Cell: The Unit Of Life Flashcards by Sai Pritam

Who discovered cell and when??

Robert Hooke in 1665

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Who discovered first living cell??

Antonvon Leewenhoek

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Who discovered nucleus?

Robert Brown

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Who told about plants in cell theory??

In 1838 Matthias Schleiden a German Botanist observed plant species and concluded that plants are made of different cell which later on form tissue.

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Who told about animal cell and what extra did the scientist discovered?

In 1839 Theodare Schwann a British Zoologist studied about animal cell and observed that animal have a thin covering (delimiting) structure known as plasma membrane. Based on his plant studies, he also concluded that presence of cell wall is unique in plant. He proposed a hypothesis that bodies of plants and animal are made of cell and its products.

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Who got the credit of cell theory and what were they not able to explain?

The credit goes to Schleiden and Schwann. They were unable to explain how new cell are formed??

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Who gave a new shape to the cell theory when and how??

Rudolf virchow in 1855 modified the cell theory and explained how new cells are formed. New cells are formed from pre-existing cells. (Omnis cellula e cellula).

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What were the points of cell theory?

(i) All organisms are made of cell and its products
(ii) Cells arise from pre-existing cells.

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Difference Between Prokaryotic cells and Eukaryotic cells?

Prokaryotic cell-
(i) Pro: primitive
Karyon: nucleus
(ii) Lack well developed nucleus.
(iii) Lack membrane bound organelles.
(iv) 70s Ribosomes are formed.

Eukaryotic cells-
(i) Well developed nucleus is present.
(ii) Membrane bound organelles are present.
(iii) 70s and 80s Ribosomes are found.

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Difference between Plant cells and animal cell..

Plant cell-
(i) Cell wall present
(ii) Plastids are present
(iii) Vacuoles are present
(iv) Centrioles are absent
(v) Unconnected structure of golgi body known as dictyosome

Animal cell-
(i) Cell wall absent
(ii) Plastids are absent
(iii) Animals have smaller vacoule
(iv) Centrosomes/Centrioles are present
(v) It is known as Golgi Body

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What are non membrane organelles?

Ribosomes, Centrosomes/Centrioles(helps in cell division)

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Which is the main arena of enzymatic reactions and what is the advantage?

Cytoplasm. It helps to maintain cell in its living state.

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What’s is the size of mycoplasma, Bacteria, and diameter of RBC??

Mycoplasma- 0.3 micrometer
Bacteria- 3-5 micrometer
Dia of RBC- 7 micrometer

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Which is the largest and longest cell?

Longest cell- Nerve Cell
Largest Cell- isolated ostrich egg

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What is the shape of- RBC, WBC, Columnar epithelial cell, Mesoplyll cells, nerve cell and tracheid?

RBC- Round and biconcave
WBC- amoeboid
Columnar epithelial cell - long and narrow
Mesoplyll cells- Round and oval
Nerve cell- Branches and long
Tracheid- elongated

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Points of prokaryotic cells-

(i) Size is smaller and multiply rapidly.
(ii) Prokaryotic cells/organisms exhibit a wide range of structure.
(iii) Depending upon the shape, bacteria can be of 4 types-
(a) Bacillus- Rod Shaped
(b) Coccus- spherical
(c) Vibrio - comma shaped
(d) Spirillum - Spiral shaped
Example of Prokaryotic cells- Bacteria, pleuropneumonia like organism(PPLO), etc..

In Bacteria cell, tell about Ribosomes, mesosomes, chemically complex envelope, polysome, Plasmids, flagella, genetic material..

Ribosomes: attached to plasma membrane, 15nm to 20nm size, 70s type.

Mesosomes- Inflodings of plasma membrane.

Chemically complex envelope- Glycocalyx(outer most), Cell wall(Middle) and Plasma Membrane(innermost).

Polysome/ Polyribosome- Helps in protein formation(Translation).

Plasmids- (i) autonomous self replicating, double stranded circular DNA.
(ii) Provide unique features to bacteria such as-
(a) Resistance to antibiotics
(b) Helps in bacterial transformation.

Flagella (If the bacteria is motile)- This filmentous extension of plasma membrane.

Genetic material- Naked Genetic Material, single chromosome, genophore, prochromosome, necleoid.

What is Inclusion body?

