An Overview:

Right from the time when a diploid zygote was formed, till the present, we all are just made up of 37.2 trillion microscopic and unicellular cells!

The cells cannot be seen by naked eyes; instead microscopes are needed to telescope our view of these diminutive structures.

In the modern era, there are more than two types of microscopes that are used for viewing the cells in detail. The most common type of microscope is a light microscope that can magnify the cell appearance by x1500. Another one is an electron microscope that magnifies cell appearance to x10,000,000, enabling scientists to see in greater detail.

Cell structure:

Cell membrane:

  • Present in all cells
  • Also called as plasma membrane or cell surface membrane
  • Made up of thin layer of protein and fats
  • Partially permeable
  • Inside cell membrane lies cytoplasm and other cell organelles.

Cell wall:

  • Present in plant and prokaryote cells
  • In plants, made up of cellulose
  • Cellulose forms fibres in criss-cross patterns over one other
  • Cell wall forms very strong covering to cell
  • Prevents cell from bursting

Cytoplasm:

  • Jelly like substance
  • Contains 70% water
  • Metabolic reactions of the cell take place over here
  • Harmful and useful substances diffuse in and out of cells through the cytoplasm

Nucleus:

  • Contains genetic information present in chromosomes
  • Chromosomes are made up of Deoxyribonucleic acid or DNA
  • Controls the functions of the cells and gives instructions carry them out
  • Present in both plant and animal cells and absent in a prokaryotic cell

Vacuole:

  • Vacuoles are spaces in cells containing a solution called cell sap
  • Large vacuoles are present in plant cells to store the useful products formed in photosynthesis
  • In animal cells, small vacuoles or no vacuoles at all can be present as animal cells are heterotrophic
  • Small vacuoles in animal cells often store food and water

Chloroplast:

  • Is the organelle that distinguishes between an animal and a plant cell
  • Contains a green coloured pigment known as chlorophyll
  • They are important for plant cells in the process of photosynthesis

Mitochondria:

  • Are powerhouses of cells
  • Are found in all cells except those of a prokaryote
  • In aerobic respiration, oxygen is used to release oxygen from the contents of the mitochondrion (starch in plants and glycogen in animals)

Cells containing mitochondria are-

  1. Muscle cell- to work
  2. Sperm cell- to swim in the semen
  3. Neurons- to carry electrical nerve impulses

Ribosomes:

  • Ribosomes are cell organelles that are the places where a protein is made by the synthesis of amino acids.
  • They are arranged in a network known as rough endoplasmic reticulum
  • They are found in all kinds of cells ranging from prokaryotic to eukaryotic.

The structure of a plant cell

Plant Cells

The structure of an animal cell

Animal Cells

A Comparison between a plant and animal cells:

 Plant cells  Animal cells
 Have a cellulose wall covering the cell membrane  Don’t have cell wall
 Have a cell membrane  Have a cell membrane
 Have cytoplasm  Have cytoplasm
 Have a nucleus  Have a nucleus
 Often have chloroplasts with chlorophyll in them  Chloroplasts absent in animal cells
 Often possess large vacuoles containing cell sap  Only possess small vacuoles containing food and water
 Often have starch grains  Only have glycogen granules present sometimes
 Often have a regular shape  Often irregular in shape

 

 Calculating Magnification:

 Top tip!: questions on magnification are quite common in cambridge IGCSE Biology paper 1 and paper 6 so do learn the formula in advance!

Magnification = Size of Image/Actual Size

Examples of specialized cells:

Ciliated cell : found in the trachea and bronchi, moves the mucus towards the throat.

Memory cell : found in the blood, keep antibodies ready to kill pathogens that have affected you more than once.

Root hair cell : found at the end of the plant roots are responsible for the absorption of minerals and water.

Palisade mesophyll cell : found beneath the epidermis of a leaf are specialized at photosynthesis.

Sperm and Egg cell: produced in testes and ovaries, fuse together to produce a zygote.

Nerve cell : found throughout the bodies of all organisms are responsible for the transmission of electrical nerve impulses.

Red Blood Cell  : found throughout in the blood of mammals and specialize at the transport of oxygen using the red pigment haemoglobin.

What you are made up of:

  • Cells : eg: ciliated cells, root hair cells etc.
  • Tissues : are are group of cells with the same function and of the same type. eg: epidermis tissue, palisade tissue, muscle tissue etc.
  • Organs: are groups of tissues. eg: heart, lungs, trachea, leaf, fruit, flower, root etc.
  • Organ systems: are made from groups of organs. eg: digestive system, respiratory system, circulatory system, reproductive system, nervous system etc.
  • Organism: is what the end result is with several organ systems that make them up! Eg: you, tiger, snake, scorpion etc.

External Links

  1. Plant Cell
  2. Eukaryote Cell
  3. Cell Organelles

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  • Suhaib Dada

    This is amazing, Thank You Very Much 🙂

    • Laurene

      True

  • Leela de Paula

    “mitochondria” – oxygen is used to release oxygen from the contents of the mitochondrion (starch in plants and glycogen in animals). Doesn’t make sense. Most probably ENERGY being released with the usage of oxygen is the correct term.

  • Laurene

    Thank you very much to all…..God bless…Many thanks

  • Laurene

    Thank you by the way