Biology Unit 2 The Chemistry of Life

Matter Something that has mass and takes up space

Mass The amount of matter something contains. This differs greatly from weight!

Elements Substances that can not be broken down into simpler forms of matter Examples include gold, oxygen, iron, calcium and lead

Elements Important for Life The most important elements for life are carbon (C), hydrogen (H), oxygen (O), nitrogen (N), and phosphorus (P) Calcium (Ca), Magnesium (Mg), potassium (K), sodium (Na), chlorine (Cl) and iron (Fe) are all needed in lesser amounts

Atoms The simplest particle of an element that still retains the properties of that element

Parts of an Atom The nucleus makes up most of the mass of an atom; it is made of two parts Protons – the part of a nucleus that has a positive charge Neutrons – the part of a nucleus that has no charge

Parts of an Atom Cont'd Electrons – negatively charged parts of an atom that orbit at high speeds around the nucleus Overall, the charge on a normal atom is zero (neutral).

Model of an Atom

Molecule Two or more atoms chemically bonded together. Which of the examples to the left is a molecule?

Compound Made of atoms of two or more elements. Which of the examples to the left is a compound?

Water Water is one of the most important compounds to most forms of life, due to its unique chemical properties.

Adhesion Water's ability to stick to other things

Cohesion Water's ability to stick to itself

Hydrogen Bonding The oxygen in water is larger and attracts that electrons shared by the hydrogen unequally. This causes the oxygen portion to take on a slight negative charge and the hydrogen portion a slight positive one + H H O _

Other Properties of Water Water has a low freezing point Water has a high heat capacity (it changes temperature slowly) Help us remain warm blooded

Organic Compounds Usually contain carbon Usually associated with living creatures Most are polymers (large molecules made of repeating units) These polymers are made of small molecules called monomers

Dehydration Synthesis Monomers bond together with the removal of water.

Hydrolysis Monomers are removed with the addition of water.

Carbohydrates Made of C, H and O Monomers are called monosaccharides Examples are sugars, starch and glycogen Disaccharide – two monosaccharides bonded together Polysaccharide – many monosaccharides bonded together

Lipids Made of C, H and O Monomers are called fatty acids Examples are fats, oils, waxes, cholesterol, steroids and some hormones

Nucleic Acids Made of C, H, O, N and P Monomers are called nucleotides Example are deoxyribonucleic acid and ribonucleic acid (DNA and RNA)

Proteins Made of C, H, O and N Monomers are called amino acids Enzymes are examples Polypeptide – many amino acids bonded together

Enzymes Enzymes catalyze chemical reactions This means the reactions happen faster and need less energy to take place Complex life forms could not live without them They are not consumed

Enzyme Functioning Enzymes work best at a particular pH, which varies with each enzyme When temperatures increase, the rate of enzyme activity increases, until 40 degrees C is reached, then the enzyme denatures

Enzyme Functioning Continued Rates of enzyme activity increase as the concentration of substrate increases, until all of the enzymes are active, then increased substrate can not increase reaction rates.

Solutions A mixture of substances that look like one substance and are difficult to separate.

Solvent The part of the solution that is present in the largest amount It dissolves things

Solutes Substances present in lesser amounts Can be more than one. The substances that get dissolved

Mixtures Two or more substances together that do not look like one substance and can usually be easily separated.

Suspension A mixture in which one or more substances settle over time. Ex: Italian dressing

Colloid A mixture in which one substance is found in another, but it doesn’t settle. Ex: a Jell-o fruit cup

Importance of Carbon The number of outer level or valence electrons determines how an element will react with other elements. Most elements need to have eight valence electrons in their valence shell to be stable.

Importance of Carbon Cont’d In order to fill its outer electron shell, carbon forms four bonds with other elements The ability to form four bonds is what allows carbon to make polymers That’s why earth’s life forms are based upon carbon (organic)