Enzymes

Define metabolism

• All chemical reactions that takes place in cells/organisms.

• Molecules involved in metabolism = metabolites.

• Reactions of metabolism takes place in multiple stages with each stage catalyzed by different enzymes.

• Interlinked metabolic reaction = metabolic pathway.

• Can be anabolic or catabolic

Define statins

Competitive inhibitors. A class of drugs that lower the level of low density lipoproteins in the blood by inhibiting the activity of an enzyme involved in the production of cholesterol in the liver.

List examples of enzymes, their location/secreted from, and function

Amylase- salivary glands/pancreas - breaks down startches into sugars
Lipase- pancreas into small intesine - breaks down lipids into fatty acids and glycerol
Protease- stomach/pancreas/small intestine- breaks down proteins into smaller peptides/amino acids

Maltase - small intestine- breaks down maltose into 2 glucose

Lactase - small intestine- breakds down lactose into glucose and galactose

Explain the difference between reversible and irreversible enzyme inhibition.

Reversible inhibition: Inhibitor binds to enzyme/enzyme-susbtrate complex whith a non-covalent/temporary bond. It can removed by dialysis/dilution

Irreversible inhibtion: Inhibitor bings covalently to enzyme = permananent= enzyme is inactivated. Penicillin binds covalently to enzyme involved in bactieral cell wall synthesis

Define denaturation

• Denaturation is loss of 3D/tertiary structure of enzyme/protein due to breaking of hydrogen bonds/ionic bonds/disulfide bridges

• High temperatures cause increaed kinetic energy/vibration of molecules which breaks bonds holding 3D structure of enzyme

Distinguish between an extracellular and intracellular enzyme

Extracellular enzyme: Syntehsiezed within cell but then secreted to extracellular space such as digestion and breakwing down (amylase and lipase in pancreas)

Intracellular enzyme: Found in cytoplasm and bound to cell organelles (ex ribosomes). Catalyze reactions that occurs inside cell (glycolysis, Krebs Cycle). Exmaples of intracellular enzyme = DNA polymerase

Detail the role of enzymes in metabolism

Enzymes are globular proteins with specific forms/structures which is crucial as these are the active sites to which substrates bind to.They are specific to substrate (enzyme-substrate specificity) meaning that the chemical properties of enzyme + substrate = complementary which means they fit together because of the specific differences in their shapes.

Compare and contrast between anabolic and catabolic reactions and provide 3 examples of each

Anabolic reaction:

• Synthesis of complex molecules from simple molecules to form macromolecules.

• Energy-requiring/endergonic reactions.

• Condensation reactions

• Stores energy in chemcial form

• Growth, repair, and energy storage

• (Ex: photosynthesis, protein sythesis)

Catabolic reactions:

• Breakdown of complex molecules into simple molecules by hydrolysis.

• Energy-releasing/exergonic reactions.

• Hydrolysis reactions

• Digestion, excretion, energy supply

• Releases chemical energy as heat/movement/active transport

• (Ex: digestion of food, breaking down glycogen for energy (cell respiration), breakdown of musle tissues)

Both:

• Enzyme-catalyzed reactions

• ATP required

List the factors of enzyme activities

Temperature: Higher temperatures = increase kinetic energy = more collisions with substrate and enzymes = higher proability of substrate binding to active site = increase rate of enzyme activity. After optimum temperature = enzyme activity decreases rapdily as enzyme is denatured

pH level: Enzymes have optimum pH range where activity is highest. Outside range = decreases due to changes in active site

Substrate concentration: Higher substrate concentration = more changes for substrates to collide/bind to active site = enzyme activity increases. Plateaus as maz enzyme activity is reach (no more susbtrates)

Explain why the shape of enzymes is important in enzyme action

Enzymes are highly specific in their action because of the way it binds to the active site which is a crevice/pocket in the protein.

Describe how an enzyme functions and its role in metabolism

Enzyme catalysis involves molecular motion and collision of substrates with active sites in enzyme. Substrate must collide at random with enzyme’s active site with correct orientation and speed in order for reaction to occur. Unsuccessful collision = molecules not correcly aligned with eachother at moment of collision/bounce off eachother = no reaction.

When substrates bind to enzymes a temporary enzyme-substrate complex is formed. The active site of an enzyme has a specific shape and chemical properties that binds with the ubstrate leading to a change in chemical strucrture of the substrate.

Products are formed and substrates detach and move away from active site so enzyme can be reused.

Outline the structure of the enzyme’s active site

• Made of few amino acids/residues that interact with eachother to form complex 3D shape

• Crevice/pocket on enzyme surface

Describe the induced-fit hypothesis

Model that illustrates how enzyme and substrate interacts. The previous (inaccurate) model was the lock-and-key model that states that enzyme active site is precisely complementary to the shape of the substrate molecule. The induced-fit states that actice site can sometimes change shape slightly (conformational change) for ideal binding arrangement of substrate.

List the advantages of enzymes

• Reusable (small number need to catalyze enzymes)

• Remaines unchanged from reactions

• Increases rate of chemical reactions in order to support life by decreasing the activation energy required to change substrate into product

Distinguish between allosteric inhibitor/site, end-product/feedback inhibition, competitive/non competitive inhibition

Allosteric: Inhibitor binds to location on enzyme that is not active site (allosteric/regulatory site) inducing conformational change in the enzyme to prevent it from binding to the substrate.

End-product/feedback: Final product of metabolic pathyway inhibits enzyme that catalyzes an earlier step in the pathway by binding to an allosteric site. It halts the production of end product (prevents overproduction of end product).

Competitive: Competive inhibitor molecule competes with substrate to bind to active site of enzyme, blocking the susbtrate from binding. Competive inhibitor and substrate = similar structure so both can bind to same location on enzyme. It is reversible (enzyme can be reused).

Non-competitive: Inhibitor binding to allosteric site. No competiton with substrate because they are not binding to same location on enzyme. Binding of non-competitive inhibitor alters enzyme’s conformation (allosteric site) = less effective at catalyzing reaction.

Describe immbolized enzymes and their uses

• Immobilized enzymes are enzymes that have restricted mobility and attatched to an inert, insoluble material making them resuable and improve their stability

• Immbolization allows multiple usability which efficient and cost-effective

• Greater tolerance of temeperature and pH changes

• Substrates exposed to higher enzyme cocnentration = increases reaction rate

• Conditions can be controlled carefully = perform at optimal conditions = more stable

• Products can be seperated easily from enzymes