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Chemistry is the study of the structure and chemical properties of any substance, while
Biochemistry is the science concerned with the various molecules that occur in living cells and organisms and their chemical reactions.
The main components of living organism are
Carbohydrates and their derivatives.
Protein and amino acids .
Lipids and their derivatives .
Biochemical importance of carbohydrates
Carbohydrates are the first and most efficient source of energy for vital processes.
Carbohydrate foods contain some water soluble vitamins and minerals.
Also their content of cellulose is important in foods to prevent constipation because it acts as a roughage i.e. it increases the bulk of stool .
Biochemical importance of proteins
Proteins are necessary for health , growth and replacement of tissues which normally undergo destruction and resynthesis .
Proteins provide the body with the essential amino acids that can not be formed inside the body .
Proteins are the major source for nitrogen, sulphur and phosphorus for the body.
Protein foods are also rich in some members of water soluble vitamins.
Biochemical importance of fats
Fats are the richest source of energy, also they are the most rich energy stores.
Fats provide the body with the essential fatty acids
Fats provide the body with a group of vitamins called “The fat soluble vitamins”.
Biochemical importance of inorganic constituents
The human body requires about eight principal mineral elements which include: calcium, phosphorus , magnesium , sodium , potassium , sulphur , iron and chlorine . These are called bulk or main elements . Certain other elements including: copper , zinc , cobalt , selenium , manganese and iodine are needed in micro amounts and are called “ trace elements ”.
The importance of the inorganic constituents are
Formation of certain tissues for example calcium and phosphorous for formation bones.
clotting of blood needs calcium ions.
Formation of hydrochloric acid ( HCl ) in the stomach , through a process needs sodium chloride ( NaCl ).
Biosynthesis of some hormones needs some trace elements , for example iodine for thyroxin and zinc for insulin .
Biosynthesis of hemoglobin and myoglobin needs iron .
Water Importance total body water is about 45 liters
It acts as an excellent solvent inside the body.
It is very important for regulation of body temperature .
It is suitable medium for the different metabolic pathways.
Many waste products are excreted as soluble form in water .
It enters in the processes of digestion
It is comparatively more essential to life than foods.
Severe dehydration is dangerous hence , death happens if about 20 % of the body water is lost.
Total body water is About 45 liters Extracellular fluid (outside cells , 15 liters) Intracellular fluid (inside the cell 30 liters) tissue fluid (12 liters) Plasma (3 liters) introduction
Maintenance of water balance
For the body to remain in water balance: water gain should be equal to water loss.
Urine: about 1 liter/day.
Faeces (stool), about 100 ml/day.
Sweat and expired air: 600-1000 ml/day.
Water and other fluids taken as such (about 1200 ml/day)
Water of foods (about 100 ml/day).
Metabolic water (about 500 ml/day), produced from metabolic processes.
Water loss Water gain
Definition of carbohydrate
Carbohydrates are organic compounds which contain carbon, hydrogen and oxygen
Carbohydrates are widely distributed in living tissue, form an important source of energy.
They are stored as reserve food in the form of glycogen in animals and starch in plants.
Classification of Carbohydrates
They are classified according to the number of sugar units into 3 groups:
Monosaccharides (1 sugar unit)
Oligosaccharides (2 - 10 sugar unit)
Polysaccharides (more than 10 sugar units)
This group include sugars of one unit , and all members cannot be hydrolysed to simpler form.
Monosaccharides are classified according to
a-the type of the functional group
b-the number of carbon atoms
a-the type of the functional group
1) Aldosugar Contain aldehyde group
2) Ketosugar Contain ketonic group
b-the number of carbon atoms in to
1) Trioses (Tri means 3) Contain three carbon atoms . There are two types of trioses:
Aldotriose e.g. glycerose “Glyceraldehyde “.
Ketotriose e.g. dihydroxy acetone.
carbohydrate Glyceraldehyde Dihydroxy acetone
2) Tetroses which contain four carbon atoms (Tetra means 4 )
3) Pentoses which contain five carbon atoms (Penta means 5 )
4) Hexoses which contain six carbon atoms (Hexa means 6 )
D- glucose D-galactose D- mannose D-fructose
DDLD DLLD DDLL DDL carbohydrate
Biochemical and biological importance of hexoses
1-Glucose (Dextrose ) : is the sugar of blood. It is the principle sugar that is utilized by the tissues giving CO2 , H2O and energy. Glucose is the sugar of grape.
