Eukaryotes Cells, Definition ,Functions ,Structure ,Type and notes for NEET

The eukaryotes include all the protists, plants, animals and fungi. In eukaryotic cells there is an extensive compartmentalisation of cytoplasm through the presence of membrane bound organelles. Eukaryotic cells possess an organised nucleus with a nuclear envelope. In addition, eukaryotic cells have a variety of complex locomotory and cytoskeletal structures. Their genetic material is organised into chromosomes. All eukaryotic cells are not identical. Plant and animal cells are different as the former possess cell walls, plastids and a large central vacuole which are absent in animal cells. On the other hand, animal cells have centrioles which are absent in almost all plant cells.

Eukaryotic Cell

Cell wall

 Cell wall found in all plants except mycoplasma.It  is not found in gametes of plant cells. It is rigid, hard, non living, protective covering, permeable.cell wall is present in plant,algae,fungi, bacteria.In higher plants cell is present made up of cellulose,hemicellulose ,pectin, lignin.In algae it is made up of cellulose ,SiO2, CaCO3,galactose,mannose.In fungi it is made up of chitin, It is called fungal cellulose which is nitrogen-polysaccharide.

Chitin is the second largest substance on earth.Hemicellulose is heteropolysaccharide because it is made up of arabinose galactose.Pectin is heteropolysaccharide ,containing nitrogen.

Lamella: when two cells are formed the first layer formed is called middle lamella that joins two cells. It is a cementing layer between two cells .It is formed by fragments of golgi bodies and endoplasmic reticulum. It contains Mg and Ca is more fundamentally Ca pectate is considered plant cement.when two adjacent cells are there then outermost layer is middle lamella. When a cell is singly present, the outermost layer is the primary cell wall. The outer layer of the epidermal cell or surface cell is the primary cell wall.

Primary cell wall : It is formed inside the middle lamella ,and thin layer growth takes place because the cell will mature so the primary cell wall grows. The primary cell increases in all duration when the cell increases its life. it's do not have secondary growth deposition .primary cell wall also known as universal cell wall meristematic cells have only two layer i.e.primary cell wall and lamella,it has particular protein called expansion.This protein help in losing microfibrils so deposition of hemicellulose take place and so cell wall expand.Expansin protein have loosing factor or growth factor.

Secondary cell wall:Found when division are not found i.e. in xylem tracheids collenchyma , sclerenchyma, it is harder,thicker it is main load bearing wall.In secondary cell cellulose microfibrils are more than hemicellulase. It is multilayered layer are termed as s1,s2,s3 cellulose microfibrils are arranged different name are given as s1, s2,s3...secondary cell wall is not universal.

 

Tertiary cell wall : found in tracheids of gymnosperm. These are dead cells. because protoplasm gets reduced. hemicellulose is more.cellulose is negligible.

Intussusception: deposition of particles in the form of granules.primary cell wall formation is by intussusception.

A Position/accretion: when deposition is in the form of a compact layer . The layer is formed due to cellulose secondary cell wall formation by both. 

Plasmodesmata : Cytoplasmic or protoplasmic connection between two cells . They are present in the living cell. It provides the living path or symplast non-living - apoplast.Plasmodesmata provides symplastic path. endoplasmic means endo- inside , plasmic - protoplasm ,reticulum -net.endoplasmic reticulum can be connect from cell to other

Suberization cork lamella has maximum suberin deposition suberin is of wax nature. cutin is formed in xerophytes . In xerophytes epidermal cell wall has deposition of cutin in the form of layer that form shielding to stomata that prevent transpiration.cutin is also waxy in nature.

Example: tomato has deposition of cutin on its surface which does not dissolve in water.

Function of cell wall 

1. Provide shape 
2. Provide protection 
3.Provide connectivity through pits and plasmodesmata.
4. Act as a barrier 
5.Regulating and controlling loss of water.

Plasma or cell membrane:

First observed by Schwann. Nageli /kramer.power observed that inside the cell or organelles nature.he used the term bio-membrane or plasma membrane or plasmalemma. Plasma membrane is very thick ,elastic selectively permeable, living membrane present on outer layer on animal cell and below cell wall in plant cell.it is made up of lipid,protein,and carbohydrates.

Plasma membrane

Selectively permeable : Higher selectively permeable inclined towards living property membrane choose the particle selectively and select the particle as per requirement by the cell made up of lipid protein and carbohydrate.

Semi-permeable :Membrane which allows certain solid particles across it. its can be non-living made up of lipid protein and carbohydrates. 

