General Biology Exam 1 Review: Core Concepts and Cellular Foundations

Chapter 1: Themes and Methods in Biology

Major Themes of Life

Biology is the study of living organisms and their interactions with the environment. Understanding the major themes of life provides a foundation for all biological study.

• Organization: Life is organized in a hierarchy (biosphere → ecosystem → molecules).

• Information: Genetic information is stored and transmitted in DNA.

• Energy and Matter: Living things require energy and cycle matter.

• Interactions: Organisms interact with each other and their environment.

• Evolution: Populations evolve over time through natural selection.

Approaches in Biology

• Scientific Method: A systematic approach to investigation involving observation, hypothesis formation, experimentation, and analysis.

• Controlled Experiment: An experiment in which only one variable is changed at a time, while all others are kept constant.

Evolution and Natural Selection

Evolution explains the diversity of life and is driven by natural selection, where advantageous traits become more common in a population over generations.

• Natural Selection: The process by which organisms better adapted to their environment tend to survive and produce more offspring.

Chapter 2: Chemical Foundations of Life

Atoms, Elements, and Chemical Bonds

Atoms are the basic units of matter, and their structure determines the properties of elements and molecules.

• Atomic Number: The number of protons in an atom, which defines the element.

• Electron Shells: Electrons are arranged in shells around the nucleus. The first shell holds 2 electrons, the second holds 8, etc.

• Valence Electrons: Electrons in the outermost shell; determine chemical reactivity.

• Covalent Bonds: Atoms share electrons to fill their valence shell.

• Ionic Bonds: Atoms transfer electrons, resulting in charged ions that attract each other.

• Hydrogen Bonds: Weak attractions between partially charged regions of molecules, important in water and biological molecules.

Properties of Water

Water is essential for life due to its unique chemical properties.

• Polarity: Water molecules have a partial positive and negative end, allowing hydrogen bonding.

• Cohesion and Adhesion: Water molecules stick to each other (cohesion) and to other surfaces (adhesion).

• High Specific Heat: Water resists temperature changes, helping regulate climate and body temperature.

• Evaporative Cooling: As water evaporates, it removes heat from surfaces.

Acids, Bases, and pH

The pH scale measures the concentration of hydrogen ions in a solution.

• Acid: A substance that increases H+ concentration in solution.

• Base: A substance that decreases H+ concentration.

• pH Scale: Ranges from 0 (most acidic) to 14 (most basic); pH 7 is neutral.

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

Chapter 3: Biological Molecules

Macromolecules and Their Monomers

Living organisms are composed of four major classes of macromolecules, each with specific monomers and functions.

• Proteins: Monomer: Amino Acids; Polymer: Polypeptides

• Carbohydrates: Monomer: Monosaccharides ("one" sugar); Polymer: Polysaccharides ("many" sugars)

• Nucleic Acids: Monomer: Nucleotides; Polymer: DNA/RNA polynucleotides

• Lipids: Not true polymers; include fats, oils, and phospholipids

Isomers and Molecular Shape

Isomers are molecules with the same chemical formula but different structures, affecting their biological activity.

• Structural Isomers: Differ in the arrangement of atoms.

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

• Enantiomers: Mirror-image isomers, important in drug activity.

Linkages and Hydrolysis

Macromolecules are formed by dehydration reactions and broken down by hydrolysis.

• Glycosidic Linkages: Join monosaccharides in carbohydrates.

• Peptide Bonds: Join amino acids in proteins.

• Phosphodiester Bonds: Join nucleotides in nucleic acids.

Levels of Protein Structure

Proteins have four levels of structure that determine their function.

• Primary: Sequence of amino acids.

• Secondary: Alpha helices and beta sheets formed by hydrogen bonding.

• Tertiary: 3D folding due to side chain interactions.

• Quaternary: Multiple polypeptide chains assembled together.

ATP: Cellular Energy Currency

ATP (Adenosine Triphosphate) stores and transfers energy within cells.

• Energy Release: Energy is released when ATP is hydrolyzed to ADP and phosphate.

Chapter 4: Cell Structure and Function

Cell Membranes and Phospholipids

Cell membranes are composed of a phospholipid bilayer, providing a barrier and controlling movement of substances.

• Phospholipid Bilayer: Hydrophilic heads face outward, hydrophobic tails face inward.

• Membrane Proteins: Facilitate transport and communication.

Cell Organelles and Their Functions

Organelles are specialized structures within cells that perform distinct functions.

• Ribosomes: Protein synthesis; can be bound (to Rough ER) or free (in cytosol).

• Vacuoles: Storage and transport; larger in plant cells.

• Vesicles: Transport materials within the cell.

• Lysosomes: Digestive enzymes break down waste and foreign material.

• Peroxisomes: Break down fatty acids and detoxify harmful substances.

• Mitochondria: ATP generation, cellular respiration.

• Chloroplasts: Photosynthesis in plant cells.

• Nucleus: Contains DNA, controls cell activities.

• Endoplasmic Reticulum (ER):

  • Rough ER: Protein synthesis, ribosome-studded.

  • Smooth ER: Lipid synthesis, detoxification.

• Golgi Apparatus: Modifies, sorts, and ships proteins and lipids.

• Cytoskeleton: Provides structure, enables movement.

Protein Transport and Secretion

Proteins are synthesized and transported through a series of organelles before reaching their final destination.

• Pathway: DNA → mRNA → Ribosome (Rough ER) → Golgi Apparatus → Cell membrane or secretion.

Endosymbiotic Theory

The endosymbiotic theory explains the origin of mitochondria and chloroplasts as formerly independent prokaryotes engulfed by ancestral eukaryotic cells.

• Evidence: Both have their own DNA and reproduce independently within the cell.

Table: Comparison of Cell Organelles

Organelle	Main Function	Present in
Nucleus	Stores genetic material (DNA)	All eukaryotes
Ribosome	Protein synthesis	All cells
Mitochondria	ATP production	All eukaryotes
Chloroplast	Photosynthesis	Plants, algae
Golgi Apparatus	Protein/lipid modification and shipping	All eukaryotes
Lysosome	Digestion and waste removal	Animal cells

Additional info: Some explanations and examples have been expanded for clarity and completeness.