Category: Biology Second Paper

The system in the male body that produces, stores, transports and expels sperm is called the ejaculatory system. Different parts of human reproductive system are-
1. Testis: The main organ of the reproductive system is the testis. There are two hanging scrotums or scrotums at the thigh joint. The left scrotum is larger and the right smaller. The testicles are located inside the scrotum. Each testicle is oval and partially flattened. Its length is 2 inches and weight is 10-12 grams.
Each testicle is covered by 3 integuments. Tunica vaginalis, tunica albuginea and tunica vasculosa testis. The outer layer is the tunica vaginalis, the middle layer is the tunica albuginea and the inner layer is the tunica vasculosa.
Each testicle divides into 250 cells or segments. Each segment contains 1-4 patchy seminiferous tubules. Each testicle contains about 1000 seminiferous tubules. A seminiferous tubule is about 500 mm long.
Many seminiferous tubules join together to form a straight duct. The straight ducts join to form the reti testis. The reti testes join together to form the vas deferens or vasa efferentia.
Function of Testis
(i) Produces sperm.
(ii) Secretes the hormone testosterone.
2. Epididymis: The seminiferous tubules or vasa efferentia of each testicle combine to form the epididymis. It is located at the posterior end of the scrotum and is a coiled duct. Its length is 4-6 meters. Its tail portion is straight and meets the vas deferens.
Function of Epididymis
(i) It separates liquid and solid waste from sperm.
(ii) It increases fertility.
(iii) It stores sperm.
(iv) It keeps the sperm fresh by secreting nutrients.
3. Vas deferens: The tube extending from the end of the epididymis to the root of the urinary bladder is called the vas deferens. It is 40-50 cm long. It forms the ampulla after crossing the urethra.
Function of Vas deferens
(i) It transports sperm.
(ii) It stores sperm.
4. Seminal vesicle: The end of the spermatic cord swells and forms a small, long, muscular and curly bag like a finger is called seminal vesicle or sperm. It produces seminal fluid of which 70% constitutes semen.
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(i) It produces cement.
(ii) secretes copious amounts of mucus to produce sperm or semen.
(iii) It produces fructose to nourish the sperm.
5. Ejaculatory duct: The short duct formed by sperm and seminal vesicles is called ejaculatory duct. It is 19 mm long and 0.3 mm in diameter.
Function: It transports the sperm to the urethra.
6. Urethra: A common tube of the excretory and reproductive system is the urethra. It is 20 cm long. It opens at the apex of the penis.
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(i) It increases the volume of semen by secreting alkaline fluid.
(ii) It preserves the spermatozoa by mitigating the acidic environment.
(iii) It provides nutrition to spermatozoa.
7. External genitalia
(i) Scotum: Two scrotums are suspended between the two thighs. The fluid in the scrotum is called a hydrocele. It maintains a favorable temperature for sperm production. Protects testicles from stress.
(ii) Penis: The soft and muscular organ through which the urethra opens to the outside is called the penis. The base of the penis is called the glans penis, the hanging part is called the glans penis, the red umbrella-like tip is called the glans penis and the tip or foreskin is called the prepuce. Muslims and Jews had their foreskins cut off. The penis is made up of elastic muscles called corpora cavernosa and corpora spongiosum. It is stiff and straight when excited.
8. Reproductive gland
(i) Prostate gland: It is a pear shaped gland. Consists of two parts. base and top. Its wall is composed of muscular and glandular cells. Glandular secretions are released into the urethra.
Work:
* It increases the volume of semen by secreting alkaline fluid.
* It keeps the sperm alive by soothing the acidic environment.
(ii) Bulbourethral of Cowper’s gland: On either side of the urethra there are two pea-like Cowper’s glands. They join the urethra.
Action: It secretes a slippery mucous substance during intercourse and makes the vagina slippery.

The process in which organisms create offspring with their own nature and shape to preserve the existence of the species is called reproduction. The system through which reproduction takes place is called reproductive system. The reproductive organs of the human body are collectively called the reproductive system. Humans are unisexual animals. Male reproductive system and female reproductive system exist in male body.

