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Cell - Notes, Biology - General Test Preparation for CUET

Cell

CellCell

  • Study which deals with the cell is called cytology.
  • Cell was first discovered by Robert Hooke in 1665 in sections of cork. He only coined the term ‘Cell’.

Cell Theory states that :

  • All living things are composed of cells and their products.
  • All cells arise from pre – existing Cells.
  • All cells are basically alike in Chemical Composition and Metabolic Activities.
  • The function of an organism as a whole is the outcome of the activities and interaction of the Constituent Cells.

Types of Cells :

  • In a typical cell, the protoplasm consists of nucleus and cytoplasm.
  • Depending on the type of nucleus present, the cells are of two types :
    • Prokaryotic cell (found in blue – green algae, bacteria and Pleuropneumonia like organisms (PPLO).
    • Eukaryotic Cell.
  • On the basis of number of cells, the organisms are classified as Unicellular and Multi – cellular organisms.

Prokaryotic Cell

Eukaryotic Cell

It is simple and primitive in nature.

It is developed and comparatively complex in nature.

The nucleus is not well organized. It has no nuclear membrane and nucleolus.

The nucleus is well organized. Nuclear membrane and nucleolus are present.

The cell has no membrane bound organelles except ribosomal granules.

The cell contains almost all the membrane bound organelles.

Chromosomes are not formed in this cell during cell division.

Chromosomes are formed in the nucleus during cell division.

Single DNA thread remains freely in the nuclear material.

DNA is present in the nuclear reticulum or chromosomes.

 

Plant Cell

Animal Cell

A plant cell has a rigid wall on the outside.

Cell wall is absent.

It is usually larger in size.

An animal cell is comparatively smaller in size

It cannot change its shape

An animal cell can often change its shape

Plastids are found in plant cells.

Plastids are usually absent.

Plant cells exposed to sunlight possess chlorophyll containing plastids called chloroplasts.

Chlorophyll is absent

A mature plant cell contains a large central vacuole.

An animal cell often possesses many small vacuoles.

Nucleus lies on one side in the peripheral cytoplasm.

Nucleus usually lies in the center.

Mitochondria are comparatively fewer.

Mitochondria are generally more numerous.

Cristae are tubular in plant mitochondria.

Cristae are plate - like in animal mitochondria.

Plant cells do not burst if placed in hypotonic solution due to the presence of cell wall.

Animal cells usually burst if placed in hypotonic solution unless and until they possess contractile vacuoles.

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FAQs on Cell - Notes, Biology - General Test Preparation for CUET

1. What is a cell?
Ans. A cell is the basic structural and functional unit of all living organisms. It is the smallest unit of life that can replicate independently and carry out essential functions such as metabolism and reproduction.
2. What are the main types of cells?
Ans. There are two main types of cells: prokaryotic and eukaryotic cells. Prokaryotic cells, such as bacteria, lack a nucleus and other membrane-bound organelles. Eukaryotic cells, found in plants, animals, fungi, and protists, have a nucleus and various membrane-bound organelles.
3. How do cells communicate with each other?
Ans. Cells communicate with each other through various mechanisms, including chemical signals. They release signaling molecules, such as hormones or neurotransmitters, which bind to specific receptors on the target cells, triggering a response. Additionally, cells can communicate through direct contact or by exchanging molecules through gap junctions or plasmodesmata.
4. What is the role of the cell membrane?
Ans. The cell membrane, also known as the plasma membrane, acts as a barrier that separates the cell's internal environment from the external environment. It controls the movement of substances in and out of the cell, allowing selective exchange of molecules necessary for cellular processes. Additionally, the cell membrane contains receptors and proteins that play a role in cell signaling and recognition.
5. How do cells reproduce?
Ans. Cells reproduce through two main methods: mitosis and meiosis. In mitosis, a single cell divides into two identical daughter cells, each with the same number of chromosomes as the parent cell. This process is essential for growth, tissue repair, and asexual reproduction. Meiosis, on the other hand, involves the division of cells to produce gametes (sex cells) with half the number of chromosomes, which are necessary for sexual reproduction.
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