Unit 1
Lab 2

Lab 2

Cellular Anatomy and Mitosis

Cell Structures

Cell Structure

  1. Nucleus:

    • Controls cellular activities and stores genetic material (DNA).
    • Regulates gene expression and mediates DNA replication and RNA synthesis.

  2. Nuclear Membrane (Nuclear Envelope):

    • Separates the nucleus from the cytoplasm.
    • Regulates the passage of molecules (e.g., RNA, proteins) between the nucleus and cytoplasm through nuclear pores.

  3. Ribosomes:

    • Synthesize proteins by translating messenger RNA (mRNA) into polypeptide chains.
    • Found either free in the cytosol or attached to the rough ER.

  4. Secretory Vesicles:

    • Store and transport proteins and other molecules to the cell membrane for secretion outside the cell.

  5. Rough Endoplasmic Reticulum (Rough ER):

    • Synthesizes and processes proteins (due to the presence of ribosomes on its surface).
    • Plays a role in protein folding and transport.

  6. Golgi Apparatus:

    • Modifies, sorts, and packages proteins and lipids for secretion or delivery to other organelles.
    • Forms secretory vesicles for transport.

  7. Plasma Membrane:

    • Acts as a selective barrier, regulating the movement of substances in and out of the cell.
    • Maintains cell integrity and facilitates cell communication.
    • Made of phospholipid bilayer. Cholesterol gives rigidity. Microtubles give shape.

  8. Smooth Endoplasmic Reticulum (Smooth ER):

    • Synthesizes lipids, phospholipids, and steroids.
    • Detoxifies chemicals and stores calcium ions.

  9. Mitochondria:

    • Generate energy (ATP) through cellular respiration (oxidative phosphorylation) happens on inner membrane. CTA cycle, krebs cycle happens between membranes.
    • Involved in apoptosis (programmed cell death) and calcium signaling.
    • Double membrane bound organelle (outer and inner membrane).

  10. Peroxisomes:

    • non secretory vesicles filled with peroxide for redox reactions.
    • Break down fatty acids and detoxify harmful substances (e.g., hydrogen peroxide).
    • Participate in lipid biosynthesis and oxidative reactions.

  11. Cytosol:

    • The liquid portion of the cytoplasm where organelles are suspended.
    • Site of many metabolic reactions and transportation of molecules within the cell.

  12. Lysosome:

    • Contains acidic digestive enzymes to break down waste materials, cellular debris, and foreign invaders (e.g., bacteria).
    • Involved in autophagy (recycling of cellular components).

  13. Centrioles:

    • Organize microtubules and form the spindle apparatus to modulate cell division (mitosis and meiosis).
    • Contribute to the formation of cilia and flagella in some cells.

Mitosis

The process by which most cells divide (except germ cells which undergo meiosis). Mitosis is the process of cell division that results in two genetically identical daughter cells. It consists of several distinct phases, each with specific events:

1. Interphase (Not technically part of mitosis, but precedes it):

  • The cell prepares for division by growing, replicating its DNA, and synthesizing proteins.
  • Chromosomes are in a relaxed, uncondensed state (chromatin).
  • Consists of three subphases:
    • G1 phase: Cell growth and normal functions.
    • S phase: DNA replication occurs.
    • G2 phase: Further growth and preparation for mitosis.

2. Prophase:

  • looks like spaghetti
  • Chromatin condenses into visible chromosomes, each consisting of two sister chromatids joined at the centromere.
  • The nuclear envelope begins to break down.
  • The mitotic spindle (composed of microtubules) starts to form, and centrosomes move to opposite poles of the cell.

3. Prometaphase:

  • The nuclear envelope fully disintegrates.
  • Spindle microtubules attach to the kinetochores (protein structures on the centromeres of chromosomes).
  • Chromosomes begin to move toward the center (equator) of the cell.

4. Metaphase:

  • Chromosomes align at the metaphase plate (the equatorial plane of the cell).
  • Spindle microtubules from opposite poles are attached to the kinetochores of each chromosome, ensuring proper alignment.

5. Anaphase:

  • Sister chromatids are pulled apart by the shortening of spindle microtubules.
  • Separated chromatids (now called chromosomes) move toward opposite poles of the cell.
  • The cell elongates as non-kinetochore microtubules push the poles apart.

6. Telophase:

  • nuclei are starting to reform
  • membrane will visibly start to pinch together.
  • Chromosomes reach the opposite poles and begin to decondense into chromatin.
  • Nuclear envelopes re-form around the two sets of chromosomes.
  • The mitotic spindle disassembles.

7. Cytokinesis (Occurs concurrently with telophase):

  • The cytoplasm divides, resulting in two separate daughter cells.
  • In animal cells, a cleavage furrow forms and pinches the cell in two.
  • In plant cells, a cell plate forms to divide the cell.

After mitosis and cytokinesis, the daughter cells enter interphase and the cell cycle begins anew.

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