Midterm II Study Guide: General Biology

Overview

This study guide outlines the major topics and subtopics covered in Lectures 7-13 for a General Biology college course. It is designed to help students prepare for a midterm exam by summarizing key concepts, definitions, and processes in cellular biology, genetics, and inheritance.

Cellular Respiration and Fermentation

Processes, Inputs, and Outputs

Cellular respiration is the process by which cells convert biochemical energy from nutrients into ATP, releasing waste products. Fermentation is an anaerobic process that allows cells to generate energy without oxygen.

• Glycolysis: The breakdown of glucose into pyruvate, producing ATP and NADH.

  • Occurs in the cytoplasm.

  • Inputs: Glucose, NAD+, ADP

  • Outputs: Pyruvate, NADH, ATP

• Krebs Cycle (Citric Acid Cycle/Tricarboxylic Acid Cycle):

  • Occurs in the mitochondrial matrix.

  • Inputs: Acetyl-CoA, NAD+, FAD, ADP

  • Outputs: CO2, NADH, FADH2, ATP

• Oxidative Phosphorylation:

  • Includes electron transport and chemiosmosis.

  • Electron carriers (NADH, FADH2) donate electrons to the electron transport chain.

  • ATP is produced via ATP synthase as protons flow down their gradient.

• Fermentation:

  • Occurs when oxygen is absent.

  • Regenerates NAD+ for glycolysis.

  • Produces lactic acid (in animals) or ethanol (in yeast).

Equation for Cellular Respiration:

Example: Muscle cells use lactic acid fermentation during intense exercise when oxygen is limited.

Photosynthesis

Light Reactions and Dark Reactions

Photosynthesis is the process by which plants, algae, and some bacteria convert light energy into chemical energy stored in glucose.

• Light Reactions:

  • Occur in the thylakoid membranes of chloroplasts.

  • Inputs: Light, H2O, NADP+, ADP

  • Outputs: O2, NADPH, ATP

  • Includes Photosystems I and II, electron transport chain, and cyclic/linear electron flow.

• Dark Reactions (Calvin Cycle):

  • Occur in the stroma of chloroplasts.

  • Inputs: CO2, NADPH, ATP

  • Outputs: Glucose, NADP+, ADP

Equation for Photosynthesis:

Example: Crassulacean Acid Metabolism (CAM) plants fix CO2 at night to minimize water loss.

Genetic Terms and Concepts

Basic Genetic Vocabulary

Genetics is the study of heredity and variation in organisms. Understanding key terms is essential for analyzing inheritance patterns.

• Genotype: The genetic makeup of an organism.

• Phenotype: The observable traits of an organism.

• Homologous Chromosomes: Chromosome pairs with the same genes but possibly different alleles.

• Allele: Alternative forms of a gene.

• Homozygous: Having two identical alleles for a gene.

• Heterozygous: Having two different alleles for a gene.

• Dominant/Recessive: Dominant alleles mask the effect of recessive alleles.

• Co-dominant/Incomplete Dominance: Both alleles are expressed, or the phenotype is intermediate.

• Monohybrid/Dihybrid Cross: Crosses involving one or two traits, respectively.

Example: In pea plants, the allele for purple flowers (P) is dominant over white (p).

Mitosis and Cell Division

Phases and Structures

Mitosis is the process by which a eukaryotic cell divides to produce two genetically identical daughter cells. It is essential for growth, repair, and asexual reproduction.

• Cell Cycle: Includes interphase (G1, S, G2) and mitotic phase (mitosis and cytokinesis).

• Centrosome: Organelle that organizes microtubules.

• Centromere: Region where sister chromatids are joined.

• Spindle Apparatus: Structure that separates chromosomes during mitosis.

• Phases of Mitosis:

  • Prophase

  • Metaphase

  • Anaphase

  • Telophase

• Cytokinesis: Division of the cytoplasm.

• Cell Cycle Checkpoints: G1, G2, M checkpoints ensure proper division.

Example: Skin cells undergo mitosis to replace damaged tissue.

Cancer Cells

Characteristics and Behavior

Cancer cells are characterized by uncontrolled growth and division, often due to mutations that disrupt normal cell cycle regulation.

• Transformation: Conversion of a normal cell to a cancer cell.

• Loss of Growth Control: Cells continue to divide even when signals tell them to stop.

• Loss of Density-Dependent Inhibition: Cancer cells pile up and do not stop dividing when crowded.

• Loss of Anchorage Dependence: Cancer cells can grow without being attached to a surface.

• Indefinite Division: Cancer cells can divide indefinitely (immortalized).

Example: Tumor formation results from uncontrolled cell division.

Meiosis and Sexual Reproduction

Phases and Genetic Variation

Meiosis is the process by which gametes (sperm and egg) are produced, reducing chromosome number by half and increasing genetic diversity.

• Phases of Meiosis: Meiosis I and II, each with prophase, metaphase, anaphase, telophase.

• Genetic Variation: Independent assortment, crossing over, and random fertilization contribute to genetic diversity.

• Animal, Plant, and Fungal Life Cycles: All involve meiosis and fertilization, but differ in timing and structure.

Example: Crossing over during prophase I increases genetic variation in offspring.

Principles of Inheritance

Mendelian Genetics and Beyond

Inheritance patterns are governed by laws discovered by Gregor Mendel and expanded by modern genetics.

• Mendel's Experiments: Demonstrated inheritance of traits in pea plants.

• Law of Independent Assortment: Genes for different traits assort independently during gamete formation.

• Law of Segregation: Each individual has two alleles for each gene, which segregate during meiosis.

• Testcross: Used to determine genotype by crossing with a homozygous recessive.

• Laws of Probability: Used to predict genetic outcomes.

• Dominance Spectrum: Complete, incomplete, and co-dominance.

• Multiple Alleles: More than two alleles exist for some genes (e.g., ABO blood group).

• Epistasis: One gene affects the expression of another.

• Environmental Impacts: Phenotype can be influenced by environment.

• Pedigree Analysis: Used to track inheritance in families.

• Recessively and Dominantly Inherited Diseases: Genetic disorders can be inherited in different patterns.

Example: Cystic fibrosis is a recessively inherited disease.

Chromosomal Basis of Inheritance

Chromosome Structure and Disorders

Genes are located on chromosomes, and inheritance patterns can be affected by chromosome behavior and abnormalities.

• Recombination Experiments: Demonstrate crossing over and gene mapping.

• Linked Genes: Genes located close together on the same chromosome tend to be inherited together.

• Sex-Linked Genes: Genes located on sex chromosomes (X, Y).

• Chromosomal Basis of Sex Determination: XX/XY system in humans.

• X Inactivation: In females, one X chromosome is randomly inactivated.

• Abnormal Chromosome Number and Structure: Can lead to genetic disorders (e.g., Down syndrome).

Example: Hemophilia is an X-linked recessive disorder.

Hemophilia Case Study: The Royal Disease

Application of Genetics

Hemophilia is a genetic disorder that impairs the blood's ability to clot. It is often used as a case study to illustrate X-linked inheritance.

• Inheritance Pattern: X-linked recessive; more common in males.

• Historical Example: The "Royal Disease" affected European royal families due to inheritance through female carriers.

Example: Queen Victoria was a carrier of hemophilia, passing the gene to her descendants.

Summary Table: Key Processes in Cellular Respiration and Photosynthesis