Cell division

Cellular Respiration

  • Overview

    • Cellular respiration is a critical biological process that generates energy for cells by converting nutrients into energy in the form of adenosine triphosphate (ATP).

    • Oxygen is vital as it acts as the primary energy carrier in individual body cells.

    • Organisms with a cell nucleus and organelles (not bacteria) utilize mitochondria for cellular respiration.

  • Mitochondria Structure

    • Mitochondria contain:

    • Inner Membrane

    • Outer Membrane

    • Mitochondrial Matrix: Space between the inner membrane folds known as cristae (folds are termed "per se").

    • The mitochondrion provides the majority of energy through cellular respiration.

  • Cellular Respiration Process

    • Cellular respiration involves multiple steps and stages:

    • Glycolysis

      • Occurs in the cytoplasm.

      • Yields products like pyruvate and NADH.

      • Conversion of glucose starts here and results in the formation of pyruvate, which is crucial for energy production.

    • Intermediate Stage

      • Pyruvate converted to acetyl-CoA before entering mitochondria.

    • Citric Acid Cycle (Krebs Cycle)

      • Takes place in the mitochondrial matrix.

      • Each glucose molecule leads to the citric acid cycle turning around twice.

      • Generates:

      • CO₂: A byproduct that contributes to exhalation.

      • NADH and FADH₂: Electron carriers for the next stage.

    • Electron Transport Chain (ETC)

      • Located in the inner membrane of the mitochondria.

      • Utilizes carrier molecules for energy transfer.

      • Electrons from NADH and FADH₂ donate electrons, creating a gradient of hydrogen ions (H⁺).

      • H⁺ flow generates ATP through a molecular motor.

    • Role of Oxygen

    • Oxygen serves as the final electron acceptor in the ETC, preventing clogging of the chain and allowing cellular respiration to proceed.

    • Without oxygen, cellular respiration stops, leading to anaerobic conditions.

Energy Output from Respiration

  • Aerobic Respiration

    • Produces up to 30 ATP from one glucose molecule.

  • Anaerobic Respiration (without oxygen)

    • Generates only 2 ATP from one glucose molecule, resulting in the production of lactic acid.

    • Causes muscle fatigue and possible lactic acidosis due to the buildup of lactic acid in the body and a drop in pH affecting cellular function.

Mitochondrial DNA (mtDNA)

  • Mitochondria possess their own independent DNA, separate from nuclear DNA.

  • Contains a limited number of genes; derived from an ancient symbiotic relationship with an ancestor of eukaryotic organisms.

Cell Nucleus

  • Components of the Nucleus

    • Nuclear Envelope: Protective membrane around the nucleus.

    • Pores: Allow substances to enter/exit the nucleus.

    • Nucleolus: Site for ribosomal RNA synthesis.

    • Chromatin: DNA and protein complex organized into chromosomes.

DNA Structure and Function

  • Chromosomes

    • Comprised of coiled chromatin (DNA and histones).

    • Shape resembles an X due to centromeres holding sister chromatids together.

  • DNA Characteristics

    • Double helix structure with base pairs: Adenine (A) pairs with Thymine (T), and Cytosine (C) pairs with Guanine (G).

    • Structural stability given by phosphate sugar backbone, which is affected during DNA extraction processes.

Transcription and Translation

  • Transcription

    • Process of converting DNA into messenger RNA (mRNA).

    • Steps:

    • Initiation: RNA polymerase binds to promoter region; unzips DNA.

    • Elongation: RNA strand is synthesized; adenine pairs with uracil (U) instead of thymine (T).

    • Termination: Detachment of RNA polymerase at termination site, leading to RNA strand completion.

    • Exons (coding regions) and introns (noncoding regions) are parts of RNA, but introns are removed during processing.

    • Stability enhanced by the addition of a poly A tail.

  • Translation

    • Process of converting mRNA into proteins at ribosomes.

    • Involves three types of RNA:

    • mRNA: Carries genetic information.

    • tRNA: Transfers specific amino acids to the growing peptide chain.

    • rRNA: Forms the core of ribosome structure.

    • Stages:

    • Initiation: mRNA binds to ribosome; start codon (AUG) established.

    • Elongation: Codons read in groups of three nucleotides, adding amino acids into a polypeptide chain.

    • Termination: Stop codon indicates end, releasing final protein product.

    • Genetic code redundancy exists; multiple codons may code for the same amino acid, minimizing mutation impact.

Cell Division (Mitosis)

  • Phases of cell division:

    • Interphase: Cell performs regular functions, cell growth, DNA replication, and prepares for division.

    • Includes G1 phase (growth), S phase (DNA synthesis), and G2 phase (preparation for mitosis).

    • Mitosis: Active division process with four stages:

    • Prophase: Chromosomes condense, spindles form, and centromeres begin to separate.

    • Metaphase: Chromosomes align at the cell's equatorial plate.

    • Anaphase: Chromatids are pulled apart towards the centrioles (poles of the cell).

    • Telophase: Nuclear envelope reforms, and chromosomes decondense.

    • Cytokinesis: Complete physical separation of two daughter cells.

  • Upon completion, cells revert to interphase, and the cycle restarts (interphase will perform its activities before division begins again).

Lab Activities

  • Students will recreate the phases of mitosis using Oreos to visualize and reinforce understanding of cell division processes.

  • Participants will translate DNA sequences into corresponding amino acids using respective codons as part of the practical activity.