9.5.6 Enthalpy

This is the sixth lecture from Chapter 5: “Energetics” in the new Class 9 Chemistry book (Punjab Board – PCTB). It discusses the two types of respiration: aerobic respiration and anaerobic respiration. The lecture also includes a multiple-choice quiz, short question and long question notes.

MCQs Based Quiz

9.5.6 Aerobic and Anaerobic Respiration

1 / 15

During respiration, we breath in ___ and breath out ___.

2 / 15

Respiration is an:

3 / 15

Which of the following is an exothermic reaction?

4 / 15

During glycolysis, one molecule of ___ is split into two molecules of pyruvate.

5 / 15

Which of the following chemical reaction produces carbon monoxide (CO)?

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Which of the following chemical species is used as an immediate source of energy in our cells?

7 / 15

The chemical process that converts our food into usable energy for our body is called:

8 / 15

The main form of energy production in bacteria and algae is ___.

9 / 15

Which of the following process produces ethanol as a byproduct?

10 / 15

Which of the following chemical reaction converts glucose into ethanol ($\mathrm{C_2H_5OH}$)?

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Which of the following chemical reaction converts glucose into carbon dioxide ($\mathrm{CO_2}$)?

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Which of the following is used as energy reserve in our bodies?

13 / 15

The excess food that we eat is stored as:

14 / 15

___ is primary storage form of glucose.

15 / 15

Glycogen is stored in ___.

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Short Questions

Q1. How would you define respiration?

Respiration is a continuous biochemical process through which living organisms fulfil their energy needs for metabolic functions.

Q2. What is aerobic respiration?

Aerobic respiration is a biochemical process that occurs in the presence of oxygen and converts glucose into carbon dioxide, water and energy.

$\mathrm{
\underset{(C_6H_{12}O_6)}{Glucose} \xrightarrow[In\ cytoplasm]{} \underset{(C_3H_4O_3)}{2\ Pyruvate} \xrightarrow[In\ mitochondria]{O_2} 6CO_{2\ (g)}\ +\ 6H_2O_{(g)}\ +\ Energy
}$

Q3. What is glycolysis?

Glycolysis is a biochemical process in which one molecule of glucose is broken into two molecules of pyruvate which results in production of 2 ATP (adenosine triphosphate)

$\mathrm{
\underset{(C_6H_{12}O_6)}{Glucose} \xrightarrow[In Cytoplasm]{} \underset{(C_3H_4O_3)}{2\ Pyruvate}\ + 2\ ATP
}$

Q4. What is the role of ATP in our bodies?

Adenosine triphosphate (ATP) is the energy source for our cells. They break down this ATP to get the energy required for metabolic activities.

Q5. How do our cells produce energy?

The food we eat is digested in our bodies and broken down into smaller molecules. These molecules are then absorbed by our cells where they undergo oxidation (respiration) to produce energy.

Q6. What is anaerobic respiration?

Anaerobic respiration is a biochemical process that occurs in the absence of oxygen and converts glucose into carbon dioxide, ethanol and energy.

$\mathrm{
\underset{(C_6H_{12}O_6)}{Glucose} \xrightarrow[In\ cytoplasm]{} \underset{(C_3H_4O_3)}{2\ Pyruvate}\ +\ Energy \xrightarrow[In\ yeast]{Absence\ of\ O_2} C_2H_5OH_{(l)}\ +\ CO_{2\ (g)}\ +\ Energy
}$

Q7. What are lipids?

Lipids are organic compounds which include fats, waxes, sterols, etc. They serve as energy reserve within our body.

Q8. From where does the fat in our come bodies form?

If we eat more food than we need in a day, the excess food is stored in the form of fat (lipids) in adipose tissues. This serves as energy reserve within our bodies.

Q9. What is the role of fat in our bodies?

Fat act as energy reserve within our bodies. In between meals and during exercise, our bodies rely on fat to provide energy.

Q10. What is glycogen?

Glycogen is the primary storage form of glucose. It is stored in liver and muscles.

