Life Process

Human digestive tract starts right from our mouth

(The buccal cavity) and ends in the small intestine. The first enzyme that the food receives is the "Salivary amylase" in the buccal cavity released from the salivary glands. This enzyme acts on the complex sugars and converts them into their simpler form i.e. Glucose etc.

As the ventricular diastole (relaxation progress) the pressure in the ventricles decreases and blood from the systemic aorta and pulmonary aorta tries to return back, but due to the closer of "Semilunar valves" the back flow of blood is prevented. This also produces the second heart sound called the "Dub" sound.

Wall of alimentary canal consists of 4 concentric coats, from outside to inside these are,

a) Serosa (visceral peritoneum)

b) Muscularis ( muscular coat)

c) submucosa

d) mucosa

The peristaltic movement of these inner walls allows the movement of food.

Transpiration is the process of loss of water from plants from small openings they possess like stomata, trichomes, cuticular openings etc.

This happens in order to maintain the homeostasis of plants under high temperature. Also, it occurs during day time only when stomata are open.

The major toxic waste that reaches kidneys through blood is the nitrogenous waste in the form of "Urea" and "Uric acid". Urea is highly water soluble and is mostly excreted via. Urine, while uric acid is insoluble in water, is mostly excreted in solid form.

Peristalsis is simply a series of contraction and relaxation of muscles in a specific manner that helps in the movement of food through the digestive tract. It comprises of the relaxation of smooth muscles, then their contraction behind the already chewed bolus preventing it from moving backward and then further longitudinal contraction to push it forward.

In the Alimentary canal, "Plexus of Auerbach" of Serosa - starts peristalsis.

While, "Plexus of Meissner" - stops peristalsis.

As the food reaches the small intestine, it receives the Bile juice secretion from the liver. The salts present in this juice are responsible for breaking the bigger fat droplets into smaller ones and this process is called "Emulsification" of fats.

Fats are nothing but triglycerides and glycerol. The salts of Bile i.e., Sodium glycocholate and Sodium taurocholate break large fat droplets into smaller one and thus pancreatic lipase can easily break these smaller triglycerides into fatty acids.

In higher plants, "Xylem" and "phloem" comprises the transport system. The basic function of these components is,

Xylem:- In xylem tissue, vessels and tracheids of the roots, stems and leaves are interconnected to form a continuous system of water-conducting
channels reaching all parts of the plant. At the roots, cells in contact with the soil actively take up ions. This creates a difference in the
concentration of these ions between the root and the soil. Water, therefore, moves into the root from the soil to eliminate this difference. This means
that there is a steady movement of water into root xylem, creating a column of water that is steadily pushed upwards

Phloem:- transports amino acids and other substances. These substances are specially delivered to the storage organs of roots, fruits and seeds and
to growing organs. The translocation of food and other substances takes place in the sieve tubes with the help of adjacent companion cells both
in upward and downward directions. In pholem translocation is done with the utilisation of energy. Material like sucrose is transferred into phloem tissue using
energy from ATP. This increases the osmotic pressure of the tissue causing water to move into it. This pressure moves the material in the
phloem to tissues which have less pressure.

Gastric glands are present in the mucosa lining of the stomach wall. They are present in the fundus, cardiac and pyloric regions of the stomach. About 2-3 liters of Gastric juice is secreted per day and its secretion is controlled by the thought of food, smell, and chewing.

These glands are,

a) Parietal or oxyntic cells:- secrete HCL that provides the acidic pH for the action of pepsin and rennin. Also, they secrete an" intrinsic factor" that helps in the absorption of vitamin B12.

b) Peptic cells or chief cells or zymogenic cells:- they secrete pepsinogen and prorennin which are zymogenic (inactive) forms which digest proteins.

c) Mucus neck cells or goblet cells:- they secrete Mucus which contains mucin which protects the stomach wall from the acidic action of HCL.

d) G-cells: - these secrete a hormone called "Gastrin" that controls the amount of secretion of Gastric juices.

Trachea is an 11 cm long and hollow tube that opens into laryngopharynx through its opening called "glottis).

