Biology Unit 4

Chemistry of Life

Elements

• Everything in our universe that has a mass and a volume is made of matter.

• Matter in its purest form is an element.

• There are 118 elements on the periodic table, each of which is distinguished by its atomic number (number of protons)

Elements in Living Things

• There are 5 elements that make up about 96% of living things.

• They are:• Carbon• Hydrogen• Nitrogen• Oxygen • Phosphorus• Sulfur

• Remember them with “CHNOPS”

Atoms

• Elements are all made of the same type of atoms.

• Atoms have protons and neutrons in the nucleus.

• Orbited by negative electrons

• Electrons exist in energy levels around an atom.

Electron Energy Levels

• The first energy level can hold 2 electrons.

• The second can hold 8

• The third can hold 18

• In order to be stable, atoms want to have 8 electrons in their outer shells.

Isotopes

• Although every element has a specific number of protons, they can have different numbers of neutrons.

• Atoms of the same element with differing numbers of neutrons are called isotopes.

• Atomic mass from the periodic table is a decimal

because it is an average.

How to Find Subatomic Particles

• Protons=Atomic number on periodic table

• Neutrons= Rounded atomic mass- protons

• Electrons= Protons if atom is neutrally charged

• How many protons, neutrons, electrons in a neutral Helium atom?

Compounds and Bonding

• Multiple atoms of similar and different elements can bond together to form compounds.• Examples: H2O, CO2, NaCl

• Chemical bonds are formed and broken through chemical reactions.

Ionic vs. Covalent Bonds

• Covalent compounds are formed when atoms share electrons.• Most compounds in the body are formed this way

• Ionic compounds are formed when charged atoms transfer electrons.

• Charged atoms are called ions.

• Positive ions are called cations. “Cat Ion”

• Negative ions are called anions. “An Ion”

Charges on Ions

• Ions have specific charges based on their groups (columns) on the periodic table.

Number of Valence Electrons

• Valence electrons are electrons on the outermost energy level of an atom.

• Magic # is 8.

• You can find out how many valence electrons an element has by looking at group number on periodic table.

• IA has 1, IIA has 2, IIIA, has 3, etc.

How Ionic Compounds Form

• Charges need to balance to make 0.

• Ex: Na+Cl, Ca+F, K+O

• Named by leaving the cation as is and changing the ending on the anion to “ide”

• Ex: NaCl Sodium Chloride

Name The Compounds

• KCl

• Li2S

• NaF

• MgBr2

Chemical Reactions

• Chemical reactions occur constantly in the body.

• These reactions are called metabolism.

Chemical Equations

• We can represent chemical reactions by writing chemical equations.

Law of Conservation of Mass

• The law of conservation of mass says that mass can never be lost or gained during a chemical reaction.

• Because of this, we have to make sure we balance our chemical equations.

How to Balance an Equation

• You can balance a chemical equation by changing the coefficients (big numbers) that come before each product or reactant.

• It works like the distributive property in math. Each compound gets multiplied by the coefficient in front of it.

• YOU CAN NEVER CHANGE THE SUBSCRIPT!!!!!!!

Example

• Balance these equations:

H2 + O2 -> H2O

K+Cl2 -> KCl

The Molecules of Life

• Known as organic molecules

• Not the organic you see at the grocery store

• All organic molecules contain carbon

Carbon Bonding

• Carbon is special because it is so easy to bond with.

• Each carbon atom can form up to 4 bonds.

• Carbon can even bond more than once with the same atom.

• These are called double and triple bonds.

Polymers

• Many carbon based molecules can form polymers. Polymers are giant molecules that are made up of smaller molecules.

• The smaller molecules that make up polymers are called monomers.

Condensation vs. Hydrolysis

• Polymers are formed by a chemical reaction called condensation.

• Condensation causes 2 monomers to come together while a water molecule is released.

• Hydrolysis happens when a water molecule breaks apart a polymer and uses the H and OH from the water to fill in the gaps.

