Science notes - Bio Chemistry


• Chemical formulae, know what they mean, know some common examples

Table showing chemicals and their formulas

Name of chemical

Chemical formulae









• Ionic bonding (between metals and non-metals); predict ions using the periodic table, write formulae for ionic salts.

Metal in periodic table

Non metals in the periodic table

Reaction between metals and non metals

Formulae for ionic salts







Magnesium (s) + chlorine (g) = magnesium chloride(s)

Mg+2(s) + Cl-1(g) =MgCl2







Nickel(s) + sulphur (g) = Nickel sulphate

Ni+2(s) + S-2(g) = NiS







Sodium(s) + oxygen (g) = Sodium oxide

Na(s) + O+2(g) = Na2O







Barium(s) + Sulphur(g) = Barium sulphate

Ba(s) + S(g) = Ba2S

• How and why the rate of chemical reactions are affected by temperature, catalysts, concentration of reactants, surface area of solid reactants

High temperatures will cause an increase in the rate of reaction while low temperature will decrease the reaction rate. This is because high temperature increases the mobility of the particles.

Introduction of catalyst will increase the reaction rate of substances

Highly concentrated reagents increase the reaction of substances while lowly concentrated reactions slow the reaction of substances

Large surface area of reactants increases the activity of substances while smaller surface area reduces the reaction.

Law of Conservation of Mass in a chemical reaction

• How to balance chemical equations

Balancing chemical equations

2HCl + 2Na → 2NaCl + H2

4Na + O2 → 2Na2O

2CH4+ O2 → CO2+ 4H2O

• How to write precipitation equations

Precipitation reactions are represented using different types of chemical equations. The first is through molecular equations, complete ionic equations and net ionic equations. It is vital to balance all the precipitation reactions.

• How to use the symbols (g), (s), (l) and (aq) to describe the states of reactants and products in a chemical equation

The symbol g, indicates the gaseous state of a chemical, s. the solid state, l, the liquid state and q, the aqueous state of a chemical.

Barium(s) + oxygen (g) = Barium sulphate(s)

Copper(s) + water (l) = Copper oxide(s) + hydrogen (g)

Silver nitrate (aq) + nitrogen chloride (aq) = Silver chloride (s)

• Types of reactions: combination, decomposition, precipitation, combustion, displacement

Type of reaction


Combustion reaction

Characterised by the fact that one of the reactants must be oxygen and the reaction produces heat and flame. In this reaction, organic compounds react with oxygen to produce carbon (IV) oxide and water vapour.

Displacement reaction

In this reactions parts of the reactants are exchanged

Combustion reaction

Two substances combine to form another substance

Decomposition reaction

Single compounds react to produce two or more substances. Temperatures are elevated for the occurrence of this reaction

• How to write equations for reactions of metal with oxygen, reactions of metals with acids and metal displacement reactions

Metal with oxygen


Metals with acids


Metal displacement reactions


Mg + O2 = Mg2O


Mg + HCl = MgCl+ H2


Fe+ CuSO = Fe3SO + Cu

• How to write a balanced chemical equation using symbols from a worded chemical equation

Hydrogen Chloride + Sodium = Sodium chloride + Hydrogen

2HCl + 2Na → 2NaCl + H2

Sodium + Oxygen = Sodium Oxide

4Na + O2 → 2Na2O

Methane+ Oxygen = Carbon (IV) oxide + water

2CH4+ O2 → CO2+ 4H2O


• How interpret pedigrees

Pedigrees are either

Autosomal Dominant- This is where one of the parents has a normal gene and an abnormal gene

Autosomal recessive- Occurs when parents have two copies of abnormal genes. This condition skips generations

Sex linked

His is X linked. Because male is XY and female XX. Males can only inherit the disease from their mothers

• How to complete punnet squares










• What makes up DNA?

The DNA is a polymer that has nucleotides and each nucleotide consists of 5-carbon deoxyribose sugar, a base pair and phosphate group. The base pairs include Adenine, Guanine, and Thymine. Adenine and Guanine are called Purines while cytosine and Thymine are pyrimidines.

• How DNA is arranged and where it is found in the body

DNA is found in the body cells the base paired have an arrangement in such a way that Guanine pairs with Cytosine and Adenine pairs up with thymine.

• Chromosomes

Chromosomes are thread like structures in a DNA that are responsible for caring the genetic material. Each chromosome has a centromere and a tail.

• How to interpret the appearance of different generations with pedigrees

• Karyotyping

Karyotyping is attest that is done to examine chromosomes in a sample that has cells. Through Karyotyping, individuals can be able to count cells and identify structural changes in chromosomes

• Different blood types and their respective genotypes & phenotypes

Blood groups

Genotype AO phenotype A

Genotype BO phenotype B

Genotype AB phenotype AB

Genotype OO phenotype O

• The impact of dominant, recessive, co-dominant and incomplete dominant alleles on inheritance

Dominant alleles are responsible for passage of genetic characteristics to the offspring

Recessive genes may be significant when it comes to the inheritance of diseased alles

Co- dominant is responsible for completely masking over another gene e.g. colour Red and white to give purely red or white depending on the dominant colour

Incomplete dominance indicates that characteristics are equality represented e.g. colour red and white to give pink offspring.

• The meaning of homozygous and heterozygous alleles

Homozygous alleles are alleles that are identical. They may be homozygous dominant, AA or recessive, aa. Heterozygous alleles are alles that are not identical example Aa or Bb

• Mitosis and meiosis



Gives raise to two daughter cells

Gives raise to four daughter cells

Occurs in body or somatic cells

Occurs in sex cells

Cell division is for the purpose of gamete production and reproduction

Cell division for the purpose of repair of damaged cells and growth replacement

• Different theories of evolution

Evolution theories include the theory of Charles Darwin, the big band theory, Modern theory of evolution, and the Lamarck’s Theory of evolution

• Natural selection and artificial selection

Natural selection

This is as result of natural factures and it occurs when a specific feature gives and organism survival advantages.

Artificial selection

Is as a result of human activities whereby the choose certain and breed organisms to fit whatever they desire

• Definition of basic terms such as genotype, phenotype, genes

Genotype is the genetic representation of genes and it normally occurs in pairs for example AA or Aa, or aa

Phenotype is the physical observation and description of an organism for example, tall, red

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