Bio 134

Ch. 6

6.1Atoms, Elements, and

Compounds

P. 148-155

Main Idea

Matter is composed of tiny particles called atoms

Atom

Building blocks of matter

Structure of an Atom

Nucleus – the center of the atom where protons and neutrons are located

Protons – positively charged particles Neutrons – particles that have no

charge Electrons – negatively charged

particles located around the nucleus

Inside an Atom

Element

A pure substance that cannot be broken down into other substances by physical or chemical means

Are made of 1 type of atom

Isotopes Atoms of the same element that

have different numbers of neutrons Add the number of protons and

neutrons

Compounds

Are a pure substance formed when two or more different elements combine

H2O

– 2 hydrogens, 1 oxygen

What are 2 characteristics of compounds?

1. Always formed in a fixed ratio– Example: Water – H2O – always has 2 H

for every 1 O

2. Can only be broken down into specific parts by a chemical reaction

Chemical Bond

The force that hold two substances together– Example: water (H2O), salt(NaCl),

methane (CH4)

Chemical Bond

They travel around the nucleus in areas called energy levels

A partially filled energy level is not stable. Atoms become more stable by losing e- or

attracting e- from other atoms

Covalent Bonds

a chemical bond that forms when e- are shared

Molecule

Substances with covalent bonds– Example: water (H2O)

Covalent bonds can be single (sharing only 1 pair of e-) double (sharing 2 pairs of e-) or triple (sharing 3 pairs of e-)

Ionic Bond

Ion – an atom that has lost or gained one or more electrons and has a positive or negative charge

Ionic Bonds – when + charged ions bond with – charged ions

NaCl Ionic Bond

Van der Waals Forces

When molecules come close together, the attractive forces between slightly positive and negative regions pull on the molecules and hold them together.

The strength of the attraction depends on the size of the molecule, its shape, and its ability to attract electrons

End of 6.1

6.2 Chemical Reactions

p. 156 - 160

Main Idea

Chemical reactions allow living things to grow, develop, reproduce, and adapt

Reactants and Products

Chemical reaction – the process by which atoms or groups of atoms in substances are reorganized into different substances

-Chemical bonds are broken down or formed

How do you know a chemical reaction has taken place? Color change Production of heat Production of light Formation of a gas, solid, or liquid

Example of a chemical reaction:

Chemical Equations

Reactants – the starting products are always on the left side of the arrow

Products – the substances formed during the reaction are always on the right side of the arrow

Reactants Products

Balanced Equations

Law of Conservation of Mass – states that matter can not be created nor destroyed

The number of atoms of each element on the reactant side must be equal to the number of atoms of the same element on the products side

Why do we balance chemical equations? Because matter can not be created nor

destroyed

Paper Burning Demo

Paper Burning Check…

How do we know a reaction took place?

What happened when we covered the paper with the glass cover?

What was needed in order for the paper to burn?

Energy of Reactions

Activation Energy – the minimum amount of energy needed for reactants to form products in a chemical reaction– Example – a candle will not burn until you

light the wick, the flame provides the activation energy for the reaction of the substances in the candle

Types of Reactions

Exothermic reactions – it releases energy in the form of heat

Types of Reactions Endothermic reactions – it absorbs

heat energy

Back to Paper burning…

What was the activation energy that started the reaction of the paper burning?

Was it an endothermic or exothermic reaction?

Enzymes

Catalyst – a substance that lowers the activation energy needed to start a chemical reaction

Enzymes – are biological catalysts that speed up the rate of chemical reactions in biological processes

Enzyme Activity

Substrates – the reactants that bind to the enzyme

Active site – the specific location where a substrate binds on an enzyme

Substrates and Active Sites

What are the factors that affect Enzyme Activity? pH Temperature Other substances

End of 6.2

6.3Water and Solutions

P. 162 - 165

Why is water so important in

Biology?

