B3b

Question 1

What are some functions of protein?

Answer 1

• enzymes:biological catalyst
• carrier molecules: used to transport smaller molecules, e.g. haemoglobin binds to oxygen and transports it around the body
• hormones:carry messages around the body
• structural proteins:are physically strong, e.g. collagen strengths connective tissues (like ligaments and cartilage)

Question 2

How are enzymes very specific?

Answer 2

• chemical reactions usually involve things being split apart or joined together
• the substrate is the molecule changed in the reaction
• every enzyme has an active site, where it joins to its substrate to catalyse the reaction
• enzymes only work with one substrate (enzymes have a high specificity for their substrate)
• this is because, for enzymes to work, substrates have to fit into the active site. If there is no fit, the reaction will not happen (this is called the lock and key mechanism)

Question 3

How do enzymes control cell reactions?

Answer 3

• enzymes reduce the need for high temperatures to speed up reactions, as enzymes are biological catalysts
• every biological reaction has its own enzyme
• each enzyme is coded for by a different gene, and has a unique shape which it needs to do its job

Question 4

Why do enzymes need specific temperatures to function properly?

Answer 4

• a higher temperature increases the rate of reaction at first
• if too hot the enzyme will denature, the change is irreversible
• the bonds holding the enzyme together break and the enzyme loses its shape, so the lock and key mechanism is broken
• the enzyme cannot catalyse the reaction and the reactions stop
• each enzyme has its own optimum temperature when the reaction goes fastest, for humans it is 37 degrees Celsius (the same as our body temperature)

Question 5

Why do enzymes need specific pH to function properly?

Answer 5

• a pH too high or low interferes with the bonding of an enzyme, changing then shape of the active site and denaturing it
• all enzymes have an optimum pH they work at best. It is often pH 7
• not always though, e.g. pepsin breaks down proteins in the stomach and works best at pH 2

Question 6

What are Q10 values?

Answer 6

• the Q10 of a reaction shows how rate of reaction changes when the temperature is raised by 10C
• equation: =rate at higher temperature/rate at lower temperature
• a Q10 value of 2 means the rate doubled when temperature is raised by 10C, and of 3 means it trebled.

Question 7

What is a catalyst?

Answer 7

-a substance that speeds up a reaction without being changed or used up

Question 8

What is an optimum temperature?

Answer 8

-the temperature just before it gets to hot and starts to denature enzymes