AP Biology Unit 1 Notes

Basics of Chemistry

Matter, Atoms, and Elements

Everything is made of matter, which is composed of atoms.
Atoms consist of protons and neutrons in the nucleus, with electrons orbiting around.
Different kinds of atoms make up elements, each with a unique number of protons (atomic number).
Life requires approximately 25 chemical elements, with carbon, hydrogen, oxygen, and nitrogen making up 96% of living matter.
Isotopes are atoms of the same element with different numbers of neutrons, some of which are unstable and undergo nuclear reactions.

Atomic Structure and Behavior

The number of protons in an atom determines its element and atomic number, which also equals the number of electrons.
All atoms of the same element exhibit identical chemical properties.
Elements in the same row of the periodic table have the same number of electron shells.
Moving from left to right in the periodic table, elements have a sequential addition of protons and electrons.
Atoms tend to complete or empty their outer (valence) electron shell, following the Octet rule, which drives chemical reactions.

Chemical Bonds

Ionic bonds involve the transfer of electrons, forming positive and negative ions.
Covalent bonds entail the sharing of electron pairs between atoms, forming molecules.
Double and triple covalent bonds involve sharing multiple pairs of electrons and are very strong.
Polar covalent bonds result from unequal sharing of electrons, creating a polar molecule.
Hydrogen bonds occur between a hydrogen atom and an electronegative atom like oxygen, contributing to unique properties of water.

Importance of Chemistry in Biology

Foundation of Biology

Chemistry forms the foundation of biology, as biological processes rely on chemical interactions.
Approximately 25 chemical elements are essential for life, with carbon, hydrogen, oxygen, and nitrogen being predominant.
Understanding chemistry is crucial for comprehending biological functions and processes.

Role of Chemical Bonds

Chemical reactions in biological systems involve the making and breaking of chemical bonds.
Strong and weak chemical bonds play vital roles in the chemistry of life.
The biological function of a molecule is closely related to its shape and the bonds it forms.

Importance of Water

Water's Unique Properties

Water's unique properties enable life on Earth.
Key concepts include polarity, hydrogen bonding, high specific heat, 'stickiness', ability to dissolve, ice's lower density, and pH.
Life depends on hydrogen bonds in water, which is a polar molecule with slightly charged regions.
Hydrogen bonds form between slightly positive hydrogen atoms and slightly negative atoms.
Polarity involves unequal sharing of electrons, with oxygen being negative and hydrogen being positive.

Hydrogen Bonding

Hydrogen bonds are crucial for proteins folding, DNA structure, and water's unique properties.
Proteins fold into specific shapes due to hydrogen bonds.
DNA forms a double helix structure because of hydrogen bonding.

High Specific Heat

Water's high specific heat allows it to absorb and retain energy.
Coastal regions have stable temperatures due to water's specific heat.
Earth's position in the 'Goldilocks zone' is maintained by water's specific heat.
Water's specific heat prevents rapid temperature changes, supporting diverse life forms.

Adhesion and Cohesion

Water exhibits adhesion (sticks to other substances) and cohesion (sticks to itself).
Adhesion allows water to climb up plants' vascular system through capillary action.
Cohesion is essential for water's surface tension and the ability to form droplets.
Adhesion and cohesion are vital for life, enabling swimming and water transport in plants.

Ability to Dissolve

Water is known as the universal solvent due to its ability to dissolve many substances.
Solutions are formed when one substance dissolves in another, creating a homogeneous mixture.
Polar solvents dissolve polar solutes, while nonpolar solvents dissolve nonpolar solutes.
Water's ability to dissolve various compounds supports life processes.

Chemistry of Water

Ice's Density and pH

Ice floats on water due to its lower density.
Fish live underneath ice, and its floating property prevents the world from getting colder.
A neutral solution has a pH of 7, with acids releasing hydrogen ions and bases removing them.

Universal Solvent and pH in Biology

Water's ability to dissolve substances makes it the universal solvent.
Blood, cytoplasm, and oceans are examples of solutions vital for life.
pH levels in the human body affect acidity, with most areas maintaining a pH of 7.

Water in Biology

Water's properties enable it to move from roots to leaves in plants.
Water's cohesive and adhesive behavior supports life processes.
Water's surface tension allows insects to stand on water surfaces.
Ice floats due to water molecules' cohesive behavior and hydrogen bonding.
Water's high specific heat means it can absorb and retain energy.
H2O's atoms are held together by covalent bonds.
Water's universal solvent property is enabled by its hydrogen bonds.

