There are three amino acids that have basic side chains at neutral pH. ... For these amino acids, the protonated forms predominate at physiological pH (about 7). Two amino acids have acidic side chains at neutral pH. These are aspartic acid or aspartate (Asp) and glutamic acid or glutamate (Glu). Histidine is the most basic amino acid in the given compound. This can be attributed to the fact that the histidine contains the most number of a basic nitrogen atom. Normally, an amino acid produces a nearly neutral solution since the acid group and the basic amine group on the root amino acid neutralize each other in the zwitterion. If the amino acid structure contains two acid groups and one amine group, there is a net acid producing effect.

he main organs of the alimentary canal are:

• The Mouth and Oral cavity.
• Esophagus.: It is a muscular tube through which small bolus of food passes from the mouth to the stomach. It is sharply bent at the point at which it meets the stomach. This prevents the backward movement of food from the stomach into it. Food in the digestive tract moves by an involuntary movement of alternate contraction and relaxation of muscles called peristalsis.
• Stomach:

  It is a muscular bag which has three parts- cardiac part, fundus, and body.

• Cardiac part– It is so called because it is present close to the heart. The opening of the esophagus to the stomach is regulated by the cardiac sphincter.
• Fundus– It is dome-shaped and is usually filled with air.
• Body– This is the main part of the stomach. The opening of the stomach into the small intestine is regulated by the pyloric sphincter.
• Largeintestine.The small intestine leads into the large intestine which has three parts- Caecum, Colon, and Rectum.
• Caecum– It is a small sac-like structure at the point where the small intestine meets the large intestine.
• Colon– It is divided into four regions-  transverse colon,  sigmoid colon ascending colon and descending colon.
• Rectum– It opens into the ****.
• Small intestine.:It is the longest part of the alimentary canal and comprises three parts- Duodenum, Jejunum, and Ileum.
• Duodenum– It is C- shaped and receives the hepatopancreatic duct formed by the union of bile and pancreatic duct.
• Jejunum–  Middle part of small intestine with thick walls and more vasculature.
• Ileum– The lower part of the small intestine with thin walls and less vasculature.

• Mouth

The mouth is the opening through which the intake of food occurs.

• Oral cavity

The oral cavity has three parts –the palate, tongue, and teeth.

Palate -It forms the roof of the oral cavity. The anterior part is called hard palate and the posterior part is called soft palate.

Tongue -Tongue is a muscular and glandular structure attached to the base of the oral cavity. On the upper surface, it has a V-shaped furrow called sulcus terminalis. It divides the tongue into the anterior oral part and posterior pharyngeal part. Its upper surface also consists of tiny projections called lingual papillae. Lingual papillae are of three kinds in humans-

(i)Vallate or circumvallate papillae -have gustatory receptors to sense taste

(ii) Filiform papillae- smallest and contain touch receptors.

(iii) Fungi-form papillae- Rounded and mostly present at the tip of the tongue.

• Teeth

Humans are diphyodont i.e. they have two sets of teeth- milk or deciduous and permanent teeth. Here is the list of different types of teeth in humans with their functions.

The human digestive system consists of the alimentary canal and its associated glands. Food is taken into the body through the mouth.

Digestion in human beings starts in the mouth. The mouth contains teeth, tongue and salivary glands. The teeth cut the food into small pieces, chew and grind it. The tongue mixes the food with saliva. The salivary glands secrete a watery liquid called saliva.

The slightly digested food goes into the food pipe or oesophagus by peristalsis. No digestion of food takes place in the oesophagus.

The slightly digested food reaches the stomach through oesophagus for further digestion where it is broken down into smaller pieces. The inner lining of the stomach secretes gastric juice which includes mucus, hydrochloric acid and digestive juices. Mucus protects the lining of the stomach from hydrochloric acid. Hydrochloric acid makes the medium in the stomach acidic to facilitate the digestion of proteins. The digestive juices break down the protein into simpler substances. Then the partially digested food goes into the small intestine.

The small intestine is a very long and narrow tube where complete digestion of food takes place. It receives secretions of liver, pancreas and its own walls. Liver secretes liquid called bile which helps in the digestion of fats and converts them into small droplets. Pancreas secretes pancreatic juice which breaks down fats into fatty acids and glycerol. Pancreatic juice also breaks down carbohydrates and proteins into simpler forms. The intestinal juice secreted by the walls of small intestine breaks down the carbohydrates into glucose, proteins into amino acids. Thus, the food gets completely digested in small intestine.

