What is Cell ?

A cell is the smallest unit of life that can function independently and make up all living organisms. Cells are often referred to as the "building blocks of life" because they carry out essential processes necessary for survival, such as metabolism, growth, and reproduction. They can be classified into two main types: prokaryotic cells, which lack a nucleus (like bacteria), and eukaryotic cells, which have a nucleus and membrane-bound organelles (like plant and animal cells).

What is the Difference Between Plant and Animal Cells

Plant cells and animal cells have distinct differences in structure and function.

1. Cell Wall: Plant cells have a rigid cell wall made of cellulose, while animal cells do not.
2. Chloroplasts: Plant cells contain chloroplasts for photosynthesis, absent in animal cells.
3. Shape: Plant cells are typically rectangular due to the cell wall, whereas animal cells are more round or irregular.
4. Vacuole: Plant cells have a large central vacuole for storage, while animal cells have small or no vacuoles.
5. Centrioles: Centrioles are present in animal cells but usually absent in plant cells.

Types of Cells

Cells can be broadly classified into two main types:

1. Prokaryotic Cells

• Definition: Simple, single-celled organisms that lack a nucleus and membrane-bound organelles.
• Examples: Bacteria and Archaea.
• Characteristics:
  • Smaller in size (typically 0.1 to 5.0 micrometers).
  • Genetic material is found in a nucleoid region.
  • Often have a cell wall.
  • Reproduce asexually through binary fission.

2. Eukaryotic Cells

• Definition: More complex cells that contain a nucleus and membrane-bound organelles.
• Examples: Plant cells, animal cells, fungi, and protists.
• Characteristics:
  • Larger in size (typically 10 to 100 micrometers).
  • Genetic material is contained within a nucleus.
  • Possess various organelles such as mitochondria, endoplasmic reticulum, and Golgi apparatus.
  • Can reproduce asexually (mitosis) or sexually (meiosis).

Subcategories of Eukaryotic Cells

• Animal Cells: Lack a cell wall and chloroplasts; have lysosomes and centrioles.

• Plant Cells: Have a cell wall, chloroplasts for photosynthesis, and large central vacuoles.

Each type of cell has unique structures and functions that contribute to the overall diversity of life.

Walls vs. membranes

Plant cells have cell walls made with tough compounds called lignin and cellulose. This makes the cell tough and rigid which strengthens the trees. 

Animal cells are contained within the cell membrane in a flexible container. This membrane does not affect the structure of the cell but regulates the organelles contained within the cell. 

Similarities between animal and plant cells

• Both have ribosomes
• Both have plasma membrane
• Both have endoplasmic reticulum
• Both have well-defined cytoplasm and nucleus
• The DNA for both plant and animal cells are surrounded by a nuclear membrane

All plant cells have Vaculose, but only a few animal cells have them

Vaculose are intercellular water balloons that keep the cells plump by creating turgor pressure. Plant cells contain vacuoles, but only some species of animal cells contain them. The vacuoles push the cell membrane against the cell wall and help the plant maintain its shape. As the plant is dying or the fruit or vegetable begins to grow stale, it is losing its turgor pressure into vacuoles. 

The Centrosome near the nuclei

The centrosome, which is found near the nuclei of animal cells organises the microtubules. Each centrosome contains two structures lying perpendicular to one another called the centrioles. Their purpose is to pull duplicate chromosomes from the opposite ends of the dividing cells. Plant cells do not have centrosomes. Yet, they are capable of cell division while animal cells can still divide despite the presence of the centrosome, making its role unclear.

The digestive process of plant and animal cells

has lysosomes that are their waste disposal system. These aren’t present in plant cells, whose digestive processes take place in vacuoles. The enzymes in lysosomes break down proteins, lipids, polysaccharides, nucleic acids and old organelles. 

Only plant cells have Chloroplasts

Chloroplast is only found in plants and helps in the important function of converting sunlight into glucose compounds. Chloroplasts occur in the leaves, stems and fruits of the plant. 

A central vacuole

The central vacuole regulates the cell’s water concentration with respect to changing environmental conditions. This is how plants survive through hot summer months when there is not rain and groundwater supply has run dry. In the absence of water, the plats wilt as the water move out of the central vacuoles and cytoplasm. When the central vacole shrinks, the cell wall is left unsupported, which in turn affects the plants appearance. Once the plant receives fresh water, the central vacuole recharges and the cell gets larger once again. 

Unique roles of plant and animal cells

The purposes of plant and animal cells are very different as per their nature and structure. At its simplest level, plants inhale carbon dioxide and animals exhale them and animals inhale oxygen and plants exhale them. Plants only need sunshine, water, soil and air to make their food and survive, all while standing in one place. Animals have to hunt, cultivate, gather and cook their food. They need oxygen to breathe and special cell types, tissues and organs for movement. Plant cells make them far more self-sufficient than animal cells. 

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