General Biology Study Guide: Foundations, Cell Structure, Membranes, Energy, and Metabolism

Introduction to Biology

Unity and Diversity of Life

Biology is the study of living organisms, their structure, function, growth, origin, evolution, and distribution. The unity and diversity of life are explained by evolutionary theory and the shared characteristics of living things.

• Common ancestry: Strong evidence for the common ancestry of all life includes universal biochemical processes and genetic code.

• Charles Darwin: Proposed natural selection as the mechanism for evolution, explaining both unity and diversity.

• Adaptation: Traits that enhance survival and reproductive success in specific environments.

• Scientific method: Involves observation, hypothesis formation, controlled experiments, and analysis.

Example: Darwin's finches in the Galápagos Islands show variation in beak shape adapted to different food sources.

Chemistry of Life

Atoms, Molecules, and Bonds

All living things are composed of atoms and molecules. Chemical bonds and interactions determine the structure and function of biological molecules.

• Elements: Most common elements in living organisms are carbon, hydrogen, oxygen, and nitrogen.

• Covalent bonds: Atoms share electrons; strong and stable.

• Hydrogen bonds: Weak attractions between polar molecules, important in water and biological macromolecules.

• Water: High specific heat, cohesion, adhesion, and solvent properties due to hydrogen bonding.

Example: Water's high specific heat helps regulate temperature in organisms and environments.

Biomolecules

Classes and Functions

Biological molecules are classified into four major groups: carbohydrates, lipids, proteins, and nucleic acids.

• Carbohydrates: Energy storage and structural support. Example: glucose, starch.

• Lipids: Hydrophobic molecules, energy storage, membrane structure. Example: triglycerides, phospholipids.

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

• Nucleic acids: DNA and RNA, store and transmit genetic information.

Example: Enzymes are proteins that catalyze biochemical reactions, lowering activation energy.

Cell Components

Prokaryotic vs. Eukaryotic Cells

Cells are the basic units of life. Prokaryotic cells lack a nucleus and membrane-bound organelles, while eukaryotic cells have both.

• Prokaryotes: Bacteria and Archaea; simple structure, no nucleus.

• Eukaryotes: Plants, animals, fungi, protists; complex structure, nucleus, organelles.

• Cell membrane: Phospholipid bilayer with embedded proteins, controls movement of substances.

• Organelles: Nucleus, mitochondria, chloroplasts, endoplasmic reticulum, Golgi apparatus.

Example: Mitochondria are the site of cellular respiration, producing ATP from glucose.

The Membrane

Structure and Transport

Cell membranes are selectively permeable barriers that regulate the movement of molecules.

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

• Transport proteins: Facilitate movement of ions and molecules across the membrane.

• Passive transport: Diffusion and osmosis; no energy required.

• Active transport: Requires energy (ATP) to move substances against concentration gradients.

Example: Sodium-potassium pump maintains electrochemical gradients in animal cells.

Energy and Metabolism

Enzymes and Metabolic Pathways

Metabolism includes all chemical reactions in cells, organized into pathways. Enzymes are biological catalysts that speed up reactions.

• Activation energy: Minimum energy required to start a reaction; enzymes lower this barrier.

• Substrate specificity: Enzymes bind specific substrates at their active sites.

• Competitive inhibition: Inhibitors compete with substrates for the active site.

• Allosteric regulation: Enzyme activity is modified by molecules binding at sites other than the active site.

Example: Amylase catalyzes the breakdown of starch into glucose.

Respiration and Photosynthesis

Energy Conversion in Cells

Cells convert energy through respiration and photosynthesis. Respiration breaks down organic molecules to produce ATP; photosynthesis converts light energy into chemical energy.

• Cellular respiration: Glycolysis, Krebs cycle, electron transport chain; produces ATP and releases CO2.

• Photosynthesis: Light-dependent reactions produce ATP and NADPH; Calvin cycle synthesizes sugars.

• Electron carriers: NADH and FADH2 transport electrons in respiration.

• Oxygen: Final electron acceptor in aerobic respiration; O2 produced in photosynthesis.

Example: ATP synthesis in mitochondria and chloroplasts uses proton gradients across membranes.

Animal Behavior and Ecology

Behavioral Adaptations and Evolution

Animal behavior is shaped by genetic and environmental factors, and evolves through natural selection.

• Innate behavior: Instinctive, genetically programmed actions.

• Learned behavior: Acquired through experience; includes imprinting and conditioning.

• Proximate causes: Immediate physiological mechanisms of behavior.

• Ultimate causes: Evolutionary reasons for behavior, enhancing survival and reproduction.

Example: Prairie dogs give warning calls to alert others of predators, an example of social behavior.

Tables

Comparison of Biomolecule Classes

Biomolecule	Monomer	Function	Example
Carbohydrate	Monosaccharide	Energy, structure	Glucose, starch
Lipid	Fatty acid, glycerol	Energy storage, membranes	Triglyceride, phospholipid
Protein	Amino acid	Enzymes, structure	Amylase, hemoglobin
Nucleic acid	Nucleotide	Genetic information	DNA, RNA

Key Equations

Biological Formulas

• Photosynthesis: $6CO_2 + 6H_2O + light \rightarrow C_6H_{12}O_6 + 6O_2$

• Cellular Respiration: $C_6H_{12}O_6 + 6O_2 \rightarrow 6CO_2 + 6H_2O + ATP$

• Water Potential: $\Psi = \Psi_s + \Psi_p$ where $\Psi$ is total water potential, $\Psi_s$ is solute potential, $\Psi_p$ is pressure potential.

Additional info:

• Some content inferred from context and standard biology curriculum, including definitions and examples.

• Questions in the file cover topics from chapters 1, 2, 3, 4, 5, 6, 8, 19, 38, and 39, which align with General Biology course topics.