Main Idea

The properties of water make it well suited to help maintain homeostasis in an organism

Polar molecule

Molecles that have an unequal distribution of charges and have oppositely charged regions

Example of polarity – the reason water and oil don’t mix – water is polar and oil is not

Example of polarity – Water and Oil

Hydrogen bond

A weak interaction ivolving a hydrogen atom and a F, O, or N atom

Is a strong type of van der Waals interaction

Hydrogen Bonding

Mixture

Combination of two or more substances in which each substance retains its individual characteristics

Examples of mixtures:

Homogeneous mixture

A mixture that has a uniform composition throughout

Examples:

Solution

When all of the components are evenly distributed throughout– Example: saltwater

Solvent

The substance in which another substance is dissolved

Example: water

Solute

The that is dissolved in the solvent

Example: salt

Heterogenous mixture

The components remain distinct, you can tell what they are individually

Example: a salad – has lettuce, vegetables, dressing – each ingredient remains independent

Suspension

When a particles in a liquid are not dissolved, and remain moving

Colloid

a heterogeneous mixture in which the particles do not settle out– Example – milk – protein and fat don’t

settle out

Blood

Solution – blood is a solution because it has many dissolved particles in it

Suspension – blood is a suspension because it has many particles suspended in it such as cells

Acids and Bases

Acid – substances that release Hydrogen ions (H+) when dissolved in water

Base – substances that release hydroxide ions (OH-) when dissolved in water

pH

The measure of concentration of H+ in a solution

pH of pure water is 7 (neutral) pH of lower than 7 are acidic

– have more H+ pH of higher than 7 are basic

– -have more OH-

pH Scale

Buffers

Mixtures that can react with acids or bases to keep the pH within a particular range

In cells, buffers keep the range between 6.5 and 7.5

In blood, buffers keep the range at about 7.4

End of 6.3

6.4 The Building Blocks of Life

p. 166 - 171

How does Chemistry relate to

Biology?

Main Idea

Organisms are made of carbon-based molecules

Organic Chemistry

Carbon can form covalent bonds with 4 other atoms, including other carbons

Can form straight chains, branched chains, and rings

Macromolecules

large molecules that are formed by joining smaller organic molecules together

Polymers

Molecules made from repeating unit of identical or nearly identical compounds linked together by a series of covalent bonds

Poly means many

P. 167

Use table 6.1 and list examples and functions of the 4 biological macromolecues

Carbohydrates

Compounds composed of carbon, hydrogen, and oxygen in a ratio of 1O, 2H, 1C

(CH2O)n – n is the number of units in the chain

Carbohydrate functions

Energy source – monosaccharide, disaccharide, sucrose (table sugar), lactose (in milk)

Structural support – in plants, cellulose provides support in cell walls– In animals Chitin is a polysaccharide that is the

main component in the hard outer shell of shrimp, lobsters, and some insects and fungi

Lipids

Molecules made mostly of carbon and hydrogen that make up fats, oils, and waxes

Primary function is to store energy– In animals, stored in fat cells– In plants, used as waxy coating on some

leaves

p. 169

Use your textbook to describe the following:– Saturated fats

– Unsaturated fats

– Polyunsaturated fats

Types of fats

– Saturated fats - Lipids that have tail chains with only single bonds between the carbon atoms

– Unsaturated fats - Lipids that have at least one double bond between carbon atoms

– Polyunsaturated fats - Fats with more than one double bond in the tail

Other Lipids

Phospholipid - Responsible for the structure and function of the cell membrane, serves as a barier in biological membranes

Steroid – examples: cholesterol and hormones such as estrogen and testosterone

Proteins

A compound made of small carbon compounds called amino acids

Amino acids

Small compounds that are made of carbon, nitrogen, oxygen, hydrogen, and sometimes sulfer

Amino Acid Structure

Have a central carbon atom An amino group (H2N)

A H atom A variable group – this makes each one

different (20 different groups)

3-D structure

Proteins have up to 4 levels of structure:– Primary structure - # of amino acids in a

chain and the order they are in– Secondary structure – folds into a uinque

3-d shape (helix and pleat)– Tertiary structure – globular or long fibers– 4th level – combining with other proteins

Nucleic Acid

Complex macromolecules that store and transmit genetic information

Made of smaller nucleotides

Nucleotides

Composed of carbon, nitrogen, oxygen, phosphorus, and hydrogen atoms

6 major nucleotides

DNA and RNA

Nucleic acids found in living organisms

ATP

The storehouse of chemical energy that can be used by the cells

End of 6.4

End of Ch. 6