Biochemistry

Question 1

4 types of large biological molecules in body

Answer 1

1. Protein
2. Carbohydrates
3. Lipid
4. Nucleic Acid

Question 2

Which one of the four large biological molecules is distinctively different from the others? How?

Answer 2

Lipid, all others are polymers

Question 3

Reaction of monomers joining to form polymer

Answer 3

Condensation / dehydration

2 mononers join, lose 1 water molecule

Question 4

Reaction of polymer dissembling into monomers

Answer 4

Hydrolysis

adding of water, H on one end, OH on another end

Question 5

2 Classes of carbohydrates based on location of carbonyl group (C=O) group

Answer 5

1. Aldoses - carbonyl at end of chain

2. Ketoses - carbonyl in middle of chain

Question 6

Name of bond between monosaccharides

Answer 6

Glycosidic linkage

Question 7

Major difference between storage polysaccharides in plant and animal? What is the purpose of that?
(plant: starch, animal: glycogen)

Answer 7

Greater level of branching in glycogen –> need multiple enzymes to be broken down –> slow down rate of breaking

Question 8

Monomers of carbohydrates

Answer 8

monosaccharide

Question 9

Monomers of protein

Answer 9

amino acid

Question 10

pKa of carboxyl group

How would it be changed?

Answer 10

pKa: 4
<4: more COOH
>4: more COO-

Question 11

pKa of amino group

How would it be changed?

Answer 11

pKa: 9
<9: more NH3+
>9: more NH2

Question 12

Name of the state when 2 ions are present in the amino acid? (NH3+ & COO-) When would it occur?

Answer 12

Zwitter ion

4 < pH < 9

Question 13

Name of bond joining amino acids together

Answer 13

Peptide bond

Question 14

Word describing amino acids with 4 different substituents

Answer 14

chiral

Question 15

Name for isomers that are different in spatial arrangement (mirror images)

Answer 15

enantiomers

Question 16

2 models for protein

Answer 16

1. Ribbon Model

2. Space-filling model

Question 17

How many different amino acids are there?

Answer 17

20

Question 18

From which end is an amino acid sequence numbered from?

Answer 18

amino end (with NH2/NH3+)

Question 19

3 types of secondary structure in protein

Answer 19

a helix
B sheet
random coil

Question 20

What is secondary structure stabilized by?

Answer 20

hydrogen bonds
(a helix: between nearby residues)
(B sheet: between carbonyl group from one amino acid and amino group from another)

Question 21

What is tertiary structure of protein resulted from?

Answer 21

Non-covalent interactions between amino acids and side chains

Question 22

How many polypeptides are there in myoglobin and haemoglobin respectively?

Answer 22

myoglobin: 1
haemoglobin: 4

Question 23

What do homologous proteins share? Give an example of homologous proteins.

Answer 23

Similar primary, secondary & tertiary structure

e.g. myoglobin & haemoglobin

Question 24

How many polypeptides are in haemoglobin? How are they different?

Answer 24

4.

2 alpha chains, 2 Beta chains

Question 25

Where is the mutation in sickle cell disease? What is the mutation?

Answer 25

in Beta chain glutamate --> valine negatively charged --> non-polar

Question 26

What happens in sickle-cell haemoglobin?

Answer 26

Aggregation: mutated deoxyhaemoglobin gets attracted and locked into one another --> form long & insoluble fibres --> greatly reduce capacity to carry oxygen

Question 27

How is insulin activated?

Answer 27

Proteolytic (enzyme) cleavage breaks proinsulin into active insulin with 2 polypeptide chains held together by strong disulfide bonds

Question 28

What is globular protein? And what are its characteristics?

Answer 28

Soluble proteins: 1. hydrophobic amino acids located inside core of protein 2. hydrophillic amino acids on surface of protein

Question 29

Is collagen soluble in water?

Answer 29

No, it is fibrous and insoluble in water.

Question 30

Major function of collagen?

Answer 30

Provide mechanical strength to connective tissue

Question 31

What are the inactive and active forms of collagen called?

Answer 31

inactive: procollagen active: tropocollagen

Question 32

How is collagen activated?

Answer 32

By procollagen peptidase. It breaks the peptide bond linking the loose ends at the amino group terminal and carboxyl group terminal.

Question 33

How many polypeptides are there in collagen? Give an important characteristic of them.

Answer 33

3, they intertwine with each other.

Question 34

What is the structure of collagen called?

Answer 34

triple-helix

Question 35

What is the significance of vitamin C in collagen?

Answer 35

Vitamin C activates prolyl-4-hydroxylase (enzyme) prolyl-4-hydroxylase catalyzes formation of hydroxypoline from proline ring -> form more hydrogen bonds -> strengthening collagen

Question 36

What is a disulfide bond? Between which amino acid would it be formed?

Answer 36

strong covalent bond between 2 sulfides. | Formed between cysteine.

Question 37

What happens to collagen in osteogenesis imperfecta?

Answer 37

glycine (smallest amino acid) at core of the triple-helix is replaced by cysteine --> disrupt helical arrangement and hydrogen bonds --> weakened triple-helix

Question 38

6 steps in collagen biosynthesis:

Answer 38

1. Single strands of polypeptides are formed 2. Hydroxylation (adding of hydroxy group) of proline and lysine side chains 3. Triple-helix is formed 4. Procollagen is converted to tropocollagen by procollagen peptidase 5. Bundles form (associating layers) 6. Cross links form (enzyme attach individual collagen molecules together)

Question 39

3 types of biologically important lipids

Answer 39

1. Fats 2. Phospholipids 3. Steroids

Question 40

What are fats constructed from?

Answer 40

Glycerol and fatty acids

Question 41

How are the fatty acids attached to the glycerol?

Answer 41

Dehydration --> Ester Linkage

Question 42

Another name for fat

Answer 42

triglyceride

Question 43

Functions of fat

Answer 43

1. Energy storage 2. Protect vital organs 3. Insulate body

Question 44

Composition of phospholipid

Answer 44

2 fatty acids and 1 phosphate group attached to a glycerol

Question 45

Where does protein synthesis occur?

Answer 45

In ribosomes

Question 46

What controls protein synthesis?

Answer 46

mRNA

Question 47

Monomer of nucleic acid

Answer 47

nucleotides

Question 48

Polymer of nucleic acid

Answer 48

polynucleotides

Question 49

2 Major types of nitrogenous bases

Answer 49

1. Pyrimidines: 6-membered ring (C, T, U for RNA) | 2. Purines: 6-membered ring fused to a 5-membered ring (G, A)

Question 50

What is the backbone of polynucleotides called? And the appendages?

Answer 50

Sugar-phosphate backbone | Appendages: nitrogenous bases

Question 51

How many polynucleotides are there in DNA?

Answer 51

2 polynucleotides

Question 52

How are the 2 polynucleotides arranged?

Answer 52

in double helix, with backbones running antiparallel to each other

Question 53

Name for spontaneous reaction with net release of energ

Answer 53

Exergonic reaction

Question 54

Name for non-spontaneous reaction with net absorb of energy

Answer 54

Endergonic reaction

Question 55

3 Steps in cellular respiration

Answer 55

1. Glycolysis 2. Citric acid cycle 3. Oxidative phosphorylation