Lesson (4) Chemical reactions inside organisms' bodies

Biological chemical reactions occur inside living organisms body in order to help in growth, get energy, build tissues and sustain life. These reactions are called "Metabolism". If these reactions stop in a living organism, it will die.

Metabolism: A group of biochemical reactions which occur within living organisms in order to build complex macromolecules from simple molecules, or break up molecules to get energy.

Metabolism reactions are divided into:-

1- Anabolism

2- Catabolism

Anabolism: A process by which simple molecules are used to build complex macromolecules through a group of chemical reactions which consume energy.

 Building proteins from amino acids is an example on anabolism

Catabolism: A process by which energy is being released from the chemical bonds in some molecules such as glucose.

 Cells break up glucose to release energy from it.

 Chemical reactions generally need high activation energy to occur. To decrease the energy used by cell in biochemical reactions occurring inside it, we need catalysts to decrease activation energy needed for the reaction to occur, which speeds this reaction up. Such catalysts are called enzymes

Activation energy: The minimum energy required for a chemical reaction to occur.

(For reading only): The term activation energy was coined by Swedish scientist Arrhenius in 1889 A.D.

Enzymes: Biological catalysts formed from proteins molecules which speed up chemical reactions occurring within living organisms.

Enzymes are formed from groups of amino acids which are arranged in the form of polypeptide chains which forms the stereoisomerism of enzymes.

(For illustration) stereoisomer: Molecules that have the same no. of atoms but with different arrangements.

The properties of enzymes

1- They resemble chemical catalysts, as they only speed up the chemical reaction without taking part in it.

2- Enzymes are affected by the concentration of hydrogen ions (pH) and temperature.

3- Enzymes are different from other catalysts because every enzyme is specialized for only one reactant substance (called substrate) and a small no. of reactions.

4- Enzymes decrease the activation energy needed for chemical reactions to occur.

Substrate: The substance on which enzyme work.

Enzymes are classified according to their chemical structure into:-

1- Simple enzymes

They are enzymes which are composed of simple proteins.

Example: Amylase enzyme.

(For reading only) amylase is an enzyme secreted by salivary glands, which changes starch into sugar.

2- Complex enzymes

They are enzymes which consist of:-

1- Protein part

2- Non protein part: This part may be an atom of metal (iron, copper, magnesium) or an organic molecular called coenzyme, non protein part is the active site of enzyme molecule.

Example: Catalase enzyme

(For reading only) catalase enzymes speeds up the decomposition of hydrogen peroxide H2O2 into water and oxygen

The active site of enzyme

Every enzyme has one or more active sites

Active site: A stereoisomer which is responsible for enzyme work

1- The active site of an enzyme (E) links with the substrate (S) forming enzyme-substrate complex (ES).

2- The complex decomposes, products of reaction are formed and the enzyme gets released.

Fig. (12) The mechanism of enzyme

1- Temperature

Every enzyme has a different optimum temperature (the temperature on which the enzyme becomes most active).

 When the temp. of an enzyme increases more than its optimum temperature, its activity decreases gradually until it stops due to the change of its structure.

 When the temp. of an enzyme becomes less than its optimum temperature, its activity also decreases gradually. Enzyme activity stops at 0◦C (but it become active again when its temperature increases).

2- Power of hydrogen (pH)

It's the measurement which determines the concentration of hydrogen ions H+ in a solution, and determines if the solution is acidic, alkaline or neutral.

Solutions with pH less than 7 are acidic, while those with pH more than 7 are alkaline. Solutions with pH equals 7 are neutral.

Fig. (12) pH measurement

 Indicators of pH has standard colours to determine the acidity or basicity of a solution and gives approximated numbers, while the digital devices give more accurate numbers.

Example of pH indicators:-

1- Litmus papers

2- Methyl orange

3- Phenolphthalein

pH and the activity of enzymes

 Enzymes are affected by pH because its composed of amino acids which contain acidic carboxyl groups COOH- and basic amine groups NH2.

 Each enzyme has its own pH on which it becomes most active, this degree of pH is called "Optimum pH"

 If the pH of an enzyme decreased or increases, its activity decreases gradually till it stops.

