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Life Processes in Animals - Respiration in humans

Grade 7CBSE

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

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Respiration is a vital biological process where food (glucose) is broken down in the cells with the help of oxygen to release energy. The overall process is represented as: Glucose+Oxygen→Carbon dioxide+Water+Energy\text{Glucose} + \text{Oxygen} \rightarrow \text{Carbon dioxide} + \text{Water} + \text{Energy}.

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Cellular Respiration occurs in the mitochondria of every cell. It is categorized into two types: Aerobic respiration (in the presence of O2O_2) and Anaerobic respiration (in the absence of O2O_2).

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Breathing is the physical process of inhalation (taking in air rich in O2O_2) and exhalation (giving out air rich in CO2CO_2). The breathing rate for an average adult at rest is 15−1815 - 18 times per minute.

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The Human Respiratory System includes the nostrils, nasal cavity, windpipe (trachea), bronchi, and lungs. The lungs are situated in the chest cavity and are surrounded by ribs.

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The Diaphragm is a large, muscular sheet that forms the floor of the chest cavity. During inhalation, the diaphragm moves down and ribs move up/outwards, increasing space in the chest cavity. During exhalation, the diaphragm moves up and ribs move down/inwards.

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Alveoli are small air sacs at the end of bronchioles where the actual exchange of gases (O2O_2 and CO2CO_2) takes place via diffusion.

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Anaerobic respiration in humans occurs in muscle cells during heavy exercise. This results in the production of Lactic Acid (C3H6O3C_3H_6O_3), which can cause muscle cramps.

📐Formulae

Aerobic Respiration: C6H12O6+6O2→6CO2+6H2O+Energy (38 ATP)\text{Aerobic Respiration: } C_6H_{12}O_6 + 6O_2 \rightarrow 6CO_2 + 6H_2O + \text{Energy (38 ATP)}

Anaerobic Respiration (Yeast): Glucose→Alcohol+CO2+Energy\text{Anaerobic Respiration (Yeast): } \text{Glucose} \rightarrow \text{Alcohol} + CO_2 + \text{Energy}

Anaerobic Respiration (Muscles): Glucose→Lactic Acid+Energy\text{Anaerobic Respiration (Muscles): } \text{Glucose} \rightarrow \text{Lactic Acid} + \text{Energy}

Breathing Rate=Number of breathsTime in minutes\text{Breathing Rate} = \frac{\text{Number of breaths}}{\text{Time in minutes}}

💡Examples

Problem 1:

An athlete's breathing rate was recorded during a training session. If the athlete took 450450 breaths over a period of 1515 minutes, calculate the breathing rate per minute.

Solution:

3015)450‾−45000\begin{array}{r} 30 \\ 15 \overline{) 450} \\ - 45 \phantom{0} \\ \hline 00 \end{array} The breathing rate is 3030 breaths per minute.

Explanation:

To find the breathing rate, we divide the total number of breaths (450450) by the total time (1515 minutes). Since 450÷15=30450 \div 15 = 30, the athlete is breathing faster than the resting average of 15−1815-18 breaths per minute due to increased energy demand.

Problem 2:

Why do we feel muscle cramps after heavy physical exercise like sprinting?

Solution:

During heavy exercise, the demand for energy is high but the supply of oxygen to produce that energy is limited. To fulfill the energy demand, muscle cells perform anaerobic respiration: Glucose→No O2Lactic Acid+Energy\text{Glucose} \xrightarrow{\text{No } O_2} \text{Lactic Acid} + \text{Energy}

Explanation:

The partial breakdown of glucose produces Lactic acid. The accumulation of this lactic acid in the muscles causes cramps. Relief can be obtained through a hot water bath or massage, which improves blood circulation and increases the supply of O2O_2 to break down lactic acid into CO2CO_2 and H2OH_2O.