Class 8 science cells-structure and function Extra Questions

Important questions Cells Structure Class 8

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1.Name the study of cells which deals with structure and functioning of cell.

Cytology — It deals with the study of structure and functions of cell.

2. Cells are the basic unit of all living being yet they remained undiscovered for a long time. Why?

This was due to the gradual advances in micrology. Cells were discovered by Robert Hooke in 1665 after an examination of slices of cork which bared smaller compartments which were referred to as cells. Hookes description of the cells was published in Micrographia. The cell Knowledge has undergone further studies that have brought about refined understanding out of it only after discovery of good microphones about 150 years ahead

3. list two factors which determine the shape of cells.

Cell wall, and membrane determine the shape of cells.

4. why does the nerve cell posses a long fibre like structure.

Nerve cells have to be long so as to quickly transports impulses to the brain. If they were short, quick responses such as removing your hand from a hot surface would take too long and preventable harm would be done to your body.

5. Which Unit is used to measure the size of a cell? How is it denoted?

 you usually use the picometer or the nanometer (abbreviated: µ --micron ) or stated as: µm (micro metre). Micrometre is 1

6.cross section hen’s egg

7. Define the terms protoplasm cytoplasm and nucleoplasm

Protoplasm is the living contents of a cell that is surrounded by a plasma membrane. Protoplasm is composed of a mixture of small molecules such as ions, amino acids, and water.

A cytoplasm is the jellylike material, which makes up much of a cell in the cell membrane. In eukaryotic cells, it is that part of cell between the nuclear envelope and the cell membrane.

Nucleoplasm, is the fluid usually found in the nucleus of eukaryotic cells. This fluid contains primarily water, dissolved ions, and a complex mixture of molecules.

8. Define Tissue, Organ, Organ System

Tissue, is a group of cells with a common purpose that form a part of an organ, (i.e. esophagial tissue, stomach tissue, intestinal tissue.)

An organ is a group of tissues that form a part of an organ system, (i.e. esophagus, stomach, intestines)

An organ system is a group of organs with a common purpose. (for example the digestive system has the esophagus, stomach, intestines, and so on...)

9. Name two organ systems in plants and Animals each

A plant has two organ systems: 1) the shoot system, and 2) the root system.

Animals' bodies are made up of various body systems, groups of organs that work together to perform a function. These body systems (also referred to as organ systems) include:

• Reproductive system - The reproductive system enables animals to produce offspring.
• Nervous system - The nervous system enables animals to send, receive, and process nerve and sensory impulses.

10. what is the number of chromosomes in a human cell

In humans, each cell normally contains 23 pairs of chromosomes, for a total of 46.

11. Why are animal cells more flexible than plant cells?

Plant cells have cell walls around them, and animal cells don't have cell walls.The cell walls give plant cells their boxy shapes.
All cells have cell membranes, and the membranes are flexible. So animal cells can have various shapes, but plant cells only have the almost fixed shapes of their cell walls.

12. what is the function of chloroplast

The chloroplast is an organelle found in some plants cells and certain unicellular organisms. This is where photosynthesis (the process by which plants use the sun's energy to convert water and carbon dioxide to sugars) takes place.

13. List two functions of cilia and flagella

Cilia and flagella are cell organelles that are structurally similar but are differentiated based on their function and/or length. Cilia are short and there are usually many (hundreds) cilia per cell. On the other hand, flagella are longer and there are fewer flagella per cell (usually one to eight). Though eukaryote flagella and motile cilia are structurally identical, the beating pattern of the two organelles can be different. The motion of flagella is often undulating and wave-like, whereas the motile cilia often perform a more complicated 3D motion with a power and recovery stroke.

14. labelled diagram of euglena and paramecium

15. Flow Chart in a living cell: