This document provides lecture notes on general biology for health science students. It covers topics such as chemical bonds, chemical reactions, factors affecting reaction rates, biological macromolecules including proteins, nucleic acids, carbohydrates and lipids. For proteins, it discusses their functions, amino acids and protein structure. For nucleic acids, it covers their components and types. It also provides details on the types of carbohydrates and lipids. Finally, it assigns students to write notes on cell structure and functions, differences between cell types, cell division and movement for the next class.

1. GENERAL BIOLOGY
Lecture Notes For Health Science Students,
East Africa University - Garowe
Prepared by; H.Wahab [Lect. Nutrition & Food Science]
habibwahab8@gmail.com @habibwahab3

2. CHEMICAL BONDS
• Molecules are a group of atoms held together by energy in a stable
association.
• When a molecule contains atoms of more than one element, it is
called a compound.
• The atoms in a molecule are joined by chemical bonds
• The bonds can result when atoms with opposite charges attract (ionic
bonds).
• When two atoms share one or more pairs of electrons, this results into
a covalent bond.

3. CHEMICAL REACTIONS
• This refers to the formation and breaking of chemical bond.
• Reactants combine to form products.
A — B + C — D → A — C + B + D
Reactants products

4. FACTORS AFFECTING THE RATE OF A
CHEMICAL REACTION.
• Temperature: Heating up the reactants increases the rate of a
reaction (as long as the temperature isn’t so high as to destroy the
molecules).
• Concentration of reactants and products: Reactions proceed
more quickly when more reactants are available. An accumulation of
products typically speeds reactions in the reverse direction.
• Catalysts. A catalyst is a substance that increases the rate of a
reaction. It doesn’t alter the reaction’s equilibrium between
reactants and products, but it does shorten the time of the reaction.

5. BIOLOGICAL MACROMOLECULES
• Atoms are organized into hundreds of smaller molecules that
are linked together into long chains.
• Biological macromolecules are traditionally grouped into
four major categories:
• Proteins
• Nucleic Acids (DNA & RNA)
• Lipids, and
• Carbohydrates.

6. PROTEINS
Functions of Proteins
• Enzyme catalysis: Enzymes are biological catalysts that facilitate specific
chemical reactions.
• Defense: Other globular proteins form the core of the body’s hormone and
immune systems
• Transport: example the transport protein hemoglobin, that carries around oxygen.
• Support: Fibrous, or threadlike, proteins play structural roles; eg keratin in hair.
• Motion: Muscles contract through the sliding motion of proteins filament: actin and
myosin.
• Contractile proteins also play key roles in the cell’s cytoskeleton and in moving
materials within cells.
• Regulation: example; hormones serve as intercellular messengers in animals

7. AMINO ACIDS
• These are the units that make up a protein molecule.
• An amino acid is a molecule containing an amino group (—NH2), a carboxyl
group (—COOH), and a functional group ( R ) , all bonded to a central carbon
atom.
• A covalent bond that links two amino acids is called a peptide bond
• This bond is formed when the —NH2 end of one amino acid joins to the —
COOH end of another.

8. NUCLEIC ACIDS
• There are of two types namely; deoxyribonucleic acid (DNA and ribonucleic
acid (RNA).
• Nucleic acids are long polymers of repeating subunits called
nucleotides. Each nucleotide consists of three components:
• A five-carbon sugar (ribose in RNA and deoxyribose in DNA)
• A phosphate (—PO4) group; and
• Organic nitrogen containing base.

9. CARBOHYDRATES
• These are energy storage molecules in the body.
• They are of three types;
1. Monosaccharides (They are the simplest of the carbohydrates
example glucose; six carbon sugar
2. Disaccharides; (These consist of two monosaccharide combined
together by a covalent bond) when glucose combines with fructose, the
resulting disaccharide is called sucrose (table sugar) when glucose is
linked to galactose, the resulting disaccharide is lactose (milk sugar)
3. Polysaccharides; These are long chains of monosaccharides, like
glucose molecules, all formed through dehydration synthesis. Example
we have starch, chitin in insects and cellulose in plant cell walls

11. LIPIDS
• These are group of molecules that are insoluble in water.
• The four major classes of biologically important lipids are:
a) Phospholipids; the molecules of the cell which forms part of all
biological membranes.
b) Triacylglycerols (triglycerides); These are normal fats, consist of
three fatty acids attached to a glycerol molecule. When an organism
consumes excess carbohydrate, it is converted into starch, glycogen,
or fats and reserved for future use.
c) Terpenes; these are components of pigments such as chlorophyll and
visual pigment retina
d) Steroids/Cholesterol; example hormone testosterone and oestrogen.

12. • Tryglycerols
• Cholesterol

13. ASSIGNMENT 1
Read and make brief notes under the following heading;
• Cell structure and functions.
• The difference between the two major types of cells
• Cell division
• Cell movement
• Use font style; New times roman
• Use font size; 12
• Line spacing; 1.5
• Minimum pages; 3 pages
• Hand in; next class.