Certainly! Let's go through each question step-by-step.
### Question 2.1: What percentage of urea was found in the urine?
To determine the percentage of urea found in the urine, we refer to the percentage composition given in the table for the substance 'Urea' under the 'In urine (%)' column.
According to the table:
- The percentage of urea in the urine is 200%.
So, the answer for 2.1 is:
200%
### Question 2.2: Explain why there are no proteins in the filtrate.
In question 2.2, we need to explain why proteins are not present in the filtrate. The concept to understand here involves the structure and function of the kidney, specifically the filtration mechanism in the glomerulus.
- Proteins are large molecules: Proteins are large biomolecules that have complex structures and relatively high molecular weights compared to other substances found in the blood.
- Filtration membrane: The filtration process in the kidneys occurs in the glomerulus, where blood is filtered through a semipermeable membrane. This membrane allows small molecules like water, salts, and urea to pass through but not larger molecules.
- Size exclusion: Due to their large size, proteins cannot pass through the tiny pores of the glomerular membrane. Essentially, the physical size of protein molecules prevents them from being filtered out of the blood into the filtrate.
- Selective permeability: The selective nature of the kidney's filtration membrane ensures that essential large molecules like proteins remain in the bloodstream, contributing to maintaining osmotic balance and other critical functions.
In summary, there are no proteins in the filtrate because proteins are large molecules that cannot pass through the filtration membrane in the kidneys. Therefore, they are not present in the filtrate.
So, the answer for 2.2 is:
Proteins are large molecules that cannot pass through the filtration membrane in the kidneys. Therefore, they are not present in the filtrate.
This concludes the step-by-step solution for the given questions.
