Excretion Test Answers

I am so, so sorry for being such a useless and irresponsible bio rep so far ): I'm so sorry for making all of you stay back for so long today. I'm so, so sorry!

Ms Aza is uploading the answers to Litespeed, but I'm not sure when, so here are the answers that have been compiled so far, in bright, pretty, electric blue:

BIOLOGY EXCRETION TEST ANSWERS:

Section A:

1)B
2)D
3)D
4)A
5)D

Section B:

Question 1:

A) Why is the tube coiled instead of being straight?

The tube is coiled to increase its surface area to volume ration so that the diffusion rate of the waste materials out of the blood into the dialysis fluid would be faster.

B) Why must the dialysis fluid be constantly replaced?

- For urea to be removed
- To maintain a low concentration of metabolic waste products in dialysis fluid

C) Why does the blood and dialysis fluid flow in opposite direction?

-create countercurrent flow in the system
-maintain a steep urea conc gradient between patient's blood and dialysis fluid
- increase the efficiency of urea diffusion

D) I. The human kidney

By selective reabsorption in the proximal convoluted tubules. Active transport energy is needed to reabsorb glucose and min. salts into tissue around the renal tubules. Glucose and mineral salts diffuse into blood vessels which is of a lower glucose and mineral conc.

E) II. The kidney machine

The dialysis fluid of the kidney machine has the same conc. Of glucose and mineral salts as the blood that flows through it. This ensures that no conc. Gradient for glucose and min. salt diffusion exist. Therefore, no net movement of glucose and min. salts out of the blood occurs and they are retained in the blood.

Question 3:
A) Name the fluids found in B and D.

Glomerular filtrate & urine.

B) Account for the absence of protein in B.

Proteins are too large to be filtered through the BASEMENT MEMBRANE and CAPILLARY WALLS of the glomerulus, hence they are not found.

C) Account for the absence of protein in C.

Reabsorption of glucose molecules has taken place at the proximal convoluted tubule before reaching C. All of the glucose molecules have been reabsorbed into the blood at the proximal convoluted tubule.

D) Explain the change in flow rate from B to D.

Volume of filtrate in B is larger than in D. AS filtrate pass along B and C, large amount of glucose and water has been reabsorbed, therefore the volume of filtrate is decreased, resulting in a slower flow rate.

High blood pressure is often related with increased fluid in the body. The anti-diuretic hormone, ADH, has a homeostatic function. How does high blood pressure affect ADH production?

A high blood pressure means that there is an increased volume of blood flowing through the body. The increased volume of blood means that there is a higher content of water in the blood and this causes the body to not need to reabsorb any water from the collecting duct and distal convoluted tubules, seeing as the body has more than enough water and needs to pass out as much as possible during urination to decrease blood pressure. Therefore, the pituitary gland in the brain will reduce the amount of ADH produced, because ADH will increase water reabsorption and will lead to an even higher blood pressure.

Thank you for being so patient with me. (: