NUTRITIONAL CONSIDERATIONS OF THE NEWBORN

Growth and development:  Newborn infants are at special nutritional risk due to their body makeup versus nutritional requirements. In the first place, this is a period of very rapid growth, and needs for many nutrients are higher compared to an adult human being. Some micronutrients such as vitamins E and K, do not cross the placental membrane well and therefore, the tissue stores are low in the newborn infant. I have discussed a lot about vitamins E and K and if you have not been following me, you can click on the link below to read about them.  Vitamins

The gastrointestinal actecture:  The gastrointestinal tract may not be fully developed, leading to malabsorption problems  and especially true for fat-soluble vitamins. The gastrointestinal tract is also sterile at birth and the intestinal flora that normally provide significant amounts of certain vitamins especially vitamin K, take several days to become established. If the infant is born prematurely, the nutritional risk is slightly greater, since the gastrointestinal tract will be less well developed and the tissue stores will be less.  I have already talked about the human intestinal flora and their development from birth and if you have not been following me, you can read about normal flora and the human microbiome from the link below.  Normal flora of the human body

Hematological concerns:  The most serious nutritional complications of newborns appear to be hemorrhagic disease. Newborn infants, especially premature infants, have low tissue stores of vitamin K and lack the intestinal flora necessary to synthesize the vitamin. Breast milk is also a relatively poor source of vitamin K. 

It is estimated that, approximately 1 out of 400 live births shows some signs of hemorrhagic disease and in that case, one milligram of the vitamin at birth is usually sufficient to prevent hemorrhagic disease.

The burden of iron in the newborn:  Most newborn infants are born with sufficient reserves of iron to last 3–4 months. Since iron is present in low amounts in both cow's milk and breast milk, iron supplementation is usually begun at a relatively early age by the introduction of ironfortified cereal.

The issue with vitamin D and other minerals:  Vitamin D levels are also somewhat low in breast milk and supplementation with vitamin D is usually recommended.  Other vitamins and minerals appear to be present in adequate amounts in breast milk as long as the mother is getting a good diet.

RELATED;

1.  BODY METABOLISM AND HOMEOSTASIS

2.  VITAMINS

3.  DIGESTION AND ABSORPTION OF MINERALS

4. NORMAL FLORA OF THE HUMAN BODY

REFERENCES

BREAKDOWN OF FATS IN THE HUMAN BODY

 

INTRODUCTION: Fats are some of the chemicals of life that are used by the body to generate energy other than carbohydrates and proteins. We have discussed much about carbohydrates in our previous presentations and the several steps involved in energy production. In our discussion here, we are going to look at some of the processes through which fats are broken down, into which they become the second most immediate source of energy for the body.

LIPOLYSIS: The term lipolysis comes from lipids, which is another name for fats. This is the process of breaking down triglycerides, which are the main form of stored fat in the body, into glycerol and free fatty acids. Lipolysis is stimulated by hormones such as epinephrine, norepinephrine, glucagon, and growth hormone, which bind to receptors on the surface of fat cells and activate an enzyme called hormone-sensitive lipase. Lipolysis can also be induced by exercise, fasting, or low-carbohydrate diets .

BETA-OXIDATION: This is the process of converting free fatty acids into acetyl-CoA, which is a molecule that can enter the Krebs cycle and produce energy. Beta-oxidation occurs in the mitochondria, which are the powerhouses of the cells. Beta-oxidation requires oxygen and coenzymes such as NAD+ and FAD, which are derived from vitamins B3 and B2. Beta oxidation can also produce ketone bodies, which are alternative fuel sources for the brain and other organs.

THERMOGENESIS: This is the process of generating heat from metabolic reactions, which can increase the energy expenditure and fat burning of the body.  Those are some of the few processes where fats can be utilized in the human body.  In our next discussion, we shall be talking about the dangers of having too much body fat.

RELATED;

1.  PROTEINS

2.  DIGESTION OF LIPIDS

3.  EPINEPHRINE AS A HOMONE AND AS A DRUG

4. GLUCAGON

REFERENCES

MACROMOLECULES OF THE HUMAN BODY

MACROMOLECULES OF THE HUMAN BODY: Chemical life begins with atoms and ions and these may combine to form molecules.  In our basic chemistry, we looked at covalent molecules and ionic molecules and the forces that can bind two or more atoms to form molecules as described in the article below; The forces that bind molecules together.  Basically molecules maybe two or more atoms combined and then several different molecules can combine to form more complex structures known as macromolecules.  There are many macromolecules in the human body some of which act as enzymes, others hormones, and for some, as molecules of metabolism.  To get clear on some of the most useful molecules available in the human body, we need to classify them according to their functions but before we continue, if you have not been following us, you need to read about the previous topic; Diversity of biomolecules.  In this discussion, we are going to look at some of the most common macromolecules in the human body and their respective roles.

CARBOHYDRATES:  These are some of the most important biomolecules in nature and the human body needs a lot of them.  Carbohydrates are some of the most abundant chemicals of life in nature and we need them for provision of energy.  they are the universal sources of energy in the human body.  Carbohydrates are of different chemical structure and composition but in our discussion here, we shall be looking at starch and glycogen.

RELATED;

1.  Diversity of biomolecules

2.  Starch

3.  Polysaccharides 

EFFECTS OF ALCOHOL ON NUTRITION

INTRODUCTION: Alcohol also sometimes referred to as the demon drink is one of the most commonly consumed and abused drink in all nations.  It is thought that some moderate quantities of this monster drink poses beneficial effects on the body systems however, because of the potential for addiction and drug dependance, it is discouraged by many in our communities.  Continuous intake of alcohol on a daily basis and in large quantities lead to development of condition known and Chronic alcoholism that comes with various health concerns some of which, are deficiency in minerals and ions in the body. 

In this article, we are going to look at some of the mineral and ion deficiencies that affect people consuming large amounts of alcoholic beverages.  This is one of the series of discussions related to drug abuse and the human body.  Our discussion on alcohol started earlier and if you did not start with us, you can find more about the previous topics by clicking on the link below; Alcohol and the human body  Chronic alcoholics run considerable risk of nutritional deficiencies for most of the food nutrients. The most common problems are neurologic symptoms associated with thiamine or pyridoxine deficiencies and hematological problems associated with folate or pyridoxine deficiencies.

ORIGIN OF DEFICIENCIES: Although it is well known that chronic alcohol abusers tends to have reduced appetite, it should be noted that the deficiencies seen with alcoholics are not necessarily due to this effect and or poor diet alone, although it is often a strong contributing factor. Alcohol causes pathological alterations of the gastrointestinal tract that often directly interfere with absorption of certain nutrients and or impaired distribution of others as we are going to see.  It should always be remembered that long term consumption of alcohol leads to development of ulcerative intestinal conditions including but not limited to peptic ulcer disease and gastritis.  

The continued corrosion of the intestinal walls causes disruption of the nutrient absorbing surface area and disruption in the chemical environment that frequently leads to nausea and vomiting, all of which alters the metabolic processes.

INVOLVEMENT OF THE LIVER: So much we have discussed about the human liver and it's role in the human body plus, the conditions that affect it.  In case you have not been following me, you can use the links below to read more about the liver.  The liver is one of the most important sites of activation and storage of many vitamins.  In fact in the liver alone, there are are always thousands of chemical reactions going on whose effects control the body. 

The severe liver damage associated with chronic alcoholism appears to interfere directly with storage and activation of certain nutrients. Alcohol appears to interfere directly with folate absorption and alcoholic cirrhosis impairs storage of this nutrient.  To understand more about the way such processes are affected, you can read more about the functions of the liver from here.

It is also astonishing to know that alcohol induced hepatitis is one of the leading causes of death in chronic and heavy alcohol drinkers.

NEURONAL INVOLVEMENT: The most sounding and intended effects of alcohol from mild enjoyment to toxicity occurs in the Central nervous system and the brain mainly.  Some alcoholics also develop a peripheral neuropathy that responds to pyridoxine supplementation. This problem appears to result from impaired activation and increased degradation of pyridoxine.  Pyridoxine is simply vitamin B6 and it is involved in the normal functioning of the brain, spinal cord and peripheral nerves.  The toxic effects of alcohol on the central nervous system is not only seen in chronic alcoholism but also, several individuals intentionally tend to drink, perceiving it that alcohol cures some sort of pain.  This is why the drug is taken as one of the most common Over The Counter Medications.

The most dramatic nutritionally related neurological disorder is Wernicke–Korsakoff syndrome. This symptoms include mental disturbances, ataxia which is described as unsteady gait and lack of fine motor coordination, and uncoordinated eye movements.  This is especially true with acute intoxication of alcohol.

CARDIOVASCULAR INVOLVEMENT: Congestive heart failure similar to that seen with beriberi is also seen in a small number of these patients. While this syndrome may only account for a small percentage of alcohol related neurologic disorders, the response to supplemental thiamine is so dramatic that it is usually worth consideration.

CAUSES OF THIAMINE DEFICIENCY: The thiamine deficiency appears to arise primarily from impaired absorption, although alcoholic cirrhosis may also affect the storage of thiamine in the liver. While those are the most common nutritional deficiencies associated with alcoholism, deficiencies of almost any of the water soluble vitamins can occur and cases of alcoholic scurvy and pellagra are occasionally reported.

VITAMIN A DEFICIENCY: Chronic ethanol consumption causes an interesting redistribution of vitamin A stores in the body. Vitamin A stores in the liver are rapidly depleted while levels of vitamin A in the serum and other tissues may be normal or slightly elevated. Apparently, ethanol causes both increased mobilization of vitamin A from the liver and increased catabolism of liver vitamin A to inactive metabolites by the hepatic P450 enzyme system.

BONE AND CALCIUM DISTURBANCES: Alcoholic patients have decreased bone density and an increased incidence of osteoporosis. This probably relates to increased rate of metabolism of vitamin D to inactive products by an activated cytochrome P450 enzyme system. Dietary calcium intake is also often poor. In fact, alcoholics generally have decreased serum levels of zinc, calcium, and magnesium due to poor dietary intake and increased urinary losses.

ISSUES TO DO WITH IRON: Iron deficiency anemia is very rare unless there is gastrointestinal bleeding or chronic infection. In fact, excess iron is a more common problem with alcoholics. Many alcoholic beverages contain relatively high iron levels, and alcohol appears to enhance iron absorption.

SUMMERY:  In summery, chronic alcohol consumption is one of the leading causes of ion and mineral deficiencies.  The most common pathophysiology is that it impairs absorption of many minerals from the gastrointestinal tract and increases elimination of those absorbed via urine.

RELATED;

1.  Alcohol and the human body

2.  The human liver

3.  Functions of the human liver

4.  Vitamin A

5.  Osteoporosis

6.  Calcium and the human body

7.  Dynamics of drugs and the human body

8.  Drug addiction and dependency 

9.  Over the counter medications

REFERENCES

INSULIN AS A CHEMICAL OF LIFE

 

Introduction: Insulin increases the transport of glucose from the blood into cells by increasing the permeability of cell membranes to glucose. It should be noted however that the Brain, liver, and kidney cells, are not dependent on insulin for glucose intake.

Role of glucose in cells: Once inside cells, glucose is used in cell respiration to produce energy in form of ATP. The liver and skeletal muscles also change glucose to glycogen, a process biochemically known as glycogenesis, which means glycogen production and the implication is that glucose can be stored for later use.

Other roles of insulin other than glucose metabolism: Insulin is also important in the metabolism of other food types; it enables cells to take in fatty acids and amino acids to use in the synthesis of lipids and proteins and in this case not energy production. Without insulin, blood levels of lipids tend to rise and cells accumulate excess fatty acids. With respect to blood glucose, insulin decreases its level by promoting the use of glucose for energy production.

Secretion of Insulin and consequences of it’s deficiency: Insulin is a vital hormone that we cannot survive for very long without. A deficiency of insulin or in its functioning is called diabetes mellitus. Secretion of insulin is stimulated by hyperglycemia which is a condition of high blood glucose level. This state occurs after eating, especially of meals high in carbohydrates. As glucose is absorbed from the small intestine into the blood, insulin is secreted to enable cells to use the glucose for immediate energy. At the same time, any excess glucose will be stored in the liver and muscles as glycogen.

RELATED;

1.  Glucagon

2.  The endocrine pancreas

3.  Diabetes mellitus

REFERECES

AMINO ACIDS

INTRODUCTION: Proteins occur in every living organism, are of many different types, and have many different biological functions. The keratin of skin and fingernails, the spider webs, and the estimated 50,000 or so enzymes that catalyze the biological reactions in our bodies are all proteins. Regardless of their function, all proteins have a fundamentally similar structure and are made up of many amino acids linked together in a long chain.

AMINO ACIDS AS BUILDING BLOCKS OF PROTEINS: Amino acids, as their name implies, are difunctional. They contain both a basic amino group and an acidic carboxyl group. Their value as building blocks to make proteins stems from the fact that amino acids can join together into long chains by forming amide bonds between the NH2 of one amino acid and the CO2H of another. For classification purposes, chains with fewer than 50 amino acids are often called peptides, while the term protein is generally used for larger chains.

AMINO ACIDS AND ACID-BASE BALANCE: Because amino acids contain both basic amino and acidic carboxyl groups, they undergo an intramolecular acid–base reaction and exist in aqueous solution primarily in the form of dipolar ions, called zwitterions. Amino acid zwitterions are internal salts and therefore have many of the physical properties associated with salts. They are relatively soluble in water but insoluble in hydrocarbons and are crystalline substances with relatively high melting points. In addition, amino acids are amphiprotic, meaning that they can react either as acids or as bases, depending on the circumstances. 

EXCHANGE OF IONS BETWEEN AMINO ACIDS: In aqueous acid solution, an amino acid zwitterion is a base that accepts a proton onto its CO2 group to yield a cation; in aqueous base solution, the zwitterion is an acid that loses a proton from its NH3 group to form an anion.

RELATED

1.  PROTEINS

2.  DIVERSITY OF BIOMOLECULES

3.  NUCLEIC ACIDS

4.  FATTY ACIDS

REFERENCES

CALCIUM AND THE HUMAN BODY

ROLE OF CALCIUM AND VITAMIN D IN BONE HOMEOSTASIS: Calcium is the primary mineral responsible for bone formation and for maintaining bone health throughout the life span. This major mineral constitutes about 2% of our body weight and is also critical to proper functioning of the nervous, muscular, and cardiovascular systems. To maintain homeostasis, calcium balance in the body is regulated by parathyroid hormone (PTH), calcitonin, and vitamin. Acting together, these three substances regulate the rate of absorption of calcium from the gastrointestinal (GI) tract, the excretion of calcium from the kidney, and the movement of calcium into and out of bone.

BONE RESORPTION AND DEPOSITION: Secreted by the parathyroid glands, PTH stimulates bone cells called osteoclasts. These cells accelerate the process of bone resorption, demineralization that breaks down bone into its mineral components. Once bone is broken down (resorbed), calcium becomes available for transport to areas in the body where it is needed. The opposite of this process is bone deposition, or bone building, accomplished by cells called osteoblasts. This process, which removes calcium from the blood to be placed in bone, is stimulated by the hormone calcitonin. When serum calcium levels become elevated, calcitonin is released by the thyroid gland.

ROLE OF VITAMIN D IN CALCIUM METABOLISM: Vitamin D and calcium metabolism are intimately related: Absorption of calcium is increased in the presence of vitamin D, and inhibited by vitamin D deficiency. Thus, calcium disorders are often associated with vitamin D disorders. Vitamin D is unique among vitamins because the body is able to synthesize it from precursor molecules. Several steps, however, are required before vitamin D can act on target tissues. The inactive form of vitamin D, cholecalciferol, is synthesized in the skin from cholesterol. Exposure of the skin to sunlight or ultraviolet light increases the level of cholecalciferol in the blood. Cholecalciferol can also be obtained from dietary products such as milk or other foods fortified with vitamin D. Enzymes in the kidneys metabolize calcifediol to calcitriol, the active form of vitamin D. Parathyroid hormone stimulates the formation of calcitriol at the level of the kidneys. Patients with extensive kidney disease are unable to adequately synthesize calcitriol and thus frequently experience calcium and vitamin D abnormalities. The primary function of calcitriol is to increase calcium absorption from the GI tract. Dietary calcium is absorbed more efficiently in the presence of active vitamin D and parathyroid hormone, resulting in higher serum levels of calcium, which is then transported to bone, muscle, and other tissues.

ROLES OF CALCIUM IN THE BODY: The importance of proper calcium balance in the body cannot be overstated. Calcium ion influences the excitability of all neurons. When calcium concentrations are too high (hypercalcemia), sodium permeability decreases across cell membranes. This is a dangerous state, because nerve conduction depends on the proper influx of sodium into cells. When calcium levels in the bloodstream are too low (hypocalcemia), cell membranes become hyperexcitable. If this situation becomes severe, convulsions or muscle spasms may result. Calcium is also important for the normal functioning of other body processes such as blood coagulation and muscle contraction.

