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A . Introduction

chemistry – science that deals with the composition of

substances and the Changes that take place in their

composition .

Organic chemistry – chemistry that deals with organic

substances (those that contain carbon and hydrogen )

Biochemistry—chemistry of living organisms ;

essential for understanding physiology because body

functions involve chemical changes that occur within

cells.

Matter – anything that has weight (or mass) and takes

up space .It can be solids, liquids , or gases .


Energy

Energy – the ability to do work . Potential energy

(PE) is stored energy in matters ; Kinetic energy

(KE) is working energy produced by the motion of

matters .

Energy occurs in 4 forms in the human body :

chemical , electrical , radiant , and mechanical

energy . chemical energy is the most important

form in terms of actually driving chemical reactions.


Models of the Atom

Figure 2.1


Atomic number

(AN) = number

of protons =

number of

electrons

Atomic weight

(AW) = number

of protons +

number of

neutrons


IONS

In addition to neutrons , the electrons of atoms tend

to change also – atoms that have either lost or

gained electrons are called ions. Atoms that have

lost electrons (as a result , now contain more p+ than

e-) are called cat ions which carry positive charges ,

while atoms that have gained excessive electrons (as

a result, now contain more e- than p+ ) are called

anions which carry negative charges .


Chemically Reactive Elements

Reactive elements

do not have their

outermost energy

level fully occupied

by electrons

Figure 2.4b


Bonding of atoms

Ionic bonding = formed by attraction of

opposite charges of a cation and an anion

(e.g. Na+ + Cl- →NaCl).


Formation of an Ionic Bond

Figure 2.5b


Covalent bonding

formed by sharing of electrons between two

atoms (e.g. Cl + Cl →Cl2) . The strongest

type of bonding .


formed by weak attraction between H+ and nitrogen (N) or oxygen

(O) (e.g. H of a water molecule attracting to O of another water

molecule). The weakest type of bonding .

Hydrogen bonding


Chemical reactions involve the formation , breaking , or

rearrangement of chemical bonds . There are 4 general types :

Dehydration synthesis : A + B → AB + water

Decomposition (or hydrolysis) : AB + water → A + B

Exchange : AB + CD → AD + CB

Reversible : A + B < - - - > AB


The rate of chemical reactions is

dependent on 4 factors :

size of reacting molecules : smaller molecules have greater

kinetic energy which produces faster reaction rate .

Temperature : higher temperature creates greater kinetic

energy and faster reaction rate .

Concentration of reactants : higher concentration produces

faster rate .

Presence of catalysts : inorganic catalysts or organic

catalysts (enzymes) increase reaction rate .


Electrolytes = compounds that release ions when

dissolved in water (e.g. NaCl + water → Na+ + Cl- )

Acids = electrolytes that release H+ (e.g. H2 CO3 → H+ +

HCO3- )

Bases = electrolytes that release anions that can combine

with H+ (e.g. NaOH → Na+ + OH- )

Salts = substances formed by the reaction between an

acid and a base (e.g. HCl + NaOH → H2O + NaCl )


PH

measurement of H+ concentration in a solution

- More H+ = lower PH = more acidic

- Less H+ = higher pH = less acidic

-Ph scale is form 0 to 14 , where the

midpoint (pH 7.0) is neutral. From pH 0

to 6.9 , it is acid ; while from pH 7.1 to

14 is base .


PH Scale

Figure 2.9


Organic substances = chemicals that

contain C and H (e.g. Carbohydrates or

Protein , Fat, and nucleic acid)

Inorganic substances = chemicals that do

not contain C and H (e.g. table salt or NaCl ,

carbon dioxides or CO2 , ammonia or NH3 )

(Most inorganic substances are small,

electrolytes and usually use ionic bonding ,

and most organic substances are large , non

electrolytes, and usually use covalent

bonding ).


An Organic Compound

(cholestrol)


Protein

Figure 2.3


Carbohydrate


Nucleic Acid


Solutions and concentration

When a substance is dissolved in a liquid (ex. water) , a solution is

formed . The substance that is dissolved is the solute and the liquid in

which the dissolution occurred is the solvent .

Concentration : The measure of dissolution of a particular solute in a

given volume of solvent . it is measured in molarity .

Molarity : The number of solute molecule per unit volume of solution .

Buffer : A substance that can react with an acid or a base and thus resist a

change in PH .


Tonicity

the ability of a solution to change the tone or shape of

cells by changing their internal H2O volume .

- Hypertonic : solutions with higher osmotic pressure.

cells in a Hypertonic solution lose H2O and shrink .

- Hypotonic : solution with a lower osmotic pressure –

cells in hyportonic solution gain H2O and swell .

- Isotonic : same tonicity . cell in isotonic solutions

neither gain , nor lose H2O .


The effect of solutions of varying tonicities on

red blood cell


1.Are always made of globular proteins .

2.Can promote the rate of chemical reactions by billions of times.

3.Can lower the activation energy – energy necessary to start a

reaction – resulting in a conservation of energy .

Enzymes


4. Are usually reusable or recycled .

5. Are always very specific – using its active site , each

enzyme is designed to bind to only one specific substance ,

the substrate and rapidly transforms the substrate into a

product .

6. Many enzymes would not achieve their optimum efficiency

unless they are bound to a cofactor (i.e. ions , metals) or to a

coenzyme (organic cofactors such as vitamins ).

7. Most enzymes' names end with "ase“(ex. Dnase, Sucrase)


Enzyme-

substrate

complex (E–S)

1

2

3

Internal rearrangements

leading to catalysis

Free enzyme (E)

Active site

Enzyme (E) Substrates (s)

Amino acids

H20

Peptide bond

Dipeptide product (P)

Mechanism of Enzyme Action

Figure 2.20


Factors that affect enzyme activity

Since all enzymes are made of globular proteins ,

and proteins are made of amino acids linked by

peptide bonds , enzymes can be affected or

denatured very easily .

Factors that could affect or denature enzymes

include heat , ration , electricity , certain chemical

substances , and extreme pH.


Synthesis and Hydrolysis of Sucrose :

METABOLISM

Anabolic metabolism

Uses dehydration synthesis reaction to build large molecules from

small molecules .

Each reaction releases a water molecule and requires energy input

Example – monosaccharide + energy → polysaccharide + water

amino acids + energy → protein + water.


Catabolic metabolism

Uses hydrolysis (or decomposition) reaction to break up large

molecules into smaller molecules .

Each reaction requires a water molecule and releases energy .

Example -- triglyceride + water → fatty acids + energy


Adenosine Triphosphate (ATP)

High- energy molecule that is derived from the nucleotide ,

adenine .

Contains 3 phosphate groups (PO4) and high-energy chemical

bonds that each time the bonds are broken , a large amount of

energy is generated .

Energy is released by ATP is broken down by hydrolysis reaction

ATP + water → ADP + PO4+ energy [ADP = adenosine

diphosphate ]

ADP + water → AMP + PO4 + energy

[AMP = adenosine monophosphate ]


ATP

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