The inner wall of Trachea contains Mucus glands and cilia, this Mucus keeps the lumen of Trachea moist and cilia pushes the Mucus and dust away from lungs.

b) Trachea has" C-shaped" cartilaginous rings on its outer wall. These rings are 16-18 in number and prevent the collapsing of the Trachea when there is less air in it.

Diaphragm separates the "thoracic cavity" from the "abdominal cavity. "During inspiration, the "phrenic" muscles of Diaphragm contracts and move downwards due to which thoracic cavity also move downwards and air can enter the lungs. Also, lungs rest on Diaphragm, while during expiration, phrenic muscles of Diaphragm relaxes and pushes the thoracic cavity upwards and causes the lungs to release out the air. If Diaphragm gets ruptured, the downward push on abdominal cavity will not be there, thus lungs will not be able to expand and the breathing process would be greatly hindered which may even lead to the death of the person.

a) Autotrophic nutrition - iv) Green plants

Explanation:- Autotrophs are those who can prepare their own food by using carbon di oxide as the sole carbon source and do not depend on other organisms for their nutrition. Green plants posses chrolophyll that provides them the ability to produce their own food by the process of photosynthesis.

b) Heterotrophic nutrition - iii) Deer

Explanation:- Heterotrophs are those who can not prepare their own food and depends upon autotrophs for their nutritional requirements. Deer depends upon grass for its food and hence is a Heterotroph.

c) Parasitic nutrition - I) Leech

Explanation:- Parasite is an organism that depends upon the host for its nutrition i.e. it solely depends upon the host for its food and can not survive without it. Leech depends upon the blood it sucks from the host and thus is a parasite.

d) Digestion in food vacuole- ii) Paramecium

Explanation:- Paramecium is a protozoa. As the food enters its mouth, it forms a vacuole in the cytoplasm and travels through the cell. Enzymes from cytoplasm enter the vacuole to digest the food and after digestion, vacuole shrink leaving the nutrients in the cytoplasm. When vacoule reaches the anal pore, it ruptures, releasing the waste to the exterior.

Transpiration occurs in plants during the day time when temperature is high. It is basically the loss of water from plants through minute openings plants posses like stomata, cuticular openings, trichomes etc.

● Transpiration helps in maintaining the basic thermostasis of plants which is important the metabolic processes to occur naturally.

● Also, it creates the negative pressure gradient, which is responsible for absorbing water and minerals from the soil with the help of cohesive and adhesive forces.

Photosynthesis.

It is the process by which plants use simple carbon source to form complex sugars in the presence of sunlight and water. The chemical energy is generated in the form of ATP which is further used in other metabolic processes.

Autotrophs.

Autotrophs are those which can prepare their own food and do not depend on any other organism for their nutritional requirements. Eg:- All green plants.

Chloroplast

Chloroplast posses membranous structures called "Thylakoids membrane" inside it.

Photosynthesis takes place in it because they possess the pigment called "chlorophyll" which traps the light energy and helps in its conversion to other food materials.

Guard cells.

Stomatal opening and closing is controlled by guard cells, this happens by their swelling and shrinking. When enough water is present inside the guard cells, they become turgid and they swell in this condition the stomatal pore is open. While when water moves out of them, these cells shrink and the stomatal pore is closed.

Heterotrophs

Heterotrophs are those organisms that depend upon another organism for their nutritional requirements since they can not prepare their own food. E.g.- animals, human etc.

Pepsin

It is secreted from the peptic cells of Gastric Glands. Pepsin acts on the proteins in the food and breaks them down into smaller forms that are processes and peptones(peptides).

Alveoli are the site of gaseous exchange. The number of alveoli in both the lungs is about 75 crores which have a surface area of About 100 square meters more than the area of a tennis court. The diffusion membrane is made of 3 layers,

● The thin simple squamous epithelium of alveoli

● The endothelium of pulmonary capillaries

● And the basement membrane in between them.

Combines thickness is less than 1 mm, this much thickness is essential for the easy exchange of gases.

● Excess water is removed by the process of transpiration.

● Some of the intracellular waste may get stored in the vacuole or in the leaves which later on are shed.

● Resins and gum are stored in specific resin vacuole or also in xylem.

