organelles

1. Nucleus

  • Structure: Surrounded by a double membrane called the nuclear envelope, contains nucleoplasm, and inside it, there's the nucleolus (where ribosomes are made).

  • Function: Stores genetic material (DNA) and controls cell activities.

2. Mitochondria (Powerhouse of the cell)

  • Structure: Has a double membrane—outer membrane (smooth) and inner membrane (folded into cristae to increase surface area), with a fluid-filled matrix inside.

  • Function: Produces ATP (energy) through cellular respiration.

3. Ribosomes

  • Structure: Small, bead-like structures made of RNA and proteins. Found free-floating in the cytoplasm or attached to the rough ER.

  • Function: Protein synthesis.

4. Endoplasmic Reticulum (ER)

  • Structure: Network of membranes connected to the nuclear envelope. Two types:

    • Rough ER (has ribosomes on surface, looks bumpy)

    • Smooth ER (no ribosomes, smooth appearance)

  • Function:

    • Rough ER: Helps in protein synthesis and transport.

    • Smooth ER: Synthesizes lipids and detoxifies chemicals.

5. Golgi Apparatus

  • Structure: Flattened, stacked sacs called cisternae.

  • Function: Modifies, packages, and sorts proteins/lipids into vesicles for transport.

6. Lysosomes (Only in animal cells)

  • Structure: Small membrane-bound sacs filled with digestive enzymes.

  • Function: Breaks down waste, damaged cell parts, and foreign invaders.

7. Peroxisomes

  • Structure: Similar to lysosomes, but contain oxidative enzymes.

  • Function: Breaks down fatty acids and detoxifies hydrogen peroxide.

8. Cytoskeleton

  • Structure: Network of protein filaments:

    • Microfilaments (thin, actin-based)

    • Intermediate filaments (medium-sized, structural support)

    • Microtubules (thick, help in cell division and movement)

  • Function: Provides shape, movement, and intracellular transport.

9. Centrioles (Only in animal cells)

  • Structure: Cylindrical structures made of microtubules.

  • Function: Helps in cell division (spindle fiber formation).

10. Chloroplasts (Only in plant cells)

  • Structure: Double membrane, with internal stacked membranes called thylakoids (which form grana), and fluid-filled stroma.

  • Function: Photosynthesis—converts sunlight into energy (glucose).

11. Vacuoles

  • Structure: Membrane-bound sacs filled with water, nutrients, or waste.

  • Function:

    • Large central vacuole (plants): Stores water, maintains cell pressure.

    • Small vacuoles (animals): Temporary storage.

12. Plasma Membrane

  • Structure: Phospholipid bilayer with embedded proteins.

  • Function: Controls what enters and exits the cell (selectively permeable).

13. Cell Wall (Only in plants, fungi, and bacteria)

  • Structure: Rigid outer layer made of cellulose (plants), chitin (fungi), or peptidoglycan (bacteria).

  • Function: Provides support and protection.

Flagellum (Plural: Flagella)

  • Structure: Long, whip-like structure made of microtubules in a 9+2 arrangement. It extends from the cell surface and is covered by the plasma membrane.

  • Function: Helps in cell movement (like a propeller). Found in some bacteria, protists, and sperm cells in animals.

3. Chromatin

  • Structure: A complex of DNA and proteins (histones) found inside the nucleus.

  • Function: Stores genetic information and controls gene expression. During cell division, chromatin condenses to form chromosomes.

4. Cytoskeleton

  • Structure: A network of protein filaments and tubules, including:

    • Microfilaments (actin filaments – thin, for movement and shape)

    • Intermediate filaments (medium-sized, for structural support)

    • Microtubules (thick, for transport and division)

  • Function: Provides shape, structure, and movement of the cell. Helps in intracellular transport (like a railway for vesicles).

5. Vesicles

  • Structure: Small, membrane-bound sacs that bud off from the Golgi body, ER, or plasma membrane.

  • Function: Transport materials (proteins, lipids, waste) around or out of the cell. Different types include:

    • Transport vesicles (move materials within the cell)

    • Secretory vesicles (export substances outside the cell)

    • Lysosomes (vesicles with digestive enzymes)

6. Cilia

  • Structure: Short, hair-like projections made of microtubules (same 9+2 arrangement as flagella but shorter and more numerous).

  • Function: Move fluid, mucus, or particles across the cell surface. Found in cells lining the respiratory tract (to clear mucus) and in some unicellular organisms for movement.

  • Cytoplasm

    • Structure:

      • A gel-like fluid that fills the inside of the cell, made mostly of water, salts, and proteins.

      • Contains organelles, enzymes, and nutrients needed for cell function.

      • Includes the cytosol (the fluid part) and everything inside the cell except the nucleus.

    • Function:

      • Holds and supports organelles in place.

      • Provides a medium for chemical reactions to occur.

      • Transports materials within the cell.

      • Maintains cell shape by working with the cytoskeleton.

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