Date: Name:

SBI4U ~ 1 of 3 ~ e-Summer School 2014

SBI4U Chemistry for Biology Biochemistry Review of the basics of chemistry • You should be able to…

o Define the three main sub-atomic particles – protons, neutrons, and electrons

o Calculate the number of protons, neutrons, and electrons in a given element

o Draw simple Lewis dot diagrams of elements, and Lewis structural diagrams of molecules

o Differentiate between (a) ionic bonds, (b) polar covalent bonds, and (c) non-polar covalent bonds

§ Ionic bond: results from attraction between two oppositely charged atoms or molecules (Na and Cl)

§ Polar covalent bond: bond between two atoms, made up of unequally shared electrons (H and O)

§ Non-polar covalent bond: bond between two atoms, made up of equally shared electrons (C and C)

Applications of chemistry in biology • A molecule can have different types of interactions with

other molecules depending on: o Types of bonds between atoms within a molecule o 3D orientation of the molecule

• If a molecule is polar, it can have: o Hydrogen bonding – generally occurs between

OH-OH, OH-NH, NH-OH, or NH-NH o Dipole-dipole interactions (depicted in Lewis

diagrams by δ+ and δ–) o Ion-dipole interactions

• If a molecule is non-polar, it can have: o van der Waals forces – relatively weaker than interactions than hydrogen bonding

and dipole interactions • An important pneumonic to remember is like

dissolves like o Ionic and polar compounds will dissolve and/or

interact with other ionic and polar compounds o Non-polar compounds will dissolve and/or

interact with other non-polar compounds Water and its properties • Water is especially important to biology • Polar molecule that exhibits hydrogen bonding • Naturally exists in its liquid state all over the planet • Acts as a “universal solvent” and supports life through

a number of its properties (see table)

Date: Name:

SBI4U ~ 2 of 3 ~ e-Summer School 2014

• In aqueous solutions (solutions where water is the solvent), solutes are generally divided

into two categories: o Hydrophilic molecules: polar/charged molecules that are strongly attracted to

water o Hydrophobic molecules: non-polar molecules that are not strongly attracted to

water • The cohesion and adhesion of water is very important to the

survival of plants o Cohesion: hydrogen bonding between water molecules o Adhesion: hydrogen bonding between water molecules and

other polar molecules • Another property of water is the role it plays in acidic and basic

solutions o Acids and bases can be classified as strong or weak based on

their percent ionization • When an acid and a base are mixed, a neutralization reaction

occurs resulting in a salt and water • The use of buffers in biological systems is paramount to living

organisms being able to adapt and survive environmental stress o Buffer: solution that can resist change in pH when an acid

or base is added to it

Date: Name:

SBI4U ~ 3 of 3 ~ e-Summer School 2014

Carbon • Has four valance electrons • Can form four single bonds, creating a

tetrahedral shape • Can also form double and triple bonds • Crucial to the formation of multiple bonds to

create long chains, complex ring structures, or both

Functional groups • There are a number of functional groups that

are found in organic chemistry (see chart) o There are a few functional groups that

play a larger role in biology than other functional groups

• Most functional groups are either ionic or polar

o Attracted to other ionic or polar molecules, including water

Chemical reactions in biology • There are four types of chemical reactions

important to biology: o Neutralization reactions – involves the

reaction of an acid and a base to produce salt and water

o Redox (reduction-oxidation) reactions – involves the loss/gain of electrons; more common to biology, reduction involves the addition of an H or removal of an O, and oxidation involves the removal of an H or addition of an O

o Condensation reactions (dehydration synthesis) – involves an H from the functional group on one molecule combining with an OH from the functional group of another molecule producing a larger molecule and water

o Hydrolysis reactions – involves the addition of a water molecule to a large molecule, splitting the large molecule in two

All images taken from: Raven, P., Johnson, G., Mason, K., Losos, J., & Singer, S. (2014). Biology. Canada: McGraw-Hill Ryerson

Limited.