Plant Cell and Animal Cell

The Kingdom Plantae includes multicellular eukaryotes that are primarily autotrophic, meaning they produce their own food. Plant cells are distinct from animal cells due to specific organelles like chloroplasts, cell walls, and vacuoles. There are approximately 400,000 identified plant species, though many more remain undiscovered.

• Plant cell sizes typically range from 10 to 100 µm and are crucial for photosynthesis, making green plants autotrophs.
• The cell wall, composed of cellulose, provides structural support and strength to plant cells.

Plant cells are the basic building blocks of plant life, carrying out all of the actions necessary for survival. Photosynthesis is the conversion of light energy, CO2, and water into food. It occurs in the cells' chloroplasts. The following are some examples of specialised plant cells:

1. Collenchyma Cells: These are elongated, living cells with irregularly thickened walls. They are flexible, allowing them to stretch and support plant growth by adapting to organ expansion.
2. Sclerenchyma Cells: These cells are rigid and provide structural support in mature plant regions that no longer grow. They are usually dead at maturity, have thick secondary walls, and contain a high percentage of cellulose.
3. Parenchyma Cells: These simple tissue cells make up most plant tissues, like the soft parts of leaves and fruit. They are involved in photosynthesis, storage of nutrients, and help in the plant's healing processes.
4. Xylem Cells: Responsible for transporting water and dissolved minerals from the roots to the leaves. Components include tracheids, vessels, and xylem fibres, which facilitate this upward movement.
5. Phloem Cells: These cells transport nutrients, like sugars and amino acids, produced by photosynthesis to different parts of the plant, moving food from the leaves to the roots.

The Kingdom Animalia comprises three-fourths of all species on Earth. The human body contains around 10¹⁴ cells, ranging in size from 10 to 30 µm in diameter.

• Animal cells lack a cell wall and chloroplasts, which sets them apart from plant cells and means they cannot make their own food.
• Most animal cells have three main components: the nucleus, cell membrane, and cytoplasm.
• The absence of cell walls is believed to have allowed the evolution of more specialised cells, tissues, and organs, enabling functions like movement supported by nerves and muscles.

All cells function collectively to support the survival of the organism. Groups of similar tissues combine to form various organs, such as the heart and lungs. These organs then coordinate to create organ systems, including the nervous, digestive, and circulatory systems. A few types of animal cells are:

1. Skin Cells: Located in the dermal and epidermal layers, these cells prevent water loss and act as a protective barrier against the external environment.
2. Bone Cells: Responsible for forming the skeleton and bones, they communicate to maintain bone balance, structure, and function, and they aid in body movement.
3. Muscle Cells: Protect delicate organs and, when grouped, enable movement of limbs and tissues.
4. Blood Cells: Function as transporters in the body, delivering hormones, nutrients, and oxygen through the bloodstream.
5. Nerve Cells: Specialised for transmitting impulses, neurons send and receive messages in the brain and consist of a cell body, an axon, and dendrites.

Cells come in different shapes, like circular, rod-shaped, columnar, spiral, oval, and rectangular, depending on their function. 

Various cells

Each cell contains organelles that help carry out life processes. Scientists study these organelles with an electron microscope, which can magnify objects two billion times their actual size.