Recording-2025-03-08T12:06:22.157Z

Mitochondria

• Function:

  • Mitochondria are the powerhouse of the cell, generating ATP through cellular respiration using oxygen.

• Location:

  • Found in almost all eukaryotic cells, with exceptions like mature red blood cells.

• Structure:

  • Consist of two membranes:

    • Outer Membrane: Smooth.

    • Inner Membrane: Folded into structures called cristae.

  • The liquid inside is called the mitochondrial matrix, and the space between the two membranes is the intermembrane space.

• Cellular Respiration:

  • Part of the respiration occurs in the matrix, while ATP synthesis occurs in the cristae. The folding of the inner membrane increases surface area to accommodate more enzymes for ATP production.

Chloroplasts

• Function:

  • Photosynthesis occurs here, converting sunlight into food and oxygen using chlorophyll, the pigment that gives plants their green color.

• Location:

  • Present in all green parts of plants, excluding parts such as roots that do not receive sunlight.

• Structure:

  • Comprised of two membranes:

    • Outer Membrane

    • Inner Membrane

  • The fluid inside is known as the stroma, with thylakoid structures stacked like poker chips.

• Content:

  • Like mitochondria, chloroplasts contain ribosomes and circular DNA.

Endosymbiont Theory

• Overview:

  • Explains the origin of mitochondria and chloroplasts as they evolved from engulfed aerobic bacteria and photosynthetic bacteria, respectively.

• Evidence:

  • Mitochondria have two membranes, DNA, and ribosomes similar to bacteria, indicating a symbiotic relationship where the host cell provides protection and nutrients in exchange for energy production.

Peroxisomes

• Function:

  • Specialized organelles that take hydrogen atoms from various sources to convert them into hydrogen peroxide and then to water, minimizing toxic buildup in the body.

• Role in Metabolism:

  • Important for breaking down fatty acids and detoxifying alcohols and harmful compounds, particularly prevalent in liver cells.

Cytoskeleton

• Function:

  • Provides structural support, shape, and strength to cells, functioning similarly to a skeleton in larger organisms.

• Components:

  • Microtubules: Hollow tubes about 25 nm in diameter, made of tubulin dimers, responsible for cell shape, movement of organelles, and separating chromosomes during cell division.

  • Microfilaments: Thin filaments composed of actin, responsible for cellular structure and mobility, particularly in muscle contraction and amoeboid movement.

  • Intermediate Filaments: Sized between microtubules and microfilaments, providing stability and anchoring organelles in place; often made up of proteins such as keratin.

Extracellular Matrix (ECM)

• Definition:

  • The ECM consists of structures outside the cell, primarily differing in plant and animal cells.

• Plant Cells:

  • Cell walls made of cellulose provide rigidity, shape, and protection against excessive water intake.

• Animal Cells:

  • More complex, composed of proteins like collagen and fibronectin, and proteoglycans that provide structural support and facilitate communication between cells and the ECM.

Cell Junctions

• Definition:

  • Points of contact between neighboring cells that allow communication and structural integrity.

• Types in Animal Cells:

  • Tight Junctions: Prevent fluid leakage between adjacent cells, important in epithelial tissues like the intestine.

  • Desmosomes: Anchor cells together, providing strength and stability, composed largely of intermediate filaments.

  • Gap Junctions: Allow for communication and coordination between cells, enabling the passage of ions and small molecules.