metabolismbiyokimya.vet/documents/biyokimya/metabolism.pdfacids by lipase are some examples of...

METABOLISM-Introduction-

Serkan SAYINER, DVM PhD. Assist. Prof.Near East University, Faculty of Veterinary Medicine, Department of Biochemistry

[email protected]

http://www.biyokimya.vet/


https://neu.edu.tr/academic/faculties/faculty-of-veterinary-medicine/


mailto:[email protected]

Overview

Living organisms need the chemicals to renew themselves and to develop and reproduce. This is because, all organisms are formed from the chemical substances.

These chemical substances can be organic such as carbohydrates, lipids protein, or can be water and inorganic elements such as Ca,P, Fe, S. For example, skin is formed from water, proteins, lipids and inorganic materials, beside this cell membranes are formed from lipids and proteins.

The molecules that make up the organism either participate in the structure of the organism or participate in the functions that provide the formation and continuity of the structure.

Once ingested and absorbed molecules enter the cell, they participate in various biochemical reactions.





METABOLISM: It is the chemical reactions that occur within the

tissues and cells of a living organism and enables the production and

continuity of living matter.

ANABOLISM: To synthesize the compounds of structural or functional

molecules from matters taken from food or inside the organism. It is

also called the orientation of the constructions of metabolic

reactions.

CATABOLISM: Fragmentation of molecules synthesized by the

organism or cells imported into the cell, therefore the it can also

called degradation of the metabolic processess.

Anabolism + Catabolism = METABOLISM

Definitions





Exergonic Reactions: Some of the reactions occurring in the

body are energizing. This reactions are called exergonic

reactions.

Endergonic Reactions: Some of the reactions occurring in

the body are energy receiving. This reactions are called

endorgonic reactions.

Intermediate metabolism: The metabolic processes within

cells and tissues in the organism referred to by the term

intermediary metabolism. In other words, the set of reactions

within the cells is called intermediate metabolism.

Definitions





Foodstuffs entering the body express changes only after

they are absorbed in the digestive tract.

The anabolic and catabolic reactions in the intermediate

metabolism develop in steps, that is, the formation of a

number of intermediates.

In other words, the reaction takes place in the form of the

initial substance reaching the final product through

intermediates. Intermediate metabolic substances in this

type of reactions are called metabolites.

Definitions





Precursor

Intermediate

MetaboliteIntermediate

Metabolite

Intermediate

Metabolite

End-

Product

Metabolites

(Intermediate metabolik substances)







There is a wide variety of metabolic reactions in the

organism that occurs. It is possible to collect them

under 3 groups.

• Hydrolysis and Condensation

• Phosphate transport

• Biological oxidations

Reactions of Metabolism





CONDENSATION• A reaction in which two or more

molecules combine to form a larger

molecule, with the simultaneous loss of a

small molecule such as water

• Glycoside bond (between two

monosaccharide molecules in

combination with an ether linkage),

Peptide bond (between two amino

acids), ester bond (between glycerol and

fatty acids) are some examples.

• Condensation is an endergonic reaction

that energy is used.






HYDROLYSIS• It is a reaction involving the breaking of a bond in a molecule using

water. The reaction mainly occurs between an ion and water molecules and often changes the pH of a solution.

• Polysaccharides with amylase, degradation of proteins with pepsin in the gastrointestinal tract, the cleavage of triglycerides to glycerol and fatty acids by lipase are some examples of hydrolysis events occurring in the body.

• They are exergonic reactions that release energy. 1-4 kcal of energy per molecule released.

• Hydrolysis events that take place under digestive enzymes in the organism and the body's temperature, can be formed by boiling with concentrated acid and alkaline in vitro.






Sucrase







PHOSPHATE TRANSPORT• In organism, many molecules, especially carbohydrates, need

to be phosphorylated, i.e. phosphate esters, to be able to

enter into the reactions.

• In this task, phosphate carriers are loaded and phosphate

residues are given to the required molecules.

• Phosphate carriers are classified in 2 groups according to the

number of phosphate residues they contain.

1. One phosphate residue carriers

2. Multiple phosphate residues carriers






1. One phosphate residue carriers• Molecules that carry enol, carboxyl, hydroxyl or an amino group

change its H atom with a phosphate residue (H2PO3-).

2. Multiple phosphate residues carriers• Examples of this group may be adenosine diphosphate (ADP)

and adenosine triphosphate (ATP). These materials can be

formed by replacing 1 hydrogen from an alcohol group of a

pentose nucleotide and receiving 2 or 3 phosphate residue.






PHOSPHATE BONDS AND ENERGY

• Some molecules carrying a phosphate residue have weak

phosphate bonds and some have resistant bonds.

• Resistant phosphate bonds have weaker energy.

• Most of them are phosphate esters and it is possible to break

down with phosphatase enzymes in the organism and with

aqueous acids and alkalis in vitro.

• Degradation of Glucose-6-phosphate (G-6-P) to phosphate and

glucose releases low energy (3.3 kcal.






• Weak phosphate bonds are bonds that break down and give

high energy.

