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Chapter 8 – Cell — Structure and Functions

The following Topics and Sub-Topics are covered in this chapter and are available on MSVgo:

Introduction

These building blocks which work together in a single body and assume different functions to form various body parts are called cells. In biology, cells can be defined as small membrane-bound units that can replicate themselves and perform complex functions to carry out life processes. The study of the structure and functions of the cell is called Cell Biology.

The history of cells can be dated back to 1665 when Robert Hooke observed a thin slice of cork under a primitive microscope and found something amazing. He saw that the cork was made up of several tiny pores, which he named “cells”. Soon after Hooke, Dutch scientist, Leeuwenhoek (1674) by using his advanced microscope detected other minuscule organisms – bacteria and protozoa and named them “animalcules”.

German scientists Theodor Schwann (1839) and Matties Schleiden (1838) made another remarkable discovery by identifying the key differences between plant and animal cells. They were also the ones who proposed the classical cell theory. Rudolf Virchow (1858) further expanded this theory and gave the correct interpretation of cell formation. Their observations can be summed up as follows:

  1. All organisms are made up of cells.
  2. The cell is the structural and functional unit of all living things.
  3. All cells come from pre-existing cells that have multiplied.

The rapid improvement in technology over the decades has led to new and advanced discoveries about cells. The modern cell theory is a drastic improvement over the classical cell theory and has three major additions too:1. During cell division the DNA is passed from cell to cell 

  1. The structural and chemical composition of cells is the same of all organisms within the same species
  2. Cells are characterized by the presence of energy flow (metabolism) within them.

The cellular structure of a living organism can be classified into two as follows:

  • Prokaryotic Cells – The Prokaryotes are the most ancient and incomplete cells. They have a basic cell structure but lack nuclear membrane around their genetic substance (DNA). The DNA bundles together in a region are called the nucleoid.

Eg –  Bacteria and Archaebacteria

  • Eukaryotic Cells – These are advanced and complete cells that contain membrane bound nuclei. These cells also have cell organelles which carry out a variety of functions such as energy production and protein synthesis.

Eg – Plants, Animals, etc.

Cell Shape

Cells  are basically round, spherical, or elongated but their ultimate shape is determined by the functions they perform. For example a Red Blood Cell is round, a nerve cell is long or a muscle cell is cylindrical. In unicellular organisms the plasma membrane maintains the shape. However, in multicellular organsims along with the rigidity of plasma membrane, functions of the cell, and mechanical action exerted by adjoining cells determine the shape of the cell.

Cell Number

Although every living organism is made up of cells, the number of cells may vary significantly. On the basis of number of cells, organisms can be divided into two as follows:

  • Unicellular Organisms – Unicellular organisms such as yeast, bacteria, etc., contain only one cell which is capable of performing all the functions needed by the organism.
  • Multicellular Organisms – Multicellular organisms such as humans, animals, etc., are made up of more than one cell to perform various complex and specialized functions.

Cell Size

Cells vary a great deal in size, from a millimetre to a nanometre, with plant cells being larger than animal cells. The size of a cell is related to its function.

Parts of the Cell

 Cell, the smallest level of organization of the human body, can do several complex functions, to make advanced activities possible for lifeforms. Let’s go through the structure of a cell:

