Lipids

                    Lipids

Importance-
The lipids are important constituents of the diet because of their high energy value and also because of the fat soluble vitamins and the essential fatty acids found with the fat of the natural food stuffs. In the body, the fats serve as efficient source of energy which is stored in the adipose tissues. They also serve as an insulating material in the subcutaneous tissues and around certain organs. Fats combined with proteins(lipoproteins) are important constituents of the cell membranes and mitochondria of the cell.
          Proteins, polysaccharides, DNA and RNA are macromolecules. Lipids are not generally classed as macromolecules, even though they share some of their features: for example most are synthesized as linear polymers of a smaller molecule (the acetyl group on acetyl- CoA), and their self assemble into larger structures (membranes).  It is noteworthy that water and protein comprise most of the mass of both mammalian and bacterial cells.

Definition-
The lipids are a heterogeneous group of compounds related to fatty acids and include fats, oils, waxes and other related substances. These are oily or greasy organic substances, relativity insoluble in water and considerably soluble in organic solvents like ether, Chloroform and benzene. They are, thus hydrophobic in nature. These are variously called as lipins or lipoids. The latter term is, however sometimes used to refer "fat- like" substances which may not actually be related to the fatty acids. The term lipid was first used by the German biochemist Bloor in 1943 for a major class of tissue components and foodstuffs.
           Chemically the fats are defined as the Esters of glycerol and fatty acids or as the triglycerides of fatty acids.


H2C-OH        HOOC.C15.H31
      |
   HC-OH   +  HOOC.C15.H31  ==>
      |
H2C-OH        HOOC.C15.H31
(Glycerol)   (Palmitic acid)
(1 mole)         (3 mole)

H2C-OOC.C15.H31
      |
   HC-OOC.C15.H31  + 3H2O
      |
H2C-OOC.C15.H31

(Tripalmitin)

     (1 mole)



 Fatty acids-
Fatty acids are long chain organic acids having usually from 4 to 30 carbon atom; they have a a single carboxyl group and a long, nonpolar hydrocarbon 'tail', which gives most lipids their hydrophobic and oily or greasy nature. Fatty acids do not occur in free or uncombined state in cells or tissues but are present in covalently bonded form in different classes of lipids. Fatty acids which occur in natural fats are usually monocarboxylic and contain an even number of carbon atoms as these are synthesized from 2 Carbon units. These are usually straight chain derivatives. The chain may be saturated (containing only single bonds) or unsaturated (containing one or more double bonds). Some fatty acids may have hydroxyl group in the chain and still others may possess ring structure (cyclic fatty acids). Fatty acids are stored as an energy reserve (Fat) through and Easter linkage to glycerol to form triglycerides. If free, the carboxyl group of a fatty acids will be ionized.

                         _
                      O
                      |
/\/\/\/\/\/\/\/\/\/C=O

Human Digestive system

Nutrition in human beings-

Human beings are heterotrophic omnivorous organisms. They obtain their food from plants, animals and their products by holozoic mode of nutrition. The essential components of human diet are  water, carbohydrates, fats, proteins, minerals and vitamins.

Human Digestive system-

The human digestive system consists of an alimentary canal and many digestive glands. So human digestive system is divided into two main parts the first one is the alimentary canal and the other one is different digestive glands associated with alimentary canal.

(1) Alimentary canal
(2) Digestive glands associated with alimentary canal


(1) Alimentary canal-


The alimentary canal is a long tube with muscular walls, glandular epithelial lining and varying diameter. It extends from the mouth to the anal opening (anus). When uncoiled, the alimentary canal measures nearly 9 metre long tube in which the ducts of several digestive glands open to secrete their respective digestive secretions. The alimentary canal consists of several organs. These organs are given below in the order in which they are involved in digesting food.

(A) Mouth
(B) Buccal (or oral) cavity
(C) Pharynx
(D) Oesophagus
(E) Stomach
(F) Small intestine
(G) Large intestine

(A) Mouth-
Mouth is the uppermost opening of human digestive system which gives passage for ingestion of food. It is guarded by two soft movable lips and opens into a chamber or cavity called buccal cavity.