RELATED;

1.  Magnesium

2.  Vitamin D

3.  Osteoporosis 

REFERENCES

THE FORCES THAT INTERACT WITH BIOLOGICAL MOLECULES

 

COVALENT BONDS:  Molecules are formed by sharing of electrons between atoms and for covalent bonding, basically the atoms will be of the same type for example, the oxygen molecule O2, nitrogen molecule N2 are diatomic molecules made up of two atoms each.

IONIC BONDS OR ELECTROSTATIC BONDS: Ionic bonds result from the electrostatic attraction between two ionized groups of opposite charges. They are formed by transfer of one or more electrons from the outermost orbit of an electropositive atom to the outermost orbit of an electronegative atom. This transfer results in the formation of a cation and an anion, which get consequently bound by an ionic bond.  Common examples of such compounds include NaCl, KBr and NaF.

HYDROGEN BONDS:  These are formed by sharing of a hydrogen between two electron donors. Hydrogen bonds result from electrostatic attraction between an electro-negative atom and a hydrogen atom that is bonded covalently to a second electronegative atom. Normally, a hydrogen atom forms a covalent bond with only one other atom. However, a hydrogen atom covalently bonded to a donor atom, may form an additional weak association, the hydrogen bond with an acceptor atom.

In biological systems, both donors and acceptors are usually nitrogen or oxygen atoms, especially those atoms in amino (NH2) and hydroxyl (OH) groups. With regard to protein chemistry, hydrogen releasing groups are -NH (imidazole, indole,peptide); -OH (serine, threonine) and -NH2 (arginine lysine). Hydrogen accepting groups are COO–, (aspartic, glutamic) C=O (peptide); and S–S (disulphide).  The DNA structure for example is maintained by hydrogen bonding between the purine and pyrimidine residues.

HYDROPHOBIC INTERACTIONS:  Non-polar groups have a tendency to associate with each other in an aqueous environment; this is referred to as hydrophobic interaction. These are formed by interactions between nonpolar hydrophobic side chains by eliminating water molecules. The force that causes hydrophobic molecules or nonpolar portions of molecules to aggregate together rather than to dissolve in water is called the ‘hydrophobic bond’.  This serves to hold lipophilic side chains of amino acids together. Thus, nonpolar molecules will have minimum exposure to water molecules.  To understand more clearly, look at the structure of a cell membrane listed below.

 

RELATED;

1.  THE GLYCOSIDIC BOND

2. DNA THE GENETIC MATERIAL

3. NUCLEOTIDES

4. STRUCTURE AND PHYSIOLOGY OF A CELL MEMBRANE

REFERENCES

 

TERTIARY STRUCTURE OF PROTEINS

INTRODUCTION:  Secondary structure denotes the configurational relationship between residues which are about 3-4 amino acids apart; or secondary level defines the organization at immediate vicinity of amino acids. The tertiary structure denotes three dimensional structure of the whole protein. The tertiary structure defines the steric relationship of amino acids which are far apart from each other in the linear sequence, but are close in the three-dimensional aspect.

STABILITY OF THE TERTIARY STRUCTURE: The tertiary structure is maintained by non-covalent interactions such as hydrophobic bonds, electrostatic bonds and van der Waals forces. The tertiary structure acquired by native protein is always thermodynamically most stable.

DOMAIN:  This is the term used to denote a compact globular functional unit of a protein. A domain is a relatively independent region of the protein, and may represent a functional unit. The domains are usually connected with relatively flexible areas of protein. To give an example, Phenyl alanine hydroxylase enzyme contains 3 domains, one regulatory, one catalytic and one protein-protein interaction domains.

 

RELATED;

1.  BIOCHEMISTRY OF PROTEINS

2. BIOCHEMISTRY OF BONDS

3. IMMUNOGLOBULINES

4. ENZYMES

REFERENCES

MAGNESIUM (Mg++)

INTRODUCTION:  Magnesium is the fourth most abundant cation in the body and second most prevalent intracellular cation. Magnesium is mainly seen in intracellular fluid. Total body magnesium is about 25 g, 60% of which is complexed with calcium in bone.  One-third of skeletal magnesium is exchangeable with serum.  Magnesium orally produces diarrhea; but intravenously it produces CNS depression.

REQUIREMENT:  The requirement is about 400 mg/day for men and 300 mg/day for women. Doses above 600 mg may cause diarrhea. More is required during lactation. Major sources are cereals, beans, leafy vegetables and fish.

