2.5 Reading Check: Enzymes and their roles
Under normal conditions...
A reaction requires a certain amount of activation energy, and it occurs at a certain rate
What is equilibrium?
A state in which opposing forced or influences are balanced
Catalyst
A substance that decreases the activation energy needed to start a chemical reaction and, as a result, also increases the rate of the chemical reaction
What macromolecule category would enzymes fall under?
Almost all enzymes are proteins. These enzymes, like other proteins, are long chains of amino acids.
In which processes are enzymes involved?
Almost every process in organisms, from breaking down food to building proteins, enzymes are needed.
What's an example?
Amylase is an enzyme in saliva that breaks down starch into simpler sugars. This reaction happens millions of times faster WITH amylase than WITHOUT it
What's an example of a substrate?
Amylase only breaks down starch, therefore starch is a substrate for amylase
What does an enzyme depend on to function properly?
An enzyme depends on its structure to function properly. Conditions such as pH can affect shape and function, or activity, of an enzyme.
When would the hydrogen bonds in the enzyme begin to fall apart?
At only a slightly higher temperature than the one mentioned before ( small temp. range around organisms normal body temp.) the hydrogen bonds in an enzyme would begin to fall apart
Why do reactions usually need a catalyst?
Because they must take place very quickly, and need a catalyst in order to do so
What can a chemical catalyst change?
Both the activation energy and rate of a chemical reaction
What do enzymes do first?
Bring the substrate molecules closer together
What are enzymes?
Catalysts for chemical reactions in living things
Enzymes allow...
Chemical reactions to occur under tightly controlled conditions
Why is enzyme structure important?
Enzyme structure is important because each enzymes shape allows only certain reactants to bind to its enzyme
Where do enzymes work best?
Enzymes work best in a small temperature range around the organisms normal body temperature.
What can the lock-and-key model do?
Explain how enzymes work
In what way can/are the bonds in the substrates weakened?
In the bending of the enzyme
But when a catalyst is present...
Less energy is needed and the products form faster.
How much activation energy would be needed to break these bonds?
Less than normal to break these slightly weakened bonds
What do enzymes do?
Like other catalysts, enzymes lower the activation energy and increase the rate of chemical reactions
Are reactants found in high or low concentrations?
Low concentrations
What would the low concentration of reactants in cells do?
Make many of the reactions unlikely to take place without enzymes bringing substrates together
How can a change in pH levels affect the hydrogen bonds in enzymes?
Many enzymes in humans work best at the nearly neutral pH that is maintained within cells of the body
Are catalysts considered products or reactants?
Neither, because although they take part in chemical reactions, they aren't considered products or reactants because they are not changed or used up during a reaction
Where does the activation energy for a chemical reaction come from?
Often comes from an increase in temperature, but even after chemical reaction starts, it may happen very slowly
What have scientists found?
Structures of enzymes are not fixed in place
What happens when a substrate bonds to an active site?
The bond inside these molecules becomes strained
What happens in reactions that are reversible, like a carbon dioxide and carbonic acid reaction?
The enzymes don't affect chemical equilibrium, which means that they don't change the direction of a reaction- they just change the amount of time needed for the equilibrium to be reached
What happens when the hydrogen bonds in an enzyme begins to fall apart?
The enzymes structure changes, and it loses its ability to function
What is this idea of enzyme function called?
The lock-and-key model
What temperature do chemical reactions in organisms have to take place in?
The organisms body temperature
Why?
The reactants might not interact enough, or they may not be at a high enough concentration to quickly form the products of the reaction
What are active sites?
The specific places where substrates bind to enzymes
What are substrates?
The specific reactants that an enzyme acts on
So what happens if an enzymes structure changes?
The substrate may not work at all
What's an example of this?
The way a key fits into a lock, substrates exactly fit the active sites of enzymes
What happens if bonds are strained or stretched out slightly out of their normal positions?
They become weaker.
What happens to enzymes when they are bound to their substrates?
They bend slightly
What do enzymes do second?
They decrease the activation energy
What would be an example of this?
Think in terms of the lock and key; it's as if the lock bends around the key to make the key fit better
How could this relate to sickness?
This is one reason a VERY high fever is so dangerous to a person
