Respiration

• Respiration denotes the process whereby glucose is metabolized to produce ATP (Adenosine Tri-Phosphate), which serves as the primary cellular energy source.
• This pivotal metabolic process occurs exclusively within the mitochondria of cells.

Breathing

• Breathing entails the act of inhaling and exhaling atmospheric air.
• Inhalation facilitates the uptake of oxygen into the lungs, while exhalation allows for the expulsion of carbon dioxide from the lungs.

ATP (Adenosine Tri-Phosphate)

• ATP functions as the predominant form of energy utilized within cells.

ATP equation: ATP ⇌ ADP + P1 + Energy

ADP (Adenosine Di-Phosphate)

P1 - Phosphate

ATP as the Cell's Energy Currency

• ATP consists of three phosphate molecules. The cleavage of a phosphate bond results in the production of ADP and energy. ADP can subsequently combine with a phosphate molecule, requiring energy input, to regenerate ATP.
• This perpetual cycle of ATP breakdown and regeneration ensures cells can effectively acquire and utilize energy.

The Respiratory System

• The respiratory system facilitates the interchange of gases between the organism's body and its surrounding environment.
• It encompasses anatomical structures such as the nostrils, nasal cavity, pharynx, trachea, bronchi, bronchioles, and lungs.
• The nasal cavity carries out crucial functions of warming, moistening, and purifying the inhaled air.

The Breathing Journey

• When we breathe, air enters our body through either the nose or mouth. If we inhale through the nose, it passes through the conchae, then goes into the pharynx and trachea.
• The epiglottis plays an important role by allowing air to pass through while guiding food towards the esophagus.
• Moving on from the trachea, the air travels into the bronchi, then continues through the bronchioles until it finally reaches the alveoli. These tiny air sacs are surrounded by capillaries.
• Inside the alveoli, oxygen enters our bloodstream, while carbon dioxide exits the blood and enters the alveoli. Red blood cells carry the oxygen, and when we exhale, carbon dioxide is expelled.
• During inhalation, our diaphragm contracts, causing the lungs to expand. On the other hand, during exhalation, the diaphragm relaxes, allowing the lungs to deflate.

Oxygen

• Oxygen is crucial for ATP production and cellular functions.
• It is transported by blood cells, with hemoglobin, containing iron, facilitating its binding and release.

Characteristics of Efficient Gas Exchange (Lungs & Gills)

• Thinness: For example, alveoli have thin walls, enabling efficient gas diffusion.
• Large surface area: Lungs contain numerous alveoli, maximizing the available surface area for gas exchange in a compact space.
• Moisture: Moist surfaces promote the dissolution of gases, facilitating their diffusion across thin membranes.
• Abundant blood supply: A rich network of capillaries ensures the effective transport of gases to and from exchange surfaces, allowing for efficient gas exchange.

Gas Exchange in the Alveoli

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• Oxygen diffuses from the alveoli into the narrow space between the alveoli and capillaries, then enters the blood capillaries. Red blood cells transport oxygen to other body cells through the bloodstream.
• Carbon dioxide, produced as a waste product by cells, diffuses from the cells into the blood capillaries. Blood carries carbon dioxide to the alveoli through circulation, and it is subsequently eliminated during exhalation.

Note: Diffusion occurs due to differences in gas concentration between regions.

Inhalation & Exhalation

Inhalation/Inspiration

• Inhalation brings air into the lungs, providing oxygen for respiration.
• During inhalation, the external intercostal muscles contract, causing the ribs to move up and out. Simultaneously, the diaphragm contracts and flattens.
• These movements increase lung volume and decrease air pressure within the lungs, allowing air to enter.

Exhalation/Expiration

• Exhalation removes air from the lungs, eliminating carbon dioxide.
• The external intercostal muscles relax, causing the ribs to move down and in. The diaphragm relaxes and returns to its domed shape.
• These changes reduce lung volume and increase air pressure within the lungs, forcing air out.

Respiration

Aerobic Respiration

• Aerobic respiration refers to the breakdown of glucose in the presence of oxygen. It is also known as cellular respiration and primarily occurs in the mitochondria of cells.

Glucose + Oxygen → Carbon Dioxide + Water + ATP + Heat Energy

• Aerobic respiration generates ATP, carbon dioxide, water, and heat energy.
• The heat energy released during this process helps maintain the body's core temperature at around 36°C.

Anaerobic Respiration

• Anaerobic respiration is the breakdown of glucose in the absence of oxygen, which can occur in plants, yeast, and some animals.

Fermentation in Yeast & Plants

Demonstrated through the process of bread-making.

• Initially, yeast utilizes any accessible oxygen and undergoes aerobic respiration. When oxygen becomes scarce, yeast transitions to anaerobic respiration, leading to the production of carbon dioxide, which causes the dough to rise.

Glucose → Carbon Dioxide + Ethanol

During the baking process, ethanol evaporates, resulting in bread without alcohol. Nevertheless, ethanol finds its use in the production of beer and wine.

Anaerobic Respiration in Animals

• In the absence of oxygen, glucose undergoes partial oxidation, resulting in the production of lactic acid and ATP.
• Under normal circumstances, sufficient oxygen is supplied through regular breathing, known as aerobic respiration.
• However, during intense physical activity or when oxygen demand surpasses supply, anaerobic respiration serves as an alternative energy source.
• Anaerobic respiration is sustainable only for a brief duration.
• The process generates lactic acid and a minimal amount of energy. Lactic acid is toxic to cells, leading to muscle soreness and fatigue. It cannot persist in the body indefinitely, resulting in an oxygen debt.
• Following strenuous exercise, the accumulated lactic acid must be broken down through vigorous and rapid breathing, repaying the oxygen debt.

Negative Effects of Smoking

• Cigarettes contain nicotine, a highly addictive substance that raises blood pressure and heart rate.

Carbon Monoxide

Red blood cells contain hemoglobin, which weakly binds with oxygen, aiding its diffusion into cells.

• Cigarette smoke contains carbon monoxide, which strongly binds to hemoglobin. Red blood cells carrying carbon monoxide preferentially

bind with it over oxygen,

leading to reduced oxygen supply to body tissues.

Hemoglobin + Carbon Monoxide → Carboxyhemoglobin

• Insufficient oxygen supply eventually results in cellular damage and death.