Proteins Energy and Enzymes

Question 1

What is primary protein structure?

Answer 1

• The amino acid sequence of a polypeptide

- This sequence is determined by a gene sequence

Question 2

What is secondary protein structure?

Answer 2

• Structures created due to hydrogen bonding between atoms of the polypeptide backbone
• Alpha helices or beta-pleated sheets

Question 3

What is tertiary protein structure?

Answer 3

Interactions between the side chains: HEDH

• Hydrogen bonding between polar side chains
• Electrostatic interactions between negative and positive side chains
• Disulfide bridges between two cysteine side chains
• Hydrophobic interactions between hydrophobic side chains towards the interior

Question 4

What is quaternary protein structure?

Answer 4

• Two or more polypeptide subunits coming together to form a functional protein e.g. haemoglobin has 2 alpha and 2 beta subunits
• Interactions are the same as for tertiary
• Not all proteins have multiple subunits/quaternary structure

Question 5

What happens during protein folding and unfolding

Answer 5

• Final 3D conformation is dependent on primary structure
• Chaperones are proteins that help other proteins fold by segregating unfolded proteins and providing a favourable folding environment
• Denatured proteins are unfolded and have lost their 3D structure
• Denaturation may be temporary or permanent

Question 6

What is the importance of protein structure?

Answer 6

• A change in primary structure can have consequences at all levels of protein structure
• e.g. one amino acid is different in the haemoglobin b subunit of sickle cell anaemia sufferers

Question 7

What are the types of proteins and their functions?

Answer 7

THESS

• Transport
• Hormonal
• Enzymatic
• Structural
• Storage

Question 8

What is metabolism?

Answer 8

• Chemical reactions that occur within cells
• Catabolism: breaking down organic matter to release energy
• Anabolism: using energy to produce cellular components

Question 9

What happens during reactions with regard to activation energy?

Answer 9

• Biochemical reactions are either catabolic (release net energy) or anabolic (require net energy)
• Activation energy (Ea) is the energy input needed to initiate any reaction

Question 10

What are enzymes and what do they do?

Answer 10

• Catalytic proteins that lower the Ea of a reaction
• Increase the rate of reaction
• Are not consumed
• Do not change the net energy loss/gain
• Can function in both directions
• How fast a reaction occurs depends on how much Ea is needed (lower Ea = faster reaction)

Question 11

What is active site substrate specificity?

Answer 11

• The active site of an enzyme binds its substrate
• It is often a pocket or a groove
• Induced fit is when the substrates bind and the shape of the enzyme changes to fit the substrate more closely
• Enzymes are substrate-specific
• This is determined by the shape and biochemistry of the active site
• Side groups interact with the substrate

Question 12

What are influences on enzyme activity?

Answer 12

CTPIES

• Cofactors: inorganic molecules that bind to the enzyme and are necessary for catalysis (coenzymes are organic cofactors)
• Temperature: higher temperatures increase reaction rate while too high temperatures disrupt week interactions causing denaturation
• pH: alters the charge on acid and basic side chains causing denaturation, extreme pH can lead to peptide bond hydrolysis
• Inhibitors: bind to the enzyme and inhibit the reaction by mimicking the substrate or changing the shape of the active site
• Enzyme concentration: more enzyme = faster reaction rate
• Substrate concentration: more substrate = faster reaction rate up to a point