HIGH ENERGY COMPOUNDSAND

ATP AS UNIVERSAL ENERGY CURRENCY

PRESENTED BY

SUSHMA P.R 1ST M.Sc BIOTECH,BRINDAVAN COLLEGE

PRESENTED TO

Mrs. DILSHAD BEGUM BIOCHEMISTRY,BRINDAVAN COLLEGE

Also known as Energy Rich CompoundsCompounds in biological system which on

hydrolysis yield free energy equal to or greater than that of ATP, i.e. ∆ G = -7.3 kcal / mol

Compounds that yield energy less than -7.3 kcal / mol are called Low Energy Compounds.

HIGH ENERGY COMPOUNDS

Most of the high energy compounds contain phosphate group [except acetyl CoA] hence they are also called high energy phosphates.

The bonds in the high energy compounds which yields energy upon hydrolysis are called high energy bonds.

These bonds are notated by the symbol '~‘ [squiggle].

Fritz Albert Lipmann invented this notation.

The energy that is actually available [ utilizable ] to do the work is called Free Energy.

Change in free energy is denoted by ∆G. Also known as Gibb’s Free Energy.

For endergonic reactions ∆G will be +veFor exergonic reactions ∆G will be -ve

WHAT IS FREE ENERGY ?

High energy compounds are mainly classified into 5 groups:

1. Pyrophosphates 2. Enol phosphates 3. Acyl phosphates 4. Thiol phosphates 5. Guanido phosphates or phophagens

CLASSIFICATION OF HIGH ENERGY COMPOUNDS

The energy bonds in pyrophosphates are acid anhydride bonds.

These bonds are formed by the condensation of acid groups [mainly phosphoric acid] or its derivatives.

An example for pyrophosphates is ATP. It has two high energy diphosphate bonds – phosphoanhydride bonds.

PYROPHOSPHATES

The bond present here is enolphosphate bondIt is formed when phosphate group attaches to a hydroxyl

group which is bounded to a carbon atom having double bond.

Example : phosphoenolpyruvate

ENOL PHOSPHATES

An example for acyl phosphate is 1,3- bisphosphoglycerate.

The high energy bond in this compound is formed by the reaction between carboxylic acid group and phosphate group.

ACYL PHOSPHATES

Here high energy phosphate bond is absent. Instead high energy thioester bond is present.

Thioester bond results from the reaction between thiol and carboxylic acid group’

Example : Acetyl CoA

THIOL PHOSPHATE

Also known as phophagensThe bond is known as guanidine phosphates bondsIt is formed by the attachment of phosphate group to

guanidine group.Most important compound with this bond is

phosphocreatine.

GUANIDO PHOSPHATES

Class Bond Example (s)

Pyrophosphates – C – P – P ATP, pyrophosphate

Acyl phosphates   O   1,3-bisphospo-    ║ glycerate,carbamoyl – C – O ~ P phosphate

Enol phosphates – CH   ║ – C – O ~ P PEP

TYPES OF HIGH ENERGY COMPOUNDS

Thiol esters (thioesters)  C  Acetyl CoA,   ║ Acyl CoA – C – O ~ S –

Guanido phosphates   | phosphocreatine – N~ P phosphoargenine

Compounds ∆Go (kCal/mol) Phosphoenol pyruvate - 14.8Carbamoyl phosphate - 12.3Cyclic AMP - 12.01,3 – Bisphosphoglycerate - 11.8Phosphocreatine - 10.3Acetyl phosphate - 10.3Pyrophosphate - 8.0Acetyl CoA - 7.7ATP→ADP + Pi - 7.3

HIGH ENERGY COMPONDS AND FREE ENERGY RELEASED

ATP is the most important high energy compound in the living cell.

It contains an adenine group,a ribose sugar and a triphosphate.

ATP is considered as an high energy compound because of the presence of two phospho anhydride bond.

Hydrolysis of the terminal phosphate group yields high negative free energy i.e. -7.3 cal / mol

ATP AS UNIVERSAL ENERGY CURRENCY

ATP acts as an link between catabolism [exergonic reaction] and anabolism [endergonic reaction].