2-Fructose (Levulose) : is present in fruits, honey . Fructose is the sugar of fetal blood. Also it is the principle sugar of semen.
3-Galactose : is present in combination with glucose in milk sugar (Lactose).
4-Mannose : enters in the composition of mucopolysaccharides
These sugars are formed by condensation of two to ten molecules of monosaccharides producing di , tri , tetra ……..saccharides .
Disaccharides are the most important group.
Are formed by condensation of 2 simple sugars (i.e. 2 monosaccharides). Important examples are
Cane sugar, beet sugar or table sugar.
sucrose consists of one molecule of glucose and one molecule of fructose
Lactose is the milk sugar human milk has a concentration of 7g % lactose, also it is the milk sugar of all mammals .
It is formed by condensation of one molecule of galactose with a molecule of glucose
It considered a perfect sugar for babies because of It is not fermented , so do not produce gases , not so sweaty , mild laxative effects and the only natural source of galactose
Maltose is formed by condensation of two molecule of glucose
Maltose is produced during digestion of cooked starch by salivary amylase
1-They are composed of a great number of monosaccharide units
2-They are economically important beside their great importance in nutrition. Some important industries are dependent on polysaccharides, e.g.:
Manufacture of textiles.
Manufacture of artificial silk.
Manufacture of paper.
Classification of polysaccharides carbohydrate Examples: gums, pectin and mucopolysaccharides Examples: starch, dexterines, dextrans, glycogen and cellulose Contain different Sugar Formed of only one type of sugar B-Heteropolysaccharides A-Homopolysaccharides
Starch is the main carbohydrate of food it is the main storage from of carbohydrates in plants .
It exists in cereals (e.g. rice ,barley , maize and wheat ) and in roots and tubers like potatoes and sweat potatoes.
Starch never present in animals.
They are produced during enzymatic hydrolysis of starch by salivary amylase or pancreatic amylase enzymes.
These are polysaccharides produced by the actions of certain bacteria when allowed to grow on sucrose media . It is used as plasma substitute to increase blood volume after severe haemorrhage
Glycogen is the main storage from of carbohydrates in animals ( Sometimes called animal starch ).
It is stored in liver and muscles .
Glycogen granules in a hepatocyte. These granules form in the cytosol, and are much smaller than starch granules in plants. Glycogen granules
5-Ag ar-agar :
Agar agar is a polysaccharides formed of galactose.
It is prepared from sea weeds.
The importance of agar agar is due to its use as a culture medium for growing of bacteria in bacteriological studies.
Constitutes the walls of plant cells.
It is formed from glucose units joined together
It is insoluble in water therefore its fibers are used in manufacturing of textiles.
Cellulose is not digested by digestive juices, however ,cellulose is important in our diet for preventing constipation
1-Gums : Gums are derived from plants, they consist of a mixture of hexoses, pentoses and sugar acids
2-Pectins : Pectins are present in fruits , they are responsible for the gelling properties of jams. They are used in the treatment of infantile diarrhea.
They are distributed in animal tissues either combined with proteins in the form of mucoproteins or in free form.
They enter in the structure of most tissues and are not oxidized to give energy. They give more than one kind of sugar on hydrolysis .
DIGESTION OF CARBOHYDRATES
Blood glucose level
Normal blood glucose level:
Range from 70-140 mgdl Two hours after meal Range from 80-140 mgdl Direct after meal Range from 60-110 mgdl Fasting blood level
Factors affecting blood glucose level:
liver : NUTRIENT DISTRIBUTION CENTER
1-Liver: NUTRIENT DISTRIBUTION CENTER
After a meal containing carbohydrate, the liver becomes a net consumer of glucose, hepatic metabolism of glucose is increased by:
increased phosphorylation of glucose and
Increased glycogen synthesis
due to increase in the secretion of insulin which is a glucose lowering hormone
During fasting the liver first uses glycogen degradation, then gluconeogenesis (glucose synthesis) due to increase in the secretion of glucagon and stress hormones which are glucose increasing hormones to maintain blood glucose levels to sustain energy metabolism of brain and other glucose-requiring tissues. .
