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Lesson Posted on 21 Jun CBSE/Class 11/Science/Biology

cell organelles function

Vivek Paryekar

I have a total of 5 years teaching experience; I was a teacher in an ICSE school teaching science, especially...

cell is the basic unit of life. now what do you mean by basic. here basic means the smallest unit Membranes & Cell Coverings plasma membrane function What are the main components of cell membranes? What does the composition of a membrane tell you in general about permeability into a cell? Animal... read more

cell is the basic unit of life.

now what do you mean by basic. here basic means the smallest unit

 Membranes & Cell Coverings

  • What is the purpose of the microvilli?
  • specialized cell junctions

-adhesive junctions (desmosomes)

-tight junctions

-gap junctions

  • Cell Coverings in Plants

-cell wall

-plasmodesmata
-middle lamella

2. Endoplasmic reticulum (ER)

        -rough (RER) 
        -smooth (SER)

  • Functions

3. Golgi Apparatus

4. Nuclear envelope

  • Two membrane surrounding chromosomes
  • Comes from ER
  • Contains "pores"
  • What sort of molecules move between nucleus and cytoplasm?

5. Cytoplasmic matrix

What is the matrix?

What does the matrix do?

The cytoplasmic matrix has both a viscous flow like a liquid and elastic deformation like a solid (matrix near plasma membrane is more solid and in the cell center more liquid). Why?

6. Cytoskeleton

What is the cytoskeleton made of?

What does it do?

Examples

Membrane Bound Organelles

7. Nucleus

  • site of storage & replication of most cells hereditary material
  • contains chromosomes
  • contains nucleoli  
  • the degree of DNA packaging in chromatin depends on the state of the cell
  • single large DNA molecule in each chromosome many times longer than the chromosome
  • How is this compaction accomplished?

8. Lysosomes

  • single membrane bound organelle containing digestive enzymes
  • produced from the Golgi Complex
  • Functions
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Lesson Posted on 13 Jun CBSE/Class 11/Science/Biology

Biology Chapter 1: The Cell

Gunjan Sadera

Biology is a subject which can turn boring if not studied in a proper manner. Hence it can made easier...

1. What is Cell Biology?Branch of biology that deals with various aspects of structure, chemistry, development, genetics and functioning of cells are called cell biology. 2. Basic unit :The cell is the basic unit of life as no organism can have life without being cellular because the cell is a unit of... read more

1. What is Cell Biology?
Branch of biology that deals with various aspects of structure, chemistry, development, genetics and functioning of cells are called cell biology.
 
2. Basic unit :
The cell is the basic unit of life as no organism can have life without being cellular because the cell is a unit of both structure and function.
 
Organisms types ( on the basis of cell types)

Unicellular or acellular (organisms made of a single cell)

Eg: chlamydomonas, acetabularia, bacteria,yeast,amoeba
   
Multicellular (organisms made of many cells)

E.G., newly born infant (2 x 1012 cells)

3. Discovery of the cell:
   
1: Zacharias Janssen (1590): built the first microscope

2: Galileo (1610): Modified Microscope

3: Robert Hooke (1635-1703): a developed new microscope with which he studied the internal structure of a number of plants. His work was famous for the study of cork cells.

Robert Hooke > took a piece of cork of Spanish oak > prepared thin slice by means of sharp pen knife > deep planoconcave lens used  for throwing light > latter observed > cork had honeycomb structure with number of box-like compartments, each having a pore and separated from others by diaphragms > named as cellular (now known as cells).

Hooke microscope and structure of cork cells

4: Leeuwenhoek (1673): first to describe and sketch a live cell. He observed protozoa, spermatozoa, red blood cells etc.

5: Malpighi (1675) & grew (1682): gave an account of the internal structure of plants.

6: Mirbel (1802): said "Plants are formed by membranous cellular tissue"

7: Dutrochet (1824): stated " all organic tissues are really globular cells of an extreme smallness which are united by cohesion"

8: Robert Brown (1831) discovered the presence of nucleus in the cells of the orchid root.