Catabolic reactions can give energy in the form of ATP.

Anabolic reactions can utilize energy through hydrolysis of ATP.

It transfers phophoryl groups from high energy compounds to less energetic compounds

HYDROLYSIS OF ATP

Adenosine Pi Pi

-7.3kcal

ADP + Pi

P P P

Adenosine triphosphate (ATP)

P P P+

Adenosine diphosphate (ADP)

HYDROLYSIS

HIGH ENERGY BOND

The ATP reaction is commonly written as:

ADP + Pi + energy ATP

The forming of ADP into ATP requires energy (endothermic) – -7.3

kcal/mole

RESYNTHESIS OF ATP

P P P+

Adenosine diphosphate (ADP)

P P P

Adenosine triphosphate (ATP)

Dehydration[Remove H2O]

1. ATP – PHOSPHOCREATINE SYSTEM• ATP is resynthesised via phosphocreatine (PC)• PC is stored in muscle cell sarcoplasm

• the following reactions takes place :• PC ---> Pi + C + energy• energy + ADP + Pi ---> ATP• the two reactions together are called a coupled reaction• these reactions are facilitated by the enzyme creatine kinase

• the net effect of these two coupled reactions is :• PC + ADP ---> ATP + C

3 PATHWAYS FOR ATP RESYNTHESIS

2. THE LACTIC ACID SYSTEM

• This system is an anerobic process and takes place in the sarcoplasm

• The process involves the partial breakdown of glucose – glucose can only be fully broken down in the presence of oxygen.

Only CHO is used in this system• Total= 2 ATP but this is used for resynthesis of ADP to

ATP not muscualr work• the end product of this reaction (in the absence of

oxygen) is lactic acid• the enzyme facilitating the conversion from pyruvic

acid to lactic acid is lactate dehydrogenase (LDH)

THE AEROBIC SYSTEMSTAGE ONE – GLYCOLYSIS – 2ATPthis takes place in CYTOPLASMand is identical to the lactic acid systemATP regenerated = 2ATP per molecule of glucose

STAGE TWO - KREB’S CYCLE (CITRIC ACID CYCLE) - 2 ATP

occurs in the presence of oxygentaking place in the muscle cell MITOCHONDRIA within the inner

fluid filled matrixpyruvic acid (from glycolysis) promoted by enzymes of the citric

acid cycle, or fatty acids (from body fat) facilitated by the enzyme lipoprotein lipase or protein (keto acids - from muscle) act as the fuel for this stage

STAGE THREE - ELECTRON TRANSPORT CHAIN – 34 ATP

occurs in the presence of oxygenwithin the cristae of the muscle cell MITOCHONDRIAhydrogen ions and electrons have potential energy which

is released to produce the ATP

The exergonic hydrolysis of ATP is coupled with the endergonic dehydration process by transferring a phosphate group to another molecule.

For example :

ATP + H2O ADP +Pi

glucose + Pi glucose-6-phosphate + H2O

Overall reaction: glucose+ATP glucose-6-phosphate+ADP

COUPLED REACTION - ATP

ATP AS A LINK BETWEEN CATABOLIC AND ANABOLIC PATHWAYS

Metabolism Synthesis e.g. * Polysaccharides * Amino acids * DNA/RNA

Movement Muscle contraction Energy to allow muscle filaments to slide

FUNCTIONS OF ATP

Active Transport

Changes the shape of carrier proteins

Secretion

In the formation of the lysosomes necessary for exocytosis

Chemical Reactions

A phosphate molecule from ATP can be transferred to . another molecule

Makes it more reactive Lowers activation energy

WHY ATP IS CONSIDERED AS UNIVERSAL ENERGY CURRENCY?

Common intermediate in many reactions

Links energy requiring and energy producing reactions

• It is universal with all living things

IN SUMMARY

Easily participates in many reactions

Drives most biological processes

One molecule can be synthesised and perform a large number of jobs

THANK YOU