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PGA – Phosphoglyceric Acid. 

Ribulose-1-5-biphosphate, a 5-carbon compound is the acceptor of CO₂ in Calvin cycle.

Photophosphorylation : The process of formation of high-energy chemicals (ATP and NADPH). 

Cyclic photophosphorylation : Two photosystems work in series − First PSII and then PSI. These two photosystems are connected through an electron transport chain (Z. Scheme). Both ATP and NADPH + H⁺ are synthesised by this process. PSI and PSII are found in lamellae of grana, hence this process is carried here.

Non-cyclic photophosphorylation : Only PSI works, the electron circulates within the photosystem. It happens in the stroma lamellae (possible location) because in this region PSII and NADP rectase enzyme are absent. Hence only ATP molecules are synthesised. 

• Discovered by Hatch & Slack, so called as Hatch &Slack Pathway. 
• First stable product is 4- carbon compound (Oxaloacetic Acid) hence called C₄-cycle and plants having this cycle are called as C₄ plants. 
• C₄ plants have special kind of leaf anatomy called as “Kranz anatomy”.
• (Presence of two types of photosynthetic cells, i.e. mesophyll cells and bundle sheaths cells). 
• In C₄ plants (Maize, sugar cane etc.) both C₃ cycle (In bundle sheath cell chloroplasts) & C₄ cycle (In mesophyll cell chloroplasts) occurs. 

C₄ plants have special type of leaf anatomy, they tolerate higher temperatures. In this pathway, oxaloacetic acid (OAA) is the first stable product formed. It is 4 carbon atoms compound, hence called C₄ pathway (Hatch and Slack Cycle). 

The leaf has two types of cells : mesophyll cells and Bundle sheath cells (Kranz anatomy). Initially CO₂ is taken up by phosphoenol pyruvate (PEP) in mesophyll cells and changed to oxaloacetic acid (OAA) in the presence of PEP carboxylase. Oxaloacetate is reduced to maltate/asparate that reach into bundle sheath cells.

C₄ plants chemically fix carbon dioxide in the cells of the mesophyll by adding it to the three-carbon molecule phosphoenolpyruvate, a reaction catalyzed by an enzyme called PEP carboxylase and which creates the four-carbon organic acid, oxaloacetic acid. Oxaloacetic acid or malate synthesized by this process is then translocated to specialized bundle sheath cells where the enzyme, rubisco and other Calvin cycle enzymes are located and where CO₂ released by decarboxylation of the fourcarbon acids is fixed by rubisco activity to the three-carbon sugar 3 – phosphoglyceric acids.

The particularly large cells around the vascular bundles of the C₄ pathway plants are called bundle sheath cells, and the leaves which have such anatomy are said to have ‘Kranz1 anatomy. ‘Kranz’ means ‘wreath’ and is a reflection of the arrangement of cells. The bundle sheath cells may form several layers around the vascular bundles, they are characterized by having a large number of chloroplasts, thick walls impervious to gaseous exchange and no intercellular spaces.

Discovered by Melvin Calvin, hence called calvin cycle. 

First stable product is 3-carbon compound hence called C₃ cycle and plants having this pathway of CO₂ fixation are called as C₃ plants.

It occurs in following three steps

a. Carboxylation, in which CO₂ combines with primary acceptor called RUBP (ribulose 1,5 bisphosphate) in the presence of enzyme RUBISCO (Ribulose, 1.5 bisphosphate carboxylase oxygenase) to produce two molecules of PGA (Phosphoglyceric acid). 

b. Reduction, in which 2 molecules of PGA get reduced to 2 molecules of PGAL (Phosphoglyceraldehyde, triose sugar) using 2ATP and 2 NADPH. 

c. Regeneration, in which again primary acceptor (RUBP) is synthesized from PGAL & ATP.

C₄ plants avoid photorespiration and thus avoid the wastage of ATP. Thus there is more efficient utilization of the resources. This helps a C₄ plant to produce more food compared to a C₃ plant.

Antennae refers to all the pigments of the photosystem except the pigment molecule (Chl’a’) that forms the reaction centre.

Van Niel on his studies with purple and green sulphur bacteria doemonstrated that photosynthesis is a light dependent reaction in which hydrogen from an oxidisable compound reduces CO₂ to form sugar. 