● Salts and some other by products move out of the stomata by the process of diffusion.

● Dead bark is the dead phleom cells that later act as protective covering also called the "rhytidome".

Diffusion is comparatively a slow process when the metabolism of breathing is taken into consideration. The transfer and diffusion of gases occur within a fraction of seconds. Also sometimes at the cellular level, gases have to be exchanged against the concentration gradient where Diffusion cannot occur.

Plus multicellular organisms have specific locations defined for the Diffusion, those location (alveoli in humans) are not in direct contact with environment hence, Diffusion can not meet oxygen requirements of multicellular organisms.

Blood is a connective tissue. It consists of a fluid matrix, plasma and formed elements.

1.) Blood plasma:- Constitutes 55% of blood, it is pale yellow in color, slightly alkaline and viscous fluid. It consists of about 90% water, 1% inorganic salts in solution and 7-8% proteins in colloidal state. Remaining are gases, cholesterol and waste materials.

2.) Formed elements:- Blood corpuscles are known as formed elements. They are produced in the red bone marrow. These include a) Red blood cells:- They are round, unnucleate, membrane bound cells that carry pigment haemoglobin. Healthy man containa 25 trillion RBCs . Cell organelles are present in mature RBCs. The pigment "Haemoglobin" binds to oxygen and oxygen is then transported throughout the body. Average life spa of RBCs is120 days.

b) White Blood cells:- They are colorless because they lack haemoglobin. They are nucleated, with cell organelles, have ameboid activity. They are also called as "leucocytes". WBCs further comprise of

"Granulocytes and Agranulocytes". WBC's are the main defense system of our body. Further WBCs include Neutrophils, Basophils, Eosinophils, Monocytes, and Lymphocytes.

3) Blood Platelets:- Also called as " Thrombocytes". They are uninucleate, colorless and lack hemoglobin. Their number varies between 150000-350000. The life span of platelets is 3-7 days and they are responsible for clotting.

In humans, Urea is the major nitrogenous waste generated in human beings. Urea is formed mainly in the liver and is released into the blood stream and removed by the kidneys in the urine.

Urea is formed in the liver by a cycle called as "Urea cycle" or "Ornithine cycle" or "Kreb Henseleit cycle". Ammino acids not needed are deaminated by an enzyme called " Oxidase" and ammonia is generated. Ammonia being toxic gets converted into Urea. 3 ammino acids that participate in the cycle are,

a) Ornithine combines with NH3 and carbon di-oxide to form citrulline.

b) Citrulline combines with NH3 to form arginine.

c) Arginine then decomposes to form urea and ornithine.

Ornithine can then be sent again in urea cycle.

Alimentary canal is also called as the digestive tract. It is the pathway by which food enters the body and solid wastes are expelled from the body. The human alimentary canal has the following main parts:

● Mouth: Alimentary canal starts from the mouth and ends in the anus. The mouth opens into a chamber or cavity called buckle cavity. The buckle cavity contains teeth, tongue and salivary glands. The teeth cut the food into small pieces, chew and grind it. The tongue has taste receptors which sense the taste of the food we eat. Salivary glands secrete (release) saliva which is mucus-like fluid, to help in swallowing the food.

● Oesophagus (food pipe): Buckle cavity opens into pharynx which leads to a long tube called oesophagus. It is present behind the windpipe (trachea) and heart, and in front of the spine. The walls are highly muscular. Digestion does not occur in the food pipe. When we swallow food, the walls of the oesophagus squeeze together (contract). It carries the food down into the stomach.

● Stomach: Stomach is a bag-like organ. It receives food from the food pipe. Highly muscular walls of the stomach help in churning the food. It secretes acids and enzymes that help in digesting the food.

● Small intestine: It is a highly coiled tube-like structure. The small intestine is longer than the large intestine but its lumen is smaller than that of the large intestine. The small intestine is divided into three parts, viz. duodenum, jejunum and ileum. In humans, the small intestine is the site of the complete digestion of food like carbohydrates, proteins, and fats. Its job is to absorb most of the nutrients from what we eat and drink.

