TNReady Review #2: LS1.3, LS1.4, LS1.5

What do adenine, cytosine, guanine, thymine, and uracil have in common?

• They are all found in RNA.

• They are all found in DNA.

• They make up the enzymes found in all organisms.

• They make up the nucleic acids found in all organisms.

Answer explanation

Adenine, cytosine, guanine, thymine, and uracil are the building blocks of nucleic acids (DNA and RNA) found in all organisms, making the correct choice about their commonality the one that states they make up nucleic acids.

Uracil is not found in DNA, and thymine is not found in RNA.

Tags

TN.BIO1.LS1.3.

Which statement correctly summarizes the relationship between DNA, proteins, and amino acids?

• The DNA molecule is a protein formed by amino acids that are linked together by peptide bonds.

• The type of protein that composes DNA codes for the twenty different amino acids.

• The sequence of amino acids in DNA determines the type of protein formed during protein synthesis.

• The sequence of nucleotides in DNA codes for specific amino acids which bond to form proteins.

Answer explanation

The sequence of nucleotides in DNA encodes specific amino acids, which then link together to form proteins. This highlights the fundamental role of DNA in protein synthesis.

Tags

TN.BIO1.LS1.3.

TN.BIO1.LS1.4.

An enzyme (catalase) is found in liver cells. Its function is to break down its substrate (hydrogen peroxide) into harmless water and oxygen.

What will happen to the enzyme (catalase) if the amount of substrate (hydrogen peroxide) keeps increasing?

• It will be used up, and the cells will be poisoned.

• It will be used up, and more of the enzyme will be produced.

• It will be denatured by the hydrogen peroxide.

• It will be reused to break down the hydrogen peroxide.

Answer explanation

The enzyme catalase will be reused to break down hydrogen peroxide. Enzymes are not consumed in the reaction; they facilitate the breakdown of substrates and can act repeatedly (be reused or recycled) as long as substrate is available.

Tags

TN.BIO1.LS1.5.

In a biology class, the students conducted an experiment using hydrogen peroxide to determine how quickly it reacted with the catalase found in potatoes. They dropped hydrogen peroxide onto a slice of a potato at different temperatures and counted how long it took for bubbles to appear on the potato. The students' data are shown in the table.

What is the optimum temperature for catalase activity?

• 15°C

• 20°C

• 25°C

• 30°C

Answer explanation

The data shows that the reaction time is shortest at 20°C, indicating that this is the optimum temperature for catalase activity, as it allows for the fastest reaction with hydrogen peroxide.

Tags

TN.BIO1.LS1.5.

The graphs show the activity of an enzyme at different pH levels and temperatures.

What can be inferred by looking at the two graphs?

• The enzyme works best at a pH of 6 and a temperature of 20°C.

• The enzyme works only at a pH of 6 and a temperature of 20°C.

• The enzyme becomes inactive at a pH of 7 and a temperature of 25°C.

• The enzyme gets completely used up at a pH of 9 and a temperature of 30°C.

Answer explanation

The graphs indicate that the enzyme exhibits peak activity at a pH of 6 and a temperature of 20°C, confirming that this is the optimal condition for its function. The enzyme will still operate at other conditions, but it will be significantly less efficient.

Tags

TN.BIO1.LS1.5.

A scientist wanted to change the color of a bird’s egg shell. She isolated the DNA of the bird and modified the section of the DNA coding for the color of the egg shell.

How will the modified section of DNA bring a change in the color of the egg shell in the bird’s offspring?

• by changing the cell membranes

• by changing the type of cell enzymes

• by synthesizing a different type of protein

• by increasing the amount of protein in the egg shell

Answer explanation

The modified DNA will lead to the synthesis of a different type of protein that determines the color of the egg shell. This change in protein composition directly affects the pigmentation, resulting in a different egg shell color.

Tags

TN.BIO1.LS1.3.

TN.BIO1.LS1.4.

The diagram shows the basic component of an important organic molecule.

This structure is the monomer for which category of molecules?

• Proteins

• Carbohydrates

• Nucleic Acids

• Lipids

Answer explanation

The structure shown is a nucleotide, which is the monomer for nucleic acids like DNA and RNA. Proteins are made of amino acids, carbohydrates from sugars, and lipids from fatty acids, making nucleic acids the correct choice.

Tags

TN.BIO1.LS1.3.

The diagram represents a portion of an organic molecule.

According to the diagram, what can be concluded about this molecule?

• The molecule is a long chain composed of smaller units; therefore, it must be a chain of fatty acids.

• The molecule contains four different nitrogen bases; therefore, it must be RNA.

• The molecule contains the nitrogen base thymine; therefore, it must be DNA.

• The molecule is composed of sugars and phosphates; therefore, it must be a molecule of ATP.

Answer explanation

The presence of thymine, a nitrogen base, indicates that the molecule is DNA, as thymine is not found in RNA. This conclusion is supported by the specific components of DNA.

Tags

TN.BIO1.LS1.3.

Which statement identifies the primary function of DNA in organisms?

• It codes for the production of proteins.

• It transports amino acids to the ribosomes.

• It serves as a source of long-term stored energy.

• It alters the activation energy of enzymes.

Answer explanation

The primary function of DNA is to code for the production of proteins, which are essential for various cellular functions and structures. The other options do not accurately describe DNA's main role.

Tags

TN.BIO1.LS1.3.

A section of DNA codes for the sequence of nitrogenous bases of mRNA to initiate protein synthesis as shown.

What process does this scenario describe?

• replication

• transcription

• translation

• transduction

Answer explanation

This scenario describes transcription, the process where a section of DNA is used to synthesize mRNA, which carries the genetic information needed for protein synthesis.

Tags

TN.BIO1.LS1.4.