2H₂A + CO₂ \(\overset{light}{\rightarrow}\) 2A + CH₂O 

In Green plants, HO is the hydrogen donor and is oxidised to O₂ In green sulphur bacteria, when H₂O instead of HO was used as hydrogen donor no O₂ was evolved. He inferred that O₂ evolved by green plants come from H₂O but not from CO₂.

The loss of vigour/fertility and productivity due to continuous inbreeding especially close inbreeding is called inbreeding depression.

(a) Sexual reproduction brings about variation in the offspring. 

(b) Since gamete formation is preceded by meiosis, genetic recombination occurring during crossing over (meiosis-I), leads to a great deal of variation in the DNA of gametes. 

(c) The organism has better chance of survival in a changing environment.

(i) In a C₃ plant, it takes place in the mesophyll cells. 

(ii) In a C₄ plant, calvin cycle takes place in the bundle sheath cells.

(a) The first carbon fixation product is PGA (3-carbon atom) in C₃ pathway, while it is oxaloacetic acid (4-carbon atom) in C₄ pathway. The C₄ pathway is more efficient than the C₃ pathway; in terms of making glucose.

(b) Both the photosystems are involved in non-cyclic photophosphorylation, while only PS I is functional in cyclic photophosphorylation. Non-cyclic photophosphorylation happens in the lamella of grana, while cyclic photophosphorylation occurs in the lamella of stroma. Both ATP and NADPH⁺H⁺ are synthesized in non-cyclic photophosphorylation, while only ATP is synthesized in cyclic photophosphorylation.

(c) Bundle sheath is present in C₄ leaves, while it is absent in C₃ leaves. The cells of C₄ leaves have a large number of chloroplasts, thick walls and no intercellular spaces.

Stone or insoluble mass of crystallised salts such as oxalates are called as renal calculi.

Selective reabsorption of glomerular filtrate takes place in the proximal convoluted tubule (PCT).

The correct answer is (B) Efferent arteriole forms peritubular network all around tubule.

To maintain hybrid characters (year after year in a desired plant), to avoid buying hybrid seeds every year (expensive seeds).

Detailed Answer

Farmers prefer apomictic seeds, when the hybrids are made into apomicts. It is because, in apomictic seeds, there is no segregation of characters in the hybrid progeny. Therefore, the farmers can keep on using the hybrid seeds to raise new crop year after year.

A- antigen binding site,

B- Variable region

c- constant region

D- light chain,

E- heavy chain (constant region),

F- disulphide bond

There are four polypeptide chains in each antibody molecule. Out of these four chains two are smaller and called light chains and the other two chains are longer and called heavy chains. It is because of this antibody molecule is represented as H₂L₂.

A—Antigen binding site 

D—Light chain 

E—Heavy chain 

F—Disulfide bridge.

When body encounters a pathogen for the first time produce a response called 1° response. 1° response is of low intensity. When body encounters the same pathogen subsequently then body elicits 2° response. 2° response is highly intensified. This is due to the fact that our body have memory of the first encounter.

Each antibody molecule has four polypeptide chains. The two smaller chains are called light chains while the two longer chains are called heavy chains. Therefore an antibody is represented as H₂L₂.

At high altitudes it is advised to take easy due to low oxygen availability. This may also cause altitude sickness. It is also advised to take rest because body compensates the low oxygen availability during rest by increasing RBC production and decreasing the binding capacity of haemoglobin, in turn increasing the breathing rate.

At high attitudes the availability of oxygen is low. Therefore, it is advised to take it easy and take rest during the initial period of high attitude trip because during this period of early rest the body compensates for the low O₂ availability by increasing RBC production and increasing the breathing rate.

Primary lymphoid organ is thymus. Secondary lymphoid organ is tonsils.

Each antibody molecule is made of the two heavy chains (H₂) and two light chains (L₂ ), hence represented as H₂ L₂

A:—Constant region of heavy chain,

B—Constant region of light chain,

C—Variable region of light and heavy chain

During changing weather, one is advised to avoid closed, crowded and air- conditioned placed like cinema halls, etc., because during this period the infectious agents are more humerous and prevalent to which we are more vulnerable.

Lymph nodes are small solid structures located at different points along the lymphatic system. Lymph nodes trap the microorganisms or other antigens, which happen to get into the lymph and tissue fluid. Antigens trapped in the lymph nodes are responsible for the activation of lymphocytes present there and cause the immune response.

