BSC1010l MIDTERM
PRACTICAL (pbsc)
1. Microscope Use:
Question: How do you correctly use a microscope to view a specimen under high
power?
Answer: Start by using the lowest magnification (4x or 10x) to locate the specimen.
Then, slowly switch to higher magnifications (40x, 100x) while adjusting the focus.
Always use the fine adjustment knob for high-power objectives to avoid damaging
the lens.
2. Cell Structure Identification:
,Question: Identify the following structures in a plant cell:
Nucleus
Cell Wall
Chloroplasts
Answer:
Nucleus: Located near the center of the cell, it controls the cell's activities and
contains genetic material.
Cell Wall: A rigid outer layer that provides structure and protection, found only in
plant cells.
Chloroplasts: Green organelles that conduct photosynthesis, giving the plant its
green color.
3. Laboratory Techniques:
Question: Describe how to prepare a wet mount slide.
Answer: Place a drop of water or solution on a clean slide. Gently place the specimen
on top, ensuring it is fully submerged in the liquid. Place a cover slip at an angle to
avoid air bubbles.
4. Osmosis and Diffusion:
Question: How would you demonstrate osmosis in the lab using a dialysis bag?
Answer: Fill a dialysis bag with a solution (e.g., sugar water), seal it, and place it in a
beaker with pure water. Over time, water will move into the bag through the semi-
permeable membrane due to osmosis, causing the bag to swell.
, 5. Titration Process:
Question: What is the purpose of titrating a solution, and how do you determine the
endpoint?
Answer: Titration is used to determine the concentration of a substance in a
solution. The endpoint is reached when the solution being titrated changes color,
indicating that the reaction is complete.
6. Chromatography:
Question: What is the principle behind paper chromatography, and how is it used to
separate pigments?
Answer: Paper chromatography separates compounds based on their solubility and
affinity for the solvent. The pigment mixture is placed at the baseline of the
chromatography paper, and as the solvent moves up, different pigments move at
different rates, separating along the paper.
7. Enzyme Activity:
Question: Explain the effect of temperature on enzyme activity.
Answer: Enzyme activity generally increases with temperature, but only up to an
optimal point. Beyond that point, the enzyme can denature and lose its function.
Extreme heat or cold can disrupt the enzyme's structure.
8. Staining Technique (e.g., Gram Staining):
Question: What are the steps involved in Gram staining, and what do the results
indicate?
Answer: The Gram staining process involves applying crystal violet, iodine, alcohol,
and safranin in succession. If the bacteria retain the crystal violet stain (purple), they
PRACTICAL (pbsc)
1. Microscope Use:
Question: How do you correctly use a microscope to view a specimen under high
power?
Answer: Start by using the lowest magnification (4x or 10x) to locate the specimen.
Then, slowly switch to higher magnifications (40x, 100x) while adjusting the focus.
Always use the fine adjustment knob for high-power objectives to avoid damaging
the lens.
2. Cell Structure Identification:
,Question: Identify the following structures in a plant cell:
Nucleus
Cell Wall
Chloroplasts
Answer:
Nucleus: Located near the center of the cell, it controls the cell's activities and
contains genetic material.
Cell Wall: A rigid outer layer that provides structure and protection, found only in
plant cells.
Chloroplasts: Green organelles that conduct photosynthesis, giving the plant its
green color.
3. Laboratory Techniques:
Question: Describe how to prepare a wet mount slide.
Answer: Place a drop of water or solution on a clean slide. Gently place the specimen
on top, ensuring it is fully submerged in the liquid. Place a cover slip at an angle to
avoid air bubbles.
4. Osmosis and Diffusion:
Question: How would you demonstrate osmosis in the lab using a dialysis bag?
Answer: Fill a dialysis bag with a solution (e.g., sugar water), seal it, and place it in a
beaker with pure water. Over time, water will move into the bag through the semi-
permeable membrane due to osmosis, causing the bag to swell.
, 5. Titration Process:
Question: What is the purpose of titrating a solution, and how do you determine the
endpoint?
Answer: Titration is used to determine the concentration of a substance in a
solution. The endpoint is reached when the solution being titrated changes color,
indicating that the reaction is complete.
6. Chromatography:
Question: What is the principle behind paper chromatography, and how is it used to
separate pigments?
Answer: Paper chromatography separates compounds based on their solubility and
affinity for the solvent. The pigment mixture is placed at the baseline of the
chromatography paper, and as the solvent moves up, different pigments move at
different rates, separating along the paper.
7. Enzyme Activity:
Question: Explain the effect of temperature on enzyme activity.
Answer: Enzyme activity generally increases with temperature, but only up to an
optimal point. Beyond that point, the enzyme can denature and lose its function.
Extreme heat or cold can disrupt the enzyme's structure.
8. Staining Technique (e.g., Gram Staining):
Question: What are the steps involved in Gram staining, and what do the results
indicate?
Answer: The Gram staining process involves applying crystal violet, iodine, alcohol,
and safranin in succession. If the bacteria retain the crystal violet stain (purple), they