9: Dujardin (1835): living semifluid substance of cells > named sarcode

10: Schleiden (1838): found all plant cells to have a similar structure- cell wall, a clear jelly-like substance and a nucleus.

11: Schwann(1838): discovered that animal cells lacked the cell wall.

12: Purkinje and Mohl (1838): renamed sarcode or jelly-like the substance of the cells as protoplasm

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Lesson Posted on 14 Apr CBSE/Class 11/Science/Biology CBSE/Class 12 Tuition/BA Tuition/Cell Biology

Ribosomes

Bhakti Makadia

I have 2 years of biology teaching experience and have a good skills in explaining the concepts.

While examining the animal and plant cell through a microscope, you might have seen numerous organelles that work together to complete the cell activities. One of the essential cell organelles are ribosomes, which are in charge of protein synthesis. The ribosome is a complex made of protein and RNA and... read more

While examining the animal and plant cell through a microscope, you might have seen numerous organelles that work together to complete the cell activities. One of the essential cell organelles are ribosomes, which are in charge of protein synthesis. The ribosome is a complex made of protein and RNA and which adds up to numerous million Daltons in size and assumes an important part in the course of decoding the genetic message reserved in the genome into protein.

The essential chemical step of protein synthesis is peptidyl transfer, that the developing or nascent peptide is moved from one tRNA molecule to the amino acid together with another tRNA. Amino acids are included in the developing polypeptide in line with the arrangement of codons of a mRNA. The ribosome, therefore, has necessary sites for one mRNA and no less than two tRNAs.

Made of two subunits, the big and the little subunit which comprises a couple of ribosomal RNA (rRNA) molecules and an irregular number of ribosomal proteins. Numerous protein factors catalyze distinct impression of protein synthesis. The translation of the genetic code is of essential significance for the manufacturing of useful proteins and for the growth of the cell.

Structure

Ribosomes are made of proteins and ribonucleic acid (abbreviated as RNA), in almost equal amounts. It comprises of two sections, known as subunits. The tinier subunit is the place the mRNA binds and it decodes, whereas the bigger subunit is the place the amino acids are included.

Both subunits comprise of both ribonucleic acid and protein components and are linked to each other by interactions between the proteins in one subunit and the rRNAs in the other subunit. The ribonucleic acid is obtained from the nucleolus, at the point where ribosomes are arranged in a cell.

The structures of ribosomes include:

  • Situated in two areas of the cytoplasm.
  • They are seen scattered in the cytoplasm and a few are connected to the endoplasmic reticulum.
  • Whenever joined to the ER they are called the rough endoplasmic reticulum.
  • The free and the bound ribosomes are very much alike in structure and are associated with protein synthesis.
  • Around 37 to 62% of RNA is comprised of RNA and the rest is proteins.
  • Prokaryotes have 70S ribosomes respectively subunits comprising the little subunit of 30S and the bigger subunit of 50S. Eukaryotes have 80S ribosomes respectively comprising of little (40S) and substantial (60S) subunits.
  • The ribosomes seen in the chloroplasts of mitochondria of eukaryotes are comprised of big and little subunits composed of proteins inside a 70S particle.
  • Share a centre structure which is very much alike to all ribosomes in spite of changes in its size.
  • The RNA is arranged in different tertiary structures. The RNA in the bigger ribosomes is into numerous continuous infusions as they create loops out of the centre of the structure without disturbing or altering it.
  • The contrast between those of eukaryotic and bacteria are utilized to make antibiotics that can crush bacterial disease without damaging human cells.ribosome structure

Ribosomes Size

Ribosomes comprise of two subunits that are suitably composed and function as one to translate the mRNA into a polypeptide chain amid protein synthesis. Due to the fact that they are made from two subunits of differing size, they are a little longer in the hinge than in diameter. They vary in size between prokaryotic cells and eukaryotic cells.