(B) Buccal (or oral) cavity-
It is a large space bounded above by the palate, below by the throat and on the sides by the jaws. The throat supports the muscular tongue which forms the floor of this cavity and helps in injestion of food.

Teeth-

The jaws bear teeth. Both upper and lower jaws are provided with teeth. Each jaw has two pairs of incisors, one pair of canines, two pairs of premolars and three pairs of molars. Thus, each jaw possesses total 16 teeth and human adults has 32 permanent teeth. The incisors are sharp and have cutting edges. The canines are pointed and occur next to the incisors  The premolars and molars are called the grinding teeth. Teeth cut the food into small pieces and chew them to make it soft for easy swallowing. The full dental formula (arrangement of teeth) of humans is represented as-
    I2/2,C1/1,Pm2/2,M3/3

Salivary glands-

The buccal cavity has three pairs of salivary glands located at at different locations the parotid glands lie on the sides of the face sublingual glands lie under the front part of the tongue and submaxillary gland lie at the angles of the lower job these celebrity glands secrete saliva through their ducks saliva contains these salz new seen and an enzyme ptyalin. the enzyme ptyalin is celebrity mileage which splits starch and glycogen into maltose carbohydrate digestion begins in the buccal cavity itself which is responsible for hydrolysis of about 30% starch present in the food.

(C) Pharynx-

The pharynx is about 12 centimetre long funnel shaped vertical canal which serves as a passage way for the food from the buccal cavity to the oesophagus.


(D) Oesophagus-

The oesophagus is a long and tubular structure which serves to carry the food from pharynx to the stomach. The wall of oesophagus is highly muscular. The oesophagus is not concerned with the digestion of the food. It exhibits peristaltic movement, i.e., contraction and expansion movement of walls, so that the partially digested food is pushed forward in the track. In fact, this movement occurs throughout the alimentary canal.


(E) Stomach-

The stomach is a wide C-shaped or j- shaped muscular sac present on the left side of the abdomen. Partially digested food reaches into the stomach from the buccal cavity through pharynx and oesophagus. Now further digestion of food takes place in the stomach. The stomach serves 4 main functions:
(a) storage of food - The food is Stored in the stomach variable duration. Carbohydrates continue to get digested till the salivary enzyme ptyalin is destroyed by the hydrochloric acid secreted in the stomach. The carbohydrates remain in the stomach for about one or two hours proteins up to 3 hours and fats for 3 to 6 hours. Storage of food in the stomach enables us to take food at intervals.
(b) Mechanical churning of food-  Wall of the stomach undergoes periodic muscular contraction so that the food gets churned and mixes thoroughly with the gastric juice .
(c) Partial digestion- Stomach possess branched and tubular glands present on the inner surface of its wall. There are three types of glands which secrete hydrochloric acid, protein digesting enzyme and mucus. All these secretions are collectively called gastric juice. The hydrochloric acid makes the medium is acidic. Protein digesting enzyme pepsin acts in acidic medium which breaks down proteins into peptones. Gastric juice also contains some gastric lipase which partially breaks down lipids. The gastric juices can also be secreted in the stomach by the sight, smell or thought of appetising food.
(d) regulation of the flow of food into the small intestine- The stomach regulate the flow of partially digested food into the small intestine.


(F) Small intestine-
The small intestine is the longest part of the alimentary canal. It is a narrow tube of about 6 metres which lies coiled in the abdomen. The length of small intestine vary in different animals depending on the type of food they eat. It is comparatively longer in herbivores animals which eat grass and shorter in carnivorous which eat meat. Long intestine of herbivores is helpful in digestion of cellulose. Meat is digested easily, therefore carnivores have a shorter small intestine. Partially digested and churned food from the stomach enters into the small intestine. The exit of food from the stomach is regulated by the sphincter muscles located at the pyloric end. This food is acidic which has to the made alkaline before further digestion.

(G) Large intestine-

The small intestine is followed by large intestine which is shorter but wider than a small intestine. It is arranged around the mass of small intestine in the form of a question mark (?). It lacks villi but secretes mucus. The greater part of large intestine is colon which gives sacculated appearance due to a series of constrictions. The colon is followed by about 15 to 20 cm long vertical column called rectum. It has longitudinal folds and large blood vessels. The undigested food is collected as faeces in the rectum. The rectum leads through 2 to 5 cm long anal canal to the exterior at the anus. The rectal wall mainly absorbs water from the undigested food. It also secrets mucus for lubrication . The faecal matter is egested out through an opening by the activity of anal sphincter.