Fluid-Mosaic Model of Plasma Membrane
1. Phospholipids: There are five types of phospholipids in the cell membrane. Lecithin, cephalin, glycolipid, glycophosphotide and phosphotidic acid. Phospholipids are arranged in two layers. Each layer is composed of numerous lipid molecules. Each lipid molecule has two parts. head and tail The large outer part is called the head. It is spherical or oval and composed of phosphates. It is polar and hydrophilic. The two filament-like parts attached to the head are called tails. It is composed of fatty acids. The tail is non-polar and hydrophobic. Between the head and the tail is the gyserol. Lipid molecules are always moving, shaking and bouncing around each other. This type of movement is called flip flop movement. As the layers move between the two layers due to frictional motion, the membrane feels like a fluid.
2. Proteins: There are three types of proteins in the plasma membrane. These are-
(i) Peripheral Protein: The protein which is located at the edge of the lipid layer is called peripheral protein. It looks round. It is enzyme in nature. It remains attached to the cytoskeleton. Cyclins are produced from abundant pollen grains by the action of membrane bound enzymes.
(ii) Intrinsic Protein: The protein that is in the intrinsic state inside the lipid layer is called intrinsic protein. It looks oval. Acts as a carrier and transports essential substances. It maintains cell-to-cell adhesion.
(iii) Intermembrane Protein: The protein that extends from one end of the lipid layer to the other end is called an intermembrane protein. It is the largest protein. It changes its structure by taking energy from the ancha. As a result, a hole is created through it. Essential substances move through these pores. It acts as a receptor for hormones, neurotransmitters, mediated endocytosis, insulin etc. Various molecules, ions and electrons move through channels, pumps and electron transport chains.
3. Glycocalyx (Carbohydrate): Carbohydrate chains are present on the outside of the cell membrane. Carbohydrate chains are attached to lipids to form glycolipids and proteins to form glycoproteins. Glycoproteins and glycolipids together are called glycocalyx or cell coat. It acts as a cell-marking factor. It helps in the movement of essential substances.
4. Cholesterol: Cholesterol is a type of steroid. It has a claw on its head and is water absorbent. The other part is water repellent. Cholesterol is sandwiched between phospholipid molecules. It is irregularly arranged. Cholesterol is higher in animal cells and lower in plant cells.
Protein molecules are scattered between phospholipids in the cell membrane. Because of this, the protein molecules look like a mosaic when viewed from the surface of the cell membrane. To explain this situation in one word, the cell membrane model has been named ‘Fluid Mosaic Model’.

1. Phospholipids: There are five types of phospholipids in the cell membrane. Lecithin, cephalin, glycolipid, glycophosphotide and phosphotidic acid. Phospholipids are arranged in two layers. Each layer is composed of numerous lipid molecules. Each lipid molecule has two parts. head and tail The large outer part is called the head. It is spherical or oval and composed of phosphates. It is polar and hydrophilic. The two filament-like parts attached to the head are called tails. It is composed of fatty acids. The tail is non-polar and hydrophobic. Between the head and the tail is the gyserol. Lipid molecules are always moving, shaking and bouncing around each other. This type of movement is called flip flop movement. As the layers move between the two layers due to frictional motion, the membrane feels like a fluid.
2. Proteins: There are three types of proteins in the plasma membrane. These are-
(i) Peripheral Protein: The protein which is located at the edge of the lipid layer is called peripheral protein. It looks round. It is enzyme in nature. It remains attached to the cytoskeleton. Cyclins are produced from abundant pollen grains by the action of membrane bound enzymes.
(ii) Intrinsic Protein: The protein that is in the intrinsic state inside the lipid layer is called intrinsic protein. It looks oval. Acts as a carrier and transports essential substances. It maintains cell-to-cell adhesion.
(iii) Intermembrane Protein: The protein that extends from one end of the lipid layer to the other end is called an intermembrane protein. It is the largest protein. It changes its structure by taking energy from the ancha. As a result, a hole is created through it. Essential substances move through these pores. It acts as a receptor for hormones, neurotransmitters, mediated endocytosis, insulin etc. Various molecules, ions and electrons move through channels, pumps and electron transport chains.
3. Glycocalyx (Carbohydrate): Carbohydrate chains are present on the outside of the cell membrane. Carbohydrate chains are attached to lipids to form glycolipids and proteins to form glycoproteins. Glycoproteins and glycolipids together are called glycocalyx or cell coat. It acts as a cell-marking factor. It helps in the movement of essential substances.
4. Cholesterol: Cholesterol is a type of steroid. It has a claw on its head and is water absorbent. The other part is water repellent. Cholesterol is sandwiched between phospholipid molecules. It is irregularly arranged. Cholesterol is higher in animal cells and lower in plant cells.
Protein molecules are scattered between phospholipids in the cell membrane. Because of this, the protein molecules look like a mosaic when viewed from the surface of the cell membrane. To explain this situation in one word, the cell membrane model has been named ‘Fluid Mosaic Model’.

