UNIT 7

If a DNA molecule is 24% cytosine, how much adenine will it contain?

• 24%

• 26%

• 48%

• 52%

During DNA replication, what occurs at Step 2 in the diagram?

• The covalent bonds between sugar and phosphate molecules are broken by helicase.

• The hydrogen bonds between sugar and phosphate molecules are broken by DNA polymerase.

• The hydrogen bonds between pairs of nitrogenous bases are broken by helicase.

• The covalent bonds between pairs of nitrogenous bases are broken by DNA polymerase.

A DNA strand undergoing replication contains the bases TACGTT. Which complementary strand does it produce?

• A. AUC GAA

• B. ATG CAA

• C. ATC GAA

• D. AUC GTT

Which statement about the structure of DNA is true? CHOOSE 3.

• A. Long strands of DNA are twisted in the form of a double helix.

• B. DNA contains four different nitrogen bases including adenine, guanine, cytosine, and uracil.

• C. DNA is made of linked nucleotides which are each made of a sugar, a phosphate and a nitrogen base.

• D. DNA consists of two strands joined together by complementary base pairing.

The graph shows the effect of pH on the rate of reaction for two digestive enzymes: pepsin and trypsin. What is the best conclusion from the graph?

• Pepsin functions best in an acidic environment.

• Trypsin functions best in a basic environment.

• •  Both pepsin and trypsin function best in a basic environment.

• • Both pepsin and trypsin function best in an acidic environment.

DNA and RNA contain different nitrogenous bases. Which of the following bases is found in RNA only?

• Cytosine

• Thymine

• Guanine

• Uracil

Which of these sequences correctly describes how DNA is copied?

• Bonding of bases - separation of strands - base pairing

• Separation of strands - bonding of bases - base pairing

• Bonding of bases - base pairing - separation of strands

• Separation of strands - base pairing - bonding of bases

Estella spilled tomato sauce on her shirt. When she washed her shirt, she noticed that the detergent she used contained enzymes. Enzymes are added to detergents to break down proteins from food and other substances that may stain clothing. Which would most likely inhibit the ability of the enzymes to remove the stain on her shirt?

• the amount of dissolved minerals in the water

• the type of fibers from which her shirt was made

• the temperature of the water

• the fragrances in the detergent

Tags

NGSS.HS-PS1-5

Enzymes influence chemical reactions in living systems by

• Combining with excess hydrogen to form gaseous wastes

• Affecting the rate (speed) at which reactions occur

• Providing the substrate required for the reaction to occur

• Absorbing water released when polymers are formed

Illustration 1 shows sugar that has formed a bond by the action of an enzyme. Illustration 2 shows the enzyme, and Illustration 3 shows the enzyme after the addition of heat. What is most likely observed in Illustration 3?

• The enzyme is denatured and loses its shape.

• The enzyme forms more bonds with sugar.

• The enzyme becomes more active.

• The enzyme remains unchanged.