B4 F) Metabolism
Many reactions in the body are linked together. The products of one reaction will react to create another product, that will react to produce another product etc.
There are two different types of reactions in cells:
1) The building of larger molecules from smaller ones. For example, the combining of glucose and nitrate ions to make amino acids that are made into proteins (such as enzymes). Another example is the joining together of glucose molecules to create starch, glycogen and cellulose. Starch is how plants store glucose, glycogen is how animals store glucose and cellulose is used to strengthen the cell wall of plant cells.
2) The breaking down of larger molecules into smaller molecules. The most important example is the breaking down of glucose in respiration reactions. When plenty of oxygen is present, glucose (C6H12O6) is broken down with oxygen to create water (H2O), carbon dioxide (CO2) and energy. Another example is where excess proteins are broken down to produce urea, which is excreted through urine.
The sum of all of the chemical reactions in the human body is known as the metabolism. The metabolism changes in individuals depending on a variety of different factors, such as:
- Body size – weight and height
- Body composition – amount of muscle/ fat
- Age – the metabolism tends to slow down after the age of 30
- Gender – males tend to have a slightly higher metabolism compared to females
- Health – the metabolism tends to increase if an individual has a fever, is ill or has an injury
The factors that affect metabolism are not required for the exam, but it is interesting to see what affects the metabolism of an individual