NORMAL SERUM LEVEL OF MAGNESIUM: Normal serum level Mg++ is 1.8-2.2 mg/dl. Inside the RBC, the magnesium content is 5 mEq/L. In muscle tissue Mg++ is 20 mEq/L. About 70% of magnesium exists in free state and remaining 30% is protein-bound (25% to albumin and 5% to globulin).  Homeostasis is maintained by intestinal absorption as well as by excretion by kidney.  Magnesium is reabsorbed from loop of Henle and not from proximal tubules.

FUNCTIONS OF MAGNESIUM:  1.  Mg++ is the activator of many enzymes requiring ATP. Alkaline phosphatase, hexokinase, fructokinase, phosphofructokinase, adenyl cyclase, cAMP dependent kinases among others. need magnesium.

2. Neuromuscular irritability is lowered by magnesium.

3. Insulin-dependent uptake of glucose is reduced in magnesium deficiency. Magnesium supplementation improves glucose tolerance.

 

RELATED;

1.  PLASMA PROTEINS

2. ENZYMES

3. VITAMIN C

4.  VITAMIN A

5.  VITAMINS AND MINERALS

6.  BIOCHEMISTRY

REFERENCES

CORTISOL

 

OBJECTIVES OF THE DISCUSSION:  By the end of this discussion, the reader/medical student will be able to;

1.  Describe cortisol and it's role in generation of stress situations

INTRODUCTION: In our discussion here, we will use cortisol as a representative of the group of hormones called glucocorticoids, because it is responsible for most of the actions of this group. Cortisol increases the use of fats and excess amino acids, in a metabolic pathway known as, gluconeogenesis for energy and decreases the use of glucose. This is called the glucose-sparing effect, and it is important because it conserves glucose for use by the brain.

SECRETION OF CORTISOL: Cortisol is secreted in any type of physiological stress situation including but no limited to; disease, physical injury, hemorrhage, fear or anger, exercise, and hunger. Although most body cells easily use fatty acids and excess amino acids in cell respiration, brain cells do not, so they must have glucose. By enabling other cells to use the alternative energy sources, cortisol ensures that whatever glucose is present will be available to the brain. 

Cortisol also has an anti-inflammatory effect. During inflammation, histamine from damaged tissues makes capillaries more permeable, and the lysosomes of damaged cells release their enzymes, which help break down damaged tissue but may also cause destruction of nearby healthy tissue. Cortisol blocks the effects of histamine and stabilizes lysosomal membranes, preventing excessive tissue destruction. Inflammation is a beneficial process up to a point, and is an essential first step if tissue repair is to take place. It may, however, become a vicious cycle of damage, inflammation, more damage, more inflammation, and so on in a positive feedback mechanism. Normal cortisol secretion seems to be the brake, to limit the inflammation process to what is useful for tissue repair, and to prevent excessive tissue destruction.

ADVERSE EFFECTS OF CORTISOL: Too much cortisol decreases the immune response, leaving the body susceptible to infection and significantly slowing the healing of damaged tissue. The direct stimulus for cortisol secretion is ACTH from the anterior pituitary gland, which in turn is stimulated by corticotropin releasing hormone (CRH) from the hypothalamus. CRH is produced in the physiological stress situations mentioned earlier. Although we often think of epinephrine as a hormone important in stress, cortisol is also important.

RELATED;

1. GLUCONEOGENESIS

2.  CATECHOLAMINES

3.  METABOLISM AND METABOLIC DISORDERS

4.  GLUCONEOGENESIS

5.  BIOCHEMISTRY

REFERENCES

CO-ENZYMES

 

INTRODUCTION: Enzymes may be simple proteins, or complex enzymes, containing a non-protein part, called the prosthetic group. The prosthetic group is called the co-enzyme and therefore may be non-proteins in nature. Usually the prosthetic group is heat stable than the protein component of the enzyme. The protein part of the enzyme is then named the apo-enzyme which is heat labile and then the two portions combined together is called the holo-enzyme.

CLASSIFICATION OF CO-ENZYMES: Co-enzymes may be divided into two groups;

1) Those taking part in reactions catalyzed by oxidoreductases by donating or accepting hydrogen atoms or electrons.

2) Those co-enzymes taking part in reactions transferring groups other than hydrogen.

