Biochemistry. Key Concept: Polarity If a molecule is created (covalent bonds), the electrons may or may not be evenly distributed – Evenly distributed:

Biochemistry

Key Concept: Polarity

• If a molecule is created (covalent bonds), the electrons may or may not be evenly distributed– Evenly distributed: nonpolar molecule– Unevenly distributed: polar molecule

• Brain check: what about ionic bonds?

Keyword: Macromolecule• A macromolecule is a very large molecule

(hundreds or thousands of atoms)– Molecule = held together with covalent bonds

• There are four groups of macromolecules– Carbohydrates– Lipids– Amino acids– Nucleic acids

• Vitamins and minerals are NOT macromolecules, they are small (but still important!)

Keyword: Intermolecular Forces

• Break down the language!– Inter=between two different things– Molecular=molecule– Force=a push or pull (in this case pull)

• The more intermolecular forces between molecules, the more the molecules stick together– Do polar or nonpolar molecules have more

intermolecular forces?

Polar Molecules• Polar molecules often

form hydrogen bonds, a type of intermolecular force

• Water is the king of hydrogen bonds, since it has two hydrogens and one oxygen– Makes it have a lot of

attractive forces

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– Known as hydrophilic– This is why honey is so sticky!

Starch• Starches are made of many individual sugar rings

bonded together– Some starches (white bread, white rice, human glycogen,

etc) are designed to break apart very quickly– Others (brown rice, whole wheat bread etc) are designed to

break apart more slowly• This is why brown carbs are better for you!

Carb Complexity

• Carbohydrates may be attached in simpler or more complex styles of arrangements– Still the same covalent bonds,

but different arrangements of the sugar rings

• Cellulose is plant fiber that is made of sugar molecules arranged into an indigestible lattice– This is why cows need 4

stomachs to eat grass

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

Common Lipids• Triglycerides are how many

living things (including humans) store energy– Contains saturated fats

and/or unsaturated fats• Cholesterol is an animal

lipid that is used for many chemical processes but not for energy– Can build up and clog

arteries in excess• Phospholipids are

triglycerides modified to have a phosphate on one end

Phospholipid Bilayer

• Phospholipids are special because they are mostly hydrophobic but the phosphate head is hydrophilic

• This causes the molecules to naturally line up and form a thin layer of oil

• This forms the basis of the cell membrane

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

Amino Acids

• Amino acids fit together like beads on a chain– Human bodies use 20

different kinds (there are many more) and each kind has a different molecule on its side chain

• The order of the amino acids cause the chain to coil up and form a protein

Some Protein Structures

Nucleic Acids

• How do our cells know what order to put the amino acids into?– Our DNA of course!

• DNA (Deoxyribose nucleic acid) is a macromolecule that stores information– The order of base pairs (A, T, G, C) codes for

amino acids in a sequence!– This process will be covered in chapter 3

Nucleic Acids

Structure of a DNA Nucleotide

• A nucleotide is a single “letter” of a DNA chain– Contains a base (the “letter), a

sugar molecule, and one or more phosphate molecules

– The energy is stored in the phosphate molecules

• The cell often uses an adenosine molecule with three phosphates to provide energy for chemical reactions– The famous ATP

See you Friday!

• Also don’t forget the review quiz is online!