Question

5. If the external ion concentration is high, cells shrink. This happens due to
____. (Explain your answer.)
a. diffusion
b. denaturation
c. osmosis
d. facilitated diffusion

6. The process by which ATP provides energy required for muscle contraction is
a. chemical reaction.
b. mechanical work.
c. transport work.
d. chemical work.

Answer 1

5. Animal and plant cells are both surounded by a selectively permeable membrane. Through this membrane some chemicals like water and oxygen can move freely acroos the membrane but other chemicals like big protein molecules and DNA are blocked by the membrane.

Osmosis is the diffusion of water through a membrane. The water always moves from a high concentration to a lower concentration. There are three cases in this-

if we place a plant or animal cell in isotonic solution where the concentration of water is same in both the cell and in the surrounding. there is no movement of water inside or outside the cell.

if we place a animal or plant cell in the hypotonic solution where the solution have more water concentration then the water moves inside the cell and cell swells up.

if we place animal cell or plant cell the hypertonic solution where the solution have more solute concentration like sugar or ion concentration and less water concentration  then water moves from a higher concentration of water inside the cell to a lower concentration outside . In this case the cell shrinks and cell loses the water.

So option c is correct.

Diffusion- Diffusion is the movement of particles from an area of higher concentration to lower concentration. In this question we are talking about the movement of water and not the particles.

So option a is incorrect.

Facilitated diffusion- Movement of some chemicals and electrical charge like sodium ions (Na⁺) or chloride ions (Cl^-) through protein channels is called facilitated diffusion. No external energy is required for this.

So option d is incorrect

Denaturation- Denaturation is the alteration of protein and nucleic acid secondary, tertiary or quaternary structure which is present in their native state by application of heat acid or alkali. After denaturation they will no longer be able to carry out its cellular function.

So option b is incorrect.

6. ATP is a nucleotide and it consists of three main structures- a adenine nitrogenous base, ribose sugar molecule; and  three phosphate groups bound to ribose. The phosphate tail of ATP is the actual power source. Bonds between the phosphates contains available energy and is and when the bond breaks, energy is released. This occurs through the addition of a water molecule. This process is called hydrolysis. It is a chemical reaction.

When outer phosphate is removed from ATP then  ATP is converted to adenosine diphosphate (ADP). Energy is released.

ATP first binds to myosin and shift it to a high-energy state. The ATP is hydrolyzed into ADP ( chemical reaction ) and inorganic phosphate with the help of enzyme ATPase. The energy released during ATP hydrolysis changes the angle of the myosin head into a “cocked” position ( this is a mechanical work ) ready to bind to actin if the sites are available. ADP and Pi remains bind. Myosin is in its high energy configuration.

So option a and b is correct and c, d is incorrect.