Absorption: The digested food material passes into the blood vessels in the walls of small intestine. This process is called absorption. The inner walls of small intestine have millions of tiny, finger-like outgrowths called villi which increase the surface area for rapid absorption of digested food. Each villus has a network of blood vessels which absorbs the digested food materials into the blood flowing through them.

Assimilation: The blood carries the absorbed food materials to the cells in all the parts of the body where it is used for growth, energy and repair. This is called assimilation. Glucose breaks down utilizing oxygen to form carbon dioxide and water, and releases energy.

The undigested and unabsorbed food passes from the small intestine into large intestine. Most of the water is absorbed from the undigested food materials in the large intestine.

Egestion: The undigested food is temporarily stored in the last part of the large intestine called rectum and finally the semi-solid waste is passed out from the body through **** in the form of faeces. This is called egestion.

Teeth: Teeth break down the food into smaller pieces. There are four types of teeth in our mouth. They are:

1. Incisors: These are chisel shaped teeth at the front of the mouth and used for biting and cutting the food.
2. Canines: These are large and pointed teeth just behind the incisors and are used for piercing and tearing the food. 
3. Premolars: These are large teeth just behind the canines on each side and are used for chewing and grinding the food.
4. Molars: These are very large teeth present just behind the premolars and help for chewing and grinding the food.

• The human digestive system consists of the alimentary canal and the associated glands.

Alimentary canal 

• The alimentary canal begins with an anterior opening – the mouth, and it opens out posteriorly through the ****.
• The mouth leads to the buccal cavity or oral cavity, which has a number of teeth and a muscular tongue and each tooth is embedded in a socket of jaw bone with a type of attachment called as thecodont.
• A set of temporary milk or deciduous teeth is replaced by a set of permanent or adult teeth, and the type of dentition is called diphyodont.
• An adult human has 32 permanent teeth, which are of four different types
• incisors (I)
• canine (C)
• premolars (PM)
• and molars (M).
• Arrangement of teeth in each half of the upper and lower jaw in the order I, C, PM, M is represented by a dental formula which in human is 2123/2123.
• The tongue is a freely movable muscular organ attached to the floor of the oral cavity by the frenulum, and the upper surface of the tongue has small projections called papillae, some of which bear taste buds.
• The oesophagus and the trachea open into the pharynx.
• A cartilaginous flap called epiglottis prevents the entry of food into the glottis, which is the opening of the wind pipe.
• The oesophagus is a thin, long tube which extends posteriorly passing through the neck, thorax and diaphragm and leads to a ‘J’ shaped bag like structure called stomach.
• The stomach has three major parts
• a cardiac portion into which the oesophagus opens
• a fundic region
• a pyloric portion which opens into the first part of small intestine.
• Small intestine is distinguishable into three regions
• a ‘U’ shaped duodenum
• a long coiled middle portion jejunum
• a highly coiled ileum.
• The opening of the stomach into the duodenum is guarded by the pyloric sphincter.
• Ileum consists of
• caecum
• colon
•  
• Caecum is a small blind sac from which a vestigial organ called vermiform appendix
• The colon is divided into three parts
• an ascending
• a transverse
• a descending part.
• The descending part opens into the rectum which opens out through the ****.
• The wall of alimentary canal from oesophagus to rectum possesses four layers
• Serosa
• muscularis
• sub-mucosa
•  
• Serosa is the outermost layer and is made up of a thin mesothelium and some connective tissues.
• Muscularis is formed by smooth muscles usually arranged into an inner circular and an outer longitudinal layer.
• The submucosal layer is formed of loose connective tissues.
• Mucosa is the innermost layer which forms rugae in the stomach and small finger-like foldings called villi in the small intestine.
• The cells lining the villi produce numerous microscopic projections called microvilli giving a brush border appearance.
• Villi are supplied with a network of capillaries and a large lymph vessel called the lacteal.
• Mucosal epithelium has goblet cells which secrete mucus that help in lubrication.
• Mucosa forms gastric glands in the stomach crypts of Lieberkuhn in different parts of the alimentary canal.

Hydroponics is the technique of growing plants with their roots immersed in the nutrient solution without soil.
(a) It is useful in areas having infertile and dry soils.
(b) It is useful to cultivate plants in the areas deficient
in one or more nutrient.

