IB Biology HL: Enzymes

Metabolism

All of the chemical reactions that take place in an organism

Metabolic Pathway

A series pf enzymes involved in creating an end product. Respiration and photosynthesis are examples.

Catabolic Reaction

• macromolecules broken down into small molecules

• ATP released

• eg. hydrolysis

Anabolic Reaction

• macromolecules created from smaller molecules

• ATP used

• eg. condensation

Pectinase

Enzyme used to increase volume of juice from fruit

Lactase

Enzyme used to convert lactose into glucose and galactose

pH,Tempatures, and Salinity

Environmental factors that can affect the function of an enzyme

Substrate

Molecule that will be changed by an enzyme

Decribe the steps on enzyme action?

• substrate binds to active site due to chemical specificity

• bonds in substrates are weakened causing it change

• products seperate

How are immbile enzymes used in Lactose free milk?

• milkcontaing lactose poured through container with alginate beeds with immobilised lactose

• lactose converted into glucose as milks flow through

Benefits of immobilised enzymes:

• can be reused multiple times

  • cheaper

  • time-efficient: no need to separate enzyme from substrate

• higher tolerance to pH and Temp

Denaturation

The loss of tertiary structure of an enzyme causing it to no longer function

• Temp: vibration break intermolecular bonds - permanent

• pH: break hydroden bonds

Activation Energy

• the minimum energy it takes for a reaction to occur

• enzymes decrease this

Intracellular uses of enzymes:

• krebs cycle inside mitochondria

• enzymes produced by free ribosomes

Extracellular uses of enzymes:

• digestion of food in the small intestine

• enzymes from the ER released in the glands

Induced Fit Model

• The active site of an enzyme is flexible and can change shape to better hug the substrate

• substrates initially bind due to polar reactions

Competitive Inhibition

• An inhibitor binds to the active site of an enzyme to reduce or stop its function.

• Increasing substrate concentration can overcome the effects of this

Allosteric Activation

An allosteric molecule must bind to the allosteric site in order to change the shape of the active site on an enzyme, so that the substrate can fit and the reaction can occur

Lock & Key Model

The active site of an enzyme is rigid and does not change shape

Allosteric Site

Location AWAY from the active site where a substance may bond in order to effect an enzymatic reaction

Feedback Inhibition

The end product of a reaction acts as an inhibitor to the initial enzyme in the reaction

Coenzyme

Organic substance that facilitates the activity of an enzyme

Cofactor

Inorganic substance that facilitates the activity of an enzyme

Non-Competitive Inhibtion

Substance attaches to an allosteric site in order to slow or stop an enzymes function

Endothermic Reaction

Reaction in which the products have more energy than the reactants

Exothermic Reaction

Reaction in which the reactants have more energy than the product

Globuilar Proteins

Describes the tertiary shape attained by all enzyme proteins

Lock & Key vs. Induced Fit Models

Lock & Key is the idea that only the correct sized substrate (key) fits into the active site (key hole). So only the correct key(substrate) opens a certain lock (enzyme).

Induced Fit Model is the idea that the substrate plays a role in determining the final shape of the enzyme and that the enzyme is partially flexible. Only the proper substrate is capable of inducing the proper alignment of the active site.

Comparison of Lock & Key and Induced Fit Model

Both agree that only one substrate will work when it meets the active site of the enzyme.

Both require an enzyme and a substrate.

Catabolic vs. Anabolic Pathways

Catabolic reactions break down molecules and release energy by breaking down complex molecules to simpler compounds.

Anabolic reactions build larger molecules from smaller ones, they consume energy to do this.

Similarities: Both are metabolic pathways

Cofactors vs. Coenzymes

A cofactor is a non-protein chemical compound. "helper molecule".

Coenzymes are cofactors that are bound to an enzyme loosely. A coenzyme is a small, organic non-protein molecule. It carries chemical groups between enzymes.

Competitive Inhibitors (active site) vs. Non- Competitive Inhibitors (allosteric site)

Competitive:

• substrate and inhibitor chemically similar

• inhibitor can bind with the same active site and make it not free for substrate

• substrate conc can still increase rate

Non-competitive:

• substrate and inhibitor diff

• inhibitor binds to an allosteric site

• changes shape

• substrate onc cna’t speed dup rate

Both:

• enzymatic reactions that slow down the rate

• both involve reversible + irreversible inhibitors

Substrate analogue:

molecules that are able to form covalent bonds with the active site of an enzyme

How to antibiotics works?

• Bacteria cell walls made of peptidoglycans

• peptidoglycans held together by crosslinks

• when new cells grows, enzymes known as autolysins produced

• these create small strechy holes in cell wal so cross links can form

• penicillin inhibits DD transpeptidase that catalyse crosslinks formation

• no crosslink but lots of holes

• bacteria in watery env. so lysis

Activation energy

the minimum amount of energy that is needed to start a chemical reaction/ difference between the energy of the reactants and the maximum energy.

Basic Characteristics of Enzymes

Reusable and specific

Speed up chemical reactions by lowering the activation energy needed to start the reaction

When put with high temperatures it denatures

Enzymes are proteins and each has its own active site.

Enzymes are affected by the acidity or alkalinity of the solutions therefore every enzyme has a different optimum pH. At extreme pH conditions the enzyme denatures

At what temperature is enzyme activity the greatest

37 degrees Celsius

The substance with which an enzyme reacts

Substrate

Enzyme actions can be ____

Reversible

Allosteric Inhibition vs. Activation Process

In warm up

Lactase

Lactase breaks lactose (the sugar in milk) into one glucose and one galactose molecule.

Pectinase

an enzyme that breaks down pectin, a polysaccharide found in plant cell walls. Commonly referred to as pectic enzymes

Amylase

any of several digestive enzymes that break down starches

(saliva glands)

Reversible Inhibiton

inhibition of enzyme activity in which the inhibiting molecular entity can associate and dissociate from the protein's binding site.

Permanent (irreversible)

the action of an inhibitor such that, once bound to a protein, it cannot dissociate.

A new antibiotic has been developed that will use competitive inhibitor enzyme inhibition. This means that the...

Antibiotic will compete for substrate binding sites on the enzyme

Which variable has the least affect on enzyme activity?

Light intensity

Enzymes are very specific in their choices of substrates because each different enzyme has an active site that....

is shaped to fit a certain substrate molecule

The site where molecules other than the substrate bind in an enzyme to alter its activity are called....

Allosteric Site

In an enzyme catalyzed reaction the reactants are called the...

substrate...duh

When the substrate is bound to the enzyme, the shape of the enzyme may change slightly, leading to this

A better induced fit

At the conclusion of an enzyme catalyzed reaction, the enzyme...

frees itself from the product and is ready to be reused.

The ability of an enzyme to catalyze a reaction is not affected by...

excess cofactor.

The temperature is raised slightly above the optimum for a specific enzyme. What would you expect

to observe as a result of the change in temperature?

decreased enzyme activity

Allosteric inhibitor binds here; changes enzyme shape.

non-catalytic binding site