CONTENTS Organization of cell cell tissue organ Difference between plant cell and animal cell Cell structures and their functions: Plasma membrane and its functions Cell wall and its functions Cytoplasm and its functions Golgi apparatus and its functions ER and its functions Lysosomes and its functions Mitochondria and its functions Ribosomes and its functions Nucleus its function and its parts Vacuoles and its functions Difference between prokaryotic and eukaryotic cells
CellTissue – group of cellsfunctioning together.Organ – group of tissuesfunctioning together.Organ System – group of organsfunctioning together.Organism – group of organsystems functioning together.
Cell is theCELL basic structural and functional unit of life. It is the smallest unit of an organism that is classified as living, and is often called the building brick of life.
TISSUE Group of cells working together constitute a tissue.
ORGAN Group of tissue working together constitute a organ.
Animal cell Plant cell Animal cells are usually Plant cells are smaller in size. comparatively larger in Enclosed by plasma size. membrane only. Cell Plasma membrane of wall is absent. plant cells is surrounded by a thick cell wall. Plastids are absent, except in the protozoan euglena. Plastids are present.
Animal cell Plant cell Cytoplasm consists Cytoplasm peripheral, largely of smaller central space occupied vacuole. by a large vacuole. Nucleus lies in the Nucleus lies on one centre. side. Prominent and highly Contains several sub- complex Golgi bodies units of Golgi present. apparatus called dictyosomes. Animal cells possess Plant cells lack centrosome with one or centrosome and two Centrioles. Centrioles.
This is the outermost covering of the cell that separates the contents of the cell from its external environment.Plasma membrane is a living, thing, delicate, elastic, selectively permeable membrane made up of proteins and lipids and is present in both plants and animals cells.
It gives definite shape to the cell. It separates the contents of a cell from its surrounding medium. It provides mechanical barrier for the protection of the internal contents of the cell. It is selectively permeable membrane. It regulates the movement of ions in and out of the cell.
Plant cells have a rigidouter protective coveringcalled the cell wall whichlies outside the plasmamembrane. The cell wallis non-living, freelypermeable and mainlycomposed of cellulose.
It provides structural strength to the plants cells. It permits the cells of plants, fungi and bacteria to withstand very dilute external media without bursting. It gives a definite shape to the cells. Because of cell walls, plant cells can withstand much greater changes in the surrounding medium than animal cells. Cell wall protects the cells against pathogens and mechanical injury.
It is the fluid partcontent of the cellwhich occurs betweenthe plasma membraneand the nuclearenvelope. It containsvarious cell organelleswhich perform differentfunctions of the cell.
Cytoplasm helps in exchange of material between cell organelles. It acts as a store of vital chemicals such as amino acids, glucose, vitamins, ions, etc. It is the site of certain metabolic pathways such as glycolysis. Synthesis of fatty acids, nucleotides and some amino acids also take place in the cytoplasm.
It is an organelle in animalcells consisting of a set ofmembrane bound smooth,flattened cisternae stackedone above the other, largespherical vacuoles and smalland spherical fluid-filledvesicles. In the plants, Golgibodies are calleddictyosomes. The Golgiapparatus is the secretoryorganelle of the cell. It arisesfrom the membrane of thesmooth ER.
Storage, modification and packaging of products in vesicles. Formation of complex sugars from simple sugars. Secretion is the main function of Golgi complex. The secretory proteins and lipids are packed and released on the surface by exocytosis. It helps in the formation of cell plate during cell division. The Golgi apparatus is also involved in the formation of lysosomes and peroxisomes.
The endoplasmic reticulum(ER)is a large network of membrane-bound tubes and sheetsextending from outer nuclearmembrane to the plasmamembrane. It occurs in the threeforms- Cisternae, vesicles and tubules.Depending upon the presenceand absence of ribosomes on thesurface of ER, these are twotypes- RER with ribosomesattached to its surface forsynthesizing proteins.
