biochemistry honors
TRANSCRIPT
Why is an understanding of chemistry important to someone studying biology?
All cells (and thus organisms) are composed of chemicals
All life processes involve a variety of chemical reactions
Reveals the complexity and elegance of life
What we will focus on in this presentation:
•Matter and Atoms
•Compounds
•Molecules
•Chemical Bonds
•Chemical Reactions
•The Unique Properties of Water
•Ions and Living Cells
•pH
Matter is anything that has mass and takes up space…
Made up of….
Atoms are the basic building blocks of matter
Our current model of atoms was first described by John Dalton in his work “The Atomic Theory”
Living Things Are Made of Matter
Compounds are substances which contain 2 or more different elements chemically combined in a fixed ratio
Atoms Elements and Compunds
Molecules are substances which contain 2 or more atoms, and are the most basic unit of a substance
Molecules can contain atoms of the same element or different elements
Molecules
Which of the following are molecules only and which are molecules and compounds?
CO2
O2
H2
H2SO4
HCl
N2
H2O
Molecule and Compound
Molecule
Molecule
Molecule and Compound
Molecule and Compound
Molecule
Molecule and Compound
Elements are substances made up of 1 kind of atom!
6 different elements make up 97% of the compounds that are found in living things
There are more than 100 known elements today
ProtonsProtons + charge, nucleus+ charge, nucleus
NeutronsNeutrons 0 charge, nucleus0 charge, nucleus
ElectronsElectrons - charge, orbit in the electron charge- charge, orbit in the electron charge
The # of protons in an atom determines its identity!The # of protons in an atom determines its identity!
One element differs from another by the number of protons in its nucleus
An element’s atomic number equals its number of protons
Element Number of Protons
Hydrogen
Carbon
8
7
1
6
Oxygen
Nitrogen
Sometimes atoms of the same element differ in their number of neutrons
Isotopes
Useful in biological research if radioisotopes
Review of Atoms Molecules and Compounds
Use the web resources listed below to help you study the topics covered so far:
http://csep10.phys.utk.edu/krogh_instructorCD/biology/ch2/animations/mod02_1.swf
http://www.phschool.com/science/biology_place/biocoach/biokit/chnops.html
http://www.chemthink.com
The Point of Reactions and Bonding is….The Point of Reactions and Bonding is….
Why Bonds FormWhy Bonds Form
Types of BondsTypes of Bonds
Reactions and EquationsReactions and Equations
Why Do Chemical Bonds Form??
Atoms are most stable when their outermost energy level is filled with electrons
To accomplish this stable state, atoms may share or transfer electrons among their nuclei and form bonds!
A Bohr Model can be used to determine the number of electrons in the outer shell of any atom!
Types of BondsTypes of Bonds
Chemical Bonds Form When Atoms Share or Transfer Electrons
Ionic Bonds Covalent Bonds
Forms when an electron (or electrons) is transferred from one atom to another
Forms when an electron (or electrons) is shared between atoms
Type of bond formed is dependent on the electronegativity of atoms involved
Ionic Bonds
Sodium wants to lose an electron to become most stableSodium wants to lose an electron to become most stable
Draw a Bohr Model of Sodium (Na) and Chlorine (Cl)
How does each atom become most stable with a full outer shell of electrons?
Chlorine wants to gain an electron to become most stableChlorine wants to gain an electron to become most stable
The strong attraction The strong attraction between the positive between the positive sodium ion and the sodium ion and the negative chloride ion negative chloride ion creates an ionic bondcreates an ionic bond
NaCl is common table salt
Covalent Bonds
A hydrogen atom wants to share its electron. For example, it A hydrogen atom wants to share its electron. For example, it can share its electron with another hydrogen atom or two can share its electron with another hydrogen atom or two hydrogen atoms can share their electrons with an oxygen atom hydrogen atoms can share their electrons with an oxygen atom which wants to share a total of two electrons.which wants to share a total of two electrons.
Shared Pair of Electrons
Covalent Bonds
If the electrons of a bond are shared equally a non-polar bond is formed
If the electrons of a bond are not shared equally a polar bond is formed
Polar Covalent Non-Polar Covalent
A chemical reaction involves the making or breaking of chemical bonds (ionic or covalent)
Chemical reactions are necessary for life:
• To establish stable atomic structuresTo establish stable atomic structures
• To form new molecules that cells needTo form new molecules that cells need
•To manage cellular energy (energy release, usage, and storage)To manage cellular energy (energy release, usage, and storage)
Chemical equations describe a chemical reaction
Chemical equations provide the following information:
• The different elements involved in the reaction
• The number of atoms involved in the reaction
• The reactants and products of the reaction
Reading a chemical reaction…..
Carbon dioxide and water react (in the presence of sunlight and chlorophyll) to produce carbohydrate (glucose) and oxygen
Other information from the equation….
# of molecules of reactants and products:
6 CO2
6 H2O
1 C6H12O6
6 O2
Other information from the equation….
The number of each kind of atom on each side of the equation
Reactants
C
O
H
Products
C
O
H
6
18
12
6
18
12
Review of Chemical Bonds and Reactions
Use the web resources listed below to help you study the topics covered so far:
http://csep10.phys.utk.edu/krogh_instructorCD/biology/ch2/animations/mod02_2.swf
http://www2.nl.edu/jste/bonds.htm
http://www.phschool.com/science/biology_place/biocoach/biokit/valence.html
http://www.chemthink.com
The Structure of WaterTwo hydrogen atoms are each joined to an oxygen atom by a single covalent bond
The weak attraction between the hydrogen atom of one molecule and a slightly negative atom within another molecule
The tendency of molecules of the same kind to stick to one another is called cohesion.
The type of attraction that occurs between unlike molecules is called adhesion.
Temperature Moderation
Because of hydrogen bonding, water has a better ability to resist temperature change than most other substances
•Oceans and large lakes moderate the temperatures of nearby land areas
•Water also moderates temperature through evaporation, such as when you sweat
Low Density of Ice
Review of Chemical Bonds and Reactions
Use the web resources listed below to help you study the topics covered so far:
http://csep10.phys.utk.edu/krogh_instructorCD/biology/ch3/animations/mod03_1.swf
http://www.phschool.com/science/biology_place/biocoach/biokit/polarity.html
http://programs.northlandcollege.edu/biology/Biology1111/animations/hydrogenbonds.html
When NaCl dissolves in water the ionic bonds are broken. The positive sodium ion is attracted to the slightly negative part of the water molecule and the negative chloride ion is attracted to the positive part of the water molecule.
When a covalent compound such as water is converted to ions, there are H+ and OH- ions in solution
The presence and abundance of these ions is critical to the functioning of the cell in terms of its biochemistry
The level of H+ and OH- ions in solution is measured by the….
pH Scale
A pH of 7 indicates an equal number of H+ and OH- ions in solution
A pH less than 7 indicates a solution with excess H+ ions = acid
A pH greater than 7 indicates a solution with excess OH- ions = base
The functioning of living cells can be affected by a change in pH
Because the very reactions of life cause pH changes, there is a need for cells to be able to regulate the pH of the intracellular fluid
Review of Chemical Bonds and Reactions
Use the web resources listed below to help you study the topics covered so far:
http://programs.northlandcollege.edu/biology/Biology1111/animations/dissolve.html
http://www.johnkyrk.com/pH.html
http://www.mhhe.com/physsci/chemistry/essentialchemistry/flash/buffer12.swf