The Chemistry of Life

Chapter 3

3-1: Matter and Substances

Atoms

Atom – the smallest unit of matter that can’t be broken down by chemical means

Atoms are made up of three types of particles: Proton: (+) charged Neutron: no charge Electron: (-) charged

Nucleus – consists of protons and neutrons

Atoms

A proton is about 1000 times larger than an electron

Electron cloud – the region where electrons orbit the nucleus

Atoms

Atomic mass = protons + neutrons

Atomic number - The number of protons in the nucleus of an atom, which determines its place in the periodic table

Atoms

Atomic Facts Atomic number = protons = electrons

Atomic mass

- Atomic number # of neutrons

Maximum number of electrons 1st energy level – 2 electrons 2nd energy level – 8 electrons 3rd energy level – 18 electrons

Atoms

Element – A substance made up a group of similar atoms that have the same number of protons

Atoms

Isotopes – Atoms of an element that have different numbers of neutrons

Chemical Bonds

Valence electron – An electron that is found in the outermost shell of an atom Lewis dot diagrams can be used to show the

transfer of valence electrons

Chemical Bonds

Chemical bonds form between groups of atoms because most atoms become stable when they have eight electrons in the valence shell (Octet rule)

Chemical Bonds

Compound – A substance made of the bonded atoms of two or more different elements

Chemical Bonds

Ion – an atom or group of atoms that has an electric charge because it has gained or lost electrons Ionic bond – the attractive force between

oppositely charged ions

Chemical Bonds

Covalent bond – chemical bond that shares electrons

Molecule – A group of atoms held together by covalent bonds

Chemical Bonds

Hydrogen bond - A chemical bond in which a hydrogen atom of one molecule is attracted to an electronegative atom

Chemical Bonds

Polarity

Polar – molecules with partial charges on opposite ends

Water is the most abundant compound in organisms

3-3: Carbon Compounds

Building Blocks of Cells

The basic units of most biomolecules contain atoms of carbon

Carbon atoms have the ability to form four covalent bonds

Carbohydrates

Carbohydrates – molecules made of sugars Sugar – contains carbon, hydrogen, and oxygen

in a ratio of 1:2:1 Monosaccharide – a simple sugar

Simple carbohydrates Ex. - glucose

Carbohydrates

Disaccharide – two sugars linked together Oligosaccharide – few sugars linked together

Ex. – Sucrose (table sugar) Ex. – Lactose (found in milk)

Carbohydrates

Polysaccharide – Many sugars linked together Complex carbohydrates Starch – Consisted of hundreds of glucose units

bonded together

Carbohydrates

Unused glucose in animals is stored as glycogen

Unused glucose in plants is stored as starch

Carbohydrates

Chitin and cellulose are used to provide support Chitin is found in shells of crabs, lobsters, and

insects Cellulose is found in cell walls of plants

Lipids

Lipids – An organic molecule made up of carbon, hydrogen, and oxygen and will not dissolve in water Ex. – Fats, phospholipids, steroids, and waxes

Lipids

Some steroid molecules include cholesterol and sex hormones (testosterone and estrogen)

Lipid Functions

The main purpose of fats is to convert excess food into long-term energy storage units

Phospholipids border cell membranes Wax covers parts of plants and aquatic birds

to repel water

Proteins

Protein – composed of chains of amino acids made of carbon, hydrogen, oxygen, and nitrogen Amino acids – building blocks of proteins

Peptide bond – covalent bond between two amino acids

Nucleic Acids

Nucleic acid – a long chain of nucleotide units Nucleotide – a molecule made up of a sugar,

phosphate group, and a base DNA stores genetic information RNA produces proteins

Nucleic Acids

ATP (adenosine triphosphate) – an organic molecule that acts as the main energy source for cell processes

3-4: Energy and Metabolism

Chemical Reactions

Reactant – a substance that participates in a chemical reaction

Product – a new substance that is formed in a chemical reaction

S8 + 8 O2 8 SO2

Chemical Reactions

Activation energy – the minimum amount of energy required to start a chemical reaction

Biological Reactions

Enzyme – a molecule that acts as a catalyst in biochemical reactions

Catalyst – used to speed up a chemical reaction

Biological Reactions

Substrate – the substance acted upon by an enzyme

Active site – the site that attaches to a substrate on an enzyme Active sites work like a

“lock and key”

http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_enzymes_work.html

Biological Reactions

Many enzymes are proteins Denature – Changes in temperature and pH

can change a protein’s shape If an enzyme changes shape, it won’t work well