Biology Study Guide: Foundations of Life, Chemistry, Water, Carbon, and Biological Moleculesh

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Chapter 1: Evolution, the Themes of Biology, and Scientific Inquiry

Cell Theory

The cell theory is a fundamental concept in biology that describes the properties of cells, the basic unit of life.

All living organisms are composed of one or more cells.
The cell is the basic unit of structure and organization in organisms.
All cells arise from pre-existing cells.

Prokaryotic vs. Eukaryotic Cells

Cells are classified as either prokaryotic or eukaryotic based on their structural differences.

Prokaryotic Cells: Lack a nucleus and membrane-bound organelles; DNA is found in the nucleoid region. Examples: Bacteria and Archaea.
Eukaryotic Cells: Have a true nucleus and membrane-bound organelles. Examples: Plants, Animals, Fungi, Protists.

Feature	Prokaryotic	Eukaryotic
Nucleus	No	Yes
Organelles	Few, not membrane-bound	Many, membrane-bound
Size	Small (1-10 μm)	Larger (10-100 μm)

Scientific Inquiry Process

The scientific inquiry process is a systematic approach to understanding the natural world.

Observation: Gathering information about phenomena.
Hypothesis: A testable explanation for an observation.
Prediction: A logical statement about what will happen if the hypothesis is correct.
Testing: Conducting experiments or further observations to test the hypothesis.

Variables in Experiments

Independent Variable: The factor that is changed or manipulated in an experiment.
Dependent Variable: The factor that is measured or observed in response to changes in the independent variable.

Chapter 2: The Chemical Context of Life

Atomic Number and Mass Number

Atomic Number (Z): Number of protons in an atom's nucleus. Determines the element.
Mass Number (A): Total number of protons and neutrons in the nucleus.

Example: An atom with 6 protons and 6 neutrons has an atomic number of 6 and a mass number of 12.

Isotopes

Isotopes: Atoms of the same element (same number of protons) but different numbers of neutrons.
Example: Carbon-12 and Carbon-14 are isotopes of carbon.

Valence Shell and Valence Electrons

Valence Shell: The outermost electron shell of an atom.
Valence Electrons: Electrons in the valence shell; determine chemical reactivity.

Electron Configuration and Ions

Atoms are stable when their valence shell is full (usually 8 electrons, the "octet rule").
If an atom gains electrons, it becomes a negatively charged ion (anion).
If an atom loses electrons, it becomes a positively charged ion (cation).

Ionic and Covalent Bonds

Ionic Bonds: Formed when electrons are transferred from one atom to another, resulting in oppositely charged ions that attract each other.
Covalent Bonds: Formed when two atoms share one or more pairs of electrons.

Hydrogen Bonds

Hydrogen Bond: A weak bond between a hydrogen atom (covalently bonded to an electronegative atom like oxygen) and another electronegative atom.
Important in water molecules, DNA, and proteins.

Chapter 3: Water and Life

Properties of Water

Lower Density as a Solid: Ice floats because it is less dense than liquid water.
High Heat of Evaporation: Water requires a lot of energy to change from liquid to gas.
High Specific Heat: Water can absorb or release large amounts of heat with little temperature change.
Solvent for Hydrophilic Molecules: Water dissolves many substances, especially polar and ionic compounds.
Cohesion and Adhesion: Water molecules stick to each other (cohesion) and to other surfaces (adhesion).

Hydrophilic and Hydrophobic

Hydrophilic: "Water-loving"; substances that dissolve easily in water (e.g., salts, sugars).
Hydrophobic: "Water-fearing"; substances that do not dissolve in water (e.g., oils, fats).

pH and Hydrogen Ion Concentration

pH: A measure of hydrogen ion concentration;
Acidic Solution: pH < 7; higher [H+]
Basic Solution: pH > 7; lower [H+]
Neutral Solution: pH = 7

Change in pH: Each unit change in pH represents a tenfold change in [H+].

Acids and Bases

Acid: Substance that increases [H+] in solution.
Base: Substance that decreases [H+] (or increases [OH-]) in solution.
Look for H+ or OH- in dissociation products to identify acids and bases.

Chapter 4: Carbon and the Molecular Diversity of Life

Isomers

Isomers: Molecules with the same molecular formula but different structures and properties.
Types: Structural isomers, cis-trans isomers, enantiomers.

Functional Groups

Recognize the following functional groups on molecules:

Hydroxyl (-OH)
Amine (-NH2)
Carboxyl (-COOH)
Carbonyl (C=O)
Methyl (-CH3)
Phosphate (-PO42-)
Sulfhydryl (-SH)

Chapter 5: The Structure and Function of Large Biological Molecules

Monomers of Biological Molecules

Carbohydrates: Monosaccharides (e.g., glucose)
Proteins: Amino acids
Nucleic Acids: Nucleotides
Lipids: Glycerol and fatty acids (not true polymers)

Polysaccharides: Functions and Organisms

Polysaccharide	Function	Organisms
Starch	Energy storage	Plants
Cellulose	Structural support	Plants
Glycogen	Energy storage	Animals, fungi
Chitin	Structural support	Fungi, arthropods

Saturated vs. Unsaturated Fatty Acids

Saturated Fatty Acids: No double bonds; solid at room temperature (e.g., butter).
Unsaturated Fatty Acids: One or more double bonds; liquid at room temperature (e.g., olive oil).

Protein Structure

Primary Structure: Sequence of amino acids.
Secondary Structure: Local folding (α-helix, β-sheet) due to hydrogen bonding.
Tertiary Structure: 3D shape formed by interactions among R groups.
Quaternary Structure: Association of multiple polypeptide chains.

Denaturation

Denaturation: Loss of protein's native structure due to heat, pH, or chemicals.
Leads to loss of function.

DNA vs. RNA

Feature	DNA	RNA
Sugar	Deoxyribose	Ribose
Bases	A, T, C, G	A, U, C, G
Strands	Double-stranded	Single-stranded

Nucleotide Components

Phosphate group
Pentose sugar (deoxyribose in DNA, ribose in RNA)
Nitrogenous base (adenine, guanine, cytosine, thymine/uracil)