Kerala SSLC Class 9 Solutions for biology – For Obtaining Energy (English Medium)
Page No. 36:
Question 1:
The food we eat gets digested. After digestion, the nutrients reach the cells through blood.
How is energy got from these nutrients?
Solution:
The nutrients which reach the cells get oxidised and energy is released in the form of ATP.
Question 2:
Why do we take food?
Solution:
We eat food for the following reasons:
- To obtain energy
- For growth of the body
- To keep the bones, skin, hair and nails supple and strong
- To maintain the immune system of the body
Question 3:
What are the nutrients that reach cells through blood?
Solution:
Water, oxygen, simple sugars, amino acids, glycerol, fatty acids, minerals and vitamins reach cells through blood.
Question 4:
Examine the figure. Find out the position of the lungs.
Solution:
The lungs are located on either side of the chest in the thoracic cavity. They rest on the diaphragm.
Question 5:
Analyse the figure and label the parts in order from nostrils to alveoli in illustration. Prepare a note about the special features of each part.
Solution:
- Nostrils: Minute hair present in the nostrils prevent the entry of dust and harmful germs into the lungs.
- Nasal Canal: The nostrils continue into a passage called the nasal canal.The nasal canal opens into the pharynx.
- Pharynx: It serves as a common passage for both respiratory and digestive systems.
- Trachea: It is also called the wind pipe. Air enters into lungs through the trachea. It is made of C-shaped cartilaginous rings. The epiglottis is a flap-like structure which prevents the entry of food into the larynx.
- Bronchi: The trachea divides into the two bronchi which enter the left and right lungs.
- Bronchioles: Bronchi inside the lungs further divide into many branches forming bronchioles.
- Alveoli: Each bronchiole terminates or enters a set of alveoli. The exchange of gases between the blood and the lungs takes place at the alveoli.
Page No. 38:
Question 1:
How many times do we breathe in a minute normally?
Solution:
A healthy adult breathes 16-20 times in a minute normally.
Question 2:
Does any change happen to the thoracic cavity when you inhale and exhale?
Solution:
The thoracic cavity increases during inhalation and it decreases during exhalation.
Question 3:
How does the structure of the lungs suit the process of breathing?
Solution:
The structure of the lungs is suited for the process of breathing. The lungs are lobular structures which contain numerous alveoli for the exchange of gases. As the number of alveoli is very high, the surface area for the exchange of gases is also very high. Muscles of the rib and the diaphragm help in respiration.
Question 4:
What change occurs in the thoracic wall during breathing?
Solution:
Changes in the thoracic wall result in breathing. The diaphragm, a muscular wall which separates the abdominal cavity and the thoracic cavity, plays a key role in this. Contraction of the thoracic wall and the lowering of the diaphragm result in an increase in the thoracic cavity. This reduces pressure inside the thoracic cavity, thus resulting in inspiration. Similarly, the relaxation of the thoracic wall and the rising of the diaphragm result in a decrease in the thoracic cavity. This decreases the pressure inside the thoracic cavity, thus resulting in expiration.
Question 5:
What are the changes occurring to the air pressure in the thoracic cavity due to the change in the shape of the diaphragm?
Solution:
When the diaphragm lowers, the thoracic cavity increases and the air pressure in the cavity decreases, thus allowing air to rush into the lungs. On the other hand, when the diaphragm is raised or comes back to its normal position, the thoracic cavity decreases and the air pressure in the cavity increases, thus allowing air to rush out of the lungs.
Question 6:
Where did the oxygen that entered the lungs through inhaled air go to?
Solution:
The oxygen which enters the lungs through inhaled air gets absorbed in the blood through alveoli by the process of diffusion. The blood then supplies this oxygen to the cells of the body.
Question 7:
How did the amount of carbon dioxide increase in the exhaled air?
Solution:
Cells of the body release carbon dioxide to the bloodstream as a cellular waste product. This carbon dioxide is then exchanged at the alveoli and carbon dioxide diffuses into the lungs and is exhaled with air. Thus, the amount of carbon dioxide increases in the exhaled air.
Page No. 39:
Question 1:
Compare the concentration of oxygen and carbon dioxide in the blood carried by the pulmonary artery and the pulmonary vein.
Solution:
The concentration of carbon dioxide is more and the concentration of oxygen is less in the pulmonary artery. On the other hand, the concentration of carbon dioxide is less and the concentration of oxygen is more in the pulmonary vein.
