Biologists - Key Contributions & Achievements

GENERAL BIOLOGY 1 FIRST SEMESTER MIDTERM p 12STEM1 Biologists - Key Contributions & Achievements Filipino Biologists 🇵🇭 1. Eduardo Quisumbing o Renowned in the study of medicinal plants. o Known as the Father of Philippine Orchidology. 2. Carmen Velasquez o Identified various species and genera of parasitic organisms, particularly fish parasites. o Authored 45 basic research and 70 articles. Gregorio Velasquez o Pioneer of Philippine Phycology (study of algae). o Conducted significant research in the biochemistry and chemistry of natural products. 3. 4. William Padolina o Recognized for her research on propagation of mutant macapuno and tissue culture. o Developed an advanced technology for rapid propagation of macapuno. 5. Angel Alcala o 6. 7. 8. 9. Noted for his contribution to the conservation of coral reefs, mangroves, and wildlife sanctuaries. o Published studies on amphibians and reptiles. Benito Vergara o Pioneered research on rice cultivation and physiology of rice. Ramon Barba o Innovator of micropropagation techniques for dwarf highyielding rice varieties. o Achieved international recognition for rice development. Pedro Escuro o Specialized in retinal and corneal transplantation. o Awarded the Ten Outstanding Young Men (TOYM). Geronimo de Ocampo o Pioneer in modern Philippine ophthalmology and conducted the first corneal transplant in the country. GENERAL BIOLOGY 1 FIRST SEMESTER MIDTERM 10. 12STEM1 Quintin Kintanar o 11. 12. Conducted various original research in pharmacology and environmental science. o Burke Award for Excellence recipient. Filomena Campos o Made significant contributions to cotton production in the Philippines. Francisco Fronda o Recognized as the Father of Poultry Science in the Philippines. 13. Francisco Santos o His numerous studies are focused on the nutritive values and chemical compositions of Filipino foods. 14. Jose Vera Santos o Known for his research on the anatomical characteristics of bamboo and grasses. Foreign Biologists 1. Carolus Linnaeus o Swedish naturalist who developed the binomial system of classifying organisms. 2. Andreas Vesalius o Belgian anatomist, Father of Modern Anatomy. 3. Louis Pasteur o French biologist and chemist famous for his Germ Theory. o Developed pasteurization. 4. Anton van Leeuwenhoek o Dutch naturalist known for using a simple microscope to discover microorganisms. Rudolf Virchow o Father of Modern Pathology who first used the word "gene" to describe heredity. 5. 6. Gregor Mendel o 7. Father of Genetics who discovered the fundamental laws of inheritance. William Harvey o Discovered the mechanics of human blood circulation. GENERAL BIOLOGY 1 FIRST SEMESTER MIDTERM 8. Wilhelm Johannsen o 9. 10. 11. 12STEM1 Danish biologist who first used the term "gene" to describe chromosomes. Charles Darwin o British naturalist known as the Father of Evolution. Alexander Fleming o Discovered penicillin as an antibiotic. Robert Koch o Discovered bacteria that cause anthrax, tuberculosis, and cholera. 12. Joseph Lister o British surgeon highlighted the importance of antiseptic in surgery. 13. Edward Jenner o Worked on smallpox vaccines. 14. Albert Sabin o Discovered vaccines against the polio virus. Robert Hooke o Observed a piece of cork in a microscope; named the "cell". 15. 16. Francis Crick o With James Watson, described the double helix structure of DNA. GENERAL BIOLOGY 1 FIRST SEMESTER MIDTERM 12STEM1 Cell Biology 1. Cell Theory A. The Three Tenets of Cell Theory • All living organisms are composed of one or more cells. o Cells are the fundamental units of life, with all biological processes occurring within cells. • The cell is the basic unit of structure and organization in organisms. o Cells provide structure and carry out essential life functions. o In multicellular organisms, cells are organized into tissues, organs, and systems. • All cells arise from pre-existing cells. o Cells arise from the division of existing cells through processes like mitosis and meiosis. B. Extensions of Cell Theory (Modern) • Cells contain hereditary information (DNA) that is passed on during cell division. • Energy flow (metabolism and biochemistry) occurs within cells. o Sites of metabolic reactions such as respiration, photosynthesis, and synthesis of biomolecules. • All cells have the same basic chemical composition. o Composed of macromolecules (proteins, lipids, carbohydrates, nucleic acids) and ions. 2. Cell Scientists A. Key Contributors 1. Robert Hooke (1665) o Discovery: First observed and named "cells." o Contribution: Published "Micrographia," initiating cell biology. 2. Anton van Leeuwenhoek (1674) o Discovery: Observed living cells, including protozoa and bacteria ("animalcules"). o Contribution: Revealed existence of microorganisms. GENERAL BIOLOGY 1 FIRST SEMESTER MIDTERM 3. 4. 5. 12STEM1 Matthias Schleiden (1838) o Discovery: Proposed all plants are composed of cells. o Contribution: Co-founder of cell theory; emphasized cells as building blocks of plants. Theodor Schwann (1839) o Discovery: Stated all animals are composed of cells. o Contribution: Co-founder of cell theory; unified the concept for all living things. Rudolf Virchow (1855) o Discovery: Proposed all cells arise from pre-existing cells ("Omnis cellula e cellula"). o Contribution: Established the principle of biogenesis. B. Supporting Contributors 1. Jan Evangelista Purkyně (1839) o Contribution: Described "protoplasm" (cytoplasm). 2. Robert Brown (1831) o Discovery: Identified and named the cell nucleus. o Contribution: Emphasized nucleus' importance in cell function. 3. Cell Structure A. Major Cell Structures 1. Cell Membrane: The Gatekeeper o Structure: o ▪ Phospholipids: Amphipathic molecules form the bilayer. ▪ Proteins: Integral and peripheral proteins serve various functions. ▪ ▪ Cholesterol: Stabilizes membrane fluidity. Carbohydrates: Involved in cell recognition and signaling. Function: ▪ ▪ ▪ Regulates movement of substances. Facilitates cell communication. Maintains structural integrity. GENERAL BIOLOGY 1 FIRST SEMESTER MIDTERM 2. Nucleus: The Control Center o Structure: o ▪ Double membrane nuclear envelope with nuclear pores. ▪ ▪ Nucleolus: Ribosome production. o Regulates gene expression. Site of DNA replication and transcription. Double-membraned with cristae inner folds. Matrix: Contains mitochondrial DNA, ribosomes, enzymes. Function: ▪ ▪ Site of cellular respiration (glucose to ATP). Involved in energy production, apoptosis, calcium storage. Ribosomes: The Protein Factories o Structure: o ▪ Composed of rRNA and proteins; free in cytoplasm or attached to rough ER. ▪ Size: Measured in Svedberg units (S), size and density. Function: ▪ 5. Houses genetic material (DNA). Mitochondria: The Powerhouses o Structure: ▪ ▪ 4. Chromatin: DNA wrapped around histone proteins. Function: ▪ ▪ ▪ 3. 