Ch 3 Biological Molecules

Question 1

Structure of water

Answer 1

• oxygen covalently bonded to 2 hydrogen atoms
• 104.5° bond angle
• 2 lone pairs
• 𝛿- on oxygen
  -𝛿+ on hydrogens

Question 2

Reasons for high boiling point of water

Answer 2

• hydrogen bonding
• stronger than London forces or dipole - dipole interactions
• reason water is liquid at room temperature

Question 3

Hydrogen bonding

Answer 3

Conditions
- hydrogen covalently bonded to Nitrogen, oxygen or fluorine
- lone pairs of electrons available
Strongest intermolecular force

Question 4

Why is water denser than ice?

Answer 4

When the water freezes, the hydrogen bonding keeps the molecules locked in a lattice, slightly more spaced out than in liquid form.

Question 5

Cohesion

Answer 5

Sticking to itself

Question 6

Adhesion

Answer 6

Sticking to other things

Question 7

Uses of water being cohesive and adhesive

Answer 7

Surface tension - c
Capillary action - a/c
- transpiration

Question 8

What is a carbohydrate?

Answer 8

A biological molecule made of only Carbon, Hydrogen and Oxygen

Question 9

Monosaccharide, disaccharide, polysaccharide

Answer 9

Saccharide - sugar
One unit, two units, many units

Question 10

Difference in structure of alpha and beta glucose

Answer 10

Alpha - H-H-OH-H-CH2OH
(Top side)
Beta - OH-H-OH-H-CH2OH

Difference - hydroxy group on C1

Question 11

Reaction for adding monomers

Answer 11

Condensation

Question 12

Reaction for splitting monomers

Answer 12

Hydrolysis

Question 13

What monosaccharides make up maltose

Answer 13

Glucose + glucose

Question 14

What monosaccharides make up lactose

Answer 14

Glucose and galactose

Question 15

What monosaccharides make up sucrose

Answer 15

Glucose and fructose

Question 16

Hexose monosaccharides

Answer 16

6 carbon atoms
Glucose, fructose, galactose

Question 17

Pentose monosaccharides

Answer 17

5 carbon atoms
Ribose, deoxyribose

Question 18

What is starch

Answer 18

Collective name for amylose and amylopectin
Storage molecule of glucose for plants

Question 19

Structure of amylose and amylopectin

Answer 19

Polysaccharides
1-4 glycosidic bonds between alpha glucose molecules
Amylopectin has 1-6 bonds, causing branching
Helxical structure

Question 20

What is glycogen

Answer 20

Glucose storage for animals

Question 21

What is the structure of glycogen

Answer 21

1-4 glycosidic bonds between alpha glucose
Very frequent branching (more so than amylopectin)

Question 22

Why is the branching good for glycogen?

Answer 22

More branching means less space used up
More branches mean more sites for glucose to be added or removed

Question 23

Cellulose structure

Answer 23

1-4 glycosidic bonds between alternating orientation beta glucose (every other unit is upside down)
No branching
Straight chain with hydrogen bonds between chains

Question 24

What does Benedict’s reagent test for?

Answer 24

Reducing sugars

Question 25

How do you test for reducing sugars?

Answer 25

Warm the sample in a boiling tube with Benedict’s reagent

Question 26

How do you test for non reducing sugars?

Answer 26

Boil sample with hydrochloric acid and test for reducing sugars

Question 27

What is a positive result for Benedict’s test

Answer 27

Blue - negative Green - very low positive Yellow - low positive Orange - medium positive Red - high positive

Question 28

What is the test for starch?

Answer 28

Iodine Positive result - blue/black Negative result - purple

Question 29

Are lipids soluble in water?

Answer 29

Non polar so insoluble

Question 30

What is a triglyceride?

Answer 30

Glycerol (propan-1,2,3-triol) bonded to 3 fatty acids - ester link

Question 31

Saturated fatty acid

Answer 31

Fatty acid with only single bonds between carbons

Question 32

Monounsaturated fatty acids

Answer 32

Fatty acids with one double bond between carbons

Question 33

Polyunsaturated fatty acids

Answer 33

Fatty acids with many double bonds between carbons

Question 34

What difference do unsaturated fatty acids make to a triglyceride?

Answer 34

The double bonds change the bond angle, meaning lipids don’t pack as easily. This reduces the melting point, making them liquids (oils) at RTP

Question 35

What are phospholipids?

Answer 35

Triglycerides with a phosphate (PO4^3-) head and 2 lipid tails

Question 36

How soluble are phospholipids?

Answer 36

The charged, hydrophilic phosphate heads are soluble in water, while the non-polar, hydrophobic tails aren’t soluble in water.

Question 37

How do you test for lipids

Answer 37

Mix with ethanol and water and shake A white layer will form if lipids are present

Question 38

What do all amino acids have?

Answer 38

R group Amine group - (-NH2) Carboxylic acid - (-COOH)

Question 39

What is a polypeptide?

Answer 39

Multiple amino acids joined by peptide bonds

Question 40

What are peptide bonds?

Answer 40

Bonds between amine groups and carboxylic acids

Question 41

Primary structure of polypeptides

Answer 41

Sequence of amino acids Influences how the chain folds

Question 42

Secondary structure of polypeptides

Answer 42

Hydrogen bonding within a chain or between chains influencing the shape Alpha helix shape - within a chain Beta pleated sheet - between chains

Question 43

Tertiary structure of polypeptides

Answer 43

The final shape of polypeptides, with further interactions occurring between R groups -London forces -hydrogen bonding -ionic bonds -disulphide bridges

Question 44

Quaternary structure of polypeptides

Answer 44

Similar to tertiary structure, but between separate polypeptides

Question 45

Globular protein

Answer 45

Roughly spherical, compact, hydrophilic R groups on outside so soluble

Question 46

Why do hormones need to be soluble

Answer 46

Hormones are transported in the blood so must be soluble in blood plasma

Question 47

What type of protein is insulin

Answer 47

Globular

Question 48

What is a conjugated protein

Answer 48

Proteins with a prosthetic group (e.g. haem group, lipids, carbohydrates)

Question 49

What type of protein is haemoglobin

Answer 49

Conjugated - (4 haem groups)

Question 50

What type of protein is catalase?

Answer 50

Conjugated - (haem group)

Question 51

What is a fibrous protein

Answer 51

Long, insoluble polypeptides, usually with a repeating sequence of amino acids with small R groups

Question 52

What type of protein is keratin?

Answer 52

Fibrous protein

Question 53

What type of protein is elastin?

Answer 53

Fibrous protein

Question 54

What type of protein is