Proteins

Question 1

What is a monomer of protein called?

Answer 1

Amino acid

Question 2

What is a dimer of a protein called?

Answer 2

Dipeptide

Question 3

What is a a polymer of a protein called?

Answer 3

Polypeptide. This is a functional protein

Question 4

What is an amino acid? And what is its structure?

Answer 4

It is the monomer of any protein molecule. It has a central carbon atom. To the right of it there is a carboxylic acid group (COOH) and to the left is an amino /amine group (NH2). Above we draw a hydrogen atom and below we put the letter r which stands for a functional group. There are 20 different functional groups and these determine what amino acid it is. Glycine would have a hydrogen atom. Cysteine would have CH2SH, which is the only functional group with Sulphur in.

Question 5

What elements do proteins mostly contain?

Answer 5

Nitrogen, carbon , hydrogen, oxygen

Question 6

What is the name for a bond between two amino acids

Answer 6

Peptide Bond

Question 7

What does a peptide Bond look like structurally?

Answer 7

A bubble is drawn around the remaining oxygen and carbon atom of the carboxylic acid and the hydrogen and nitrogen from the the amino group.

Question 8

Where does the water molecule come from in a condensation reaction between two amino acids?

Answer 8

It is the oh of the carboxylic acid group and and the bottom H of the amino group.

Question 9

What are the two types of functional proteins AKA polypeptides?

Answer 9

Metabolic / globula and structural / fibrous

Question 10

Give an example of metabolic globular polypeptide

Answer 10

Enzymes, haemoglobin, antibodies, hormones

Question 11

Give examples of structural / fibrous polypeptides

Answer 11

Collagen, keratin, myosin and actin

Question 12

What does it mean for a protein to be metabolic / globular?

Answer 12

They have metabolic roles so involved in chemical reactions and are compact. ‘Metabolic’ describes the function, globular the shape.

Question 13

What does it mean for a proteins to be structural / fibrous?

Answer 13

It means they have structural roles for example in hair and are extended rather than compact. Structural describes the function, globular the shape.

Question 14

What levels of protein structure do metabolic / globular polypeptides have?

Answer 14

Tertiary or quaternary

Question 15

What levels of protein structure do structural / fibrous polypeptides have?

Answer 15

Secondary or quaternary

Question 16

Give an example of a tertiary metabolic / globular polypeptide

Answer 16

Enzymes

Question 17

Give two examples of quaternary metabolic / globular polypeptides

Answer 17

Haemoglobin and antibodies

Question 18

Give an example of quarternary / fibrous polypeptide

Answer 18

Collagen

Question 19

What are the four levels of protein structure?

Answer 19

Primary sequence, secondary structure, tertiary structure, quaternary structure

Question 20

How many polypeptides are in a gene?

Answer 20

1

Question 21

How many peptide bonds are there in comparison to number of amino acids?

Answer 21

There is always one less peptide Bonds than there are amino acids

Question 22

Describe a primary sequence of amino acids

Answer 22

The primary sequence is non-functional and is simply a sequence of amino acids held together by peptide bonds.

Question 23

What are the two types of secondary structure proteins?

Answer 23

Alpha helix and beta pleated sheet

Question 24

Describe the alpha helix secondary structure of proteins

Answer 24

Hydrogen bonds form between between amino acids at different locations in the polypeptide chain. These bonds between oxygen and hydrogen atoms cause the polypeptide chain to coil into a helix.

Question 25

Describe a beta pleated sheet secondary structure of proteins

Answer 25

Hydrogen bonds form between hydrogen and oxygen atoms again but this time it is between two parallel adjacent chains rather than the same chain on top of itself. This means he pleated sheet forms instead.

Question 26

Can polypeptides chains exist as both alpha helix and beta pleated sheets?

Answer 26

Yes. If it is a massive polypeptide chain, the polypeptide chain can be a combination of the two.

Question 27

Describe the basics of a tertiary structure polypeptide

Answer 27

Tertiary structured polypeptides are formed when secondary structure proteins , keeping the hydrogen bonds, develop further into tertiary structure protein. They are the irregular folding of a polypeptide chain into a globular shape.

Question 28

Describe all the the additional Bonds in in a tertiary structure protein

Answer 28

More hydrogen bonds. These form in the R groups between oxygen and hydrogen atoms. Ionic bonds form between positively and negatively charged R groups e.g. NH3+ and O-. Disulfide Bridges form between pairs of cysteine amino acids. The two functional groups bond between their sulphur atoms so it's backbone-CH2-S-S-CH2-backbone. The 3rd H normally in the functional group of cysteine bonds separately so is not included here. The more disulfide Bridges, the more stable the molecule will be. Hydrophobic interactions are the last additional Bond that tertiary structure proteins have. They are where nonpolar R groups 'hide' in the centre of the protein structure . See the booklet for a better description

Question 29

What is the polypeptide chain which has not specifically bonded to anything called in a tertiary structure protein?

Answer 29

The polypeptide backbone which can either be alpha helix or beta fitted sheet and sometimes can be changing mixture of both

Question 30

What are the four extra types of bonds in a tertiary structured protein?

Answer 30

More hydrogen bonds, ionic bonds, disulfide Bridges and hydrophobic interactions

Question 31

What bonds are the strongest middle and weakest in a tertiary structure protein?

Answer 31

Hydrogen

Question 32

What is the quarternary structure protein level?

Answer 32

Where two or more polypeptide chains are bonded together. For example a potassium channel is made up of four identical chains, each 97 amino acids long. Each chain is a protein, a polypeptide, so there are four proteins present but as the chains are identical, only one Gene is required.

Question 33

Describe a fibrous protein

Answer 33

The form long fibres. There have regular, repetitive sequences of amino acids. They are insoluble in water and play structural roles. They are strong and tough

Question 34

Describe a globularProtein

Answer 34

They fold up in a compact ball like shape. They are more water-soluble and have metabolic roles. They have a wide range of amino acid sequences in their structure. They are specific to their shape. Hydrophobic r groups on amino acids turn inwards towards the centre of protein and hydrophilic R groups go on the outside.

Question 35

What does haemoglobin do?

Answer 35

Haemoglobin transports oxygen in red blood cells.

Question 36

What structure level does haemoglobin have?

Answer 36

Haemoglobin is an example of a quaternary structure. It is made out of two lots of two different polypeptides, bonded mostly by disulphide Bridges. One of the types of polypeptide is called Alpha and the other beta. So we call the polypeptides alpha subunits and beta subunits.

Question 37

How does haemoglobin transport oxygen?

Answer 37

Each subunit, a polypeptide, contains a cofactor known as a haem group that includes an iron atom in the centre. The main component that binds with oxygen is the iron. There are four subunits in each haemoglobin. Therefore, each molecule of haemoglobin is capable of carrying four oxygen molecules.

Question 38

What is a prosthetic group?

Answer 38

A tightly bound, specific non polypeptide unit, required for the biological function of some protein. They are there non amino parts of a conjugated protein and are bonded to these polypeptides by covalent bonds or weak interactions. A haem is a prosthetic group.

Question 39

What are conjugated proteins? How does this link to haemoglobin?

Answer 39

Are proteins that function in interaction with other, non polypeptide chemical groups. Each polypeptide in haemoglobin is a conjugated protein that works with its own prosthetic haem group.

Question 40

What types of collagen are there?

Answer 40

There are lots of different types of collagen and most types are fibril structures.

Question 41

Describe the structure of a collagen triple helix in terms of it's amino acids and physical shape and bonds

Answer 41

of 3 amino acids: glycine, hydroxyproline and proline. These three amino acids form a polypeptide chain where one in every 3 is glycine. Three of these 'identical' polypeptide chains then coil together in an alpha helix. Collagen has a long rigid structure made of the three polypeptides. It is sometimes called a triple helix or a triple helical structure. Each polypeptide alpha helix is held together by hydrogen bonds, forming the triple helix.

Question 42

Describe the structure of a collagen fibril

Answer 42

Triple helices line up parallel to each other and are cross-linked by covalent bonds.

Question 43

What is the function of collagen?

Answer 43

Collagen has a high tensile strength, due to its fibrous structure. It is present in skin, bone, tendons, blood vessels and cornea. This is type 1...?

Question 44

What shape is the hemoglobin molecule?

Answer 44

It is globular

Question 45

What molecule is the beta chain in haemoglobin like?

Answer 45

Myoglobin

Question 46

Haemoglobin + 4 oxygen molecules =?

Answer 46

Oxyhaemoglobin

Question 47

What conditions are needed to make oxygen separate from haemoglobin?

Answer 47

Low partial pressure of oxygen and the breakdown is made more efficient by presence of carbon dioxide or a low pH.

Question 48

What is the name given to the sequence of amino acids in a protein molecule?

Answer 48

Primary structure