● Large Intestine: Undigested food goes into the large intestine. Anus is the opening at the end of the alimentary canal through which undigested food is thrown out. It is the last part of the digestive system in vertebrates. Water is absorbed here and the remaining waste material is stored as feces before being removed by defecation.

The ventricles are located on the posterior end of the heart beneath their corresponding atrium. The right ventricle receives deoxygenated blood from the right atria and pumps it through the pulmonary vein and into pulmonary circulation, which goes into the lungs for gas exchange.

The pulmonary arteries carry deoxygenated blood from the right ventricle into the alveolar capillaries of the lungs to unload carbon dioxide and take up oxygen. These are the only arteries that carry deoxygenated blood and are considered arteries because they carry blood away from the heart. The short, wide vessel branches into the left and right pulmonary arteries that deliver deoxygenated blood to the respective lungs. Blood first passes through the pulmonary valve as it is ejected into the pulmonary arteries.

The inferior vena cava is the largest vein in the body and carries deoxygenated blood from the lower half of the body into the heart. The left and right common iliac veins converge to form the inferior vena cava at its lowest point. The inferior vena cava begins posterior to the abdominal cavity and travels to the heart next to the abdominal aorta. Along the way up the body from the iliac veins, the renal and suprarenal veins (kidney and adrenal glands), lumbar veins (from the back), and hepatic veins (from the liver) all drain into the inferior vena cava.

● In the Right Side

Blood flows from your right atrium into your right ventricle through the open tricuspid valve. When the ventricles are full, the tricuspid valve shuts. This prevents blood from flowing backward into the atria while the ventricles contract.

● In the Left Side

Blood flows from your left atrium into your left ventricle through the open mitral valve. When the ventricles are full, the mitral valve shuts. This prevents blood from flowing backward into the atria while the ventricles contract.

Also, the aortic valve closes quickly to prevent blood from flowing back into the left ventricle, which is already filling up with new blood. Blood leaves the heart through the aortic valve, into the aorta, and to the body. This pattern is repeated, causing blood to flow continuously to the heart, lungs, and body.

Amoeba is a unicellular organism found in fresh water. Amoebas eat algae, bacteria, plant cells, and microscopic protozoa and metazoan – some amoebas are parasites. They eat by surrounding tiny particles of food with pseudo pods, forming a bubble-like food vacuole. The food vacuole digests the food. Wastes and excess water are transported outside the cell by contractile vacuoles. In amoeba carbon dioxide and ammonia are the main waster materials. These waste materials are excreted out by the process of diffusion through the general body surface. In amoeba, no excretory organs are present so contractile vacuoles function as an excretory unit. The waste materials present in the cytoplasm of amoeba enters the contractile vacuole. Then the contractile vacuole moves close to the plasma membrane, come in contact with the plasma membrane and burst to release its contents in the surrounding.

Explanation: The waste material carbon dioxide is removed by the process of diffusion though the cell membrane and the nitrogenous waste mainly ammonia is excreted with the help of the contractile vacuole. Specific excretory organs are absent in unicellular organisms like an amoeba. These organisms remove waste products by simple diffusion from the body surface into the surrounding water. Amoebas possess osmoregulatory (osmotic pressure) organelle called contractile vacuole. This collects water and waste from the body, swells up, reaches the surface and bursts to release its content to outside. The main excretion takes place through a body surface by the process of osmosis. Thus, waste products are exceeding in amoeba.

Ultra filtration is a process in the kidney by which urea, salt, water, and glucose etc. is extracted from the blood. The blood flows through the glomerulus under great pressure which is much greater than in the capillaries elsewhere. The reason for this greater pressure is that the efferent arteriole is narrower than the efferent arteriole. This high pressure causes the liquid part of the blood to filter out from the glomerulus into the renal tubule. This filtration under extraordinary force is called ultra filtration.

The mechanism of occurrence:

● When blood passes through the top of the nephron, it enters a structure called the glomerulus (Bowman’s capsule) which is a network of tiny capillaries.

● This causes the pressure to increase and fluid is forced through the "sieve-like" walls of the vessels into the Bowman's capsule. This fluid is called the filtrate.

● Blood cells and larger proteins do not pass through the capillaries as they are too large and so are not found in the filtrate.

