Proteins, Polysaccharides And Lipids

Question 1

A-helix examples

Answer 1

Haemoglobin, Myosin

Question 2

A helix bonding

Answer 2

CO hydrogen bonded to NH 4 residues ahead.

3.6 residues / helix turn

Question 3

A helix structure

Answer 3

Rod. Strong extensible proteins. Stabilised by H bonds

Question 4

Beta Pleated Sheet example

Answer 4

Proteins where flexibility eg silk fibroin (anti-parallel)

Question 5

Beta pleated sheet structure

Answer 5

Zigzag chains. Parallel, Anti-parallel

Question 6

Beta pleated sheets bonding

Answer 6

Chains align, CO and NH align, H bonding occurs = sheet structure

Question 7

Triple Helix example

Answer 7

Collagen only. Connective tissue (skin, bone, tendon)

Question 8

Triple helix structure

Answer 8

Strong soluble fibres. Three chains = tropocollagen

Question 9

Triple helix amino acid number

Answer 9

1000 per chain. No H bonds in chain

Question 10

Triple Helix chemical structure

Answer 10

X-Pro-Gly or X-Hyp-Gly. H bonds between Hyp and Hydroxylysine residues

Question 11

Triple Helix 2

Answer 11

Small Gly residues. Bulky R groups point outwards. Intra/inter covalent bonds between Lys and His

Question 12

Fibrous proteins

Answer 12

Insoluble, metabolically unreactive.
Collagen
Keratin
Fibrin (blood clots)
Elastin (eg arterial walls)
Myosin (muscle)

Question 13

Physical structure of collagen triple helix

Answer 13

Glycine, hydroxyproline, proline

Question 14

Globular proteins

Answer 14

Spherical. Backbone folds on itself. Soluble

Question 15

Globular proteins structure

Answer 15

Usually have 3• and 4• structures eg myoglobin and actin (3•) and haemoglobin (4•)

Question 16

Sterols examples

Answer 16

Cortisol, Cholesterol, Estrogen (estradiol) , testosterone

Question 17

Stearic acid (saturated fat and fatty acid)

Answer 17

the molecules are tightly packed

Question 18

Unsaturated fat and fatty acids (oleic acid)

Answer 18

The molecules cannot pack together closely due to kinks

Question 19

Myoglobin

Answer 19

Oxygen storage in muscle. Globular, 3* structures. 8 helical regions (75 percent of all aa), single chain (153 aa), random coiling

Question 20

Absence of haem group in myoglobin

Answer 20

Forms apoprotein
not tightly folded

Question 21

Myoglobin interior

Answer 21

only two polar His residues Important for haem

Question 22

Prosthetic haem group

Answer 22

hydrophobic bonds between haem porphyrin ring and non polar side chains

Question 23

Haemoglobin

Answer 23

Oxygen transport. 4* structures. 2 pairs of polypeptide chains (2a and 2b) Similar to myoglobin. Spheroidal. 4 haem groups

Question 24

Interactions Haemoglobin

Answer 24

Each a subunit in contact with both b chains. Few interactions between two a or two b chains.

Question 25

Irregular shape

Answer 25

a1b1 and a2b2 half molecules irregular in shape as central open channel when fitted together

Question 26

Mode of action of messenger proteins

Answer 26

Influence rate of synthesis of enzymes and other proteins

Affect rate of enzymatic catalysis

Alter permeability of cell membranes

Question 27

Hormone

Answer 27

Bonds membrane bound receptor, message related to inside cell, cascade of events, cellular action

Question 28

Hormones can be

Answer 28

Proteins polypeptide amino acid derivatives or steroids

Question 29

Enzymes

Answer 29

Globular proteins that increase reaction rates by up to 10^20

Question 30

Muscle contraction

Answer 30

Myosin (fibrous)

Actin (gobular)

Question 31

Immune protection

Answer 31

Antibodies, cytokines

Question 32

Monosaccharides

Answer 32

The building blocks of more complex carbohydrates

Question 33

Aldoses vs ketoses

Answer 33

Aldoses contain aldehyde group and ketoses contain ketone group

Question 34

Starch vs cellulose

Answer 34

Starch has 1-4 linkages of a glucose whilst cellulose has 1-4 linkages of b glucose

Question 35

Disacchardides

Answer 35

Dehydration/hydrolysis reactions of monosaccharide units form /catabolise complex carbohydrates

Question 36

Glucose plus glucose

Answer 36

Maltose

Question 37

Sucrose plus maltose

Answer 37

Lactose

Question 38

Difference between alpha and beta configuration

Answer 38

OH in alpha below 1 and above 1 in beta

Question 39

Starch vs cellulose up or down

Answer 39

Starch down but cellulose up

Question 40

Amylose

Answer 40

Unbranched (5-600 glucose units) a-1,4-linked

Question 41

Amylopectin

Answer 41

Branched glucose units. 30 a-1,4-linked units until branch point (a-1,6 link)
Food reserve

Question 42

Glycogen

Answer 42

Same structure as starch but more highly branched
Food reserve

Question 43

Cellulose

Answer 43

Unbranched b-1,4-linked glucose units
Cannot be digested by animal enzymes (some ruminants possess b-glycosidases which digest cellulose)
Structural role

Question 44

Complex carbohydrates

Answer 44

Plant cells, cellulose microfibrils in plant cell wall (0.5 micro metres), microfibril, about 80 cellulose molecules form a microfibril the main architectural unit of a plant cell wall. Cellulose molecules, a cellulose molecule is an Unbranched b glucose polymer. Parallel cellulose molecules held by hydrogen bonds between hydroxyl groups attached to carbons 3 and 6

Question 45

Glycerides (based on glycerol)

Answer 45

For example phosphatidylcholine (a diacylglyceride) is a major phospholipid of membranes. Triacylglycerides are storage compounds