The harmful alleles get eliminated from population over a period of time, yet sickle cell anaemia is persisting in human population because SCA is a harmful condition which is also a potential saviour from malaria.

Those with the benign sickle trait possess a resistance to malarial infection. The pathogen that causes the disease spends part of its cycle in the red blood cells and triggers an abnormal drop in oxygen levels in the cell. In carriers, this drop is sufficient to trigger the full sickle-cell reaction, which leads to infected cells being rapidly removed from circulation and strongly limiting the infection’s progress. These individuals have a great resistance to infection and have a greater chance of surviving outbreaks. This resistance to infection is the main reason the SCA allele and SCA disease still exist. It is found in greatest frequency in populations where malaria was and is still often a serious problem.

The harmful alleles get eliminated from population over a period of time, yet sickle cell anaemia is persisting in human population because SCA is a harmful condition which is also a potential saviour from malaria.

Those with the benign sickle trait possess a resistance to malarial infection. The pathogen that causes the disease spends part of its cycle in the red blood cells and triggers an abnormal drop in oxygen levels in the cell. In carriers, this drop is sufficient to trigger the full sickle-cell reaction, which leads to infected cells being rapidly removed from circulation and strongly limiting the infection’s progress. These individuals have a great resistance to infection and have a greater chance of surviving outbreaks. This resistance to infection is the main reason the SCA allele and SCA disease still exist. It is found in greatest frequency in populations where malaria was and often still is a serious problem.

The harmful alleles get eliminated from population over a period of time, yet sickle cell anaemia is persisting in human population because SCA is a harmful condition which is also a potential saviour from malaria.

Those with the benign sickle trait possess a resistance to malarial infection. The pathogen that causes the disease spends part of its cycle in the red blood cells and triggers an abnormal drop in oxygen levels in the cell. In carriers, this drop is sufficient to trigger the full sickle-cell reaction, which leads to infected cells being rapidly removed from circulation and strongly limiting the infection’s progress. These individuals have a great resistance to infection and have a greater chance of surviving outbreaks. This resistance to infection is the main reason the SCA allele and SCA disease still exist. It is found in greatest frequency in populations where malaria was and often still is a serious problem.

(a) Metastasis

1. The flavour in yogurt is due to acetaldehyde formation. 

2. Large holes in Swiss Cheese is due to more CO₂ production bypropionibacterium shermanii.

Yogurt, Paneer, Curd, Idli batter, Bread dough.

1. Prebiotics: Prebiotics are compounds in food (fibers) that induce the growth or activity of beneficial microorganisms. 

2. Probiotics: Probiotics are live microorganisms intended to provide health benefits when consumed,generally by improving or restoring the gut flora.

1. Swiss Cheese – Propionibacterium shermanii 

2. Bread dough – Saccharomyces cerevisiae

Beverages, antibiotics, organic acids, amino acids, vitamins, bio fuels, single cell protein, enzymes, steroids, vaccines, pharmaceutical drugs.

Antibiotic resistance occurs when bacteria develop the ability to defeat the drug designed to kill or inhibit their growth. It is one of the most acute threat to public health. Antibiotic resistance is accelerated by the misuse and over use of antibiotics, as well as poor infection prevention control. Antibiotics should be used only when prescribed by a certified health professional. When the bacteria become resistant, antibiotics cannot fight against them and the bacteria multiply. Narrow spectrum antibiotics are preferred over broad spectrum antibiotics. They effectively and accurately target specific pathogenic organisms and are less likely to cause resistance.

Broad-spectrum antibiotics act against a wide range of disease-causing bacteria. Narrowspectrum antibiotics are active against a selected group of bacterial types.

Correct Answer is: (d) ii and iv

1. Alexander Fleming 

2. Earnest Chain 

3. Howard Florey

Erythromycin, Chloromycetin, Neomycin, Kenamycin.

(b) R explains A

Though Tetracycline & Streptomycin are broad spectrum antibiotics, Tetracycline acts as a bacteriostatic antibiotic whereas streptomycin acts as bactericidal antibiotic against both gram positive and gram negative bacteria.

B) Cork cap and test tube moves in the opposite direction.

Poliomyelitis virus enters the body through mouth and nose.