Free Response Practice: General Biology

Introduction

This study guide covers foundational topics in General Biology, focusing on molecular biology, genetics, evolution, biochemistry, and cell structure. Each section provides definitions, explanations, and examples to help students prepare for free response questions and figure-based problems.

Molecular Biology and Genetics

Nucleotides and DNA Structure

Nucleotides are the building blocks of nucleic acids such as DNA and RNA. Each nucleotide consists of three parts: a phosphate group, a five-carbon sugar (deoxyribose in DNA, ribose in RNA), and a nitrogenous base.

• Nucleotide: Monomer of nucleic acids; composed of a phosphate, sugar, and base.

• DNA Double Helix: Formed by complementary base pairing (A-T, G-C) and hydrogen bonds between nucleotides.

• Example: Adenine (A) pairs with Thymine (T); Guanine (G) pairs with Cytosine (C).

Inheritance and Gene Expression

DNA carries genetic information that is passed from parents to offspring. Traits are inherited through the transmission of genes, and gene expression determines how genetic information is used to produce proteins.

• Inheritance: The process by which genetic traits are passed from one generation to the next.

• Gene Expression: The process by which information from a gene is used to synthesize a functional gene product (usually a protein).

• Example: Mendelian inheritance patterns (dominant and recessive alleles).

Feedback Loops

Feedback loops regulate biological systems. Positive feedback amplifies changes, while negative feedback reduces changes to maintain homeostasis.

• Positive Feedback: Example: Blood clotting cascade.

• Negative Feedback: Example: Regulation of blood glucose by insulin.

Cell Biology and Organization

Properties of Life and Levels of Organization

Living organisms share seven properties: order, evolutionary adaptation, response to environment, regulation, energy processing, growth and development, and reproduction. Biological organization ranges from molecules to biosphere.

• Levels: Molecule → Organelle → Cell → Tissue → Organ → Organ System → Organism → Population → Community → Ecosystem → Biosphere

Domains and Cell Types

Life is classified into three domains: Bacteria, Archaea, and Eukarya. The two main cell types are prokaryotic and eukaryotic.

• Bacteria & Archaea: Prokaryotic cells (no nucleus).

• Eukarya: Eukaryotic cells (nucleus and organelles).

• Example: Escherichia coli (Bacteria), Homo sapiens (Eukarya).

Evolution and Natural Selection

Evolution by Natural Selection

Evolution explains how populations change over time through natural selection, where advantageous traits become more common.

• Natural Selection: Differential survival and reproduction of individuals due to differences in phenotype.

• Example: Rock pocket mouse color adaptation to environment.

Chemistry of Life

Electron Configurations and Chemical Bonds

Atoms have specific electron configurations that determine their chemical properties. Bonds can be covalent (sharing electrons) or ionic (transferring electrons).

• Covalent Bond: Electrons are shared between atoms.

• Ionic Bond: Electrons are transferred from one atom to another.

• Polar Covalent Bond: Unequal sharing of electrons.

• Nonpolar Covalent Bond: Equal sharing of electrons.

Water and Its Properties

Water is a polar molecule with unique properties due to hydrogen bonding.

• Cohesion: Water molecules stick together.

• Adhesion: Water molecules stick to other surfaces.

• Solvent Properties: Water dissolves many substances.

Intermolecular Forces

Chemical bonds and intermolecular forces determine molecular interactions.

• Hydrogen Bonds: Attraction between a hydrogen atom and an electronegative atom.

• Van der Waals Forces: Weak attractions between molecules.

Isotopes and Radioactivity

Isotopes are atoms of the same element with different numbers of neutrons. Radioactive decay is the process by which unstable isotopes lose energy.

• Isotope: Same number of protons, different number of neutrons.

• Radioactive Decay: Spontaneous breakdown of atomic nucleus.

• Carbon Dating: Uses decay to estimate age of organic materials.

Acids, Bases, and Buffers

pH and Buffers

pH measures the concentration of hydrogen ions in a solution. Buffers help maintain stable pH in biological systems.

• pH Formula:

• Buffer System: Maintains pH by neutralizing excess acids or bases.

• Example: Carbonic acid-bicarbonate buffer in blood.

Biomolecules and Biochemistry

Biomolecule Types and Functions

Four classes of biomolecules: carbohydrates, lipids, proteins, and nucleic acids. Each has specific monomers and functions.

Polymerization and Structure

Monomers join to form polymers through dehydration synthesis. Structure affects function, as seen in alpha and beta glucose polymers.

• Alpha Glucose: Forms starch (energy storage).

• Beta Glucose: Forms cellulose (structural support).

Protein Structure and Function

Proteins have four levels of structure: primary, secondary, tertiary, and quaternary. Bond types and intermolecular forces determine shape and function.

• Primary: Amino acid sequence.

• Secondary: Alpha helices and beta sheets (hydrogen bonds).

• Tertiary: 3D folding (disulfide bridges, hydrophobic interactions).

• Quaternary: Multiple polypeptide chains.

Enzymes and Chemical Reactions

Enzyme Function

Enzymes are biological catalysts that speed up chemical reactions by lowering activation energy.

• Active Site: Region where substrate binds.

• Catalysis: Enzymes facilitate conversion of reactants to products.

• Example: DNA polymerase adds nucleotides to DNA.

Figures and Visuals

Textbook Figures

Students should be able to draw and explain key figures from the textbook, including molecular structures, cell diagrams, and biochemical pathways. Refer to specific chapters and figures for practice.

• Chapter 1: Figures 1.13, 1.18, 1.20, 1.4, 1.7

• Chapter 2: Figure 2

• Chapter 3: Figures 3.2, 3.8, 3.12

• Chapter 4: Figures 4.7, 4.9

• Chapter 5: Figures 5.4, 5.6, 5.7, 5.9, 5.10, 5.11, 5.13, 5.14, 5.18

Additional info: Some explanations and examples have been expanded for academic completeness. Students should refer to their textbook for detailed diagrams and further reading.