Homework answers / question archive / Answer all questions in the spaces provided on the assignment paper

Answer all questions in the spaces provided on the assignment paper

Biology

Share With

---

1. Answer all questions in the spaces provided on the assignment paper.
2. Under no circumstances should you remove the questions and DO NOT CHANGE THE FONT OF THE ASSIGNMENT
3. Marks allocated should serve as a guide to the depth of the answer
4. Students are advised, where possible, to collaborate online in their groups
5. Students may, if they so wish, also submit a hard copy by sliding it under my door. However under all circumstances all Covid 19 protocols should be observed.
6. Please send me an email if you have also submitted a hard copy.
7. Make sure you also include your student number
8. Pasting and copying from a source will result in a zero (0) mark.
9. Submit your assignment as a PDF file

 

QUESTION 1                                                                                                                         [14]

(a)        Calculate the surface area-to-volume ratio of a cube 4 mm and a cube 8 mm.                      (8)

___________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

(b)        What is the significance of a large surface area-to-volume ratio for a cell?                (2)

__________________________________________________________________________________________________________________________________________________________________________

(d)        Which exact type of microscope would you use to study

(i)         changes in shape of a living human white blood cell?                                                 (1)

_______________________________________________

(ii)        details of surface texture of a human hair?                                                                 (1)

_______________________________________________

(iii)       detailed structure of an organelle of a human liver cell?                                                        (1)

_______________________________________________

(e)        Cyanide binds with at least one of the molecules involved in the synthesis of ATP. Following exposure of a cell to cyanide, most of the cyanide would be expected to be found in the

A.        ribosome          B.         mitochondria   C.         lysosome         D.        peroxisomes

Answer ____                                                                                                                           (1)

 

 

 

QUESTION 2                                                                                                                         [15]

 

          Mammalian red blood cells are sensitive to a change in salt concentration of the external environment. If they are transferred from plasma to a less concentrated solution they swell. If they swell sufficiently they burst, in which case they are said to be haemolyzed. In an experiment to find the percentage of human red blood cells haemolyzed at different concentrations, the following results were obtained:

 

Salt concentration (g/l)	% red blood cells haemolyzed
3.2	100
3.4	97
3.6	81
3.8	53
4.0	30
4.2	13
4.4	3

 

(a)     Plot the results on a graph paper, making sure the dependent variable is on the vertical axis. The graph should be drawn on a graph paper (a freehand graph) which has to be scanned and submitted with the assignment as an attachment                                                                                    (5)

 

(b)     Explain why red blood cells swell and burst when placed in a dilute salt solution                     (2)

__________________________________________________________________________________________________________________________________________________________________________

 

(c)     Explain why a plant cell does not burst under the same situation as in 2 above             (2)

__________________________________________________________________________________________________________________________________________________________________________

 

(d)     At what concentration is the proportion of haemolyzed to non-haemolyzed cells equal?

          Indicate your answer clearly on the graph__________                                                  (2)

         

(e)     Amoeba is a protest that lives in freshwater. What osmotic problem(s) are faced by a unicellular organism like and how does it overcome them?                                                                (3)

_______________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

 

(e)        How do marine organisms osmotically adapt to living in an environment which has such a high salinity?                                                                                                                                    (1)

_____________________________________________________________________________________

 

 

QUESTION 3                                                                                                                         [10]

A range of concentrations of sucrose solutions is used to find the concentration of the solution which causes no change in weight or size of tissue immersed in it. The result of such an investigation are given in the figure below:

 

 

1. Write down the solute concentration of the potato chip._____________                                (1)

Explain__________________________________________________________________________________________________________________________________________________________         (2)

2. What is happening to te cells in the sucrose solution of 0.3 M? Explain.                                 (2)

_____________________________________________________________________________________

3. What is happening to te cells in sucrose solution of 0.8 M? Explain                            (2)

_____________________________________________________________________________________

The turgidity of tissue immersed in solutions can be demonstrated as follows: Identical potato chips are left in (A) water and in (B) 20% sucrose solution                                                                        (3)

    

 

  A: Water                                           B: 20% Sucrose

 

 

            Potato                                        Potato                                                                                                                                                                      p                                                                     

 

 

 

Which of the two is still turgid? ___________________

Explain___________________________________________________________________________________________________________________________________________________________________

 

 

QUESTION 4                                                                                                                         [11]

(a)        Two molecules that pass through the lipid bilayer without the help of proteins are O₂ and CO₂. What properties allow this to occur?                                                                                     (2)

__________________________________________________________________________________________________________________________________________________________________________

(b)        The stomach has two types of exocrine cells: the chief cells, which secrete an inactive form of the protein-digesting enzyme pepsinogen, and the parietal cells, which secrete hydrochloric acid (HCl) that activates pepsinogen. Both cell types have an abundance of mitochondria for ATP production- the chief cells need energy to synthesize pepsinogen, and the parietal cells need energy to transport hydrogen ions. (H⁺) and chloride ions (Cl^-) from the blood into the stomach lumen. Only one of these cell types has an extensive rough endoplasmic reticulum and abundant Golgi stacks.

Would this be the chief cells or the parietal cell? ___________________________              (1)

Why?                                                                                                                                       (2) __________________________________________________________________________________________________________________________________________________________________________

4. Colostrum, the first milk that a mother produces, contains an abundance of antibodies, large protein molecules. These maternal antibodies help protect the breast-fed infants from infections until the babies are capable of producing their own antibodies, By what  means would you suspect these maternal antibodies are transported across the cells lining a newborn’s digestive tract into the bloodstream? Name the means and explain                                                                                                                                    (3)

_______________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

(e)        Which of the following methods of transport is being used to transfer these substrate into the cell in the accompanying graph?                                                                                                  (3)

 

 

A         diffusion down a concentration gradient

B          osmosis

C          active transport

D         vesicular transport

E          it is impossible to tell with the information provided

 

Answer: ________________________________________

Explain:___________________________________________________________________________________________________________________________________________________________________