Glucose is continuously filtered by renal system, under normal conditions glucose completely return to circulation by reabsorptive renal system, when blood glucose level abnormally elevated and exceed the capacity of the reabsorptive renal system ( renal threshold is 180 mgdl ) glucose appear in urine ( glucosuria ).
Insulin is a key regulatory enzyme of blood glucose level, it is a polypeptide hormone produced by the beta cells of the islets of langerhans of the pancreas . Insulin decreases the production of glucose by inhibiting gluconeogenesis and the breakdown of glycogen.
It increases glucose uptake by increasing the number of glucose transporters in the cell membrane.
The intravenous administration of insulin thus causes an immediate decrease in the concentration of blood glucose.
Metabolic abnormalities of glucose level:
Hypoglycemia Blood glucose level equal to or less than 40 mgdl
Hyperglycemia It is the rise of blood glucose level above normal average level
Blood glucose level equal to or less than 40 mgdl and symptoms being resolved within minutes following the administration of glucose.
Hypoglycemia is a medical emergency because the central nervous system ( CNS ) has an absolute requirement for a continuous supply of blood-borne glucose to serve as fuel for energy metabolism.
Hypoglycemia is characterized by: 1) central nervous system symptoms, including confusion, aberrant behavior, or coma
Causes of hypoglycemia :
1- Insulin-induced hypoglycemia: Hypoglycemia occurs frequently in patients with diabetes receiving insulin treatment without eating.
2- Postprandial hypoglycemia: This is the second most common form of hypoglycemia is caused by an exaggerated insulin release following a meal, prompting transient hypoglycemia.
3- Fasting hypoglycemia: Low blood glucose occurring during fasting is rare, but is more likely to present as a serious medical problem. Often seen in patients with liver damage.
4- Hypoglycemia due to alcohol intoxication.
Causes of hyperglycemia :
Patient receiving IVF containing glucose
Diabetes is not one disease, but rather is a heterogeneous group of syndromes characterized by an elevation of fasting blood glucose caused by a relative or absolute deficiency in insulin .
Diabetes mellitus is the leading cause of adult blindness and a mputation , and a major cause of renal f ailure , heart attacks , and strokes .
Types of diabetes mellitus
Type 1 diabeties
The disease is characterizec by an absolute deficiency of insulin caused by an autoimmune attack on the cells of the pancreas. This destruction requires a stimulus from the environment (such as a viral infection) and a genetic predisposition.
The metabolic abnormalities of type 1 diabetes mellitus include hyperglycemia , ketoacidosis , and hypertriglyceridemia . They result from a deficiency of insulin . Type 1 diabetics must intake exogenous insulin injected subcutaneously to control hyperglycemia
Type 2 diabeties
It has a strong genetic component . Results from a combination of insulin resistance and dysfunctional cells .
Insulin resistance is the decreased ability of target tissues, such as liver, adipose tissue and muscle, to respond properly to normal circulating concentrations of insulin. Obesity is the most common cause of insulin resistance.
The metabolic alterations observed in type 2 diabetes are milder than those described for the insulin-dependent form of the disease.
Available treatments for diabetes moderate the hyperglycemia, but fail to completely normalize metabolism.
The long-standing elevation blood glucose causes the chronic complications in the form of atherosclerosis, retinopathy, nephropathy, and neuropathy.
Biochemical distrurbance in diabetes mellitus:
decrease intracellular glucose a sensation of hunger pain lead to polyphagia (escessive eating)
increase blood glucose cause increase in blood osmolarity thirst sensation ( poydepsia )
glucosuria : appear of glucose in urine
increase breakdown of tissue proteins cause muscle wasting
change in glucose blood level in diabetes mellitus: >200 mgdl Range from 140-200 mgdl Range from 70-140 mgdl Two hours postprandial >126 mgdl Range from 110-120 mgdl Range from 110-120 mgdl Fasting blood glucose Diabetic Impaired glucose utilization Normal