The Fluid Mosaic Model of the cell membrane was proposed by which scientists?
A. Watson and Crick
B. Robertson and Danielli
C. Singer and Nicolson
D. Schleiden and Schwann
Answer: Option C
Solution (By JKSSB Mock Tests)
The Fluid Mosaic Model of the plasma membrane was proposed by S. Jonathan Singer and Garth Nicolson in 1972. It describes the cell membrane as a dynamic, fluid structure composed of a phospholipid bilayer with globular proteins embedded or attached, moving laterally within the lipid matrix.
Explanation:
Pleiotropy is a phenomenon where a single gene influences multiple, seemingly unrelated phenotypic traits. Phenylketonuria (PKU) is an autosomal recessive metabolic disorder caused by a mutation in a single gene (PAH) that codes for the enzyme phenylalanine hydroxylase. This single mutation leads to multiple effects: intellectual disability, reduced hair and skin pigmentation, and musty odor.
Consider the following statements about vitamins:
1. Vitamin C deficiency causes scurvy.
2. Vitamin D deficiency causes beriberi.
3. Vitamin A deficiency causes night blindness.
Which of the above is/are correct?
Explanation:
Scurvy is vitamin C deficiency; night blindness is vitamin A deficiency. Beriberi is due to vitamin B₁ deficiency, not D. So 1 and 3 are correct.
Consider statements about microorganisms: 1. Bacteria reproduce by binary fission. 2. Viruses have their own metabolic machinery. 3. Fungi have a cell wall made of chitin. Which are correct?
Explanation:
Bacteria are prokaryotes that primarily reproduce asexually through binary fission, where a single cell divides into two identical daughter cells. Fungi are eukaryotes characterized by having cell walls primarily composed of chitin, a tough polysaccharide. Viruses lack cellular structure and metabolic machinery; they are obligate parasites that rely entirely on the host cell's machinery for replication. Thus, statements 1 and 3 are correct.
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