Please review my notes on enzymes

[minajneb]

I was just going over my parts of my enzyme notes and started to question the detail. Am I doing too much or not enough?

Here is the example:

Structure and regulation of biochemical pathways

What is an enzyme?

A substance (protein) produced by a living organism which acts as a catalyst to bring about a specific biochemical macromolecular biological catalyst reaction

•    the role of enzymes as protein catalysts in biochemical pathways

Features of enzymes

Most enzymes are globular proteins that have a tertiary or quaternary structure
The main features of enzymes are their specificity and catalytic power

Specificity

Different enzymes act as catalysts for different biochemical reactions by binding to a specific type of molecule called a substrate
Although evolved to be highly specific, some enzymes can act on multiple substrates
The active site is a key structure of enzymes
The active site is a pocket or groove-like part of the enzyme formed by the tertiary folding of the protein
Each active site is a complex three-dimensional shape that interacts with a specific substrate to catalyse a specific reaction
When an active site binds to a substrate it forms an enzyme-substrate complex
When a substrate enters an active site it forms an enzyme-substrate complex. The substrate then exits the enzyme-substrate complex as a product molecule
Enzymes are not consumed when they catalyse reactions

Enzyme-substrate interaction models

Enzymes and their substrate interact through two models:

Lock and key: Is when the enzyme and the substrate fit together like a lock and key. No reaction will occur if the ‘key’ does not fit the ‘lock’
Induced-fit model: Is when a substrate binds to the active site of an enzyme and a change in shape (or conformational change) of the active site occurs. Know as a more accurate representation of a enzyme-substrate interaction, as the active site is flexible and capable of changing shape in order to conform to the shape of the substrate and achieve a tighter fit

Enzyme catalysis

Catalytic power - Enzymes make reactions occur more quickly compared to the reaction occurring without the enzyme

Reactions are often reversible and so can often be catalysed in both directions
substrate > product, and product > substrate - although this is not always the case as some reactions of glycolysis are reversible, but others are not
Usually different enzymes catalyse a reaction in each direction. For example, DNA polymerase builds up DNA and DNAse breaks it down. The direction will depend on the concentration of substances and products, as well as on the energy requirements
Enzymes are not consumed when they catalyse reactions and therefore can be used over and over again

Enzymes reduce activation energy

All reactions need an input of energy to start, this is called activation energy
Whether a reaction releases or consumes energy, activation energy is needed for the reaction to start
The catalytic power of enzymes comes from their ability to reduce activation energy, thus less energy is required for the reaction to occur

Enzymes reduce activation energy by influencing:

Proximity and orientation:  Enzymes bring the parts of molecules involved in the reaction closer to each other in the active site and position them where a reaction is more likely to occur
The micro environment: most active sites are hydrophobic. The absence of water results in a non-polar environment, allowing stabilising interactions such as hydrogen bonds, \hydrophobic and van der Waals interactions to occur
Ion exchange: The amino acids in the active site can often take the H+ ions from, or donate them to the substrate, to facilitate steps in certain reactions

Enzymes regulate biochemical pathways

Many chemical processes occur as a sequence of reactions in which each reaction is catalysed by a specific enzyme and the product of one reaction becomes the substrate in the next reaction
Such sequences of biochemical reactions form biochemical pathways
Some biochemical pathways are linear, some are branched (leading to many final products), and others are cycles
An example of a cyclic pathway is the Calvin-Benson cycle

Metabolism

Metabolism is the collection of all the biochemical (or metabolic) reactions that that occur in living cells

Metabolic reactions can be catabolic or anabolic

Catabolic reactions: reactions where the substrate is broken down and energy is released. Catabolic reactions are exergonic because they release energy
Anabolic reactions: Reactions that require an input of energy in order to produce larger molecules from smaller substrates. Anabolic reactions are endergonic because they require energy. The energy is required to form bonds between molecules
Some reactions require an input of energy because they are not energetically favourable. This need for energy is addressed by coupling biochemical pathways, so a reaction that requires energy is put together with a reaction that requires energy. This coupling ensures the reaction takes place

•    the mode of action of enzymes including reversible and irreversible inhibition of their action due to chemical competitors at the active site, and by factors including temperature, concentration and pH

Factors that regulate Enzyme Activity

The amounts of final products and the speed at which they are produced in a biochemical pathway can be controlled through the regulation of individual reactions that make up that pathway
Slowing down one reaction will have an effect on all subsequent reactions, as each reaction in a biochemical uses the product from the previous reaction as a substrate
Enzymes have specific conditions in which they perform best. When conditions are optimal, enzyme activity is at its highest and the rate of reaction is at its fastest. Factors include temperature, pH and the concentration of the substrate and the enzyme. Other factors such as inhibitors, phosphorylation, and cofactors and coenzymes, regulate the activation and inhibition of enzymes and determine whether they can catalyse at all, rather than the rate at which reactions occur

Temperature

Enzyme-catalysed reactions will generally increase as the temperature increases. This is because the warmer particles become during a reaction, the more rapidly they move, which make collision more likely to occur
Enzymes (proteins) can become denatured at high temperatures. This occurs by the shape of the enzyme changing, so the substrate cannot bind to the enzyme and the reaction cannot take place. The hydrogen bonds and hydrophobic interactions that create the tertiary and quaternary structures become broken
Human enzymes have an optimum temperature of 36-38 degrees matching normal body temperature of approximately 37 degrees
If enzymes are cooled down below optimum temperature, particles will move more slowly and  the rate of reaction will slow down. In addition, the bonds are not as flexible at lower temperatures and conformational change (induced fit) will not occur. Reaction rate will increase again if the enzyme is reheated

[blue-pants]

Looks fine
Maybe a bit too much detail but you cover more than just the dotpoints mentioned ~ detail is never a bad thing as well.