Post on 26-Dec-2015
The Chemistry of Life
Life depends on chemistry
Eat food, Breathe in oxygen – chemical reactions allow your body to use these substances
Matter
Just as an architect needs to understand the materials used to build a skyscraper
…biologists need to understand the chemical building blocks of life.
Matter
Matter – anything that takes up space and has mass
Mass – the amount of matter a substance contains
This is NOT the same as weight!
Matter
The international unit of measure for mass is the kilogram
1kg is equal to the mass of a single cylinder of platinum kept by the international committee of weights and measure
Mass
A Greek philosopher If you break and object in half, are both
halves still the same thing? If you break a piece of chalk, are the two
pieces still chalk?
Democritus
Atom – the basic unit of matter Everything is made of atoms An atom cannot be broken and still be the
same thing
The Atom
Atoms are made up of even smaller parts Protons, Neutrons, Electrons Protons are positively charged particles Neutrons have no charge Electrons are negatively charged particles
Subatomic Particles
Element – a pure chemical substance that consists entirely of one type of atom
We know of over 100 different elements Only about 2 dozen are commonly found in
living things
Element
Elements are represented by letter symbols
H = hydrogen C = carbon O = oxygen Na = sodium He = helium
Element
Elements are determined by the combination of protons, neutrons, and electrons in their atoms
Ex. Hydrogen is the first element on the
periodic table H has 1 proton and 1 electron
Element
Isotope – atoms of an element that have a different number of neutrons
A change in the number of neutrons alters the atomic mass
Isotopes are important to many chemical processes in life
We’ve already learned they are useful when using radioactive dating
Isotope
Carbon dating is one of the most accurate ways to determine the age of organic material
C has an atomic mass of 12 C14 has an atomic mass of 14 - it is an
isotope
Radiocarbon Dating
Elements are usually found combined with other elements
Chemical Compound – substance formed by the combination of chemical elements in defined proportions
H2O, NaCl, C6H12O6
Chemical Compounds
Physical and chemical properties of compounds are usually very different from the individual elements
Take Sodium (Na) and Chlorine (Cl) for example…
Chemical Compounds
Compounds are formed when elements are chemically bonded◦ The sole of your shoe is bonded to the upper◦ A book cover is bonded to the pages
A reaction has occurred and the two types of atoms are now chemically linked together
http://youtu.be/afRlDab1_e8
Chemical Compounds
Ionic bond – one or more electrons are transferred from one atom to another
Covalent Bond - electrons are shared between atoms
Chemical Bonds
http://youtu.be/QqjcCvzWwww
http://www.youtube.com/watch?v=_M9khs87xQ8
Chemical Bonds
Van der Waals forces – weak attraction between oppositely charged atoms
Electrons are not shared or transferred Kind of like magnets!
Van der Waals
H2O 2 hydrogen and 1 oxygen
Water!
Polarity – having poles or a positive and negative side
Water is polar because there is an uneven distribution of electrons between the oxygen and hydrogen atoms
Water is Polar
Polar molecules can attract each other
Hydrogen bond – the attraction between water molecules
Hydrogen bonds
Cohesion – attraction between molecules of the same substance◦ Water is the best example! It sticks together!
Adhesion – attraction between molecules of different substances
Adhesion and Cohesion
Why can this spider walk on top of the water?!
You can mix things without chemically bonding them!
Mixture – material made of two or more elements physically mixed together
NOT chemically combined!
Solutions and Suspensions
Solution – a mixture of two or more substances that are evenly distributed
Ex. Salt dissolved in water!
