proteins

Question 1

describe the formation of a peptide bond

Answer 1

condensation reaction

between amine group on one AA

and carboxylic acid group of another AA

forming a water molecule

Question 2

describe how hydrogen bonds form within secondary structure of proteins

Answer 2

oxygen is relatively negative and hydrogen is relatively positive

oxygen and hydrogen are attracted to each other

Question 3

alpha keratin is composed of alpha helices

explain why alpha keratin has a more regular structure than the quaternary protein haemoglobin

Answer 3

secondary structures are simple repeating structures

globular protein haemoglobin has a tertiary structure formed from complex folding of a secondary structure

Question 4

compare and contrast the role of R-Group interactions in the formation of tertiary and quaternary structures of proteins

Answer 4

R-groups on AA interact

tertiary – interact within the protein molecule determines its shape

quaternary – interact between protein molecules holds molecules together

both involve the same interactions

Question 5

what’s a peptide bond

Answer 5

formed between amino acids

covalent

carboxylic group of one AA interacts with amine group of another AA in a condensation reaction

Question 6

what’s a protein

Answer 6

polypeptides (and macromolecules) made up of amino acids (monomers)

sequence, type and number of amino acids determines the protein’s shape (and its function)

Question 7

what determines a different amino acid?

Answer 7

the R-group

Question 8

how many different AA are commonly found in cells?

how many of these are essential?

Answer 8

20

9 and can only be obtained from what we eat

Question 9

how is protein synthesised?

Answer 9

peptide bond between amino acids

condensation reaction:
amine group interacts with carboxylic group of another AA

forming a dipeptide/polypeptide

Question 10

what is the production of polypeptides catalysed by?

Answer 10

enzyme peptidyl transferase (present in ribosomes)

Question 11

describe the formation of a primary structure of a protein

Answer 11

sequence of amino acids bonded by covalent peptide bonds

DNA of a cell determines the primary structure of a protein by instructing the cell to add certain amino acids in specific quantities in a certain sequence

this affects the shape and function of the protein

Question 12

describe the formation of a secondary structure of a protein

Answer 12

occurs when (weak) negatively charged nitrogen and oxygen atoms

interact with the weak positively charged hydrogen atoms

forming hydrogen bonds between polypeptide chains

Question 13

describe the formation of alpha helic

Answer 13

hydrogen bonds form within AA chain

pulling the chain into a coiled shape

Question 14

describe the formation of a beta pleated sheet

Answer 14

formed by parallel polypeptide chains that form hydrogen bonds

Question 15

describe tertiary structure of a protein

Answer 15

folding of a protein into its final shape

coiling/folding of sections into a protein’s secondary structure brings r-groups of different AAs closer together to interact

Question 16

what interactions are seen in tertiary structure

Answer 16

weak hydrophilic/hydrophobic interactions
between polar and non-polar r-groups

hydrogen bonds (weakest)

ionic bonds
formed between oppositely charged r-groups

disulfide bonds
covalently forms between AAs that contain sulfur

Question 17

describe a quaternary structure

Answer 17

results from association of more than 1 polypeptide chain (subunit) working as a functional macromolecule

protein subunits can be identical or different

Question 18

what’s the difference between hydrophobic and hydrophilic proteins?

Answer 18

proteins are assembled in the aqueous environment of the cytoplasm

so the way a protein folds depends on whether the r-groups are hydrophilic or hydrophobic

philic groups – outside the protein
phobic groups – inside of molecule shielded from water in cytoplasm

Question 19

what enzyme catalyses the break down peptide bonds?

Answer 19

protease – catalyses break down of peptides into their constituent AA

Question 20

a conjugated protein is held together by many different types of bond

which bond is not formed when a conjugated protein folds into its quaternary structure?

Answer 20

peptide

Question 21

what are the properties of globular proteins?

Answer 21

compact

water soluble

usually roughly spherical

Question 22

how are globular proteins formed?

Answer 22

found where proteins fold into their tertiary structure

where the hydrophobic r-groups are kept away from aqueous environment

hydrophobic r-groups on the outside of the protein

this is essential for regulating many of the processes necessary to life

Question 23

what’s an example of a globular protein

Answer 23

insulin

involved in blood glucose regulation

hormone, therefore has to fit into specific receptors on membrane

water soluble, so it’s able to be transported in the blood

Question 24

what’s a conjugated protein?

Answer 24

a globular protein which contains a non-protein, prosthetic group

Question 25

what's a cofactor?

Answer 25

metal ions and molecules derived from vitamins that form prosthetic groups

Question 26

what's an example of a conjugated protein?

Answer 26

haemoglobin quaternary protein made from 4 polypeptides, consisting of 2 alpha, and 2 beta subunits each subunit contains a prosthetic haem group the haem group consists of iron (II) ions which combine reversibly with oxygen

Question 27

describe the formation and function of catalase

Answer 27

enzyme quaternary protein containing 4 haem prosthetic groups iron (II) ions allows catalase to react with hydrogen peroxide to increase the rate of reaction (hydrogen peroxide is a common byproduct of metabolism and causes damage to cells when it accumulates)

Question 28

what's a fibrous protein?

Answer 28

formed from long, insoluble molecules which is due to high proportion of amino acids with hydrophobic r-groups in their primary structure the amino acid sequence in primary structure is usually repetitive which makes the structures of fibrous proteins more organised and stronger

Question 29

describe the formation and function of keratin

Answer 29

fibrous protein has large proportion of cysteine (sulfur-containing amino acid) many strong disulfide bonds (disulfide bridges) results in forming strong, inflexible, insoluble materials

Question 30

having a high degree of disulfide bonds leads to what

Answer 30

flexibility

Question 31

describe the formation and function of elastin

Answer 31

fibrous quaternary protein found in elastic fibres made from tropoelastin (stretchy molecule) gives blood vessels the elasticity to expand when needed, or go back to their normal size

Question 32

describe the formation and function of collagen

Answer 32

fibrous protein connective tissue found in skin, tendons, ligaments and nervous system most are made up of 3 polypeptides wound together in long and strong rope-like structure (gives flexibility)

Question 33

describe the secondary structure of a protein

Answer 33

secondary structure of a protein is held together by hydrogen bonds that form between the amine group of one amino acid and the carboxyl group of another These hydrogen bonds cause the polypeptide chain to coil into an alpha helix/beta pleated sheet

Question 34

how are amino acids made in: plants and animals

Answer 34

made in autotrophic green plants as products of photosynthesis which are assembled into proteins heterotrophic organisms gain amino acids from plants through food chains

Question 35

describe the difference between simple and conjugated proteins?

Answer 35

simple contain amino acids in their structure conjugated contain amino acids plus a prosthetic group

Question 36

what are the three ways the charges on a protein resulting from the pH effect may influence its behaviour

Answer 36

charges on active site affects capability of enzyme to join with its specific substrate at iso-electric point (IEP) the protein carries equal numbers of opposite charges which attract, making the protein clump together and ppt. at other pHs the proteins carry like charges which repel molecules which increase the solubility at extreme pHs the protein molecules may carry huge numbers of like charges which may exert a large repulsive force which breaks apart the hydrogen and ionic bonds holding the 3D structure together leads to denaturation since structure and functional ability is lost

Question 37

state three properties of a fibrous protein different from a globular protein

Answer 37

insoluble strong unreactive