AP Biology: Chemistry of Life - Water, Macromolecules, and Cell Structures

Water

A molecule that occurs between the attraction of hydrogen molecules and oxygen molecules.

Covalent Bonds

Bonds that occur between two non-metals where valence electrons are shared to satisfy the atoms' octet rule.

Hydrogen Bonds

Bonds that form when a hydrogen atom is attracted to a highly electronegative atom due to unequal sharing of electrons in a polar covalent bond.

Specific Heat

The amount of energy required to change one gram of water one-degree Celsius.

High Specific Heat

Water can resist changes in temperature due to hydrogen bonds requiring energy to break, which helps moderate air temperatures and stabilize large bodies of water.

Heat of Vaporization

The amount of energy required to convert one gram of a liquid into a gas at its boiling point without a change in temperature.

Evaporative Cooling

The reduction in temperature that occurs when a liquid evaporates, allowing body temperatures in living organisms to be maintained.

Cohesion

The attraction between molecules of the same substance.

Adhesion

The attraction between molecules of different substances.

Surface Tension

The property of the surface of a liquid that allows it to resist an external force due to cohesive forces between liquid molecules.

Polarity

A property of molecules where there is an uneven distribution of electron density, leading to a molecule having a positive and negative end.

Octet Rule

The principle that atoms tend to bond in such a way that they have eight electrons in their valence shell, achieving a stable electron configuration.

Biological Function of Water

The properties of water that result from its polarity and hydrogen bonding, affecting its role in biological systems.

Hydrogen Atom

An atom that can form hydrogen bonds due to its slight positive charge when bonded with electronegative atoms.

Electronegativity

The tendency of an atom to attract electrons towards itself when it is chemically bonded with another atom.

Complex Properties

Properties that emerge from the interactions of biological systems.

Khan Academy Video

A resource for additional information about the structure of water and hydrogen bonding.

Biological Systems

Systems that interact and exhibit complex properties due to their components and their interactions.

Hydrogen Molecules

Molecules that are part of water, contributing to its unique properties through bonding.

Oxygen Molecules

Molecules that are part of water, playing a crucial role in its structure and properties.

Energy Release

The energy that is released when hydrogen bonds are broken, contributing to the stability of water temperature.

Homeostasis

The ability of an organism to maintain stable internal conditions despite external changes.

Capillary Action

The ability of water to move upward through narrow spaces against gravity, due to the combined forces of cohesion and adhesion.

Macromolecules

Large molecules required by living organisms, composed of smaller units called monomers.

Dehydration Synthesis

Occurs when two smaller molecules come together to make a larger molecule, involving the removal of a hydrogen ion (H+) and a hydroxyl group (OH-) to form a bond and create a polymer.

Monomer

The building block of a larger molecule.

Polymer

A larger molecule that occurs when monomers are bonded together.

Hydrolysis

Occurs when a larger molecule (polymer) is broken into smaller molecules (monomers) by adding a water molecule to break the covalent bond.

Hydrogen

An element required to make up the building blocks of life.

Carbon

An element required to make up the building blocks of life; must be present for something to be considered organic.

Nitrogen

An element required to make up the building blocks of life; found in proteins and nucleic acids.

Oxygen

An element required to make up the building blocks of life; can form two bonds.

Phosphorus

An element required to make up the building blocks of life; can form three bonds and is found in nucleic acids.

Sulfur

An element required to make up the building blocks of life; found in proteins.

Atomic Number

The number of protons in the nucleus of an atom, defining the element.

of Valence Electrons

The number of electrons in the outer shell of an atom that can participate in forming bonds.

of Bonds it can form

The maximum number of covalent bonds an atom can form based on its valence electrons.

Dynamic Homeostasis

The process by which biological systems maintain stability while adjusting to conditions that are optimal for survival.

Building Blocks of Life

The essential elements and compounds that make up living organisms.

Carbohydrates

Composed of carbon (C), hydrogen (H), and oxygen (O) in a 1:2:1 ratio (e.g., glucose is C₆H₁₂O₆).

