Post on 06-Jan-2018
description
transcript
Chemistry Basics
Elements, Molecules and Compounds
matter• any object around us is made of
tiny particles called atoms• atoms are made of protons,
neutrons, and electrons
• every element has its own type of atoms
ex. carbon ex. hydrogen
• isotopes are atoms of the same element that have different number of neutrons, ex.
Pet scans: radioisotopes
• Unstable isotopes are radioactive and are called radioisotopes
• When atoms join together they can form molecules
molecules• combinations of atoms held together by
strong chemical forces of attraction (covalent bonds)
• molecules that contain atoms of the same element are called molecular elements, ex. O2
• molecules that contain atoms of different elements are called compounds, ex. H2O
The elements of life• living things are mostly (98%) made of 6
elements:C – carbonH – hydrogenO – oxygenP – phosphorusN – nitrogenS – sulphur
-each element makes a specific number of bonds with other elements
Carbon: 4 bonds
Hydrogen: 1 bond
Oxygen: 2 bonds
Phosphorus: 3 bonds
Nitrogen: 3 bonds
Sulphur: 2 bonds
Biochemistry
• Field that bridges chemistry and biology• Deals with properties and interactions of
biologically important molecules
• Many of the molecules of life are organic: contain carbon and hydrogen
SO WHAT'S SO SPECIAL ABOUT WATER?
1) two-thirds of Earth are covered by it (97% of that is sea water)
2) ours is the only planet in the Solar System where water can exist in its liquid state
3) all life is water-based: we are 75% water!
Structure of Water1) water has a very
slight charge to it, where the O is more negative and the H
is more positive
2) this slight charge difference makes water polar
3) Polar molecules can form hydrogen bonds with other polar molecules
• Intramolecular bonds: bonds within a molecule, ex. covalent, ionic
• Intermolecular interactions: bonds between molecules, ex. hydrogen bonding and hydrophobic/hydrophilic interactions
• Polarity of water:
• Since water is polar it can dissolve other charged or polar substances (ex. salt) but not uncharged or nonpolar substances, ex. Oil
• [remember: like dissolves like]
hydrophilic molecules-like water, can be dissolved in it-are polar
hydrophobic molecules-don’t like water, can’t be dissolved in
it-are non-polar- the natural clumping of non-polar
molecules in water plays a key role in how biologically important molecules are shaped!
Ions in biological systems
• an atom can obtain a stable valence shell by losing or gaining electrons, rather than sharing:
• when an atoms gains/loses an electron it becomes charged, and forms an ion
• cation: a positive ion
• anion: a negative ion
• substances that form ions (ionic compounds) are almost always considered in terms of ions, since they are in an aqueous environment
So…
• In biology STRUCTURE DICTATES FUNCTION
• Since molecules will come together depending on how hydrophobic/hydrophilic hydrogen bonding will determine the function of many large biological molecules: MACROMOLECULES