  1. Cell Membrane or Plasma Membrane – A cell membrane is a very thin layer of protein and fats. It is very important to the cells because it separates the cell from its external environment. It is said to be selectively permeable, which means that it will let some substances through but not others. It performs certain physical activities such as Diffusion and Osmosis for the intake of substances.
  2. Cell wall – A plant cell is surrounded by a cell wall that is made up of cellulose. It helps to protect and support the cell. The cell wall is said to be fully permeable because the spaces between these fibres permit large molecules to pass through it. The presence of the wall in plant cells prevents them from bursting even when the cell absorbs a lot of water and swells.
  3. Nucleus – The nucleus is known as the ‘control centre’ of the cell. The nucleus contains chromosomes where the genetic information is stored. The nucleus plays a central role in cellular reproduction and determines the way the cell will develop.
  4. Cytoplasm – Cytoplasm is the fluid content inside the plasma membrane. It contains a variety of cell organelles and many different metabolic reactions take place in the Cytoplasm. These cell organelles include the following:
  • Endoplasmic Reticulum (ER) – The ER functions as a transporter of proteins within and outside the cell and even plays a crucial role in the biochemical activities of the cell. There are two types of ER – Rough Endoplasmic Reticulum and Smooth Endoplasmic Reticulum.
  • Golgi Apparatus – They synthesize glycoproteins and pack proteins for export from the cell. 
  • Lysosomes – Known as the “suicide bags” of a cell, Lysosomes contain digestive enzymes and keep the cell clean by digesting unwanted materials and worn-out organelles.
  • Mitochondria – Regarded as the “powerhouse of a cell”, Mitochondria produces Adenosine triphosphate (ATP), which gives the energy required for various chemical activities.
  • Plastids – Plastids are found only in plant cells and are of two types – Chromoplasts and Leucoplasts. Chromoplasts help in photosynthesis and Leucoplasts store starch, oil, and protein granules. 
  • Vacuoles – Vacuoles store proteins, organic acids, sugar, salts, pigments, etc which are necessary for life. Surrounded by a membrane called the tonoplast, it controls the exchange of material between vacuoles and the cytoplasm.

Both plants and animals are structurally similar as they are eukaryotic cells, i.e, they have a clearly defined nucleus. However, a few structural and functional differences also exist. Here is a comparison between Plant cell and Animal cell.

BasisPlant CellAnimal Cell
Size and shapePlant cell size varies from 10 to 1000 micrometres and has a regular shape.Animal cell size varies from 10 to 30 micrometres and has an irregular shape.
Cell WallPresentAbsent
Plasma MembranePresentAbsent
CytoplasmPresentPresent
RibosomesPresentPresent
LysosomesAbsentPresent
NucleusPresentPresent
PlastidsPresentAbsent
VacuolesLarge vacuoles containing cell sapSmall vacuoles

What are the 5 cell structures?

All activities inside the cell and interaction of the cell are possible due to these five structures in the cell- Plasma Membrane, Cell Wall, Nucleus, Cytoplasm, and Cell Organelles.

What are the 7 functions of a cell?

The seven functions of a cell include – Movement, Conductivity, Metabolic Absorption, Secretion, Excretion, Respiration, and Reproduction.

What is the basic structure of a cell?

A cell structure consists basically of three parts – Cell Membrane which protects the cell from the external environment, Nucleus which is the control unit of the cell, and Cytoplasm is the fluid content of the cell.

What are the basic functions of a cell?

The most basic and necessary functions of the cell include nutrition uptake from food, facilitating growth, reproduction, excretion, and reacting to external changes.

What are the four basic cell structures?

The four basic cell structure are as follows:

  1. Cell Membrane – separates the cell from its external environment.
  2. Nucleus – contains DNA information.
  3. Cytoplasm – fluid content inside the cell membrane which contains all the cell organelles.
  4. Cell Wall – protective and supportive layer around the plant cell.

What are the most important cell structures?

Nucleus, the “control centre” of the cell, is most important because it stores genetic information and coordinates other important cell functions such as cell division, reproduction, growth etc.

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This was a brief summary about the cell, its structure, and its functions. It is imperative to study aspects of a cell to understand how living organisms exist and their body functions happen.