Cytoplasm

 

'Cytoplasm' word given by straiburges.it is jilly like colloidal semi fluid material present ouside the nuclear envelope and inside plasma membrane 

cytoplasm is two part : 

Hyloplasm- without any structure .also called ground plasm also called cytrol

protoplasm that contain different organelles and inclusions

Nucleoplasm 

A matrix enclosed by a nuclear envelope is called nucleoplasm.(nuclear has double membrane so called envelop)

cytoplasm + nucleoplasm=protoplasm   

Protoplast 

Organelles surrounded by plasma membranes are called protoplasts. protoplasm include solid organelles but protoplasm is only liquid part organelles are the part of protoplast. all together are called protoplasm of a cell including cellular part organelles nucleus etc.

Organelles living as golgi bodies , mitochondria ,lysosome parts of cells that are chemically active organelles are also called protoplasmic bodies. cillia ,flagella organelles are metabolically active, they have definite structure and composition chemicals have definite functions. 

vacuole are organelles because they take part in living activity organelles are developed just after cytokinesis i.e just after the formation of daughter cells organelles are also called organoids. inclusion not metabolically active, on living , they do not have definite position and shape.they are the result of metabolic activity.

example food vacuole ,gas vacuole hormones ,pigment , granules etc

Endomembrane system

In certain eukaryotic cells ,membranous structures work together as coordination .These  are called endomembrane systems .This coordination takes place in certain cases; those membrane structures are called members of endo membranous systems.

 animal cell contain E.R, golgi bodies ,lysosomes work together

Plant cells contain E.R , golgi bodies ,lysosomes and vacuoles work together.

Endoplasmic reticulum 

Network of tubules inside the cytoplasm. The name was given by a porter. endoplasmic reticulum are absent in germ cell, mature mammalian and RBC

endoplasmic reticulum is made up of cisternae, vesicle and tubules 

Cirternac: are flat tubular that are unbranched but interconnected contain 80 s ribosomes and membrane . They are placed like stacks or pulled over one another .They are related to protein synthesis because they have 80 ribosomes.

They are found in cells that are related to protein synthesis

Vesicles: small, spherical and membrane structure rich in 80 ribosomes. 

Tubules: are flat ,tubular ,membrane ,branched structure ,not interconnected and can be found freely or associated with cisternas.

Ribosomes are not found in tubules so tubules are found in those cells where lipid is synthesis not in protein synthesis cells. inner side of endoplasmic reticulum interlaminar ,

outer side of endoplasmic reticulum extraluminal

Endoplasmic reticulum are two type 

Rough endoplasmic reticulum : ribosomes are present on the surface 80s ribosomes composed of cisternae and vesicles synthesis of protein.

Smooth endoplasmic reticulum : It don't have ribosomes composed of tubules synthesis of lipid hormones.Ribophorin protein attached ribosomes to cisternac .ribophorin are found in rough endoplasmic reticulum.smooth are abundant in liver cells.rough endoplasmic reticulum are abundant in pancreatic cells insulin glucagon are synthesised in pancreatic cells.

Modification of endoplasmic reticulum

1.sacoplasmic endoplasmic reticulum

These are found in smooth and striated muscles i.e.they are found in cardiac and skeletal muscles. It helps in muscle contraction and relaxation. They store Ca+. they help in calcium storage 

2.Ergastoplasm: endoplasmic reticulum 

These are found in nerves cell they are rough endoplasmic reticulum because they contain parallel stacks of cisternae and cisternac are rich in ribosomes they are also called nissl granule related to protein synthesis.these cisternac are rich in 80s ribosome.

myeloid bodies ; found on the retina of eyes. (epithelial cells of eyes ) These are sarcoplasmic smooth endoplasmic reticulum. They are light sensitive i.e they help in pigment  transfer.iodopsin and rhodopsin is transferred by myeloid bodies with the help of vitamin A.

function of endoplasmic reticulum

1.protein synthesis: 

Endoplasmic reticulum receives the polypeptide chain and help following it peptide are folded then convertain into chain storage golgi bodies break the protein 

Protein synthesis in three steps 

a. Peptide are folded 

b.Storage/ quality control 

c. Converted to chain

2.lipid synthesis 

Golgi bodies and endoplasmic bodies together form a system called endoplasmic reticulum golgi intermediate compartment. This compartment is called ERGIC.this compartment help in lipid synthesis smooth endoplasmic reticulum is involved in this.