It gives mechanical support by forming a network in the cytoplasm. ER serves as channels for the transport of materials between various regions of cytoplasm or between the cytoplasm and the nucleus. Certain enzymes present in the smooth ER fats, steroids and cholesterol. Rough ER is concerned with the transport of proteins which are synthesized by ribosomes in their in their surface.
These are membrane-boundvesicular structures found in thecytoplasm of all eukaryoticanimal cells expect mammalianRBC’s. Each lysosomes issurrounded by a singlemembrane and containspowerful digestive enzymes.These enzymes are made byRER. Lysosomes are involvedin intracellular digestion offoreign food or microbes andare called digestive bags.These are involved in autolysisof cells after their death, hencethey are also called suicidalbags. Lysosomes are a kind ofwaste disposal system of a cell.
Lysosomes destroy any foreign material which enter the cell such as bacteria and virus, thus protect the cells from infection. They help in removing dead and worn-out cell organelles by digesting them. They bring self-destruction of a cell by releasing their enzymes within the cell. Thus, they act like suicidal bags in damaged cells.
These are rod-shapedstructures present in thecytoplasm of all the eukaryotesexcept mammalian RBCs.Mitochondria are called powerhouse of the cells. They storeenergy in the form of ATPmolecules by cellularrespiration. It is a self-replicating organelles. Theycontain DNA, RNA andribosomes to carry out proteinsynthesis. Mitochondria arethe largest organelles in theanimal cells.
Mitochondria are the sites of cellular respiration. They provide energy for the vital activities of living cells. Mitochondria are able to make some of their own proteins, so they are regarded as semiautonomous organelles. They provide intermediates for synthesis of various chemicals like fatty acids, steroids, amino acid, etc.
They are dense, sphericaland granular particles, whichoccur freely in the matrix orremain attached to thesurface of the ER. These aresmallest known electronmicroscopic,ribonucleoprotein particlesfound in the cytoplasm ofboth prokaryotes andeukaryotes. Ribosomes aresites of protein synthesis andhence are called proteinfactories of the cells.
Robert brown in 1831discovered the nucleus isthe largest cell structure.It is spherical or ovalprominent structure,usually located in thecentre of the cell.Nucleus has the followingimportant parts:
Nuclear membrane: it is a double layered membrane, which separates nucleus from the cytoplasm. It has pores called nuclear pores which allow the transfer of material from inside the nucleus to the cytoplasm. Nucleolus: it is a homogeneous and granular dense fluid present inside the nucleus to the cytoplasm. Chromatin material: it consists of long, coiled network of thread-like structures. The chromatin material is made up of DNA which is responsible for storing and transmitting the hereditary information from one generation to the other. It condenses into compact rod- like bodies called chromosomes at the time of cell division. Nucleolus: it is more or less round structure found inside the nucleus. The nucleolus contains RNA and proteins.RNA is helpful in protein synthesis in the cytoplasm.
There are fluid-filled or solidfilled membrane boundspaces in cytoplasm. Inanimal cells, they are small-sized and many, but in plantcells, a single prominent verylarge vacuole occupies about50-90% of the cell volume. Inthe plant cells, vacuole isbounded by a membranecalled tonoplast. The vacuoleis filled with cell sap which isa watery solution rich inamino acids, sugars, variousorganic acids and someproteins.
DIFFERENCE BETWEEN: Prokaryotic cells Eukaryotic cells Size of the cell is Size of the cell is generally small. generally large. Nuclear region is Nuclear region is well- poorly defined due to defined and absence of nuclear membrane and known surrounded by a as nucleoid. nuclear membrane. It contains single It contains more than chromosome. one chromosome..
Nucleolus is absent. Nucleolus is present. Membrane bound cell Cell organelles such as organelles are absent. mitochondria, plastids, ER, lysosomes,etc are present. Cell division occurs by meiotic cell division. Cell division takes Centrioles are present place by budding. in animals cells. Centrioles absent. Eukaryotic cells are Prokaryotic cells are found in fungi, plant found in bacteria, blue- and animal cells. green algae.