Class 9 Science Chapter 5 Question Answers - The Fundamental Unit of Life

Q1: Name the smallest cell and the longest cell in human body.
Ans: The smallest cell in the human body is the red blood cell or the sperm cell in males. The longest cell is the nerve cell.

Q2: What is osmosis?
Ans: The movement of water molecules through a selectively permeable membrane is known as osmosis. This process occurs when water moves from an area of higher concentration to an area of lower concentration.

Q3: Why does mitochondria have largely folded inner membrane?
Ans: Mitochondria have largely folded inner membrane which provides the increased surface area for ATPgenerating chemical reactions. Mitochondria is the site for cellular respiration and provides energy to the cell.

Q4: Which organelle makes the digestive enzyme of lysosome?
Ans: The rough endoplasmic reticulum (RER) is responsible for producing the digestive enzymes found in lysosomes.

Q5: Name the cell organelles that have their own DNA and ribosomes. Name the autonomous organelles in the cell.
Ans: The cell organelles with their own DNA and ribosomes are mitochondria and plastids. Chloroplast and mitochondria are the autonomous organelles in the cells.

Q6: What is the energy currency of the cell?
Ans: ATP—Adenosine Triphosphate.

Q7: Where are genes located in the cell?
Ans: Genes are located in the chromosomes in the nucleus of the cell.

Q8: What is the cell wall composed of ?
Ans: The cell wall is primarily made of cellulose, which is a complex substance. This composition provides structural strength to plants.

Q9: Where are proteins synthesized inside the cell?
Ans: Proteins are synthesised in the ribosomes, which are often referred to as the cell's protein factories.

Q10: What would happen if the plasma membrane breaks down?
Ans: If plasma membrane breaks down then molecules of some substances will freely move in and out.

Q11: State two conditions required for osmosis.
Ans: Conditions required for osmosis:

• Concentration difference: There must be a difference in the concentration of water, with one side having a higher concentration than the other.
• Semi-permeable membrane: A semi-permeable membrane is necessary to allow the flow of water.

Q12: What is the function of vacuoles?
Ans: Vacuoles are the storage sacs for solid or liquid content. In plant cells, it provides turgidity and rigidity to the cell. In single-celled organisms, vacuoles store food, e.g. amoeba.

Q13: Why are plasma membrane called selectively permeable membrane?
Ans: Plasma membrane allows to go in and out some materials to and from the cell. It also prevents movement of some other materials. So, it is called selectively permeable membrane.

Q14: Why are plasma membrane called selectively permeable membrane?
Ans: Plasma membrane allows to go in and out some materials to and from the cell. It also prevents movement of some other materials. So, it is called selectively permeable membrane.

Q15: What are genes?
Ans: Gene is a part of DNA. They are located on chromosomes in linear fashions. One gene may perform one or more function. Genes are carrier of genetic character.

Q16: Do vacuoles store material? If so, name them.
Ans: Yes, vacuoles store some important substances required in life of the plant cell. These are amino acids, sugars, various organic acids and also some proteins.
Example : Amoeba, vacuoles also store food.

Q17: Which cell organelle is known as the ‘suicidal bags’ of a cell? Why?
Ans: Lysosomes are known as suicidal bag of cell. During the disturbance in cellular metabolism, lysosome may burst and the enzymes digest their own cell. Hence, lysosome are called ‘suicide bags’ of a cell.

Q18: What are chromosomes? What are they made of?
Ans: The compact rod-like bodies inside the nucleus are called chromosomes. These are seen at the time of cell division. They are made up of deoxyribonucleic acid or DNA and proteins.

Q19: How are new cells reproduced?
Ans: Cells multiply by dividing themselves again and again. Cells divide to produce cells of their own kind.

Q20: What is a prokaryotic cell?
Ans: A cell in which there is absence of a defined nuclear region and a nuclear membrane is called a prokaryotic cell. Prokaryotic cells are generally small in size. They lack membrane bound cell organelles. They have a single chromosome.

Q21: How does a living cell perform basic functions?
Ans: A living cell perform basic functions by division of labour among specific components within it is known as cell organelles.

Q22: Write a function of cell membrane.
Ans: Its major function is to hold cellular contents and control passage of materials in and out of the cell.

Q23: Give example of working of chromoplasts.
Ans: Spinach looks green due to the presence of chloroplasts, papaya is yellow and edible part of watermelon is red due to the presence of chromoplasts.

Q24: Which cell organelle transmits the heredity information from parents to offspring?
Ans: Genes are the functional units of chromosomes which transmit the heredity information from parents to offspring. These are located on chromosomes.

Q25: Where do lipids and proteins get synthesized?
Ans: Lipids get synthesized in the smooth endoplasmic reticulum and proteins get synthesised in the ribosome and rough endoplasmic reticulum.