Protein

Question 1

Draw and label a diagram of an amino acid.

Answer 1

A carbon atom with a carboxyl (COOH) and an amino group (NH2) attached on either side.
They have a hydrogen above or below the carbon atom.
And then also an R-group above or below the carbon atom.

Question 2

Identify the part of an amino acid which is variable.

Answer 2

The R-group is the variable part of an amino acid.

There are 20 different types of R-group

Question 3

State how many amino acids occur in life.

Answer 3

20

Question 4

Draw a labelled diagram demonstrating the condensation of peptide bonds.

Answer 4

Condensation reaction- a peptide bond connects amino acids forming a dipeptide. This happens between the carboxyl group on one amino acid and the amino group of another amino acid and releases water (from and OH of the carboxyl group and H from the amino group)

Question 5

Draw a labelled diagram demonstrating the hydrolysis of peptide bonds.

Answer 5

Hydrolysis reaction- the breaking of peptide bonds using water.

Question 6

Draw a dipeptide and label the peptide bond.

Answer 6

2 amino acids connected with a bond between the carbon atom and the nitrogen atom.
Draw it

Question 7

Explain how the variety of amino acids leads to a wide range of dipeptides and very quickly to an incredible variety of polypeptide chains.

Answer 7

because the R-group in amino acids is variable so when they are sequenced together in a condensation reaction the resulting polypeptide chain is very different.

Question 8

Define the terms “polypeptide chain”

Answer 8

A molecule formed from more than 2 amino acids

Question 9

Define the term protein

Answer 9

1 or more polypeptide chains arranged as a complex macromolecule

Question 10

Describe how one end of a polypeptide chain differs from the other end.

Answer 10

In a polypeptide the NH and the CO groups are polar.

The H atom is slightly positive and the O atom is slightly negative. So hydrogen bonding can form between them.

Question 11

Define the term “primary structure” of a protein and describe how it is held together.

Answer 11

Its the sequence of amino acids in the polypeptide chain. Different proteins have different sequences of amino acids in their structure. Its held together by peptide bonds between the amino acids.

Question 12

Define the term “secondary structure” of a protein

Answer 12

Secondary structure- Hydrogen bonds forms between the -NH and -CO groups of amino acids in the same chain. This forms either an alpha helix coil or a beta pleated sheet

Question 13

Describe the structure of an alpha helix coil

Answer 13

Hydrogen bonds may form within the amino acid chain pulling it into a coil shape

Question 14

Describe the structure of a beta pleated sheet

Answer 14

Poly peptide chains can also lie parallel to each other with hydrogen bonds forming between them forming a sheet-like structure. The pattern formed by individual amino acids causes the structure to appear pleated.

Question 15

Define the term “tertiary structure” of a protein, and describe how it is held in place (include all the different possible bonds).

Answer 15

The folding of a protein into its final shape it often includes sections of secondary structure. the coiling or folding of sections of proteins into their tertiary structures brings R-groups of different amino acids close enough together to interact and further folding will occur.

Question 16

State all the interactions that occur in tertiary structure

Answer 16

1. Hydrophobic and Hydrophillic interactions
2. Hydrogen bonds
3. Ionic bonds
4. Disulfide bonds

Question 17

Describe the Hydrophobic and Hydrophillic interactions in the tertiary structure

Answer 17

When Hydrophobic R-groups are close together in the protein, they tend to clump together. This means that hydrophillic R-groups are more likely to be pushed to the outside which affects how the protein folds up into its final structure.

Question 18

Describe the hydrogen bonds in the tertiary structure

Answer 18

These weak bonds form between slightly positively- charged hydrogen atoms in some R-groups and slightly negatively-charged atoms in other R-groups on the polypeptide chains.

Question 19

Describe the ionic bonds in the tertiary structure

Answer 19

these are the attractions between the negatively-charged R groups and positively-charged R groups on different parts of the molecule

Question 20

Describe the disulfide bonds in the tertiary structure

Answer 20

These are covalent and the strongest of the bonds but only form between R-groups that contain sulfur atoms

Question 21

Explain how the primary structure of a protein determines its tertiary structure.

Answer 21

the sequence of variable groups(the primary structure) and how they interact with each other through hydrogen and sulfide bonds will determine the secondary structure (alpha helices and beta pleated sheets) which will help determine the structure.

Question 22

Define the term “quaternary structure” of a protein, and describe how it is held in place (include all the different possible bonds).

Answer 22

Quaternary structure results from the association of two or more individual proteins called sub-units. the interactions between the sub-units are the same as in tertiary structure except they are between different protein molecules rather than within one molecule.

Question 23

Define the terms “globular protein”

Answer 23

1. They are spherical water-soluble proteins.
2. In globular proteins the hydrophillic R-groups on the amino acids tend to be pushed to the outside of the molecule.
3. This is caused by the hydrophobic and hydrophillic interactions in the protein’s tertiary structure.
4. This makes globular proteins soluble so are easily transported in fluids.

Question 24

Define the terms “fibrous protein”.

Answer 24

1. They are an insoluble and rope shaped protein.
2. They are very strong and are structural proteins and are fairly unreactive.
3. They are formed from long insoluble molecules. this is due to the presence of a high proportion of amino acids with hydrophobic R-groups in their primary structure .
4. They contain a limited range of amino acids usually with small R-groups.
5. They aren’t folded into complex 3D shapes like globular proteins

Question 25

Define the terms “prosthetic group”

Answer 25

A non protein component of a conjugated protein

Question 26

Define the terms “conjugated protein”.

Answer 26

A protein with a non-protein group attached. they are globular proteins.

Question 27

Haemoglobin

Answer 27

1. Its a globular protein and has quaternary structure
2. Carries blood around the body in red blood cells
3. It has a prosthetic group attached to it so is a conjugated protein.
4. Each of the 4 polypeptide chains in haemoglobin has a prosthetic group called haem
5. A haem group contains iron which oxygen binds to

Question 28

Inuslin

Answer 28

1. Its a globular protein with a Quaternary structure
2. Its a hormone secreted by the pancreas to help regulate blood glucose level .
3. Soluble- it can be transported in the blood to the tissues where it acts
4. It consists of 2 polypeptide chains which are held together by disulfide bonds.
5. when in pancreas 6 of these molecules binds together to form a large globular structure

Question 29

Amylase

Answer 29

1. Its a globular protein
2. Its an enzyme which catalyses the breakdown of starch
3. It is made of a single chain of amino acid
4. its secondary structure contains both alpha-helix and beta-pleated sheet sections
5. Most enzymes are globular proteins

Question 30

Collagen

Answer 30

1. A fibrous protein
2. Found in animal connective tissues such as bone, skin and muscle
3. very strong molecule
4. Minerals can bind to the protein to increase rigidity

Question 31

Keratin

Answer 31

1. Fibrous protein
2. Found in many of the external structures of animals such as skin, hair, nails, feathers and horns
3. Can be flexible or hard and tough

Question 32

Elastin

Answer 32

1. Fibrous protein
2. Found in elastic connective tissue such as skin, large blood vessels and some ligaments.
3. It’s elastic so allows tissues to return to their original shape after they have been stretched