4 Classes of Biomolecules

• Carbohydrates

• Lipids

• Proteins

• Nucleic Acids

Carbohydrates (sugar and starch)

• Used by cells to provide energy.

• 4 calories per gram

• Monomers: Monosaccharides

• Multiple monomers can form polysaccharides.

• Polysaccharides form through condensation.

• 1:2:1 ratio of Carbon to hydrogen to oxygen

Carbohydrate Examples

• Examples of monosaccharides: Fructose and Glucose• Found in fruits, used for energy by both animals and plants

• Examples polysaccharides: Cellulose, glycogen• Very large molecules, take a long time to break down

• Animals store glycogen in their livers for back up energy.

• Plants use cellulose to help provide structure.

Lipids (fats)

• Large biomolecules made of mostly carbon and hydrogen with a little bit of oxygen.

• Non-Polar: Means they will not dissolve in water

• Monomer: Fatty acids

• 9 calories per gram

Lipids Examples/Uses

• Fats, oils, waxes, steroids

• Used for energy storage/insulation in many animals

• High in energy

• Major component in cell membranes

Proteins

• Made up of carbon, hydrogen, oxygen, nitrogen, and sometimes sulfur.

• Essential for all life

• Monomer: Amino Acids

• Come together to form proteins. Held together by peptide bonds.

• 4 calories per gram

Proteins Uses/Examples

• Come in a huge variety of shapes and sizes.

• Shape determines function.

• Building blocks of many structural components in living things.• Muscle tissue, assist with immunity, transport oxygen, carry out chemical

reactions.

• Used as enzymes!

Enzymes

• Life as we know it would not be possible without enzymes.

• Enzymes speed up reactions exponentially but do not get used up in the reaction.

• The activity of enzymes depends on pH and temperature.

• Every enzyme has an active site where a substrate must bind in order to speed up the reaction.

Active Site and Substrate

Nucleic Acids

• Made up of carbon, hydrogen, oxygen, nitrogen, and phosphorus atoms.

• These atoms are arranged into a nitrogenous base, a simple sugar, and a phosphate group.

• Monomer: Nucleotides

Nucleic Acids: Examples and Uses

• DNA and RNA

• DNA contains the instructions to form all of an organism’s enzymes for structural proteins.

• DNA determines how an organism looks and acts.

• RNA is used by the body to make a copy of DNA for use in making proteins.

Water, Solutions, and pH

Water is Polar

• Water is a covalently bonded molecule.

• Sometimes, covalently bonded molecules do not share electrons equally. This makes them polar.

• Polar molecules have both positive and negative parts.

• This allows them to make solutions very easily.

Hydrogen Bonds

• Water is attracted to itself through hydrogen bonds.

• This means that the negative oxygen is attracted to the positive hydrogen.

• Causes surface tension and capillary action.

High Specific Heat of Water

• Water is very resistant to temperature change.

• It takes more energy to change the temperature of water than it does to change most other liquids.

• Allows cells to maintain homeostasis.

• Why do you think coastal cities usually have milder temperatures than those inland?

Water Expands when it Freezes

• Water is one of the few substances that becomes less dense when it becomes a solid.

• It also expands when it becomes solid.

• This is helpful for breaking up rock and returning nutrients to the soil.

• What animals might benefit from this property of water?

Diffusion in Water

• Particles are in constant random motion.

• Diffusion is the net movement of particles from high concentration to low concentration.

• High temp can increase rate of diffusion.

• Eventually, concentration will be even. This is called dynamic equilibrium.

• Cells use diffusion to move substances in and out.

Water and Solutions

• The polarity of water makes it perfect for dissolving other compounds.

• Because it has both negative and positive charges, it can bond to both parts of other polar molecules, creating weak bonds that allow solutions to be made.

• See example on board:

Water and pH

• Acids are substances that release H+ ions in water. These substances have a pH below 7.

• More H+ = more acidic= lower pH

• Bases are solutions that release OH- ions in water. They have a pH above 7.

• More OH- = more basic= higher pH

Atoms that release fewer H+ ions that pure water would be classified as:

Example pH Scale