Human Physiology

Step 1: In biological nomenclature, each organism is given a binomial name consisting of a genus name and a species name.
Step 2: When the genus name and species name are exactly the same, such a name is called a tautonym.
Step 3: Examples of tautonyms include:

\textit{Bison bison}
\textit{Naja naja}

Step 4: Tautonyms are permitted in zoological nomenclature but not in botanical nomenclature.

Step 1: T.O. Diener was an American plant pathologist.
Step 2: In 1971, he discovered viroids, which are the smallest known infectious agents.
Step 3: Viroids consist only of short strands of naked RNA and do not have a protein coat.
Step 4: Hence, viroids are described as free infectious RNA.

Step 1: Plasmids are extrachromosomal, circular DNA molecules that possess their own origin of replication. Hence, statement I is correct.
Step 2: In genetic engineering, a hybrid (recombinant) plasmid carrying foreign DNA is commonly introduced into bacterial cells by the process of transformation. Hence, statement II is correct.
Step 3: Bacteriophages are viruses that infect bacteria and contain their own viral genome. Plasmids are not found in bacteriophages; they are independent replicons mainly present in bacteria (and some eukaryotes like yeast). Hence, statement III is incorrect.

Step 1: A very large amount of solar energy reaches the Earth’s atmosphere.
Step 2: Only a small fraction of this energy is absorbed by plants for the process of photosynthesis.
Step 3: Of the total solar radiation:

Much is reflected back into space,
Much is absorbed as heat,
Only a tiny fraction is converted into chemical energy by plants.

Step 4: Experimental and ecological studies show that only about 0.2% of the sunlight energy reaching the atmosphere is ultimately utilized in photosynthesis.

Step 1: Transmembrane transport involves movement of molecules across a biological membrane through protein channels or transporters.
Step 2:

(A) Stroma thylakoid space involves transport across the thylakoid membrane.
(B) Cytoplasm ER lumen involves transport across the ER membrane via translocons.
(D) Intermembrane space mitochondrial matrix involves transport across the inner mitochondrial membrane.

Step 3: Transport from ER to Golgi does not occur by crossing a membrane directly. Instead, proteins are moved via vesicular transport, where membrane-bound vesicles bud off from the ER and fuse with the Golgi.
Step 4: Since vesicular transport does not involve passage through a membrane, it is not transmembrane transport.

Step 1: Reactive Oxygen Species (ROS) such as superoxide anion ( ) are generated due to leakage of electrons from the mitochondrial electron transport chain (ETC).
Step 2: Complex I (NADH dehydrogenase) can leak electrons directly to molecular oxygen, forming superoxide.
Step 3: Complex III (cytochrome bc complex) also contributes significantly to ROS generation during the Q-cycle.
Step 4: Complex II contributes very little to ROS generation, and Complex IV efficiently transfers electrons to oxygen to form water, not ROS.
Step 5: Hence, the major complexes involved in ROS generation are Complex I and Complex III.

Step 1: The cell cycle consists of phases G , S, G , and M.
Step 2: Some cells permanently stop dividing and exit the active cell cycle.
Step 3: These cells enter a resting or quiescent phase known as G phase.
Step 4: Neurons and skeletal muscle cells are terminally differentiated and remain permanently in the G phase.

Step 1: A transgenic animal is one whose genome has been permanently altered by the introduction of a foreign gene.
Step 2: There is no single fixed sequence of steps to produce a transgenic animal.
Step 3: Different independent techniques are used for gene transfer, such as:

Microinjection
Electroporation
Transfection
Retroviral vector-mediated gene transfer

Step 4: These methods are alternative approaches, not sequential steps used one after the other.
Step 5: The term transgenics refers to the \emph{final product}, not a procedural step.
Step 6: Hence, none of the given options correctly represent a valid sequence.

Step 1: Digestion of carbohydrates begins in the mouth.
Step 2: Saliva contains the enzyme salivary amylase (ptyalin).
Step 3: Salivary amylase hydrolyses starch into maltose and dextrins.
Step 4: In the stomach, acidic pH inactivates salivary amylase, so no further starch digestion occurs there.

Step 1: The vagina is subjected to friction and mechanical stress.
Step 2: Stratified squamous epithelium is well suited to protect underlying tissues from abrasion.
Step 3: This type of epithelium consists of multiple layers of cells, providing strength and protection. Hence, the lining of the vagina is covered with stratified squamous epithelium.

Step 1: Glycolysis is the first step of cellular respiration in which glucose is broken down into pyruvate.
Step 2: This process does not require any membrane-bound organelle and occurs in the cytoplasm of the cell.
Step 3: Mitochondria are involved in later stages of respiration such as the Krebs cycle and oxidative phosphorylation. Hence, glycolysis takes place in the cytoplasm.

