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)
Ans:
a)True
b) False
c) False
d) True
2. Make a sketch of the human nerve cell. What function do nerve cells perform?
Function of Nerve Cells:
The primary function of nerve cells (neurons) is to transmit electrical signals (impulses) between different parts of the body. They carry messages from receptor organs (like the skin, eyes, ears) to the brain and vice versa, enabling control and coordination of various body functions.
3. Write short notes on the following.
(a) Cytoplasm
(b) Nucleus of a cell
Short Notes on:
(a) Cytoplasm:
Cytoplasm is a semi-fluid substance that fills the space between the nucleus and the plasma membrane.
It contains all the cell organelles (e.g., mitochondria, ribosomes, Golgi bodies) and is the site for many biochemical reactions.
The cytoplasm helps in the exchange of materials between cell organelles and plays a role in cellular metabolism.
It is made up of about 80% water and is usually clear and colorless.
(b) Nucleus of a Cell:
The nucleus is a membrane-bound organelle found in eukaryotic cells. It serves as the control center of the cell.
Nuclear membrane: A double-layered membrane that encloses the nucleus. It separates the contents of the nucleus from the cytoplasm and has pores to allow the transport of substances.
Nucleolus: A small, dense, spherical structure within the nucleus. It is not membrane-bound and is responsible for producing ribosomes.
Chromosomes: Thread-like structures made of DNA. They carry genes, which store genetic information and are essential for inheritance. They regulate the transfer of characteristics from parents to offspring.
4. Which part of the cell contains organelles?
Soln:
The cytoplasm of the cell contains various organelles. It is a clear, colorless fluid that surrounds the cell’s nucleus and is the site where most of the cell’s metabolic activities take place. Organelles such as mitochondria, ribosomes, Golgi bodies, endoplasmic reticulum, and others are suspended in the cytoplasm
5. Make sketches of animal and plant cells. State the differences between them.
Soln:
Differences between Plant and Animal Cells:
6. State the difference between eukaryotes and prokaryotes.
7. Where are chromosomes found in a cell? State their function.
Soln:
Chromosomes are found in the nucleus of a cell. They are thread-like structures that carry genes. Genes contain all the necessary information required for the transfer of traits from parents to offspring. Chromosomes play a key role in inheritance and ensure that genetic information is accurately passed on during cell division.
8. “Cells are the basic structural units of living organisms.” Explain.
Soln:
Cells are the smallest units of life that carry out all the functions necessary for an organism’s survival. Every part of a plant or animal is made up of cells. They perform a wide range of activities, and their shape and size are related to their specific functions. Cells provide the structural foundation for living organisms, which is why they are referred to as the basic structural and functional units of life.
9. Explain why chloroplasts are found only in plant cells.
Soln:
Chloroplasts are plastids responsible for photosynthesis, the process by which plants convert sunlight into food. Since animals do not perform photosynthesis, chloroplasts are found only in plant cells. They contain the green pigment chlorophyll, which absorbs light energy for photosynthesis
10. Complete the crossword with the help of the clues given below.
Across
This is necessary for photosynthesis.
Term for component present in the cytoplasm.
The living substance in the cell.
Units of inheritance present on the chromosomes.
Down
Green plastids.
Formed by a collection of tissues.
It separates the contents of the cell from the surrounding medium.
Empty structure in the cytoplasm.
A group of cells.
Soln:
Across
Chlorophyll
Organelle
Protoplasm
Genes
Down
Chloroplast
Organ
Membrane
Vacuole
Tissue
