Parts of Cell and their Functions

Parts of Cell and their Functions

Cell wall

• Generally found in plant and fungus cell.
• Freely permeable.
• It is made up of cellulose (plant) and chitin (fungus).
• It provides shape and rigidity to the cell.

Cell membrane

• It is also known as plasma membrane / cytoplasmic membrane / plasmalemma
• In animal cell it is the outer cover of the cell.
• In plant cell it is found within cell wall.
• Cell membranes contain a variety of biological molecules, notably lipids and proteins.
• The cell membrane is selectively permeable and able to regulate what enters and exits the cell, thus facilitating the transport of materials needed for survival..

Protoplasm

• Protoplasm is the living part of a cell that is surrounded by a plasma membrane.
• It is generally the whole fluid present inside plasma­membrane.
• It contains the genetic material of a cell or organism
• It plays a role in controlling the activity of the cell.
• It consists of Cytoplasm & Nucleoplasm.
  • Cytoplasm: The fluid found outside the nuclear membrane.
  • Nucleoplasm: The fluid found inside the nuclear membrane.

Mitochondria

• The mitochondrion (/ˌmaɪtəˈkɒndrɪən/,[1] plural mitochondria) is a semi autonomous double-membrane-bound organelle found in most eukaryotic organisms.
• It is called as “Powerhouse of the Cell” because in it stepwise oxidation of fuel occurs which results in release of chemical energy. This energy is stored in the form of ATP.
• Mitochondria play a vital role in the conversion of energy from food into energy for biological processes.

Endoplasmic Reticulum

• These are hollow membranous system having ribosomes (thus called Rough ER) or no ribosomes (thus called Smooth ER).
• Rough Endoplasmic Reticulum is the site of protein synthesis, while Smooth Endoplasmic Reticulum is the site of synthesis of steroids and detoxification.

Golgi Apparatus

• Also known as Golgi boy or Golgi Complex.
• It was identified in 1897 by the Italian scientist Camillo Golgi and was named after him in 1898.
• Plays important role in secretion, transportation and acrosome formation.

Plastid

• Found in cells of plants, algae, and some other eukaryotic organisms.
• Plastids were discovered and named by Ernst Haeckel.
• They often contain pigments used in photosynthesis, and the types of pigments in a plastid determine the cell’s color.
• Different kinds of Plastids :
  • Chloroplasts : green plastids for photosynthesis.
  • Rhodoplasts : red plastids found in red algae.
  • Chromoplasts  : coloured plastids for pigment synthesis and storage.
  • Leucoplasts : colourless plastids for monoterpene synthesis.
  • Amyloplasts : for starch storage and detecting gravity (for geotropism).
  • Elaioplasts : for storing fat
  • Proteinoplasts : for storing and modifying protein
  • Tannosomes : for synthesizing and producing tannins and polyphenols
• The red colour of tomatoes is due to the presence of lycopene pigment, i.e., chromophore.
• The colour of carrot is due to carotene.

Ribosomes

• It is made up of ribonucleic acid (RNA).
• The term “ribosome” was proposed by scientist Richard B. Roberts in the end of 1950s:
• takes part in protein synthesis.

Lysosome

• lysosome is a membrane-bound cell organelle that contains digestive enzymes.
• Lysosomes are involved with various cell processes.
• They break down excess or worn-out cell parts. They may be used to destroy invading viruses and bacteria.
• The enzyme found in lysosome may digest the entire cell. This is why it is also known as suicidal bag.

Chromosome

• Chromosome is threadlike structure, found in the nucleus.
• Chromosome is a long DNA molecule with part or all of the genetic material of an organism.
• Bead­like structure found on chromosome is called genes, which are made up of DNA and are the carrier of genetic information from generation ­to generation. In some viruses, RNA is the genetic material called retrovirus.
•  Eukaryotic cells possess many chromosomes.

Vacuoles

• These are non-­living reservoirs, bounded by a membrane called tonoplast.
• It stores toxic metabolic waste and helps in osmoregulation.

Nucleus

• It was discovered by Robert Brown.
• The nucleus is a membrane-bound organelle that contains genetic material (DNA) of eukaryotic organisms.
• Nucleus is rich in protein and RNA.
• Eukaryotes usually have a single nucleus, but a few cell types, such as mammalian red blood cells, have no nuclei, and a few others including osteoclasts have many.
• Among mammals only Camel and Llama’s red blood cells has nuclei.
• The main function of the cell nucleus is to control gene expression and mediate the replication of DNA during the cell cycle.
• It is the controlling centre of a cell.

Nucleic Acids

• Complex organic compound found in cell.
• These contain the genetic instructions used in the development and functioning of all known living organisms.
• There are of two types nucleic acid – DNA and RNA.
• DNA 
  • Full form Deoxyribo Nucleic Acid.
  • DNA was discovered by James D Watson and Francis Crick, who got Nobel Prize for this discovery.
  • Frederic Meischer first isolated DNA from nucleus of a cell.
  • DNA  is mainly found in nucleus. In Small amount it is also found in mitochondria and chloroplast.
  • Chemically DNA is made up of three components – Nitrogen Base, Sugar and Phosphate Group.
  • Nitrogen Bases are of two types – Purines & Pyrimidines.
  • Purines contain two type of nitrogen base – Adinine and Guanine.
  • Pyrimidines contain two type of nitrogen base – Thymine and Cytosine.
  • Functions of DNA :
    • It contains genetic information in coded form.
    • DNA synthesizes RNA.
• RNA
  • Full form Ribo Nucleic Acid.
  • RNA is a single stranded nucleic acid made up to phosphate, ribose sugar and  nitrogenous base uracil,adenine, guanine and cytosine.
  • It is found in nucleus as well as cytoplasm.
  • Function: Synthesis of protein.