• The metabolic pathway through which the electron passes from one carrier to another, is called the electron transport system (ETS).
• Electron transport system takes place in inner mitochondrial membrane.
• Electron transport chain comprises of the following:
• Complex I: NADH dehydrogenase
• Complex II: succinate dehydrogenase
• Complex III: cytochromes bc1
• Complex IV: cytochromes a-a₃
• Complex V: ATP synthase
• NADH₂ is oxidized by NADH dehydrogenase and electrons are then transferred to ubiquinone located in the inner mitochondrial membrane.
• FADH₂ is oxidized by succinate dehydrogenase and transferred electrons to ubiquinone.
• The reduced ubiquinone is then oxidized with transfer of electrons via cytochromes bc1 complex to cytochrome c.
• Cytochrome c is a small protein attached to the outer surface of the inner membrane and transfer electrons from complex III to complex IV.
• When electrons transferred from one carrier to another via complex I to complex IV, they are coupled to ATP synthesis of ATP from ADP and Pi.
• Oxygen plays a vital role in removing electrons and hydrogen ion and finally helps in the production of H₂

Glomerular Filtration Rate (GFR): The amount of the filtrate formed by the kidneys per minute is called glomerular filtration rate (GFR). GFR in a healthy individual is approximately 125 ml/minute, i.e., 180 litres per day. On an average, 1100-1200 ml of blood is filtered by the kidneys per minute which constitute roughly 1/5th of the blood pumped out by each ventricle of the heart in a minute.

Lacteals are the small lymphatic capillaries. Their function is to absorb fats and fat-soluble vitamins in the small intestine.

Apoplast is the space outside the plasma membrane consisting of intercellular spaces where the material diffuses freely. It does not involve protoplasm in the plant tissues but involves the non-living parts of the plant such as cell wall and intercellular spaces.

The pathways of ion and water created by symplast are known as the symplastic pathway. This pathway offers resistance to the flow of water since the selective plasma membrane of the root cells handles the intake of ion and water. Moreover, symplasty is affected by metabolic states of the root. The symplastic route occurs beyond the endodermis in plants with secondary growth.

Immobilization is the opposite of mineralization where the inorganic nutrients are taken up by soil microbes making them unavailable for plant uptake. Immobilization is the conversion of an element from an inorganic to organic form by microorganisms. ... Thus, under conditions of nutrient limitation, the microorganisms compete with plants for nutrient made available from mineralization, chemical weathering, and atmospheric deposition.

Total Lung Capacity: Total volume of air accommodated in the lungs at the end of a forced inspiration is called Total Lung Capacity. Total Lung Capacity = VC + RV = (ERV + TV + IRV) + RV.

There is an auto regulatory mechanism present in the kidney to regulate the glomerular filtration rate. This mechanism is carried out by juxta glomerular apparatus (JGA) which is a special sensitive region formed by cellular modification of the distal convoluted tubule and the different arteriole at the location of their contact. A fall in the GFR will activate the JG cells to release renin which converts the angiotensinogen in blood to angiotensin I and later into angiotensin II. The angiotensin II is a powerful vaso constrictor which increases the glomerular blood pressure and there by increase the GFR. The Angiotensin II also activates the adrenal cortex to release aldosteron which causes the reabsorption of Na+ and water from the distal parts of the tubule. This also results in the increase in blood pressure and GFR.

A nerve cell is like a receiver, transmitter and transmission line with the task of passing a signal along from its dendrites to the axon terminal bundle. ... This enhanced signal transmission is called saltatory conduction. Myelin insulates the axon to prevent leakage of the current as it travels down the axon. Nodes of Ranvier are gaps in the myelin along the axons; they contain sodium and potassium ion channels, allowing the action potential to travel quickly down the axon by jumping from one node to the next.

Digestion of fats:

Butter is a fat product and gets digested in the small intestine. The bile juice secreted by the liver contains bile salts that break down large fat globules into smaller globules, so as to increase their surface area for the action of lipase. This process is referred to as emulsification of fats.

After this, the pancreatic lipase present in the pancreatic juice and the intestinal lipase present in the intestinal juice hydrolyse the fat molecules into triglycerides, diglycerides, monoglycerides, and ultimately into glycerol and fatty acids.

FatsTriglycerides + Diglycerides

Diglycerides and monoglyceridesFatty acids + Glycerol

Absorption of fats:

Fat absorption is an active process. During fat digestion, fats are hydrolysed into fatty acids and glycerol. However, since these are water insoluble, they cannot be directly absorbed by the blood. Hence, they are first incorporated into small droplets called micelles and then transported into the villi of the intestinal mucosa.

They are then reformed into small microscopic particles called chylomicrons, which are small, protein-coated fat globules. These chylomicrons are transported to the lymph vessels in the villi. From the lymph vessels, the absorbed food is finally released into the blood stream and from the blood stream, to each and every cell of the body.