12STEM1 Translate mRNA into polypeptides (proteins). Endoplasmic Reticulum (ER): The Production and Transport Network o Structure: ▪ ▪ o Rough ER: Covered with ribosomes. Smooth ER: Lacks ribosomes. Function: ▪ Rough ER: Synthesizes and processes proteins. GENERAL BIOLOGY 1 FIRST SEMESTER MIDTERM 12STEM1 ▪ 6. Smooth ER: Synthesizes lipids, detoxifies, stores calcium. Golgi Apparatus: The Packaging and Distribution Center o Structure: ▪ o ▪ 7. ▪ Membrane-bound, contains hydrolytic enzymes. Function: ▪ Digest/recycle cellular waste, damaged organelles, foreign materials. ▪ Involved in apoptosis. Cytoskeleton: The Structural Framework o Structure: ▪ o Composed of microfilaments, intermediate filaments, microtubules. Function: ▪ 9. Modifies, sorts, packages proteins and lipids for distribution. Lysosomes: The Digestive Compartments o Structure: o 8. Flattened sacs (cisternae). Function: Provides support, maintains shape, facilitates movement, transport, division. Vacuoles: The Storage Units o Structure: ▪ o Membrane-bound sacs (larger in plant cells). Function: ▪ ▪ Store nutrients, waste products. Maintain turgor pressure in plants. 10. Chloroplasts (Plant Cells Only): The Photosynthesis Machinery o Structure: ▪ ▪ ▪ Double-membraned, containing chlorophyll. Thylakoids: Site of light-dependent reactions. Stroma: Site of the Calvin cycle. GENERAL BIOLOGY 1 FIRST SEMESTER MIDTERM o 12STEM1 Function: ▪ ▪ Convert light energy into glucose. ▪ Composed of cellulose. Produce oxygen as a byproduct. 11. Cell Wall (Plant Cells Only): The Protective Barrier o Structure: o Function: ▪ ▪ Provides rigidity and strength. Prevents excessive water uptake. 12. Centrioles (Animal Cells Only): The Organizers of Cell Division o Structure: ▪ o Cylindrical structures near the nucleus. Function: ▪ Organize microtubules during cell division (mitotic spindle). B. Minor Cell Structures 1. Peroxisomes: The Detoxifiers o Structure: ▪ o Function: ▪ 2. Membrane-bound, contain enzymes like catalase, oxidase. Break down fatty acids, amino acids, toxins (e.g., hydrogen peroxide). Cilia and Flagella: The Movement Specialists o Structure: o ▪ Hair-like with microtubules, plasma membranecovered. ▪ ▪ Cilia: Short, numerous. Flagella: Longer, fewer. Function: ▪ ▪ Cilia: Move fluids over cell surface. Flagella: Propel cells. GENERAL BIOLOGY 1 FIRST SEMESTER MIDTERM 3. Nucleoid Region (Bacterial Cells Only): The DNA Hub o Structure: ▪ o Region in cytoplasm (non-membrane bound) with bacterial chromosome. Function: ▪ 4. 12STEM1 Contains genetic material, directs cellular activities. Plasmids (Bacterial Cells Only): The Extra DNA o Structure: ▪ o Small, circular DNA molecules. Function: ▪ Typically carry advantageous genes (e.g., antibiotic resistance). C. Macromolecules and Their Roles in Cells 1. Proteins: The Workhorses of the Cell o Structure: ▪ o 2. Composed of amino acids, forming polypeptides with specific 3D structures. Function: ▪ ▪ ▪ Enzymes: Catalyze reactions. ▪ Signal proteins: Involved in cell communication. Structural proteins: Provide support. Transport proteins: Move substances across membranes. Carbohydrates: The Energy Source o Structure: ▪ o Composed of carbon, hydrogen, oxygen in forms of sugars and polysaccharides. Function: ▪ ▪ Energy storage. ▪ Cell recognition and signaling. Structural components: ▪ Cell walls (e.g., cellulose in plants). GENERAL BIOLOGY 1 FIRST SEMESTER MIDTERM 3. Lipids: The Energy Reserves o Structure: ▪ o Glycerol and fatty acids form triglycerides, phospholipids, sterols. Function: ▪ ▪ ▪ 4. 12STEM1 Energy storage. Structural components of membranes. Signaling molecules (e.g., hormones). Nucleic Acids: The Information Molecules o Structure: ▪ o Composed of nucleotides forming DNA and RNA. Function: ▪ ▪ DNA: Stores genetic information. RNA: Transfers genetic info for protein synthesis. 4. Cell Functions A. Metabolism: The Sum of All Chemical Reactions • Anabolism: Synthesis of complex molecules (energyrequiring). • Catabolism: Breakdown of complex molecules (energyreleasing). B. Cellular Respiration: The Energy Conversion Process • Glycolysis: Converts glucose into pyruvate, producing ATP and NADH. • Krebs Cycle: Produces ATP, NADH, FADH2 in mitochondrial matrix. • Electron Transport Chain: Generates ATP through oxidative phosphorylation. C. Photosynthesis (Plant Cells Only): The Light Energy Conversion • Light-Dependent Reactions: Convert sunlight to ATP and NADPH. • Calvin Cycle: Fixes carbon dioxide into glucose using ATP and NADPH. GENERAL BIOLOGY 1 FIRST SEMESTER MIDTERM 12STEM1 D. Protein Synthesis: The Central Dogma of Molecular Biology • • Transcription: DNA sequence copied into mRNA. Translation: Ribosomes synthesize proteins from mRNA. E. Cell Division: The Process of Reproduction • • Mitosis: Produces two genetically identical daughter cells. Meiosis: Produces four genetically unique gametes with half the chromosomes. F. Cell Signaling: The Communication System • Signal Transduction: Cell responses to external signals. G. Transport Mechanisms: The Movement of Substances • Passive Transport: Diffusion, osmosis, facilitated diffusion (no energy). • • Active Transport: Movement against gradient, requiring ATP. Endocytosis and Exocytosis: Intake/export of large molecules via vesicles. GENERAL BIOLOGY 1 12STEM1 FIRST SEMESTER MIDTERM Comparison of Plant, Animal, and Bacterial Cells Organelle/Feature Plant Cells Animal Cells Bacterial Cells Cell Wall Present (cellulose) Absent Present (peptidoglycan) Plasma Membrane Present Present Present Nucleus Present (linear DNA) Present (linear DNA) Absent (nucleoid region) Nucleolus Present Present Absent Ribosomes Present (80S) Present (80S) Present (70S) ER Present (Rough/Smooth) Present (Rough/Smooth) Absent Golgi Apparatus Present Present Absent Mitochondria Present Present Absent Chloroplasts Present Absent Absent Vacuole Large central Small or absent Absent Lysosomes Absent Present Absent Peroxisomes Present Present Absent Vesicles Present (for transport) Present (for transport and secretion) Absent (may have inclusion bodies) Cytoskeleton Present Present Present (simpler) Centrioles Absent Present Absent Cilia/Flagella Rare Present Present Plasmodesmata Present Absent Absent Pili/Fimbriae Absent Absent Present Plasmids Absent Absent Present DNA Structure Linear Linear Circular Reproduction Mitosis/Meiosis Mitosis/Meiosis Binary fission Size Larger (10-100 μm) Larger (10-100 μm) Smaller (1-10 μm) Glycocalyx Absent Absent Present Mesosomes Absent Absent Present GENERAL BIOLOGY 1 FIRST SEMESTER MIDTERM Cell Diagrams 1. Plant Cell 2. Animal Cell 12STEM1 GENERAL BIOLOGY 1 FIRST SEMESTER MIDTERM 3. Bacteria Cell 12STEM1 GENERAL BIOLOGY 1 FIRST SEMESTER MIDTERM 12STEM1 HOMEWORK #2 September 04, 2024 Plant Tissues 1. Meristematic Tissues • • Definition: Actively dividing cells responsible for plant growth. Types: o Apical Meristem ▪ ▪ o Function: Contributes to the elongation of plant organs (length growth). ▪ Example: Growing tip of a plant's shoot. Lateral Meristem (Cambium) ▪ ▪ o Location: Tips of roots and shoots. Location: Along the sides of stems and roots. Function: Responsible for the thickening (girth growth) of plant organs. ▪ Example: Vascular cambium in tree trunks. Intercalary Meristem ▪ ▪ Location: Base of leaves or internodes (in grasses). ▪ Example: Grass blades regrowing after being cut. Function: Helps in the regrowth of grasses and elongation of internodes. 2. Permanent Tissues a. Simple Permanent Tissues • Parenchyma o Function: Storage, photosynthesis, and secretion. o Cell Structure: Thin cell walls, large central vacuole. o Example: Mesophyll in leaves, storage tissues in fruits like apples. • Collenchyma o Function: Provides support and flexibility to young plant parts. o Cell Structure: Thickened cell walls at corners. o Example: Stems of young plants, celery stalks. GENERAL BIOLOGY 1 FIRST SEMESTER MIDTERM • 12STEM1 Sclerenchyma o Function: Provides mechanical strength and support. o Cell Structure: Thick, lignified cell walls; cells are dead at maturity. o Example: Hard outer shells of nuts, fibers in jute and flax. b. Complex Permanent Tissues • Xylem o o o • Function: Transports water and minerals from roots to other parts; provides structural support. Components: ▪ Tracheids and Vessels: Conduct water and minerals. ▪ ▪ Xylem Fibers: Provide mechanical support. Xylem Parenchyma: Stores nutrients, assists in water transport. Example: Wood in trees, vascular bundles in stems. Phloem o o Function: Transports nutrients (sugars) produced during photosynthesis. Components: ▪ ▪ ▪ ▪ o Sieve Tubes: Conduct food. Companion Cells: Support sieve tubes. Phloem Fibers: Provide support. Phloem Parenchyma: Stores food and other substances. Example: Bark of trees, vascular bundles in leaves. GENERAL BIOLOGY 1 FIRST SEMESTER MIDTERM 12STEM1 Animal Tissues 1. Epithelial Tissue • Function: Covers body surfaces, lines internal cavities, and forms glands; provides protection, absorption, secretion, and filtration. • Types: o Simple Squamous Epithelium ▪ ▪ ▪ o o o o o Function: Allows diffusion and filtration. Example: Alveoli in lungs, lining of blood vessels. Simple Cuboidal Epithelium ▪ ▪ ▪ o Structure: Single layer of flat cells. Structure: Single layer of cube-shaped cells. Function: Secretion and absorption. Example: Kidney tubules, ducts of glands. Simple Columnar Epithelium ▪ ▪ Structure: Single layer of tall, column-like cells. ▪ Example: Lining of the stomach and intestines. Function: Absorption and secretion; may have microvilli. Stratified Squamous Epithelium ▪ ▪ ▪ Structure: Multiple layers; surface cells are flat. ▪ ▪ ▪ Structure: Usually two layers of cube-shaped cells. ▪ Structure: Several layers; surface cells are columnar. ▪ ▪ Function: Protection and secretion. Function: Protection against abrasion. Example: Skin, lining of the esophagus. Stratified Cuboidal Epithelium Function: Protection. Example: Sweat glands, mammary glands. Stratified Columnar Epithelium Example: Male urethra, some gland ducts. Pseudostratified Columnar Epithelium ▪ Structure: Appears stratified but is a single layer with varying cell heights. ▪ Function: Secretion, especially of mucus; movement of mucus via cilia. GENERAL BIOLOGY 1 FIRST SEMESTER MIDTERM ▪ o 12STEM1 Example: Lining of the trachea, upper respiratory tract. Transitional Epithelium ▪ Structure: Resembles both stratified squamous and stratified cuboidal; can stretch. ▪ Function: Stretches readily to accommodate volume changes. ▪ Example: Lining of the urinary bladder. 2. Connective Tissue • Function: Supports, binds, and protects organs; stores energy, and transports materials. • Types: o Loose Connective Tissue ▪ Areolar Tissue ▪ ▪ ▪ Function: Stores fat; insulates the body. Example: Under the skin, around organs. Reticular Tissue ▪ ▪ o Example: Beneath the skin, around blood vessels. Adipose Tissue ▪ ▪ ▪ Function: Binds skin to underlying tissues Function: Supports soft organs. Example: Spleen, lymph nodes. Dense Connective Tissue ▪ Dense Regular: Strong, resists pulling forces. ▪ Example: Tendons (connect muscle to bone), ligaments (connect bone to bone). ▪ Dense Irregular: Withstands tension from multiple directions. ▪ Elastic: Allows tissue to stretch and return to shape. ▪ ▪ Example: Dermis of the skin. Example: Walls of large arteries, bronchial tubes. GENERAL BIOLOGY 1 FIRST SEMESTER MIDTERM 12STEM1 3. Muscle Tissue • • Function: Responsible for movement through contraction. Types: o o o Skeletal Muscle ▪ Structure: Long, cylindrical fibers; striated; voluntary control. ▪ ▪ Function: Moves bones and generates heat. Example: Muscles attached to bones, such as biceps, triceps. Cardiac Muscle ▪ Structure: Branched fibers striated; involuntary control; intercalated discs. ▪ ▪ Function: Pumps blood throughout the body. Example: Walls of the heart. Smooth Muscle ▪ Structure: Spindle-shaped cells, non-striated; involuntary control. ▪ Function: Moves substances through hollow organs. ▪ Example: Walls of blood vessels, digestive tract, bladder. 