Proteins + Enzymes

Question 1

What are the monomers of proteins?

Answer 1

Amino acids

Question 2

What type of bond is present after the condensation reaction of amino acids takes place?

Answer 2

Peptide bonds

Question 3

What is the general structure of a protein?

Answer 3

NH2 represents an amine group,
COOH represents a carboxyl group
R represents a side chain.
And a normal C-H

Question 4

What does a functional protein contain?

Answer 4

It contains one or more polypeptides.

Question 5

Primary Structure

Answer 5

The sequence of amino acids linked together to form a polypeptide chain.

Question 6

Secondary structure

Answer 6

This is where hydrogen bonding can form making the protein change into an alpha helix or beta pleated sheet.

Question 7

Tertiary structure

Answer 7

This is where the protein can be twisted and folded more to give a more complex, 3D shape. This is maintained by bonds called dilsulfide bridges,
ionic bonds and hydrogen bonds.

Question 8

Quarternary structure

Answer 8

Occurs in proteins that have more than one polypeptide chain working together as a functional macromolecule, for example, haemoglobin

Question 9

Describe how the different types of bonds work in the tertiary structure.

Answer 9

disulfide bridges - fairly strong so not easily broken

ionic bonds - easily broken by changes in pH and are only formed between the carboxyl and amino groups

hydrogen bonds- numerous but easily broken as they are the weakest type of bond

Question 10

Globular proteins

Answer 10

Globular proteins are compact, roughly spherical in shape, and soluble in water

Question 11

Fibrous Proteins

Answer 11

Fibrous proteins are long strands of polypeptide chains that have cross-linkages due to hydrogen bonds

Question 12

Describe the test for proteins

Answer 12

Add NaOH to make the sample alkaline
Then add Biueret solution
If proteins are present the colour will change from blue to purple.

Question 13

Induced fit model

Answer 13

Enzymes are specific to substrates they bind to meaning that only one type of substrate fits into the active site of the enzyme. When the enzyme and substrate bind they form an enzyme-substrate complex and the structure of the enzyme is altered so that the active site of the enzyme fits around the substrate

Question 14

Lock and Key Theory

Answer 14

The shape of the active site matches the shape of its substrate molecules.

Question 15

Define ‘Enzyme’

Answer 15

Enzymes speed up reactions by lowering the activation energy of a reaction and in doing so they provide an alternative energy pathway

Question 16

How do the properties of enzymes relate to their tertiary structure?

Answer 16

The tertiary structure of an enzyme determines the structure of its active site, and therefore its substrate binding ability. This makes the enzyme and its substrate complementary

Question 17

How does temperature affect enzyme activity?

Answer 17

The rate of reaction increases up to the optimum temperature as the kinetic energy of the enzyme increases. However, above the optimum temperature, the rate of reaction decreases beyond the optimum temperature as the enzyme becomes denatured.

Question 18

How does pH affect enzyme activity?

Answer 18

pH affects the enzyme’s shape as it can disrupt the bonds in the tertiary structure of the enzyme.
It needs specific conditions if the pH is too high or too low the enzyme will not work.

Question 19

How does substrate concentration affect enzyme activity?

Answer 19

The rate of reaction increases as enzyme concentration increases as there are more active sites for substrates to bind to, however, increasing the enzyme concentration beyond a certain point has no effect on the rate of reaction as
there are more active sites than substrates so substrate concentration becomes the
limiting factor.

Question 20

How does enzyme concentration affect enzyme activity?

Answer 20

As the concentration of substrate increases, the rate of reaction increases as more enzyme-substrate complexes are formed. However, beyond a certain point the rate of reaction no longer increases as enzyme concentration becomes the
limiting factor.

Question 21

How does non-competitive inhibition affect enzyme activity?

Answer 21

As concentration on non-competitive reversible inhibitors increases, the rate of reaction decreases as the shape of the enzyme (not the active site) is altered by the inhibitors.

Question 22

How does competitive inhibiton affect enzyme activity?

Answer 22

As the concentration of competitive reversible inhibitors increases, the rate of reaction decreases as the active sites are temporarily blocked by inhibitors so substrates cannot bind to them.