1.
Oxygen is so essential to your life that you would die within minutes if you were deprived of it. But why? Explain in detail. Include the following in your answer.- Which critical process is oxygen required for? (1 pt)
- What is the ultimate purpose of that process? (1 pt)
- What exactly does oxygen do in this process? (1 pt)
- Why is oxygen well-suited to this task (as opposed to other elements)? (1 pt)
2.
Describe the process of endosymbiosis in a series of NUMBERED steps. (3 pt)
3.
Explain how enzyme function is similar to a lock-and-key. Use and CAPITALIZE the words:- SUBSTRATE(1 pt)
- ACTIVE SITE(1 pt)
- ACTIVATION ENERGY(1 pt)
- CATALYST(1 pt)
You are welcome to submit your answer in the form of a labelled sketch on the scrap paper provided. (Be sure to write your name.) You may also type your answer in the space provided here.
4.
Which of the following is an example of a cell moving something across its membrane in a way that requires energy.
Correct Answer
C. Ions pumped out of a nerve cell from an area of low concentration to an area of high concentration
Explanation
Ions being pumped out of a nerve cell from an area of low concentration to an area of high concentration requires energy because it is going against the concentration gradient. This process is known as active transport, which involves the use of cellular energy (usually in the form of ATP) to move molecules or ions across the cell membrane.
5.
If you place a red blood cell into an hypertonic solution, which of the following is most likely to occur.
Correct Answer
C. The cell is likely to shrivel up as water leaves the cell and flows into the hypertonic solution.
Explanation
When a red blood cell is placed in a hypertonic solution, the concentration of solutes outside the cell is higher than inside the cell. This creates a concentration gradient that causes water to move out of the cell through osmosis. As a result, the cell loses water and shrivels up. Therefore, the correct answer is that the cell is likely to shrivel up as water leaves the cell and flows into the hypertonic solution.
6.
Which phrase best describes the effect of a catalyst on a chemical reaction?
Correct Answer
D. Decreases the activation energy
Explanation
A catalyst is a substance that speeds up a chemical reaction by lowering the activation energy required for the reaction to occur. By decreasing the activation energy, a catalyst allows the reactants to overcome the energy barrier more easily, leading to an increased reaction rate. Therefore, the correct answer is "decreases the activation energy."
7.
Which of the following is NOT true of enzymes.
Correct Answer
D. They must be rebuilt after each use.
Explanation
Enzymes are specialized proteins that act as catalysts in biological reactions. They lower the activation energy required for a reaction to occur, thereby increasing the reaction rate. Enzymes can also undergo conformational changes, allowing them to bind to substrates and facilitate the reaction. However, enzymes do not need to be rebuilt after each use. They can be reused multiple times as they are not consumed in the reaction and remain unchanged at the end of the reaction.
8.
What would the complementary strand of DNA be to the following sequence of bases? TTGCGCA
Correct Answer
D. AACGCGT
Explanation
The complementary strand of DNA is formed by pairing each base with its complementary base. In DNA, adenine (A) pairs with thymine (T) and cytosine (C) pairs with guanine (G). Therefore, the complementary strand of the given sequence TTGCGCA would be AACGCGT.
9.
Which of the following does NOT occur as part of DNA replication?
Correct Answer
B. A molecule of messenger RNA (mRNA) is assembled by an enzyme called RNA polymerase.
Explanation
During DNA replication, an enzyme called DNA helicase unzips the DNA double helix, separating the two strands. Then, an enzyme called DNA polymerase helps in assembling a new complementary strand for each of the original strands, using them as templates. This process ensures that each daughter strand contains a template from the parent strand. Additionally, free nucleotides are attracted to the exposed nucleotides within the replication bubble, allowing for the formation of the new DNA strands. However, the assembly of mRNA by an enzyme called RNA polymerase is not a part of DNA replication. mRNA is synthesized during a process called transcription, which occurs after DNA replication.
10.
How many mRNA bases would it take to covey the code for 10 amino acids?
Correct Answer
E. 30
Explanation
To convey the code for 10 amino acids, each amino acid requires a sequence of three mRNA bases. Since there are 10 amino acids, the total number of mRNA bases needed would be 10 x 3 = 30.
11.
Which of the following occurs at the ribosome?
Correct Answer
A. Translation
Explanation
Translation occurs at the ribosome. During translation, the ribosome reads the mRNA molecule and uses the information to assemble a specific sequence of amino acids, forming a protein. This process involves the interaction of transfer RNA (tRNA) molecules, which carry the amino acids, with the mRNA. The ribosome acts as the site where the tRNA molecules bind to the mRNA and bring the amino acids together to form the protein chain. Therefore, translation is the correct answer as it specifically describes the process that occurs at the ribosome.
12.
Which molecule stores readily usable energy for the cell?