High School Physics

  • Alternating Current
  • Atoms
  • Communication Systems
  • Current Electricity
  • Dual nature of Radiation and Matter
  • Electric Charges and Fields
  • Electricity
  • Electromagnetic Induction
  • Electromagnetic Waves
  • Electron Beams and Radioactivity
  • Electrons and Photons
  • Electrostatic Potential and Capacitance
  • Fluid Pressure
  • Force and Acceleration
  • Force And Laws Of Motion
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  • Kinetic Theory
  • Law of motion
  • Light – Reflection And Refraction
  • Magnetic Effects Of Electric Current
  • Magnetism and Matter
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  • Physical world
  • Ray optics and optical instruments
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  • Sources Of Energy
  • Specific and Latent Heats
  • Spherical Mirrors
  • Static Electricity
  • Systems of Particles and Rotational motion
  • Thermal properties of matter
  • Thermodynamics
  • Units and Measurement
  • Vectors, Scalar Quantities and Elementary Calculus
  • Wave Optics
  • Waves
  • Work, Power and Energy

High School Chemistry

  • Acids, Bases and Salts
  • Alcohols, Phenols and Ethers
  • Aldehydes, Ketones and Carboxylic Acids
  • Aliphatic and Aromatic Hydrocarbons
  • Alkyl and Aryl Halides
  • Amines
  • Analytical Chemistry 
  • Atomic Structure
  • Atoms And Molecules
  • Basic concepts of Chemistry
  • Biomolecules
  • Carbon And Its Compounds
  • Carboxylic acids and Acid Derivatives
  • Chemical Bonding and Molecular Structures
  • Chemical Energetics
  • Chemical Equilibria
  • Chemical Kinetics
  • Chemical Reactions And Equations
  • Chemical Reactions and Their Mechanisms
  • Chemistry in Everyday Life
  • Chemistry of p-Block elements
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  • Classification of Elements
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  • Haloalkanes and Haloarenes
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  • Ionic equilibria
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  • Periodic Classification of Elements
  • Physical and Chemical Changes
  • Physical and Chemical Properties of Water
  • Polymers
  • Preparation, Properties and Uses of Compounds
  • Principles and Processes of Isolation of Elements
  • Redox Reactions
  • Relative Molecular Mass and Mole
  • States of Matter
  • Structure Of The Atom
  • Study of Compounds
  • Study of Gas Laws
  • Study of Representative Elements
  • Surface Chemistry
  • The d-block and f-block elements
  • The Gaseous State
  • The p-Block Elements
  • The Periodic Table
  • The s-Block Elements
  • The Solid State
  • Thermodynamics

High School Biology

  • Absorption and Movement of Water in Plants
  • Adolescent Issues
  • Anatomy of Flowering Plants
  • Animal Kingdom
  • Bacteria and Fungi-Friends and Foe
  • Biodiversity and Conservation
  • Biofertilizers
  • Biological Classification
  • Biomedical Engineering
  • Biomolecules
  • Biotechnology and its Applications
  • Biotic Community
  • Body Fluids and Circulation
  • Breathing and Exchange of Gases
  • Cell – Unit of Life
  • Cell Cycle and Cell Division
  • Cell Division and Structure of Chromosomes
  • Cell Reproduction
  • Cellular Respiration
  • Chemical Coordination and Integration
  • Circulation
  • Control And Coordination
  • Crop Improvement
  • Digestion and Absorption
  • Diversity In Living Organisms
  • Ecosystem
  • Environmental Issues
  • Excretory Products and their Elimination
  • Flowering Plants
  • Genes and Chromosomes
  • Health and Diseases
  • Health and Its Significance
  • Heredity And Evolution
  • Heredity and Variation
  • How Do Organisms Reproduce?
  • Human Diseases
  • Human Eye And Colourful World
  • Human Health and Disease
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  • Kingdom Fungi
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  • Life Processes
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  • Microbes in Human Welfare
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  • Molecular Basis of Inheritance
  • Morphology of Flowering Plants
  • Neural Control And Coordination
  • Nutrition in Human Beings
  • Organism and Population
  • Photosynthesis
  • Photosynthesis in Higher Plants
  • Plant Growth and Development
  • Plant Kingdom
  • Pollination and Fertilization
  • Pollution; Sources and its effects
  • Principles of Inheritance and Variation
  • Reproduction and Development in Angiosperms
  • Reproduction in Organisms
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  • Respiration in Human Beings
  • Respiration in Plants
  • Respiratory System
  • Sexual Reproduction in Flowering Plants
  • Strategies for Enhancement in Food Production
  • Structural Organisation in Animals
  • Structural Organisation of the Cell
  • The Endocrine System
  • The Fundamental Unit Of Life
  • The Living World
  • The Nervous System and Sense Organs
  • Tissues
  • Transpiration
  • Transport in Plants