The prokaryotic is comprised of a 30s (Svedberg) subunit and a 50s (Svedberg) subunit meaning 70s for the entire organelle equal to the molecular weight of 2.7×106 Daltons. Prokaryotic ribosomes are about 20 nm (200 Å) in diameter and are made of 35% ribosomal proteins and 65% rRNA.

Notwithstanding, the eukaryotic are amidst 25 and 30 nm (250–300 Å) in diameter. They comprise of a 40s (Svedberg) subunit and a 60s (Svedberg) subunit which means 80s (Svedberg) for the entire organelle which is equal to the molecular weight of 4×106 Daltons.

Location

Ribosomes are organelles located inside the animal, human cell, and plant cells. They are situated in the cytosol, some bound and free-floating to the membrane of the coarse endoplasmic reticulum.

They are utilized in decoding DNA (deoxyribonucleic acid) to proteins and no rRNA is forever bound to the RER, they release or bind as directed by the kind of protein they proceed to combine. In an animal or human cell, there could be up to 10 million ribosomes and numerous ribosomes can be connected to the equivalent mRNA strand, this structure is known as a POLYSOME.

Function

When it comes to the main functions of ribosomes, they assume the role of bringing together amino acids to form particular proteins, which are important for completing the cell's activities.

Protein is required for numerous cell functions, for example, directing chemical processes or fixing the damage. Ribosomes can yet be discovered floating inside the cytoplasm or joined to the endoplasmic reticulum.

The other functions include:

  1. The procedure of creation of proteins, the deoxyribonucleic acid makes mRNA by the step of DNA transcription.
  2. The hereditary information from the mRNA is converted into proteins amid DNA translation.
  3. The arrangements of protein assembly amid protein synthesis are indicated in the mRNA.
  4. The mRNA is arranged in the nucleus and is moved to the cytoplasm for an additional operation of protein synthesis.
  5. The proteins which are arranged by the ribosomes currently in the cytoplasm are utilized inside the cytoplasm by itself. The proteins created by the bound ribosomes are moved outside the cell.

Taking into consideration their main function in developing proteins, it is clear that a cell can’t function in the absence of ribosomes.

Those that live inside bacteria, parasites and different creatures, for example, lower and microscopic level creatures are the ones which are called prokaryotic ribosomes. While those that live inside humans and others such as higher level creatures are those ones we call the eukaryotic ribosome. The other major differences include:

  1. Prokaryotes have 70S ribosomes, singly made of a 30S and a 50S subunit. While the Eukaryotes have 80S ribosomes, singly made of a 40S and 60S subunit.
  2. 70S Ribosomes are relatively smaller than 80S while the 80S Ribosomes are relatively bigger than 70S ribosomes.
  3. Prokaryotes have 30S subunit with a 16S RNA subunit and comprise of 1540 nucleotides bound to 21 proteins. The 50S subunit gets produced from a 5S RNA subunit that involves 120 nucleotides, a 23S RNA subunit that contains 2900 nucleotides and 31 proteins.
  4. Eukaryotes have 40S subunit with 18S RNA and also 33 proteins and 1900 nucleotides. The big subunit contains 5S RNA and also 120 nucleotides, 4700 nucleotides and also 28S RNA, 5.8S RNA as well as 160 nucleotides subunits and 46 proteins.
  5. Eukaryotic cells have mitochondria and chloroplasts as organelles and those organelles additionally have ribosomes 70S. Hence, eukaryotic cells have different kinds of ribosomes (70S and 80S), while prokaryotic cells just have 70S ribosomes.

