Question

1. The following skeletal formula represent D-leucine (top) and L-leucine (bottom). Which type of isomers are these two molecules? Select one: a. structural isomers b. they are not isomers c. enantiomers d. geometric isomers

Complete the following sentence: "When ionic compounds dissociate in water, each ion is surrounded by a sphere of hydration: _________ are surrounded by the partially negative charge of the water molecule's _________; _________ are surrounded by the partially positive charge of the water molecule's _________.

Select one:
a. cations, hydrogen, anions, oxygen
b. anions, oxygen, cations, hydrogen
c. elections, oxygen, cations, hydrogen
d. protons, oxygen, elections, hydrogen
e. cations, oxygen, anions, hydrogen

The plasma membrane of a cell consists of

Select one:
a. protein molecules arranged in two layers with polar areas forming the outside of the membrane.
b. two layers of lipids organized with the nonpolar tails forming the interior of the membrane.
c. lipid molecules positioned between two carbohydrate layers.
d. protein molecules with polar and nonpolar tails.

Facilitated diffusion ___ require energy and uses the help of _____

Select one:
a. does, transport proteins
b. does, cytoplasm
c. does not, transport proteins
d. does not, sodium pumps

Which is not a property of water?

Select one:
a. good solvent for electrolytes
b. high specific heat
c. adheres to polar compounds
d. contracts during freezing

Answer 1

1. The following skeletal formula represent D-leucine (top) and L-leucine (bottom). Which type of isomers are these two molecules?

ANSWER : They are enantiomers of each other. Enantiomer is a type of isomer in which both forms exist as a non superimposable mirror image of each other.

2 . Complete the following sentence:

ANSWER : When ionic compounds dissociate in water, each ion is surrounded by a sphere of hydration: CATIONS are surrounded by the partially negative charge of the water molecule's OXYGEN; ANIONS are surrounded by the partially positive charge of the water molecule's HYDROGEN.

Reason behind this is 'oppsosite charges attract each other and like charges repel each other'.

3. The plasma membrane of a cell consists of

ANSWER : two layers of lipids organized with the nonpolar tails forming the interior of the membrane

Plasma membrane is the lipid bilayer with polar heads of lipd molecule facing outward and non polar tails are directed inward of bilayer and proteins are spreaded in lipids. Some proteins are present on surface (intrinsic protein) and some are embedded in the lipd bilayer (extrinsic protein).

4. Facilitated diffusion ___ require energy and uses the help of _____

ANSWER : does not , transport protein

Facilitated diffusion the process in which solute move down the concentration gradient i.e. from region of high concentration of sloute to low concentration of solute with the help of a transport protein.

5. Which is not a property of water?

ANSWER : contracts during freezing

Maximum density of water is observed at 4⁰ C. On freezing density of water molecules starts decreasing leading to expansion of volume of water.