21. How many natural amino acids are there? a. 4 b. 10 c. 20 d. 25 22. A polypep

Question

21. How many natural amino acids are there? a. 4 b. 10 c. 20 d. 25 22. A polypeptide chain starts with a a. Amino group (N-terminal) b. Carboxyl group (C-terminal) c. R group (side chain) d. Hydroxyl group 23. The steroids in a cell membrane a. Catalyze chemical reactions b. Regulate the fluidity of the membrane Receive chemical signals Transport molecules across the membrane c. d. 24. In a protein, amino acids are joined by a. Glycosidic linkages b. Peptide bonds c. Phosphodiester bonds d. Ionic bonds

Explanation / Answer

21. There are 20 amino acids found in nature. Thus, the correct option is (c).

22. The polypeptide chain consists of many amino acids. Each polypeptide chain starts with a amino terminal or N terminal and ends with a carboxy terminal or C terminal. Thus, the correct option is (a).

23. Steroids are one of the major components of the plasma membrane of almost all cells. CholesChole is one of the main steroids found in the plasma membrane. Cholesterol prevents two phospholipid molecules from coming very close to each other and making the membrane rigid. This means that cholesterol helps maintain the fluidity of the membrane. Thus, the correct option is (b).

24. Two amino acids are joined together by the formation od a peptide bond between the carboxylic group of one amino acid and the amino group of the next amini acid. A water molecule is released in this process. Thus, the correct option is (b).

25. Phospholipids are a major constituent of the plasma membrane or the outer layer of cells in hunans. Thus, the correct option is (c).

26. The quaternary structure of proteins is formed by the interaction of two or more polypeptide chains. Thus, the correct option is (c).

27. The beta sheet is a type of secondary structure of proteins. It is formed by connecting many beta strands connected together by hydrogen bonds in order to form a sheet like structure. Thus, the correct option is (a).

28. A diasaccharide is formed by joining two monosaccharides. Among the given option, maltose is formed by joining two glucose units. Thus, the correct option is (d).

29. The major white sugar which we use is sucrose, while the major sugar present in most fruits is fructose. Thus, the correct option is (d).

30. The cell wall of almost all plants is composed of cellulose. It is also the component of plant fibers, specially cotton and is the most abundant organic polymer present on Earth. Thus, the correct option is (c).

31. Cork is an impermeable material which is formed as a part of secondary growth in plants. It is composed of a hydrophobic substance called suberin. Thus, the correct option is (b).

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