2.0 - biological reaction

7/30/2019 2.0 - Biological Reaction

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Introduction• Biochemical reactions are characterized by the use of

enzymes or whole cells (micro-organisms) to carry outspecific conversions

• Example:• Fermentation of fruit juices to make alcohol

• Subsequent oxidation to vinegar

• Living organisms are capable of carrying out a wide

range of transformations which can often bemanipulated by controlling their environment or by changing genetic constitution. The primary interest of organism is to replicate themselves



Introduction Major areas of biological sciences that are

significance to the process engineer.



Introduction Applications of biological processes will considering

systematics, genetics, biochemistry and physiology.

Outline of a biological process:



Introduction• Important aspects to reactors:

• Nature and processing of raw materials

• Choice and manipulation of the catalysts

• Control of reaction process from which the productmust be recovered.

• Bioprocesses are autocatalytic reactions. Cells is agroup of proteins that have catalytic properties

(Enzymes).• Enzymes, similar to inorganic catalyst in some ways

and very powerful catalysts that capable to enhancethe overall rate of reactions.



Introduction Enzymes are water-soluble but are frequently bound to

membranes within the cells or retained in the microbeby the cell walls.

Enzymes usually retain their catalytic activity whenisolated from the cell.

Bioreactors as an alternatives to conventional chemical

reactors, e.g in pharmaceutical industry, micro-organism & enzymes can be used to produce specificstreo-isomers selectivity.



Bioreactors Advantages

high selectivity

Feasible for multistage separation in purification

Reduced potential pollution

Increased energy recovery and reduced greenhouseemissions

Lower long-term maintenance cost

Disadvantages

Product may formed in dilute aqueous solution

Low rates

Rheological properties that difficult to handle

Low interfacial tensions – difficulties in physical

separation of product



Biological vs Chemical Reaction



Biological Products



Cells• Each components are divided

by bilayer phospholipids

membranes.

•Transportation of reactants &

products to & from cells

produces concentration

gradients because of transport

resistances within & without thecell.



Cells as Reactors Organism must grow & reproduce itself using resources

from the surrounding environment.

Living systems capture & utilize energy from the

environment to produce highly ordered structures to giverise to autocatalytic processes.

This allows the natural optimization of living processes forthe evolution of new biological information structures and

new life forms. The complexity of the bacterial cell is thus a match for any

chemical plant in the power and sophistication of itschemistry.



Cells as Reactors The basic of life lies in chemistry creates a variety of

novel solutions to a set of problem associated with life.These includes: The acquisition of food

–provide energy and nutrients that

make up the structure of the cell

Conversion of the food into the structure of the livingsystem

Retention of information–

chemical structures may bereproduced when required

Introduction of variation in the biological information - toencourage the adaptation of the organisms to theenvironment



Composition of Cells

6 major

elements,make up 90%

of weight



Composition of Cells Most of the elemental composition of cells is found in

proteins, nucleic acid and lipids.

Water is the major component of cells with 80–

90% of the total weight

Most of the protein present in the form of enzymes.

Nucleic acid are found in various forms of Ribonucleic

Acid (RNA) and Deoxyribonucleic Acid (DNA) Polysaccharides and lipids are associated with wall &

membrane structures & also act as energy-storagematerials within the cell.



Composition of Cells



Proteins Nucleic acid in the form of DNA forms the stored

structural and regulatory material for organism.

Protein is formed mainly of polymerised amino-acids.The primary structure is non-repetitive & require achemical template stored in DNA molecule for itsproduction.

Proteins have catalytic activity (enzymes) whilst otherproteins have roles in storage, trasportation,antibodies, chemical messengers (hormones) & instructure.



Nucleic Acid Nucleotides are the basic monomers of nucleic acid. It

is made from heterocyclic nitrogen compounds,purines & pyrimidines.

Types of nucleic acid:

Ribonucleic acid (RNA) – contain ribose with bases of cytosine, adenine, guanine and a unique base uracil.

Deoxyribonucleic acid (DNA)–

contain deoxyribone with bases of cytosine, adenine, guanine and a uniquebase thymidine.

The differences in the base structure affect the

secondary structures of these polymers.



RNA & DNA



Lipids & Membranes Lipids – major components of membrane.

Complex structure of fatty acids esterified withalcohols to form glycerides

Sterols is also important lipid components

Hydophobic structure – provide entry & exit portsfrom the interior of cell



Carbohydrates Major structural components of the cell walls.

Cellulose is the most commom form.

Others–

hemicellulose (hexose & pentose), pectinsand chitin.

Also act as energy storage materials in living systems.

Glycogen & starch are the major carbohydrate stores in

animals & plants, respectively.



Cell walls Derived from carbohydrates and polymeric materials.

Provide the cell with mechanical strength, providerigid structure againts which the membrane located.

The variable structure will change according toenvironment and surface properties are determinedby the cell wall materials.

The wall is negatively charges & can act as an ionexchanger.



Bio-energy & Metabolic

Pathways Biological combustion

Oxygen transport

Photosynthesis Genetic code



Rates & Kinetics of Biological

Processes

P n AnS n A P A s

A biological species i.e organism or cells

Ssubstrate or food supply

Pmetabolic product

n A >1 organism growth (reproduction)

n A =1 metabolism



Kinetics of Reproduction

P AS A 2 S AC kC r

If excess nutrientSOS

C C

SO AC kC r



In batch reactor SO A

A

C kC dt

dC

t kC

Ao A

so

eC C

exponential growth

Natural for any living system to reproduce

Desired exponential growth??

Undesired exponential growth???



If growth is limited by food supply, S and A can be

related by

S

S SO

A

Ao A

n

C C

n

C C

1



Model for steady state population; birth and

death

A B BC k r

SO BkC k

2

A

C k r D D

What is the reaction rate model for population which includes birth and

death?



Metabolism A is not reproducing, therefore n A =1

P AS A S A

C kC r

P S

CA is constant, AO AC C



In batch reactor, S Ao

S C kC

dt

dC

t kC

SoS

Ao

eC C

P S SOC C C Material balance

)1(t kC

So P

AoeC C



Enzyme Kinetics Kinetics is the study of the rated of chemical reactions.

The rates of biological reactions are greatly increasedby enzyme catalysts.

Enzyme kinetics is based upon the elementary kinetics.

2.0 - biological reaction

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