Page 83 - Ripples SCIENCE 7 - TEJPUR Edition 2024 Answer Key

9. Respiration

Chapter in a Nutshell

v Every organism is made up of tiny structural & functional units called cells that perform
all necessary functions, such as digestion, transportation, excretion, reproduction and
respiration.

v Energy is required for all the above functions which is acquired by the food the living
organisms consume.

v The food consumed by us is broken down into simpler substances–glucose & amino acids
during digestion.
v The glucose is further broken down in the presence of oxygen to release energy, carbon

dioxide and water. This energy is used by all the cells of the body to perform various life
processes. This process is called respiration.
v Respiration takes place in two steps–breathing and cellular respiration.

v Breathing is a mechanical process in which oxygen is inhaled and carbon dioxide is exhaled.
v The process of breathing in oxygen-rich air is called inhalation whereas the process of
breathing out carbon dioxide is called exhalation.

v The percentage of nitrogen in the inhaled and exhaled air remains the same because it is
neither used nor released in the process of respiration.

v Breathing is a continous process throughout the life of an organism.
v During inhalation, our chest expands where as it relaxes (contracts), when we exhale.
v Lungs are filled with air when the diaphragm moves downwards on inhalation. During

exhalation, the lungs flatten and the diaphragm moves upwards.
v The number of times a person breathes in a minute is called the breathing rate of the person.

Normal breathing rate is about 15-18 times in a minute. This rate does not always remain
constant.
v At higher altitudes, amount of oxygen is reduced due to low atmospheric pressuse. Less

amount of oxygen is available to our lungs, which may cause dizziness & may also result in a
condition called hypoxia. Therefore, mountaineers often carry oxygen cylinders with them
for sufficient supply of oxygen at higher altitudes.

In cellular respiraton, glucose breaks down with the help of oxygen into carbon dioxide,
water and energy.
C H O + 6O  6CO + 6H O + Energy
6
2
2
12
6
2
Glucose Oxygen Carbon Water (in the form of ATP)
dioxide
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