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Cell Biology Flashcards

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1
Q

Who discovered cell?

A

Robert Hooke

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2
Q

Define cell

A

Cell is the structural and functional unit of life capable of independent existence and replication.

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3
Q

What are the features of modern cell theory?

A
  1. All cell arise from pre-existing cells of similar kind by cell division.
  2. Each cell is capable of independent existence but not cell organells.
  3. Every cell is totipotent provided the suitable conditions.
  4. Every cell must perform homeostasis for survival else the cell dies of enthalpy.
  5. A cell has definite life span,
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4
Q

Demerits of cell theory are:

A
  1. Viruses are living but doesn’t have cellular structure.
  2. Mature mammalian RBC and sieve tube cells don’t have nucleus.
  3. Mucor doesn’t have definite differentiation of cells i.e. they have coenocytic structure.
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5
Q

Differences of prokaryotic and eukaryotic cells.

A
  1. True nucleus (absent in prokaryotic cells)
  2. In P.C. DNA is not organized with histone proteins, and lies freely in cytoplasm
    In E.C. organized DNA lies in ( nucleus, mitochondria and plastid) .
  3. IN PC ribosome is of 70s type but in E.C. It is of 80s type in cytoplasm and 70s type in mitochondria and plastid.
  4. Cyclosis absent in P.C. and present in E.C.
  5. Cell division in P.C. is mostly amitosis and in E.C. mitosis and meiosis.
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6
Q

Differences between plant cell and animal cell.

A
  1. Cell wall
  2. Plastid
  3. Nucleus lies in periphery, in the center.
  4. Vacuoles ( Large vacuole in plant cell and absent or small size vacuole in animal cell )
  5. Centrosome and lysosome ( Generally absent in plant cell and present in animal cell)
  6. Osmotic bursting absent in plant cell and present in animal cell.
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7
Q

What is osmotic bursting?

A

Occurs when the liquid outside a cell enters the cell causing it to burst.

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8
Q

What is cell wall?

A

The outer rigid semi-elastic, permeable, supportive and protective layer present in plant cell, bactera, fungi and some protists is cell wall.

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9
Q

What is cell wall derived from?

A

Living Protoplast

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10
Q

Cell wall consists of?

A
  1. Middle lamella
  2. Primary cell wall
  3. Plasmodesma
  4. Secondary cell wall
  5. Pits
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11
Q

Functions of cell wall are?

A
  1. Mechanical support
  2. Protects inner components from mechanical injury.
  3. Prevents osmotic bursting of cell when kept in hypotonic solution.
  4. Help in transfer of protoplasmic material among adjacent cells which is done by plasmodesmata.
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12
Q
  1. Middle lamella
A

First formed cementing layer after cytokinesis that is present between two adjacent cells. Made up of calcium and magnesium pectate which joins two adjacent cells.

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13
Q
  1. Primary cell wall
A
  • Thin layer
  • Present in inner layer of middle lamella
  • They are made up of cellulose, chitin and murein in the cell wall of plant, fungi and bacteria respectively.
  • Made up of matrix and microfibers.
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14
Q
  1. Plasmodesmata
A
  • Cytoplasmic or protoplasmic bridges present in primary cell wall of adjacent cells that transfer cytoplasmic contents among adjacent cells.
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15
Q
  1. Secondary cell wall
A
  • Situated inner to primary cell wall
  • thick layers
  • can’t expand
  • present in cell of thick
  • present in cell wall dead tissue of plants (sclerenchyma)
  • Made up of matrix and microfibers
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16
Q
  1. Pits
A
  • Depressed areas present in secondary cell wall
  • Consists of pit chamber and pit membrane
  • Consists of primary cell wall and middle lamella
  • Helps in translocation of materials between two adjacent cells.
17
Q

What is cell membrane (plasmalemma) ?

A

Cell membrane is a thin, semi permeable covering of protoplasm primarily composed of phospholipid bilayer.

18
Q

Who discovered cell wall?

A

Robert Hooke

19
Q

Cell wall is absent in?

A

Germ cell (animal cell)

20
Q

What are the theories about the supposition of structure of cell wall?

A
  1. Lamellar Model
  2. Fluid Mosaic Model
21
Q

Lamellar model was proposed by?

A

Danielli and Davson

22
Q

In which organism tertiary wall is present?

A

Exceptionally present in tracheids of gymnosperm.

23
Q

Why was the sandwich model rejected?

A

The sandwich model was rejected because it could not explain the dynamic and complex nature of the cell membrane, could not explain the transport of solutes and solvents, could not explain bulk transport through cell membrane due to which it was discarded.

24
Q

What was the structure of cell membrane according to Danielli and Davson?

A
  • Solid and stable structure
  • Phospholipid consisting of polar hydrophilic head and non-polar hydrophobic tail.
25
Q

Who proposed fluid mosaic model?

A
  • Singer and Nocolson
26
Q

According to fluid mosaic model, how is cell membrane described?

A
  • Dynamic, quasifluidy in nature
  • Protein icebergs in sea of phospholipid
27
Q

Advantages of Fluid Mosaic Model :

A
  1. Dynamic structure
  2. Quasifluidy structure
  3. Supports lipid : protein ratio
  4. Explain bulk transport and active transport
28
Q

Functions of cell membrane :

A

1) Since it is semi-permeable, it helps in pathogen differentiation
2) Bulk transport
3) It helps in exchange of gases with external environment by process of diffusion.
4) Water regulation by osmosis

Biology (19 decks)

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