Chemical composition

Which of the following is true about the molecules?

• molecule X contains phosphate group while molecule Y does not contain phosphate group

• molecule X and molecule Y are carbohydrate molecules

• molecule X and molecule Y consist of carbon, hydrogen, oxygen and nitrogen

• molecule X is partially hydrophobic while molecule Y is hydrophobic

Diagram 4 shows a petri dish filled with agar containing starch. Four holes are cut in the agar and each hole is filled with substances as shown. After 30 minutes, which hole labelled A, B , C or D will be surrounded by the largest area with no starch present ?

• A

• B

• C

• D

Which of the following is not a component of nucleic acid?

• ribose

• phosphate group

• adenine

• amino acid

Which of the following statements regarding amino acids is false?

• there are 20 types of naturally occurring amino acids

• leucine is amino acids that need to be taken from diet

• 2 molecules of amino acids linked together to form dipeptide by hydrolysis

• the monomers of polypeptides

Benedict's test will come out as negative when tested with

• sucrose boiled with dilute hydrochloric acid

• sucrose boiled without dilute hydrochloric acid

• maltose boiled with dilute hydrochloric acid

• maltose boiled without dilute hydrochloric acid

Benedict's test will become positive if

• brick red precipitate is formed

• blue precipitate is formed

• copper (I) ion is oxidised to copper (II) ion

• sucrose is tested

Starch is

• a kind of monosaccharides

• a energy storage in animals

• tested by iodine test

• non-reducing sugar

The structure of proteins can be divided into four types. Which is incorrect statements about the structure ?

• Primary structure is a linear structure of amino acids

• secondary structure consists of alpha helix chain and beta pleated sheets.

• enzymes' structure is quaternary structure to form a functional and complex protein molecule

• tertiary structure is composed of helix chains or beta-pleated sheets folded or coiled into 3D shape

Which comparisons regarding saturated fats and unsaturated fats are correct? (answers may be more than 1)

• saturated: can react with additional hydrogen vs unsaturated: cannot react with additional hydrogen

• saturated: do not contain double bond vs unsaturated: contain double bond

• saturated: liquid at room temperature vs unsaturated: solid at room temperature

• example of saturated: ghee, example of unsaturated: olive oil

Which of the following is true about saturated fats as compared to unsaturated fats?

• Of vegetable origin

• They are found in butter and cheese

• Usually in liquid form at room temperature

• They have one or more double bond between their carbon atoms