Question:
Why can't single cells grow very large? Or Big organisms like human beings are multi-cellular? Why can't such big organisms be a single large cell?
Answer:
Cell is the fundamental unit of life. All metabolic activities (necessary for life) takes place inside the cell. All raw materials required for these metabolic activities enter through the cell surface via cell membrane. Greater the surface are, large amount of raw material can enter (this is the case of uni-cellular micro-organisms). As the size of cell grows larger, the Surface Area to Volume (SA/V) ratio decreases, it means raw material required for the cell to survive will not be sufficient. Thus, SA/V ratio limits the size of the cell. Therefore big organisms like human beings are mulch-cellular.
The Fundamental Unit of Life
Q 1.
Which cell organelle is known as 'protein factory'?
Q 2.
Identify cell organelle and write down its name:
A tough, non-living layer, it prevents plant cells from bursting, freely permeable
Q 3.
What is the plasma membrane composed of?
Q 4.
Is plasma membrane permeable or selectively permeable?
Q 6.
Why is mitochondria absent in red blood cells?
Q 7.
Identify cell organelle and write down its name:
A network of flattened cavities surrounded by a membrane, which links with the nuclear membrane. Help in packaging proteins.
Q 8.
What are chromosomes?
Q 9.
What is the full form of DNA and RNA?
Q 10.
Name the two postulates of the cell theory.
Q 11.
Which cell organelle is called 'kitchen of plant'?
Q 12.
Are plastids present in all cells? What are its types?
Q 13.
Which of the following cell is better candidate to study lysosomes?
(a) White Blood Cell
(b) Muscle Cell
Q 14.
Who expanded cell theory by suggesting that all cells arise from pre-existing cells?
Q 15.
Name the biggest cell in human body.
Q 16.
Name the sac like structure which form the grana?
Q 17.
Identify cell organelle and write down its name:
Digestive organelle where macromolecules are hydrolyzed
Q 18.
Give examples of cells which are muti-nucleate (i.e. having many nuclei).
Q 19.
Who observed the cells the first time?
Q 20.
Give an example of anucleate cell i.e. cell without nucleus.
Q 21.
Which cell organelle is called 'transport system'?
Q 22.
What are the function of nucleus?
Q 23.
Identify cell organelle and write down its name:
Slipper or oval shaped, its inner membrane is multi-folded and has lot of chemical activity
Q 24.
In which year electron microscope was invented?
Q 25.
Name the smallest cell in human body.
Q 26.
What are different types transport of components across cell membrane?
Q 27.
Place a de-shelled egg in water for five minutes. What do you observe? (Note: De-shelled egg means,the shell of an egg is removed by dissolving it in dilute hydrochloric acid. The shell is mostly calcium carbonate. A thin outer skin now encloses the egg.)
Q 28.
Identify cell organelle and write down its name:
Called 'suicide bags' of a cell.
Q 29.
Who proposed the cell theory?
Q 30.
Who coined the term 'protoplasm'?
Q 31.
Name the cell in human body which cannot reproduce.
Q 33.
What are the conditions for osmosis?
Q 34.
Name the cell type that have internal membranes which compartmentalize their functions.
Q 35.
Identify cell organelle and write down its name:
A partially permeable layer prevents cell contents from escaping controls what substances enter and leave the cell. Identify?
Q 36.
Identify cell organelle and write down its name:
Powehouse of cell
Q 37.
Give an example of cells containing two nuclei (Binucleate).
Q 38.
Will the temperature have any effect on the process of the osmosis?
Q 39.
Which organ of the plant body helps in osmoregulation?
Q 40.
What are the components nucleus?
Q 41.
Who proposed fluid-mosaic model of cell or plasma membrane?
Q 42.
What is plasmolysis?
Q 43.
When chromosomes are visible in the nucleus?
Q 44.
Who is known as 'Father of Microscopy'?
Q 45.
What is the function of nucleoplasm?
Q 46.
Why can't single cells grow very large? Or Big organisms like human beings are multi-cellular? Why can't such big organisms be a single large cell?
Q 47.
Identify cell organelle and write down its name:
Contains green colour pigment, traps light energy. Present in some plant cells.
Q 48.
Identify cell organelle and write down its name:
Appear brown dots either present freely in cell or bound to a membrane and make proteins.
Q 49.
Identify cell organelle and write down its name:
Controls cell division and cell development.
Q 50.
Who discovered Golgi apparatus?
