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Chapter 3 – Chemistry of Life
How is Chemistry related to Biology?
Four elements – carbon (C), oxygen (O), hydrogen (H), and nitrogen (N) make up 96% of living matter.
Review of the Atom
Atoms – the basic smallest unit of all matter
Subatomic Particle Charge Location
Atoms are electrically neutral.
o # protons = # electrons
Protons + Center of atom (nucleus)
Neutrons 0 Center of atom (nucleus)
Electrons - “cloud” around the nucleus
Elements
Pure substance made of only one kind of atom
Each represented by a symbol
Differ in the number of protons
Simplest element, hydrogen
Contains 1 proton, 1 electron
Neutrons usually equal to number of protons
Atoms that have different #’s of neutrons are called isotopes
The Periodic Table
The Periodic Table
Atomic number = number of protons
Atomic mass = protons + neutrons
Atomic Number
Element
Atomic Mass
Bonding
Compounds and molecules form by the chemical combination of two or more elements.
The number of valence (outermost) electrons determines the chemical activity and bonding ability of an atom.
Atoms combine (bond) to fill these outermost shells.
First shell is full with 2 electrons.
The remaining shells are “full” with 8 electrons.
Covalent Bonds – share valence electrons
Non-polar Covalent Bonds – share electrons equally
Polar Covalent Bonds – share electrons unequally results in the two ends
(poles) having slight positive and negative charges.
Ionic Bonding
Ionic bonds form between atoms when there is a transfer of electrons between one another. When an atom gains an electron… becomes a (-) ion. When an atom loses an electron… becomes a (+) ion.
Opposite charges attract, forming the bond.
Sodium atom (Na) Chlorine atom (Cl) Sodium ion (Na+) Chloride ion (Cl-)
Protons +11 Electrons -11 Charge 0
Protons +17 Electrons -17 Charge 0
Protons +11 Electrons -10 Charge +1
Protons +17 Electrons -18 Charge -1
Transfer of electron
Hydrogen Bonding
Hydrogen Bond – a weak attraction between two polar molecules
The slight positive end of one polar molecule is attracted to the slight negative end of another polar molecule.
Example: WATER!!!
Water
Importance:
Living things are ~75% water.
Water can absorb and store large amounts of energy (good insulator)
Water allows organisms to control their temperature (homeostasis)
Main characteristics 1. High surface tension
(cohesion) 2. Capillary action
(adhesion) 3. High heat of
vaporization 4. Resists temperature
change 5. Expands when it
freezes 6. Universal solvent
Cohesion
Cohesion – the attraction of water to itself
Because water is a polar molecule, it easily attracts other water molecules.
Surface tension
Attraction of water molecules to one another causes it to act like a stretched film over the surface of the water.
Adhesion
Attraction of water to other substances
The clinging of one substance to another.
Capillary action – movement of water up thin tubes Example – plants and the movement of water against
gravity!
High Heat of Vaporization
It takes a lot of energy to make water evaporate.
Importance: evaporative cooling – as water evaporates, the surface of the liquid that remains behind cools down
When sweat evaporates from skin, it draws away the heat to help cool the body.
Homeostasis!
Resists Temperature Change
Water changes its temperature less when it absorbs or loses a given amount of heat.
Significance… Homeostasis -beneficial in helping to maintain body
temperature as well
Coastal areas – a large body of water can absorb and store a huge amount of heat from the sun in the daytime and during the summer. At night and during the winter, the gradually cooling water can warm up the air. Example: Chicago and Lake Michigan
Water Expands When it Freezes
Water is less dense as a solid than a liquid, so ice floats in liquid water.
When water freezes, it expands because the hydrogen bonds keep the molecules at “arm’s length” and create a crystalline structure.
Important in the fitness of the environment. If ice sank, bodies of water would freeze solid, making life impossible.
Universal Solvent
Solution – a mixture in which all of the components are evenly distributed. Solvent – dissolves the solute (water) Solute – the substance that is dissolved
“Likes dissolve Likes” Water can easily dissolve other polar substances. Nonpolar substances do not dissolve in water. Oil
and water.
Acids and Bases
Acids – form hydrogen ions (H+)when dissolved in water
Bases – form hydroxide ions (OH)when dissolved in water
pH scale is based on the concentration of hydrogen ions in solutions Values between 0-14
Pure water 7
Acids <7
Soda, orange juice, vinegar, tomatoes, lemon, lime
Bases >7
Antacids, glass cleaner, baking soda
3.3 Carbon Compounds
Large molecules that contain carbon and hydrogen atoms
4 carbon compounds in all living things…
1) Carbohydrates
2) Lipids
3) Proteins
4) Nucleic Acids
Making Macromolecules
Monomers – smaller units (subunits) that join together to make larger molecules
Polymers – a long molecule consisting of many similar or identical building blocks
Monomer 1
Monomer 2
Monomer 4
Monomer 3
Polymer
Carbohydrates Elements
Monomers/ Basic Units
Functions
Location in Cell
Examples
C, H, O (1:2:1)
sugars
Short-term energy for cells, structural support, cell recognition
•Simple sugars/ monosaccharides (glucose, fructose) •Polysaccharides (cellulose, starch, glycogen)
Mitochondria
Carbohydrates, cont.