1. NADH-Q reductase: a 26-subunit compound.
2. Cytochrome reductase: A 10-subunit compound.
3. Cytochrome oxidase: An 8 subunit compound.
4. Cytochrome-C: A small protein.
** Ubiquinone: A non-protein compound.

1. Step 1: NADH2 is oxidized to release high-energy electrons (e-) and energy. The released electron carrier is taken up by NADH-Q reductase. The energy generated here drives the proton (H+) out of the inner membrane. Here an ATP is produced.
2. Step 2: Electrons are then transferred from NADH-Q reductase to the carrier ubiquinone (Co-Q). Next the electron (e-) from ubiquinone reaches the carrier cytochrome-b.
3. Step 3: FADH2 is oxidized to release high energy electrons (e-) and energy. The released electron carrier is taken up by cytochrome-b. The energy generated here drives the proton (H+) into the intermembrane space. Electrons then pass from cytochrome-B to carrier cytochrome-C.
4. Step IV: Electrons (e-) are transferred from cytochrome-C to cytochrome oxidase. Here the existing proton (H+) is sent to the intermembrane space. Finally, electrons are released into the mitochondrial matrix and combine with O2 to form H2O water.
5. Fifth step: Protons from the intermembrane space are re-entered into the matrix by ATP synthase in the process of chemi-osmosis. Here the energy released combines ADP and Pi to form ATP.
6. Sixth step: Electrons (e-) and protons (H+) react with oxygen in the matrix to produce H2O. The process stops when an oxygen vacancy occurs in the matrix.

The system through which electrons are transferred from one place to another and ATP and H2O are produced during the flow of electrons is called the electron transport system. It is also called respiratory chain. Energy is released at specific locations as electrons flow in this process. This energy combines ADP and Pi to form ATP. Thus the production of ATP with the help of the energy released in the oxidation process is called oxidative phosphorylation.
ADP + Pi → ATP
Several electron transport proteins combine to form multi-proteins. The inner membrane of mitochondria contains four multi-proteins (in order of strength) and transfer electrons. In this process NADH2, NADPH2, FADH2 and FADPH2 are oxidized to NAD, NADP, FAD and FADP and release energy. Under the influence of this energy, ATP is produced by combining ADP and Pi. Normally 2 of each FADH2 or FADPH2 and 3 of each NADH2 or NADPH2 are formed. [Currently, NADH2 = 2.5 ATP, FADH2 = 1.5 ATP]