Question 2:
Where is the concentration of oxygen high? In the alveoli or in the blood capillaries? What about the concentration of carbon dioxide?
Solution:
The concentration of oxygen is higher in the alveoli than in the blood capillaries. Hence, oxygen from the alveoli diffuses easily to the blood capillaries. On the other hand, the concentration of carbon dioxide is higher in the blood capillaries than in the alveoli. Hence, carbon dioxide from the blood capillaries diffuses easily to the alveoli.
Page No. 40:
Question 1:
Which component of the blood carries oxygen from the alveoli to the cell? How does that process take place?
Solution:
Haemoglobin present in the red blood cells binds to oxygen and carries it from the alveoli to the cell. When haemoglobin binds to oxygen, it forms oxyhaemoglobin. This oxyhaemoglobin is carried to the cell and oxygen is released at the cell forming haemoglobin again.
Question 2:
Are the characteristics of the red blood corpuscles and haemoglobin helpful in the exchange of gases? Why?
Solution:
Haemoglobin has a good capacity to bind to oxygen. It also dissociates quickly. Thus, at alveoli, when the concentration of oxygen is high, haemoglobin quickly binds to oxygen forming oxyhaemoglobin. Similarly, at the tissues, as the concentration of oxygen is less in cells, oxyhaemoglobin quickly dissociates and releases oxygen to the cells. Red blood cells are enucleated; hence, they have a good capacity to hold maximum number of molecules of oxyhaemoglobin.
Page No. 41:
Question 1:
What are the stages of cellular respiration?
Solution:
Stages of cellular respiration:
- Glycolysis: Glucose undergoes glycolysis forming pyruvic acid.
- Krebs cycle: Energy along with water and carbon dioxide are released.
Question 2:
What is the role of mitochondria?
Solution:
Mitochondria play a key role in the process of cellular respiration. It is the site of cellular respiration in cells.
It produces enzymes required for the oxidation of food during cellular respiration. The process of cellular respiration takes place partly in the mitochondrial matrix and partly in the cristae of mitochondria, and produces energy.
Question 3:
What is the amount of energy released?
Solution:
32 ATP molecules are released by oxidation of one molecule of glucose.
Question 4:
What is the available net energy?
Solution:
When one molecule of glucose is oxidised, the net available energy is 30 ATP molecules. Of 32 ATP molecules produced, 2 molecules are used in cellular respiration.
Question 5:
Analyse the illustration and prepare a note on how carbon dioxide is eliminated.
Solution:
- Carbon dioxide is produced in cells as a by-product of cellular respiration.
- This carbon dioxide is diffused into the tissue fluid from cells and eventually to the bloodstream.
- Blood carries carbon dioxide to the lungs.
- Carbon dioxide is carried by the blood in different forms by dissolving in the water of the plasma, as bicarbonate by dissolving in the water of RBCs or as carbaminohaemoglobin.
- This carbon dioxide in three forms is carried to the lungs and gets diffused in the lungs through alveoli.
- From the lungs, carbon dioxide is expelled from the nose through the nostrils.
Page No. 42:
Question 1:
Write a note on respiratory mechanisms of amoeba, earthworm, cockroach, scorpion, fish and frog.
Solution:
Page No. 43:
Question 1:
You have understood the peculiarities of respiration in bacteria and yeast. How does it differ from the process of respiration in man?
Solution:
The key difference in respiration in man and in bacteria and yeast is that man respires in the presence of oxygen, i.e. exhibits aerobic respiration, whereas bacteria and yeast respire in the absence of oxygen, i.e. exhibits anaerobic respiration.
Question 2:
Complete the table given below.
Solution:
Page No. 44:
Question 1:
We have learnt that we breathe in order to release energy from the food we take. If so, do plants which directly absorb solar energy have to breathe?
Solution:
Yes, plants also need to breathe. The exchange of gases in plants takes place through stomata. Carbon dioxide required for photosynthesis enters the plant body. Oxygen formed as a by-product during photosynthesis is utilised for respiration. Additional oxygen is given out through stomata during the day.
Question 2:
Do plants absorb oxygen just as animals do?
Analyse the given figure.
Solution:
No. The mechanism of absorbing oxygen from the atmosphere is different in plants.
In plants, gaseous exchange mainly occurs through stomata and to some extent through lenticels.
Carbon dioxide required for photosynthesis enters in the plant’s body. Oxygen formed as a by-product during photosynthesis is utilised for respiration. Additional oxygen is given out through stomata during the day. During the night, carbon dioxide is given out and oxygen is taken in.