[Maximum number: 1]

Fig. 1.1 is a labelled diagram of a leaf palisade mesophyll cell, as seen with a high quality light microscope.

Fig. 1.1

An electron micrograph of the same leaf mesophyll cell at the same magnification would show more detail than is shown in Fig. 1.1.

(a)

In Fig. 1.1, starch granules are visible within the chloroplasts. Starch is the most common storage compound of plants. It is composed of amylopectin and amylose.

[ 1 ]

(i)

State one role of magnesium ions within chloroplasts.

[ 1 ]

[Maximum number: 1]

What is the maximum number of hydrogen bonds that can form between a single water molecule and other water molecules?

[Maximum number: 3]

Fig. 2.1 shows three molecules of water.

Fig. 2.1

(a)

Describe the hydrogen bonding that occurs between the water molecules shown in Fig. 2.1.

[ 3 ]

[Maximum number: 1]

Which type of bond does not hold together the tertiary structure of a protein?

disulfide

hydrogen

hydrophobic interactions

peptide

[Maximum number: 1]

A naturally occurring polysaccharide is a branched chain of $\alpha$ -glucose.
The straight parts of the molecule are linked by $\alpha-1,6$ glycosidic bonds with a small number of branches which are linked by either an $\alpha-1,3$ glycosidic bond or an $\alpha-1,4$ glycosidic bond.

Which polysaccharide has a structure most similar to that described?

amylopectin

amylose

cellulose

glycogen

[Maximum number: 1]

Which molecules have properties that are dependent on hydrogen bonds?
1 cellulose
2 glycogen
3 haemoglobin
4 water
A 1, 2 and 3 only B 1, 2 and 4 only C 1, 3 and 4 only D 2, 3 and 4 only

[Maximum number: 1]

The protein glutenin gives bread dough its elasticity. The diagram represents a polypeptide of glutenin.

What describes the structure of glutenin?

quaternary structure because there are both globular and fibrous regions

quaternary structure because there are both spiral and tightly coiled regions

secondary structure because the loose spiral is an $\alpha$ -helix

tertiary structure because the different regions form a 3D shape

[Maximum number: 1]

Hydrogen bonding explains many of the properties of water, including the high latent heat of vapourisation and high specific heat capacity.

For which processes in plants is hydrogen bonding in water important on hot sunny days?
1 preventing denaturation of enzymes in leaves
2 reducing water loss by evaporation
3 allowing leaves to cool down quickly at night
4 holding the column of water in xylem vessels together

1, 2, 3 and 4

1, 2 and 4 only

1, 3 and 4 only

2 and 3 only

[Maximum number: 1]

The diagram represents roles of water in living organisms.

Which roles are dependent upon hydrogen bonds between water molecules?

1, 2 and 3

1 and 2 only

1 and 3 only

2 and 3 only