Unit 1-4 Study Guide

Biology: The Study of Scientific Life

Biology and Its Subfields

Biology is the scientific study of life, encompassing the structure, function, reproduction, evolution, and interactions of living organisms. Major subfields include:

• Cell Biology: Study of cell structure and function

• Genetics: Study of heredity and gene function

• Evolution: Study of changes in organisms over generations

• Ecology: Study of organisms' interactions with each other and their environment

• Anatomy/Physiology: Study of organism structure and function

• Microbiology: Study of microscopic organisms

• Molecular Biology: Study of biological molecules and processes

• Biotechnology: Application of biological knowledge for technological advances

Characteristics of Life

• Organization: Living things are highly organized, from molecules to cells to organisms.

• Cells and DNA: All life is cellular and uses DNA as genetic material.

• Metabolism/Energy Use: Life requires energy for growth, maintenance, and reproduction.

• Regulation/Homeostasis: Organisms maintain stable internal conditions.

• Response to Environment: Organisms sense and respond to stimuli.

• Growth and Development: Organisms grow and develop according to genetic instructions.

• Reproduction: Life reproduces, passing genetic information to offspring.

• Evolutionary Adaptation: Populations change over generations, adapting to environments.

The Three Domains of Life

All life is classified into three domains based on cellular structure and genetics:

• Bacteria: Prokaryotic, no nucleus, diverse environments

• Archaea: Prokaryotic, distinct biochemistry, often extremophiles

• Eukarya: Eukaryotic, nucleus and organelles; includes animals, plants, fungi, protists

Levels of Biological Organization

Biology is organized hierarchically from smallest to largest:

• Molecules → Organelles → Cells → Tissues → Organs → Organ Systems → Organisms → Populations → Communities → Ecosystems → Biosphere

• Emergent properties arise at each level due to interactions among components.

Five Themes of Biology

• Evolution: Explains unity and diversity of life

• Information Flow: DNA → RNA → Protein (central dogma)

• Structure/Function: Biological structures are adapted to their functions

• Transformation of Matter and Energy: Life requires energy and matter cycling

• Systems Interactions: Components interact at all levels

The Chemical Basis of Life

Atoms, Elements, and Bonds

• Element: Pure substance of one kind of atom (e.g., C, O, Na)

• Atom: Smallest unit of an element

• Covalent Bonds: Atoms share electrons (e.g., H2, O2, CO2)

• Ionic Bonds: Electron transfer creates charged ions (e.g., NaCl)

Water and Its Properties

• Cohesion: Water molecules stick to each other (surface tension)

• Adhesion: Water molecules stick to other substances

• Hydrogen Bonding: Responsible for water's unique properties

pH and Buffers

• pH: Measures hydrogen ion concentration; scale from 0 (acidic) to 14 (basic)

• Buffers: Substances that resist pH changes

The Molecules of Cells

Macromolecules and Their Building Blocks

• Proteins: Polymers of amino acids

• Nucleic Acids: Polymers of nucleotides (DNA, RNA)

• Carbohydrates: Simple sugars and polysaccharides

• Lipids: Not true polymers, but form aggregates (e.g., fats, phospholipids)

A Tour of the Cell

Prokaryotic vs Eukaryotic Cells

• Prokaryotic Cells: No nucleus, simple structure (Bacteria, Archaea)

• Eukaryotic Cells: Nucleus, membrane-bound organelles (Eukarya)

The Working Cell

Membrane Structure and Transport

• Fluid Mosaic Model: Phospholipid bilayer with embedded proteins

• Facilitated Diffusion: Passive transport via protein channels for specific molecules

How Cells Harvest Chemical Energy

Cellular Respiration and Redox Reactions

Cellular respiration is the process by which cells extract energy from glucose:

• Overall equation: $\mathrm{C_6H_{12}O_6 + 6O_2 \rightarrow 6CO_2 + 6H_2O + ATP + \text{heat}}$

• Redox reactions transfer electrons, releasing energy for ATP synthesis

• Efficiency of cellular respiration is about 34%

Photosynthesis: Using Light to Make Food

Leaf and Chloroplast Structure

• Leaf: Main photosynthetic tissue

• Chloroplast: Contains inner/outer membranes, stroma, thylakoids

• Three compartments: thylakoid space, thylakoid membrane, stroma

The Cellular Basis of Reproduction and Inheritance

Cell Division: Mitosis and Meiosis

• Cell Division: Enables growth, repair, and reproduction

• Mitosis: Produces genetically identical cells for growth/repair

• Meiosis: Produces haploid gametes, increases genetic diversity

Patterns of Inheritance

Mendelian Genetics and Punnett Squares

• Genotype: Genetic makeup (allele combinations)

• Phenotype: Observable traits

• Punnett Square: Predicts offspring genotype and phenotype ratios

Molecular Biology of the Gene

Central Dogma and DNA as Genetic Material

• Central Dogma: Information flows from DNA → RNA → Protein

• Replication: DNA is copied for cell division

• Transcription: DNA is transcribed to RNA

• Translation: RNA is translated to protein

The Genetic Code

• Triplet Code: Three-base codons specify amino acids

• Redundant: Multiple codons for most amino acids

• Universal: Nearly all organisms use the same code

• Start/Stop Codons: Define where translation begins and ends

Population Ecology

Population Structure and Dynamics

• Population Structure: Age and sex distribution affects growth

• Population Growth: Exponential (J-shaped) or logistic (S-shaped)

• Carrying Capacity (K): Maximum sustainable population size

Summary Table: Key Biological Concepts

Topic	Key Concept	Example/Application
Central Dogma	DNA → RNA → Protein	Gene expression
Cellular Respiration	Glucose + O2 → CO2 + H2O + ATP	Energy for cells
Photosynthesis	CO2 + H2O + light → Glucose + O2	Plant energy capture
Mitosis	2 identical cells	Growth, repair
Meiosis	4 haploid cells	Gamete formation
Punnett Square	Predicts inheritance	Genotype/phenotype ratios
Genetic Code	Triplet codons	Protein synthesis
Population Ecology	Growth models, structure	Human population trends