STPM Biology 2019 Term 1 MCQ

Which molecule property is important to aquatic organisms during winter?

• Low viscosity

• Strong viscosity

• More dense in liquid form

• High specific heat capacity

A general statement about cholesterol and carbohydrate is given. Which are true about the statement?

I Contain hexose sugars

II Contain carboxyl group

III Contain hydroxyl groups

IV Contain pentagon rings in their molecular structures

• I and II

• I and III

• II and IV

• III and IV

Which common structures are found in prokaryotes and eukaryotes?

I Cell wall

II Microtubule

III Mitochondrion

IV DNA associated with protein

• I and II

• I and III

• II and IV

• III and IV

A new plant species has a unique photosynthetic pigments. The leaves of the plant appeared

to be orange in colour. Which visible lights are not absorbed by the photosynthetic pigments

of the plant?

• Red and yellow

• Green

• Red and Blue

• Green, blue and violet

Washing silk garment at temperature above 65°C will cause it to crumple because _______.

• the tertiary structure of silk is destroyed at high temperature

• silk is made up of protein which denatures at high temperature

• water reacts with polar amino acids of the silk at high temperature

• hydrogen bonds, peptide bonds, disulphide bridges and Van der Waals forces break at

  high temperature

Answer explanation

Silk is a fibrous protein. High temperatures will reduce the strength of the hydrogen bonds and disrupt the structure, thus denaturation of the protein occurs.

Molecule X has the following characteristics:

• The length of the molecule is 80 nucleotides

• The 3D structure of the molecule is an L-shaped

• The presence of hydrogen bond in between adenine and uracil

• The complementary base pairing of the molecule is at the antiparallel part

What is molecule X?

• DNA

• mRNA

• rRNA

• tRNA

Why there is no sedimentation of the membrane fragments after homogenising liver tissue and fractionating it using an ultracentrifugation?

• It has a high S value.

• It has the smallest mass.

• It is the smallest organelle.

• Its density is higher than that of water.

Answer explanation

The particles with smaller mass experience less sedimentation force in a centrifugal field. In ultracentrifugation, particles sediment based on their mass and density, and smaller particles may experience less sedimentation compared to larger, denser particles. Membrane fragments have the smallest mass, leading to the most reduced sedimentation forces, thus no sediments.

The characteristics of a type of plant cells are given below.

• The cells are longitudinal and vary in size.

• The mature cells lack of nuclei and cytoplasm.

• The secondary cell walls are thickened with lignin.

Which specialised plant cell has the characteristics above?

• Collenchyma

• Parenchyma

• Sclerenchyma

• Tracheid

Which is not true about an enzyme immobilisation technique?

I The product needs to be purified.

II The cost of operation is expensive.

III The immobilised enzyme can be reused.

IV The technique helps to stabilise the enzyme.

• I and II

• I and IV

• II and III

• III and IV

Which stage of the Krebs cycle involves the reduction of FAD?

• The conversion of α-ketoglutarate to succinyl CoA

• The conversion of isocitrate to α-ketoglutarate

• The conversion of malate to oxaloacetate

• The conversion of succinate to fumarate