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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