4. Nervous Tissue • Function: Transmits electrical signals throughout the body; controls and coordinates body functions. • Components: o o Neurons ▪ Structure: Specialized cells with a cell body, dendrites, and an axon. ▪ Function: Conduct electrical impulses to transmit information. ▪ Example: Sensory neurons, motor neurons. Neuroglia (Glial Cells) ▪ ▪ Function: Support, protect, and nourish neurons. Example: Astrocytes, oligodendrocytes, Schwann cells. GENERAL BIOLOGY 1 FIRST SEMESTER MIDTERM q 12STEM1 GENERAL BIOLOGY 1 FIRST SEMESTER MIDTERM Animal Tissue 12STEM1 GENERAL BIOLOGY 1 FIRST SEMESTER MIDTERM 12STEM1 GENERAL BIOLOGY 1 FIRST SEMESTER MIDTERM HOMEWORK #3 12STEM1 September 11, 2024 Characterization of the Cell Cycle Phases and Their Control Points Phases of the Cell Cycle Interphase • • Comprised of three sub-phases (G1, S, G2) Grows and prepares for cell division M phase • • Includes mitosis (nuclear division) Cytokinesis (cytoplasmic division) G1 Phase (First Gap Phase) • Duration: Varies from several hours to years depending on cell type and conditions • Cellular Events: o Increases in size o Synthesizes mRNA and proteins o Organelle duplicatP Uion o Monitors internal environment (energy, nutrients, signals) • Regulation and Control Point: o G1/S Checkpoint (Restriction Point): ▪ Decides whether to enter DNA synthesis and cell division ▪ Key regulators: Cyclin D and Cyclin E bind to CDKs (CDK4/6, CDK2) ▪ Rb protein phosphorylation, releasing E2F to activate DNA synthesis genes ▪ Failure consequences: Enter quiescent state (G0) or trigger apoptosis GENERAL BIOLOGY 1 FIRST SEMESTER MIDTERM 12STEM1 S Phase (Synthesis Phase) • Duration: Typically, 6 to 8 hours • Cellular Events: o DNA duplication results in sister chromatids held by o o • centromere Helicases and DNA polymerases facilitate DNA replication Histone production Quality Control: o No formal checkpoint o Proofreading and Mismatch repair ensure fidelity G2 Phase (Second Gap Phase) • Duration: Typically, 3 to 4 hours • Cellular Events: o Final preparation for mitosis o Synthesis of mitosis necessary proteins o Microtubule assembly for mitotic spindle o DNA integrity check • Regulation and Control Point: o G2/M Checkpoint: Ensures DNA replication completeness o Key regulators: Cyclin A, Cyclin B, and CDK1 o DNA damage response (DDR) with ATM and ATR activation The M Phase (Mitotic Phase) Mitosis • Prophase: Chromosomes condense, nuclear membrane disintegrates, centrosomes migrate • Prometaphase: Nuclear envelope breaks down, spindle fibers attach to kinetochores • • • Metaphase: Chromosomes align at the metaphase plate Anaphase: Sister chromatids are pulled apart to opposite poles Telophase: Chromosomes decondense, nuclear envelope reform GENERAL BIOLOGY 1 FIRST SEMESTER MIDTERM Cytokinesis • • • 12STEM1 Division of cytoplasm Animal cells: Formation of a cleavage furrow Plant cells: Formation of a cell plate Control Points in the Cell Cycle • G1/S Checkpoint (Restriction Point): Checks DNA integrity, nutrients, growth signals • G2/M Checkpoint: Confirms DNA replication completion and lack of damage • Spindle Assembly Checkpoint: Ensures chromosomes are correctly attached to spindle apparatus before anaphase Stages of Mitosis and Meiosis Stages of Mitosis Prophase • • • Chromosome Condensation • • Nuclear Envelope Disassembly Nuclear Envelope Breakdown Formation of the Mitotic Spindle Prometaphase Attachment of Spindle Fibers Metaphase • Chromosome Alignment at metaphase plate Anaphase • Separation of Sister Chromatids Telophase • • Chromosome Decondensation • • Animal cells: Cleavage furrow Reformation of the Nuclear Envelope Cytokinesis Plant cells: Cell plate formation GENERAL BIOLOGY 1 FIRST SEMESTER MIDTERM 12STEM1 Stages of Meiosis Meiosis I: The Reductional Division Prophase I • • Chromosome Condensation Synapsis and Crossing Over: Formation of tetrads and exchange of DNA Metaphase I • Homologous Chromosome Alignment at metaphase plate Anaphase I • Separation of Homologous Chromosomes Telophase I • Formation of Two Daughter Cells Meiosis II: The Equational Division Prophase II • • Chromosome Condensation Spindle Formation Metaphase II • Chromosome Alignment at metaphase plate Anaphase II • Separation of Sister Chromatids Telophase II • Formation of Four Haploid Daughter Cells Significance of Mitosis and Meiosis Significance of Mitosis • • • Growth Tissue Repair and Regeneration Asexual Reproduction Significance of Meiosis • • • Sexual Reproduction Genetic Diversity: Crossing over and Independent assortment Maintenance of Chromosome Number GENERAL BIOLOGY 1 FIRST SEMESTER MIDTERM 12STEM1 Key Differences Between Mitosis and Meiosis Characteristic Mitosis Meiosis Primary Function Growth, tissue repair, asexual reproduction Sexual reproduction Rounds of Division One Two Genetic Composition of Daughter Cells Identical to parent Genetically diverse Chromosome Number Diploid (2n) Haploid (n) Homologous Chromosomes Pairing No pairing, no crossing over Pairing, crossing over occurs Type of Cells Produced Somatic cells Gametes GENERAL BIOLOGY 1 FIRST SEMESTER MIDTERM CELL CYCLE References: [1] https://www.genome.gov/genetics-glossary/Cell-Cycle [2] https://www.britannica.com/science/cell-cycle [3] https://byjus.com/biology/cell-cycle-and-division/ [4] https://www.britannica.com/science/mitosis [5] https://www.yourgenome.org/theme/what-is-meiosis/ [6] https://sciencenotes.org/mitosis-vs-meiosis/ [7] https://www.sciencefacts.net/cell-cycle.html 12STEM1 GENERAL BIOLOGY 1 FIRST SEMESTER MIDTERM 12STEM1 Cell Division: Mitosis CELL DIVISION • The process by which a single cell generates new daughter cells. CELL CYCLE • The sequence of events by which a cell duplicates its genome, synthesizes other cell constituents, and eventually divides into two daughter cells. • Continuous Process: The cell cycle does not have a distinct beginning or end. Phases of Cell Cycle (Example for a 24-hour cycle) 1. 2. 3. 4. G1 (First Gap): 11 hours S (Synthesis of DNA): 8 hours G2 (Second Gap): 4 hours Mitotic Phase (Mitosis & Cytokinesis): 1 hour INTERPHASE • The stage of the cell cycle where the cell engages in normal metabolic activities and prepares for the next cell division. o Contains three distinct phases: G1, S, and G2. o During interphase, chromosomes are de-condensed and present in the nucleus. Interphase Sub-Stages 1. 