In the first group, the change occurring in the substrate is counter-balanced by the co-enzymes. Therefore, such co-enzymes may be considered as co-substrates or secondary substrates.

NICOTINAMIDE ADENINE DINUCLEOTIDE (NAD+): This is a co-enzyme synthesized from Nicotinamide, a member of vitamin B complex. The reversible reaction of lactate to pyruvate is catalyzed by the enzyme lactate dehydrogenase, but the actual transfer of hydrogen is taking place on the co-enzyme, NAD⁺.

In this case, two hydrogen atoms are removed from lactate, out of which one hydrogen and two electrons are accepted by the NAD⁺ to form NADH, and the remaining H⁺ is released into the surrounding medium.

SECOND GROUP OF CO-ENZYMES: These co-enzymes take part in reactions transferring groups other than hydrogen. A particular group or radical is transferred from the substrate to another substrate. Most of them belong to vitamin B complex group.

ADENOSINE TRIPHOSPHATE (ATP): ATP is considered to be the energy currency in the body. In the ATP molecule, the second and third phosphate bonds are ‘high energy' bonds. During the oxidation of food stuffs, energy is released, a part of which is stored as chemical energy in the form of ATP. The endergonic reactions are carried out with the help of energy released from hydrolysis of ATP.

METALLO-ENZYMES: These are enzymes which require certain metal ions for their activity. In certain cases, such as copper in Tyrosinase, the metal is tightly bound with the enzyme. In other cases, even without the metal ion, enzyme may be active; but when the metal ion is added, the activity is enhanced. They are called ion-activated enzymes, for example, calcium ions will activate pancreatic lipase.

Co-factors: The term co-factor is used as a collective term to include co-enzymes and metal ions. Co-enzyme is an organic co-factor.

RELATED;

1. LACTATE

2. PYRUVATE

3. BIOCHEMISTRY OF ENZYMES

4. BIOMOLECULES AND CHEMICALS OF LIFE

REFERENCES

PLASMA PROTEINS

 

INTRODUCTION: Total blood volume is about 4.5 to 5 liters in adult human being. If blood is mixed with an anticoagulant and centrifuged, the cell components which iclude Red blood cells (RBC) and white blood cells (WBC) are precipitated. The supernatant is called plasma. About 55-60% of blood is made up of plasma. If blood is withdrawn without anticoagulant and allowed to clot, after about 2 hours liquid portion is separated from the clot. This defibrinated plasma is called serum, which lacks coagulation factors including prothrombin and fibrinogen.

PROTEINS IN BLOOD: Total protein content of normal plasma is 6 to 8 g/100 ml. The plasma proteins consist of albumin, which is about 3.5 to 5 g/dl, globulins which make up 2.5-3.5 g/dl and fibrinogen making it to about 200-400 mg/dl. Almost all plasma proteins, except immunoglobulins are synthesized in liver. Plasma proteins are generally synthesised on membrane-bound polyribosomes. Most plasma proteins are glycoproteins.

RELATED;

1. BLOOD AND IT’S COMPONENTS

2. PROTEINS

3. IMMUNOGLOBULINS

REFERENCES

VITAMINS AND MINERALS

 

INTRODUCTION: Vitamins are organic molecules needed in very small amounts for normal body functioning. Some vitamins are coenzymes; that is, they are necessary for the functioning of certain enzymes. Others are antioxidant vitamins, including vitamins C, E, and betacarotene, which is a precursor for the synthesis of vitamin A. Antioxidants prevent damage from free radicals, which are molecules that contain an unpaired electron and are highly reactive. The reactions of free radicals can damage DNA, cell membranes, and the cell organelles.

FORMATION OF FREE RADICALS: Free radicals are formed during some normal body reactions, but smoking and exposure to pollution will increase their formation. Antioxidant vitamins combine with free radicals before they can react with cellular components. Plant foods are good sources of these vitamins.

DEFICIENCY OF VITAMINS: Deficiencies of vitamins often result in diseases including but not limited to: vitamin C deficiency and scurvy, for example. Other deficiency diseases that have been known for decades include pellagra which is due to lack of niacin, beri-beri which is due to lack of riboflavin, pernicious anemia for lack of vitamin B12, and rickets for lack of vitamin D. More recently the importance of folic acid (folacin) for the development of the fetal central nervous system has been recognized. Adequate folic acid during pregnancy can significantly decrease the chance of spina bifida also known as, open spinal column and anencephaly which is the absence of the cerebrum and always fatal in a fetus. All women should be aware of the need for extra folic acid during pregnancy.

