2. Biological Molecules

Question 1

describe and carry out the Benedict’s test for reducing sugars

Question 2

the iodine test for starch

Question 3

the emulsion test for lipids

Question 4

the biuret test for proteins

Question 5

describe and carry out a semi quantitative Benedict’s test on a reducing sugar solution by standardising the test and using the results (time to first colour change or comparison to colour standards) to estimate the concentration

Question 6

describe and carry out a test to identify the presence of non-reducing sugars, using acid hydrolysis and Benedict’s
solution

Question 7

describe and draw the ring forms of α-glucose and β-glucose

Answer 7

α-glucose- OH down on 1st carbon
β-glucose- OH up on 1st carbon

Question 8

define the terms monomer, polymer, macromolecule, monosaccharide, disaccharide and polysaccharide

Answer 8

monomer-
polymer-
macromolecule-
monosaccharide-
disaccharide-
polysaccharide-

Question 9

types of monosaccharide, disaccharide and polysaccharide

Answer 9

monosaccharide-
pentose (5C)- ribose, deoxyribose
hexose (6C)- glucose, fructose, galactose

disaccharide-
maltose- 2 alpha glucose
sucrose- alpha glucose + b fructose
lactose- alpha glucose + galactose

polysaccharide- starch, glycogen, cellulose

Question 10

state the role of covalent bonds

Answer 10

joining smaller molecules together to form polymers

Question 11

types of reducing and non-reducing sugars

Answer 11

glucose, fructose and maltose are reducing sugars and that sucrose is a non-reducing sugar

Question 12

how are disaccharides formed

Answer 12

formation of a glycosidic bond by condensation- removal of H2O

Question 13

breakage of glycosidic bond

Answer 13

breakage of a glycosidic bond in polysaccharides and disaccharides by hydrolysis, with reference to the non-reducing sugar test

Question 14

describe the molecular structure of the polysaccharide
starch (amylose and amylopectin) and relate
their structures to their functions in living organisms

Question 15

describe the molecular structure of the polysaccharide glycogen and relate their structures to their functions in living organisms

Question 16

describe the molecular structure of the polysaccharide cellulose and outline how the arrangement of cellulose molecules contributes to the function of plant cell walls

Question 16

what are triglycerides and their molecular structure

Answer 16

triglycerides are non-polar hydrophobic molecules.

3 fatty acids chain (saturated and unsaturated), 1 glycerol
and the formation of ester bonds- removal of H2O.

Question 16

relate the molecular structure of triglycerides to their functions in living organisms

Question 16

describe the molecular structure of phospholipids

Answer 16

hydrophilic (polar) phosphate heads and hydrophobic (non-polar) fatty acid tails.

Question 17

general structure of an amino acid

Answer 17

NH2- amine
COOH- carboxyl
R- r-group 20 types
H-

H2O removed to form peptide bond oh from cooh and h from nh2 to form chon.

Question 17

describe the types of interaction that hold protein molecules in shape:

Answer 17

• hydrophobic interactions
• hydrogen bonding
• ionic bonding
• covalent bonding, including disulfide bonds

Question 18

meaning of the terms primary structure, secondary structure, tertiary structure and quaternary structure of proteins

Question 18

structure of a molecule of haemoglobin

Answer 18

globular protein

formation of its quaternary structure from two alpha (α) chains (α–globin), two beta (β) chains (β–globin) and a haem group.

Question 19

relate the structure of haemoglobin to its function, including the importance of iron in the haem group

Question 19

types of proteins and their features

Answer 19

globular proteins are generally soluble and have physiological roles and fibrous proteins are generally insoluble and have structural roles. globular- haemoglobin, enzymes, fibrous- collagen, keratin, fibrin, elastin

Question 20

describe the structure of a molecule of collagen.

Answer 20

fibrous protein the arrangement of collagen molecules to form collagen fibres.

Question 21

relate the structures of collagen molecules and collagen fibres to their function.