Exam 1 Study Guide: Foundations of Biology

Biology: The Study of Life

Scientific Reasoning

• Scientific reasoning involves using evidence-based methods to understand natural phenomena.

• Key steps include observation, hypothesis formation, experimentation, data analysis, and drawing conclusions.

• Example: Testing whether plants grow faster under blue light by setting up controlled experiments.

Properties of Life

• All living things share several fundamental properties:

• Cellular organization: Composed of one or more cells.

• Metabolism: Ability to acquire and use energy.

• Homeostasis: Regulation of internal environment.

• Growth and development: Increase in size and complexity.

• Reproduction: Ability to produce new organisms.

• Response to stimuli: Reacting to environmental changes.

• Evolutionary adaptation: Populations change over generations.

Levels of Organization

• Biological systems are organized hierarchically:

• Atoms → Molecules → Organelles → Cells → Tissues → Organs → Organ systems → Organisms → Populations → Communities → Ecosystems → Biosphere

Three Major Theories in Biology

• Cell Theory: All living things are composed of cells; cells are the basic unit of life.

• Theory of Evolution by Natural Selection: Species change over time through differential survival and reproduction.

• Chromosome Theory of Inheritance: Genes are located on chromosomes and are the basis of inheritance.

Central Dogma of Molecular Biology

• Describes the flow of genetic information:

• DNA → RNA → Protein

• Transcription: DNA is transcribed to RNA.

• Translation: RNA is translated to protein.

Chemical Foundation of Life

Elements and Atoms

• Element: A pure substance consisting of one type of atom.

• The four most important elements in biology: Carbon (C), Hydrogen (H), Oxygen (O), Nitrogen (N).

• Atom: The smallest unit of an element, composed of protons, neutrons, and electrons.

Chemical Reactions

• Chemical reactions involve the rearrangement of atoms to form new substances.

• Reactants: Substances present before the reaction.

• Products: Substances formed as a result of the reaction.

Chemical Bonds

• Covalent bonds: Atoms share electrons.

• Polar covalent bonds: Unequal sharing of electrons (e.g., in water).

• Non-polar covalent bonds: Equal sharing of electrons (e.g., in O2).

• Ionic bonds: Transfer of electrons from one atom to another, forming ions.

• Hydrogen bonds: Weak attractions between a hydrogen atom and an electronegative atom (e.g., between water molecules).

• Van der Waals interactions: Weak, transient attractions between molecules.

Water Molecule and Its Properties

• Water (H2O) is a polar molecule with unique properties:

• Cohesion: Water molecules stick together.

• Adhesion: Water molecules stick to other substances.

• High specific heat: Resists temperature changes.

• Excellent solvent: Dissolves many substances.

• Ice is less dense than liquid water: Due to hydrogen bonding.

pH, Buffers, Acids, and Bases

• pH: Measures hydrogen ion concentration; scale from 0 (acidic) to 14 (basic).

• Acids: Donate H+ ions (lower pH).

• Bases: Accept H+ ions (raise pH).

• Buffers: Substances that minimize changes in pH.

• Equation:

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

Hydrocarbons and Isomers

• Hydrocarbons: Molecules consisting only of carbon and hydrogen.

• Isomers: Compounds with the same molecular formula but different structures.

• Types of isomers: structural, geometric (cis-trans), and enantiomers.

Functional Groups

• Groups of atoms attached to carbon skeletons that give molecules specific properties.

Functional Group	Structure	Properties
Hydroxyl	-OH	Polar, forms hydrogen bonds
Carbonyl	>C=O	Polar, found in sugars
Carboxyl	-COOH	Acidic, donates H+
Amino	-NH2	Basic, accepts H+
Sulfhydryl	-SH	Forms disulfide bonds
Phosphate	-PO4	Contributes negative charge
Methyl	-CH3	Nonpolar, affects gene expression

Biological Molecules: Proteins, Carbohydrates, and Lipids

Major Macromolecules

• Four major classes: Proteins, Carbohydrates, Lipids, Nucleic Acids.

Monomers and Polymers

• Monomers: Small building blocks (e.g., amino acids, monosaccharides, nucleotides).

• Polymers: Large molecules made by joining monomers (e.g., proteins, polysaccharides, nucleic acids).

Reactions That Create and Break Macromolecules

• Dehydration synthesis (condensation): Joins monomers by removing water.

• Hydrolysis: Breaks polymers into monomers by adding water.

Enzymes and Specificity

• Enzymes: Biological catalysts that speed up chemical reactions.

• Highly specific for their substrates due to their active site structure.

Carbohydrates

• Monosaccharides: Simple sugars (e.g., glucose, fructose).

• Disaccharides: Two monosaccharides joined (e.g., sucrose).

• Polysaccharides: Long chains (e.g., starch, glycogen, cellulose).

• Sugar types: triose (3C), pentose (5C), hexose (6C).

Lipids

• Hydrophobic molecules, not true polymers.

• Types: fats (triglycerides), phospholipids, steroids.

• Fats: Glycerol + 3 fatty acids; energy storage.

• Phospholipids: Glycerol + 2 fatty acids + phosphate; major component of cell membranes.

• Steroids: Four fused rings (e.g., cholesterol).

Proteins

• Polymers of amino acids.

• Levels of structure: primary, secondary, tertiary, quaternary.

• Functions: enzymes, structure, transport, signaling, defense.

Nucleic Acids

Basic Organization

• Nucleic acids are polymers of nucleotides.

• Each nucleotide: phosphate group, pentose sugar, nitrogenous base.

What is a Nucleic Acid?

• Macromolecules that store and transmit genetic information.

• Two main types: DNA (deoxyribonucleic acid) and RNA (ribonucleic acid).

DNA vs. RNA

• DNA: Double-stranded, deoxyribose sugar, bases A, T, C, G.

• RNA: Single-stranded, ribose sugar, bases A, U, C, G.

• DNA stores genetic information; RNA is involved in protein synthesis and gene regulation.

DNA and RNA Structure

• DNA: Double helix, antiparallel strands, complementary base pairing (A-T, C-G).

• RNA: Usually single-stranded, can form complex structures.