● A large proportion what enters the filtrate is valuable to the body and so needs to be reabsorbed into the blood by the process of selective re-absorption.

Explanation: Blood flows into the glomerulus from the afferent arteriole, which is wider in diameter than efferent article. This difference in diameter ensures the blood in the capillaries is under increased pressure. The high-pressure forces liquid and small molecules out into the Bowman’s capsule. The endothelium of the capillaries has small gaps to ensure substances can pass through. The basement membrane is made of glycoprotein’s which ensure large proteins cannot pass through-it is a selective barrier. Epithelial cells of the Bowman’s capsule called podocytes to have finger-like projections which ensures fluid can pass into the lumen of Bowman’s capsule. Once the blood is filtered in this way only blood cells and large plasma proteins remains in the blood and continue into the proximal convoluted tubule.

Urine formation takes place in the kidneys. This formed urine is then transported to the urinary bladder by the ureters, where it is stored. This stored urine is then passed out of the body by an opening in a muscular tube-like structure, called urethra.

The process of urine formation is given below in the diagram:

(a) - Glomerular filtration:
Blood containing useful substances (glucose, amino acids, vitamins, hormones, electrolytes ) and harmful substances (urea, uric acids, creatinine, ions, etc.) reaches the kidneys for filtration. This takes place through the semipermeable walls of the glomerular capillaries and Bowman’s capsule.

(b) - Selective reabsorption:
Wastes dissolved in water is filtered out as urine in the kidneys.

(c) - Tubular secretion:
Ureters carry urine to the urinary bladder.

Urine stored in the urinary bladder is passed out through the urinary opening at the end of the urethra.

(a) During the metabolism of glucose, there could be 2 possible conditions. Since we know that during the electron transport chain occurring in mitochondria, oxygen is the ultimate electron acceptor.

So the 2 conditions can be defined as aerobic(in presence of oxygen) and anaerobic(in the absence of oxygen) .

Under Aerobic conditions:- when glucose is broken into pyruvate molecules in glycolysis, pyruvate molecules further enters the Kreb cycle and overall 36 ATP are generated.

Under Anaerobic conditions :-Since here oxygen is not present, thus there is no electron acceptor at the end of electron transport chain, thus the pyruvate molecules generated undergo fermentation and alcohol is produced as an end product(in microorganisms) while lactic acid is the end product in muscle cells and only 2 AT are generated.

(b) The main difference between aerobic and anaerobic respiration is that aerobic needs oxygen to supply the body with ATP energy. But, anaerobic respiration does not require oxygen in order to provide energy.

a) Phloem - ii) Translocation of food

There are mainly 2 transport mechanisms plants possess, xylem that carries water and minerals and phloem that carries food.

Translocation of food means carrying the food from the location at which it is produced(source) to the location where it is needed(sink) I.e. from leaves to the other cells of plants.

b) Nephron - i) Excretion

Nephrons are the basic and functional units of kidneys that take part in blood filtration and removal of waste from it.

c) Veins - iv) Deoxygenated blood

This is because deoxygenated blood is at low pressure; also the walls of the veins are thin compared to the arteries that carry oxygenated blood.

d) Platelets – iii) clotting of blood

Whenever there is a wound or blood loss from our body platelets are the first that reach the wounded area and get deposited there. After sometime proteins like fibrin, fibrinogen also reaches there and the wound to prevent blood loss.

Depending on the conditions, the breakdown of the pathway of energy production varies.

i) In presence of oxygen,

In the presence of oxygen-glucose undergoes glycolysis, each glucose molecule produces 2 molecules of pyruvate and this pyruvate enters the citric acid cycle or the kerb cycle and at the end of it, 36 ATP are generated.

ii) In the absence of oxygen, (muscle cells)

In the absence of oxygen, which is the ultimate electron acceptor in the electron transport chain occurring in mitochondria, the pyruvate molecules generated are converted into lactic acid and then ATP is produced. Under this condition, 1 glucose molecule generates only 2 ATPs.

iii) In the absence of oxygen, (microorganisms)

Under this condition, the end products are not lactic acid but ethyl alcohol and this process are also called as fermentation. This property of microorganisms is exploited at an industrial level also.