Living Cell

The cell is the basic structural and functional unit in all living organisms. Living forms vary in size but they are all made up of cells. In unicellular organisms, the cell is the organ. As an organism grow in complexity, the cells increase in number and similar cells aggregate into tissues and organs with specialized functions. The shape of the cell is often determined by its function and the size of the cell is determined by the optimum dimensions that will enable it to perform its duties more effectively.

The human body is composed of a multiple of specialized tissues which inturn consist of vast clusters of cells differentiated into specialised chemical factories which perform various biochemical reactions.

Types of cells

Two general types are recognised in nature. They are prokaryotic and eukaryotic cells.

Prokaryotic cells

Prokaryotes were the first cells to arise in biological evolution. They are very small and simple having only a single membrane. The cell membrane, is usually surrounded by a rigid cell wall.

They are devoid of nucleus and membranous organelles such as mitochondria and endoplasmic reticulum etc.

Eukaryotic cells

Eukaryotic cells are presumably derived from prokaryotes. They are much larger and much more complex than prokaryotic cells

They have nucleus and membrane bound subcellular organelles. Many of their metabolic reactions are segregated within structural compartments. The significant differences between prokaryotic and enkaryotic cells are:

Differences between prokaryotic and
enkaryotic cells
Eukaryotes Prokaryotes
Have nucleus with nuclear
membrane
Do not have nucleus
Have membrane bound
subcellular organelles such
as mitochondria, endoplasmic
reticulum and golgi complex
Do not have organelles
Have large ribosomes Have small ribosomes
Have many chromosomes
which undergo mitosis
and meiosis during cell
division
Have a single chromosome,
which consists of a single
molecule of double helical
DNA
Reproduce by sexual
division
Reproduce by asexual
division
They are present in fungi,
protozoa, most algae,
higher plants and animals
They are found in eubacteria,
the blue green algae, the
spirochetes and the
mycoplasma

The eukaryotic cell structure is composed of

(i) cell membrane

(ii) nucleus

(iii) mitochondria

(iv) endoplasmic reticulum

(v) golgi apparatus

(vi) ribosomes

(vii) lysosomes and others.

These specialised structural units are called as subcellular organnelles. Biochemistry today is increasingly concerned with the structure of cells and their organelles.

Suggested Posts

Life Cycle of Plasmodium in Man – Schizogony   There are two phases in the life cycle of malarial parasite in man.They are (1) Pre erythrocytic cycle or Exoerythrocytic cycle (in liver ce...
Earthworm – Characteristic Features Phylum Annelida Class Chaetopoda Order Oligochaeta Type Lampito mauritii   Earthworms are nocturnal animals. The...
Methods of taxonomy Phenetic method or Numerical taxonomy This method involves clustering or grouping of individuals of a taxon or several taxa. Based on overall similar...
Scientific Names – Invertebrates Scientific names of some common Invertebrate Earthworm Lampito mauritii Cockroach Periplaneta americana House fly Musca nebula ...
Monsters that are found in rivers The most terrible monsters, which can be found in fresh water.  Let us hope that in our rivers and lakes, there are no monsters. ...
Fyrose

Fyrose is one of the Authors of HourlyBook.

Related Posts
Comment ( 1 )
  1. PMT AIPMT Practice Questions – National and State Level | Hourly Book
    February 12, 2015 at 9:57 pm
    Reply

    […] In humans, the HIV virus primarily attacks which of the following types of cells? (a) Epidermal cells (b) Red blood cells (c) White blood cells (d) Neurons 2. A biologist counted […]

Leave a reply
Captcha Click on image to update the captcha .