(2) Digestive glands associated with alimentary canal-

Human digestive system having different types of digestive glands which is helpful in the digestion of the food. Some important digestive glands which is helpful in the process of digestion are given below-

(A) Salavary glands
(B) Gastric glands
(C) Liver
(D) Pancreas
(E) Intestinal glands

Carbohydrates

Carbohydrates-

Importance-

The carbohydrates are often termed as sugars are the 'staff of life' for most organisms. On the basis of mass, they are the most abundant class of biomolecules in nature. Carbohydrates are also known as saccharides (sakcharon = Sugars or sweetness) since many of those of relatively small molecular weight have a sweet taste, although this is not true of those with large molecules. They are widely distributed molecules (moles = mass) in both plant and animal tissues. They are indispensable for living organisms, serving as a skeletal structures in plants and also in insects and crustaceans. They also occur as food reserves in the storage organs of plants and in the liver and muscles of animals. In addition, they are an important source of energy required for the various metabolic activities of the living organisms; the energy being derived as a result of their oxidation. They also serve to lubricate skeletal joints, to provide adhesion  between cells and to confer  biological specificity on the surface of animal calls.
          Plants are  considerably richer in carbohydrates in comparison to the animals. In fact, animal and plant tissues differ widely in the relative abundance of the various major classes of constituent chemicals.

Nomenclature and definition-

The term carbohydrate was  originally coined  for this class of compounds has most of them were 'hydrates of carbon' or could be represented by the general formula Cx(H2O)y. Later it was found that some of them such as deoxyribose (C5H10O4) and Rhamnose (C6H12O5) do not have the required ratio of hydrogen to oxygen. In addition certain other carbohydrates are now known to possess nitrogen (e.g.,glucosamine C6H13O5N), phosphorus or sulphur also and obviously do not coincide with the above general formula.
        Hence the continued uses of the term carbohydrate is for convenience rather than exactness.
          To accommodate a wide variety of compounds the carbohydrates are nowadays broadly defined as polyhydroxy aldehyde or  ketones and their derivatives or as  substances that yield  one of these compounds on hydrolysis.

Classification-

Carbohydrates are usually classified in three groups:-

(1) Monosaccharides-
( Mono=one ; sakcharon = sugar)

The monosaccharides often called simple sugars, are compounds which possesses a free aldehyde (-CHO) or Ketone (=CO)group and two or more hydroxyl (-OH)groups. They are, in fact the simplest sugars and cannot be hydrolysed into smaller units. Their general formula is Cn(H2O)n.
          The monosaccharides may be subdivided into trioses, tetroses, pentoses, hexoses heptoses etc., depending upon the number of carbon atoms they possess; and as aldoses or ketoses, depending upon whether they contain aldehyde or Ketone group.  some important examples are-
  Name   |   Aldoses  |      Ketoses 

                |                   |
  Trioses | Glycerose|Dihydoxy-
                |                   |  acetone
Tetroses |Erythrose |Erythrulo-                                                    se  Pentoses|Ribose       |Ribulose                           
Hexoses |Glucose     |Fructose                                 
Heptoses|Gluco-       |Sodo-                                                |heptulose                         heptose 
                |                   |
                |                   |

(2) Oligosaccharides-
( Oligo=few  ; sakcharon = sugar)

  These are compound Sugars that yield 2 to 10 molecules of the same or different monosaccharides on hydrolysis.  Accordingly, an oligosaccharide yielding two molecules of monosaccharide on hydrolysis is designated as a disaccharide, and the one yielding three molecules of monosaccharide as a trisaccharide and so on. The general formula of disaccharides is Cn(H2O)n-1 and that of trisaccharides is Cn(H2O)n-2 and so on. A few examples are-

Disaccharides -
 sucrose, Lactose , maltose etc.

Trisaccharide -
Raffinose, Rhamninose, etc.

Tetrasaccharides -
Scorodose, Stachyose etc.