Q11. How can you classify respiration based on the consumption of oxygen?

Based on the consumption of oxygen during the process respiration is divided into two categories.

  • Aerobic Respiration (with oxygen)
  • Anaerobic Respiration (without oxygen)

Descriptive Questions

Q1. Write a note on aerobic and anaerobic respiration of glucose.

Respiration is a continuous biochemical process through which living organisms fulfil their energy needs for metabolic functions.

The food an organism eat undergoes digestion in its body and these digested food molecules are absorbed by cells. There they undergo oxidation to produce energy. Because respiration releases energy it is an exothermic process.

Based on the consumption of oxygen during the process respiration is divided into two categories.

  • Aerobic Respiration (with oxygen)
  • Anaerobic Respiration (without oxygen)

Aerobic Respiration (With Oxygen):

Aerobic respiration is a biochemical process that occurs in the presence of oxygen and converts glucose into carbon dioxide, water and energy.

$\mathrm{
\underset{(C_6H_{12}O_6)}{Glucose} \xrightarrow[In\ cytoplasm]{} \underset{(C_3H_4O_3)}{2\ Pyruvate} \xrightarrow[In\ mitochondria]{O_2} 6CO_{2\ (g)}\ +\ 6H_2O_{(g)}\ +\ Energy
}$

Aerobic respiration happens in the presence of oxygen and glucose is converted into carbon dioxide, water and energy.

This type of respiration is more common in humans and other animals.

 Anaerobic Respiration (Without Oxygen):

Anaerobic respiration is a biochemical process that occurs in the absence of oxygen and converts glucose into carbon dioxide, ethanol and energy.

$\mathrm{
\underset{(C_6H_{12}O_6)}{Glucose} \xrightarrow[In\ cytoplasm]{} \underset{(C_3H_4O_3)}{2\ Pyruvate}\ +\ Energy \xrightarrow[In\ yeast]{Absence\ of\ O_2} C_2H_5OH_{(l)}\ +\ CO_{2\ (g)}\ +\ Energy
}$

Anaerobic respiration happens in the absence of oxygen and glucose is convenient into ethanol and carbon dioxide.

This type of respiration is common in bacteria and algae.

Glycolysis:

Glycolysis is the first step of respiration in which one glucose molecule ($\mathrm{C_6H_{12}O_6}$) is split into two molecules of pyruvate ($\mathrm{C_3H_{4}O_3}$). Glycolysis is an exothermic reaction with a net production of 2 ATP (adenosine triphosphate). This ATP is used as energy in the metabolic functions of our body. Our cells break down this ATP to get required energy.

Q2. Discuss energy storage role of lipids and glycogen.

Lipids:

  1. Lipids are group of organic compounds and include fats, waxes, sterols, etc.
  2. Lipids serve as energy reserve in our bodies.
  3. They fulfil almost half of the energy needs of our bodies.
  4. The extra food that we eat is converted into fat and stored in adipose tissues of our bodies.
  5. In between meals and during exercise our bodies rely on this fat to provide energy.

Glycogen:

  1. Glycogen is the primary storage form of glucose.
  2. It is stored in liver and muscles.

Q3. How would you compare the two types of respiration?

Heat

Enthalpy

Aerobic respiration is a biochemical process that occurs in the presence of oxygen and converts glucose into carbon dioxide, water and energy.

Anaerobic respiration is a biochemical process that occurs in the absence of oxygen and converts glucose into carbon dioxide, ethanol and energy.

It is an exothermic process.

It is also an exothermic process.

It produces CO2, H2O and energy.

It produces ethanol (C2H5OH), CO2 and energy.

Its first step is glycolysis which produces pyruvate (C3H4O3) and 2 ATP.

Its first step is also glycolysis which produces pyruvate (C3H4O3) and 2 ATP.

It occurs in the presence of oxygen.

It occurs in the absence of oxygen.

Most common form of respiration in human and other animals.

Most common form of respiration in bacteria and algae.