Proteins

Question 1

why do we need proteins in our diet?

Answer 1

for growth and repair

Question 2

foods that are rich in protein

Answer 2

meat, fish, lentils, tofu, chickpeas

Question 3

what are proteins?

Answer 3

large, important molecules (polymers) found in our bodies
each protein within the body has a specific function that is related to its shape.
they are condensation polymers made up of many amino acid molecules linked together

Question 4

2 types of protein shape

Answer 4

1. fibrous (fibres, long chains)

2. globular (globule, spherical shape)

Question 5

Fibrous proteins

Answer 5

long and thin and are the major structural materials of animal tissue

Question 6

globular proteins

Answer 6

spiral chains folded into compact units.

involved in the maintenance and regulation of life processes and include enzymes and many hormones.

Question 7

Collagen

Answer 7

found in tendon, muscle, bone
functions - structural support
nature - fibrous

Question 8

Keratin

Answer 8

found in hair, skin and nails
function - structural support
nature - fibrous

Question 9

Insulin

Answer 9

found in pancreas
function - hormone to help control blood glucose levels
nature- globular

Question 10

what are proteins made up of?

Answer 10

amino acid molecules joined together

Question 11

what are amino acids?

Answer 11

the building blocks from which proteins are formed

they contain an amino (amine) group (-NH2) and a carboxyl group (-COOH) attached to the same carbon (alpha carbon)

Question 12

Structure of proteins: what is R?

Answer 12

a variable organic group or a hydrogen

Question 13

Structure of proteins: Phenylalanine

Answer 13

amine and carboxyl groups attached to carbon

R= CH2 and benzene ring

Question 14

what are essential amino acids?

Answer 14

the amino acids that cannot be made in our body.

they must be present in our diet.

Question 15

condensation polymerisation

Answer 15

condensation: molecules join together and water is eliminated.
polymerisation: single units (monomers) joining together to form a large chain of many units (polymer)

Question 16

condensation reaction

Answer 16

the amino group on one amino acid and the carboxyl group on a neighbouring amino acid join together, with the elimination of water

Question 17

what is the link that forms between two amino acids called?

Answer 17

an amide link (-CONH)

also known as peptide link

Question 18

what is a tripeptide

Answer 18

polymers made up of only 3 amino acids

Question 19

what is a polypeptide

Answer 19

polymer made up of a large number of amino acids

Question 20

structural formula of condensation polymerisation

Answer 20

-OH removed from carboxyl group and -H removed from amine group.

Question 21

when are proteins broken up?

Answer 21

during digestion process called hydrolysis to produce amino acids

Question 22

breakdown of proteins

Answer 22

a water molecule causes the splitting

N-C bond is broken

Question 23

steps for hydrolysis of proteins

Answer 23

1. identify the amide links
2. break apart C-N bonds
3. redraw individual structures
4. add -OH to make carboxyl groups and -H to complete amine group

Question 24

general condensation definition

Answer 24

when molecules join together with the elimination of a small, stable molecule (eg water)

Question 25

general hydrolysis definition

Answer 25

when large molecules are broken down into smaller molecules by reaction with water

Question 26

what is chromatography?

Answer 26

a technique that allows us to separate substances in a complex mixture

Question 27

describe paper chromatography

Answer 27

HP- hydrolysed protein (mixture of different proteins)
A-D pure samples of various amino acids

solvent added- mobile phase
the extent to which molecules travel up paper depends on size/polarity

no of spots=no of amino acids present
if spots on HP same height as amino acid A-D they are the same

Question 28

what can be done if the hydrolysed protein contains an amino acid that does not match

Answer 28

another chromatogram can be run with different known samples of pure amino acids.

Question 29

what are enzymes

Answer 29

proteins which act as biological catalysts

Question 30

Enzymes are specific for particular chemical reactions. Give an example

Answer 30

Pepsin only catalyses the hydrolysis of proteins and not any other chemical reaction

Question 31

what is the active site

Answer 31

certain sequences of amino acids form a region known as the active site
the shape of the active site allows specific reactants, known as substrates, to attach (like lock and key)

Question 32

what happens to incorrect substrates

Answer 32

they are unable to fit the shape of the active site and are not changed

Question 33

what is enzyme function related to

Answer 33

molecular shapes of proteins

Question 34

process of catalysis by enzymes

Answer 34

1. substrate approaches active site
2. substrate attaches to active site
3. substrate becomes products
4. products released and active site free to react again

Question 35

how do protein chains react with themselves

Answer 35

intermolecular bonding (often hydrogen bonding)

Question 36

intermolecular bonding in proteins

Answer 36

• gives the protein a particular shape and creates an ‘active site’ which is unique to that enzyme
• only specific, complementary substrates will fit into this active site

Question 37

denaturing enzymes

Answer 37

-when the temperature is increased too much or the acidity increases too high the intermolecular bonds will break.
-this means the protein chain will unravel, destroying the active site
-the substrate can no longer bind and so the enzyme no longer functions as a catalyst
(graph of enzyme activity vs temp/pH with narrow optimum range)

Question 38

a real-life example of denaturing proteins

Answer 38

the protein albumin in eggs becomes denatured and changes colour and texture