The kidneys serve several essential regulatory roles. They are essential in the regulation of electrolytes, maintenance of acid-base balance, and regulation of blood pressure. They serve the body by filtering blood to remove wastes that are diverted to the urinary bladder for excretion. The kidneys excrete wastes such as urea and ammonium, and are also responsible for the reabsorption of water, glucose, and amino acids. Furthermore, the kidneys also produce hormones, including calcitriol, erythropoietin, and the enzyme renin.

Stomata are small pores present in the epidermal cells of leaves in plants. Stomata are open during the day and close during night.Stomata take in carbon dioxide required for the photosynthetic activity during the day. They give out excess water released in the process of respiration during night along with carbon dioxide. Opening and closing of stomata is controlled by concentration of solutes in the guard cell. Mechanism of opening and closing of stomata Opening of stomata: Solutes from neighbouring epidermal and mesophyll cells enter the guard cells lowering its osmotic potential and water potential. This lowered water potential and osmotic potential will allow movement of water into guard cells from neighbouring cells. Guard cells become turgid due to water accumulation in them which results in the opening of the guard cells.  Closing of stomata: As the somata open the solute concentration is reduced. This makes the water from the guard cells to move away into neighbouring cells. Now, guard cells becom flaccid with no water. They collapse against each other and result in the closing of stomata. 

Mitochondria produce ATP through process of cellular respiration—specifically, aerobic respiration, which requires oxygen. The citric acid cycle, or Krebs cycle, takes place in the mitochondria. This cycle involves the oxidation of pyruvate, which comes from glucose, to form the molecule acetyl-CoA. Acetyl-CoA is in turn oxidized and ATP is produced.

The citric acid cycle reduces nicotinamide adenine dinucleotide (NAD+) to NADH. NADH is then used in the process of oxidative phosphorylation, which also takes place in the mitochondria. Electrons from NADH travel through protein complexes that are embedded in the inner membrane of the mitochondria. This set of proteins is called an electron transport chain. Energy from the electron transport chain is then used to transport proteins back across the membrane, which power ATP synthase to form ATP.

The digestion of proteins begins in the stomach and is completed in the small intestine. The enzymes that act on proteins are known as proteases.

Digestion in the stomach: The digestive juice secreted in the gastric glands present on the stomach walls is called gastric juice. The main components of gastric juice are HCl, pepsinogen, and rennin. The food that enters the stomach becomes acidic on mixing with this gastric juice.

The acidic medium converts inactive pepsinogen into active pepsin. The active pepsin then converts proteins into proteases and peptides.

Proteins  {tex}\begin{array}{l}\xrightarrow{Pep\sin}\\\end{array}{/tex} Proteoses + Peptides

The enzyme rennin plays an important role in the coagulation of milk.

Digestion in the small intestine: The food from the stomach is acted upon by three juices present in the small intestine – pancreatic juice and intestinal juice (known as succus entericus).

Action of pancreatic juice

Pancreatic juice contains a variety of inactive enzymes such as trypsinogen, chymotrypsinogen, and carboxypeptidases. The enzymes are present in an inactivated state. The enzyme enterokinase secreted by the intestinal mucosa activates trypsinogen into trypsin.

Trypsinogen{tex}\begin{array}{l}\xrightarrow{\;Enterokinase}\\\end{array}{/tex}Trypsin + Inactive peptide

The activated trypsin then activates the other enzymes of pancreatic juice.

Chymotrypsinogen is a proteolytic enzyme that breaks down proteins into peptides.

Chymotrypsinogen {tex}\begin{array}{l}\xrightarrow{Tryp\sin}\\\end{array}{/tex} Chymotrypsin

Proteins{tex}\begin{array}{l}\xrightarrow{Chymotryp\sin}\\\end{array}{/tex} Peptides

Carboxypeptidases act on the carboxyl end of the peptide chain and help in releasing the last amino acids.

Peptides{tex}\begin{array}{l}\xrightarrow{\;Carboxypeptidase}\\\end{array}{/tex}Smaller peptide chain + Amino acids

Action of bile juice

Bile juice has bile salts such as bilirubin and biliverdin which break down large, fat globules into smaller globules so that pancreatic enzymes can easily act on them. This process is known as emulsification of fats. Bile juice also makes the medium alkaline and activates lipase. Lipase then breaks down fats into diglycerides and monoglycerides.

Action of intestinal juice

Intestinal juice contains a variety of enzymes. Pancreatic amylase digests polysaccharides into disaccharides. Disaccharidases such as maltase, lactase, sucrase, etc., further digest the disaccharides.

The proteases hydrolyse peptides into dipeptides and finally into amino acids.

