Biochemistry

Macromolecules

• To discuss macromolecules, we will have to explore some chemistry

• Everything you’ll need to know about chemistry will fit on these few slides– I promise!

The Basics

• All matter is made of atoms• Every atom has a nucleus with at least one proton and usually some neutrons– Protons exert a + charge around them– Neutrons have no charge

• These + charges attract electrons which each have a – charge– Electrons are way smaller so they zoom around

really fast and can’t hold still

Chemistry is Electron Behavior

• The number of protons determines what element it is– Where it goes on the periodic table of the elements

• The reason this matters is because there are fixed slots the electrons fit into, and electrons “want” to fill the slots if possible

• Atoms will sometimes donate or receive electrons– Ionic bonds

• Other atoms will share electrons to fill the slots– Covalent bonds

Ionic Bonds

• An ionic bond is weak; it dissolves in an environment with many charges– Salt dissolves in water

• Sodium, potassium and calcium are three common metals that form ionic bonds– They donate their electrons to halogens like

chlorine and become cations (positive charges)– They are required in our bodies in specific

amounts, dissolved in our blood and cells

Covalent Bonds

• Covalent bonds are formed as a sharing of electrons between nonmetals– Metals do NOT typically form covalent bonds

• The goal is to have four pairs of electrons for most nonmetals– Carbon has four unpaired electrons so it can make

four covalent bonds– Oxygen has six electrons so only makes two bonds

Covalent Bond Behavior• Sometimes covalent bonds are uneven– Electron spends more time on one end than the

other– Anyone who’s shared custody of children knows

sharing is often uneven!• This means the atom with more than 50%

time is slightly negative and the atom with less than 50% is slightly positive– This is a polar bond and may make the molecule a

polar molecule

Example of Polar Molecule:

• Water!• Water dissolves salt (ionic

bonds) because the positive and negative atoms mix with the positive and negative charges in the water

• This means water (and other polar chemicals) are slightly “sticky”

Three questions:

• Why is water “sticky” when you can slip on it?

• What is a very sticky liquid?

• What is a very not-sticky liquid?

Best Answers:

1) All liquids are slippery to some degree– Also note: ice is only slippery if it has a layer of

water on the outside

2) Honey, syrup, molasses: all have sugar in them!

3) Oil, grease: all have lipids which are nonpolar!

Sugar (Carbohydrates)

• Sugars are carbon molecules with lots of oxygen and hydrogen, so they are also polar molecules

• They mix well with water and form many more + - attachments– This is why honey is so sticky!

Starch• Starches are made of many individual sugar rings

bonded together• Some starches (white bread, white rice, etc) can be

digested quickly• Others (brown rice, whole wheat bread etc) are

digested more slowly– This is why brown carbs are better for you!

Lipids (Fats & Oils)

• Lipids are made with carbon and hydrogen– Carbon and hydrogen form

a nonpolar bond• Since electron sharing is

even, no + and – charges form

• This means they do not mix with water– Hydrophobic

Consider the Following:• Since oils are not sticky (no

polar bonds) they don’t stick to glass like water does

• Since oil and water don’t mix, how do you get oil off your hands?– Soap! Soaps are chemicals with

hydrophobic and hydrophilic parts so they can make oil and water mix (detergent)

– The term for this is to emulsify

Nucleic Acids and Amino Acids

• DNA and RNA• Stores/handles

information• Usually made of a

nitrogenous base attached to a sugar with 1 or more phosphate groups– The phosphate groups

store energy

• Strung together to make proteins

• Proteins perform almost all jobs in human body– Messengers– Structural fibers– Enzymes– Transportation

• Made using information in DNA

See you next week!

• DNA and Protein structures will not be discussed until week 6– Their functions will be lightly covered next week