2.1.2 Biological Molecules

Question 1

Biological molecules

Answer 1

CHO Carbohydrates
CHO Lipids
CHON Proteins
CHONP Nucleic acids

Question 2

Water

Answer 2

Polar
= cohesive for transport = good transport solvent

H-bonds (H-O)
= high SHC = gradual temp changes = high LH of evaporation (sweat)

Less dense when solid
= fish swim = molecules held further apart (H-bonds fix)

Question 3

Carbohydrates

Answer 3

Alpha glucose = OH group below

Beta glucose = OH group above

Glucose
= energy store, soluble, easily transported
= glycosidic bonds

Condensation
= water given off, bonds formed

Hydrolysis
= water needed, bonds broken

Question 4

Carbohydrates; GLYCOGEN

Answer 4

Energy store in animals

Alpha glucose

More branches than amylopectin
Easy access for enzymes

Compact for storage

Question 5

Carbohydrates; STARCH

Answer 5

Energy store in plants

Alpha glucose

AMYLOSE long unbranched coiled

AMYLOPECTIN long branched enzyme access

Question 6

Carbohydrates; CELLULOSE

Answer 6

Cell walls

Beta glucose

Long unbranched
Chains linked by H-bonds
Fibres = microfibrils

Alternately flipped OH H

Question 7

Testing for carbohydrates; reducing sugars

Answer 7

Add equal volume of Benedict’s reagent
Heat gently in boiling water bath 5 mins

Brick red precipitate = positive result

Qualitative

Question 8

Testing for carbohydrates; non-reducing sugars

Answer 8

e.g. sucrose won’t react w Benedict’s when warmed

Boil with dilute hydrochloric acid
Add Benedict’s
Warm 5 mins
(Sucrose hydrolysed to glucose and fructose = reducing sugars)

Question 9

Colours of Benedict’s test

Answer 9

Blue = none 
Green = very low
Yellow = low
Orange = medium
Brick red = high

Question 10

Testing for carbohydrates; Iodine test for starch

Answer 10

Few drops of iodine

Changes to purple/black = starch present

Question 11

Lipids

Answer 11

Fats&oils • non-polar • insoluble • large macromolecules

TRIGLYCERIDES 1 glycerol + 3 fatty acids • esterification = ester bonds • energy store

PHOSPHOLIPIDS phosphate + 2 fatty acids • form surfactants and bilayers (membranes)

CHOLESTEROL hydrocarbon ring with HC tail • strengthen cell membrane • bind to hydrophobic tails

Question 12

Proteins

Answer 12

Amine group, carboxyl group, r-group (amino acid)

Synthesis=OH and H released as H2O

PEPTIDE bonds formed

Catalysed by PEPTIDYL TRANSFERASE

Question 13

Primary structure of protein

Answer 13

Sequence of AA

PEPTIDE bonds between AA

Question 14

Secondary structure of protein

Answer 14

HON atoms interact
H-bonds form within AA chain

Alpha helix

Beta pleated sheet

Question 15

Tertiary structure of protein

Answer 15

Cooking and folding brings R-groups closer together - interact

• Hydrophobic/philic interactions LOW
• H-bonds LOW
• Ionic bonds MED
• Disulphide bonds HIGH

Question 16

Types of proteins

Answer 16

Globular = compact, soluble, sphere, hydrophobic R-groups in centre e.g.INSULIN

Conjugated = globular + prosthetic group e.g. haemoglobin

Fibrous = long, insoluble, repetitive AA sequence e.g. keratin (hair,disulphide)

Question 17

What are the bonds in carbohydrates?

Answer 17

Glycosidic

Question 18

What are the bonds in lipids?

Answer 18

Ester

Question 19

What are the bonds in proteins?

Answer 19

Peptide

Question 20

What are the bonds in nucleic acid?

Answer 20

Phosphodiester (between nucleotides)