Need help with these two:
26. Why do plant cells contain both choroplasts and mitochondria?
a. in the light, plants are photosynthetic autotrophs. In the dark, they are heterotrophs.
b. if plants can't produce enough ATP to make sugars during photosynthesis, they can produce it during cellular respiration
c. Sugars are produced in chloroplasts during photosynthesis. These sugars can be stored in the plan for later use during cellular respiration
d. The leaves, and sometimes, the stems of plants contain chloroplasts while the roots of plants contain mitochondria.
27. Which of the following is true for both aerobic and anaerobic respiration?
a. ATP is produced during glycolysis
b. Pyruvate is broken down to ethanol or lactate
c. the electron transport chain pumps hydrogen ions across a membrane
d. An organic hydrogen acceptor recycles NAD+
Thanks
-MC
26. The correct answer is option c. Sugars are produced in chloroplasts during photosynthesis. These sugars can be stored in the plant for later use during cellular respiration.
To understand why plant cells contain both chloroplasts and mitochondria, let's break it down:
Chloroplasts are responsible for photosynthesis, the process by which plants convert sunlight, carbon dioxide, and water into glucose (sugar) and oxygen. This process occurs in the presence of light and takes place in the chloroplasts found in the leaves and sometimes stems of plants.
On the other hand, mitochondria are known as the powerhouses of the cell. They are responsible for cellular respiration, the process that generates ATP (adenosine triphosphate) from glucose. ATP is the molecule that provides energy for various cellular activities.
While plants primarily use chloroplasts for photosynthesis during the day when there is sunlight, they also need energy at night or in periods of low light. This is where cellular respiration comes in. During cellular respiration, the stored sugars produced during photosynthesis in the chloroplasts are broken down in the mitochondria to generate ATP, which the plant can use as energy.
Therefore, the presence of both chloroplasts and mitochondria in plant cells allows them to perform photosynthesis during the day, storing energy in the form of sugars, and then utilize those stored sugars for ATP production during cellular respiration when needed.
27. The correct answer is option a. ATP is produced during glycolysis.
Now, let's explore why this statement is true for both aerobic and anaerobic respiration:
Glycolysis is the first stage of cellular respiration, regardless of whether it is aerobic (with oxygen) or anaerobic (without oxygen). It takes place in the cytoplasm of cells and involves the breakdown of glucose into two molecules of pyruvate.
During glycolysis, a small amount of ATP is produced. This ATP generation occurs through a series of enzymatic reactions where glucose is converted into smaller molecules, releasing energy in the process. Some of this energy is used to convert ADP (adenosine diphosphate) into ATP.
In both aerobic and anaerobic respiration, glycolysis is the same initial step. However, the subsequent processes differ:
- In aerobic respiration, the pyruvate molecules produced during glycolysis are further broken down in the mitochondria through additional biochemical reactions. This breakdown ultimately yields a significant amount of ATP through the Krebs cycle and oxidative phosphorylation, which occur in the mitochondria. Oxygen plays a crucial role in these subsequent stages of aerobic respiration.
- In anaerobic respiration, which occurs in the absence of oxygen, the pyruvate molecules are converted into other compounds such as ethanol (as in yeast and some bacteria) or lactate (as in animal muscle cells). This conversion allows the recycling of other molecules involved in glycolysis but does not generate significant amounts of ATP like aerobic respiration does.
In summary, while both aerobic and anaerobic respiration start with glycolysis and produce some ATP, the subsequent stages differ depending on the presence or absence of oxygen, leading to different final outcomes in terms of energy production.
26. The correct answer is c. Sugars are produced in chloroplasts during photosynthesis. These sugars can be stored in the plant for later use during cellular respiration.
Explanation: Plant cells contain both chloroplasts and mitochondria because they need both organelles for different functions. Chloroplasts are responsible for photosynthesis, which is the process by which plants use sunlight to convert carbon dioxide and water into glucose (sugars) and oxygen. However, plants cannot perform photosynthesis all the time, such as in the dark or during winter. Therefore, they need to store the sugars produced during photosynthesis for later use.
Mitochondria, on the other hand, are responsible for cellular respiration, which is the process by which cells convert glucose and oxygen into ATP (adenosine triphosphate), the energy currency of the cell, carbon dioxide, and water. These mitochondria will break down the stored sugars from chloroplasts into ATP when needed, providing energy for various cellular processes.
27. The correct answer is a. ATP is produced during glycolysis.
Explanation: Both aerobic (with oxygen) and anaerobic (without oxygen) respiration involve glycolysis, which is the initial step of cellular respiration. During glycolysis, glucose is broken down into two molecules of pyruvate, and a small amount of ATP is produced. This process occurs in the cytoplasm of the cell and is common to both aerobic and anaerobic respiration.
The other options are specific to either aerobic or anaerobic respiration:
b. Pyruvate is broken down to ethanol or lactate: This is true for anaerobic respiration. In the absence of oxygen, pyruvate can be converted into either ethanol (in yeast and some bacteria) or lactate (in muscle cells).
c. The electron transport chain pumps hydrogen ions across a membrane: This is true for aerobic respiration. In aerobic respiration, the electron transport chain is located in the inner membrane of the mitochondria. It uses the high-energy electrons from the breakdown of glucose to pump hydrogen ions across the membrane, generating a proton gradient that is used to produce ATP.
d. An organic hydrogen acceptor recycles NAD+: This is true for anaerobic respiration. In anaerobic respiration, NAD+ is necessary for the continuation of glycolysis. Since glycolysis produces a limited amount of ATP, it needs a way to regenerate NAD+ for it to continue. An organic hydrogen acceptor, such as ethanol or lactate, can act as a final electron acceptor and recycle NAD+ to keep glycolysis going.