 

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Answered on 24/12/2017 CBSE/Class 11/Science/Biology Tuition/Class XI-XII Tuition (PUC)

Bhuvesh Yadav

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Homeotherms are animals that have a constant body temperature. Poikilotherms are animals whose body temperature adjusts depending on the environment.
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Answered on 27/12/2017 CBSE/Class 11/Science/Biology Tuition/Class XI-XII Tuition (PUC)

Dhiraj Panja

Specially Biology

Diploblastic; body derived from two cell layer (endoderm&ectoderm)and triploblastic ;body derived from complete three embryonic cell layers i,e. Ectoderm,mesoderm,endoderm.
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Answered on 16/12/2017 CBSE/Class 11/Science/Biology Tuition/Class XI-XII Tuition (PUC)

Ekta Vishwakarma

Tutor

Amphibians are those organisms which live on both land and in water. Bryophytes are called amphibians of the plant kingdom because these plants though live in soil but they need water for sexu@l reproduction.
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Answered on 17/12/2017 CBSE/Class 11/Science/Biology Tuition/Class XI-XII Tuition (PUC)

Ekta Vishwakarma

Tutor

(a) They are smaller than bacteria. (b) They can be filterable. (c) May cause infection and diseases like small pox, flu etc. (d) Able to reproduce in host cells. (e) Use enzymes and metabolic machinery of host cell. (f) DNA/RNA is their genetic material. (g) They are obligate parasites, self replicating,... read more
(a) They are smaller than bacteria. (b) They can be filterable. (c) May cause infection and diseases like small pox, flu etc. (d) Able to reproduce in host cells. (e) Use enzymes and metabolic machinery of host cell. (f) DNA/RNA is their genetic material. (g) They are obligate parasites, self replicating, non- cellular organisms. (h) Plant viruses mostly have single stranded (ss) RNA. (i) All animal viruses mostly have single or double stranded RNA/DNA. (j) They have protein coat called capsid that protects nucleic acid. (k) They cause diseases in plants like mosaic, leaf curling, leaf role, yellowing, vein clearing, dwarfing as well as stunted growth etc. read less
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Answered on 07 Mar CBSE/Class 11/Science/Biology Tuition/Class XI-XII Tuition (PUC)

Sujatha

Tutor

Binomial nomenclature Taxonomical hierarchy.
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Answered on 12 Mar CBSE/Class 11/Science/Biology Tuition/Class XI-XII Tuition (PUC)

Arvind Singh

Tutor

Capsule is the distal most part of the sporophyte stage of mosses. Inside capsule haploid spores are formed after meiosis. These spores after dispersal and upon reception of optimum envromnent (moisture/temp) germinate to produce male or female gametophyte. Hence, we should remember that without the... read more

Capsule is the distal most part of the sporophyte stage of mosses. Inside capsule haploid spores are formed after meiosis. These spores after dispersal and upon reception of optimum envromnent (moisture/temp) germinate to produce male or female gametophyte. Hence, we should remember that without the capsule the haploid generation in the mosses wouldnt occur.

Thanks

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Answered on 08 Mar CBSE/Class 11/Science/Biology Tuition/Class XI-XII Tuition (PUC)

Who gave live Kingdom classification? What was the criteria used for such classification?

Gouthami

Tutor

Two kingdom classification was given by Carolus Linnaeus that is kingdom plantae and animalia based on whether organism performing photosynthesis (plantae) and locomotion (animals). Three kingdom classification was given by Ernst Haeckel ie plantae, animalia and (protista for unicellular organism).... read more

Two kingdom classification was given by Carolus Linnaeus  that is kingdom plantae and animalia based on whether organism performing photosynthesis (plantae) and locomotion (animals).

Three kingdom classification was given by Ernst Haeckel ie plantae, animalia and (protista for unicellular organism). 

Four kingdom classification was given by Copeland. He included Monera(Mychota) for prokaryotes along with plantae, animalia, protista.

Five kingdom classification was given by Robert H.Whittaker. He included fungi based on saprophytic mode of nutrition. 5 kingdom classification includes Monera,protista,fungi,plantae, animalia.

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