Theme C: Interaction and Interdependence

Enzymes

are biological catalysts made of protein. 

Enzyme Active Site

Most important of an enzyme , it must be complementary to the substrate, allowing for the formation of an enzyme-substrate complex.

Alcohol Metabolism: Alcohol Dehydrogenase

 Ethanol (alcohol) is first metabolized in the liver by the enzyme ADH into acetaldehyde.

Aldehyde Dehydrogenase

Acetaldehyde is then further metabolized by ALDH into acetate, which is non-toxic and can be used in the body for energy production.

What do enzymes do?

 presence of enzymes in cells and organisms that enables these reactions to occur at incredible speeds, in an orderly manner, yielding products that the organism requires, when they are needed.

Effectiveness of Catalysts

• are effective in small amounts

• remain unchanged at the end of the reaction.

Characteristics of enzyme

• Enzymes are highly specific in their action, which makes them different from most inorganic catalysts.

• Enzymes are specific because of the way they bind with their substrate at the active site.

Active site

• is a region of an enzyme molecule where the substrate molecule binds.

• the binding point

How do they work?

• the starting substance is called the substrate, and what it is converted to is the product. 

• An enzyme works by binding to the substrate molecule at a specially formed pocket in the enzyme. 

Enzyme Active Site

• At the active site, the arrangement of a few amino acid molecules in the enzyme matches certain groupings on the substrate molecule, enabling the enzyme–substrate complex to form.

• As it forms, it seems a slight change of shape is induced in the enzyme molecule (induced-fit hypothesis)

How does this occur

Enzymes are developed from DNA into Mrsna and then into protein

• there are amino acids in the active site that are complementary and those different ions associatied with the enzumes can cause new ionic bonds or carboxyl or sulfate groups

• then the product is released into the body. for example, once the glucose goes into the active site there is a change in conformation.

Extracellular enzymes

enzymes produced in a cell that are moved out of the cell to carry a specific conditions. Pepsin is the principal enzyme involved in protein digestion (produce in gastric glands). 

It breaks down proteins into smaller peptides and amino acids that can be easily absorbed in the small intestine.

Intracellular enzymes

DNA polymerases are enzymes that create DNA molecules by assembling nucleotides.

Produce whitin most cells.

catabolism

 proccess where complex molecules breakdown into simpler molecules

• the hydrolysis of macromolecules into monomers.

Anabolism

the process of synthesis of complex molecules from simpler molecules

• formation of macromolecules from nonomers by condensation reaction.

Alcohol dehydrogenase

is produce in the cytosol of stomach and liver cells and functions as the main enzyme for alcohol metabolism. 

Metabolism

• only occur in the presence of specific enzymes.

involves metabolites that are molecules that allow chemical reactions

Extraceullar vs. Intraceullular enzymes

• are exported from cells, such as the digestive enzymes. 

  • Enzymes like these are parcelled up and secreted, and they work externally.

• enzymes remain within cells and work there. 

• There are enzymes that are always present in the organism, and other are produce when needed. 

Movement

needed for a substrate molecule and an active site to come together. 

Kinetic energey

• The greater the kinetic energy of enzyme and substrate, the greater the chance of collisions between molecules and the formation of enzyme–substrate complexes.

Immobilized enzymes

• an enzyme attached to an inert, insoluble material, enabling recovery, reuse and improved enzyme stability.

• example: Enzymes immobilized on (or in) a membrane (EIM) is a widely used method in food processing, pharmaceuticals and wastewater treatment.

Advantages of Enzyme immobolization

 permits reuse of the enzyme preparation

- the product is enzyme free

- the enzyme may be much more stable and long lasting, due to protection by the inert matrix.

Enzymes can be denatured

denaturation

•  is a structural change in a protein that alters its three-dimensional shape.

• Temperature rises and changes in pH of the medium may cause denaturation of the protein of enzymes. 

  • Fibrous proteins tend not to denature as easily as globular proteins.

how does this occur?

The rate of an enzyme-catalysed reaction is sensitive to environmental conditions. denaturation is specifically true for nzymes, which are large, globular proteins where a small part of the surface is an active site.

Tripsin

digestive enzyme that breaks down proteins in the small intestine.

Is produce by the Acinar cells.

• Malfunction of the CFTR gene affects pancreatic enzyme secretion, leading to poor digestion.

• basically malfunction affecting enzyme secretion leads to digestive issues.

DNA Polymerase

an enzyme responsible for synthesizing DNA during replication.

Importance of DNA Polymerase

Mutations affecting its function can result in cancer (due to uncontrolled cell growth) or mitochondrial disorders (due to defective mtDNA replication). Understanding these mechanisms helps in developing targeted therapies, such as DNA polymerase inhibitors for cancer treatment or mitochondrial-targeted therapies for POLG-related diseases.

• therefore it is essential for maintaining genetic stability

Example of denaturation due to temperature

• As the temperature increases so does the rate of enzyme activity.  An optimum activity is reached at the enzyme's optimum temperature. A continued increase in temperature results in a sharp decrease in activity as the enzyme's active site changes shape. Leads to denaturation.

Example of denaturation due to pH

As pH increases, enzyme activity rises, peaking at the optimum pH (8). Beyond this, activity sharply declines as the active site changes shape, leading to denaturation. pH measures a solution's acidity or basicity.

Concentration affecting enzyme activity

As substrate concentration increases, enzyme activity rises, reaching an optimum rate. Beyond this, activity plateaus as all enzyme molecules are occupied, limiting further breakdown.

Activation Energy

energy required by a substrate molecule before it can undergo a chemical change.

how it works;

Activation energy is the initial energy required to weaken substrate bonds, forming the transition state. Energy is then released as the substrate converts into the product.