3.Transportation :

Intracellular within the cells endoplasmic to golgi bodies 

extracellular :material exchange between extracellular fluid and cells 

intercellular: between two cells 

4.Surface area:

 It provides surrounding in the cell 200 metabolic activities that take place in cells placed in cells endoplasmic reticulum scattered in the cell which increase surface area.

toxins that destroy metabolic activity

5.Glycogen metabolism

Excess of glucose converted to glycogen conversion of glucose into glycogen is called glycogen is.this is done by insulin. This is done by insulin; this glycogen is stored in the liver endoplasmic reticulum to help in glycogen synthesis.

During the requirement of energy glucose is provided by liver diabetic people cannot store glucose in their lies glucose is not stored in the liver so diabetic people are less energetic.glycogen by glucose is called glycogenolysis.This is helped by endoplasmic reticulum.

6.Detoxification 

medicines contain chemical bacterials infection poison inside the body's destruction of composition of toxins is called detoxification.

7.spherosomes:

These are formed by smooth endoplasmic reticulum small pieces of tubules is spherosomes.they help in synthesis.

8.nuclear membrane formation 

At the time prophase endoplasmic reticulum is scattered in the cells, the nuclear membrane is reformed in trlrphase by the pieces of endoplasmic reticulum and nuclear membrane.

Arrangement of phragmosome pieces of endoplasmic reticulum and nuclear membrane is called a cell plate. if Ca+ deposit then middle lamella.

Golgi Bodies 

Observed by Camillo Golgi observed in owl nerve cell and named as interrectculate apparatus.

golgi bodies are also called golgi complex/ golgi apparatus ideosomes /dictyosomes. It is a membrane of the endomembrane system .It is a membrane present in a eukaryotic cell. It is absent in RBC, bryophyte, phelon, sieves tube, spermatozoa and pteridophyta.golgi bodies are maximum in the living cell; they can be one or many.

golgi bodies

Whenever golgi bodies are found cytoplasmic organelles are not found .This zone is called zone of exclusion this part has some distinctive feature.golgi bodies form an extensive transport system with endoplasmic reticulum which deposit protein to cellular organelles. its receives large no. of vesicles from endoplasmic reticulum so. no organ can develop around golgi bodies.

Three component of golgi body

1. cisternac : sac like flat, membrane unbranched,they have polarity ,inter connected.

2.ploarity : one part convex and other concave,convex part is towards nuclus called as cishase /proximal phase /concave towards plasma membrane away from nucleus called distal phase transphase because it help in transformaton of material maturation phase because material gets mature material is receive from cis phase entry side concave also called exit side.

3. Tubules: Branched interconnect mainly found in peripheral region.plasma membrane when lost during exocytosis and endocytosis repareby golgi bodies.

Function of golgi golgi body :

Protein receiving > chemically treated > packaging >Transferred.golgi body in carbohydrate synthesis except starch and glycogen . it is help in synthesis of lysosome formation .help in cell plate formation .also help in acrosome formation (head of sperm , ovum wall penetrated by golgi body)and help in vitellogenesis (vital is the membrane formed on york )it direct the transportation of material coming from nucleus.direction or controller of traffic cell

Vacuole 

These are membrane bounded vesicles ,comparatively larger in size than lysosome .its containing matrix is non living tonoplast is like plasma membrane but not plasma membrane because it encloses non living substance.it is semi permeable.

Type of vacuole on the nature and basis of content

Vacuole or sap vacuole:

 Most frequently found in plant cells not well developed in animals cells or absent.meristematic cells also do not have sap or vacuoles.well developed in permanent tissue of plants and occupy 70%to 90% of cell space so nucleus shifted toward periperly.so it is called as central vacuole.

The membrane is called tonoplast .Matrix is non living mainly composed of water minerals ,salt , excretory products.

Also contain soluble pigment pigment also as anthocrol (yellow).conduction by storing water and collect excretory product.help in excretion it collect all the toxic substance inside 

Contractile vacuole :

In some membrane of protists like amoeba freshwater animals contractile vacuole is present which help in osmoregulation and excretion concentration of cytoplasmic is more than concentration of fresh water so water enters into cytoplasm so body of amoeba will burnt .when water enters into cytoplasm and vacuole some near to plasma membrane and burst release extra water .This contractile vacuole contract and relax and when it become very large then it burst near cell membrane 

vacoule

Food vacuole :

In lower organisms like concentrated protozoa etc food comes through endocytosis and those food materials are reserved in the form of vacuoles.these vacuoles will be hydrolysed by enzymes so the residual matter will be removed by exocytosis.

Gas vacuole:

As a result of metabolic activities gas is produced and several gas vacuoles combine to form large gas vacuoles. This large vacuole is surrounded by a proteinaceous membrane.