2. G1 Stage: o The cell is metabolically active and continuously grows but does not replicate its DNA. o Environmental conditions and signaling molecules may influence the cell to progress through the rest of the cell cycle. S Stage: o DNA synthesis (replication) takes place. o The result is a pair of sister chromatids for each chromosome. GENERAL BIOLOGY 1 FIRST SEMESTER MIDTERM ▪ 3. 12STEM1 Example: A human cell in G1 has 46 chromosomes. In G2, it has 46 pairs of sister chromatids (92 chromatids). G2 Stage: o The cell synthesizes proteins necessary for chromosome sorting and cell division. o Some cell growth may occur in preparation for mitosis. MITOTIC PHASE (M Phase) • Includes both mitosis and cytokinesis; it is typically the shortest part of the cell cycle. o Mitosis: Involves somatic cells and primarily functions for cell growth and repair. o Cytokinesis: Division of the cell's cytoplasm into two new cells. Steps of Mitosis 1. Prophase o Chromosomes condense. o Spindle fibers form. o Nuclear membrane disassembles. o Nucleolus disappears. o Replicated chromosomes, joined as sister chromatids, condense. 2. Metaphase o Longest stage in mitosis. o The nuclear membrane disassembled; chromosomes align along the metaphase plate. o Chromatids remain attached at the centromere. 3. Anaphase o Shortest stage in mitosis. o Sister chromatids separate and move to opposite poles. o Poles of the cell move further apart, leading to separated daughter chromosomes. GENERAL BIOLOGY 1 FIRST SEMESTER MIDTERM 12STEM1 4. Telophase o Spindle fibers disassemble. o Nuclear membrane re-forms. o Chromosomes uncoil. o Nucleolus re-forms. 5. Cytokinesis o Separation of the two nuclei into individual daughter cells. o Animal Cells: Formation of a cleavage furrow which splits the cell. o Plant Cells: Formation of a cell plate that eventually forms a new cell wall. SIGNIFICANCE OF MITOSIS • Diploid Cells: Results in diploid cells with identical genetic composition. • • Cell Growth: Supports growth of multicellular organisms. • Meristematic Tissues: Enables continuous growth in plants. Cell Repair: Continuous replacement of cells like epidermis, gut lining, and blood cells. Comparison of Mitosis and Meiosis: • Mitosis: One cycle of PMAT, results in 2 identical diploid cells. • Meiosis: Two cycles of PMAT, results in 4 non-identical haploid cells. Summary • Mitosis results in two identical daughter cells, each with a diploid set of chromosomes (46 chromosomes in humans). • Essential for growth, repair, and continuous cellular activities in multicellular organisms. GENERAL BIOLOGY 1 FIRST SEMESTER MIDTERM HOMEWORK #4 12STEM1 September 17, 2024 Cell Transport Mechanisms Cells need to move molecules, ions, and nutrients in and out to maintain homeostasis, grow, and respond to their environment. There are two main types of transport mechanisms: 1. Passive Transport (no energy required) 2. Active Transport (requires energy—usually in the form of ATP) These transport mechanisms ensure that cells acquire essential molecules like oxygen and nutrients while removing waste products. 1. Passive Transport • No energy is required. • Molecules move down their concentration gradient (from high to low concentration). Types of Passive Transport: o Simple Diffusion: Movement of small, nonpolar molecules (like oxygen or carbon dioxide) directly through the cell membrane. o Facilitated Diffusion: Utilizes carrier proteins or channels to transport larger or polar molecules (e.g., glucose, ions) across the membrane. o Osmosis: Movement of water molecules through a semipermeable membrane, influenced by solute concentration. GENERAL BIOLOGY 1 12STEM1 FIRST SEMESTER MIDTERM Passive Transport Energy Required? Direction of Movement Examples Simple Diffusion No High to low concentration O₂, CO₂ Facilitated Diffusion No High to low concentration Glucose, Na⁺, K⁺ Osmosis No High to low concentration Water across the cell membrane 2. Active Transport • Requires energy (usually in the form of ATP). • Molecules are moved against their concentration gradient (from low to high concentration). Types of Active Transport: o Primary Active Transport: Direct use of ATP to pump molecules across the membrane (e.g., Sodium-Potassium Pump). o Secondary Active Transport (Cotransport): Utilizes the energy from the gradient created by primary active transport. Active Transport Energy Required? Direction of Movement Examples Primary Active Yes (ATP) Low to high concentration Na⁺/K⁺ pump Secondary Active Yes (indirectly ATP) Uses gradient for movement Glucose uptake in intestines GENERAL BIOLOGY 1 FIRST SEMESTER MIDTERM 12STEM1 Endocytosis and Exocytosis: Bulk Transport These are specialized forms of active transport used by cells to move large particles (like proteins, lipids, and large molecules) into or out of the cell. Unlike simple transport, they involve the use of vesicles. Exocytosis: "Exporting Molecules" • Definition: Exocytosis is a form of bulk transport where materials are exported out of the cell via vesicles. • Process: 1. Vesicle Formation: Materials to be exported are packaged into vesicles. 2. Transport: Vesicles are transported to the plasma membrane. 3. Fusion: The vesicle membrane fuses with the cell membrane. 4. Release: The contents (like proteins or waste) are released into the extracellular space. • Examples: o Release of neurotransmitters from neurons. o Secretion of hormones like insulin from pancreatic cells. o Transport of antibodies during an immune response. Exocytosis Direction Examples Energy Required? Moves materials out Cell → External space Neurotransmitter release, hormone secretion Yes (ATP) Endocytosis: "Importing Molecules" • Definition: Endocytosis is the process of importing large molecules into the cell via vesicle formation. • Process: 1. Engulfing: The plasma membrane folds inward around the material. 2. Vesicle Formation: The membrane pinches off, enclosing the material in a vesicle. GENERAL BIOLOGY 1 12STEM1 FIRST SEMESTER MIDTERM 3. • Transport: The vesicle moves into the cytoplasm for further processing. Types of Endocytosis: 1. Phagocytosis ("Cell Eating"): Engulfment of large particles like bacteria or dead cells. 