Step 1: Identify the pollutant involved. The question refers to fish living in mercury-contaminated water. Mercury, especially in the form of methyl mercury, enters aquatic food chains.
Step 2: Understand bioaccumulation.
Mercury accumulates in aquatic organisms.
Concentration increases at higher trophic levels.
Humans consuming contaminated fish receive toxic doses.
Step 3: Recall the disease associated with mercury poisoning. Minamata disease is a neurological disorder caused by methyl mercury poisoning. It was first identified in Minamata, Japan, due to industrial mercury discharge into water bodies.
Step 4: Eliminate incorrect options.
Hiroshima episode: Related to nuclear radiation.
Bright’s disease: A kidney disorder.
Osteosclerosis: Abnormal hardening of bones.
Hence, the correct answer is

Step 1: Understand what pulmonary circulation is. Pulmonary circulation refers to the movement of blood between the heart and the lungs.
Step 2: Describe the pathway.
Deoxygenated blood is pumped from the right ventricle to the lungs via the pulmonary artery.
In the lungs, blood becomes oxygenated.
Oxygenated blood returns to the left atrium via the pulmonary veins.
Step 3: Eliminate incorrect options.
Cardiac circulation: Not a standard term for lung circulation.
Gastric circulation: Refers to blood flow to the stomach.
Trachea: An air passage, not a circulatory system.
Hence, the correct answer is

Step 1: Understand what gastric juice is. Gastric juice is a digestive fluid secreted by the gastric glands in the stomach.
Step 2: Identify the components of gastric juice. Gastric juice contains:
Hydrochloric acid (HCl) — creates acidic medium and kills bacteria.
Pepsin enzyme — digests proteins.
Mucus — protects the stomach lining.
Step 3: Verify each statement.
Kill bacteria — True, due to presence of HCl.
Digest food — True, enzymes like pepsin digest proteins.
Include hydrochloric acid — True.
Step 4: Draw conclusion. Since all the given statements are correct,
Hence, the correct answer is

Step 1: Recall the origin of lymphocytes. All lymphocytes originate from hematopoietic stem cells present in the bone marrow.
Step 2: Understand B-lymphocyte maturation.
B-lymphocytes are formed in the bone marrow.
They also undergo preprocessing (maturation) in the bone marrow itself. (The letter B in B-lymphocytes originally stands for \emph{Bursa of Fabricius} in birds, but in humans, this function is carried out by the bone marrow.)
Step 3: Eliminate incorrect options.
(A) Incomplete — does not mention preprocessing.
(B) Incomplete — ignores formation.
(C) Incorrect — liver is not involved in lymphocyte maturation.
Hence, the correct answer is

Step 1: Recall what Tyson’s glands are. Tyson’s glands are sebaceous glands present in the male reproductive system. They secrete a lubricating substance (smegma).
Step 2: Identify their anatomical location. These glands are located on the inner surface of the prepuce (foreskin) of the penis, near the glans.
Step 3: Eliminate incorrect options.
Urethra: Passage for urine and semen, not the site of Tyson’s glands.
Scrotum: Sac enclosing testes; contains sweat and sebaceous glands, but not Tyson’s glands.
Epididymis: Coiled tube for sperm maturation, unrelated to glandular secretion.
Hence, the correct answer is

Step 1: Recall the stages of cellular respiration. Cellular respiration occurs in three main stages:
Glycolysis — in cytosol
Citric acid cycle (Krebs cycle) — in mitochondria
Electron transport chain — inner mitochondrial membrane
Step 2: Identify the location of the citric acid cycle. The citric acid cycle occurs in the mitochondrial matrix of eukaryotic cells.
Step 3: Eliminate incorrect options.
Cytosol: Site of glycolysis, not the citric acid cycle.
Peroxisomes: Involved in fatty acid oxidation and detoxification.
None of these: Incorrect since mitochondria is listed.
Hence, the correct answer is

Step 1: Understand what hinge joints are. Hinge joints are a type of joint that allow movement in a single plane, similar to the opening and closing of a door.
Step 2: Verify each statement.
(A) Are synovial joints — True. Hinge joints belong to the synovial joint category, which have a synovial cavity.
(B) Permit movements in one direction — True. They allow flexion and extension only.
(C) Are found in knee — True. The knee joint is a classic example of a hinge joint.
Step 3: Draw the conclusion. Since all the given statements are correct,
Hence, the correct answer is

Step 1: Understand what the question refers to. In standard biology questions, this refers to the glomerular filtration rate (GFR), i.e., the amount of blood plasma filtered by the kidneys per minute.
Step 2: Recall the normal value of GFR. In a healthy adult: This value represents the average amount of blood filtered through the kidneys each minute.
Step 3: Match with the given options. The range closest to the normal GFR is:
Hence, the correct answer is

Step 1: Recall the resting potential of a neuron. A neuron at rest maintains a resting membrane potential of about , with the inside of the axon being negatively charged relative to the outside.
Step 2: Understand ion permeability at rest. At resting state:
The axonal membrane is highly permeable to ions due to open potassium leak channels.
The membrane is nearly impermeable to ions because most sodium channels are closed. This selective permeability causes more ions to diffuse out than ions to diffuse in, maintaining the negative resting potential.
Step 3: Eliminate incorrect options.
(B) Incorrect — sodium permeability is low at rest.
(C) Incorrect — permeability is not equal.
(D) Incorrect — membrane is selectively permeable, not impermeable.
Hence, the correct answer is