Science questions in details [4 marks ]

Chloroplasts are the green coloured plastids present in the cytoplasm of plant cells. They possess photosynthetic pigment called chlorophyll. Chlorophyll absorbs energy from the sunlight during the process of photosynthesis. In the process of photosynthesis, green plants make their own food in the presence of sunlight and chlorophyll with the help of inorganic substances like carbon dioxide and water. Thus, chloroplast help in the synthesis of food by green plants.

Chromosomes are thread-like structures usually present in the nucleus that become visible only during cell divisions. The function of chromosomes is to transfer the characters from parents to the off springs through the genes located on them.

The differences between eukaryotes and prokaryotes are:

Eukaryotes	Prokaryotes
The cells having a well-organized nucleus with a nuclear membrane are termed as eukaryotic cells.	The cells having nuclear material without nuclear membrane are termed as prokaryotic cells.
Most eukaryotes are multi-cellular.	Most prokaryotes are unicellular.
Cell organelles such as mitochondria, plastids, golgi bodies, etc. are present.	Cell organelles such as mitochondria, plastids, golgi bodies, etc. are absent.
Example: Fungi, onion cells, etc.	Example: Bacteria and blue green algae.

Parameter	Plant Cell	Animal Cell
Sketch
Cell wall	Present	Absent
Size	Small	Large
Vacuole	Large	Small or Absent
Plastids	Present	Absent

Nucleus of a cell: Nucleus is an important component of the living cell. It is mostly spherical and located in the centre of the cell. It is separated from the cytoplasm by a membrane called the nuclear membrane. In addition, nucleus contains thread-like structures called chromosomes. These carry genes and help in inheritance or transfer of characters from the parents to the offspring. Nucleus, in addition to its role in inheritance, acts as control centre of the activities of the cell. The entire content of a living cell is known as protoplasm. It includes the cytoplasm and the nucleus. Protoplasm is called the living substance of the cell.

Cytoplasm: Cytoplasm is the jelly-like substance present between the cell membrane and the nucleus. Various other components or organelles like mitochondria, golgi bodies, ribosomes, etc. are present in the cytoplasm. Cytoplasm helps exchange and storage of substances among cell organelles. Most of the metabolic activities occur inside cytoplasm.

he size of the cells of an organism is not related with the size of its body. This can be understood with the example of an elephant and a rat. The cells in elephant are not bigger as compared to the cells of small animal like rat. Hence, proving that cells are not related to the size of organism. However, the size of a cell is related to the function it performs. The nerve cells in both rat and elephant are long and branched and perform the same function of transferring and receiving messages. Thus, helps in coordination of different functions of body parts.

The above mentioned statement is wrong. The unicellular organisms also respire, reproduce and carry all metabolic functions like multicellular organisms. The difference is that all the functions are performed by the single cell in a unicellular organism. Similar functions in multicellular organisms are performed by various organs (organ system) which are made up of many different types of cells.

An Ameoba cell can change its shape and a white blood cell in human blood can also changing its shapes. The difference between an Amoeba cell and a white blood cell is that the Amoeba cell is a full-fledged organism which is capable of independent existence. While white blood cell is only a cell of human blood which is not a full-fledged organism and hence cannot exist independently. White blood cells can exist only inside the blood.

Plant organs	Anlmai organs
Leaf	Brain
Roots	Lungs
Stem	Kidneys
Flower	Heart

S.No.	Plant cell	Animal cell
1.	Cell wall is present.	Cell wall is absent.
2.	Larger in size.	Smaller in size.
3.	They have one large central vacuole.	Many small vacuoles are found.
4.	Chloroplast is present which helps plant in photosynthesis.	Chloroplast is absent.

Plant cell	Animal cell
Cell wall is present and is made of cellulose.	They lack cell wall.
Usually lack lysosomes and peroxisomes.	Lysosomes and peroximes are present.
They have one large central vacuole.	Many small vacuoles are found.
Chloroplast is present which helps plant in photosynthesis.	Chloroplast is absent.

Prokaryotic cells	Eukaryotic cells
Bacterium cell.	Amoeba cell.
Blue-green algae cell.	Human cheek cell.
	onion peel cell.