The Chemistry of Life Chapter 2

Why should we study chemistry in Biology? Life depends on chemistry!

Life depends on chemistry! When you eat food or inhale oxygen, your body uses these materials in chemical reactions that keep you alive. Just as buildings are made from bricks, steel, glass, and wood, living things are made from chemical compounds. Wouldn’t you want an architect to understand building materials? Same idea applies to geneticists, ecologists, zoologists, botanists, biologists, and etc.

Atoms The study of chemistry begins with the basic unit of matter…the History Greeks were first to try to explain chemical reactions 400 BC: thought all matter composed of: ________ _________ first used word “________”, meaning indivisible Atom

Atoms Atoms are composed of 3 main particles: (subatomic particles) Protons (+) Neutrons Electrons (-)

Protons and Neutrons Strong forces bind protons and neutrons together to form the ________, which is at the center of the atom. Both particles have about the same _______.

Electrons Electrons are negatively charged with about 1/1840 the mass of a _________. They are in constant________ in the space surrounding the nucleus.

Atoms Atoms have _______ numbers of electrons and protons. Because these subatomic particles have equal but _________ charges, atoms are _________.

Elements Elements are the building blocks of all matter. Elements cannot be __________ into simpler matter. Group Number: 1 2 3 4 5 6 7 8

The Elements ____ known elements ____ occur naturally The ____ elements form a plethora of compounds, just as 26 letters of the alphabet make a seemingly endless number of words.

Atomic Number Counts the number of _________ in an atom

Atomic Number on the Periodic Table 11 Na

All atoms of an element have the same number of protons 11 Na 11 protons Sodium

Atomic Mass Mass of an atom. Approximately equal to the number of ___________ and ___________ Find number of neutrons by subtracting the number of protons from the mass.

The Periodic Table

Isotopes Isotopes are atoms that have the same atomic number but different ______________. Most elements have two or more isotopes. Same ________ properties because the electron number does not change.

Isotope symbols X A Z Mass number Atomic number

B Example How many protons does this have? 11 5 How many protons does this have? How many neutrons does this have? Is the “5” necessary ?

More about isotopes: Some isotopes have ________ nuclei which break down over time. They are called _________ isotopes Some radiation is harmful.

Radiation can also be useful Radioactive Dating Tracers with X-rays Cancer Treatment Kill bacteria

More About Atomic Structure The center of the atom is called the ___________. Electrons live in something called ________. Shells are areas that surround the center of an atom. A shell is sometimes called an _________ or ____________________.

More About Electrons Every shell can hold only so many electrons The _________ from the nucleus, the more electrons a shell can hold

Valence Electrons The electrons on the ________ edge of the atom This is where the action is- where _________ takes place Atoms have no more than __ valence electrons

The Octet Rule: Atoms will combine to form ___________ in order to reach eight electrons in their outer energy level. This is very stable! Atoms with _________________ tend to lose electrons. Atoms with ______________ tend to gain electrons.

Compound ______ or ______ elements chemically combined in specific proportions Examples: Water H2O _____ NaCl Sugar C6H12O6 Chemical Formulas are used to represent compounds Two types of compounds: ______________

Ionic Compounds Form when electrons are _________ from one atom to another. ______ - Atoms with a net charge due to gaining or losing electrons Gaining electrons gives an ion a _______ charge Losing electrons gives an ion a _________ charge **If they have to choose, atoms would rather be stable (with a full “octet”) than neutral.

How Does This Happen? Some atoms have a few too many electrons Some atoms only need a few electrons

What do you do if you are a sodium (Na) atom with one extra electron? Go look for an atom that wants it!

Ionic Bonding Negative ions and positive ions are held together by ionic bond.

Ionic compounds form between ______ and ________

What If No One Will Give Up An Electron? Atoms with less than __valence electrons can move close to each other and _______ their electrons The electrons spend their time around both atoms. And they lived happily ever after!

Covalent Bonds Formed when a pair of electrons is _______ between two atoms. Sometimes the atoms share two pairs of electrons and form a ___________, or three pairs of electrons to form a __________. Structures formed by covalent bonds are ___________.

Covalent compounds form between 2 ________

Van der Waals Forces There are small _________ forces between all atoms Help to hold molecules to each other Ex: Gecko

2-2 Water is a Polar Molecule Polar: Molecule in which electrons are shared _________ between atoms, causing each end of the molecule to have a slight ________ Negative end Positive end

This causes water to be attracted to other polar or charged particles Water is attracted to _______ Water is attracted to itself, forming hydrogen bonds

Hydrogen Bonds In Water Are Responsible For: __________ Attraction between molecules of different substances Graduated cylinder Attraction between molecules of the same substance Drops of water on a penny Ex: Surface Tension Jesus Lizard

Types of Chemical Substances Compounds and Elements are called _____________. Most matter is neither of these.

