April 15, 2023

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The Cell – Its Structure

And Functions

[In Detail]A Group PowerPoint

Presentation By

Group 1

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The Discovery Of A Cell Cells emerged on Earth at least 3.5 billion

years ago. In 1655, the English scientist Robert Hooke made an observation that would change basic biological theory and research forever. While examining a dried section of cork tree with a crude light microscope, he observed small chambers and named them as cells.

After 175 years, research led to the formation of the cell theory. In its modern form, this theorem has four basic parts:

I. 1. The cell is the basic structural and functional unit of life; all organisms are composed of cells.

II. 2. All cells are produced by the division of pre-existing cells. Each cell contains genetic material that is passed down during this process.

III. 3. All basic chemical and physiological functions are carried out inside of cells.

IV. 4. The activities of cells depends on the activities of subcellular structures within the cell.

What is a Cell ? The cell (from Latin cella, meaning “small room”)is the basic structural, functional and biological unit of all known living organisms. Cells are the smallest unit of life that can reproduce independently, and are often called the "building blocks of life". The study of cells is called cell biology.

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Variation In Cell Number, Shape And Size In Living Organisms

Cell Number

Human body has trillions of cells which vary in shapes and sizes. Different groups of cells perform a variety of functions. living organisms can be classified into two categories-

a) Organisms made of more than one cell are called multicellular organisms. For example, human beings ,animals etc.

b) The single-celled organisms are called unicellular organisms. For example, amoeba, euglena etc.

The both type organism can performs all the necessary functions for their existence.

Cell Shape

Generally, cells are round, spherical or elongated. Some cells are long and pointed at both ends. They exhibit spindle shape . Cells sometimes are quite long. Some are

branched like the nerve cell or a neuron.

Cell Size

Cell vary in size. The smallest cell is PPLO(Pleuro pneumonia-like organism)and is about 0.1µm in diameter. The ostrich egg is the largest cell with 1,70,000µm in diameter.

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Part Of The Cell

Cell Membrane• Cell Wall

Cytoplasm

Nucleus• Nucleoplasm• Chromosomes• DNA

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Cell Membrane The cell membrane (also known as the plasma

membrane or cytoplasmic membrane) is a biological membrane that separates the interior of all cells from the outside environment. It also surrounds the inner gel-like material called protoplasm. It controls the entry and the exit of substance according to the requirements of the cell.

The cell wall is a tough, flexible but sometimes fairly rigid layer that surrounds plant cells. It is located outside the cell membrane and provides plant cells with structural support and protection.

Cytoplasm The cytoplasm comprises cytosol – the gel-like substance enclosed

within the cell membrane – and the organelles – the cell's internal sub-structures. All of the contents of the cells are contained within the cytoplasm. The cytoplasm is made up of carbohydrates, proteins, fats, minerals vitamins and about 80% water and usually colourless.

In plants, movements of the cytoplasm around vacuoles are known as cytoplasmic streaming.

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Nucleus The nucleus is the most

important part of the cell as it controls the functions and activities of the cell. It is lies in the centre of the cell but it also occupy peripheral positions.

The nucleus is bound by a nuclear membrane. The protoplasm present in the nucleus is called nucleoplasm. It has a thread-like network called chromatin. When the cell divides it condenses to form, a thread-like structure called chromosomes. The number of chromosomes in human beings is 46(23 pairs of chromosomes).

Chromosomes contain genetic

material, organized as multiple long linear DNA (deoxyribonucleic acid)molecules in complex with a large variety of proteins.

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Cell Organelles

Plastids

Mitochondrio

n

EndoplasmicReticul

um

Golgi

Apparatus

Vacuole

Ribosomes

Flagella &

Cilium

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PlastidsThe plastid  is a major organelle found in the cells of plants and algae. Plastids are the site of manufacture. They often contain pigments used in photosynthesis, and the types of pigments present can change or determine the cell's colour.

MitochondrionThe mitochondrion (plural mitochondria) is a membrane-bound organelle. These are rod shape or spherical structures. These structures are described as "cellular power plants" because they generate most of the cell's supply of adenosine triphosphate (ATP).

Endoplasmic Reticulum

The endoplasmic reticulum (ER) is a

type of organelle in the cells that forms an interconnected network of flattened. There are two types of endoplasmic reticulum, rough endoplasmic reticulum (RER) and smooth endoplasmic reticulum (SER). It works as skeletal framework for the cell.

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Golgi ApparatusThe Golgi apparatus, also known as the Golgi complex is an organelle found in the cells. It was identified in 1897 by the Italian physician Camillo Golgi. The Golgi apparatus packages proteins inside the cell before they are sent to their destination; it is important in the processing of proteins for secretion.

VacuoleA vacuole is a membrane-bound organelle which is present in all types cells. Vacuoles are essentially enclosed compartments which are filled with water containing inorganic and organic molecules. The organelle has no basic shape or size;

its structure varies according to the needs of the cell.

RibosomesThe ribosome is a large and complex molecular machine, found within all living cells, that help in protein synthesis.

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Some of the cells have small organelles on their cell membrane, which help them in transportation and collection of food. Two of them are-

FlagellumA flagellum is a lash-like appendage that protrudes from the cell body of certain cells like Euglena. The primary role of the flagellum is locomotion but it also often has function as a sensory organelle, being sensitive to chemicals and temperatures outside the cell.

Cilium A cilium is an organelle found in unicellular cells like Paramecium.

Cilia are slender protuberances that project from the much larger cell body.

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Comparison Between Plant And Animal Cells

Sr. no.

Part of a Cell Plant Cells Animal Cells

1. Cell Membrane Present Present

2. Nucleus & Nucleus Membrane

Present Present

3. Cytoplasm Present Present

4. Cell Wall Present Absent

5. Plastids Present Absent

6. Vacuole Present (Large in size)

Present (Small in size)

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Levels Of Organisation In An Organism

Cell

Tissue

Organ

Organ System

Organism

The basic unit of structure and function in living things. 

Made up of cells that are similar in structure and function and which work together to perform a specific activity.

Made up of tissues that work together to perform a specific activity. 

Groups of two or more tissues that work together to perform a specific function for the organism. 

Entire living things that can carry out all basic life processes. 

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Created ByAbhinav MauryaMail me at Mabhinav60@gmail.com