High School Math

  • Algebra – Arithmatic Progressions
  • Algebra – Complex Numbers and Quadratic Equations
  • Algebra – Linear Inequalities
  • Algebra – Pair of Linear Equations in Two Variables
  • Algebra – Polynomials
  • Algebra – Principle of Mathematical Induction
  • Algebra – Quadratic Equations
  • Binomial Theorem
  • Calculus – Applications of Derivatives
  • Calculus – Applications of the Integrals
  • Calculus – Continuity and Differentiability
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  • Geometry – Area
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  • Geometry – Introduction to Euclid’s Geometry
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  • Geometry – Straight Lines
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  • Linear Programming
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  • Mensuration – Areas
  • Mensuration – Surface Areas and Volumes
  • Number Systems
  • Number Systems – Real Numbers
  • Permutations and Combinations
  • Probability
  • Sequence and Series
  • Sets and Functions
  • Statistics 
  • Trignometry – Height and Distance
  • Trignometry – Identities
  • Trignometry – Introduction

Middle School Science

  • Acids, Bases And Salts
  • Air and Its Constituents
  • Basic Biology
  • Body Movements
  • Carbon and Its Compounds
  • Cell – Structure And Functions
  • Changes Around Us
  • Chemical Effects Of Electric Current
  • Chemistry in Your Life
  • Coal And Petroleum
  • Combustion And Flame
  • Components Of Food
  • Conservation Of Plants And Animals
  • Crop Production And Management
  • Electric Current And Its Effects
  • Electricity And Circuits
  • Elements and Compounds
  • Fibre To Fabric
  • Food production and management
  • Force And Pressure
  • Forests: Our Lifeline
  • Friction
  • Fun With Magnets
  • Garbage In, Garbage Out
  • Getting To Know Plants
  • Health and Hygiene
  • Heat
  • Hydrogen
  • Life Processes: Nutrition in Animals and Plants
  • Light, Shadows And Reflections
  • Materials: Metals And Non-Metals
  • Matter and Its States
  • Metals and Non-metals
  • Micro Organisms: Friend And Foe
  • Motion And Measurement Of Distances
  • Motion And Time
  • Nutrition In Animals
  • Nutrition In Plants
  • Organization in Living Things
  • Our Environment
  • Physical And Chemical Changes
  • Pollution and conservation
  • Pollution Of Air And Water
  • Reaching The Age Of Adolescence
  • Reproduction In Animals
  • Reproduction In Plants
  • Respiration In Organisms
  • Rocks and Minerals
  • Separation Of Substances
  • Simple Machines
  • Soil
  • Some Natural Phenomena
  • Sorting Materials Into Groups
  • Sound
  • Stars And The Solar System
  • Structure of Atom
  • Synthetic Fibers And Plastics
  • The Living Organisms And Their Surroundings
  • Transfer of Heat
  • Transformation of Substances
  • Transportation In Animals And Plants
  • Universe
  • Waste-water Story
  • Water: A Precious Resource
  • Weather, Climate And Adaptations Of Animals To Climate
  • Winds, Storms And Cyclones

Middle School Math

  • Addition
  • Area and Its Boundary
  • Boxes and Sketches
  • Data Handling
  • Fun With Numbers
  • Heavy and Light
  • How Many
  • Long And Short
  • Mapping
  • Measurement
  • Money
  • Multiplication and Factors
  • Multiply and Divide
  • Numbers
  • Parts and Wholes
  • Pattern Recognition
  • Patterns
  • Play With Patterns
  • Rupees And Paise
  • Shapes And Angles
  • Shapes And Designs
  • Shapes and Space
  • Similarity
  • Smart Charts
  • Squares
  • Subtraction
  • Tables And Shares
  • Tenths and Hundredths
  • Time
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