Glycolysis

Overview of Glycolysis

Glycolysis is the first step in cellular respiration, occurring in the cytosol of cells. It is a metabolic pathway that breaks down glucose into pyruvate, generating energy in the form of ATP.

• Aerobic vs. Anaerobic: Aerobic processes require oxygen, while anaerobic processes do not.

• ATP Yield: Glycolysis nets 2 ATP molecules per glucose.

• Location: Glycolysis occurs in the cytosol, not the mitochondria.

• Oxygen Requirement: Glycolysis does not require oxygen.

• Fates of Pyruvate: Pyruvate can enter aerobic respiration (mitochondria), undergo fermentation (anaerobic), or be converted to other metabolites.

• Prokaryotes: Prokaryotes perform glycolysis.

• Reactants: Glucose, NAD+, ADP, and inorganic phosphate.

• Products: Pyruvate, NADH, ATP.

Fermentation & Cellular Respiration

Fermentation

Fermentation is an anaerobic process that allows cells to regenerate NAD+ and produce ATP when oxygen is unavailable.

• ATP Production: Fermentation produces little ATP compared to cellular respiration.

• Oxygen Requirement: Fermentation does not require oxygen.

• Types: Muscle cells use lactic acid fermentation (producing lactate); yeast uses alcoholic fermentation (producing ethanol).

• Evolutionary Importance: Fermentation is ancient and supports glycolysis as a unifying pathway.

• NAD+ Regeneration: Fermentation regenerates NAD+ from NADH.

Cellular Respiration

Cellular respiration is a multi-step process that converts glucose into ATP using oxygen. It includes glycolysis, Acetyl CoA synthesis, Krebs cycle, and the electron transport chain (ETC).

• Acetyl CoA Synthesis: Reactants: Pyruvate, CoA, NAD+; Products: Acetyl CoA, CO2, NADH. CoA is recycled.

• Location: Acetyl CoA synthesis and Krebs cycle occur in the mitochondria.

• Krebs Cycle: Reactants: Acetyl CoA, NAD+, FAD, ADP; Products: CO2, NADH, FADH2, ATP.

• Citric Acid: The cycle is named for citric acid, which is formed and broken down in the process.

• ATP Yield: Krebs cycle nets 2 ATP per glucose.

• Folded Inner Membrane: Increases surface area for ETC and ATP production.

Electron Transport Chain (ETC) and Chemiosmosis

The ETC is a series of protein complexes in the mitochondrial inner membrane that transfer electrons and pump protons to generate ATP.

• ATP Synthase: Enzyme that synthesizes ATP from ADP and inorganic phosphate using energy from proton flow.

• Energy Source: Energy comes from the movement of H+ ions down their concentration gradient (chemiosmosis).

• Electron Carriers: NADH and FADH2 donate electrons to the ETC.

• Respiratory Complexes: Four main complexes; some pump H+ ions.

• Active Transport: H+ ions are pumped against their gradient, creating potential energy.

• ATP Production: ETC alone produces about 28-32 ATP per glucose; total cellular respiration yields about 30-36 ATP.

ETC Details

• Electron Flow: Electrons from NADH and FADH2 move through complexes, releasing energy.

• CO2 Release: CO2 is released during Acetyl CoA synthesis and Krebs cycle.

• NAD+ vs. NADH: NAD+ is the oxidized form; NADH is the reduced, electron-carrying form.

• H+ Role: H+ ions are pumped to create a gradient used for ATP synthesis.

Photosynthesis

Overview of Photosynthesis

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

• Location: Occurs in chloroplasts, not human cells.

• Wavelengths: Light wavelength affects photosynthesis; green light is less effective because chlorophyll reflects it.

• Reactants: CO2, H2O, light energy.

• Products: Glucose, O2.

• Chlorophyll: Main pigment for capturing light.

• Accessory Pigments: Carotenoids and anthocyanins broaden the spectrum of light absorbed.

• Thylakoid Membranes: Folded structure increases surface area for light reactions.

Light Reactions and Calvin Cycle

• Light Reaction Goal: Convert light energy to chemical energy (ATP, NADPH).

• Products: ATP, NADPH, O2.

• Photosystems: Chlorophyll is organized into photosystems for efficient energy transfer.

• ETC Comparison: Both photosynthesis and respiration use ETCs, but photosynthesis uses light energy and produces NADPH.

• ATP Use: ATP from light reactions is used in the Calvin cycle.

• Calvin Cycle: Produces G3P (a precursor to glucose); uses ATP and NADPH.

• G3P Fates: Can be used to make glucose or regenerate RuBP.

• RuBP Cycling: Regenerates the molecule needed for CO2 fixation.

• Photosynthesis vs. Respiration: Photosynthesis does not replace respiration; both are essential.

Cellular Reproduction

Overview of Cellular Reproduction

Cellular reproduction is the process by which cells divide to produce new cells, essential for growth, repair, and reproduction.

• Types: Occurs in both unicellular and multicellular organisms; bacteria reproduce by binary fission.

• Genome: The complete set of genetic material in a cell.

• Chromosome: DNA molecule with associated proteins; humans have 46 chromosomes (23 pairs).

• Functions of Mitosis: Growth, repair, asexual reproduction.

• Sister Chromatids: Identical copies of a chromosome connected at the centromere.

• DNA Packing: DNA is wrapped around histones for efficient storage.

• Ploidy: Diploid (2n) cells have two sets of chromosomes; haploid (n) cells have one.

• Cell Cycle Phases: Interphase (G1, S, G2), Mitotic phase (prophase, metaphase, anaphase, telophase, cytokinesis).

• Centromere: Region where sister chromatids are joined.

• Spindle Fibers: Facilitate chromosome movement during division.

• Cleavage Furrow vs. Cell Plate: Animal cells form a cleavage furrow; plant cells form a cell plate.

Meiosis

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

• Cells: Meiosis occurs in germ cells.

• Gametes: Haploid reproductive cells.

• Daughter Cells: Four non-identical haploid cells.

• Meiosis I: Homologous chromosomes are separated.

• Meiosis II: Sister chromatids are separated.

• Synapsis: Homologous chromosomes pair up.

• Crossing Over: Exchange of genetic material between homologs.

• Independent Assortment: Random distribution of chromosomes increases variation.

• Telomeres: Protective chromosome ends; senescence prevents cancer.

• Apoptosis: Programmed cell death.

• p53: Tumor suppressor protein.

• Cyclins: Proteins regulating cell cycle.

Comparison Table: Mitosis vs. Meiosis

Additional info:

• Some explanations and context were inferred to ensure completeness and clarity for exam preparation.