(i) Phosphate Granule(stores Phosphate)
(ii) Cyanophyceen Granulea
(iii) Glycogen granules ( store glucose)

Apart from this, single non-unit membrane structure id present-
(i) Poly B Hydroxybutyrate
(ii) Sulphur granules
(iii) Gas Vacoule(Provide Buyancy)
(Bluegreen, Purple, Green)- Helps in Photoshnthesis

What does the chemical envelope contains??

Glycoxalyx
Cell wall
Cell membrane/ plasma membrane

What is glycocalyx??

(i)Outermost layer of bacteria.
(II) made of polysaccharides
(iii) can be represented into 2 forms
(a) Loose sheath- Slime layer, Helps in bacteria to prevent water loss
(b) Thick and tough layer- Capsule, provide gummy and sticky nature and helps to hide from host immune system.

What is Cell wall??

(I)Made of peptidoglycan.
(II) Shape, and structural support
(iii) helps to prevent collapsing/busting.
(iv) Protect the cell from mechanical injury

What is cell membrane??

(I) lipid and protein(phospholipid)
(II) structurally it is similar to eukaryotes
(Iii) selectively permeable
(Iv) Interact with outside world.

What are the infoldings of plasma membrane??

(a) mesosome
(b) chromatophores

What are measosome??

Increase the surface area for energetic reactions.
Helps in DNA replication and distribution of/to daughter cell.
Secretion, respiration, cell wall formation etc

What are chromatophores??

It contains pigment and helps in photosynthesis in some Cyanobacteria/ blue green algae

What are the types of ribosomes in bacteria?

Cytoplasmic Ribosome- Synthesis protein which is needed inside cell (non secretary) Plasma membrane associated ribosome- Synthesis of proteins which are related to outside cell (Secretary Proteins)

What is the structure of bacteria??

(I) Involved in Motality- Flagela Made up of flagellum proteins, Extension of plasma membrane, no.of arrangement varies. Not involved in motility- Pili(elongated tubular structure) and Fimbriae. Made of pilin proteins, Helps in sexual reproduction(conjunction), Bristle like structure helps to attach to host or substratum such as rocky surface etc.

Name the Indian Scientist who is mentioned in this chapter

G.N. Ramachandra- Triple helical structure of collagen.

Eukaryotic cells points-

Protista, Plantae/ plants, animals, etc. Compartmentalisation is seen All eukaryotic cells are not identical. I.e. plants cell differ from animal cell Cytoskeleton structures are not present which provide structural support. Well developed nucleus with nuclear membrane is present. Membrane bound structures are also present.

Points of cell membrane of eukaryotic cells.

In 1950s with the help of electron microscope, structure of plasma membrane was explained while working on RBC. A very popular model of plasma membrane given by Singer and Nicholson (1972) which was fluid mosaic model.

Composition of cell membrane-

Lipids (phospholipid) -> (lecithin/cephalin) Protein- on the ease of extraction ,— (I) peripheral proteins- present towards outer side. (II) integral protein- present partially/ totally buried in membrane) Lipid: Quasified nature Proteins: lateral movement (large size) Lipid: flip flop movement :. Ice bergs of proteins floats on the sea of lipid

Transport of molecule across the membrane:-

Active transport- ATP is required Ex- Na/K pump in animal cells Passive Transport- ATP not required to pass Ex- Transport of neural molecules. Transport of gases through diffusion. Polar molecules= Transmembrane proteins (facilitated diffusion)

Nature of plasma membrane

Plasma membrane is amphipathic in nature (Hydrophilic and hydrophobic) Plasma membrane is assymeteic Fluidity is the ability to move within the membrane.

What’s the significance of fluid nature of membrane-

Cell growth and Formation of intercellular junction, secretion, endocytosis, cell division and exocytosis

Cell wall points in eukaryotic cell

Non living, rigid structure, composition varies among different species. Surrounds Plasma membrane. Function: (I) structural support (II) protect from injury (Iii) cell-cell interaction Algae- Cellulose, galactans, mannans and minerals like CaCO3 Plants- Cellulose, Hemicellulose, pectin, protein Fungi- Chitin (A polymer of N-acetyl glugosamine) Bacteria- peptidoglycan layer

Types of cell wall

(I) Primary Cell wall- Present initially in plants(young) Thin walled elastic capable of extension Outer layer Diminished upon maturity Single layer Secondary cell wall- Develop later on in plants, thick walled, Grows inside primary layer due to the deposition of certain materials, grows well with maturity.