NCERT Solutions For Class 8 Science Chapter 8 Exercise
Chapter 8 – Cell – Structure and Functions
Questions:
1. Indicate whether the following statements are True (T) or False (F).
(a) Unicellular organisms have one-celled body. (T/F)
(b) Muscle cells are branched. (T/F)
(c) The basic living unit of an organism is an organ. (T/F)
(d) Amoeba has irregular shape. (T/F)
Soln:
a)True
b) False
c) False
d) True
2. Sketch the human nerve cell. What function do nerve cells perform?
Soln:
Transmitting messages from receptor organs to the brain and vice versa is the primary job of the nerve cell. It is in charge of how various bodily parts function.
3. Write short notes on the following.
(a) Cytoplasm
(b) Nucleus of a cell
Soln:
(a) Cytoplasm:
All of the cell organelles, including mitochondria, ribosomes, Golgi bodies, and others, are found in the fluid known as cytoplasm. It is situated in the space between the plasma membrane and the nucleus. It facilitates material transfer across cell organelles. It is typically transparent and colorless, consisting of 80% water.
(b) Nucleus of a cell:
In eukaryotic cells, the nucleus is a double-membrane-bound cell organelle. It has genetic material, DNA, in it. It is spherical and serves as the cell’s command hub. It consists of the following parts:
4. Which part of the cell contains organelles?
Soln:
There are several different cell organelles in the cytoplasm. It is a colorless, transparent fluid that includes organelles such as Golgi bodies, ribosomes, and mitochondria.
6. State the difference between eukaryotes and prokaryotes.
Prokaryotes |
Eukaryotes |
Most of them are unicellular |
Most of them are multicellular |
There is no nuclear membrane. So,the nucleus is poorly defined. |
There is a nuclear membrane. So, the nucleus is well-defined. |
Not all cell organelles are present |
All the cell organelles are present. |
Nucleolus is absent |
Nucleolus is present |
For example, blue-green algae, Bacteria |
For example, plants, animal cells, and fungi. |
7. Where are chromosomes found in a cell? State their function.
Soln:
Genes are carried by thread-like structures called chromosomes, which are found in the nucleus. The genes contain every piece of information needed to pass on traits from one set of parents to the next. Only because of chromosomes is it possible to inherit features.
8. “Cells are the basic structural units of living organisms”. Explain.
Soln:
Cells make up a variety of parts of both plants and animals. It can perform every living function and is the smallest unit of life. They serve as life’s fundamental components. Cells are known as “the basic structural and functional blocks of life” for this reason.
Cells come in a variety of sizes and forms and carry out a vast array of functions.
Their sizes and shapes correspond to the roles they play.
9. Explain why chloroplasts are found only in plant cells.
Soln:
Only plant cells include chloroplasts, plastids necessary for the food-producing process known as photosynthesis.
10. Complete the crossword with the help of the clues given below.
Across
1. This is necessary for photosynthesis.
3. Term for component present in the cytoplasm.
6. The living substance in the cell.
8. Units of inheritance present on the chromosomes.
Down
1. Green plastids.
2. Formed by a collection of tissues.
4. It separates the contents of the cell from the surrounding medium.
5. Empty structure in the cytoplasm.
7. A group of cells.
Soln:
Across
-
Chlorophyll
-
Organelle
-
Protoplasm
-
Genes
Down
-
Chloroplast
-
Organ
-
Membrane
-
Vacuole
-
Tissue