• Acyl sulfates, enol phosphates, adenosine triphosphate

molecule are carrying this kind of phosphate bonds.

• They are destroyed with special phosphatase enzymes in

biological reactions, 7-13 kcal of energy is released. Thats

why these phosphate compounds are also called high-energy

phosphate compounds.

• For example, a phosphate and the ADP revealed with the

degradation of the ATP and the 7 kcal energy occurs.






Phosphate inculing

moleculesBond type Reaction Kcal

Glucose-6-phosphate Ester G-6-P Gli + P - 3,3

ATP Phosphoanhydride ATP ADP + P - 7,0

ATP Phosphoanhydride ATP AMP + P + P - 8,6

Phosphoenolpyruvate Enolphosphate PEP Pyruvate + P - 13,0

Creatin phospahte Phosphamide Creatin-P Creatin +P - 10,2

Phosphate Bonds And Energy





All high-energy phosphate compounds serve as the phosphate

donor.

The hydrolysis of such phosphate compounds leads to energy

output. Among these, however, ATP, in particular, provides both

the necessary phosphate and energy for the destruction of

another molecule.

Phosphate and energy transport in the organism is under the

control of phosphokinase enzymes.






BIOLOGICAL OXIDATIONS (Oxidation and reduction events)

• Transition of electrons from one atom or molecule to another

referred to as redox reaction (Redox: e- transfer).

• OXIDATION: It is the loss of electrons or an increase in

oxidation state by a molecule, atom, or ion.

• REDUCTION: It is the gain of electrons or a decrease in oxidation

state by a molecule, atom, or ion.

• Hydrogen ions are also seperated from the organic molecule with

the electrons. Thats why the simplest type of an oxidation is called

dehydrogenation.

• In organism, enzymes are also oxidized or reduced.







A

(reducing)

B

(oxidizing)

B

(Reduced)

A

(oxidized)

e-

e-

e-

e-





The most important electron donors in the

organism are hydrogen atoms of organic molecules

(e.g. glucose, fatty acids).

The hydrogen atom consists of an H+ and an e-.

The most important electron receivers are the

oxygen molecule of air (O2).

Mechanism of Biological Oxidations





Biological oxidizations are the transport of H ions and electrons

in these organic materials to oxygen. The reactions are formed

in steps rather than in a single reaction. In these steps, H ions

and electrons in organic materials are transported by oxidation-

reduction enzymes (redox enzymes).

Reducing equivalent refers to any of a number of chemical

species which transfer the equivalent of one electron in redox

reactions. Redox enzymes are essential for this transfer. They

are transported either directly or indirectly to the oxygen.






Direct biologic oxidations in body occur in very small

amounts. The enzymes involved in this case are

Oxidase.

Indirect biologic oxidations in body occurs in great

amounts. dehydrogenases.






Indirect Biologic Oxidations • In this type of biological oxidation, H ions and electrons are

taken from the organic molecules through enzymes and

transported as a series of enzymes as oxygen.

• In this case, dehydrogenases are called respiratory enzymes.

The active moieties (i.e. the moieties carrying hydrogen and

electrons from organic molecules) carrying the reduction

residues of these enzymes are the coenzymes and the

coenzymes are grouped into four groups according to their

active groups.






1. PYRIDINE NUCLEOTIDE ENZYMES• The effective group is nicotinic acid amide. The full name of

the coenzyme is nicotinamide adenine dinucleotide (NAD). There are 2 phosphoric acids in the structure. In the third entry, NADP+ (nicotinamide adenine dinucleotidephosphate) occurs.

• NAD and NADP+ are reduced by receiving electrons and H ions, becoming NADH+H+ and NADPH.

• Enzymes with coenzyme NAD are particularly involved in carbohydrate metabolism, metabolic pathways such as glycolysis and TCA cycle, and in the mitochondrial respiratory chain.






2. FLAVIN CONTAINING ENZYMES • The effective group is riboflavin (Vitamin B2), its dimethyl-

isoalloxazine group. The full name is flavin adenine

dinucleotide (FAD).

• Reduced state is FADH2. FAD is tightly bound to a specific

apoenzymes.

• In the respiratory chain, the electrons and hydrogen taken

from pyridine enzymes and organic substances are

transferred to the quinone enzymes (Q) by FAD.






3. ENZYMES WITH QUINONE (COENZYME Q10)• Effective group is quinone. It carries 10 isoprene as a

side chain. It is reduced to hydroquinone after

gaining 2H+ and 2e-.

• There is a close relationship with cytochromes

involved in the biological oxidation chain. 2H+ and 2e-

from Flavin containing enzymes causes reduction of

its and these are given to cytochromes (iron

containing enzymes).






4.ENZYMES CONTAINING IRON• Active group is iron (Fe). It is located in porphine

skeleton. Thereby forming a coenzyme.

• These coenzymes, which are found in porphyrin

structures, bind very tightly to various specific

proteins, bringing up various ferric enzymes. These

enzymes are mainly cytochromes and cytochrome

oxidases.






