SPM BIology 2015

Question

6 . Diagram 6 shows the structure of a nephron and the blood vessels in human kidney.

Rajah 6 menunjukkan struktur nefron dan salur darah di dalam gingal manusia.

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(a) Based on Diagram 6, process Q occurs between the glomerulus and the Bowman’s capsule. Explain the process.

Berdasarkan Rajah 6, proses Q berlaku di antara glomerulus dan kapsul Bowman. Terangkan proses itu.

 

(b) An individual is found to have a high content of urea in his urine. Explain why.

Seorang individu didapato mempunyai kandungan urea yang tinggi dalam air kencingya. Terangkan mengapa.

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(c) Antidiuretic hormone (ADH) is involved in regulation of water. Aldosterone is involved in regulation of salt. Explain the regulation of water and salt contents in individual R and S respectively based on the following sequences:

Hormon antidiuretik (ADH) terlibat dalam kawal atur air. Aldosteron terlibat dalam kawal atur garam. Terangkan pengawalaturan kandungan air dan kandungan garam dalam individu R dan individu S masing-masing berdasarkan urutan berikut.

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    2021-02-23T11:54:42+08:00

    6.a) -Process Q is ultrafiltration.

    -The efferent arteriole has a smaller diameter compared to the afferent arteriole.

    -Thus, the blood entering the glomerulus is under high hydrostatic pressure.

    -This high pressure filters the blood, allowing small molecules to pass through the pores of the glomerulus into the Bowman’s capsule. Red blood cells and plasma proteins are large molecules thus they do not pass through the pores.

     

    b)-This might be due to a large consumption of protein.

    -Protein breakdowns to form urea. Large amounts of proteins form large amounts of urea.

    -Furthermore, urea consists of nitrogen, oxygen, carbon and hydrogen molecules.

    -The body is not able to metabolize nitrogen. Thus, excess nitrogen is removed from the body in the form of urea.

    -The liver converts excess nitrogen into urea. Urea travels through the bloodstream and gets excreted in the form of urine via the kidneys.

     

    c)-R has high blood osmotic pressure due to less water and high salt content in blood.

    Osmoreceptors found within the hypothalamus detects this increase in osmotic pressure and the posterior pituitary gland gets more stimulated to release larger amounts of ADH into the bloodstream.

    -An increase in the level of ADH results in an increase in the permeability of the distal convoluted tubule (DCT) and the collecting duct to water, this increases the reabsorption of water from filtrate into the blood.

    Furthermore, the adrenal gland gets less stimulated to release lesser amounts of aldosterone.

    -Low levels of aldosterone leads to lesser reabsorption of salt. 

    -Thus, the urine produced is concentrated and in small amounts. Blood osmotic pressure then decreases back to normal range.

     

    -S has low blood osmotic pressure due to high water and low salt content in blood.

    Osmoreceptors found within the hypothalamus detects this decrease in osmotic pressure and the posterior pituitary gland gets less stimulated to release lesser amounts of ADH into the bloodstream. 

    -A decrease in the level of ADH results in a decrease in the permeability of the DCT and the collecting duct to water, this decreases the reabsorption of water from filtrate into the blood.

    Furthermore, the adrenal gland gets more stimulated to release larger amounts of aldosterone.

    -High levels of aldosterone increases the permeability of the DCT and collecting duct to mineral salts causing higher salt reabsorption.

    -Thus, the urine produced is dilute and in large amounts. Blood osmotic pressure then increases back to normal range.

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