K.C.S.E Biology Q & A - MODEL 1998PP1QN18

K.C.S.E Biology Q & A - MODEL 1998PP1QN18

​ A hungry person had a meal, after which the concentration of glucose and amino acids in the blood were determined. This was measured hourly as the blood passed through the hepatic portal vein and the iliac vein in the leg. The results were as shown in the table below.

(a) Using the same axes draw graphs of concentration of glucose in the heptic portal vein and the iliac vein in the leg against time
(b) Account for the concentration of glucose in the hepatic vein from:
(i) 0/1 hour
(ii) 1-2 hour
(iii) 2- 4 hours
(iv) 5 – 7 hours
(c) Account for the difference in the concentration of glucose in hepatic portal vein and the iliac vein between 2 and 4 hours.
(d) Using the data provided in the table explain why the concentration of amino acids in the hepatic portal vein took longer to increase.

answers

​(a) If axes  reversed allow  marks for identification of curves only max 2 
Correct scales
Correctly leveled axes
Curves reject broken lines for curves
(b) 0-1 hour.
i) Acc constant/low/below normal levels in blood; No/little digested foods/glucose from the intestines/gut/alimentary canal/absorption.
ii) 1-2 hours
Sharp increase in concentration of glucose in blood; (more) absorption of glucose; after digestion of the meal.
iii) 2-4 hours.
Glucose concentration declining/decreasing; less glucose being absorbed; (more) glucose being converted to glycogen in the liver/tissue/used for (tissue) respiration.
iv) 5-7 hours.
Concentration of glucose stabilizes/constant/ this is the normal glucose level concentration in the blood.
(c) The concentration of glucose in the iliac vein is lower than in the hepatic portal vein because it hasn’t been stored in the liver to be used respiration. Portal vein because most of it was stored/used up by the liver/other tissues/respiration.
(d) Proteins take longer to digest.