Correct Answer
A. ATP
Explanation
ATP (adenosine triphosphate) is the molecule that stores readily usable energy for the cell. It is often referred to as the "energy currency" of the cell because it provides the energy needed for various cellular processes. ATP is produced during cellular respiration and can be quickly broken down to release energy when needed. This energy is used for activities such as muscle contraction, active transport, and synthesis of molecules. Sugar, ADP, oxygen, and carbon dioxide are not molecules that directly store energy in the same way as ATP does.
13.
Which of the following correctly show the products of photosynthesis?
Correct Answer
C. Sugar and oxygen
Explanation
The products of photosynthesis are sugar and oxygen. During photosynthesis, plants use carbon dioxide and water to produce glucose (sugar) and release oxygen as a byproduct. This process occurs in the chloroplasts of plant cells, where sunlight is converted into chemical energy in the form of ATP. The ATP and enzymes mentioned in the options are involved in the process of photosynthesis, but they are not the direct products. The last option mentioning carbon, hydrogen, nitrogen, and oxygen is incorrect as it refers to the elements involved in photosynthesis, not the actual products.
14.
Which statement best captures the purpose of cellular respiration?
Correct Answer
D. To transfer energy from sugar to ATP
Explanation
The purpose of cellular respiration is to transfer energy from sugar to ATP. This process involves breaking down food and converting it into carbon dioxide and water, but the main objective is to generate ATP, which is the primary energy currency of cells.
15.
In which process is lactic acid formed when there is not enough oxygen present for cellular respiration to take place?
Correct Answer
D. Fermentation
Explanation
Fermentation is the process in which lactic acid is formed when there is not enough oxygen present for cellular respiration to occur. During fermentation, glucose is broken down into lactic acid, which helps to generate energy in the absence of oxygen. This process is commonly observed in certain bacteria and yeast, as well as in muscle cells during strenuous exercise when oxygen supply is limited.
16.
Which needs oxygen to take place?
Correct Answer
B. The movement of electrons in the electron transport chain
Explanation
The movement of electrons in the electron transport chain requires oxygen. This process occurs in the mitochondria of cells and is a crucial step in cellular respiration. During the electron transport chain, electrons are passed along a series of protein complexes, creating a flow of energy that is used to generate ATP. Oxygen is the final electron acceptor in this chain, and its presence is necessary to maintain the flow of electrons and produce ATP efficiently. Without oxygen, the electron transport chain cannot proceed, leading to a decrease in ATP production and potentially causing cellular dysfunction.
17.
The bacterium shown in this figure may have evolved into a mitochondrion after going through the process of
Correct Answer
C. Endosymbiosis
Explanation
The bacterium shown in the figure may have evolved into a mitochondrion after going through the process of endosymbiosis. Endosymbiosis is a process where one organism lives inside another and both organisms benefit from the relationship. In this case, it is believed that mitochondria, which are organelles responsible for energy production in cells, were once free-living bacteria that were engulfed by another cell. Over time, they formed a mutually beneficial relationship, with the host cell providing protection and nutrients, while the mitochondria provided energy through respiration. This theory is supported by the similarities between mitochondria and bacteria, such as their own DNA and ability to divide independently.
18.
Scientists hypothesize that cyanobacteria changed the early Earth by
Correct Answer
A. Adding oxygen to the atmosphere
Explanation
Cyanobacteria are known to be the first organisms capable of photosynthesis, which involves converting sunlight, water, and carbon dioxide into glucose and oxygen. As cyanobacteria proliferated and performed photosynthesis, they released large amounts of oxygen into the atmosphere. This increase in atmospheric oxygen had a profound impact on the early Earth, leading to the development of aerobic organisms and the formation of the ozone layer. Therefore, the correct answer is adding oxygen to the atmosphere.
19.
Which of the following best describes what is meant by the Cabrian Explosion.
Correct Answer
D. An explosion in the number of animal species
Explanation
The Cambrian Explosion refers to a period in Earth's history, around 541 million years ago, when there was a sudden and rapid diversification of animal species. It was a time when a wide variety of complex organisms, including the first appearance of many major animal groups, emerged in the fossil record. This event marked a significant increase in the number and diversity of animal species, making the answer "an explosion in the number of animal species" the most accurate description of the Cambrian Explosion.
20.
Which of the following best describes the diversity of life over time on Earth?
Correct Answer
D. Overall biodiversity increases, but it is interrupted by major extinction events
Explanation
Overall, the diversity of life on Earth has increased over time. However, this increase is not constant and is interrupted by major extinction events. These extinction events cause a significant loss of species, reducing biodiversity temporarily. Nonetheless, over the long term, new species evolve and diversify, leading to an overall increase in biodiversity.
21.
Refer to the graph from the previous question. What key event in life's history is represented by the steep slope of the line labeled A.
Correct Answer
A. Cambrian explosion
Explanation
The steep slope of line A on the graph represents a rapid increase in the number of species over a relatively short period of time. This event is known as the Cambrian explosion, which occurred approximately 541 million years ago. During this time, there was a significant diversification of complex organisms, including the appearance of many major animal phyla. The Cambrian explosion marked a crucial point in the history of life on Earth, as it led to the establishment of the diverse and complex ecosystems that we see today.