• This coenzyme function is based on the fact that

only the electrons exchange and give rise to

changes in the iron valence.

• Trivalent iron is reduced to divalent iron. There

are three types of cytochromes; b1, c1 and c

cytochromes.

• They transfer the electrons they receive from

Koenzim Q to one another.






The electron donor is oxidized

and acceptor is reduced. Reduced

cytochrome c gives its electrons

to cytochrome oxidases and is

self-oxidized again.

There are two types of

cytochrome oxidases; Cytochrome

a and cytochrome a3.


Cytochrome c





Cytochrome oxidase a3 takes electrons from the

cytochrome c and reduced.

Reduced cytochrome oxidase a3 gives electrons to O2

and turns it to oxygen ions.

The oxygen ion also reacts with the two hydrogen atoms

in the environment, so that water is synthesized.

The synthesis of endogenous water in the organism

occurs in this way.






Much of the biological oxidation occurs when multiple oxidation-

reduction events complement each other and are arranged as

rings of a chain.

At the end of this chain, there is an oxidized substance formed

by the direct effect of a special dehydrogenase enzyme by

activating the hydrogen from the organic substances and a

molecular oxygen at the other end.

Between the two ends a special alignment of hydrogen and

electron acceptor and carrier enzymes is observed. This is called

the electron transport chain or the respiratory chain. This

chain can start from the NAD as well as from the FAD.

The function of the Respiratory Chain





Video Source: Youtube







https://www.youtube.com/watch?v=xbJ0nbzt5Kw

Overall energy is revealed at the end of oxidation. The chemical

entering the reaction goes down to a level lower than the high

energy level in the system. The same phenomenon is seen in the

respiratory chain. During the 2 H + and 2 e-transport, there is

sufficient energy production to form a high-energy bond.

The energy released is moved adenosine diphosphate 'e (ADP)

with an inorganic phosphate. ADP uses the energy and phosphate

linking constitute high energy adenosine triphosphate (ATP).

The amount of energy and production place in the respiratory chain





If chain starts from a dehydrogenase with

NAD and is oxidased, 3 mol ATP is

synthesized.

If chain starts from a dehydrogenase with

FAD and is oxidased, 2 mol ATP is

synthesized.

The amount of energy and formation place in the respiratory chain





One of the events that continue to occur in organism is

biological oxidations.

These events provide the necessary energy for

endergonic chemical reactions occurring in the body, as

well as the emergence of many new substances

necessary for the body during oxidation and degradation

of a substance.

Importance of Biological Oxidation





700 kcal for 1 mole of glucose in biological oxidation

occurs. 1 mol ATP stores 7-8 kcal.

The energy stored in the form of ATP,• Is used in the formation and maintenance of body

temperature.

• Provides to maintain peptide bonds, glycoside bond and many

reaction events.

• Is used to maintain active contraction of the muscles and cell

membrane permeability (active transport) and secretion

events.

Importance of Biological Oxidation





A metabolic pathway is a linked series of chemical

reactions occurring within a cell.

Some metabolic pathways flow in a 'cycle' wherein each

component of the cycle is a substrate for the

subsequent reaction in the cycle. The sequence of chain

reactions starting from a basic substance and returning

to that basic substance at the end of ongoing reactions

is called the metabolic cycle or reaction cycle.• For example: TCA cycle or Krebs Cycle

The reaction cycles of metabolism





TCA Cycleor

Krebs Cycleor

Citric acid cycle







Nucleus• Transfer and replication of hereditary molecules (DNA and

RNA), hydrolysis and synthesis of nucleic acids, proteins

(transcription).

Mitocondria• Biological oxidations, TCA cycle, ATP synthesis.

Ribosomes• Protein biosynthesis (translation).

Locations of Metabolic Reactions in the Cell





Endoplasmic Reticulums• Folding and transport proteins.

Lysosomes• Hydrolysis of nucleic acids and proteins proteinase. It contains

many proteolytic enzymes such as RNase, phosphatases,

glycosidases.

Cytoplasm• Glycolysis, destruction of proteins, destruction of fat, glycogen

breakdown, biosynthesis of fatty acids.

Locations of Metabolic Reactions in the Cell





Question 1

Answer: a

........... İs a reaction in which two or more molecules combine to form a larger molecule, with the simultaneous loss of a small molecule such as water.

a. Condensation

b. Hydrolysis

c. Oxidation

d. Dehydrogenation

e. Reduction





Question 2

Answer: d

Which of the following molecules carry multiple

phosphate residue?

a. PEP

b. G-6-P

c. Creatin Phosphate

d. ATP

e. AMP





Question 3

Answer: c

Which of the following is not a coenzyme of respiratory

chain?

a. NAD

b. FAD

c. Phosphofructokinase

d. Cytocrom a

e. Q10





Any Questions?





Ası T. 1999. Tablolarla Biyokimya II. Nobel Tıp Kitapları Dağıtımı

Sözbilir Bayşu N, Bayşu N. 2008. Biyokimya. Güneş Kitabevi

References





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Metabolism





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