Cellular Respiration and Fermentation

Overview of Processes and Outputs

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

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

  • Occurs in the cytoplasm.

  • Net products: 2 ATP, 2 NADH, 2 pyruvate per glucose.

• Krebs Cycle (Citric Acid Cycle): Completes the oxidation of glucose derivatives, generating NADH and FADH2.

  • Occurs in the mitochondrial matrix.

  • Products per turn: 3 NADH, 1 FADH2, 1 ATP, 2 CO2.

• Oxidative Phosphorylation: Uses electron transport and chemiosmosis to produce ATP.

  • Electron carriers NADH and FADH2 donate electrons to the electron transport chain.

  • ATP synthase uses the proton gradient to synthesize ATP.

  • Equation:

• Fermentation: Occurs when oxygen is absent; regenerates NAD+ for glycolysis.

  • Types: Lactic acid fermentation, alcoholic fermentation.

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

Photosynthesis

Light 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; convert solar energy to chemical energy.

  • Photosystems I and II absorb light.

  • Electron transport chain produces ATP and NADPH.

  • Linear electron flow: electrons move from water to NADP+.

  • Cyclic electron flow: produces additional ATP.

• Dark Reactions (Calvin Cycle): Occur in the stroma; use ATP and NADPH to fix CO2 into glucose.

  • Equation:

• Types of Plants:

  • C3 plants: Use the Calvin cycle directly.

  • C4 plants: Minimize photorespiration by spatial separation of steps.

  • CAM plants: Minimize water loss by temporal separation of steps.

Example: Succulent plants use CAM metabolism to survive in arid environments.

Genetic Terms and Concepts

Basic Genetic Vocabulary

Genetics is the study of heredity and variation in organisms. Key terms describe the physical and genetic characteristics of organisms.

• 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 affect the phenotype (co-dominance) or blend (incomplete dominance).

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

Example: In pea plants, tall (T) is dominant over short (t).

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: Series of events leading to cell division; includes interphase (G1, S, G2) and mitosis.

• Centrosome: Organelle that organizes microtubules.

• Centromere: Region where sister chromatids are joined.

• Spindle Apparatus: Structure that separates chromosomes during mitosis.

• Phases of Mitosis:

  • Prophase: Chromosomes condense, spindle forms.

  • Metaphase: Chromosomes align at the cell equator.

  • Anaphase: Sister chromatids separate.

  • Telophase: Nuclear envelope reforms.

• Cytokinesis: Division of the cytoplasm.

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

Example: Skin cells divide by mitosis to replace lost cells.

Cancer Cells

Characteristics and Behavior

Cancer cells are characterized by uncontrolled growth and division due to genetic mutations.

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

• Loss of Growth Control: Cells continue to divide even when growth factors are absent.

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

• Loss of Anchorage Dependence: Cancer cells grow without attachment to a substrate.

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

Example: HeLa cells are immortal cancer cells used in research.

Principles of Inheritance

Mendelian Genetics and Laws

Inheritance principles explain how traits are passed from parents to offspring. Mendel's experiments laid the foundation for modern genetics.

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

• Law of Segregation: Each organism carries two alleles for each trait, which segregate during gamete formation.

• Testcross: Crossing an individual with a homozygous recessive to determine genotype.

• Laws of Probability: Used to predict genetic outcomes.

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

• Epistasis: One gene affects the expression of another.

• Environmental Impacts: Phenotype can be influenced by environment.

• Pedigree Analysis: Charting inheritance patterns in families.

• Multiple Alleles: More than two alleles for a gene (e.g., ABO blood group).

Example: Mendel's pea plant experiments demonstrated dominant and recessive inheritance.

Chromosomal Basis of Inheritance

Chromosome Structure and Disorders

Chromosomes carry genetic information and their behavior during meiosis explains inheritance patterns.

• Recombination Experiments: Show crossing over and genetic variation.

• Linked Genes: Genes located close together on the same chromosome.

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

• Chromosomal Basis of Sex Determination: XX (female), XY (male).

• X Inactivation: One X chromosome in females is inactivated (Barr body).

• Abnormal Chromosome Number: Disorders such as Down syndrome (trisomy 21).

• Genetic Disorders: Caused by abnormal chromosome number or structure.

Example: Hemophilia is a sex-linked disorder studied in the Royal Family.

Hemophilia Case Study: The Royal Disease

Genetic Basis and Inheritance

Hemophilia is a genetic disorder affecting blood clotting, often inherited as an X-linked recessive trait.

• Inheritance Pattern: More common in males due to single X chromosome.

• Historical Example: The Royal Family of Europe had several members affected by hemophilia.

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

Summary Table: Key Processes in Cellular Respiration and Photosynthesis