Unit 1: Chemistry of Life

AP Biology | 2024-2025

What are elements?

substances that cannot be broken down into simpler substances

What are the 4 most common elements?

carbon (C), hydrogen (H), oxygen (O), and nitrogen (N)

What are the CHON elements used for?

building biological molecules and forming storage compounds and cells in all organisms

What are trace elements?

elements required by an organism only in very small quantities

What are examples of trace elements?

iron (Fe), iodine (I), and copper (Cu)

What are atoms?

the units of life and the building blocks of the physical world

What are protons?

positively charged (+) particles

What are neutrons?

uncharged particles

What are electrons?

negatively charged (-) particles

What are isotopes?

atoms that have the same number of protons but differ in the number of neutrons in the nucleus

What are compounds?

2 or more elements held together by chemical bonds

What are the different types of chemical bonds?

ionic, covalent, and hydrogen

What is an ionic bond?

a bond formed between 2 atoms when one or more electrons are transferred from atom to another

What are ions?

the charged forms of the atoms in ionic bonds

What are covalent bonds?

bonds between atoms that share electrons

What are nonpolar covalent bonds?

covalent bonds that share electrons equally

What are polar covalent bonds?

covalent bonds that share electrons unequally

What are hydrogen bonds?

weak chemical bonds that form when a hydrogen is covalently bonded to an oxygen atom

What special properties does hydrogen bonding give water?

• cohesion

• adhesion

• surface tension

• high specific heat

• unique characteristics as ice

What is cohesion?

the linking together of like molecules

How does cohesion help water transport in plants?

by helping hold together the column of water within the cells

What is adhesion?

the clinging of one substance to another

How does adhesion help water transport in plants?

by helping resist the downward pull of gravity

What is surface tension?

a measure of how difficult it is to stretch or break the surface of a liquid

How is the surface tension of water significant?

water has unusually high surface tension, making it behave as though it were coated with an invisible film

What is specific heat?

the amount of heat that must be absorbed or lost for 1g of a substance to change its temperature by 1^°C

How is water’s high specific heat significant in nature?

• a large body of water can absorb and store a huge amount of heat from the sun in the daytime and during the summer while warming up only a few degrees, and at night and during the winter, the gradually cooling water can warm the air

• ocean temperatures are stabilized, creating a favorable environment for marine life

• since organisms are made primarily of water, they are better able to resist changes in their own temperature

What are the properties of ice?

• it is less dense than liquid water and thus can float

• water expands when it solidifies, forming a lattice structure

How are the properties of ice significant in nature?

• if ice sank, all bodies of water would freeze, making life as we know it impossible on Earth

• when a deep body of water cools, the floating ice insulates the liquid water below, preventing it from freezing and allowing life to exist under the frozen surface

When is a solution acidic?

if it contains a lot of hydrogen ions (H+)

What happens if you dissolve an acid in water?

it will release a lot of hydrogen ions

When is a solution basic?

if it contains a lot of hydroxide ions (OH-)

What happens if you dissolve a base in water?

it will release a lot of hydroxide ions

What are organic molecules?

molecules that contain carbon

What are inorganic molecules?

molecules that do not contain carbon

Why is carbon important for life?

it is a versatile atom, meaning that it has the ability to bind not only with other carbons but also with a number of other elements, including nitrogen, oxygen and hydrogen

What are monomers?

the individual building blocks of a polymer

What are polymers?

chains of building blocks in macromolecules

What is dehydration synthesis?

the formation of polymers by removing water to form a bond

What is hydrolysis?

the breaking apart of polymers by adding water to break a bond

What are macromolecules?

the 4 classes of organic compounds to life on earth

What are the 4 macromolecules?

carbohydrates, proteins, lipids and nucleic acids

What are elements make up carbohydrates?

carbon, hydrogen and oxygen in a 1:2:1 ratio

What are the most common monosaccharides?

glucose and fructose

What are monosaccharides the energy source for?

cells

How are glucose and fructose depicted?

as either “straight” or “rings” with Hs and OHs attached to them

What are disaccharides formed by?

glycosidic linkage

What is maltose formed from?

2 glucose molecules

What are polysaccharides?

many repeated units of monosaccharides in branched or unbranched chains

What are examples of polysaccharides?

starch, cellulose, glycogen, chitin

What is the function of starch?

to store sugar in plants

What is the function of glycogen?

to store sugar in animals

What is the function of chitin and cellulose?

to provide structural support

What are proteins important for?

structure, function, and regulation of tissues and organs

What is the structure of proteins?

an amino group (-NH₂), a carboxyl group (-COOH), a hydrogen, and an R-group surrounding a central carbon

What are the monomers of proteins?

amino acids

What elements are in proteins?

carbon, hydrogen, oxygen and nitrogen

How many different amino acids are there?

20

How do we distinguish between amino acids?

based on their R-group

How do you spot amino acids?

by looking for the amino group (NH₂), then looking for the carboxyl molecule

What does side chain polarity affect?

whether an amino acid is more hydrophobic or more hydrophilic

What are the polymers of proteins?

polypeptides

What is a dipeptide?

2 amino acids joined together when the carboxyl group of one combines with the amino group of another

What is a peptide bond?

the bond between 2 amino acids

What is the primary structure of a protein?

the linear sequence of the amino acids

What are the secondary structures of a protein?

the coils (alpha helix) and zigzags (beta-pleated sheets) that form when a polypeptide begins twisting

What is the tertiary structure of a protein?

the interaction of amino acids that were far apart from each other prior to polypeptide reshaping

What is the quaternary structure?

the interaction of different polypeptide chains

What elements do lipids consist of?

carbon, hydrogen and oxygen

What are examples of lipids?

triglycerides, phospholipids, steroids

Why are lipids important?

due to their nonpolar structures

What are the functions of lipids?

• to provide structure for cell membranes

• to provide insulation

• to signal molecules

• to store energy

What are triglycerides?

a glycerol molecule with 3 fatty acid chains attached to it

What are saturated fatty acids?

fatty acids saturated with hydrogen along its long carbon chain

What are unsaturated fatty acids?

fatty acids that have a double bond in their chain

What is lipid saturation?

the extent that saturation in a lipid can affect its structure and function; the more double bonds that exist within a lipid, the more unsaturated it is

What is the structure of phospholipids?

2 fatty acid tails and 1 negatively charged phosphate head

Why are the phospholipid heads hydrophobic?

because their lack of polarity prevents them from mixing well with water

Why are the phospholipid tails hydrophilic?

because their polarity allows them to mix well with water

What is cholesterol?

a four-ringed molecule that is found in membranes

What is cholesterol important for?

making certain types of hormones and vitamin D

What elements are in nucleic acids?

carbon, hydrogen, oxygen, nitrogen, and phosphorus

What are the monomers of nucleic acids?

nucleotides

What does DNA contain?

the hereditary “blueprints” of life

What is RNA essential for?

protein synthesis