Lysosome 

These are membrane bound vesicular structures formed by the process of packaging in the golgi apparatus. The isolated lysosomal vesicles have been found to be very rich in almost all types of hydrolytic enzymes (hydrolases – lipases, proteases, carbohydrases) optimally active at the acidic pH. These enzymes are capable of digesting carbohydrates, proteins, lipids and nucleic acids.

Mitochondria 

They are double membrane disc shaped structures related to ATP synthesis known as powerhouse of the cell.observed first in voluntary muscle of insects by Kallikas .Attman called them as bioplast. Benda as they look like thread he called them as mitochondria.Present in all eukaryotic cell because they are double membranous .absent in mature RBCs  

The no. of mitochondria in a cell depends on the metabolic activities and size of cell.cell that have more working capacity then mitochondria will be more .A dormant seed has less mitochondria and germinating seed has move mitrochoridia .

The fight muscles of birds have maximum mitochondria and in cilia and flagella the no. is maximum because they are in continuous motion.Mitochondria also called ATP factory powerhouse of cell cell furnace ATP mill , cell within the cell. It is autosomes i.e. universal energy independent .Chloroplast is not called within the cell. because it is not universal it is energy dependent.

Outer membrane :smooth rich in protein and phospholipid but less protein in comparison to inner membrane has more pories . Protein is less and pories are more in it . The particles that are found are called subunits of parson.These are rich porins .Particles that are found on the outer side similar particles are found inside called ferdinand particles. Ferdinand particle synonyms to parson particle . if the outer membrane present is called mitoplast.

Inner membrane :certain infolding which are finger-like called cristae . contain more protein and less permeable.it has two phases, first is c-phase and second is m-phase .Small particles are found called oxysomes.

They have two chambers.

Primitrochondrial: it is the space between two membranes filled with aqueous matrix that contain pyruvic oxidising enzymet. It is the space that separates both the membranes .Inner chamber :contain matrix ,cristae ,oxysomes .

Cristae: infolding no will be more of cristae in mitochondria will more active .it increase ethe physiological surface. inner surface or face contain some stalked structure .these stalked structure are called oxysomes are elementary particle.also called f1 particle or moran particles i.e. fm pariticle ,also called Atp synthase.

Each oxysome is divided into 3 part :

1. base -embedded in inner membrane 

2 . atp synthase enzyme is present in head 

3. stalk

Matrix :

contain circular naked DNA , double stranded DNA,70s ribosomes contain enzymes for kreb cycle lipid synthesis, protein synthesis for amino acid synthesis have minerals and water.

Mitochondria is autonomous:

because it has its own DNA RNA protein synthesis apparatus .it is semi autonomous because it can synthesis some of the enzyme and some of them are synthesised by nucleus have more guanine and cytosine as compared to admin 1 % of total cell

Biogenesis :

origin of mitochondria : when a cell divides into two then binary fission does not take place it originated from parental cells.it not deniro newly born. 

Scientists say that there are similarities between BGA and mitochondria because both have 70s and naked DNA and are formed by binary fission. Scientists say that mitochondria originated from BGA.

Plastids

Generally plastids refer to chloroplast plastids are membrane identity that is present in some alge euglonoids and plants these plastids are involved in storage and synthesis of organic compounds.

Function of plastids

Attraction of insects for pollination. storage of food .balancing of CO2 and O2

Three type of plastids are 

1. chromoplast 

2.leucoplast 

3. chloroplast 

The first cell to develop is meristematic cells in plants; plastids develop from meristematic cells in meristematic cells; small vesicles that are colourless are called proplastids or proto-plastids.

leucoplast can be directly converted into chloroplast.Chromoplast can never converted into chloroplast and leucoplast.the genetic material of all three is similar as well as origin sothey inter converted but chromoplast is not interconvertible.

1. chromoplast:

coloured pigment containing plastids. carotenoid cluster of coloured pigment .It is a long chain of hydrocarbons.

Mainly carotenoids are found and chlorophyll present in very less amounts.

carotenoids protect the chlorophyll molecule from chloroplast (solar radiation). 

carotenoids are mainly composed of carotene and xanthophyll.All are fat soluble not water soluble because they are hydrocarbon.

Example: lycopene found in red chillies and tomatoes.

Coloured pigments are found in petals i.e. chromoplast is present.similar pericarp is present in fruit is made up of chromoplast.

These coloured pigments are also present in leaves and roots.carotenoids are helpful in pollination.

2.Leucoplast:

It is colourless pigment . mainly found on unexposed parts of plants such as root and seed.main function is storage of food .Food like carbohydrate ,protein lipids

3.Chloroplast:

Most important organelle on earth . plastids that are involved in photosynthesis.plastid that trap solar energy and convert it into chemical energy and convert it into chemical energy and conscience in the form of food .

