protein structure and amino acids

Question 1

what are proteins?

Answer 1

a diverse group of molecules

can exist in many different shapes and sizes

can exhibit a range of chemical and physical properties

Question 2

what are the 2 general classes of proteins?

Answer 2

fibrous and globular proteins

Question 3

describe fibrous proteins?

Answer 3

• important structural proteins
  -long thread like tough and insoluble in water

Question 4

what does fibrous proteins make?

Answer 4

bone, skin, tendons, cartilage, hair, wool, fur, nails, claws, scales, feathers, muscle, silk

Question 5

what does fibrous proteins include>

Answer 5

collagens, keratin, fibrin, elastins

Question 6

describe collagen?

Answer 6

25-35% total protein in mammals

major component of connective tissues (bones, teeth, cartilage, tendons, ligaments, blood vessels, skin)

Question 7

describe collagen in bone?

Answer 7

found along with calcium phosphate polymer

Question 8

describe collagen in tendons?

Answer 8

collagen forms stiff fibres with high tensile strength

Question 9

describe collagen in skin?

Answer 9

collagen is loosely woven allowing expansion in different directions

Question 10

describe keratin?

Answer 10

major component of skin, fur, hair

composed almost entirely of helix structures (slightly more tightly wound than -helix)

Question 11

what is the basic unit of keratin?

Answer 11

protofibril

Question 12

describe globular proteins?

Answer 12

have important ‘biological’ or ‘operational’ functions

roughly) spherical in shape

more soluble than fibrous proteins

glob proteins include enzymes, hameoglobin etc

Question 13

what is a conjugated protein?

Answer 13

contain a protein component associated with a non-protein component

Question 14

all protein are made from what?

Answer 14

20 amino acids

Question 15

the amino acid side chains vary in?

Answer 15

size
charge
shape
chemical reactivity

Question 16

what is the basic amino acid structure

Answer 16

draw

Question 17

what are the classes of amino acids?

Answer 17

aliphatic
imino
hydroxy
sulphur-containing
aromatic
heterocyclic
basic
acidic (+ amide derivatives)

Question 18

describe aliphatic amino acids?

Answer 18

c atoms in the side chain are arranged in chains. because these amino acids contain C and H they prefer to make non polar covalent bonds

-partially soluble in h20

the longer the side chain the more hydrophobic the amino acid

Question 19

describe hydroxy amino acids?

Answer 19

side chains have a OH group
these side chains contain O as well as carbon and hydrogen (electronegatives) they prefer to make polar bonds

readily soluble in h20

Question 20

sulphur containing AA

Answer 20

have aliphatic side chains
have thiol (SH) or thioether (S-CH3) groups
are hydrophobic amino acids

Question 21

what are aromatic amino acids/

Answer 21

side chains contain benzene skeleton
are hydrophobic amino acids

Question 22

heterocyclic amino acids?

Answer 22

eg. histidine
the ring structure is not composed of just one sort of atom

histidine is hydrophilic

Question 23

what are basic amino acids?

Answer 23

+ charged at neutral pH

Question 24

what are acidic amino acids?

Answer 24

• charged at a neutral pH

-secondary carboxylic acidic (COO-) group

-hydrophilic

-amide derivatives have an amide group instead (CONH2)

Question 25

what is an imino acid?

Answer 25

has an aliphatic side chain, cyclised by bonding to the N atom of the amino group

hydrophobic

Question 26

what is important about the amino side chain?

Answer 26

plays a large part in controlling its chemical and physical properties

Question 27

an amino acid solubility depends on

Answer 27

the structure of the side chain

Question 28

where would you find regions of proteins containing hydrophobic AA

Answer 28

may exist in hydrophobic intracellular environments (eg. within membranes)

Question 29

what can bacteria do?

Answer 29

bacteria can synthesise all amino acids

Question 30

humans can do what?

Answer 30

humans can only synthesise 10 from other precursor molecules

the remainder must be obtained in the diet (essential amino acids)

Question 31

lysine and tryptophan

Answer 31

vegeatrains must have proptions of these in the diet