Biological Molecules

Question 1

Structure of phospholipids

Answer 1

inorganic phosphate ions
ion has extra electrons
hydrophilic head
hydrophobic tail

Question 2

Why are unsaturated fatty acids liquid at room temp?

Answer 2

double bonds cause bends so they cannot pack closely together

Question 3

Structural difference between alpha and beta glucose

Answer 3

on the first carbon, the hydroxyl group is at the top when its beta glucose

Question 4

Quartanery structure of proteins

Answer 4

combined polypeptides
prosthetic groups

Question 5

Properties of glucose

Answer 5

polar
soluble in water

Question 6

Properties of fibrous proteins

Answer 6

Long and insoluble
insoluble because theres a high proportion of hydrophobic R groups

Question 7

Properties of conjugated proteins

Answer 7

Globular proteins with a prosthetic

Question 8

Primary structure of proteins

Answer 8

The specific order of amino acids in a polypeptide

Question 9

Structure of collagen

Answer 9

Three polypeptide chains
triple helix
every third amino acid is glycine which makes it compact

Question 10

Properties of globular proteins

Answer 10

Compact, water soluble and spherical.
Hydrophilic R groups on the outside

Question 11

Structure of elastin

Answer 11

Many soluble tropoelastin protein molecules

Question 12

Saturated fatty acid

Answer 12

no double bonds

Question 13

synthesis of dipeptides

Answer 13

amine and carboxyl group join
form a peptide bond
condensation reaction

Question 14

Tertiary structure of proteins

Answer 14

R groups interact:
Hydrogen bonding
Disulphide bridges
Hydrophobic interactions
Hydrophilic interactions
Ionic bonds

Question 15

How does a dissacharide form

Answer 15

condensation reaction
water molecule removed
1-4 glycosidic bond

Question 16

Structure of triglycerides

Answer 16

3 fatty acids
glycerol molecule
joined by ester bonds

Question 17

Structure of starch

Answer 17

amylose: 1-4 glycosidic bonds, helix, stabilised by hydrogen bonds
Amylopectin: 1-4 glycosidic bonds with 1-6 branches

Question 18

Structure of cellulose

Answer 18

beta glucose
1-4 glycosidic bonds
every other glucose is flipped
straight chains form hydrogen bonds

Question 19

Structure of glycogen

Answer 19

1-4 glycosidic bonds
1-6 branches
compact, ideal for storage
branching provides attachments where molecules can be added or removed

Question 20

Secondary structure of proteins

Answer 20

polypeptide bends
hydrogen bonds form
alpha helices and beta pleated sheets

Question 21

Water is polar. What does this mean?

Answer 21

There are areas of electronegative and areas of electropositive charge

Question 22

Importance of water being a good solvent

Answer 22

Metabolic processes in all organisms rely on chemical reactions being able to occur in a solution

Question 23

Importance of water having a high specific heat capacity

Answer 23

Constant temperatures provided (no fluctuations)

Question 24

Why does water have a high specific heat capacity?

Answer 24

The amount of hydrogen bonds present; a lot of thermal energy would be required to break them all

Question 25

Importance of water having a high latent heat of vaporisation

Answer 25

coolant

only a small amount of water is lost for a large amount of heat to be lost

Question 26

Importance of water being cohesive and adhesive

Answer 26

Allows continuous columns of water up xylems

creates surface tension

Question 27

Which elements are present in:
Carbs
Lipids
Proteins
Nucleic Acids

Answer 27

Carbs: C H O
Lipids: C H O
Proteins: C H O N S
Nucleic Acids: C H O N P

Question 28

Compare the structure and functions of amylose and cellulose

Answer 28

Amylose:
Straight chain of alpha glucose
Coils up
Plant storage

Cellulose:
Beta glucose joined by 1-4 glycosidic bonds
Alternate glucoses are inverted
Straight chains with hydrogen bonds between chains
Forms cell walls

Question 29

Explain how the structure of glucose relates to its function

Answer 29

Used in respiration to release ATP
Easily converted into glycogen for storage

Question 30

Explain how the structure of amylose relates to its function

Answer 30

Insoluble in water so does not affect the water potential of the cell - good for storage

Question 31

Explain how the structure of glycogen relates to its function

Answer 31

Highly branched so is easily hydrolysed
Insoluble so does not affect water potential
Compact - high energy content

Question 32

Explain how the structure of cellulose relates to its function

Answer 32

hundreds of polypeptide chains - forming many hydrogen bonds = strong
Macrofibrils:
Allows water to move through cell wall
Prevents cells from bursting
Determines how a cell can grow

Question 33

How is a peptide bond formed?

Answer 33

H group of an amine group and the OH group from a carboxyl group

Water is lost

Question 34

Biuret Test

Answer 34

Proteins

Add biuret solution

lilac = protein present

Question 35

Reducing sugars (Benedict’s test)

Answer 35

Add benedict’s solution
Heat to 80
Reducing sugar present = orange/red precipitate

Question 36

Non reducing sugars (Benedict’s test)

Answer 36

If reducing sugars test is negative

Fresh sample with hydrochloric acid
neutralise with sodium hydrogencarbonate
Add benedict’s solution
Heat to 80
Non reducing sugar present = orange/red precipitate

Question 37

Iodine test

Answer 37

Starch

Add iodine

Starch present = black

Question 38

Emulsion test

Answer 38

Lipids

Mix with ethanol
Shake gently
Pour into water
Lipid present = white emulsion