General Biology: Core Concepts and Cell Structure Study Guide

Topic 1: Chemical Context for Life

Introduction

This topic explores the chemical principles underlying biological systems, focusing on the structure and properties of matter, atoms, molecules, and their roles in living organisms.

• Hierarchy of Life: Living things are organized in a structural hierarchy, from atoms and molecules to cells, tissues, organs, and organisms.

• Atoms: The basic unit of matter; atoms are the foundation for both non-living and living matter. Atomic structure includes protons, neutrons, and electrons.

• Matter: Anything that occupies space and has mass; composed of elements and compounds.

• Chemical Elements: Pure substances consisting of only one type of atom. Examples: Carbon (C), Oxygen (O), Hydrogen (H).

• Molecules & Compounds: Molecules are two or more atoms bonded together; compounds are molecules with different elements.

• Atomic Number & Mass: Atomic number is the number of protons; atomic mass is the sum of protons and neutrons.

• Electron Shells: Electrons are arranged in shells around the nucleus; their arrangement determines chemical reactivity.

• Chemical Bonds: Covalent (sharing electrons), ionic (transfer of electrons), and hydrogen bonds (weak attraction between polar molecules).

• Water: The molecule that supports all life; its polarity and hydrogen bonding make it essential for biological processes.

• Properties of Water: Cohesion, adhesion, high specific heat, solvent abilities, and role in Earth's habitability.

• pH: Measure of hydrogen ion concentration; scale ranges from 0 (acidic) to 14 (basic). $pH = -\log_{10}[H^+]$

• Buffers: Substances that minimize changes in pH.

• Ocean Acidification: Decrease in ocean pH due to increased CO2 absorption, affecting marine life.

Example:

Water's high specific heat helps regulate Earth's climate and maintain stable environments for life.

Topic 2: Structure and Function of Macromolecules

Introduction

This topic examines the major biological macromolecules, their structures, and their functions in living organisms.

• Carbon Backbone: Carbon's ability to form four covalent bonds makes it the backbone of organic molecules.

• Organic Molecules: Molecules containing carbon and hydrogen; include carbohydrates, lipids, proteins, and nucleic acids.

• Functional Groups: Specific groups of atoms within molecules that confer particular chemical properties (e.g., hydroxyl, carboxyl, amino).

• Carbohydrates: Polysaccharides; provide energy and structural support. Example: Glucose, Starch.

• Proteins: Made of amino acids; perform structural, enzymatic, and regulatory functions.

• Nucleic Acids: DNA and RNA; store and transmit genetic information.

• Lipids: Fats, oils, and phospholipids; important for energy storage and membrane structure.

Example:

Proteins such as enzymes catalyze biochemical reactions essential for life.

Topic 3: Membrane Structure & Function

Introduction

This topic covers the structure and function of biological membranes, including their composition, fluidity, and transport mechanisms.

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

• Plasma Membrane: Composed of a phospholipid bilayer with embedded proteins; regulates entry and exit of substances.

• Fluid Mosaic Model: Describes the dynamic nature of the membrane, with proteins and lipids moving laterally.

• Membrane Proteins: Integral and peripheral proteins perform transport, signaling, and structural functions.

• Transport Across Membranes:

  • Passive Transport: Movement of substances down their concentration gradient without energy input (simple & facilitated diffusion, osmosis).

  • Active Transport: Movement against the concentration gradient using energy (ATPases, co-transport).

  • Bulk Transport: Endocytosis (into cell) and exocytosis (out of cell); e.g., LDL uptake.

• Membrane Potential: Electrical potential difference across the membrane due to ion distribution.

Example:

Facilitated diffusion allows glucose to enter cells via specific transport proteins.

Topic 4: Features of the Cell

Introduction

This topic explores the diversity, structure, and function of cells, including their organelles and differences between cell types.

• Cells: Fundamental units of life; all living things are composed of cells.

• Cellular Life: Diversity based on energy sources (carbon, oxygen).

• Microscopy: Light and electron microscopes are used to study cell structure.

• Three Domains of Life: Bacteria, Archaea, Eukarya.

• Prokaryotic vs. Eukaryotic Cells: Prokaryotes lack a nucleus and membrane-bound organelles; eukaryotes have both.

• Endosymbiosis Theory: Explains origin of mitochondria and chloroplasts from ancestral prokaryotes.

• Surface Area to Volume Ratio: Limits cell size; smaller cells have higher ratios, facilitating efficient exchange.

• Plant vs. Animal Cells: Plant cells have cell walls, chloroplasts, and large vacuoles; animal cells do not.

• Cell Organelles: Nucleus, ER, ribosomes, Golgi apparatus, lysosomes, mitochondria, chloroplasts, peroxisomes.

• Chloroplasts & Mitochondria: Both generate energy; mitochondria perform cellular respiration, chloroplasts conduct photosynthesis.

• Cytoskeleton: Microtubules, microfilaments, and intermediate filaments provide structural support and facilitate movement.

• Extracellular Matrix (ECM): Provides structural and biochemical support to surrounding cells.

Example:

Chloroplasts convert solar energy into chemical energy via photosynthesis in plant cells.

HTML Table: Comparison of Prokaryotic and Eukaryotic Cells

Feature	Prokaryotic Cells	Eukaryotic Cells
Nucleus	Absent	Present
Membrane-bound Organelles	Absent	Present
Cell Size	Generally smaller	Generally larger
Examples	Bacteria, Archaea	Plants, Animals, Fungi, Protists