Notes

Introduction to Kinetics

The rate of reactions is called kinetics. The activation energy of a chemical reaction is kind of like that “hump” you have to get over to get yourself out of bed. Even energy-releasing (exergonic) reactions require some amount of energy input to get going, before they can proceed with their energy-releasing steps. This initial energy input, which is later paid back as the reaction proceeds, is called the activation energy and is abbreviated. In order for the reaction to take place, some or all of the chemical bonds in the reactants must be broken so that new bonds, those of the products, can form. To get the bonds into a state that allows them to break, the molecule must be contorted (deformed, or bent) into an unstable state called the transition state. The transition state is a high-energy state, and some amount of energy – the activation energy – must be added in order for the molecule reach it. Because the transition state is unstable, reactant molecules don’t stay there long, but quickly proceed to the next step of the chemical reaction.

Activation energy and reaction rate
The activation energy of a chemical reaction is closely related to its rate. The higher the barrier is, the fewer molecules that will have enough energy to make it over at any given moment. Many reactions have such high activation energies that they basically don't proceed at all without an input of energy. The released energy helps other fuel molecules get over the energy barrier as well, leading to a chain reaction. Most chemical reactions that take place in cells are like the hydrocarbon combustion. The process of speeding up a reaction by reducing its activation energy is known as catalysis, and the factor that's added to lower the activation energy is called a catalyst. Biological catalysts are known as enzymes.

Enzymes

When we talk about catalysts in biological systems were typically talking about ensymes and the way that an enzyme might catalyze this reaction is by providing some positive charges around negative charges to pull them further away to create space so you can actually have the action proceeded. Protein complexes are things that might have a more acidic or basic environment, so you can view them as proteins, and the molecules that are going to bind to the proteins are the Substrates. So the reaction, glucose, and the atp, are going to be the substrates. The Enzyme that does that helps phosphorlate a sugar molecule is a hexokinase, that looks like protein. The ATP are one of the substrates and then the glucose are gonna bind to it. and the two substrates bind and where they are binding are called the active site, that's where the action is. It makes it more suitable for the action to take place, therefore the whole protein might bend a little more to lock them implace a little more, that is called Induced Fit.

Key Terms
Catalyst is a substance that speeds up a chemical reaction without being changed

Enzyme is A biological catalyst (usually a protein)

Substrate is The reactant molecule that an enzyme works on

Active site is The part of the enzyme where the substrate binds

Enzyme structure and function

Enzymes are catalysts. They are usually proteins, though some RNA molecules act as enzymes too.

Enzymes lower the activation energy of a reaction - that is the required amount of energy needed for a reaction to occur. They do this by binding to a substrate and holding it in a way that allows the reaction to happen more efficiently. The part of the enzyme where the substrate binds is called the active site.

Factors affecting enzyme activity
Enzyme activity can be affected by a variety of factors, such as temperature, pH, and concentration.

Queations because I wasn't really paying attention to this subject

1. The diagram below shows an enzyme binding with substrate.
You have to increase the enzyme concentration.

2. In the graph above, what might cause a reaction that originally proceeds through the path of X to change and proceed through the path Y?
The addition of catalyst

3. Which of the following is true regarding the structure of enzymes?
The active site is where the enzyme binds with the substrate.

4. How will the activity of pepsin change after it moves with the food from the stomach to the small intestine?
It will slow down because the environment is too basic.

5. n the graph above, which letter represents the activation energy
? Y; the activation energy EA is reduced in a catalyzed reaction

6. How does an enzyme influence a chemical reaction?
It speeds up the reaction rate.

7.In the graph above, which letter represents the activation energy of a catalyzed reaction and why?
Y; the activation energy is reduced in a catalyzed reaction

8.Pepsin is an enzyme found in the human stomach that breaks down protein. Pepsin will not break down starch.
Enzymes only work for specific substrates.

9. In the graph above, what might cause a reaction that originally proceeds through the path of X to change and proceed through the path Y? The addition of a catalyst

10. What is one way to increase the rate of the reaction?
Increase the enzyme concentration