The 'Fluid Mosaic Model' of the cell membrane was proposed in 1972 by:
A. Robertson
B. Danielli and Davson
C. Watson and Crick
D. Singer and Nicolson
Answer: Option D
Solution (By JKExamLibrary)
The Fluid Mosaic Model is the universally accepted model for the structure of the plasma membrane. It was proposed by S. Jonathan Singer and Garth Nicolson in 1972. It describes the membrane as a dynamic, fluid lipid bilayer in which globular proteins are embedded (integral) or attached to the surface (peripheral), creating a 'mosaic' pattern. The lipids and proteins can move laterally within the plane of the membrane. Danielli and Davson proposed the earlier 'sandwich model'.
Consider the following statements about biotechnology:
1. Restriction enzymes cut DNA at specific sequences.
2. Ligase joins DNA fragments.
3. PCR amplifies DNA.
Which of the above is/are correct?
Explanation:
Restriction enzymes cut DNA at recognition sites, DNA ligase seals fragments, and PCR amplifies specific DNA sequences. All three are fundamental tools in biotechnology.
Consider the following statements about enzymes:
1. Enzyme activity is affected by pH.
2. All enzymes have an optimum temperature around 37°C.
3. Enzymes are reusable.
Which of the above is/are correct?
Explanation:
Enzyme activity depends on pH and temperature; they are not consumed (reusable). Optimum temperature varies; human enzymes around 37°C, but bacterial enzymes can be higher. So 2 is not universally true.
Explanation:
Beta-carotene is a precursor of vitamin A (provitamin A) and imparts an orange color to carrots, pumpkins, and sweet potatoes. Lycopene gives red color to tomatoes, chlorophyll is green, xanthophyll is yellow. Beta-carotene is an antioxidant and is important for vision and immune function.
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