Hydrogen bonding has many important roles in organisms. State and explain the importance of hydrogen bonding for the specific heat capacity of water and for the latent heat of vaporisation of water.

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3(b)Plant Structure TransportMedium3 marks

Describe and explain the role of hydrogen bonding in the movement of water in xylem vessels in plants.

Answer

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3(c)Dna Structure ReplicationEasy3 marks

Figure 3.1 shows part of a DNA molecule. The four bases in Figure 3.1 are labelled W, X, Y and Z.

Figure 3.1, part of a DNA molecule showing two base pairs joined by hydrogen bonds shown as dashed lines: base W, drawn as a single six-membered ring, paired to base X, drawn as a fused two-ring shape, by two hydrogen bonds; and base Y, drawn as a single six-membered ring, paired to base Z, drawn as a fused two-ring shape, by three hydrogen bonds; each base attaches to a five-membered sugar ring and a phosphate group forming the backbone.

State the names of bases W, X, Y and Z in Figure 3.1.

W, X, Y and Z

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3(d)Proteins Amino AcidsEasy3 marks

Table 3.1 lists three types of interaction that maintain the shape of protein molecules. For each interaction, select the structural level or levels — primary, secondary or tertiary — that it can affect.

Hydrogen bonds

Hydrophobic interactions

Ionic bonds