Life Processes Test - 89

The human intestine is a long tube-like structure. It includes small and large intestines. The small intestine comprises the duodenum, jejunum and ileum and measures about 6 metres in length. The food received from the stomach is continually mixed and stirred for further digestion in the small intestine. There are small finger-like structures called villi present all along the surface of the small intestine which helps in the absorption of nutrients, carbohydrates and fats by increasing the surface area.   

The dialysing fluid has the same components (glucose, water, electrolytes, etc.) as that of blood, except the nitrogenous waste - urea. During the dialysis procedure, the patient’s blood is passed through the tubes suspended in a tank filled with the dialysing fluid. These tubes are lined with a semi-permeable lining. During this passage, the nitrogenous waste product (urea) from the blood passes into the dialysing fluid by diffusion. The purified blood (without urea) is then pumped back into the patient's body.

The human transport system is a system of tubes with a pump and valves to ensure one-way blood flow. We need a transport system to deliver oxygen, nutrients, hormones and other substances to all our body cells and take away waste products from them. 

The correct pathway is: Vena cava $$\rightarrow$$ Right atrium $$\rightarrow$$ Right ventricle $$\rightarrow$$ Pulmonary artery $$\rightarrow$$ Lungs $$\rightarrow$$ Pulmonary veins $$\rightarrow$$ Left atrium $$\rightarrow$$ Left ventricle $$\rightarrow$$ Aorta $$\rightarrow$$ Rest of the body.

The arteries carry blood away from the heart, while veins return blood to the heart. With both, their structure is related to their function. Blood in the arteries is under high pressure generated by the heart. The arteries have thick outer walls and thick layers of muscle and elastic fibers. The blood in veins is under lower pressure than the blood in arteries. The veins have thin walls and thin layers of muscle and elastic fibers. Unlike arteries, veins have one-way valves in them to keep the blood moving in the correct direction.

Translocation is the movement of food particles from the leaves to other tissues throughout the plant. Carbohydrates are the product of photosynthesis, which are translocated to other parts through the phloem. If the rate of translocation of food is slow then the respiration will slow down, which utilizes the food and the food will remain in the cell and thus, the rate of photosynthesis will decrease.

The majority of carbon dioxide molecules (85 percent) are carried as part of the bicarbonate buffer system. In this system, carbon dioxide diffuses into the red blood cells. Carbonic anhydrase (CA) within the red blood cells quickly converts the carbon dioxide into carbonic acid (H$$_2$$CO$$_3$$). Carbonic acid is an unstable, intermediate molecule that immediately dissociates into bicarbonate ions (HCO$$_3$$−) and hydrogen (H+) ions. Since carbon dioxide is quickly converted into bicarbonate ions, this reaction allows for the continued uptake of carbon dioxide into the blood, down its concentration gradient. It also results in the production of H+ ions. If too much H+ is produced, it can alter blood pH. However, hemoglobin binds to the free H+ ions, limiting shifts in pH. The newly-synthesized bicarbonate ion is transported out of the red blood cell into the liquid component of the blood in exchange for a chloride ion (Cl-). This is called the chloride shift. When the blood reaches the lungs, the bicarbonate ion is transported back into the red blood cell in exchange for the chloride ion. The H+ ion dissociates from the hemoglobin and binds to the bicarbonate ion. This produces the carbonic acid intermediate, which is converted back into carbon dioxide through the enzymatic action of CA. The carbon dioxide produced is expelled through the lungs during exhalation. 

Digestion process is facilitated by enzymes. Since oesophagus just helps in transferring of partially digested food from mouth to stomach, it has no active role in digestion process. It is thus devoid of any enzyme secretion. Thus, the correct answer is option A.

Blood pressure (BP) is the pressure exerted by circulating blood upon the walls of blood vessels. It is usually measured at a person's upper arm. Blood pressure is usually expressed in terms of the systolic (maximum) pressure over diastolic (minimum) pressure and is measured in millimeters of mercury (mm Hg). It is one of the vital signs along with respiratory rate, heart rate, oxygen saturation, and body temperature. Normal resting blood pressure in an adult is approximately 120/80 mm Hg.