Question

Which substance is in higher concentration in blood than in glomerular filtrate?
A. Water
B. Glucose
C. Urea
D. Plasma proteins

Answer 1

Hint: The substance present in glomerular filtrate are plasma proteins, water, glucose and urea. The plasma proteins are relatively larger in size. Therefore, they are unable to pass through the minute pores (filtration slits) that are present in Bowman's capsule and stay in blood only.

Complete answer:
Option A- water
The amount of filtrate is very large. It is about 45 gallons per day in an adult human.
Therefore, both lipid-soluble and polar substances pass through the glomerulus into the tubule filtrate and about 99% of the water-like filtrate, small molecules, and lipid-soluble substances, are reabsorbed.

Option B- Glucose
Glucose is present in both blood plasma and glomerular filtrate. It is present in urine (normally) because the glucose is selectively reabsorbed in the proximal convoluted tubule. The reabsorption occurs from the filtrate into the blood by active transport.

Option C- urea
Urea is present in blood plasma, glomerular filtrate, and urine. The glomerular filtrate normally contains water, glucose, salts, and urea. All these enter the Bowman's capsule in nearly the same concentrations as they have in the blood and only approx 50% of urea is reabsorbed. The concentration of urea in the urine depends on the amount of water in the urine.

Option D- Plasma proteins
The first step known in the production of urine is the filtration of plasma passing through the kidney. This filtration takes place from the glomerular capillaries into the Bowman's capsule to form tubular fluid.
The glomerular filter prevents these plasma proteins from passing into the nephrons but is permeable to all other plasma constituents like ions, glucose, amino acids, urea, etc.

So, option D is correct - Plasma proteins.

Note: As we said Glomerular filtration is the first step in urine formation. It comprises the basic physiologic function of the kidneys. It illustrates the process of blood filtration in the kidney. In this process fluid, ions, glucose, and waste products are eliminated from the glomerular capillaries.