 {tex}\begin{array}{l}\xrightarrow{dipeptides}\\\end{array}{/tex} Amino acids

Pancreatic lipase breaks down fats into diglycerides and monoglycerides.

The nucleases break down nucleic acids into nucleotides and nucleosides.

Abscisic acid is known as the stress hormone because of the following reasons :
1. It helps plant to cope with adverse environmental conditions or stresses. 
2. It causes temporary closure of stomata due to which there is reduction in the rate of transpiration. Therefore, it acts as antitranspirant and reduces water loss.
3. It acts as a general growth inhibtor and inhibitor of plant metabolism.
4. It inhibits seed germination.

The lingual tonsils are two small mounds of lymphatic tissue located at the back of the base of the tongue, one on either side. They are composed of lymphatic tissue that functions to assist the immune system in the production of antibodies in response to invading pathogenic bacteria or viruses.

To produce the desired end-product ammonia, the hydrogen is then catalytically reacted with nitrogen (derived from process air) to form anhydrous liquid ammonia. This step is known as the ammonia synthesis loop (also referred to as the Haber-Bosch process): 3H2 + N2 → 2NH. Due to the comparatively low price, high availability, easy processing, lifespan and activity, iron was ultimately chosen as catalyst. The production of for example 1800 tons ammonia per day requires a gas pressure of at least 130 bar, temperatures of 400 to 500 °C and a reactor volume of at least 100 m³.

Re-absorption: As the filtrate flows along the tubule useful substances such as glucose, amino acids, salts and water are selectively re-absorbed into the blood by capillaries surrounding the nephron tubule.
The amount of water re-absorbed depends on the need of the body and also on the amount of wastes to be excreted.

1. Storage Leaves: Some plants of xerophytic habitats and members of the family Crassulaceae generally have highly thickened and succulent leaves with water storage tissue. These leaves have large parenchymatous cells with big central vacuole filled with hydrophilic colloid. This kind of adaptation helps plants to conserve very limited supply of water and resist desiccation (drying up).

2. Leaf Tendrils: In weak- stemmed plants, leaf or a part of leaf gets modified into green thread­like structures called tendrils which help in climbing around the support.

3. Leaflet Hooks: In Bignonia unguiscati the three terminal leaflets of leaf get modified into claw like hooks which help in climbing .

4. Leaf Roots: In case of Salvinia three leaves are present at one node. Out of these two leaves are normal and third gets modified into adventitious roots which help in floating over the surface of water

The algal component of the lichen is called phycobiont and fungal component is known as mycobiont. Phycobiont prepare food for fungi and mycobiont provides shelter and absorb mineral nutrients and water for its partner.

The ultrastructure of the phycobionts is similar to that of free-living algae. The mycobionts displayed structural differences in their walls which apparently are unrecorded for fungus hyphae, resulting in a striking polymorphism of the hyphae.

Abscisic acid is called stress hormones as it induces various responses in plants against stress conditions.

It increases the tolerance of plants toward various stresses. It induces the closure of the stomata during water stress. It promotes seed dormancy and ensures seed germination during favourable conditions. It helps seeds withstand desiccation. It also helps in inducing dormancy in plants at the end of the growing season and promotes abscission of leaves, fruits, and flowers.

Brassicaceae or Cruciferae is a medium-sized and economically important family of flowering plants commonly known as the mustards, the crucifers, or the cabbage family. Most are herbaceous plants, some shrubs, with simple, although sometimes deeply incised, alternatingly set leaves without stipules or in leaf rosettes, with terminal inflorescences without bracts, containing flowers with four free sepals, four free alternating petals, two short and four longer free stamens, and a fruit with seeds in rows, divided by a thin wall (or septum).

When fatty acids are found esterified with glycerol, they are called glycerides. Presence of three esterified bonds makes them triglycerides.

In this figure, the left side is composed of glyceride. The right side is composed of palmitic acid, ocleic acid and alpha-linolenic acid; from top to bottom.

Glycosidic bond is the bond that joins the monosaccharide units in a polysaccharide chain. the bond is formed between two adjacent monosaccharide units and it involves dehydration.   When a base (Purine or pyrimidine) is attached to D-ribose or deoxyribose, is formed nucleoside.A nitrogen atom at 9th position of Purine base and nitrogen atom at 1st position of pyrimidine base is linked to carbon 1st position of deoxyribose or ribose by N-glycosidic linkage.                           

The transport of food from the leaves to other parts of the plant is called translocation. Phloem tissue transports the food from the leaves to the other parts of the plant. The movement of food in phloem takes place by utilising energy. The sugar made in the leaves is loaded into the sieve tubes of phloem by using ATP. Water enters the sieve tube containing sugar which causes high pressure and pushes the food to all the parts of the plant having low pressure. This is how the food is transported according to the needs of the plant.