Transcript Principals of General Zoology (Zoo-103)

Lecture 23: Animal physiology
Metabolism ‫األيْض‬

Metabolism: is the set of chemical reactions that occur in living
organisms to maintain life ‫ يحافظ على الحياة‬. These processes allow
organisms to grow and reproduce ‫ يتناسل‬, maintain their structures, and
respond to their environments.

Metabolism is usually divided into two categories:
a)
Catabolism; ‫ هدم‬breaks down organic matter, for example to produce energy
in cellular respiration.
b)
Anabolism; ‫ بناء‬constructing ‫تكوين‬/‫ بناء‬components of cells such as proteins and
nucleic acids.

Enzymes are important to metabolism because they act as catalysts to
allow chemical reactions to proceed quickly and efficiently.
 Key Biomolecules In Metabolism ‫الجزيئات الحيوية األساسية في األيض‬

Most of the structures that make up animals, plants and
microbes are made from three basic types of molecule:
1) proteins,
2) carbohydrates
3) and lipids (often called fats).

As these molecules are important for life, metabolism focuses
on utilizing these molecules in two ways:
a) in the construction of cells and tissues ‫تكوين الخاليا واألنسجة‬,
b) or breaking them down and using them as a source of energy ‫ كمصدر للطاقة‬.

These macromolecules are essential parts of all living
organisms.
Important biochemicals:
1- Proteins:
 Proteins are made of amino acids arranged in a linear chain and
joined together by peptide bonds.
 Many proteins are the enzymes that catalyze ‫سهـل‬
ِّ ُ ‫ ت‬the chemical
reactions in metabolism.
 Other proteins have structural ‫ تركيبية‬or mechanical ‫ميكانيكية‬
functions, such as the proteins that form the cytoskeleton.
 Proteins are also important in cell signalling ‫اإلشارات الخلوية‬, immune
responses ‫اإلستجابات المناعية‬, active transport across membranes ‫النقل‬
‫النشط خالل األغشية‬.
2- Lipids
 Lipids composed of three fatty acids and glycerol
molecule.
 They construct ‫تكون‬
ِّ part of the cell membrane.
 They are a source of energy.
 Steroids such as cholesterol are another major class of
lipids that are made in cells.
3- Carbohydrates
 Carbohydrates are straight-chain aldehydes or
ketones with many hydroxyl groups that can exist as
straight chains or rings.
 Carbohydrates are the most abundant ‫األكثر‬
‫توفرا‬biological molecules, and found as storage for
producing energy (e.g. glycogen) and structural
components (cellulose in plants, chitin in animals).
 The basic carbohydrate units are called
monosaccharides and include galactose, fructose, and
glucose.
 Monosaccharides can be linked together to form
polysaccharides.
4- Coenzymes ‫ ُم ِّعينة‬/‫إنزيمات مساعدة‬
 Metabolism involves chemical reactions, most involve metabolic
intermediates ‫ وسطاء‬called coenzymes.
 Coenzymes are therefore continuously being made ‫تتكون باستمرار‬,
consumed ‫ وتستهلك‬and then recycled ‫ ويعاد تكوينها‬.
 One central coenzyme is adenosine triphosphate (ATP), the energy
source of cells. and used to transfer chemical energy between
different chemical reactions.
 ATP acts as a bridge between catabolism and anabolism, with
catabolic reactions generating ATP and anabolic reactions consuming
it.
 It also serves as a carrier of phosphate groups in phosphorylation
‫ تفاعالت الفسفرة‬reactions.
5- Vitamines
 Vitamin is an organic compound needed in small quantities
that cannot be made in the cells.
 In human nutrition, most vitamins function as coenzymes after
modification.
 Nicotinamide adenine dinucleotide (NADH), a derivative ‫مشتق من‬
of vitamin B3 (niacin), is an important coenzyme that acts as a
hydrogen acceptor ‫مستقبل للهيدروجين‬.
 NAD+ exists in two related forms in the cell, NADH and NADPH.
 The NAD+/NADH form is more important in catabolic reactions,
while NADP+/NADPH is used in anabolic reactions.
6- Minerals & Cofactors
a)- elements
 They are inorganic elements play important roles in metabolism; (e.g.
sodium and potassium).
 About 99% of mammals' mass ‫ وزن الجسم‬are the elements carbon, nitrogen,
calcium, sodium, chlorine, potassium, hydrogen, phosphorus, oxygen
and sulfur.
 The organic compounds (proteins, lipids and carbohydrates) contain the
majority of the carbon and nitrogen and most of the oxygen and
hydrogen is present as water.
b)- ions:
 The most important inorganic ions are sodium, potassium, calcium,
magnesium, chloride, phosphate, and the organic ion bicarbonate.
 These Ions are also critical for nerves and muscles.
Catabolism ‫ & اهلدم‬Anabolism ‫البناء‬
a)- Catabolism:
 It is the metabolic processes that break down large molecules .
 The purpose ‫ الهدف‬of the catabolic reactions is to provide the
energy and components needed by cell .
 In animals these reactions involve complex organic molecules
being broken down to simpler molecules, such as carbon dioxide
and water .
b)- Anabolism:
 It is the constructive ‫ البنائية‬metabolic processes where the energy
released by catabolism is used to synthesize‫ لتكوين‬complex
molecules from small and simple components .
 Anabolism involves three basic stages .
1) the production of components such as amino acids, monosaccharides, and fatty
acids ,
2) their activation into reactive forms using energy from ATP ,
3) the assembly ‫تشكيل‬/‫ تركيب‬of these components into complex molecules such as
proteins, polysaccharides and lipids.
Metabolism ‫األيض‬
(Metabolism is the chemical reactions that
occur in living organisms to maintain their
life, to grow and to reproduce).
Catabolism ‫الهدم‬
Is the break down of large
molecules to provide energy
and components needed for
anabolic reactions .
Anabolism ‫البناء‬
Is the constructive processes that
uses energy formed by catabolism
to synthesize complex molecules
for make up cellular structures.