1. Krebs cycle is the main center of energy production. This energy is used in various metabolic functions – mineral salt absorption, water absorption, transport, movement, growth, flowering etc.
2. α-ketoglutaric acid and oxaloacetic acid produced in this cycle help in nitrogen metabolism.
3. This process involves the production of amino acids.
4. Various types of organic acids produced in this cycle are used in metabolism.
5. In this cycle succinyl CO is produced. Succinyl Co-A is one of the building blocks of chlorophyll, cytochrome, hemoglobin, phycobilin etc.
6. Organisms release CO2 through this cycle.
7. Each molecule of glucose oxidized produces 24 ATP.
8. Pyrimidines and alkaloids are produced from oxaloacetic acid.
9. Oxidation of carbohydrates, fatty acids and amino acids occurs through the Krebs cycle.
10. Oxidative co-enzymes NADH+H+ and FADH2 are synthesized through the Krebs cycle.
11. This cycle links sugar metabolism with nitrogen metabolism.
12. This cycle is called amphibolic pathway as both addition and dissociation reactions occur.
13. This cycle is linked to the glyoxylate cycle.

1. Condensation: Acetyl CoA reacts with oxaloacetic acid to produce citric acid under the action of acetyl CoA condensing enzyme with the help of citrate synthetase.
2. Isomerization: Under the action of aconitase enzyme, cis-aconitic acid is produced from citric acid and then isocitric acid from cis-aconitic acid.
3. Dehydrogenation: Oxalosuccinic acid is produced from isocitric acid by the action of isocitrate dehydrogenase enzyme. At this time, NADP participates in the reaction and produces NADPH+H+. The reaction is bidirectional.
4. Decarboxylation: Under the action of oxalo succinate carboxylase enzyme, oxalo succinic acid is converted into alpha keto glutaric acid.
5. Oxidative decarboxylation: Succinyl Co is produced from alpha ketoglutaric acid with the help of alpha ketoglutarate dehydrogenase enzyme. At this time NADP participates in the reaction NADPH+H+
produces
6. ATP Synthesis: Succinic acid is produced from succinyl CoA in the presence of succinyl CoA synthetase enzyme. During this reaction, ADP takes part and produces ATP. The reaction is bidirectional.
7. Dehydrogenation: Fumaric acid is produced from succinic acid by the action of succinyl dehydrogenase enzyme. FAD participates in the reaction and produces FADH2. The reaction is bidirectional.
8. Hydration: Fumaric acid is converted to malic acid in the presence of fumarase enzyme. The reaction is bidirectional.
9. Dehydrogenation: Oxaloacetic acid is produced from malic acid with the help of malate dehydrogenase enzyme. At this time, NADP participates in the reaction and produces NADPH+H+.
The oxaloacetic acid produced then re-enters the Krebs cycle and keeps the cycle going.

1. Condensation: Acetyl CoA reacts with oxaloacetic acid to produce citric acid under the action of acetyl CoA condensing enzyme with the help of citrate synthetase.
2. Isomerization: Under the action of aconitase enzyme, cis-aconitic acid is produced from citric acid and then isocitric acid from cis-aconitic acid.
3. Dehydrogenation: Oxalosuccinic acid is produced from isocitric acid by the action of isocitrate dehydrogenase enzyme. At this time, NADP participates in the reaction and produces NADPH+H+. The reaction is bidirectional.
4. Decarboxylation: Under the action of oxalo succinate carboxylase enzyme, oxalo succinic acid is converted into alpha keto glutaric acid.
5. Oxidative decarboxylation: Succinyl Co is produced from alpha ketoglutaric acid with the help of alpha ketoglutarate dehydrogenase enzyme. At this time NADP participates in the reaction NADPH+H+
produces
6. ATP Synthesis: Succinic acid is produced from succinyl CoA in the presence of succinyl CoA synthetase enzyme. During this reaction, ADP takes part and produces ATP. The reaction is bidirectional.
7. Dehydrogenation: Fumaric acid is produced from succinic acid by the action of succinyl dehydrogenase enzyme. FAD participates in the reaction and produces FADH2. The reaction is bidirectional.
8. Hydration: Fumaric acid is converted to malic acid in the presence of fumarase enzyme. The reaction is bidirectional.
9. Dehydrogenation: Oxaloacetic acid is produced from malic acid with the help of malate dehydrogenase enzyme. At this time, NADP participates in the reaction and produces NADPH+H+.
The oxaloacetic acid produced then re-enters the Krebs cycle and keeps the cycle going.