General Biology Study Guide: Life, Evolution, and Chemistry of Life

Chapter 1: The Study of Life

Attributes of Life

Living organisms share several key characteristics that distinguish them from non-living matter.

• Order: Living things exhibit complex but ordered organization.

• Regulation: Organisms can regulate their internal environment (homeostasis).

• Growth and Development: Organisms grow and develop according to specific instructions coded in their DNA.

• Energy Processing: Living things obtain and use energy for maintenance and growth.

• Response to Environment: Organisms respond to environmental stimuli.

• Reproduction: Organisms reproduce their own kind.

• Evolutionary Adaptation: Populations evolve over generations through adaptations.

Biological Hierarchy and Emergent Properties

The biological hierarchy organizes life from the smallest to the largest scale, with each level exhibiting emergent properties not present at lower levels.

• Levels: Molecule → Organelle → Cell → Tissue → Organ → Organ System → Organism → Population → Community → Ecosystem → Biosphere

• Emergent Properties: New properties arise at each level due to the arrangement and interactions of parts. Example: A functioning heart can pump blood, but individual heart cells cannot.

Domains of Life

All living organisms are classified into three domains based on cell type and genetic characteristics.

• Bacteria: Prokaryotic, unicellular organisms.

• Archaea: Prokaryotic, often found in extreme environments.

• Eukarya: Eukaryotic cells, includes protists, fungi, plants, and animals.

Structure and Function in Biology

Structure and function are closely related in biology; the shape of a structure often determines its function.

• Example: The structure of red blood cells (biconcave shape) increases surface area for gas exchange.

Energy Transfer and Matter Recycling in Ecosystems

Energy flows through ecosystems, while matter is recycled.

• Producers: (e.g., plants) convert solar energy into chemical energy via photosynthesis.

• Consumers: (e.g., animals) obtain energy by eating other organisms.

• Decomposers: (e.g., fungi, bacteria) break down dead matter, returning nutrients to the environment.

• Ultimate Source of Energy: The sun.

Interactions in Biological Systems

Organisms interact with each other and their environment, forming complex networks.

• Examples: Predator-prey relationships, symbiosis, competition.

Natural Selection and Evolution

Natural selection is the process by which organisms better adapted to their environment tend to survive and produce more offspring, leading to evolution over time.

• Key Points: Variation exists in populations; traits that confer advantages increase in frequency.

• Example: Peppered moths during the Industrial Revolution in England.

Chapter 2: The Chemical Context of Life

Phases of Matter

Matter exists in three primary phases:

• Solid: Definite shape and volume.

• Liquid: Definite volume, takes shape of container.

• Gas: No definite shape or volume.

Elements and Compounds

Elements are pure substances consisting of one type of atom; compounds are substances formed from two or more elements chemically combined in fixed ratios.

• Example: Water (H2O) is a compound of hydrogen and oxygen.

Major Elements in the Human Body

Four elements make up about 96% of the human body:

• Oxygen (O)

• Carbon (C)

• Hydrogen (H)

• Nitrogen (N)

Atomic Structure

Atoms consist of a nucleus (protons and neutrons) and electrons in orbitals.

• Atomic Number (Z): Number of protons in the nucleus.

• Mass Number (A): Number of protons plus neutrons.

• Electrons: Negatively charged particles in orbitals around the nucleus.

Isotopes

Isotopes are atoms of the same element with different numbers of neutrons.

• Stable Isotopes: Do not decay.

• Radioactive Isotopes: Unstable, decay over time, used in medical imaging.

Chemical Bonds

Atoms combine via chemical bonds to form molecules.

• Ionic Bonds: Transfer of electrons from one atom to another.

• Covalent Bonds: Sharing of electron pairs between atoms.

• Polar Covalent Bonds: Unequal sharing of electrons.

• Non-polar Covalent Bonds: Equal sharing of electrons.

• Hydrogen Bonds: Weak attractions between a hydrogen atom and an electronegative atom (e.g., O or N).

Comparison of Bond Types

Bond Type	Strength	Example
Ionic	Strong (in dry conditions)	NaCl (table salt)
Covalent	Very strong	H2O (water)
Hydrogen	Weak	Between water molecules

Emergent Properties of Water

Water exhibits four emergent properties critical for life, largely due to hydrogen bonding:

• Cohesion: Water molecules stick together, aiding transport in plants.

• Moderation of Temperature: Water absorbs and releases heat slowly.

• Expansion Upon Freezing: Ice is less dense than liquid water, allowing it to float.

• Versatility as a Solvent: Water dissolves many substances, facilitating chemical reactions.

Acids, Bases, and pH

The pH scale measures the concentration of hydrogen ions ($[H^+]$) in a solution.

• Acid: Substance that increases $[H^+]$ in solution (pH < 7).

• Base: Substance that decreases $[H^+]$ in solution (pH > 7).

• pH Equation:

$\text{pH} = -\log_{10}[H^+]$

• Importance: Biological systems require stable pH for proper function; buffers help maintain pH.

Chapter 3: The Chemistry of Carbon and Macromolecules

Importance of Carbon

Carbon's unique bonding properties make it the backbone of biological molecules.

• Forms four covalent bonds, allowing for diverse molecular structures.

• Can form chains, rings, and branched molecules.

Carbon Skeletons and Isomers

Carbon skeletons vary in length and shape, and isomers are compounds with the same formula but different structures.

• Structural Isomers: Differ in covalent arrangement.

• Cis-trans Isomers: Differ in spatial arrangement around double bonds.

• Enantiomers: Mirror images of each other.

Functional Groups

Functional groups are specific groups of atoms attached to carbon skeletons that confer specific properties.

• Hydroxyl (-OH)

• Carbonyl (C=O)

• Carboxyl (-COOH)

• Amino (-NH2)

• Phosphate (-PO4)

Macromolecules: Classes and Functions

There are four major classes of biological macromolecules, each with unique functions and structures.

Class	Sub-class	Elements Present	Polarity	Examples	Function	Distinguishing Features
Carbohydrates	Monosaccharides, Disaccharides, Polysaccharides	C, H, O	Polar	Glucose, Starch	Energy storage, structure	Ring structures, glycosidic bonds
Lipids	Fats, Phospholipids, Steroids	C, H, O (sometimes P)	Mostly non-polar	Triglycerides, Cholesterol	Energy storage, membranes, signaling	Hydrophobic, ester bonds
Proteins	Polypeptides	C, H, O, N, (sometimes S)	Varies	Enzymes, Hemoglobin	Catalysis, structure, transport	Peptide bonds, 4 levels of structure
Nucleic Acids	DNA, RNA	C, H, O, N, P	Polar	DNA, RNA	Genetic information storage and transfer	Phosphodiester bonds, double helix (DNA)

Macromolecule Synthesis and Breakdown

Macromolecules are built and broken down by specific chemical reactions.

• Dehydration Synthesis: Joins monomers by removing water.

• Hydrolysis: Breaks polymers into monomers by adding water.

Protein Structure

Proteins have four levels of structure, each contributing to their function.

• Primary: Sequence of amino acids.

• Secondary: Local folding (alpha helices, beta sheets).

• Tertiary: Overall 3D shape.

• Quaternary: Association of multiple polypeptide chains.

Primary structure determines all higher levels of structure and thus the protein's function.