Biochem Chapter 6 Flashcards
Enzymes are also called
Biological Catalysts
Enzymes bind to ____ on a specific spot called the ______ _____
Substrates, Active Site
What is Activation Energy? What do Enzymes do to them?
The amount of energy chemical reactions need to move forward. Enzymes decrease the activation energy so that it does not take as much energy for the reaction to occur and therefore the reaction goes faster.
Describe the ways enzymes prepare substrates for reaction.
- The active site contains amino acid R groups that end up close to chemical bonds in the substrate, which makes the bonds easier to break
- Brings substrates together in the correct position
- Transfers electrons to or from the substrate to oxidize it, destabilising it, making it more likely to react
- Add or remove hydrogen ions to or from the substrate, destabilising it and making it more likely to react
What is the Induced Fit Hypothesis
Just prior to the substrate binding, the enzyme changes its shape or conformation, so that the active site becomes even more precise in its ability to bind to its substrate
What is a co-factor vs a co-enzyme
Cofactor - a non-protein group that binds very precisely to an enzyme (iron, copper)
Co-enzyme - water-soluble vitamins that bind to an enzyme. They shuttle molecules from one enzyme to another
List the factors that affect enzyme activity
Substrate Concentration, Enzyme Concentration, pH, Temperature
What happens when the concentration of a substrate is constant and at a high level?
the rate of reaction will be proportional to the enzyme concentration because the amount of enzyme limits the rate
When the amount of Enzyme is constant and the substrate is increasing
the rate of reaction will be increased up to the saturation level. At this maximum rate, they will combine with the substrate
pH indicates…
the concentration of hydrogen ions in a particular solution
An increase or decrease in the pH changes the ion concentration of the solution and these ions alter the structure of the enzymes either due to…
the formation of additional bonds or breakage of already existing bonds. Ultimately the chemical makeup of the enzyme and substrate are changed so the substrate can no longer identify the enzyme
What is the optimal pH for pepsin? What does it do? Where is it found? What happens to enzyme activity as the pH deviates from the optimal pH?
2, breaks down proteins in the stomach, at 6 it denatures
What is the optimal pH for trypsin? What is it and where is it found? How does this relate to the optimal pH
8, breaks down proteins in the duodenum, chyme is very acidic but the sodium bicarbonate neutralizes it bringing it up to a pH of 8
The temperature has an effect on enzyme activity in two distinct processes
- General effect on all chemical reactions - as the temp rises so does kinetic motion, more frequent collisions
- Effect on all proteins - as the temp rises, the kinetic motion of amino acid chains of enzymes increase, at the same time the strength and frequency of collisions between the enzyme molecules and any surrounding molecules also increases
Describe Competitive Inhibitors
the competitive inhibitor binds to the active site blocking access to the normal substrate and slowing the rate or reaction.
Describe Non-competitive inhibition
a non-competitive inhibitor binds to an enzyme at a location other than the active site which changes the shape of the enzyme reducing the ability of the substrate to bind efficiently
what is reversible inhibition
when the binding of the inhibitor is weak and readily irreversible.
what is irreversible inhibition
when they bind so strongly through the formation of covalent bonds that they completely disable the enzyme
Why are enzymes of extreme medical interest?
Most drugs prescribed are inhibitors.
Cyanide
a potent poison that bonds strongly to and inhibits cytochrome oxidase (key step in cellular respiration)
Penicillin
inhibits the synthesis of peptidoglycan, a key component of bacterial cell walls. Penicillin mimics the structure of the two amino acids that are normally brought together by the active site. This bond is irreversible, effectively destroying the molecule.
Allosteric Activation
Stimulates enzyme activity. It causes the active site to have a high affinity for its substrate.
Feedback Inhibition
If the product is in excess, it will slow or stop the enzymatic reaction that produces it.
If the product is scarce, inhibition is reduced therefore it increases the rate of reaction
What is lactose intolerance
Lactase digests lactose. People with lactose intolerance do not produce enough lactase therefore lactose is not digested or absorbed properly. The lactose is then consumed by bacteria in the gut which leads to symptoms including nausea, cramping, and bloating.
Chymosin
Cheese production. Bacteria is added to milk to aid in the curdling process. Lactic acid is produced as a waste product. This lowers the pH of milk and it starts to denature. Chymosin is then added to hydrolyze the milk protein (casein).
Starch to glucose
enzymes break down starch into glucose syrup
Laundry Detergent
Enzymes improve stain removal making it more effective at lower temperatures.
Brewing
Removes carbohydrates in beer
Animal Feed
degradation of the components in the feed to improve digestion
Leather
unhalving, batting, and defatting, soaking to soften hides and skins
Wine and Juice
degradation of the protein pectin for clarification and increase juice yield.
