Nucleus

• Structure: The nucleus is a large, membrane-bound organelle containing the cell’s genetic material. It is surrounded by a double membrane called the nuclear envelope, which has pores for the transport of molecules.
• Function: The nucleus houses DNA, which is organized into chromosomes. It controls cell activities by regulating gene expression and mediating the replication of DNA during cell division.

Mitochondria

• Structure: Mitochondria are double-membraned organelles with an outer membrane and a highly folded inner membrane that forms structures called cristae.
• Function: Mitochondria are the powerhouses of the cell, generating ATP through oxidative phosphorylation in the process of cellular respiration. They also play a role in apoptosis (programmed cell death) and calcium storage.

Endoplasmic Reticulum (ER)

• Structure: The ER is a network of membranous tubules and sacs. It is of two types: rough ER (RER), studded with ribosomes, and smooth ER (SER), which lacks ribosomes.
• Function: The RER is involved in protein synthesis and folding, while the SER is responsible for lipid synthesis, detoxification, and calcium ion storage.

Golgi Apparatus

• Structure: The Golgi apparatus consists of a series of flattened, membrane-bound sacs known as cisternae.
• Function: It modifies, sorts, and packages proteins and lipids for secretion or delivery to other organelles. The Golgi apparatus is also involved in the formation of lysosomes.

Lysosomes

• Structure: Lysosomes are small, membrane-bound vesicles containing hydrolytic enzymes.
• Function: They break down macromolecules, old cell parts, and microorganisms. Lysosomes are the cell’s waste disposal system, playing a key role in intracellular digestion and recycling of cellular components.

Peroxisomes

• Structure: Peroxisomes are small, membrane-bound organelles containing enzymes, notably catalase and oxidases.
• Function: They detoxify harmful substances, including hydrogen peroxide, and are involved in lipid metabolism and the oxidation of fatty acids.

Ribosomes

• Structure: Ribosomes are small, non-membranous structures composed of ribosomal RNA and proteins. They can be found floating freely in the cytoplasm or attached to the rough ER.
• Function: Ribosomes are the sites of protein synthesis, translating genetic instructions from messenger RNA to build polypeptides.

Plasma Membrane

• Structure: The plasma membrane is a phospholipid bilayer with embedded proteins, carbohydrates, and cholesterol, creating a semi-permeable barrier around the cell.
• Function: It regulates the movement of substances in and out of the cell, facilitates cell communication and signaling, and maintains the cell’s structural integrity.

Cytoskeleton

• Structure: The cytoskeleton is a network of protein fibers, including microfilaments (actin), intermediate filaments, and microtubules.
• Function: It provides mechanical support, maintains cell shape, enables cell movement, and plays a role in intracellular transport and cell division.

Chloroplasts (in plant cells)

• Structure: Chloroplasts are double-membraned organelles containing chlorophyll, with internal structures called thylakoids stacked into grana.
• Function: They are the site of photosynthesis, converting light energy into chemical energy stored in glucose. Chloroplasts also contribute to the synthesis of fatty acids and amino acids.

Vacuoles

• Structure: Vacuoles are large, membrane-bound sacs, with a prominent central vacuole found in plant cells.
• Function: They store nutrients, waste products, and help maintain turgor pressure in plant cells. Vacuoles also play a role in the degradation of cellular components and can store defensive compounds in plants.

Centrosomes and Centrioles

• Structure: The centrosome is an organelle that serves as the main microtubule-organizing center. It contains two centrioles, which are cylindrical structures made of microtubules.
• Function: Centrosomes play a crucial role in organizing the mitotic spindle during cell division, ensuring proper chromosome segregation.