Introduction to Macromolecules

Macromolecules Overview

Macromolecules are large organic molecules found in living organisms.
They are essential for various biological functions.
Monomers are the building blocks of macromolecules.
Polymers are formed by joining monomers through covalent bonds.

Dehydration Synthesis and Hydrolysis

Dehydration Synthesis: Monomers join to form polymers with the release of water.
Hydrolysis: Polymers are broken down into monomers with the addition of water.
Enzymes are required to catalyze both processes.

Carbohydrates

Structure and Function of Carbohydrates

Carbohydrates serve as a source of energy and for structural purposes.
Monosaccharides are the monomers of carbohydrates.
Disaccharides and polysaccharides are formed by the bonding of multiple monosaccharides.
The ratio of elements in carbohydrates is 1:2:1 (C:H:O).

Types of Carbohydrates

Monosaccharides: Simple sugars like glucose, fructose, and galactose.
Disaccharides: Examples include maltose, lactose, and sucrose.
Polysaccharides: Complex carbohydrates like glycogen, starch, cellulose, and chitin.

Functions of Carbohydrates

Short-term energy storage in animals and energy storage in plants.
Provide support in organisms, such as cell walls in plants.
Act as transferable energy when consumed by animals.

Lipids

Lipids Overview

Lipids are a diverse group of macromolecules insoluble in water.
They play crucial roles in energy storage, insulation, and cell structure.

Types and Functions of Lipids

Triglycerides: Formed by glycerol and three fatty acids, categorized as saturated or unsaturated.
Phospholipids: Compose cell membranes with hydrophilic heads and hydrophobic tails.
Wax: Hydrophobic lipid that resists water, used for waterproofing.

Additional Lipid Functions

Long-term energy storage compared to carbohydrates.
Insulation in cold climate animals.
Building blocks of cell membranes and waterproofing.

Proteins in Biology

Proteins are essential macromolecules with diverse functions in living organisms.
Functions of proteins include structural support (e.g., hair, nails), movement (muscles), enzymatic activity, transportation of molecules, hormonal signaling, defense mechanisms (antibodies), and storage of amino acids.
Example: Hemoglobin, a protein, transports oxygen in the blood.

Protein Structure Levels

Proteins have four structural levels: primary, secondary, tertiary, and quaternary.
Primary structure: Linear sequence of amino acids determined by DNA.
Secondary structure: Local folding patterns like alpha-helix and beta-sheet.
Tertiary structure: Overall 3D shape influenced by R-group interactions.
Quaternary structure: Formed by the association of multiple polypeptide chains.
Example: Sickle cell anemia results from a single amino acid change in the primary structure.

Factors Holding Proteins Together

Proteins are held together by hydrogen bonds, ionic bonds, disulfide bridges, and hydrophobic interactions.
Denaturation disrupts protein structure through factors like pH, temperature, and salt concentration.
Some proteins can refold into their functional shape after denaturation.

"Disrupting the 3D structure of proteins can alter their function and activity levels significantly."

Amino Acids and Protein Building

Proteins are composed of amino acid monomers linked by peptide bonds.
There are 20 different amino acids with unique properties determined by their R-groups.
Amino acids can be nonpolar, polar, charged, large, or small.
Example: Cysteine forms disulfide bridges in proteins.

Nucleic Acids

Nucleic Acid Structure

Nucleic acids are polymers made of nucleotide monomers.
Nucleotides consist of a nitrogenous base, a phosphate group, and a 5-carbon sugar.
DNA and RNA are examples of nucleic acids with distinct functions.

Nucleotide Composition

Nucleotides are composed of a nitrogenous base (purines or pyrimidines), a phosphate group, and a 5-carbon sugar.
Purines (adenine, guanine) have a double-ring structure, while pyrimidines (cytosine, thymine, uracil) have a single-ring structure.
In DNA, adenine pairs with thymine, and guanine pairs with cytosine via hydrogen bonds.

DNA Structure and Function

DNA forms a double helix structure with hydrogen bonds between complementary base pairs.
The sequence of bases encodes genetic information passed from parent to offspring.
Adenosine Triphosphate (ATP) is a modified nucleotide crucial for energy transfer in cells.