Cells-Part One

Question 1

First saw and described live cell

Answer 1

Anton von Leeuwenhoek

Question 2

Discovered nucleus

Answer 2

Robert Brown

Question 3

Cell theory proponents

Answer 3

Matthias Schleiden- 1838 (German botanist), Theodore Schwann 1839 (British zoologist), Rudolf Virchow (Russian?)

Question 4

Fluid Mosaic Model

Answer 4

Singer and Nicholson (1972)

Question 5

Golgi Apparatus

Answer 5

Camillo Golgi (1898)

Question 6

Contribution of Matthias Schleiden (German Botanist)- 1838

Answer 6

Examined a large number of plants and observed that all plants are composed of different kinds of cells which form tissues of the plant

Question 7

Contribution of Theodore Schwann (British Zoologist)- 1839

Answer 7

Studied different types of animal cells and reported that cells had a thin outer layer which is today known as ‘plasma membrane’. Also concluded, based on his studies on plant tissue that presence of cell wall is a unique character of the plant cells. On the basis of this, Schwann proposed he hypothesis that the bodies of animal and plants are composed of cells and products of cells.

Question 8

Sizes of mycoplasma, bacteria, human RBC

Answer 8

Mycoplasma- 0.3 micrometer
Bacteria- 3 to 5 micrometer
Human RBC- 7 micrometer

Question 9

Prokaryotic cells are represented by

Answer 9

Bacteria, Blue green algae, Mycoplasma, PPLO

Question 10

Order of bacteria according to abundancy

Answer 10

Bacillus, Cocci, Vibrio, Spirillum

Question 11

Sizes wrt eukaryotic cell

Answer 11

Eukaryotic: 10 to 20 micrometer
Typical bacteria: 1 to 2 micrometer
Virus: 0.02 to 0.2 micrometer
PPLO: about 0.1 micrometer

Question 12

Genomic DNA of prokaryotics

Answer 12

Single chromosome, circular DNA

Question 13

Prokaryotes have something unique in the form of

Answer 13

Inclusions
Reserve material stored. Not bound by any membrane system and lie freely in the cytoplasm.
Example: phosphate granules, cyanophysean granules, glycogen granules.
Gas vacuoles are found in purple, blue green and green photosynthetic algae.

Question 14

Cell envelope of Prokaryotes is

Answer 14

Chemically complex

Trilayered: Glycocalyx, cell wall and plasma membrane

Question 15

Name a special membranous structure of Prokaryotes which is formed by the extension of plasma membrane. These extensions are in the form of? Give 6 functions.

Answer 15

Mesosomes
Occur in the form of vesicles, tubules and lamellae.
Functions: 1) cell wall formation
2) DNA replication
3) distribution to daughter cells
4) respiration
5) secretion process
6) increase surface area of plasma membrane and enzymatic content

Question 16

Name the pigment containing membranous extensions present in cyanobacteria

Answer 16

Chromatophores

Question 17

Which surface structures do not play a role in motility in Prokaryotes?

Answer 17

Pili and Fimbriae
Pile are elongated tubular structures made of a special protein.
Fimbriae are small bristle like fibres sprouting out of the cell. In some bacteria, they are known to help attach the bacteria to rocks in streams and also to host tissues.

Question 18

Where are ribosomes found in prokaryotes? Give size details. What do the ribosomes of a polysome do?

Answer 18

Ribosomes are found associated with the plasma membrane in Prokaryotes. They are about 15nm by 20nm in size.
The ribosomes of a polysome translate the mRNA into proteins.

Question 19

First saw and described a live cell

Answer 19

Anton von Leeuwenhoek

Question 20

Eukaryotes include

Answer 20

Protists, plants, animals and fungi

Question 21

Animal cells have centrioles which are absent in all paint cells. True or False?

Answer 21

False. Absent in almost all plant cells. (Found in Chlamydomonas)

Question 22

When was the study of he detailed structure of plasma membrane possible?

Answer 22

After the advent of the electron microscope in the 1950s

Question 23

Plasma membrane is made up of? Describe arrangement.

Answer 23

LIPIDS, PROTEINS, CARBOHYDRATES (latter’s presence revealed later upon biochemical investigation)
Major lipids are phospholipds.
The lipid component of the membrane consists mainly of phosphoglycerides.
In addition to phospholipids, membrane also consists of CHOLESTEROL.
Hydrophillic polar head outside and hydrophobic non polar tail inside. Thus ensures that the non polar tail do saturated hydrocarbons is protected from aqueous environment.
Proteins: peripheral (lie on surface of membrane
Integral (partially or totally buried)

Question 24

What is fluidity? (Answer wrt Fluid Mosaic Model, 1972)

Why is this fluid nature important?

Answer 24

Ability of protein to move within the membrane. (The quasi-fluid nature of lipid enables lateral movement of proteins within the overall bilayer)
Fluidity has the following other functions as well:
1) cell growth
2) formation of intercellular junction
3) secretion
4) endocytosis, exocytosis
5) cell division

Question 25

What is fluidity? (Answer wrt Fluid Mosaic Model, 1972)

Answer 25

Ability of protein to move within the membrane. (The quasi-fluid nature of lipid enables lateral movement of proteins within the overall bilayer)

Question 26

Give the most important function of plasma membrane. Elaborate.

Answer 26

TRANSPORT of molecules. PM is selectively permeable to substances on both sides. Types: Passive: eg neutral solutes may move along the PM according. To their concentration gradients Diffusion, osmosis (Def: many molecules can move briefly without expenditure of energy) POLAR MOLECULES CANNOT TRAVEL ACROSS A NON POLAR LIPID BILAYER. Hence, need a carrier protein of the membrane to facilitate their transport across it. Some molecules or ions are transported across the membrane against their concentration gradient and require energy to do so hence, Active transport. Eg Na+ K+ pump.

Question 27

Name the non living rigid structure which forms the outer covering of the plasma membrane of fungi and plants. Give functions.

Answer 27

Cell wall. 1) gives shape 2) protection 3) cell to cell interaction 4) barrier to undesirable macro molecules

Question 28

Give composition of algal and plant cell wall and of the middle lamella as well.

Answer 28

Algal cell wall: cellulose, galactans, mannans and minerals like calcium carbonate Plant cell wall: cellulose, hemi-cellulose, playing and proteins Middle lamella: calcium pectate

Question 29

What is the cell wall of a young plant call called?

Answer 29

Primary cell wall. It is capable of growth which gradually diminishes as the cell matures and the secondary wall is formed on the inner membrane of the cell.