Respiration in Organisms-III

Glucose is the most common respiratory substrate.

Cytoplasm is the site of glycolysis. 

Fats yield the highest energy per gram.

Aerobic respiration produces approximately 36-38 ATP molecules per glucose molecule, whereas anaerobic respiration yields only 2 ATP. This 18-fold difference in energy yield makes aerobic respiration far more advantageous for organisms. Option C is incorrect because both processes cause complete breakdown - anaerobic also fully breaks down glucose (to lactate/ethanol).

Pneumatophores are called breathing roots.

Respiratory enzymes are located in mitochondrial matrix of the cell. It is also called power house of the cell.

Photosynthesis and respiration are complementary processes - photosynthesis uses CO2 and water to produce glucose and oxygen (in chloroplasts using light energy), while respiration uses glucose and oxygen to produce CO2, water, and ATP (in mitochondria). They are essentially reverse reactions forming a biological carbon cycle. Circulation and osmoregulation are not complementary to respiration.

The theoretical maximum ATP yield from aerobic respiration is 38 ATP (or sometimes cited as 36). Anaerobic respiration (fermentation) produces only 2 ATP per glucose molecule - the net gain from glycolysis alone since fermentation doesn't produce additional ATP. Options A and B have the order reversed, while option C is incorrect as glycolysis does produce 2 ATP even in anaerobic conditions.

Oxygen is a reactant in aerobic respiration. Oxygen enters the cell by diffusion. It is first transported to the cells via the red corpuscles. These contain haemoglobin, a transporter protein that carries oxygen to the cells of the body.

Vital capacity is the maximum volume of air a person can expel from lungs after maximal inhalation (VC = TV + IRV + ERV). For an average adult human, this ranges from 3000-4500 ml. Option B's lower bound is too high, while options C and D represent tidal volume and residual volume respectively, which are much smaller. Option A has a typo character but the range is correct.

The trachea is prevented from collapsing by C-shaped cartilaginous rings made of hyaline cartilage. These rings provide structural support while allowing flexibility for esophagus expansion behind the trachea (the open part of C faces posteriorly). Muscles and diaphragm are involved in breathing mechanics but don't support the trachea structure itself. Ribs protect the lungs but not the trachea.

If the thoracic wall is punctured, the man dies as the lungs get punctured.

During inspiration (inhalation), the diaphragm contracts and flattens, increasing the volume of the thoracic cavity. This creates negative pressure that draws air into the lungs. During expiration, the diaphragm relaxes and returns to its dome shape. Option A is vague (expands is not the precise term - contracts/flatten is more accurate).

Gas exchange in alveoli occurs by simple diffusion - oxygen moves from alveolar air (higher PO2) into blood (lower PO2), and CO2 moves from blood (higher PCO2) into alveoli (lower PCO2). This is passive movement down concentration gradients without energy expenditure. Osmosis is water movement, active transport requires energy, and passive transport is a broader category.

Increased CO2 concentration in blood is detected by chemoreceptors in the medulla and carotid bodies, which signal the respiratory center to increase breathing rate. This enhanced ventilation helps eliminate excess CO2 and restore normal blood pH. This is a negative feedback mechanism - elevated CO2 triggers increased breathing to reduce it back to normal levels.

During strenuous exercise, when oxygen supply cannot meet the demand, muscle cells undergo anaerobic respiration. Pyruvate from glycolysis is converted to lactic acid (lactate) instead of entering the Krebs cycle. This allows glycolysis to continue by regenerating NAD+. Glycogen is broken down to glucose (not vice versa), and starch is not involved in animal metabolism.

The epiglottis is a flap-like structure located at the entrance of the larynx (wind pipe). When you swallow, it closes over the larynx to prevent food or liquid from entering the respiratory tract. The glottis is the vocal cord opening, larynx is the voice box, and pharynx is the shared passage for both air and food - none of these prevent entry.

Polio is caused by the poliovirus which attacks the nervous system, specifically motor neurons in the spinal cord, causing paralysis. It does not affect the lungs. Pneumonia, bronchitis, and asthma are all respiratory conditions that directly affect lung tissue - pneumonia involves lung inflammation, bronchitis affects bronchial tubes, and asthma causes airway constriction.

During heavy exercise, muscles require more oxygen than can be supplied, leading to anaerobic respiration. This process produces lactic acid as a byproduct, which accumulates in muscle tissue and causes cramps. The other options are incorrect because CO2 is a normal byproduct, ethanol is produced in yeast fermentation, and muscles never have complete absence of oxygen (that would cause tissue death, not cramps).