Study Unit 3 Flashcards by Lara Olivier

Fermentation

Reactions wherein a raw organic feed is converted into a product by the action of microbes or by the action of enzymes

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Three classes of biological processes

Fermentation
Elementary physiological processes
Actions of living entities

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Groups of fermentation

Catalysed by enzymes

- Catalysed by microorganisms

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What is the difference between enzymatic and microbial fermentation?

Enzymatic fermentation
- Organic feed is converted into a product but no enzyme is produced

Microbial fermentation
- Organic feed is converted to a product but cells are reproduced during fermentation

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What is an enzyme?

A protein with a high molecular weight that acts as a catalyst

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What does it mean when we say that enzymes are substrate specific?

Every enzyme is specific for a certain substance (substrate)

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How are enzymes named?

Reference to reaction or substrate + “-ase”

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What is a holo-enzyme?

An active complex enzyme consisting of an apoenzyme with a coenzyme attached to it

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What is the apoenzyme?

The protein component of an enzyme

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What is the coenzyme?

The non-protonatious organic substance that usually contains a vitamin or mineral

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What is a cofactor?

A metical ion that needs to be associated with an enzyme for the the enzyme to function

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What are iso-enzymes?

Enzymes that differ in form but that catalyze the same reaction

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What happens during enzymatic fermentation?

The substrate binds to a very specific active site on the enzyme. When bonded the enzyme-substrate complex is formed and the reaction can take place. The products of the reaction then leave the active site, leaving it available for another substrate molecule.

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What is the proximity effect that takes place during enzymatic fermentation?

The proximity effect increases the rate of the reaction as the active sites of the substrate and the enzyme are aligned and held close together (has the same effect as the increase in concentration of the reagents of the reaction)

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What is the orientation effect that takes place during enzymatic fermentation?

3D structure of the enzyme is changed to increase the reaction rate

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How is enzyme concentration measured?

In units.
1 U = 1 micromole/min at a certain T and pH with a substrate concentration much greater than Km (Michaelis-Mentin constant)

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What is a unit?

A unit has to do with the amount of catalytic activity under certain conditions

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What is the specific activity?

Units/proteins

micromole/min.mg

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What is Michaelis and Menten’s 2-step proposed mechanism for enzymatic fermentation?

E + S = ES

ES = E + P

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Why can it not be said that the MM constant refers to the affinity of the enzyme for the substrate?

MM constant relates to the various rate constants. Temp and pH influence the rate constants thus these factors influence the MM constant

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Why is Km intrinsic (essential) and Vm not?

Km is a CONSTANT for a given substrate acting on a GIVEN ENZYME.
Vmax is directly proportional to the enzyme concentration as k2 (k3) is a constant for the specific given enzyme.

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3 main types of reactors

Batch reactors
Plug flow reactors (PFR)
Continuous-stirred tank reactor (CSTR) or Mixed flow reactor (MFR)

What is cooperative binding?

Some enzymes have more than one active substrate binding site. As soon one substrate binds to the enzyme it becomes possible for the other substrate to bind to the enzyme.

What does an inhibitor do?

They bind to enzymes and reduce their activity which inhibits the enzyme substrate reaction

Name the types of inhibitors

Irreversible - heavy metals Reversible - competitive, noncompetitive, uncompetitive Substrates - elevated substrate levels can also cause inhibition

How do irreversible inhibitors work?

They form stable complexes that are difficult to reactivate

What are the three types of reversible inhibitors?

Competitive Non-competitive Uncompetitive

How does competitive inhibition work?

Substrates A and B compete for the same active site of the enzyme. - A + E < - > X(SE) -> R(product) + E - B + E < - > Y [E0] = [E] + [X] + [Y]

N = ...

N = k4/k5

The higher value the value of N during competitive inhibition ...

... the lower the reaction rate.

The higher the concentration of the inhibitor B ...

... the lower the reaction rate.

How can competitive inhibition be overcome?

Increase the substrate concentration will overcome inhibition and increase the reaction rate

In Batch reactors/PFRs/CSTR what happens to k3 during competitive inhibition?

k3 remains constant

In Batch reactors/PFRs/CSTR what happens to Km(1+NCbo) during competitive inhibition?

Increases (thus the equation increases by factors)

What happens during non-competitive inhibition?

``` B binds to a different active site than A but as soon as B binds to the enzyme, A cannot disassociate to form the product (like a lock preventing product formation) A + E < - > X -> R + E B + E < - > Y B + X < - > Z [E0] = [E] + [X] + [Y] + [Z] ```

The higher the value of L during non competitive inhibition ...

... the lower the reaction rate.

The higher the concentration of the inhibitor B ...

... the lower the reaction rate.

How can non-competitive inhibition be overcome?

Add reagents that prevent B from binding to the enzyme. Increasing [S] will not work.

How do you identify non-competitive inhibition in a graph?

Non-competitive inhibition is identified by a decrease in the gradient (slope). Cm remains constant.

How does uncompetitive inhibition work?

An inhibitor binds only to the complex formed between the enzyme and the substrate A + E < - > X -> R + E B + X < - > Y Y cannot form any products. Production rate reduces

How does a high substrate concentration lead to inhibition?

A + E < - > X -> R + E | A + X < - > Y

Why does a change in pH influence an enzyme's activity?

Enzymes have ionic groups on active sites. The change in pH leads to a change in the ionic form of the enzyme and may also change its 3D structure.

What is the effect of an increase in the temperature on enzyme activity?

The reaction rate will initially increase (temp. activation). Beyond the critical point enzymes start to denaturate and activity will decrease.

At what temp do most animal enzymes denaturate?

Above forty degrees celsius

Application of pectinesterase

Maintains fruit's shape and texture

Application of pectinase

Used to clarify juice and helps to speed up the peeling process of fruits

Application of chymosin

Replacement for rennet, used to bind milk protein in the production of cheese

Application of amylase

Liquefies starch during the manufacturing of beer and wine | Treatments of textiles before it is colored

Application of cellulase

Breaks down cellulose into glucose, cellobiose and longer glucose polymers

Application of protease

Breaks down protein to obtain DNA from plant and animal cells

Application of lactase

Production of reduced lactose milk

Application of catalase

Removal of hydrogen peroxyde

Application of invertase

Chocolates with soft liquid filling