Pentasaccharides-
Verbascose

(3) Polysaccharides-
( Poly =many  ; sakcharon = sugar)

 These  are also compound Sugars and yield more than 10 molecules of monosaccharides on hydrolysis. These may be further classified depending on whether the monosaccharide molecules produced as a result of the hydrolysis of polysaccharides are of the same type(Homopolysaccharides) or of different types(Heteropolysaccharides). Their general formula is (C6H10O5)x.
   Some common examples are-

Homopolysaccharides -
starch, glycogen, inulin, cellulose, pectin, chitin etc.

 Heteropolysaccharides-
 Hyalueonic acid,  Chindrotin etc.

Blood circulatory system (Blood vascular system )

Blood circulatory system    (Blood vascular system )

Blood circulatory system is regarded as a kind of vascular system and therefore, it is called blood vascular system. A vascular system is that which has tubes full of fluid to be transported from one place to another.  The blood vascular system comprises of heart, the organ which pumps and receives the blood, and blood vessels, which are tubes through which the blood flows. 

   Blood vessels-

The blood vessels are elastic muscular tubes which carry blood. There are three kinds of blood vessels in human body.

    They are of three types-(1)Arteries 

(2)veins and 

(3)capillaries.

(1)Arteries-

Arteries are the thick walled blood vessels which carry blood away from the heart for distribution to the body. The walls of arteries particularly those near the heart are thick that enables them to dilate but not rupture when the heart contracts and forces blood into them. Thus the blood passing through narrow lumen of arteries is aerated and has a considerable pressure.

(2) Veins -

veins are thin walled blood vessels which bring blood from the body back to the heart. They are larger and hold more blood than the arteries. The blood passing through wide lumen of veins is nonaerated and has low pressure. It flows slow and steady. The veins have valves that allowed the blood to flow only towards the heart and prevent the backflow.

(3) Capillaries-

Capillaries are thin walled and extremely narrow blood vessels which occur at the terminals of artery and vein. They join the arteries and veins together. They form a vast network of vessels. The wall of capillaries are permeable to water and dissolved substances so that the exchange of materials between the blood and body cells takes place. The blood also flows very slow which facilitates the exchange of food material, gases and waste products.

The Human Heart-

The heart is a hollow, muscular organ roughly of the size of our clenched fist (12 × 9 CM). Its average weight is about 300 gram in males and about 250 gram in females. It is reddish- brown in colour and somewhat conical in form. The heart is situated between the two lungs in the middle of the thoracic cavity.  It is surrounded by a tough, two layer Sac, the pericardium. The pericardial fluid is secreted in the pericardial cavity between the pericardium and heart which reduces the friction between the heart wall and surrounding tissues when the heart is beating.

Structure of heart-

The heart is a double pump. It is divided by septa into two halves: the right and the left. Each half consists of two communicating Chambers: upper smaller auricle or atrium and lower larger ventricle. Thus the heart has four Chambers: The two upper Chambers called atria and two lower Chambers called left and right ventricles. There are valves between left atrium and left ventricle and between right atrium and right ventricle. These valves provide one way passage and prevent the return of blood. That means these two valves permit the flow of blood from atrium to ventricle and not in the reverse order . The walls of heart are composed of special muscle cells, called cardiac muscle fibres.

Function of heart-

The most vital function of heart is heartbeats which takes place all the time throughout one's life

. The sequence of events which takes place during the completion of one heartbeat is called the cardiac cycle. It involves repeated rhythmic contraction and relaxation of heart muscles. Contraction is called systole and relaxation is called diastole. The cardiac cycle involves the  followings:

(1) During the time when the muscles of all four Chambers of the heart and relaxed the blood returning to the heart under low pressure in the veins enters the two atria. Blood from large veins called vena cava pour into right atrium. This blood comes from head, upper body parts and lower body parts where oxygen has been used up and the blood is free from oxygen (deoxygenated). Thus the deoxygenated blood enters the right atrium. At the same time the pulmonary vein from lungs pours oxygenated blood into the left atrium. Thus the oxygenated blood enters the left atrium.

(2) As the right and left Atria filled with blood pressure in them rises so that the walls between left atrium and left ventricle (bicuspid valve) and between right atrium and right ventricle (tricuspid valve) open and the Atria contract. Atrial contraction (atrial diastole) faces pumping of deoxygenated blood from right atrium into the right ventricle through tricuspid valve and oxygenated blood from left atrium into left ventricle through bicuspid valve.