2. ▪ Example: White blood cells engulfing pathogens. Pinocytosis ("Cell Drinking"): Engulfment of liquids or dissolved substances. ▪ 3. Example: Absorption of nutrients in the small intestine. Receptor-Mediated Endocytosis: Targeted uptake of specific molecules that bind to receptors on the cell surface. ▪ Example: Cholesterol uptake via LDL receptors. Endocytosis Type Material Transported Energy Required? Phagocytosis (Cell Eating) Large particles, pathogens Yes (ATP) Pinocytosis (Cell Drinking) Liquids, small molecules Yes (ATP) Receptor-Mediated Endocytosis Specific molecules like LDL Yes (ATP) Differences Between Exocytosis and Endocytosis Characteristic Direction of Transport Exocytosis Out of the cell Endocytosis Into the cell Involves Vesicles? Yes Yes Energy Requirement Yes (Active Transport) Yes (Active Transport) Function Secreting hormones, enzymes, waste Engulfing particles, bacteria, fluids Examples Release of neurotransmitters Phagocytosis, pinocytosis GENERAL BIOLOGY 1 FIRST SEMESTER MIDTERM 12STEM1 Why Are These Processes Important? • Cell Communication: Exocytosis allows for the release of signaling molecules like neurotransmitters. • Nutrient Absorption: Endocytosis enables cells to take in essential nutrients and molecules. • Immune Response: Phagocytosis (a form of endocytosis) allows immune cells to destroy pathogens. • Waste Removal: Exocytosis helps in eliminating cellular waste products. References: [1] https://byjus.com/biology/transport-across-cell-membrane/ [2] https://www.vedantu.com/biology/cell-transport-and-its-types [3] https://www.youtube.com/watch?v=ufCiGz75DAk [4] https://byjus.com/biology/difference-between-exocytosis-and-endocytosis/ GENERAL BIOLOGY 1 FIRST SEMESTER MIDTERM HOMEWORK #1 12STEM1 October 02, 2024 1. Enzymes: Structure, Function, and Types Definition: • Enzymes are biological catalysts that speed up chemical reactions in living organisms. They are proteins that lower the activation energy required for reactions, enabling life-sustaining processes to occur efficiently. Key Properties of Enzymes: 1. 2. 3. 4. 5. Catalytic Power: o Enzymes increase the rate of reactions without being consumed in the process. o They work by lowering the activation energy (the energy barrier that must be overcome for a reaction to proceed). Specificity: o Enzymes are highly specific to their substrates (the molecules they act upon). o This specificity is due to the unique active site of each enzyme, which fits only particular substrates. Active Site: o The region of the enzyme where the substrate binds is called the active site. o The shape and chemical environment within the active site are critical for the enzyme’s function. Lock and Key Model vs. Induced Fit Model: o Lock and Key Model: The enzyme’s active site is precisely shaped to fit the substrate, like a key fits a lock. o Induced Fit Model: The enzyme’s active site changes shape slightly to better fit the substrate as it binds. Cofactors and Coenzymes: o Some enzymes require cofactors (inorganic ions like Zn²⁺, Mg²⁺) or coenzymes (organic molecules like vitamins) for proper function. GENERAL BIOLOGY 1 FIRST SEMESTER MIDTERM 6. 12STEM1 Temperature and pH Sensitivity: o Enzymes work best at an optimal temperature and pH. o Extreme temperatures or pH levels can denature (damage) the enzyme, making it inactive. Enzyme Function in Metabolism: • Anabolic Reactions: Enzymes help in building larger molecules from smaller units (e.g., protein synthesis). • Catabolic Reactions: Enzymes break down complex molecules into simpler ones (e.g., digestion of food). Types of Enzymes Based on Reaction Type: Type of Enzyme Function Example Oxidoreductases Catalyze oxidation-reduction reactions Catalase Transferases Transfer functional groups between molecules Kinases Hydrolases Catalyze the breakdown of molecules by adding water Amylase Lyases Break bonds without water Decarboxylases Isomerases Catalyze the rearrangement of atoms within a molecule Phosphoglucoisomerase Ligases Join two molecules together DNA ligase Enzyme Inhibition: 1. 2. 3. Competitive Inhibition: o A substance competes with the substrate for the enzyme’s active site. o This prevents the enzyme from binding to its substrate. Non-Competitive Inhibition: o An inhibitor binds to a site other than the active site, altering the enzyme’s shape and reducing its activity. Allosteric Regulation: o Some enzymes have an allosteric site where molecules can bind to enhance or inhibit the enzyme's activity. GENERAL BIOLOGY 1 FIRST SEMESTER MIDTERM 12STEM1 2. Reduction-Oxidation (REDOX) Reactions: Definition: • Reduction-Oxidation (REDOX) reactions involve the transfer of electrons between two chemical species. One species loses electrons (oxidation), and the other gains electrons (reduction). Key Concepts: 1. 2. 3. 4. Oxidation: o Loss of electrons from a substance. o The substance that loses electrons is said to be oxidized. Reduction: o Gain of electrons by a substance. o The substance that gains electrons is said to be reduced. Oxidizing Agent (Oxidant): o The substance that accepts electrons (gets reduced) in a REDOX reaction. o Example: In the reaction 2H2+O2 → 2H2O, oxygen acts as the oxidizing agent because it gains electrons from hydrogen. Reducing Agent (Reductant): o The substance that donates electrons (gets oxidized) in a REDOX reaction. o Example: In the same reaction, hydrogen is the reducing agent because it loses electrons to oxygen. Rules for Identifying Oxidation and Reduction: • Oxidation State (also known as oxidation number) helps in identifying what gets oxidized and reduced: o Elements in their elemental form have an oxidation state of 0. o Oxygen generally has an oxidation state of -2, except in peroxides or compounds with fluorine. o Hydrogen generally has an oxidation state of +1 when bonded to non-metals and -1 when bonded to metals. GENERAL BIOLOGY 1 FIRST SEMESTER MIDTERM Species 12STEM1 Oxidation Change Process Oxygen (O₂) 0 → -2 Reduction Hydrogen (H₂) 0 → +1 Oxidation Examples of REDOX Reactions: 1. 2. 