Life Processes

Diffusion is the movement of a substance from an area of high concentration to an area of low concentration. The exchange of gases take place in the millions of alveoli in the lungs and the capillaries that envelop them. Due to the difference in concentration, inhaled oxygen moves from the alveoli to the blood in the capillaries, and carbon dioxide moves from the blood in the capillaries to the air in the alveoli.

Saliva contains the enzyme salivary amylase. It breaks down starch into simpler molecules such as maltose. Starch is a polysaccharide made up of many units of glucose. Maltose, on the other hand is a disaccharide produced when starch is broken down by amylase.

Dialysis fluid contains all the constituents of the plasma except the nitrogenous wastes. Urea is the main nitrogenous waste of the body. In case of kidney failure, urea gets accumulated in the blood.

Paramecium uses cilia to sweep food particles along with some water into an oral groove (a groove present on the surface of paramecium). At the end of the oral groove, a food vacuole gets created. This food vacuole further travels throughout the cytoplasm and during this journey, the food inside the vacuole gets digested and absorbed.

The alveoli are surrounded by tiny blood vessels, called capillaries. It is the alveoli that receive the oxygen and pass it on to the blood.

Excess or unused carbohydrates produced during photosynthesis are stored in the form of starch (polysaccharide/polymer of simple glucose molecules) as a reserve of energy for future use in various parts of the plant body.

Veins collect blood from different parts of the body and bring it back to the heart. They do not need thick walls because the blood is no longer under pressure, but instead, they have valves to ensure that the blood flows only in one direction towards the heart.

The force that blood exerts against the wall of a blood vessel is known as blood pressure. Blood pressure is measured with an instrument called sphygmomanometre. It consists of an inflatable rubber cuff, which is wrapped around the upper arm and is connected to an apparatus that records blood pressure.

The digestion of proteins starts in the stomach by the action of gastric juices produced by the walls of the stomach. Further, it also takes place in the duodenum and ileum of the small intestine under the action of pancreatic and intestinal juices respectively.

In our circulatory system, the artery divides into smaller and smaller vessels to bring the blood in contact with all the individual cells. These small vessels have walls which are one-cell thick and are known as capillaries. Exchange of material between the blood and surrounding cells take place across this thin wall. The capillaries then join together to form veins that carry the blood away from the organ or tissue.