The cell wall is a rigid covering that protects the cell,

It provides structural support, and gives shape to the cell.

Fungal and protistan cells also have cell walls.

The plant cell wall is mainly composed of an organic constituent called cellulose, a polysaccharide comprised of glucose units.

While the chief component of prokaryotic cell walls is peptidoglycan,

Chloroplasts

Chloroplasts are plant cell organelles that carry out photosynthesis

They have their own DNA.

Photosynthesis is the process by which plants through a  series of reactions  use carbon dioxide, water, and light energy to make glucose and oxygen.

Plants  are autotrophs as they are able to make their own food, like sugars, while animals are heterotrophs as they must ingest their food.

This is a major difference between plants and animals;

Chloroplasts have outer and inner membranes

Within the space enclosed by a chloroplast’s inner membrane there  is a set of interconnected and stacked fluid-filled membrane sacs called thylakoids.

Each stack of thylakoids is called a granum (plural = grana).

The fluid enclosed by the inner membrane that surrounds the grana is called the stroma.

The space inside the thylakoid membranes is called the thylakoid space.

The chloroplasts contain a green pigment called chlorophyll, which captures the light energy for carrying out the process of photosynthesis.

The light harvesting reactions take place in the thylakoid membranes.

The synthesis of sugar takes place in the stroma.

Like plant cells, photosynthetic protists also have chloroplasts. Some bacteria perform photosynthesis, but their chlorophyll is not relegated to an organelle.

“Chloroplast structure” by OpenStaxis licensed under CC BY 4.0

Watch the Video on Chloroplast structure and Function.

The Central Vacuole

The central vacuole is an unique and essential component of plant cell and occupies most of the space of the cell.

The central vacuole plays a key role in regulating the concentration of water in the cell against the changing environmental conditions.

The the liquid inside the central vacuole provides turgor pressure, which is the outward pressure caused by the fluid inside the cell.

The wilting of a plant when we forget to water it for few days is because of shrinking of the central vacuole caused due to the movement of water out of the central vacuole ,as the water concentration in the soil becomes lower than the water concentration in the plant.

This loss of support to the cell walls of plant cells results in the wilted appearance of the plant.

On the contrary when the  central vacuole holds more water, the cell gets larger without having to invest a lot of energy in synthesizing new cytoplasm.

The  fluid inside the central vacuole has a very bitter taste, which discourages consumption by insects and animals.

The central vacuole also functions to store proteins in developing seed cells.

In plant cells, the digestive processes take place in vacuoles.

Plasmodesmata

Plasmodesmata(singular = plasmodesma) are junctions between plant cells,

Neighboring plant cells cannot touch one another because they are separated by the cell walls

The Plasmodesmata are numerous channels that pass between the cell walls of adjacent plant cells,

They serve to connect the cytoplasm , signal molecules and  transport the nutrients  from one plant cell to another.

Organelles/ cell structures specific for Animal cell

The Centrosome

The centrosome is a microtubule-organizing center. It is  found near the nuclei of animal cells and contains  a pair of centrioles,

The two centrioles  lie perpendicular to each other.

Each centriole is a cylinder of nine triplets of microtubules. Non tubulin serves to hold the microtubule triplets .

The microtubule originate from the centrosome .

The centrosome replicates itself before a cell division.

The centrioles  pull the duplicated chromosomes to opposite ends of the dividing cell.

The exact function of the centrioles in cell division is however not  clear as cells that have had the centrosome removed can still divide; and plant cells, which lack centrosomes, are capable of cell division.

“Centriole structure” by Libre Text biology is licensed under CC BY-SA 4.0

Lysosomes

 The lysosomes are the cell’s “garbage disposal units ” .

The lysosomes contain enzymes that  aid the breakdown of proteins, polysaccharides, lipids, nucleic acids, and even worn-out organelles.

These enzymes are active at a much lower pH than that of the cytoplasm. Therefore, the pH within lysosomes is more acidic than the pH of the cytoplasm.

Many reactions that take place in the cytoplasm could not occur at a low pH,

this is the advantage of compartmentalizing the eukaryotic cell into organelles .

“lysosome “ by Open stax is licensed under CC BY 4.0

Extracellular Matrix of Animal Cells

Most animal cells release materials into the extracellular space.

The primary components of the extra cellular matrix  are glycoproteins and the protein collagen. Collectively, these materials are called the extracellular matrix .

Their function  include :

• Hold the cells together to form a tissue
• Allows the cells within the tissue to communicate with each other.