General Biology: Foundations and Key Concepts – Study Guide

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General Biology: Foundations and Key Concepts

Introduction

This study guide covers foundational topics in General Biology, including the properties of macromolecules, cell structure and function, levels of biological organization, and basic biochemistry. The content is structured to help students prepare for exams by reviewing key definitions, processes, and examples relevant to introductory college biology.

Macromolecules and Their Properties

Hydrophilic and Hydrophobic Properties

Hydrophilic molecules are attracted to water and can dissolve in it due to their polar nature.
Hydrophobic molecules repel water and do not dissolve in it, typically because they are nonpolar.
Amphipathic molecules possess both hydrophilic and hydrophobic regions, such as phospholipids in cell membranes.
Example: Phospholipids form bilayers in cell membranes due to their amphipathic nature.

Macromolecules as Polymers

Polymers are large molecules made by joining many smaller units (monomers).
Examples: Polysaccharides (carbohydrates), proteins, and nucleic acids are polymers. Lipids are not true polymers.

Dehydration and Hydrolysis Reactions

Dehydration reaction: Builds larger molecules by removing a water molecule to form a new bond.
Hydrolysis reaction: Breaks down molecules by adding water to split bonds.
Equation for dehydration synthesis:

DNA Structure and Base Pairing

Base Pairing Rules

Adenine (A) pairs with Thymine (T) via two hydrogen bonds.
Guanine (G) pairs with Cytosine (C) via three hydrogen bonds.
Mnemonic: "A-T, G-C"

Cellular Organization and Function

Levels of Biological Organization

Cell → Tissue → Organ → Organ system → Organism → Population → Community → Ecosystem → Biosphere
Example: Muscle cell → Muscle tissue → Heart (organ) → Circulatory system → Human (organism)

Prokaryotes vs. Eukaryotes

Prokaryotes: Lack a nucleus and membrane-bound organelles (e.g., bacteria, archaea).
Eukaryotes: Have a nucleus and membrane-bound organelles (e.g., plants, animals, fungi, protists).
Similarities: Both have cell membranes, cytoplasm, ribosomes, and genetic material.

Cell Membrane Structure

Phospholipid bilayer: Main component of cell membranes, with hydrophilic heads facing outward and hydrophobic tails inward.
Fluid Mosaic Model: Describes the dynamic and flexible nature of the membrane, with proteins embedded or attached.
Membrane proteins: Can be integral (embedded) or peripheral (attached to the surface).

Transport Across Membranes

Types of Transport

Passive transport: Movement of molecules down their concentration gradient without energy input (e.g., diffusion, facilitated diffusion, osmosis).
Active transport: Movement of molecules against their concentration gradient, requiring energy (usually ATP).
Transport proteins: Include channels, carriers, and pumps that assist in moving substances across membranes.

Key Terms

Osmosis: Diffusion of water across a selectively permeable membrane.
Endocytosis and Exocytosis: Processes for bulk transport of materials into (endocytosis) or out of (exocytosis) the cell.

Biological Molecules and Elements

Major Elements in Living Organisms

CHNOPS: Carbon, Hydrogen, Nitrogen, Oxygen, Phosphorus, Sulfur are the most abundant elements in living things.
Isotopes: Atoms of the same element with different numbers of neutrons (e.g., S and S).

Atomic Structure

Protons: Positively charged particles in the nucleus.
Neutrons: Neutral particles in the nucleus.
Electrons: Negatively charged particles orbiting the nucleus.
Atomic number: Number of protons in an atom.
Mass number: Sum of protons and neutrons.

Chemical Bonds

Covalent bonds: Atoms share electrons.
Ionic bonds: Transfer of electrons from one atom to another.
Hydrogen bonds: Weak attractions between a hydrogen atom and an electronegative atom (e.g., in water).
Polar vs. Nonpolar Covalent Bonds: Polar bonds have unequal sharing of electrons; nonpolar bonds have equal sharing.

Enzymes and Metabolism

Enzyme Function

Enzymes: Biological catalysts that speed up chemical reactions by lowering activation energy. (Enzymes are proteins that play a crucial role in biological processes)
Lactase deficiency: Leads to lactose intolerance, where individuals cannot digest lactose in dairy products.

Metabolic Pathways

Catabolism: Breakdown of molecules to release energy.
Anabolism: Synthesis of complex molecules from simpler ones, requiring energy. (Anabolism builds complex molecules from simple ones.
Why it's important: It helps your body grow, heal itself, and maintain its cells. )

Energy and Thermodynamics

ATP and Energy Storage

ATP (Adenosine Triphosphate): Main energy currency of the cell.
Energy is stored in the high-energy phosphate bonds of ATP.

Thermodynamics in Biology

First Law: Energy cannot be created or destroyed, only transformed.
Second Law: Every energy transfer increases the entropy (disorder) of the universe.

Tables and Comparisons

Comparison of Prokaryotic and Eukaryotic Cells

Feature	Prokaryotes	Eukaryotes
Nucleus	Absent	Present
Membrane-bound organelles	Absent	Present
Cell size	Small (1-10 μm)	Larger (10-100 μm)
Examples	Bacteria, Archaea	Plants, Animals, Fungi, Protists

Major Macromolecules and Their Functions

Macromolecule	Monomer	Function
Carbohydrates	Monosaccharides	Energy storage, structure
Proteins	Amino acids	Enzymes, structure, transport
Nucleic acids	Nucleotides	Genetic information storage
Lipids	Glycerol, fatty acids	Membranes, energy storage

Functional Group	Structure	Functional Characteristic	Biological Example

Hydroxyl

–OH

Makes molecules polar and hydrophilic (dissolves in water)

Found in alcohols and glucose

Carboxyl

–COOH

Acts as an acid (can donate H⁺); lowers pH

Found in amino acids and fatty acids

Amino

–NH₂

Acts as a base (can accept H⁺); raises pH

Found in amino acids and proteins

Phosphate

–PO₄²⁻

Highly negative; used to store/release energy

Found in ATP and DNA/RNA

Carbonyl

C=O

Makes molecules polar; helps with reactivity

Found in ketones and aldehydes (like in sugars)

Methyl

–CH₃

Nonpolar; used to turn genes on/off (epigenetics)

Found in DNA methylation

Sulfhydryl

–SH

Forms disulfide bridges that stabilize protein shape

Found in cysteine (an amino acid)

Additional info:

Some content was inferred and expanded for clarity and completeness, such as the full definitions of macromolecules, the structure of the cell membrane, and the comparison tables.
Questions and prompts from the file were converted into explanatory notes and organized by topic for study purposes.