MINERALS IN THE HUMAN BODY: Minerals are simple inorganic chemicals and have a variety of functions, many of which you are already familiar with. Among some of the most important minerals we have Sodium and potassium which are very important in the normal functioning of the nervous system and the heart, Calcium important in bone formation, Magnesium and phosphorous as we shall be discussing them in details later.

RELATED;

1. VITAMIN A

2.  VITAMIN C

3.  MAGNESIUM

4.  DYNAMICS OF THE HUMAN BODY

REFERENCES

COLLOIDS

 

INTRODUCTION: Colloids are proteins, starches, or other large molecules that remain in the blood for a long time because they are too large to easily cross the capillary membranes.

EFFECTS OF COLLOIDS: While circulating, they have the same effect as hypertonic solutions, drawing water molecules from the cells and tissues into the plasma through their ability to increase plasma osmolality and osmotic pressure. Sometimes called plasma volume expanders, these solutions are particularly important in treating hypovolemic shock due to burns, hemorrhage, or surgery

EXAMPLES OF COLLOIDS: The most commonly used colloid is normal serum albumin, which is featured as a prototype drug for shock. Several colloid products contain dextran, a synthetic polysaccharide. Dextran infusions can double the plasma volume within a few minutes, although its effects last only about 12 hours.

Plasma protein fraction is a natural volume expander that contains 83% albumin and 17% plasma globulins. Plasma protein fraction and albumin are also indicated in patients with hypoproteinemia. Hetastarch is a synthetic colloid with properties similar to those of 5% albumin, but with an extended duration of action.

RELATED;

1.  INTRAVENOUS INFUSION OF FLUIDS

2.  PLASMA VOLUME EXPANDERS

3.  ANATOMY AND PHYSIOLOGY

REFERENCES

DIGESTION OF LIPIDS

 

INTRODUCTION: The major dietary lipids are triacyl glycerol, cholesterol and phospholipids. The average normal diet contains about 20-30 g of lipids per day. Western diet generally contains two or three times more than this quantity.

DIGESTION IN STOMACH: The lingual lipase from the mouth enters stomach along with the food. It has an optimum pH of 2.5-5. The enzyme, therefore, continues to be active in the stomach. It acts on short chain triglycerides (SCT). SCTs are present in milk, butter and ghee. The action of lingual lipase is observed to be more significant in the newborn infants. Gastric lipase is acid stable, with an optimum pH around 5.4. It is secreted by chief cells, the secretion is stimulated by gastrin. Up to 30% digestion of triglycerides occurs in stomach.

DIGESTION IN INTESTINES: Emulsification is a prerequisite for digestion of lipids. The lipids are dispersed into smaller droplets; surface tension is reduced; and surface area of droplets is increased. This process is favored by:

1. Bile salts also known as detergent action

2. Peristalsis which provides mechanical mixing

3. Phospholipids

ENZYMES IN INTESTINES:

1. Pancreatic lipase with Co-lipase

2. Cholesterol esterase

3.Phospholipase A2.

The bile (pH 7.7) entering the duodenum serves to neutralise the acid chyme from the stomach and provides a pH favorable for the action of pancreatic enzymes.

DIGESTION OF TRIGLYCERIDES: 1. Pancreatic lipase can easily hydrolyse the fatty acids esterified to the 1^st and 3^rd carbon atoms of glycerol forming 2-monoacylglycerol and two molecules of fatty acid.

2. Then an isomerase shifts the ester bond from position 2 to 1. The bond in the 1st position is then hydrolysed by the lipase to form free glycerol and fatty acid.

3. The major end products of the digestion of TAG are 2-MAG (78%), 1-MAG (6%), glycerol and fatty acids (14%). Thus digestion of TAG is partial (incomplete).

4. Cholesterol ester may be hydrolysed to free cholesterol and fatty acid. The action of phospholipase A2 produces lysophospholipid and a fatty acid.

Co-lipase: The binding of co-lipase to the triacyl glycerol molecules at the oil water interface is obligatory for the action of lipase. The co-lipase is secreted by the pancreas as an inactive zymogen. It is activated by trypsin.

RELATED;

1.  PHASES OF METABOLISM

2.  METABOLISM OF PROTEINS

3.  METABOLISM AND METABOLIC DISORDERS

REFERENCES