By Dr. Elrasheed Eltaher Osman

Biochemistry

Definition

Is the science concerned with various biomolecules that occur in the living cell and organism and their chemical reactions

Components of biochemistry :

1- cell biology

2- molecular biology

3- molecular genetics

Aims of biochemistry

1- is to describe and explain in molecular terms all chemical processes of living cell

2- To understand how life is began

3- knowledge of biochemistry is essential to all life sciences

Bio-medicine relationship

All diseases have biomedical bases

Most of biomedical reaction has been discovered after following a course of a disease

Biomedical techniques used for diagnosis of diseases

Biochemistry used for formulation of drugs

In order to study biochemistry a little information should be known about the cell

The cell smallest unit of live capable of doing all living processes

Cell divided into :

1- eukaryotic cell2- prokaryotic cell

Biomolecules

Complex molecules that is formed living organisms they include:

1- carbohydrates

2- protein

3- lipids4- nucleic acids

5- minerals6- vitamins

7- water

All are composed of atoms

All except minerals contain elements of water

All except minerals and water are organic molecules

All except minerals ,water and vitamins yield energy

• WATER IS BLESS FROM GOD ~ USE IT DON’T ABUSE IT

Homeostasis

Is the maintenance of composition of the internal environment for good health and this include:

1- water distribution

2- pH

3- electrolytes concentration

WATER , pH and BUFFERS

Water

Is the principle end product of oxidative catabolism of food Is the most important molecule for life

No life without water

All elements and processes in some how needs water

Water distribution

This depends on

Control of thirst by hypothalamus

Anti-diuretic hormone

Retention or excretion of water by

-Kidney (micturition)- skin (perispiration)-Lung (respiration)

Water disbalance occurs when there is state of water depletion or excess

Water depletion (dehydration)Result from

1- decrease intake (comma)

2- increase loss (severe sweating, renal loss, diarrhea cholera …

Water excess

May be due to:

Increase intake (excessive I/V fluids)

Decrease output (renal failure)

WHAT MAKES WATER AN IDEAL SOLVENT FOR THE LIFE ?

This is due to its ideal properties

Physical properties of water

1- high heat of vaporization

2- high melting

3- low freezing point

4- neutral pH

solvent Melting point

Boiling

point

Heat of vaporizatio

n

1 water 0 100 22602 methanol -98 65 11003 ethanol -117 78 8544 acetone -95 56 5235 benzene 6 80 3946 chloroform -63 61 2477 Hexane -98 69 423

1- tetrahedral

Chemical properties of water

2- bipolar

3- formation of hydrogen bonds

4- Partial dissociation

5- React as acid or base

6- high ionic product

pH

Is –log [H+]

Normal pH 7.35 – 7.45

pH scale 1—147 neutral

Potential hydrogenHydrogen ion concentration

• pH < 7 acidic • In blood pH<7.35

acidosis• Acidosis can be 1- metabolic 2- respiratory

• pH > 7 alkaline• In blood pH>7.45

alkalosis• Alkalosis can be 1- metabolic 2- respiratory

Molecules that resist change in pH when acid or alkaline are added to a solution

Buffers

They are week acids and their conjugated base

Normal occurring buffers inside human body include:

1- carbonic acid and bicarbonate

2- organic phosphoric acid and phosphate

3- proteins

Week acid

HX H++X-

Conjugate base

AX A++X-

If we add acid (H+)

HX H++X-

H+ H+ H+

AX A+ + X-

Not like this

Wake up

Forces stabilizing bimolecules

These Include:

1- covalent bonds

2- non- covalent bonds

Covalent bonds

Strong bonds

Needs high energy to be broken

Examples are

Peptide bondsGlycosidic bondsEster bondsDisulfide bridge

Peptide bonds

Covalent bond

Form between amino group of one molecule and carboxyl group on another molecule

Glycosidic bond

Covalent bond

Form between two different alcohol groups Can be

1- N-glycosidic

2- O-glycosidic

3- S-glycosidic

O-glycosidic bond

Occur when the two alcoholic groups are OH-

-CH2OH + OHCH2-

-CH2-O-CH2- H2O

N-glycosidic bond

Occur when one of the alcohol group is NH3

-CH2NH2 + OHCH2-

-CH2-N-CH2- H2O IH

S-glycosidic

Occur when one of the alcohol group is SH

-CH2SH + OHCH2-

-CH2-S-CH2- H2O

Ester bond

Occur between alcohol group and carboxyl groupPhosphoesterThioester

-COH +H OOC-

H2O

-C-O-C-

O II

Disulfide bridge

Occur between two SH group

-SH + HS-

―S―S―

2H+

The non-covalent bonds

This include

1- hydrogen bond2- hydrophobic interaction

3- Electrostatic bond

4- Van Der Waal forces

Hydrogen bond

Non-covalent bond

Occur between positive hydrogen ion in a molecule ad negative ion in another one

Is very week bond

The hydrophobic interaction

Is tendency of a molecule for folding around it self to hide the non-polar part from water when put in solution

In this case the polar part come to the out side to contact water

Electrostatic interaction (ionic bridge,salt bridge)

Non-covalent bond

Occur between a positive ion in one molecule and most negative ion in another molecule

Van Der Waal forces

Is the attractive and repulsive forces that occur between two adjacent atoms in a molecule