edexcel gcse biology as level unit 1, Study notes of Biology

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Molecule ,transpo an healt.

Chemistr for biologist.

Ionic and covalent bonding.

Biology is the study of living things , but living things consist of chemical substances. The basic unit of all elements is the atom. When the atoms of two or more different elements react, they form a compound. An atom is made up of a nucleus containing positive protons and neutral neutrons. The nucleus is surrounded by negative electrons. There are two types of bonding patterns of atoms, ❖ Ionic bonds. ❖ Covalent bonds. In ionic bonding atoms involved in the reaction receive or give electrons. The party that gives electrons are cations while the party that accepts electrons are anions. In covalent bonding the electrons are shared between 2 or more atoms. If their electronegativities are different then electrons get attracted to one rather than the other. This uneven distribution of charge within atoms is known as polarity. Chemical structure of water. The chemical formula of water is H 2 O. It consists of two hydrogen atoms and one oxygen atom. As their electronegativities are slightly different the electrons get Attracted more towards the oxygen molecule. Therefore oxygen atom becomes slightly negative than Hydrogen atoms. Therefore water is a polar molecule.

Question

1. Why is water known as a polar molecule.? Because the oxygen atom is slightly negative than two hydrogen atoms as electronegativity of oxygen is high.
2. State separately the charge in each atom of a water molecule. Oxygen slightly negative. Hydrogen slightly positive.

Inorgani ion.

The process in which ionic substance dissolves in water is known as dissolution. Living things contain 60%-70% of water therefore ionic substances that are dissolved in water exist as positive and negative ions. Some ions. Nitrate ion.(NO- 3 ). In DNA. In amino acids phosphate ions. (PO 4 3- ). ATP and ADP. DNA and RNA. Chloride ions (Cl−). nerve impulses. sweating. secretory systems. Hydrogen Carbonate ions (HCO 3 - ).buffer blood pH. Sodium ions (Na+). nerve impulses. sweating. secretory systems.