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 hierarchical manner (biosphere → ecosystem → molecules).

• Information: Genetic information is stored and transmitted in living organisms.

• Energy and Matter: Life requires energy transfer and transformation.

• 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, and experimentation.

• 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 organisms better adapted to their environment tend to survive and reproduce.

• Natural Selection: The process by which traits that enhance survival and reproduction become more common in successive generations.

Chapter 2: Chemical Foundations of Life

Atoms, Elements, and Molecules

All matter is composed of atoms, which combine to form elements and molecules. The properties of atoms determine the behavior of molecules in biological systems.

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

• Electron Shells: Electrons are arranged in shells; the first shell holds 2 electrons, the second holds up to 8, etc.

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

• Isotopes: Atoms of the same element with different numbers of neutrons.

Chemical Bonds and Interactions

Atoms interact to form molecules through various types of chemical bonds.

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

• 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 macromolecules.

Properties of Water

Water is essential for life due to its unique properties arising from hydrogen bonding.

• Cohesion: Water molecules stick to each other.

• Adhesion: Water molecules stick to other surfaces.

• High Specific Heat: Water resists changes in 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 a 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 Macromolecules

Macromolecules and Their Monomers

Cells 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; composed of fatty acids and glycerol

Linkages and Reactions

• Glycosidic Linkages: Bonds between carbohydrate monomers.

• Peptide Bonds: Bonds between amino acids in proteins.

• Phosphodiester Bonds: Bonds between nucleotides in nucleic acids.

• Dehydration Reaction: Joins monomers by removing water.

• Hydrolysis: Breaks polymers into monomers by adding water.

Isomers and Molecular Shape

• Isomers: Molecules with the same formula but different structures; three types: structural, cis-trans, and enantiomers.

• Molecular Shape: Influences biological activity and function.

Gene Expression and DNA vs. RNA

• Central Dogma: DNA → RNA → Protein

• DNA: Double-stranded, stores genetic information.

• RNA: Single-stranded, involved in protein synthesis.

Chapter 4: Cell Structure and Function

Cell Membranes and Phospholipids

Cell membranes are composed of a phospholipid bilayer, which provides a barrier and allows compartmentalization.

• Phospholipids: Have hydrophilic heads and hydrophobic tails.

• Bilayer: Hydrophobic tails face inward, hydrophilic heads face outward.

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: Detoxification; manage reactive oxygen species.

• Mitochondria: ATP generation, cellular respiration.

• Chloroplasts: Photosynthesis in plant cells.

• Nucleus: DNA storage and gene expression.

• Endoplasmic Reticulum (ER):

  • Rough ER: Protein synthesis, ribosome factory.

  • Smooth ER: Lipid synthesis, detoxification, Ca2+ storage.

• Golgi Apparatus: Protein modification, sorting, and shipping.

• Cytoskeleton: Cell structure, movement, and transport.

Protein Targeting and Transport

Proteins are directed to specific locations in the cell based on signals and pathways.

• Endomembrane System: Includes ER, Golgi, vesicles, and plasma membrane.

• Protein Export Pathway: DNA → mRNA → Ribosome (Rough ER) → Golgi → Vesicle → Cell membrane

Endosymbiotic Theory

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

• Evidence: Double membranes, own DNA, semi-independent reproduction.

Summary Table: Macromolecules and Their Monomers

Macromolecule	Monomer	Polymer	Bond Type
Proteins	Amino Acids	Polypeptides	Peptide Bonds
Carbohydrates	Monosaccharides	Polysaccharides	Glycosidic Linkages
Nucleic Acids	Nucleotides	DNA/RNA	Phosphodiester Bonds
Lipids	Fatty Acids & Glycerol	Triglycerides, Phospholipids	Ester Linkages

Additional info:

• Some content was expanded for clarity and completeness, including definitions and examples.

• Table reconstructed to summarize macromolecule properties.