Mixtures Mixtures are combinations of substances held together by __________________, not chemical bonds. Each substance keeps its own properties

Mixtures may be either: ____________ ________ ____________

Solutions Have small particles Are ___________ (not the same as colorless) Do not separate Water solutions are very common in biological systems Examples: salt water, kool-aid, air, brass, vinegar

Suspensions Have very________ particles Settle out (separates into layers) Examples: blood platelets, muddy water, calamine lotion, oil & water, Italian salad dressing

pH Scale Measures concentration of __________ ions in a solution Ranges from 0 to 14 7 is _______ 0-7 have more hydrogen ions (H+) and are _______ 7-14 have more hydroxide ions (OH-) and are _______

Acids, Bases, and pH Water molecules form ions H2O H+ + OH- Water hydrogen ion + hydroxide ion Very few ions are formed in pure water, but there are equal numbers of hydrogen and hydroxide ions Water is neutral!

pH of common substances

pH and Homeostasis Maintaining a pH between 6.5 and 7.5 is important in cells Dissolved compounds called _______ control pH ________

Organic Compounds

Organic Compounds Make up most of living organisms Contain bonds between two or more _______ atoms Carbon can easily bond with up to __ other elements 4 valence electrons = 4 covalent bonds

Organic Compounds Carbon atom is versatile, can be “__________” of long chains or rings Organic molecules can be extremely large and complex; these are called ________________

Macromolecule “______ molecules” Formed by a process called _________________ Large compounds (________) are built by joining smaller ones (__________) together

Organic Compounds Four main types of organic macromolecules: ______________ _______ __________

Carbohydrates Made of Carbon, Hydrogen, & Oxygen Main energy source for living things Breakdown of sugars supplies immediate _______ for cell activities Extra sugar is stored as complex carbs called __________

Carbohydrates Single sugar molecules are called _________________ Examples: _________ – in many plant and animal tissues, most common monosaccharide ________ – in many fruits galactose – component of milk

Carbohydrates Large molecules of many monosaccharide are _______________ Examples: __________ – animals use to store excess sugar plant starch – plants use to store excess sugar __________ – fibers that give plants their rigidity & strength

Lipids Store more energy than carbohydrates because the chains are longer Ex: Fats, oils, waxes Won’t dissolve in water

Lipids Important parts of biological membranes and __________ coverings __________ are lipids that act as chemical messengers

Lipids Many lipids are made from a glycerol combined with ____________ If all carbons have single bonds, lipid is ___________ Ex: butter, lard, animal fat (usually solid at room temperature) If any carbons have double or triple bonds, lipid is ________________ Ex: vegetable oil, fish oil, peanut oil (usually liquid at room temperature)

Proteins Contain C, H, O, plus ________ Formed from _______________ joined together More than ___ amino acids can be joined in any order or number to make countless proteins (think of how many words can be made from 26 letters!)

Proteins Chains are folded and twisted giving each protein a ______________ ______________ forces and __________ bonds help maintain protein’s shape _________ of protein is important to its function!

Proteins Provide structure Aid chemical activities in your body Ex: _______- makes up your skin, muscles & bones Aid chemical activities in your body Ex: ________- work to speed up rxns in your body Transport substances into or out of cells Help fight diseases

Nucleic Acids Contain C, H, O, N plus ____________ Formed by bonding of individual units called __________ Nucleic Acid nucleotide

Nucleic Acids Store and transmit hereditary information Ex: (deoxyribonucleic acid) _____(ribonucleic acid)

Chemical Reactions When one set of chemicals changes into another set of chemicals, a ________________ occurs Bonds are either ________ or _________ (or both!)

Chemical Equations 2H2O Represent a reaction Give the types and amounts of substances that react and form _________ _________ 2H2 + O2 “yields” “yields” 2H2O

Evidence of a Chemical Reaction Formation of a _________ (a solid substance separated from a liquid) _____ is evolved (seen by bubbles forming in a liquid) Change in ______ or light energy

Energy Transfer Much of the energy organisms need is provided by _____ (food) Undergoes a series of chemical reactions in which energy is released (___________________) The net release of free energy is called an __________ (exothermic) reaction

Reactions that involve a net absorption of free energy are called ______________ (endothermic) reactions _____________ is an example Most reactions in living organisms are endergonic; therefore living organisms require a __________ source of energy

Most chemical reactions require ________ to begin The amount of energy needed to start the reaction is called ______________________

Enzymes Some chemical reactions are slow or have activation energies that are too high to make them practical for living tissue These chemical reactions are made possible by ____________

Catalyst Substance that speeds up the rate of chemical reactions Work by lowering a reaction’s __________________

Enzymes Mostly _________. Biological catalysts _______ up reactions in cells Very specific Named for the reaction is catalyzes Names always end in ________

Substrates The __________ of enzyme catalyzed reactions The _________ of the enzyme and the substrate have complementary shapes Fit like a lock and key.

Regulation of enzyme activity Enzymes are affected by any variable that affects chemical reactions ____ ____________ _______________