In some organisms, polysaccharides function as storehouses of energy
Starch – made by plants
Glycogen – made by animals
Both made of hundreds of linked glucose molecules
Cellulose – provides structural support for plants
Humans cannot digest cellulose
You cannot digest wood, mostly cellulose
Lipids
Elements
Monomers/ Basic Units
Functions
Location in Cell
Examples
C, H
Glycerol & Fatty Acid
Long-term energy for cells Water-proofing
Insulation Make up membranes around cells
Fats, Oils, Waxes, Phosholipids
Biological Membranes
Fats comparison
S -All carbon atoms in the chain are bonded to two hydrogen atoms (except the carbon at the end)
U-Some of the carbon atoms are linked by a “double” covalent bond, each with only one hydrogen atom-Produces kinks in the chain
Nucleic Acids
Elements
Monomers/ Basic Units
Functions
Location in Cell
Examples
C, H, O, N, P
Nucleotides
Store and transmit hereditary info
DNA RNA
Nucleus
Nucleic Acids
Nucleotide has 3 parts: a sugar, a base, and a phosphate group
Phosphate
Sugar
Base
Proteins
Elements
Monomers/ Basic Units
Functions
Location in Cell
Examples
C, H, O, N
Amino acids
Control reaction rates, Regulate cell processes, Transport substances in cells, Energy carriers
Enzymes Make up parts of hair, nails, skin
In membranes and cytoplasm
Proteins
20 amino acids are found in proteins
Some are polar, some are nonpolar
Some electrically charged, some are not
Folds help to compact the shape
Some are enzymes that promote chemical reactions
Some have structural functions
Collagen
Skin, ligaments, tendons, bone
Antibodies – defend against infection
Hemoglobin – carries oxygen from lungs to body tissues
PROTEINS ARE EVERYWHERE AND IN EVERYTHING!!!!
Proteins, cont’d
Carbon Compounds
include
Which are made of
which contain
Which are made of Which are made of Which are made of
which contain which contain which contain
Section 2-3 Concept Map
Carbohydrates Lipids Nucleic acids Proteins
Simple sugars
Glycerol/3 fatty Acid Subunits
Nucleotides
Amino Acids
Carbon, hydrogen,
oxygen
Carbon, hydrogen,
Carbon,hydrogen, oxygen, nitrogen,
phosphorus
Carbon, hydrogen,oxygen,
nitrogen,
Section 4 – Energy and Chemical Reactions
Energy is the ability to move or change matter
Exists in many different forms
Light, heat, chemical energy, mechanical, energy, and electrical energy, to name a few
Can be converted from one form to another
Energy can be stored or released by chemical reactions
Chemical Reactions
A chemical reaction is a process that changes one set of chemicals into another set of chemicals. Involves the breaking of bonds in the reactants and
the formation of bonds in the products.
Reactants – the elements or compounds that enter the reaction
Products – the elements or compounds that are produced by the reaction.
Reactants ----------> Products
2H2 + O2 --------> 2H2O
Energy and Chemical Reactions
Energy releasing = exothermic
Energy absorbing = endothermic
Catalysts
A catalyst is a substance that speeds up the rate of a chemical reaction.
Catalysts work by lowering the activation energy of a chemical reaction. Activation energy – the
amount of energy required to get the reaction started (to break the bonds in the reactants)
Example: Enzymes are proteins that act as catalysts in cells.
Enzyme Specificity
Substrate – substance on which an enzyme acts during a chemical reactions
Enzymes act only on specific substrates
EX – amylase assists in the breakdown of starch to glucose
Starch → glucose by amalyse
• Starch is amalyse’s substrate
Shape determines activity
Enzyme is typically a large protein with one or more deep
folds called active sites
Enzyme only acts on a specific substance because only that substrate
fits into its active site.
Enzyme Action
Factors in Enzyme Activity
Operate most efficiently within a certain range of temperatures
Outside of range temperatures can break or strengthen some of the enzyme’s bonds, changing it shape
Operate best within a certain pH value
Can cause bonds in the enzyme to break, reducing the effectiveness
ATP
Adenosine triphosphate
Energy Molecule of the cell
Single nucleotide with two extra energy-storing phosphate groups
When food molecules break down, some of the energy is stored temporarily in ATP.