(3) Almost immediately the ventricles contract. This is called ventricular systole. During contraction of ventricles the deoxygenated blood from right ventricle flows to the lungs through pulmonary artery and the oxygenated blood from left ventricle is distributed to all the parts of the body through the largest artery called aorta.

Double circulation-
The blood circulation in human heart is double circulation. This means that blood passes through the heart twice for each circuit of the body. One circulation involves the entry of blood from all body parts into the heart. This blood is deoxygenated which goes to the lungs for oxygenation. The second circulation involves entry of oxygenated blood from lungs into the heart and then its distribution to all parts of the body. Double circulation is made possible because the human heart is divided into two. One-half pumps de- oxygenated blood to the lungs and the other half pumps oxygenated blood to the rest of the body.

Reproductive system of human beings

Reproductive system of human beings -

Human beings are unisexual and the human reproduction is highly evolved. There is a distinct sexual dimorphism. Thus, the structures associated with reproduction are different in males and females. The structures associated with male reproduction constitutes the male reproductive system. similarly, The structures associated with female reproduction constituted the female reproductive system. The reproductive systems of males and females consists of many organs which are distinguishable into primary and secondary sex organs.

Primary sex organs-
The primary sex organs are gonads, which produce gametes and sacrete sex hormones. The gonads of the male are called testes which produce male gametes- sperms and the male hormone- testosterone . The gonads of the female are ovaries which produce female gamete- ova and female hormones -estrogen and progesterone.

Secondary sex organs-
The secondary sex organs include the genital ducts and glands which help in transportation of gametes and reproductive process. They do not produce gametes or secrete hormones.

Male reproductive system-

Human male reproductive system consists of the following organs-
(1) Testes
(2) Scrotum
(3) Vas Deferens
(4) Urethra
(5) penis

(1) Testes -
The human male possesses to testes, which are the primary reproductive organs, lying outside the abdominal cavity. The two testes are the male gonads, which are the sites where male gametes (sperms) are made. The tastes also produce the male sex hormone- testosteron. The testes of man produce sperms from puberty onwards, throughout his life.
(2) Scrotum-
The scrotum is a pouch of skin that hangs between the legs. It is divided internally into right and left scrotal sacs by a muscular partition. The two tastes lie in respective scrotal sacs. The scrotum acts as a thermoregulator and provides an optimal temperature for the formation of sperms. The sperms develop at a temperature 1-3°C lower than the normal body temperature. The life of sperms is greatly reduced if the temperature is higher. During winters when temperature falls the scrotum shrinks to bring the testes close to body to get warmth. During summers when temperature rises the scrotum becomes relaxed to loss heat.
(3) Vas deferens -
This is a straight tube about 40 cm long which carries the sperms to the seminal vesicles. The sperms are stored temporally in the seminal vesicle where mucus and a watery alkaline fluid containing the sugar fructose mix with the the sperms.
(4) Urethra-
It is about 20 cm long tube that arises from the urinary bladder to carry urine. It runs through the penis and opens to the outside from male genital pore. The contents of two seminal vesicles sperm from was difference also join the urethra. Thus urethra carries urine from the bladder as well as sperms from the Vas diferentia through the penis.
(5) Penis-
Penis is a long and thick muscular organ made up of mostly erectile tissue. The tip of penis consists of a soft and highly sensitive glans penis which is covered by a loose retractable fold of skin called foreskin. At the time of sexual excitement the erectile tissue gets filled with blood causing the penis to become erect. It is inserted into the vagina of the female where sperms are ejaculated for the purpose of reproduction.
            In human males there is only one opening for the urine and sperms to pass out of body.



Female reproductive system-

Female reproductive system is more complex as compared to that of males. The complexity of sexual structures in females is due to the fact that it accepts sperm from male, supports their movement up to egg, fertilization and subsequent post fertilization changes. Female reproductive system consists of the following organs.

