SLE111 Lecture Notes - Lecture 1: Ionic Bonding, Chemical Polarity, Nitrogenous Base
13 May 2018
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Cells and Genes Lecture Notes
SLE111 Cells and Genes – Introduction
Biological Part 2: The Building Materials of Cells
Properties of living things
- Order
- Energy processing
- Evolutionary adaptation
- Regulation
- Reproduction
- Growth and development
- Response to the environment
- Living things are comprised of cells
- Living things store and transmit information in form as DNA
Biological Molecules
- Biological molecules are compounds
- Compounds consist of elements
o Element: substance that cannot be broken down further
o Compound: substance that consists of two or more elements in a fixed ratio
- In biology, most important 4 is Hydrogen, Oxygen, Carbon, Nitrogen
- The major elements of life
o Carbon (19%)
o Oxygen (65%)
o Nitrogen (3%)
o Hydrogen (10%)
o Most of the other 4% is sulphure, Phosphorus, Calcium
Bonding
- Elements joined together through bonding
- Two types:
o Ionic bonds – involves swapping of electrons between atoms
o Covalent bonds
Atoms
- Nucleus contains protons and neutrons (+ will repel +) (+ will attract to -)
- Electrons
o In electron clouds or orbital around nucleus
o Each orbital can contain optimal electrons
- An ionic bond is the attraction between two
Covalent bonds
- Sharing a pair of valence electrons
find more resources at oneclass.com
find more resources at oneclass.com
Water
- Is a polar molecule
- Essential to life on earth
- Polarity of water results in hydrogen bonding
- Because of H bonding, water is:
o More structured than other liquids
o Gies ater properties that otriute to earths suitailit for life
- Properties of water:
o Cohesion
▪ Responsible to surface tension
▪ H bonds allow water to be pulled up inner water pipes fro roots to
leaves
o Moderation of temperature
o Expansion upon freezing
o Versatility as a solvent
- Water can dissociate
o Water can uncouple (dissociate) to form protons (H+) and hydroxyl anions
(OH-)
o Very weak, only partially occurs
o Concentration of H+ and OH- determines acidity and alkalinity
What is pH?
- Measure of acidity/alkalinity
- Scale 1-14
- 7 neutral
- <7 acid
- >7 alkaline
Why is pH important?
- Has the ability to alter the charge and hence shape of biological molecules
- Important as the shape of biological molecules allows it to function
Proteins
- Proteins are the most abundant molecules in cells after water
- Proteins account for up to 50% of the dry weight of a cell
o Polypeptide – polymers of amino acids
o Protein – one or more polypeptides folded and coiled into a specific
arrangement
- Proteins are polymers made up of amino acid monomers
How to identify amino acids
- Amino acids are the monomers or smallest components of a protein
- Atoms present:
o Carbon
o Hydrogen
o Oxygen
o Nitrogen
find more resources at oneclass.com
find more resources at oneclass.com
- There are 20 different amino acids that make up the proteins in cells
- We categorise the amino acids according to chemical properties and of their R chain
Polymerization of amino acids
- Dehydration reaction between the COOH group of amino acid in the growing chain
and the NH2 group of the incoming amino acid
Structure and function of proteins
- Proteins have many diverse functions – the tools of the ell
o Structure and support (tubulin)
o Storage (ovalbumin)
o Transport (haemoglobin)
o Hormonal (insulin)
o Receptors
o Contraction and motility (actin and myosin)
o Defence (antibodies – immunoglobulins)
o Enzymatic degradation (enzymes)
- Proteins can have such diverse functions because they have diverse structure
o There are four levels to protein structure:
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Biological part 2: the building materials of cells. Living things store and transmit information in form as dna. Compounds consist of elements: element: substance that cannot be broken down further, compound: substance that consists of two or more elements in a fixed ratio. In biology, most important 4 is hydrogen, oxygen, carbon, nitrogen. The major elements of life: carbon (19%, oxygen (65%, nitrogen (3%, hydrogen (10%, most of the other 4% is sulphure, phosphorus, calcium. Ionic bonds involves swapping of electrons between atoms: covalent bonds. Nucleus contains protons and neutrons (+ will repel +) (+ will attract to -) In electron clouds or orbital around nucleus: each orbital can contain optimal electrons. An ionic bond is the attraction between two. Polarity of water results in hydrogen bonding. Because of h bonding, water is: more structured than other liquids, gi(cid:448)es (cid:449)ater (cid:1008) properties that (cid:272)o(cid:374)tri(cid:271)ute to earth(cid:859)s suita(cid:271)ilit(cid:455) for life.