3. Combustion Reactions: o Involves oxygen reacting with hydrocarbons (e.g., in fuel) to produce carbon dioxide and water, releasing energy. o Example: CH4 + 2O2 → CO2 + 2H2O Cellular Respiration: o Biological REDOX process where glucose is oxidized to carbon dioxide and oxygen is reduced to water, generating ATP energy. o Example: C6H12O6 + 6O2 → 6CO2 + 6H2O Photosynthesis: o Opposite of respiration: Carbon dioxide is reduced to glucose, and water is oxidized to oxygen. o Example: 6CO2 + 6H2O + light → C6H12O6 + 6O2 Balancing REDOX Reactions: 1. 2. 3. 4. Assign Oxidation States: o Identify which atoms are oxidized and which are reduced. Separate Half-Reactions: o Write out the oxidation and reduction half-reactions. Balance Each Half-Reaction: o Ensure that the number of atoms and charges are balanced. Combine Half-Reactions: o Add the half-reactions back together, ensuring electrons are canceled out. GENERAL BIOLOGY 1 FIRST SEMESTER MIDTERM 12STEM1 Applications of REDOX Reactions: • Batteries and Fuel Cells: o Electrochemical cells use REDOX reactions to generate o electricity. Example: Lithium-ion batteries involve the oxidation of lithium at the anode and reduction at the cathode. • Corrosion: o A natural REDOX reaction where metals (like iron) oxidize, forming rust (iron oxide). • Metabolism: o REDOX reactions are central to cellular energy production in both photosynthesis and respiration. REDOX in Electrochemistry: • Electrochemical Cells: o Devices that convert chemical energy into electrical energy (or vice versa) using REDOX reactions. • Anode: o • The electrode where oxidation occurs. Cathode: o The electrode where reduction occurs. GENERAL BIOLOGY 1 FIRST SEMESTER MIDTERM 12STEM1 GENERAL BIOLOGY 1 FIRST SEMESTER MIDTERM 12STEM1 Components of an Enzyme • Enzymes: Proteins (and occasionally ribonucleic acids) that speed up biochemical reactions by modifying specific substances. • Discovery: Anselme Payen (1833) isolated the first enzyme, diastase. Wilhelm Kuhne (1878) coined the term "enzyme". Multiple Choice Pre-Test 1. Enzymes act as catalysts (a). 2. Enzymes are made of proteins (b). 3. Enzymes speed up reactions (a). 4. Substrate binds at the active site (d). 5. Molecule an enzyme reacts with is called substrate (b). Endergonic and Exergonic Reactions • Endergonic Reactions: Require energy input, energy is absorbed. • Exergonic Reactions: Release energy. Energy Reactions: • Metabolism: Series of transforming energy from one form to another. Enzyme Functionality: 1. 2. 3. 4. 5. Substrate: Reactant molecule that enzyme acts on. Active Site: Specially shaped area of the enzyme that fits around the substrate. Enzyme-Substrate Complex: Association between enzyme and substrate. Catalysis: Process the substrate undergoes, can involve breakdown or synthesis. Product: The final form of the substrate after the enzymatic reaction. GENERAL BIOLOGY 1 FIRST SEMESTER MIDTERM 12STEM1 Enzyme Mechanisms Emil Fischer's Lock-and-Key Model • Enzyme and substrate fit exactly into each other like a key into a lock. Daniel Koshland's Induced Fit Model • Substrate induces a slight change in the shape of the enzyme's active site to fit better. Important Terms • • Catalyst: Substance that increases the rate of a chemical reaction. • Cofactors: Non-protein chemical compounds or metallic ions that assist in enzyme activity. • Coenzymes: Organic non-protein compounds that bind with enzymes to catalyze reactions. • Inhibitors: o Competitive Inhibitors: Resemble substrate and compete for active site. o Noncompetitive Inhibitors: Bind to another part of the enzyme, altering active site shape. Activation Energy: Minimum amount of energy required to start a reaction. Enzyme and Metabolism 1. 2. 3. 4. 5. Metabolism: o All chemical reactions in maintaining life. Anabolism: o Builds complex molecules, requires energy. Catabolism: o Breaks down complex molecules. Catalysis vs. Catabolism: o Catalysis increases reaction rate without being consumed. o Catabolism is a type of metabolism. Energy in Metabolism: o Anabolic reactions require energy. GENERAL BIOLOGY 1 FIRST SEMESTER MIDTERM 12STEM1 Vocabulary: • • • • • • Activation Energy: Minimum energy required to initiate a reaction. Active Site: Region on enzyme where substrate binds. Cofactor/Coenzyme: Assist enzyme activity. Competitive Inhibitor: Competes for active site. Noncompetitive Inhibitor: Alters enzyme shape, affecting activity. Induced Fit: Enzyme active site’s slight shape change to fit substrate. GENERAL BIOLOGY 1 FIRST SEMESTER MIDTERM 12STEM1 Oxidation-Reduction (Redox) Reactions • Energy is essential for life processes such as order, growth, reproduction, responsiveness, and internal regulation. Definition: • Oxidation-reduction reactions are chemical reactions that involve the transfer of electrons between two species, leading to changes in their oxidation states. • • • • • Oxidation: Loss of electrons by a molecule, atom, or ion. • H₂ + F₂ → 2HF o Oxidation: ( H₂ → 2H⁺ + 2e⁻ ) o Reduction: ( F₂ + 2e⁻ → 2F⁻ ) Key Terms: Reduction: Gain of electrons by a molecule, atom, or ion. Oxidizing agent: Species that gains electrons (is reduced). Reducing agent: Species that loses electrons (is oxidized). Oxidation number: The charge an atom would have if electrons were transferred completely, without sharing. Examples: Mnemonics: • OIL RIG: Oxidation Is Loss, Reduction Is Gain (of electrons). Practice Questions: 1. MnO₄⁻ + HSO₃⁻ → MnO₄²⁻ + SO₄²⁻ o Oxidizing Agent: MnO₄⁻ o Reducing Agent: HSO₃⁻ GENERAL BIOLOGY 1 FIRST SEMESTER MIDTERM Example Reactions and Balancing: 1. C₂H₂ + O₂ → CO₂ + H₂O o Balanced Equation: o Reactants: C₂H₂, O₂ o Products: CO₂, H₂O 2. C₆H₁₂O₆ + O₂ → CO₂ + H₂O o Balanced Equation: o Reactants: C₆H₁₂O₆, O₂ o Products: CO₂, H₂O 3. CH₄ + Cl₂ → CCl₄ + HCl o Balanced Equation: o Reactants: CH₄, Cl₂ o Products: CCl₄, HCl 4. CO₂ + H₂O → C₆H₁₂O₆ + O₂ o Balanced Equation: o Reactants: CO₂, H₂O o Products: C₆H₁₂O₆, O₂ 5. H₂O → H₂ + O₂ o Balanced Equation: o Reactants: H₂O o Products: H₂, O₂ Identifying Oxidized and Reduced Species: 1. CH₂ + Cl₂ → CCl₄ + HCl o Oxidizing Agent: o Reducing Agent: 2. CO₂ + H₂O → C₆H₁₂O₆ + O₂ o Oxidizing Agent: o Reducing Agent: 3. H₂ + O₂ → H₂O o Oxidizing Agent: o Reducing Agent: 12STEM1 GENERAL BIOLOGY 1 FIRST SEMESTER MIDTERM 4. Cu + 4HNO₃ → Cu(NO₃)₂ + 2NO₂ + 2H₂O o Oxidizing Agent: o Reducing Agent: 5. PbS(s) + O₂(g) → PbO(s) + SO₂(g) o Oxidizing Agent: