Cell structure

Cell Structures

Common Structures in Animal and Plant Cells

  • Consistency: Cell contents are often jelly-like, known as the cytoplasm, providing a medium for biochemical reactions.

  • Mitochondria:

    • Function: Provide energy for the cell by converting food into energy.

    • Process: Break down sugars (like glucose) through aerobic respiration, producing ATP (adenosine triphosphate), which is the energy currency of the cell. This process also releases carbon dioxide and water as byproducts.

  • Ribosomes:

    • Function: Site of protein synthesis, where amino acids are assembled into proteins based on the mRNA template.

    • Location: Can be found free-floating in the cytoplasm or attached to the endoplasmic reticulum, forming rough ER.

Additional Structures in Plant Cells

  • Cell Wall:

    • Composition: Made of cellulose, which is a carbohydrate; it is rigid and provides structural strength to the cell.

    • Function: Supports the cell to prevent bursting due to turgor pressure when excess water enters; it also protects the cell from mechanical stress and pathogen invasion.

  • Permanent Vacuole:

    • Description: A large sac that stores cell sap, a mixture of sugars, salts, and water, often taking up a large part of the cell's volume.

    • Function: Helps maintain cell turgor, stores nutrients and waste products, and can also play a role in plant growth by absorbing water and contributing to the cell's internal pressure, vital for support.

  • Chloroplasts:

    • Function: Site of photosynthesis, the process by which plants convert sunlight into sugars (e.g., glucose) using sunlight, carbon dioxide, and water.

    • Components: Contains chlorophyll, a green pigment necessary for absorbing light energy; also has its own DNA and ribosomes, indicating an evolutionary relationship to prokaryotic cells.

Bacterial Cells

  • Prokaryotic Cells:

    • Definition: Bacteria are unicellular organisms consisting of a single prokaryotic cell, lacking a membrane-bound nucleus.

    • Structures: Include cell membrane (controls entry and exit of substances), cell wall (provides shape and protection), ribosomes (for protein synthesis), and cytoplasm (fills the cell).

    • Absence of: Mitochondria and chloroplasts; energy production occurs in the cell membrane.

  • Genetic Material: Exists as a single circular strand of DNA, free in the cytoplasm, known as a circular chromosome or nucleoid. It contains genes necessary for survival and reproduction, encoding proteins required for basic cellular functions.

  • Plasmids: Extra small rings of DNA that carry additional genes (e.g., antibiotic resistance), which may enhance survival in hostile environments.

  • Flagella:

    • Description: Thread-like structures that can rotate; typically found in one or more numbers on bacteria.

    • Function: Propel bacteria and enable movement towards nutrients or away from harmful substances, facilitating chemotaxis.