What is Biochemistry?

Chemical Context of Life Key Elements of Life 92 naturally existing elements on Earth 25 play a role in the chemical processes of life 96 percent of all biological matter contain: carbon (C) oxygen (O) hydrogen (H) nitrogen (N) ALL organic molecules contain carbon

Concept check: 1. Explain why table salt is a compound, while the oxygen we breath is not. 1. What four chemical elements are most abundant in the food you ate yesterday?

Atomic structure

Stable

Unstable

Uses of Isotopes Radioisotopes are radioactive and break down, emitting radiation, over time. Radioisotopes can be used to help understand chemical and biological processes in organisms. They can also be used in radiometric dating which is useful in determining the age of fossils

For Example: A solution of phosphate, containing radioactive phosphorus-32, is injected into the root system of a plant. Since phosphorus-32 behaves identically to that of phosphorus-31, the more common form of the element, it is used by the plant in the same way. A Geiger counter is used to detect the movement of the radioactive phosphorus-32 throughout the plant. This information helps scientists understand the detailed mechanism of how plants utilized phosphorus to grow and reproduce.

For Example Brachytherapy is a form of radiation therapy where radioactive isotopes in the form of small pellets (called seeds) are inserted into cancerous tumours to destroy cancer cells while reducing the exposure of healthy tissue to radiation. It is currently approved for treatment of prostate cancer and cancers of the head and neck. There are also studies underway to see whether it can be used in the treatment of lung cancer.

Radioactive Decay: Using the rate at which radioactive isotopes break down to determine the age of a specimen

Uses of Stable Isotopes How Stable Isotopes WorkExamples of Uses

Valence electrons are those electrons that are available for bonding. The electrons in the outermost s and p orbitals Chemical Bonding

Bonds are formed when: electrons are shared or exchanged between atoms. 1. Intermolecular Bonds Bonds formed between molecules 2. Intramolecular Bonds Bonds formed between atoms WITHIN a molecule

Intramolecular Bonds: 1. covalent bonds sharing of electrons between atoms Atoms are shared between non-metals Double and triple bonds can result if 2 or 3 pairs are shared a) polar covalent bonds unequal sharing of electrons between atoms b) non-polar covalent bonds equal sharing of electrons between atoms 2. ionic bonds electrostatic attraction between ions upon electron transfer….occurs b/w a metal and a non-metal Na  +  Na + [] Cl  Cl  

Intramolecular Bonds: 1. covalent bonds sharing of electrons between atoms Atoms are shared between non-metals Double and triple bonds can result if 2 or 3 pairs are shared a) polar covalent bonds unequal sharing of electrons between atoms b) non-polar covalent bonds equal sharing of electrons between atoms 2. ionic bonds electrostatic attraction between ions upon electron transfer….occurs b/w a metal and a non-metal Na  +  Na + [] Cl  Cl  

Electronegativity nonpolar bond: electrons are shared equally HCl: polar bond: electrons are shared unequally because of the difference in electronegativity. H 2, Cl 2 :

Bond Polarity Determined by the difference in electronegativity between elements. The greater affinity for electrons, the greater the electronegativity of the element. Noble gases have En = 0, fluorine (F) is the most highly electronegative element En = 4.0 Nonpolar ionic Increasing polar covalent increasing ionic characteristics Example: The bond between hydrogen and oxygen is polar covalent. E n of H = 2.1, E n of O = 3.5 therefore ∆E n = = 1.4 Since 1.4 is between 0 and 2.0, the bond is polar covalent

Intermolecular Bonds (van der waals forces) Bonds or ‘interactions’ between molecules They are much weaker than intramolecular bonds. They determine the physical state of substances at a given temperature and pressure They are broken when solids melt into liquids or when liquids evaporate into gases There are three types: London forces, dipole-dipole forces, hydrogen bonds

Intermolecular Bonds cont: 1. London forces (weakest) attraction between noble gas atoms and non-polar molecules only occur when atoms and molecules are very close together Form because of temporary random and unequal distribution of electrons around the nuclei of atoms 2. dipole-dipole interactions attraction of  + and  - ends of polar molecules 3. hydrogen bonding (H-bonding) (strongest) special type of dipole-dipole interaction generally occur when hydrogen bonded to O, N Hydrogen bonds hold water molecules together, and this gives water its unique properties

Which is which?

Homework: 1. Rd. Chapter 1.1 – focus on Water and Acid and Bases (pg. 16 – 22) (skip molecular shape pg. 15) 2. Answer questions 4, 7-10, Together – page 10 #1

An important life component

Properties of water It is a universal solvent – most substances dissolve in it than any other liquid This is due to its polarity It has partial positive and negative charges, therefore other polar molecules or ions can attach to it. Non polar molecules e.g. oil are hydrophobic, polar molecules that form hydrogen bonds with water are hydrophilic Its physical and chemical properties are a direct result of its simple composition and structure

Properties of Water