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 1 st energy level – 2 electrons 2 nd energy level – 8 electrons 3 rd 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 S O 2  8 SO 2

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”

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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