Final 10 - Enzymes Flashcards
How do enzymes affect biochemical reactions?
Reduces the activation energy for a biochemical reaction to occur
- Very specific to the compounds they react with (eg: renin only works on k-casein, not a- or b-casein)
- Has optimal condition to work - pH, temperature
Do enzyme structures change after reaction?
No - enzymes are specialized proteins that speed up or start a chemical reaction without being changed by it (a catalyst - reduce activation energy needed to initiate reaction)
Describe lock-key and induced-fit model of enzymes
LOCK-KEY: substrates fit into a specific active site to form an enzyme-substrate complex
INDUCED-FIT: when substrate gets close enough it induces the active site to change its structure to match the structure, so still a perfect match. After product is released the enzyme returns to its original structure
List the 4 factors that influence enzyme activity
- water activity
- concentration of solution
- factors that denature protein
- enzyme inhibitors
Describe how water activity influences enzyme activity
- Eg: yeast needs water to facilitate enzymatic activity
- Reactions often need to happen in a solution
- WA will affect how quickly enzymes move to work on a substrate
Describe how concentration of the solution influences enzyme activity
- When you have a low amount of a substrate compared to enzymes the reaction rate is slow
- As more substrates are added reaction speed increases
- UNTIL all active sites of enzymes are blocked, at which point reaction rate slows
What factors denature proteins? Describe how they effect enzyme activity.
HEAT
• Most animal enzymes denature rapidly at temps >40C (104F)
• Why vegetables are “blanched” before freezing
PH
• Each enzyme has optimal pH range
• Enzyme denatures if pH is too high or too low
• Eg- pepsin works best around pH 1.5-1.7; rennin pH <5.8
• Adjust pH to slow undesirable enzymatic activity
IONIC STRENGTH/ELECTROLYTES
• Work as coenzyme to promote enzymatic activity (Ca2+, Fe2+)
• Stop important enzymatic activity (Hg2+, Pb2+)
• Salt, such as NaCl, binds to enzymes of bacteria
Describe how ENZYME INHIBITORS influence enzyme activity
• Any substance that will prevent the enzyme substrate complex from forming properly
- Competitive
- Uncompetitive - substance that can bind to non-active site of enzyme making so it doesn’t work
- Noncompetitive
• Naturally exist in many food products
- Natural preservatives - block bacteria’s enzymatic activity
- Eg- conalbumin in egg white, tomatin in tomato
What are positive applications of enzymes in the food industry? Give examples
- Make food texture more appealing (eg - meat tenderizer)
- Preserve food (eg - changing into cheese)
- Aid digestion (eg - lactase in milk
What are negative effects of enzymes in the food industry?
- Enzymatic browning in fruits and vegetables
- Rotting action in foods
- Fat rancidity
Why is cellulase added during juice extraction?
To clarify citrus juices or improve nutritional value
Why can pineapple be used to tenderize meat?
Raw pineapple contains an enzyme called Bromelain that is used to make meat tenderizer.
- Rapidly breaks down the protein and muscle structure of the meat and turns it into a mush over time
- Heating neutralizes the bromelain and will prevent it from giving your proteins a bad flavor
Describe enzymatic browning in fruits and vegetables
- Occurs when enzyme oxidases reacts with oxygen to produce brown pigments
- Creates structural changes that causes produce to become mushy
How can you control enzymatic browning of fruits and vegetables?
• Store fruits in oxygen-free environment • Replace CO2 with nitrogen • Reduce injuries or bruises • Denature the enzyme by blanching • Store fruits in cold temperatures • Use preservatives - Sulfites - Ascorbic acid - Citric acid - Acetic acid
What are the most common coenzymes?
Vitamins and minerals
