Plasma Membrane
- The membrane on the cell surface that envelopes the content of a cell
- It is made up of proteins and phospholipids and is semi permeable
- It acts as a selective barrier to regulate the movement of substances like respiratory gases,nutrients and waste products in and out of the cell
Cell Wall
- It is found in plant cells only and is made up of cellulose,a tough and fibrous carbohydrate
- Its is rigit outer layer that surrounds the plasma membrane gives shape and mechanical strength to support the plant
- It has tiny pores and is permeable to all fluids in and out of the cell
Cytoplasm
- It is jelly-like matrix found between the plasma membrane and the nucleus and where the organelles are suspended
- It contains organic and inorganic substances
- It also acts as a medium for biochemical reactions in the cell
Nucleus
- It is large,dense and spherical organelle and is enclosed by a nuclear membrane
- It contains the nucleoplasm and the nucleolus which is a dark and dense spherical region
- Chromatins that carry the genetic materials in the form of DNA
- It controls all cellular activities inside the cell
Vacuoles
- A fluid-filled sac enclosed by a semi-permeable membrane called tonoplast
- The fluid called the cell sap contains water,organic acids,sugars,amino acids,mineral salts,waste materials,pigments and metabolic by-products
- In herbaceous plants,the cell sap in the vacuole prevents the plant from wilting easily
- A matured plant cell has a large vacuole whereas a young plant cell has smaller vacuoles
- In some unicellular organisms like the Amoeba sp. and Paramecium sp.,they have small vacuoles which act as food storage and also helps to regulate the water balance
Mitochondrion
- It appears as a small spherical or cylindrical shaped organelle
- It contains respiratory enzymes and is a site for cellular respiration
- Food substances such as glucose are oxidised and energy is released in the form of ATP (adenosine triphosphate)which can be readily utilised by the cell
Ribosomes
- They are compact,spherical organelles and are either attached to the surface of the rough endoplasmic reticulum or suspended freely in the cytoplasm
- Each ribisome contains 2 subunits,a large subunit and a small subunit,each consisting of the RNA(ribonucleic acid) and protein
- Ribosomes are the sites for protein synthesis
Endoplasmic Reticulum
- It is a network of folded membranes that forms interconnected tubes or sacs
- It's membrane is continuous with the nuclear membrane
- Two types:Rough endoplasmic reticulum
- The rough endoplasmic reticulum has ribosomes attached to its surface to synthesis proteins before transporting them in vesicles
- The smooth endoplasmic reticulum doesn't have ribosomes and synthesis lipids and detoxifies drugs and poisons and is also the site for metabolic reactions
Golgi Apparatus
- It consists of a stack of flattened membranous sacs
- It acts as a processing,packaging and transporting center for carbohydrates,proteins,glycoproteins and phospholipids
- Transport vesicles from the rough endoplasmic reticulum fuse with the membrane of the Golgi apparatus and empty the contents into it
- They are processed and the finished products are then repackaged in vesicles and are budded off from the Golgi apparatus
- The budded vesicles will then fuse with the plasma membrane to realese the contents outside the cell
Lysosomes
- They are small,spherical sacs surrounded by a single membrane containing hydrolatic enzymes which will then breakdown and digest complex molecules like proteins,lipids,polysaccharides and nucleic acids
- It also breakdown the old and worn out mitochondria and other organelles
- In certain unicellular organisms,it fuse with the food vacuoles to digest their contents and release the nutrients by the organisms
Centrioles
- They are small cylindrical structures that are arranged in pairs just outside the nucleus
- Its are composed of a complex arrangement of microtubules
- Its are only found in animal cells
- In cell division,they form the spindle fibres
Chloroplasts
- They are bi-convex shaped organelles and have double membrane
- They contain the green pigments,chlorophyll which capture light energy from the sun and convert it to chemical energy during photosynthesis
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