2 components of a solution◦ The Solute◦ The Solvent
Solutions
Solute – what is being dissolved
Solvent – what is doing the dissolving (most of the time this is water)
Solute
When NaCl dissolves the Na and the Cl atoms are pulled apart by the water molecules forming ions
Ion - an atom or molecule with a net electric charge due to the loss or gain of electrons
http://youtu.be/EBfGcTAJF4o
Ions
When a substances does not dissolve in water
Instead it separates into pieces so small they do not settle
Suspension – mixture of water and materials that do not dissolve
Ex. Dirt/sand in water
Suspension
Acids vs. Bases
We already know carbon is an important element
Carbon is found in each and every living thing
There is an entire branch of chemistry for just Carbon called Organic Chemistry
Carbon Compounds
Carbon can bond to other carbon atoms Carbon can link into long chains …or form rings! Carbon can form millions of different
complex structures
Carbon Compounds
Organic compound must have BOTH carbon and hydrogen
Ex. ◦ CH4; C6H12O6
Organic vs. Inorganic
Many molecules in living things are so large we call them macromolecules◦ Macro = large
Monomers – small unit that can join together with other units
Polymer – large compound formed from many smaller monomers
Macromolecules
We can group organic compounds found in living things into 4 categories
◦Carbohydrates◦Lipids◦Nucleic Acids◦Proteins
Macromolecules
Carbohydrate – compound made of C, H, and O atoms; major source of energy for living things
Carbohydrates are polymers The monomers that make up carbohydrate
molecules are sugars
Carbohydrates
Carbohydrates are broken down into glucose molecules in living things
Glucose is the source of energy for all your body cells
Carbohydrates
Lipid – macromolecule made of mainly C and H
Fats, oils, and waxes
Lipids are used to store energyImportant parts of membranes and waterproof coverings
Lipids
Lipids are long carbon hydrogen chains
Saturated and unsaturated fats You may have seen these terms on food
labels
Lipids
Saturated vs. Unsaturated
Nucleic Acid – macromolecule containing C, H, O, N, and P
Store and transmit genetic info
Two kinds:◦ DNA◦ RNA
Nucleic Acids
Nucleic acids are polymers of nucleotides
Nucleic Acid – a sugar, a phosphate, nitrogenous base
Nucleic Acids
Proteins – macromolecule made of C, H, O, and N
Needed for growth and repair Made of amino acids
Proteins
Proteins can have up to 4 levels of organization◦ Primary◦ Secondary◦ Tertiary◦ Quaternary
Proteins
Primary protein organization = the initial chain of amino acids
Peptide bond – the bond between amino acids to form the long chain we call a protein
Primary Level
Secondary structure consists of two shapes◦Alpha helix◦Beta sheets
Caused by hydrogen bonding
Secondary Level
Three dimensional structure of a single protein molecule
Caused by hydrophobic interactions
Tertiary Level
3D structure with multiple protein subunits Held together by disulfide bonds
Quaternary Structure
Some proteins help to control reactions and cell processes
Enzyme – protein that can speed up reactions
Other proteins build bone and muscle Some help with transport
Proteins
There are two main types of chemical bonds◦ Ionic Bonds◦ Covalent Bonds
Ionic bonds transfer electrons
Covalent bonds share electrons
Chemical Bonds
When a molecule with an ionic bond dissolves in water…
The molecule breaks into a positive and negative ion
NaCl Na+ and Cl-
Ions
Living things are all made of chemical compounds
Chemistry is also how life works and what it does!
◦ Growth, reproduction, movement
Chemical Reactions
Chemical Reaction – process that changes, or transforms one set of chemicals into another
Chemical reactions drive life processes!
Chemical Reaction
Some reactions are slow
Some reactions are fast
Reactants – the chemicals that enter into a chemical reaction
Products – the chemicals that are produced by the chemical reaction
Reactants Products
*chemical reactions always involve changes in the chemical bonds
Chemical Reactions
H2O + CO2 + sunlight C6H12O6 + O2
K2CO3 + 2HCl --> 2KCl + H2O + CO2
Chemical Reaction
Energy can be either released or absorbed whenever chemical bonds form or are broken
Living things carry out chemical reactions that require energy
Organisms need a source of energy◦ Plants have the sun◦ Animals eat food
Energy in Reactions
Activation energy – the energy needed to start a chemical reaction
Energy in Reactions
Remember! Some reactions give off energy…and some
absorb energy!
Energy in Reactions