o Reducing Agent: 6. Cr⁺ + Sn⁴⁺ → Cr³⁺ + Sn²⁺ o Oxidizing Agent: o Reducing Agent: 12STEM1 Enzymes and Metabolic Pathways • Enzymes speed up chemical reactions and are essential in metabolic pathways. • Metabolic pathway: A series of reactions catalyzed by enzymes. o Example: One enzyme transforms a reactant into a product, which is used by the next enzyme in the pathway. GENERAL BIOLOGY 1 FIRST SEMESTER MIDTERM 12STEM1 FACTORS AFFECTING ENZYME ACTIVITY • Enzymes are biological molecules that significantly increase the rate of chemical reactions within cells. • • They help in digestion, metabolism, and binding molecules together. Enzymes are selective catalysts, speeding up specific reactions. Key Learning Points • Temperature: o Increasing temperature generally speeds up a reaction. o Extreme high temperatures -> denaturation. o Optimum temperature: Close to normal body temperature. • pH (power of hydrogen): o Each enzyme has an optimum pH range. o Extreme pH values -> denaturation. o Small pH changes can affect enzyme binding and reaction rates. • Substrate Concentration: o More substrate -> increased reaction rate, but only to a certain point. o When all enzymes are bound, adding more substrates doesn’t affect the rate. • Enzyme Concentration: o More enzymes -> faster reaction rate, given there's sufficient substrate. o Reaction doesn't speed up further once all substrates are bound. GENERAL BIOLOGY 1 FIRST SEMESTER MIDTERM 12STEM1 Effect of Temperature on Enzyme Activity • As temperature increases, the enzyme activity increases until it peaks (optimum temperature) and then declines sharply due to denaturation. Effect of pH on Enzyme Activity • Enzymes have optimum pH levels, beyond which their activity declines. Effect of Substrate Concentration on Enzyme Activity • Reaction rate increases with substrate concentration until the enzymes are saturated. Effect of Enzyme Concentration on Enzyme Activity • Reaction rate increases with enzyme concentration, provided sufficient substrate is available. Vocabulary • • • • • • • Activator: Substance that increases catalyst activity. Active Site: Specific region where the substrate binds. Concentration: Defined amount of substance. Denature: Loss of structure and function. Optimum: Best or most favorable condition. Rate of Reaction: Speed of a chemical reaction. Substrate: Molecule acted upon by an enzyme. GENERAL BIOLOGY 1 12STEM1 FIRST SEMESTER MIDTERM HOMEWORK #2 October 18, 2024 PHOTOSYNTHESIS Definition: • Photosynthesis is the process by which plants, algae, and some bacteria convert light energy into chemical energy stored in glucose. This process takes place primarily in the chloroplasts of plant cells and can be divided into two main stages: 1. 2. Light-Dependent Reactions (Occurs in the thylakoid membranes) Calvin Cycle (Occurs in the stroma) 1. Light-Dependent Reaction • The light-dependent reactions occur in the thylakoid membranes of the chloroplasts and require light to produce ATP and NADPH. Key Steps: • Photon Absorption: Chlorophyll absorbs light energy, exciting electrons to a higher energy state. • Water Splitting (Photolysis): Water molecules are split into oxygen, protons, and electrons. The oxygen is released as a byproduct. • Electron Transport Chain (ETC): Excited electrons move through the ETC, releasing energy used to pump protons into the thylakoid lumen. • ATP Synthesis (Chemiosmosis): Protons flow back into the stroma through ATP synthase, generating ATP. • NADP+ Reduction: The electrons reduce NADP+ to NADPH, which will be used in the Calvin cycle. Inputs Outputs Light energy ATP (energy carrier) H₂O NADPH (electron carrier) ADP + Pi O₂ (waste product) NADP+ GENERAL BIOLOGY 1 12STEM1 FIRST SEMESTER MIDTERM 2. Calvin Cycle (Light-Independent Reaction) • The Calvin Cycle takes place in the stroma of the chloroplasts and does not directly require light, but it uses the ATP and NADPH produced in the lightdependent reactions to synthesize glucose. Key Steps: 1. 2. 3. Carbon Fixation: CO₂ combines with ribulose-1,5-bisphosphate (RuBP) in a reaction catalyzed by the enzyme rubisco, forming 3phosphoglycerate (3-PGA). Reduction Phase: ATP and NADPH are used to reduce 3-PGA into glyceraldehyde-3-phosphate (G3P), a 3-carbon sugar. Regeneration of RuBP: Some G3P molecules exit the cycle to form glucose, while others are used to regenerate RuBP with the help of ATP. Inputs Outputs CO₂ (from the air) G3P (sugar precursor) ATP (from light reaction) ADP + Pi NADPH (from light reaction) NADP+ Calvin Cycle Diagram GENERAL BIOLOGY 1 FIRST SEMESTER MIDTERM 12STEM1 Importance of Chlorophyll • Chlorophyll is the green pigment crucial for photosynthesis. It plays several important roles: Why is Chlorophyll Important? • Light Absorption: Chlorophyll absorbs light energy (especially blue and red wavelengths) and converts it into chemical energy. • Energy Transfer: The excited electrons from chlorophyll are transferred to the electron transport chain, initiating the lightdependent reactions. • Optimal Function in Photosynthesis: Without chlorophyll, plants could not effectively harness solar energy, and photosynthesis would be severely limited. Chlorophyll Function Description Light Absorption Absorbs solar energy, particularly red and blue wavelengths Electron Excitation Excites electrons to initiate the electron transport chain Energy Transfer Transfers light energy to chemical energy in ATP and NADPH Green Coloration Reflects green light, giving plants their characteristic color Types of Chlorophyll: 1. 2. Chlorophyll a: The primary pigment involved in photosynthesis. Chlorophyll b: An accessory pigment that helps capture light energy. Chlorophyll Type Function Chlorophyll a Absorbs light in the violet-blue and red regions Chlorophyll b Expands the spectrum of light absorbed by transferring energy GENERAL BIOLOGY 1 FIRST SEMESTER MIDTERM 12STEM1 Important Terms to Remember: • Photolysis: Splitting of water molecules during light-dependent reactions. • • Rubisco: Enzyme that fixes CO₂ in the Calvin cycle. • A single plant can produce hundreds of thousands of glucose molecules every second through photosynthesis! G3P (Glyceraldehyde-3-phosphate): The sugar produced in the Calvin cycle. Fun Fact: LIGHT DEPENDENT REACTION CHLOROPHYLL