Biological Molecules

Question 1

Glucose + glucose

Answer 1

Maltose + H2O

Question 2

Glucose + galactose

Answer 2

Lactose + H2O

Question 3

Glucose + fructose

Answer 3

Sucrose + H2O

Question 4

Properties of starch

Answer 4

Large - cannot cross cell surface membrane
Insoluble - osmotically inactive
Helical - forms a compact store
Branched - glucose is easily released

Question 5

Properties of glycogen

Answer 5

Insoluble - osmotically inactive
Branched - for easy release of glucose

Question 6

Test for reducing sugars

Answer 6

Benedict’s test

Question 7

Benedict’s test method

Answer 7

Add sample to same volume of Benedict’s solution
Heat to 95° in a water bath

Question 8

Test for starch

Answer 8

Iodine test

Question 9

Positive result of starch test

Answer 9

Colour change
Orange —> blue/ black

Question 10

Positive result of Benedict’s test

Answer 10

Colour change
Blue —> brick red

Question 11

Test for protein

Answer 11

Biurets test

Question 12

Positive result for biurets test

Answer 12

Colour change
Blue —> lilac

Question 13

Test for lipids

Answer 13

Emulsion test

Question 14

Emulsion test method

Answer 14

Place sample in test tube with ethanol
Shake mixture so fat dissolves
Add water and mix

Question 15

Positive result for emulsion test

Answer 15

White emulsion forms

Question 16

Method for testing non reducing sugar

Answer 16

Carry out Benedict’s test on sample - negative result

Heat sample in water bath to 95° with HCl
Let cool
Neutralise with alkali
Add Benedict’s solution and heat in water bath to 95°
Positive result shows none reducing sugar present

Question 17

Alpha glucose

Answer 17

Question 18

Condensation reaction with peptides

Answer 18

Question 19

What bond joins amino acids

Answer 19

Peptide bonds as a result of a condensation reaction

Question 20

What bonds join phospholipids

Answer 20

Esther bonds as a result of a condensation reaction

Question 21

What bonds join monosaccharides

Answer 21

Glycosidic bonds as a result of condensation reactions

Question 22

Primary structure of proteins

Answer 22

Sequence of amino acids in a polypeptide chain

Question 23

Secondary structure of proteins

Answer 23

Coiling/ folding of the polypeptide chain due to hydrogen bonding

Form either alpha helix or beta pleated sheets

Question 24

Tertiary structure of a protein

Answer 24

Further coiling / folding of polypeptide chain due
Ionic bonds form
Disulphide bridges form

Question 25

Quaternary structure of proteins

Answer 25

Proteins with more than one polypeptide chain due Ionic

Question 26

Properties of water (4)

Answer 26

Metabolic reactions - metabolite Solvent -transport nutrients -remove waste products Temperature regulation -high heat capacity Absorbs lots of heat energy before temperature increases -large latent heat of vaporisation Cooling effect Support - internal cohesive forces between molecules Supports water tubes eg. Xylem -external cohesive forces provide surface tension -not easily compressed

Question 27

Induced fit enzyme

Answer 27

Active site of enzyme is flexible Presence of specific substrate induces a change in active site shape Active site becomes complementary Enzyme remains unchanged at end of reaction

Question 28

Effect of pH on enzymes

Answer 28

Small optimum pH window Too high or too low pH can denature enzymes Active site changes shape due to change in tertiary structure

Question 29

Effect of temperature on enzymes

Answer 29

Higher temp more kinetic energy Increases frequency of collisions between active site and substrate (more enzyme-substrate complexes) Too high temp can denature enzymes by changing active site shape by altering tertiary structure

Question 30

Competitive inhibition

Answer 30

Inhibitor has a similar structure to substrate and competes to attach to active site Substrate cannot bind RoR decreases Addition of more substrate can increase RoR

Question 31

Non-competitive inhibition

Answer 31

Inhibitor doesn’t have similar structure to substrate Combines elsewhere on the enzyme - not the active site Enzyme inhibitor complex forms Alters tertiary structure of enzyme Substrate cannot bind as it’s no longer complementary

Question 32

ATP

Answer 32

ATP is hydrolysed to release energy and then resynthesized ATP (+atp hydrolyse) —> ADP +Pi

Question 33

ATP

Answer 33

ATP is hydrolysed to release energy and then resynthesized ATP (+atp hydrolyse) —> ADP +Pi