Every organism directly or indirectly depends on chloroplast.

These are double membrane oval or spherical plastids in higher plants .Involved in trapping solar energy. Photosynthesis is an anabolic process. photosynthesis is the only factor that controls the CO2 concentration into the atm.

Structure of chloroplast

Envelope double membrane structure membranes are made up of lipoprotein. Both membranes are smooth in mitrochorida distalare present.outer protein contain less protein more permeable similar inner membrane more protein less permeable no. c and m phase space between outer and inner membrane periplasmic space is present./

Plastids

Thylakoid  

 membranous structure flattened ,sac like stacked over one over another.when chloroplast get mature inner membrane from thylakoid cavity of thylakoid is called lumen .two connected thylakoid inter granum thylakoid small structure found inside thylakoid membrane called quantasome . A quantasome is the place where solar energy is trapped so it is called PSU ( photosynthesis unit ) each quantasome contains 230 -400 molecules of different pigment and chlorophyll.

Cytoskeleton 

In the cell some filament or fibrous and globular or tubules proteinaceous network is present .This network of protein is called cytoskeleton. This network is meant for technical support ,it helps in intracellular transport and helps in orientation of cellular organelles to maintain shape of the cells.

Division of Cytoskeleton 

1. Microtubules 

Made up of protein tubulin.extensive network in cytoplasm .made up of filament of indefinite length these filament are cylindrical unbranched.help in spindle formaton.help in formation of centrioles and basal granules formed basal. basal granule is also called blepharoplasty .microtubules help in movement of chromosome during anaphase

2.Microfilament

They are very thin of filamentous protein actin and unbranched. Actin is the main filament protein .This protein works with myosin of muscle for contraction of muscle so they are also called myofilament.

Ribosomes 

Ribosome

Discovered  by george palade so called palade particles .small dense granule or particular they are done because they do not have matrix.Without membrane.related to protein synthesis .smallest cellular organelles .they are smallest they are found in large number. found in both eukaryotic and prokaryotic so they are called universal cellular organelles.considered as organelles within organelles as they are present mitochondria and plastids.related to protein synthesis so called protein factory of cells. contain r-RNA (ribonucleoprotein particles.70 subunit present in prokaryotic and 80 subunit present in eukaryotic.

Nucleus ( karyon)  

These are found in all eukaryotes except phloem ,sieve cells and mature RBCs. The study of nucleus known as karyology.membrane is called karyotheca . At the time of cell division , the prophase nucleus disappears.reappear completely in telophase by the assembling of fragments of endoplasmic reticulum . turitly seen by levlen work in fishes RBCs. credit for the discovery details study and terms nucleus goes to Robert brown.

Robert Brown studied the structure of nucleus in orchids root.Control of nucleus over cellular organelle is given by hammerling in algae acetabularia.nucleus is also called director or controller of the cell or control room or control centre.

Nucleus is double membranous largest cellular structure containing genetic information and controls cellular activity or metabolism to regular cell growth. In plants the nucleus is not spherical; it is oval elliptical because it is pushed by vacuole at the periphery.in animals it is present centre.

Structure of nucleus:

 1. Nucleoplasm:

These are also called karyolymph, karyoplasm ,nucleus matrix homogeneous colloidal semi fluid mainly composed of water different minerals mainly Ca2+ and mg2,Ca help in nucleus formation and Mg is help in ribosomes synthesis . so it contains water ,minerals ,protein ,enzyme nucleotide ,RNA polymers ,DNA polymerase.polymerase group of enzymes that work for the synthesis of RNA and DNA. In nucleoplasm highly fibres are found called nuclear matrix .These protein fibers are formed by lamin proteins that help in maintaining the structure of nucleoplasm.

2.Nucleolus: 

Nucleus

 First discovered by Fontane and detailed study was done by Wagner .The term nucleolus was given by Bowman .

The nucleolus is the distinct structure present in the nucleus of eukaryotic cells. Primarily, it participates in assembling the ribosomes, alteration of transfer RNA and sensing cellular stress. The nucleolus is composed of RNA and proteins, which form around specific chromosomal regions.

3. Fibrillar: 

In eukaryotic small filamentous pieces are known as fibrilar regions .These are made up of protein and RNA .They are precursors of granular regions. 

 4.Chromatin:

 nucleolus originates from chromatin or chromosomes .These chromatin called perinucleolar chromatin appear in the nucleus called nucleogenesis individual chromatin .