Revision Notes: Respiratory System | Biology for SSS 2 PDF Download

The Respiratory System

Need for Energy

• Synthesis of Proteins: Energy is required to assemble amino acids into proteins, which are essential for various functions in living organisms.
• Production of Enzymes: Enzymes, which catalyze biochemical reactions, are produced using energy.
• Muscle Contraction for Movement: Energy is necessary for the contraction of muscles, enabling movement in animals.

Animals have a greater need for energy production compared to plants because they must move to find food and escape predators. Respiration is the process by which energy is released from glucose, a simple sugar, to fuel various life processes. The chemical equation for respiration is:

C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + ATP

• Glucose + Oxygen → Carbon Dioxide + Water + Energy (ATP)

Characteristics of Respiration

• The process of breaking down glucose into carbon dioxide and water occurs through a series of chemical reactions, not in a single step. These reactions include glycolysis, Krebs cycle, and electron transport.
• Each step of the breakdown is facilitated by a specific enzyme.
• A small portion of the energy released during the breakdown of glucose is given off as heat. However, most of it is converted into chemical energy in the form of Adenosine Triphosphate (ATP).

Kinds of Respiration

• Aerobic Respiration: This type of respiration occurs when glucose is broken down in the presence of oxygen. It is common in many animals, including humans, as well as in certain bacteria and fungi.
• Anaerobic Respiration: Anaerobic respiration takes place when glucose is broken down in the absence of oxygen. Unicellular organisms like yeast and some bacteria are examples of anaerobes that use this type of respiration.
• Fermentation: Fermentation is a specific process where pyruvic acid is converted into ethanol and carbon dioxide in the absence of oxygen. This process is carried out by certain microorganisms or their enzymes.

Differences between Aerobic and Anaerobic Respiration in Plants

Parts of Respiration

• Breathing: This is the physical process of taking in atmospheric air and expelling it from the lungs, which are the organs responsible for absorbing oxygen.
• Gaseous Transport: Once oxygen is absorbed by the blood in the lungs, it is transported throughout the body by red blood cells (RBCs) in the form of oxyhaemoglobin. Carbon dioxide, a waste product from the tissues, is transported back to the lungs by the blood via veins in two forms:
  • As bicarbonates dissolved in plasma.
  • In combination with hemoglobin in RBCs as carbamino-hemoglobin.
• Tissue Respiration: In this process, capillaries, which are the smallest blood vessels, transport oxygen to the body cells or tissues. Oxygen diffuses through the thin walls of the capillaries into the cells, while carbon dioxide, produced by the cells, is picked up by the capillaries and transported back to the lungs.
• Cellular Respiration: This refers to the complex chemical processes that occur inside the cells to release energy from glucose. Cellular respiration consists of three main stages:
  • Glycolysis: The breakdown of glucose into pyruvate.
  • Krebs Cycle: The further breakdown of pyruvate to produce energy carriers.
  • Electron Transport: The final stage where energy is produced in the form of ATP.

The respiratory system in humans includes the following components:

Role in Respiration:

• The diaphragm is crucial during the process of respiration.

Blood Supply to the Lungs:

• Deoxygenated blood is transported from the heart to the lungs via the pulmonary artery.
• The pulmonary artery branches into fine capillaries that surround the alveoli in the lungs.
• In the alveoli, the concentration of oxygen is higher than in the surrounding blood capillaries. This difference causes oxygen to move into the blood capillaries through diffusion.
• This process of gas exchange between the air and blood is known as external respiration.
• Inside the blood, red blood cells (RBCs) contain a pigment called haemoglobin, which has a strong affinity for oxygen. Hemoglobin acts as an oxygen carrier by binding to oxygen and forming oxyhaemoglobin.
• When oxyhaemoglobin reaches an area with low oxygen levels, it releases the oxygen. This occurs in the tissues, where the concentration of oxygen is lower. The released oxygen then diffuses into the tissues, and haemoglobin is re-formed in the process. This mechanism ensures that oxygen is supplied to all body tissues that are deficient in oxygen.
• The exchange of gases between the cells and blood is referred to as internal respiration.
• A significant portion of carbon dioxide produced in the tissues is converted into bicarbonate, which dissolves in the blood plasma. A smaller amount of carbon dioxide diffuses into the RBCs and combines with haemoglobin to form carbamino-haemoglobin.
• The blood, now rich in carbon dioxide, is transported back to the heart through the veins. From the heart, it is sent to the lungs via branches of the pulmonary artery.
• In the lungs, the concentration of carbon dioxide in the blood capillaries is higher than in the alveolar air. This difference causes carbon dioxide to move from the blood into the alveolar air through diffusion. The carbon dioxide is then expelled from the body during expiration.

Differences between Breathing and Respiration

BREATHING:

• Breathing is a physical process.
• It involves taking oxygen into the lungs.
• Breathing occurs outside the cells and does not release energy.
• The respiratory cycle includes inhalation, exhalation, and a brief pause.

RESPIRATION:

• Respiration is a chemical process.
• It involves transferring oxygen from the lungs to the bloodstream or cells.
• Respiration occurs inside the cells and releases energy.

Differences between Inspiration and Expiration

Control of Breathing Movements:

• Breathing movements are primarily regulated by a respiratory centre located in the medulla oblongata of the brain.
• These movements are usually involuntary, meaning they happen without conscious control. However, individuals can consciously alter the rate of breathing to some extent.

Air Sickness at High Altitudes:

• At higher altitudes, the concentration of oxygen in the air is lower. This can lead to a condition known as air sickness, where the body does not receive enough oxygen.
• Symptoms of air sickness may include dizziness, unsteady vision, hearing loss, lack of muscle coordination, and in severe cases, complete blackouts.

Hypoxia:

• Hypoxia refers to a condition where tissues do not receive an adequate supply of oxygen.
• This can occur in crowded spaces with poor ventilation or at high altitudes where oxygen levels are low.

Asphyxiation:

• Asphyxiation is a severe condition characterized by a critically low supply of oxygen to the body.
• It can result from various causes, including strangulation, drowning, choking, or any obstruction in the respiratory tract.

Comparison of Respiration in Plants and Animals

Similarities:

• Both plants and animals release energy during cellular respiration, which is stored in the form of ATP in the mitochondria.
• The end products of aerobic respiration in both cases are carbon dioxide and water.

Differences:

Respiration in Plants

• Plants do not show external ventilation or breathing movements.
• There is no gaseous transport involved; respiratory gases simply diffuse in and out of the cells.
• Oxygen released during photosynthesis can be an additional source of oxygen for plants.
• The end product of anaerobic respiration in plants is ethanol.
• Plants produce a small amount of heat during respiration, and the rate of respiration is comparatively lower.

Respiration in Animals

• Higher animals, such as humans, exhibit external ventilation or breathing movements.
• The tissue fluid, or blood, is responsible for the transport of gases in animals.
• Air is the primary source of oxygen for animals.
• The end product of anaerobic respiration in animals is lactic acid.
• Animals produce a large amount of heat during respiration, and the rate of respiration is comparatively higher.