1.6- PROTEINS

Question 1

What is the size of proteins usually?

Answer 1

usually very large molecules

Question 2

How are the types of carbohydrates and lipids in all organisms in terms of number + structure?

Answer 2

relatively few and they are very similar

Question 3

Something about the shape of proteins in comparison to each other?

Answer 3

shape of any one type of protein molecule differs from that of all other types of proteins

Question 4

How significant are proteins in living organisms?

Answer 4

very important

Question 5

What does the word “protein” mean in greek?

Answer 5

“of first importance”

Question 6

How involved are enzymes?

Answer 6

enzymes involved in almost every living process

Question 7

What is amino acids used as?

Answer 7

basic monomer units which combine to make up a polymer

Question 8

What is the name of the polymer made up of amino acids?

Answer 8

polypeptide

Question 9

When polypeptides are combined what do they form?

Answer 9

proteins

Question 10

About how many amino acids have been identified?

Answer 10

about 100 amino acids

Question 11

How many amino acids occur naturally in proteins?

Answer 11

20

Question 12

What does the fact that the same 20 amino acids occur in all living organisms provide indirect evidence for?

Answer 12

evolution

Question 13

What does every amino acid have?

Answer 13

a central carbon atom to which are attached four different chemical group

Question 14

What are the four different chemical groups attached to the carbon in an amino acid?

Answer 14

-NH₂
-COOH
-H
R group

Question 15

Through what process do amino acid monomers combine to form a dipeptide?

Answer 15

condensation reaction

Question 16

How is the water formed in the condensation reaction between amino acids?

Answer 16

combining an -OH from carboxyl group of one amino acid with -H from amino group of another amino acid

Question 17

How do the two amino acids become linked?

Answer 17

by a peptide bond

Question 18

Where is the peptide bond between?

Answer 18

between the carbon atom of one amino acid and nitrogen atom of other

Question 19

How can a peptide bond of a dipeptide bond be broken and what is left?

Answer 19

through hydrolysis to give two constituent amino acids

Question 20

What is the process called when a series of condensation reactions happen, joining many amino acid monomers?

Answer 20

polymerisation

Question 21

What is the resulting chain of many hundreds of amino acids called?

Answer 21

polypeptide

Question 22

What is the primary structure of any protein?

Answer 22

sequence of amino acids in polypeptide chain

Question 23

How is the sequence of amino acids in a polypeptide chain determined?

Answer 23

determined by DNA

Question 24

How is there a limitless number of primary protein structures?

Answer 24

as polypeptides have many (usually hundreds) of the 20 naturally occurring amino acids joined in different sequences, there’s a limitless number of combinations

Question 25

What does the primary structure determine?

Answer 25

its ultimate shape and hence its function

Question 26

What can a change in a single amino acid in the primary sequence lead to?

Answer 26

lead to a change in the shape of protein + may stop it from carrying out function

Question 27

What is the protein's shape very specific to?

Answer 27

its function

Question 28

What can happen if the shape of a protein is changed?

Answer 28

it will function less well or differently

Question 29

What may a simple protein consist of?

Answer 29

consist of a single polypeptide chain

Question 30

More commonly, what does a protein consist of?

Answer 30

made up of a number of polypeptide chains

Question 31

What does the linked amino acids that make up a polypeptide possess?

Answer 31

-NH and -C=O groups on either side of peptide bond

Question 32

What overall charge does the hydrogen on -NH have?

Answer 32

an overall positive charge

Question 33

What overall charge does the O of -C=O group have?

Answer 33

overall negative charge

Question 34

Due to the charge of the hydrogen on -NH and charge of O on -C=OH what happens?

Answer 34

readily form weak bonds called hydrogen bonds

Question 35

What does the hydrogen bond between the O and H cause?

Answer 35

the long polypeptide chain to be twisted into a 3D shape

Question 36

What can the 3D shape?

Answer 36

alpha helix or beta pleated sheets

Question 37

What happens in the tertiary structure?

Answer 37

secondary protein structure can be twisted and folded even more

Question 38

What does the further folding and twisting produce?

Answer 38

gives a complex, and often specific 3D structure of each protein

Question 39

How is the tertiary structure maintained?

Answer 39

by a number of different bonds

Question 40

How is where the bonds in the tertiary structure determined?

Answer 40

depends on the primary structure of protein

Question 41

What are the bonds in the tertiary structure?(3)

Answer 41

disulfide bridges ionic bonds hydrogen bonds

Question 42

How strong are disulfide bridges?

Answer 42

fairly strong so not easily broken

Question 43

Where are ionic bonds formed?

Answer 43

Formed between any carboxyl and amino groups that are not involved in forming peptide bonds

Question 44

How strong are ionic bonds and how are they broken?

Answer 44

weaker than disulfide bonds and easily broken by change in pH

Question 45

How strong are hydrogen bonds + numbers?

Answer 45

numerous but easily broken

Question 46

What is important for the function of protein?

Answer 46

3D shape of protein

Question 47

What does the 3D shape allow?

Answer 47

makes each protein distinctive and allows it to recognise, and be recognised by other molecules

Question 48

What does proteins being able to interact with other molecules enable?

Answer 48

it can interact with them in a very specific way

Question 49

What do large proteins often form?

Answer 49

form complex molecules containing a number of individual polypeptide chains that are linked in various ways

Question 50

What other groups may also be associated with the molecules in the quaternary structure?

Answer 50

non-protein (prosthetic) groups

Question 51

Example of prosthetic group on protein?

Answer 51

iron-containing haem group in haemoglobin

Question 52

What determines the 3D structure in the first place?

Answer 52

the sequence of amino acids (primary structure)

Question 53

What is the most reliable test for proteins?

Answer 53

Biuret test

Question 54

What does the Biuret test detect?

Answer 54

peptide bonds