler units by the addition of water.

Polysaccharides :
They are insoluble in water, tasteless, do not crystallize and a non-reducing agent. Common polysaccharides are starch, glycogen and cellulose.
Starch is found in wheat, rice, potatoes.
Glycogen is excess starch that is stored in the liver and mucle cells. Cellulose makes up cell wall of a plant cell.

Lipid :
Contain Carbon, Hydrogen and Oxygen
2 common lipids are Triglyceride and Lipoids

It is made up of 3 molecules of fatty acid
1 molecule of glycerol
Fatty acids can be divided into saturated fats and unsaturated fats.

Saturated Fats
Unsaturated Fats
Exist in solid state when in...
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