Macromolecules

Question 1

Roles of sugars and polysaccharides

Answer 1

Food molecules and energy store
Structural support
cell protection
cell-cell adhesion and motility
cell signalling

Question 2

What are D isomers

Answer 2

straight chain polyhydroxy alcohols (linear form of cyclic sugars)
either an aldehyde or ketone group
at least three carbon units

Question 3

What are the two glucose enantiomers

Answer 3

alpha and beta glucose

Question 4

How do the two glucose enantiomers differ, which one is more stable

Answer 4

alpha glucose = OH group pointing down
beta glucose = OH group pointing up

beta is more stable as OH groups are further apart in the molecule

Question 5

What are the polymers of the glucose enantiomers

Answer 5

alpha = starch and glycogen
beta = cellulose and chitin

Question 6

How are sugars linked

Answer 6

condensation reaction, removing water forming a 1,4 glycosidic bond

Question 7

What is the reducing end

Answer 7

the end that is free to become linearised

Question 8

Glycogen

Answer 8

highly branched glucose polysaccharide
branching increases the number of ends available to be digested for rapid release of glucose

Question 9

Structure of a ribosome

Answer 9

RNA and protein
active site of ribosome is RNA which is the catalyst for protein synthesis
ribozyme - extra OH on ribose

Question 10

Structure of a ribosome

Answer 10

RNA and protein
active site of ribosome is RNA which is the catalyst for protein synthesis
ribozyme - extra OH on ribose

Question 11

What is DNA and RNA used for

Answer 11

DNA = store of genes
RNA = gene expression

Question 12

What bonds form when nucleotides are polymerised

Answer 12

phosphodiester

Question 13

What type of pentose is deoxyribose and where is it deoxy at

Answer 13

Aldopentose
deoxy at the 2 position

Question 14

How many hydrogen bonds between A and T, C and G

Answer 14

A and T = 2
C and G = 3

Question 15

What are purine and pyrimidine bases

Answer 15

Purine = A and G, two rings
Pyrimidine = T, U, C, one ring

Question 16

Why does a purine and pyrimidine always complementary base pair

Answer 16

keeps the sugar phosphate backbone the same distance apart all the way along the DNA strand

Question 17

what is a nucleoside

Answer 17

ribose and base

Question 17

what is a nucleoside

Answer 17

ribose and base

Question 18

Which complementary base pair requires less energy to break

Answer 18

A and T as there is only two hydrogen bonds between them

Question 18

Which complementary base pair requires less energy to break

Answer 18

A and T as there is only two hydrogen bonds between them

Question 18

Which complementary base pair requires less energy to break

Answer 18

A and T as there is only two hydrogen bonds between them

Question 18

Which complementary base pair requires less energy to break

Answer 18

A and T as there is only two hydrogen bonds between them

Question 19

Levels of protein structure

Answer 19

Primary = the order of amino acid residues in the chain
Secondary = localised regular arrangements of the polypeptide backbone to form alpha helices and beta sheets
Tertiary = overall three dimensional fold of the protein
Quaternary = arrangement of multiple amino acid chains

Question 20

Amino acids

Answer 20

Chiral carbon molecules
Carboxyl group
Amino group
Hydrogen
R group

Only amino acid that is not chiral = glycine

Question 21

How do amino acids differ

Answer 21

Chemical groups within side chains

Question 22

Hydrophobic

Answer 22

Water hating Large and non polar R groups Cluster away from water in the core of the protein or at interaction interfaces

Question 23

What are the hydrophobic Amino acids

Answer 23

Alanine Valine Leucine Isoleucine Glycine Cysteine Phenylalanine Tryptophan Proline

Question 24

Which two hydrophobic amino acids contain sulphur

Answer 24

Cysteine Methionine

Question 25

What amino acid can form disulphide bonds and how

Answer 25

Cysteine In an oxidising environment so not in cells as this is reducing

Question 26

Hydrophilic

Answer 26

Water loving Forms hydrogen bonds with water Can be uncharged but polar, negatively charged, positively charged

Question 27

What are the negatively charged amino acids

Answer 27

Aspartic acid Glutamic acid (Both carboxylic acids)

Question 28

What are the positively charged amino acids

Answer 28

Lysine (primary amine) Arginine Histidine

Question 29

What are the uncharged polar amino acids

Answer 29

Serine Threonine Tyrosine (Hydroxyl groups) Asparagine Glutamine

Question 30

Peptide bond

Answer 30

Condensation reaction removing water as the amino and carboxyl groups are joined together forming a linear peptide

Question 31

How are proteins numbered

Answer 31

From the N terminus to the C terminus Residue 1 has a free NH3 +

Question 32

What are the side chains of the polypeptide

Answer 32

The R groups

Question 33

What structure is a peptide bond

Answer 33

Planar - no rotation (All in one plane)

Question 34

Why can the peptide bond flick between single and double bonded

Answer 34

Delocalisation of electrons from the nitrogen onto the single C-N gives it a partial double bond characteristics Restricts rotational movement of the polypeptide chain around that bond

Question 35

How is the confirmation of the backbone describe by

Answer 35

Torsion angles

Question 36

What are the angles of rotation

Answer 36

Phi = angle around alpha carbon and nitrogen Psi = angle around alpha carbon and carbon

Question 37

How does folding of the polypeptide chain occur

Answer 37

Rotation of the phi and psi angles for each residue Rotation around alpha carbon is not completely free as many combinations of phi and psi angles cause steric clashes of side chains

Question 38

Disaccharides

Answer 38

Maltose = alpha glucose and alpha glucose Sucrose = alpha glucose and alpha fructose Lactose = alpha glucose and beta galactose Lactulose = beta galactose and beta fructose

Question 39

Consequences of breaching in starch and glycogen

Answer 39

Starch is more densely packed More exposed end units for access by glycogen synthase/phosphorylase

Question 40

How can C be converted to U

Answer 40

Spontaneous deamination

Question 41

Why is DNA double stranded

Answer 41

Provide copying mechanism Enable repair of damaged bases Stabilise with hydrogen bonds

Question 42

Why is RNA single stranded

Answer 42

Allow protein synthesis Allow internal hydrogen bonding Allow binding to proteins as well as other RNAs

Question 43

Ramachandran plot shows

Answer 43

Most optimal phi and psi angles to avoid steric clashes