Glycosidic bonds

Covalent bonds that connect monomers to build polymers.

Monosaccharides

Monomers of carbohydrates (e.g., glucose, fructose).

Disaccharides

Polymers of carbohydrates formed from two monosaccharides (e.g., sucrose).

Polysaccharides

Polymers of carbohydrates formed from multiple monosaccharides (e.g., starch, cellulose, glycogen).

Short-term energy source

Glucose is used for cellular respiration.

Energy storage

Starch in plants and glycogen in animals serve as energy storage.

Structural support

Cellulose in plant cell walls and chitin in fungal cell walls and arthropod exoskeletons provide structural support.

Lipids

Typically nonpolar and hydrophobic molecules.

Fatty acids

Monomers of lipids that can be saturated or unsaturated.

Saturated fatty acids

Contain only single bonds between carbon atoms and are solid at room temperature.

Unsaturated fatty acids

Contain at least one double bond between carbon atoms, causing kinks, and are liquid at room temperature.

Triglycerides

1 glycerol + 3 fatty acids (saturated or unsaturated).

Phospholipids

1 glycerol + 2 fatty acids + phosphate group.

Steroids

Composed of 4 fused carbon rings (e.g., cholesterol).

Long term energy storage

Fats provide long term energy storage and support cell function.

Steroids and hormones

Support physiological functions.

Cholesterol

Provides structure in cell membranes.

Phospholipid bilayers

Formed by phospholipids, these are the main components of cell membranes.

Nucleic acids

Polymers made of nucleotide monomers.

Nucleotide

The monomer of a nucleic acid, comprised of a nitrogenous base, sugar, and phosphate group.

3' end

The end of a nucleic acid strand with a hydroxyl group.

5' end

The end of a nucleic acid strand with a phosphate group.

Covalent bonds in nucleic acids

Formed between nucleotides when new nucleotides are added to the 3' end of the growing strand.

Antiparallel orientation

The two strands of DNA run in opposite directions (5' to 3' and 3' to 5').

Base pairing in DNA

Adenine pairs with Thymine.

Base pairing in RNA

Adenine pairs with Uracil.

Base pairing in both DNA and RNA

Guanine pairs with Cytosine.

Differences between DNA and RNA

DNA is double stranded while RNA is single stranded.

Uracil

Only found in RNA.

Thymine

Only found in DNA.

Deoxyribose

Found in DNA.

Ribose

Found in RNA.

DNA location

DNA can't leave the nucleus.

RNA location

RNA can be found throughout the cell.

Function of DNA

Stores genetic information that determines the structure and function of proteins.

Hereditary material

DNA acts as the hereditary material passed from parent to offspring.

Instructions for proteins

DNA provides the instructions for making all the proteins an organism needs.

Function of RNA

Transfers genetic information from DNA so proteins can be made.

mRNA

Messenger RNA carries the genetic code from DNA to ribosomes.

tRNA

Transfer RNA brings amino acids to the ribosome during translation.

rRNA

Ribosomal RNA is part of the ribosome and helps assemble proteins.

Amino Acids (AA)

The monomers of proteins.

Structure of Amino Acids

AAs have a central carbon bound to an amine group, carboxyl group, hydrogen atom, and R group.

R group

Different for each amino acid and helps determine the properties of the amino acid.

Categories of Amino Acids

AAs are grouped into hydrophobic/non-polar, hydrophilic/polar, or ionic.

Peptide bonds

Covalent bonds formed between the carboxyl group of one amino acid and the amine group of the next amino acid.

Primary structure of protein

Determined by the specific sequence of amino acids.

Secondary structure of protein

Made by interactions between atoms on the backbone of the protein, forming alpha-helices and beta-pleated sheets.

Tertiary structure of protein

Results from interactions between the side chains of the amino acids.

Quaternary structure of protein

Arises from interactions of multiple polypeptides coming together to form a protein.

Functions of proteins

Include enzymes, transport, defense, structure, cell signaling, and movement.