Understanding Dehydrogenase Activity in Chloroplasts

This video tutorial by Mrs. Drake covers required practical eight in A-level biology, focusing on investigating the rate of dehydrogenase activity in chloroplast extracts. It includes an introduction, aim, background, hypothesis, method, results, conclusion, and limitations. The video also provides exam questions and additional resources for further study.

What is the primary aim of the practical discussed in the video?

• To investigate the effect of a variable on dehydrogenase activity in chloroplasts

• To study the impact of light intensity on plant growth

• To measure the rate of photosynthesis in plants

• To analyze the role of chlorophyll in photosynthesis

Which chemical is used as a redox indicator in the experiment?

• Ammonium hydroxide

• NADP

• DCIP

• Chlorophyll

What is the purpose of the control test tube covered in foil?

• To show that chloroplasts are not necessary for the reaction

• To demonstrate that DCIP does not decolorize without light

• To ensure that light is not required for the reaction

• To prove that ammonium hydroxide is the only variable affecting the reaction

How is the chloroplast suspension prepared for the experiment?

• By drying and grinding spinach leaves

• By boiling spinach leaves

• By blending spinach leaves in an isotonic solution

• By freezing spinach leaves

What was the observed effect of ammonium hydroxide on the dehydrogenase activity?

• It had no effect on the reaction

• It increased the rate of reaction

• It decreased the rate of reaction

• It caused the reaction to stop completely

What is one limitation of the experiment mentioned in the video?

• The use of multiple light sources

• The subjective nature of determining the endpoint

• The lack of a control group

• The use of a non-standardized chloroplast source

Why is it important for the isolation medium to be isotonic?

• To prevent chloroplasts from bursting or shriveling

• To ensure the chloroplasts are visible

• To enhance the activity of dehydrogenase

• To increase the solubility of DCIP

What role does DCIP play in the experiment?

• It acts as a coenzyme

• It stabilizes the chloroplast suspension

• It serves as a redox indicator

• It provides electrons for the reaction

How can the subjective nature of the endpoint be improved?

• By using a different enzyme

• By increasing the light intensity

• By adding more DCIP

• By using a colorimeter

What is the consequence of not having the light-dependent reaction in plants?

• Increased production of glucose

• Inhibition of the Calvin cycle

• Unchanged ATP levels

• Enhanced chlorophyll synthesis