Question

QUESTION 13

1. The movement of water across the cell membrane

   		is determined by the concentration of water on either side of the membrane.
   		is determined by the concentration of solutes on either side of the membrane.
   		may cause the cell to shrink or swell and even burst.
   		All statements are true.

1.2 points   

QUESTION 14

1. What are the main components of a cell membrane?

   		carbohydrates and proteins
   		phospholipids and proteins
   		nucleic acids and carbohydrates
   		carbohydrates and phospholipids

1.2 points   

QUESTION 15

1. Which of the following best describe the process of diffusion?

   		the movement of materials up the concentration directly through the cell membrane
   		the movement of materials down the concentration gradient assisted by proteins and powered by ATP
   		the movement of materials down the concentration gradient either directly through the membrane or though protein channels in the membrane
   		the movement of materials up the concentration gradient driven by kinetic energy i.e. the random movement of molecules

Answer 1

Ans 13) the movement of water across the cell membrane is called Osmosis.

Osmosis is the movement of solvent from a region of lower concentration to higher concentration. The higher or lower concentration means the solute concentration. The solution have lower solute is lower concentration but it had high water potential (solvent) while solution having high amount of solute is called higher concentration and the water has low water potential. So, the movement always occurs from high water potential, lower concentration to low water potential, high concentration. Osmosis occurs via a semi-permeable membrane mean osmosis always occurs through a membrane.

Example = raisin when dipped in water swell up due to low concentration in water and high in raisin so water moves into the raisin resulting in swelling. This is also called hypotonic solution, hypo= less, tonic = concentration.cell swell in this case.

While when raisin are prepared from grapes they are generally put in high concentration sugar solution so movement of water occurs from raisin to sugar solution. This is called hypertonic solution. Cell shrink in this case.

So, Accordingly correct answer is Option D, all are true.

Ans 14) main components of cell membrane are :

Phospholipid, glycolipids, cholesterol and proteins.

Correct answer Option b, phospholipids and proteins.

Ans 15) Diffusion -- it is movement of particles from a region of higher concentration to lower concentration without the expenditure of energy. It is also called downhill transport as movement occurs from higher concentration region to lower concentration region. It can occur directly through membrane or through protein channels in the membrane.

So, correct answer is Option C, movement of materials down the concentration gradient either directly through the membrane or through protein channels in the membrane.