(1)  Ovaries
(2) Fallopian tubes (oviduct)
(3) Uterus
(4) Vagina

(1) Ovaries -
Each human female contains two almond shaped ovaries located in the lower part of abdominal cavity near the kidney. Each ovary is connected by a ligament to the uterus.  The ovaries are primary sex organs (or female gonads) which  perform the dual function - (a)production of female gametes (eggs or ova) and (b) secretion of female sex hormones (estrogen and progesterone. Each ovary is composed of ovarian follicles at various stages of development. Each follicle contains a large ovum surrounded by many layers of follicle cells. The production of ova starts at the age of puberty. Usually one ovum is produced every month during the fertile years of a woman. After menopause the ovaries become small and loss follicle.

(2) Fallopian tubes (oviduct)-
A fallopian tube is about 10 to 12 cm long muscular tube which carries egg from the ovary to the uterus and also provides the appropriate environment for its fertilization. The funnel shaped opening end of each fallopian tube lies near the posterior ends of each ovary. The other ends of the long convoluted tubes open into the uterus.

(3) Uterus-
The uterus is a large inverted pear-shaped muscular structure that lies behind the bladder. If fertilization takes place the embryo gets attached to the wall of uterus and grows there until birth.

(4) Vagina -
This is a muscular tube about 7 to 10 cm long whose walls contain elastic tissue. It is well adapted to receive the male's penis during copulation. The vagina is also called birth canal as it allows  passage of the baby at the time of childbirth.
              In human females the urinary opening (external opening of urethra) and vaginal openings are separate.

Excretory system of human beings

     Excretion in human beings

Excretory system-

Excretory system in human beings (also known as urinary system) consists of a pair of kidneys, a pair of ureters ,a urinary bladder and a urethra .
The two kidneys are located towards the back of the lower part of the abdominal cavity, one on either side of the backbone. Left kidney is slightly larger and placed a little higher than the right kidney. The blood from aorta enters into kidneys via the renal arteries and returns to the posterior Vena cava via renal veins. Urine formed in the kidneys passes by a pair of ureters to the bladder where it is stored until it is released via the urethra.

Structure and function of kidneys-

There are two kidneys in humans each kidney is purplish- brown, slightly flattened and shaped somewhat like rajma Bean. It is about 12 centimetre long, about 6 CM thick and wait about 150 grams. Internally a kidney is made of numerous microscopic excretory units called nephrons. Single kidney contains about a million nephrons each approximately 3 centimetre long.

           The most important function of kidney is filtration of blood to excrete the waste products of metabolism. If these waste products mainly nitrogenous waste such as urea and uric acid are not removed from the blood they will start accumulating to unbearable toxic levels. Besides filtering out the waste products the kidneys perform other functions such as osmoregulation, secretion of erythropoietin, enzyme - renin and conversion of inactive form of vitamin D to the active form. The kidney filter about 190 litres of blood to produce 0.9 to 1.9 litres of urine daily.

Structure and function of nephrons -

Each nephron has a  cup shaped upper end called Bowmen's capsule. It contains a bundle of blood capillaries called glomerulus. The blood entering into the glomerulus carries waste materials which are filtered out in the Bowmen's capsule. Filtration is possible because the walls of glomerular capillaries and Bowmen's capsule are very thin and are selectively permeable. This property of membranes allows water and small molecules in the blood to pass through them.
             Once the waste material is filtered out the blood free from these waste materials goes into the renal veins from where it goes into the heart through posterior vena cava. The fluid containing waste material is forced out of the glomerular capillaries in the bowman's capsule. The filtered out fluid is known as glomerular filtrate which contains sodium, potassium and chloride ions, glucose and amino acids along with urea, uric acid and a large amount of water.

              Bowmen's capsule leads into a long tubular structure into which the glomerular filtrate moves away. The tubular structure is convolued, twisted, folded and has U- turn before meeting the collecting duct. During the flow of glomerular filtrate in this long tube reabsorption of useful materials and secretion of certain substances takes place. The materials reabsorbed are glucose and amino acids sodium ion,  potassium ion and chloride ion, water etc. The fluid reaching the end of collecting duct is called urine. The urine is fluid and dissolved waste substances excreted by the kidneys. Human urine contains about 95% water and 5% nitrogenous substances (mostly urea and uric acid etc) and a few other substances. Finally the urine moves through the ureter and collects in the urinary bladder till thrown out of the body through urethra and urinary opening.