Question

5) Which of the following statements about water is false?
A) Ice is more dense than liquid water.
B) Water molecules form hydrogen bonds which allow insects to walk on water.
C) Hydrogen bonds between water molecules allow water to move from roots to leaves in trees.
D) Evaporation of water from our skin allows us to cool (lower) our body temperature.

6) People who are lactose intolerant are NOT able to
A) produce milk proteins    B) produce lactose        C) digest cellulose    D) produce lactase.

7) A major type of lipid found in plasma (cell) membranes is
A) triglycerides.    B) phospholipids.        C) glycerol.        D) waxes.

8) How are genes used by cells to build proteins?
A) The genes in DNA direct the synthesis of an RNA molecule, which is used to build a protein.
B) The genes in RNA direct the synthesis of a DNA molecule, which is used to build a protein.
C) DNA is transcribed into an amino acid sequence.
D) The genes in RNA direct the synthesis of proteins directly.

Answer 1

5. Option A is the correct answer.

Ice is less dense than water. When water freezes a crystalline structure is formed which is maintained by hydrogen bonding. The orientation of hydrogen bonds push the molecules apart resulting into lower density.

6. Option D is the correct answer.

Lactase is an enzyme responsible for digestion of lactose. A lactose intolerant person cannot digest lactose because of inability to produce lactase enzyme.

7. Option B is the correct answer.

The lipids present in cell membrane is phospholipids.

8. Option A is the correct answer.

The genes present in DNA molecules direct the synthesis of mRNA via the process of transcription. mRNA contains genetic code which are used to synthesize proteins by the process of translation. This is known as central dogma of life.