chapter 3

Answer  Key

Activity  1

A.       Carbohydrate                                                 E. Carrier protein

B        Glycoprotein                                                  F. Channel protein

C        phospholipids bilayer                                      G. Glycolipid

D        Cytoplasm                                                     H. Cholesterol

                                      

Activity  2

A.              Hypotonic

B.              Isotonic

C.              Hypertonic

Activity  3

1. Lipid                                          6.       Carrier protein
2. Semi-permeable                         7.       Active transport
3. Energy                                       8.       Flaccid
4. Facilitated diffusion                     9.       Turgid
5. Osmosis                                    10.     Flaccid

Assessment

A.   Objective  ( 10 marks)

       1.                    A                                               6.       C

       2.                    B                                               7.       A

       3.                    A                                               8.       B

       4.                    C                                               9.       C

       5.                    C                                               10.     D

B.   Structure  ( 8 marks)

                  

(a)     i )     Cell Q                [1]

              ii)      Cell  P             [1]

    

(b)   The cell is said  to be plasmolysed       [2]

(c)   The higher concentration of solute in solution (hypertonic solution)

 causes water to leave  the cell by osmosis.

  Both the vacuole and cytoplasm shrink and

  the plasma membrane pull away from the cell wall.

  The cell becomes flaccid.                  [3]

(d)  By placing it in  distilled  water.                [1]

C) .  Essay  (20 marks)

1.(a) Simple diffusion- Movement of molecules in gas or liquid from a region

                                                 of  higher concentration to a region  of lower

                                                 concentration                                                           [2]

                     Facilitated  diffusion- Movement of big molecules along  a concentration

                                                          gradient with the help of protein carriers across

                                                          the plasma membrane.                                      [3]

                                       Osmosis - Movement of water molecules across

                                                         a semipermeable membrane.

                                           from a region  of  lower concentration

                                               to a region  of  higher  concentration  

                                                                                                                         [3]

      

                           Active transport- Movement of particles  across plasma membrane  

                                                         against the concentration gradient with the help

                                                         of protein carriers and the presence of energy

                                                    from  ATP.                                                        [4]

(b)  

Active transport	[ 2]   Passive transport
Needs energy	Does not need energy
Movement of molecules or ions against a concentration gradient	[ 2]   Movement of water molecules along  a concentration  gradient
Takes  place through the plasma membrane of a living cell	[ 2]   Takes place through a semipeameable membrane
Needs protein carriers	[ 2]   Does not  needs protein carriers