 Most enzymes works at pH of 7.4

Examples

- Pepsin enzyme works at acidic pH (less than 7)

- Trypsin enzyme works at basic pH (more than 7)

(For reading only) pepsin enzyme is secreted by stomach to help in the digestion of proteins, whereas trypsin enzyme is secreted by pancreas and poured in small intestine to digest proteins, too.

 Scientists discovered that proteins can be used in the treatment of many diseases and disorders in human body. These biological macromolecules were produced and used to treat some diseases, they are called Biopharmaceuticals

 It's hard to send medicines to target cells in human body, scientists solved this problems by discovering methods to send these medicines to target cells by using nanomaterials, which resulted in the creation of a new science called Nanopharmaceutics and these nano biological medicines were called Nanobiopharmaceutics

Metabolism: A group of biochemical reactions which occur within living organisms in order to build complex macromolecules from simple molecules, or break up molecules to get energy.

Anabolism: A process by which simple molecules are used to build complex macromolecules through a group of chemical reactions which consume energy.

Catabolism: A process which breaks some molecules to release energy from them.

Activation energy: The minimum energy required for a chemical reaction to occur.

Enzymes: Biological catalysts formed from proteins molecules which speed up chemical reactions occurring within living organisms.

Substrate: The substance on which enzyme work.

Active site: A stereoisomer which is responsible for enzyme work.

Power of hydrogen pH: The measurement of the concentration of positive hydrogen ions in solutions to determine their acidity or basicity.

Biopharmaceuticals: They are biological macromolecules which are used to treat some diseases.

Nanopharmaceutics: The science that studies and creates methods for sending medicine right to target cells accurately by means of nanomaterials.

Nanopharmaceuticals: They are biological macromolecules which are used as medicines to treat some diseases, they are being sent to target cells by means of nanomaterials..

1- Metabolism reactions are very important to living organisms.

Because it plays an important role in building complex molecules from simple ones, and breaking some molecules to release the energy stored in them.

2- Catabolism and Anabolism reactions are essential for living cells.

Because catabolism process breaks up some molecules to release the energy stored in them, while anabolism builds up complex molecules from simple ones.

3- The biological importance of enzymes.

Because they speed up chemical reactions occurring inside living organisms without taking part in them by decreasing the activation energy needed for these reactions to occur.

4- Amylase is a simple enzyme, while Catalase is a complex one.

Amylase is a simple enzyme because it is composed of simple proteins, while Catalase is a complex enzyme because it is composed of complex proteins and non proteins parts.

5- Temperature affects enzyme activity.

Because each enzyme has a temp. on which it becomes most active "optimum temperature", when its temp. increases or decreases, its activity decreases until it stops

6- When the temp. of an enzyme increases more than its optimum temperature, its activity decreases gradually until it stops.

Due to the change of the natural structure of enzyme.

7- pH of solutions affect enzyme activity.

because its composed of amino acids which contain acidic carboxyl groups COOH- and basic amine groups NH2.

1- Choose the correct answer

1- A process by which simple molecules are used to build complex macromolecules through a group of chemical reactions which consume energy is called ………………

A- Catabolism B- Anabolism C- Oxidation D- Hydrolysis

2- A process which breaks some molecules to release energy from them is called ………

A- Oxidation B- Reduction C- Anabolism D- Catabolism

3- The substance on which enzyme work is called ……

A- Substrate B- Substance of reaction C- Reagent D- Product

4- Enzymes are made up of ………

A- Proteins B- Nucleic acids C- Carbohydrates D- Lipids

5- …………. is from simple enzymes

A- Amylase B- Catalase C- Pepsin D- Trypsine

6- ………. is from complex enzymes.

A- Trypsine B- Pepsin C- Catalase D- Amylase

2- Define:-

1- Metabolism

2- Anabolism

3- Catabolism

4- Activation energy

5- Enzymes

6- Substrate

7- Active site

8- Power of hydrogen pH

9- Biopharmaceuticals

10- Nanopharmaceutics

11- Nanopharmaceuticals

1- Choose the correct answer

1- Anabolism

2- Catabolism

3- Substrate

4- Proteins

5- Amylase

6- Catalase