The transmembrane regions of proteins are predominantly formed by α-helices due to their ability to interact favorably with the hydrophobic core of the lipid bilayer. Hydrophobic side chains extend outward to interact with the lipid bilayer, while the backbone hydrogen bonds stabilize the helix. β-sheets, in contrast, are typically seen in specific pore-forming structures like porins.

Key Enzyme Functions:

• Cytochrome oxidase: Functions in the electron transport system, facilitating ATP synthesis.
• Topoisomerases: Change the linking number of DNA, aiding replication and transcription.
• Cohesins: Bind sister chromatids until segregation during cell division.
• PCNA: Proliferating cell nuclear antigen, essential for DNA replication and repair.

Citrate acts as a feedback inhibitor for PFKII, a key regulatory enzyme in glycolysis. By inhibiting PFKII, citrate helps balance energy production between glycolysis and the Kreb’s cycle, ensuring efficient energy use.

Key reasons for destabilization:

• (A): Proline introduces a sharp kink in the α-helix.
• (B): Its nitrogen atom is part of a rigid ring, preventing rotation around the N-C bond.
• (C): Proline lacks a substituent hydrogen for hydrogen bonding, a key stabilizer in α-helices.

Lipid rafts are specialized microdomains in the plasma membrane that are rich in cholesterol and sphingolipids. These domains play a significant role in cellular signaling, protein sorting, and trafficking. They are more ordered and tightly packed compared to the surrounding membrane but maintain fluidity.

Galactosemia is caused by a deficiency in galactose-1-phosphate uridyltransferase (GALT). This enzyme converts galactose-1-phosphate into UDP-galactose, a critical step in galactose metabolism. Its deficiency results in toxic accumulation, causing severe complications like liver damage and developmental delays.

Key pairings for vitamins and disorders:

• Vitamin-A: Deficiency causes night blindness.
• Vitamin-D: A fat-soluble vitamin essential for bone health.
• Vitamin-C: Deficiency leads to scurvy.
• Vitamin-K: Necessary for blood clotting.

The intermediates in glycolysis are formed in the sequence:

• Fructose 6-phosphate (B) → Fructose 1,6-biphosphate (A)
• Phosphoenolpyruvate (D) → Lactate (C) (under anaerobic conditions).

Sequence of enzymes in the TCA cycle:

• Aconitase: Converts citrate to isocitrate.
• α-ketoglutarate dehydrogenase: Converts α-ketoglutarate to succinyl-CoA.
• Fumarase: Converts fumarate to malate.
• Malate dehydrogenase: Converts malate to oxaloacetate.

Xylene cyanol is a tracking dye used in gel electrophoresis to visualize DNA/RNA migration. It does not emit fluorescence, unlike Alexa Fluor, GFP, and DsRed.

Colony hybridization is a molecular technique where bacterial colonies are lysed and transferred to a membrane. A labeled probe is used to detect the presence of a specific DNA sequence in the colonies.

Size-exclusion chromatography separates molecules based on their size using a porous matrix. Larger molecules elute first as they cannot enter the pores, while smaller molecules are retained longer.

The Shine-Dalgarno sequence is a ribosomal binding site in the 5’ untranslated region (UTR) of prokaryotic mRNA. It helps align the ribosome with the start codon for translation initiation.

Helicase unwinds the DNA double helix at the replication fork, creating single-stranded templates for replication. Topoisomerase prevents supercoiling, while DNA polymerase and ligase have other roles in replication.

Protein synthesis occurs in the rough endoplasmic reticulum (RER), not the smooth ER. The smooth ER is involved in lipid synthesis, detoxification, and calcium storage.

Okazaki fragments are short DNA fragments synthesized discontinuously on the lagging strand during replication. They are later joined by DNA ligase to form a continuous strand.

Vasopressin, also known as antidiuretic hormone (ADH), is synthesized by the hypothalamus and stored in the posterior pituitary, not the anterior pituitary gland.

RuBisCO catalyzes the fixation of CO₂ to ribulose-1,5-bisphosphate in the Calvin cycle, a critical step in photosynthesis.

ATP synthase is involved in the synthesis of ATP through oxidative phosphorylation, but it is not a direct component of the electron transport chain (ETC), which includes cytochrome c, ubiquinone, and Complex IV.

A nucleosome is the fundamental unit of chromatin, consisting of DNA wrapped around histone proteins. It compacts DNA into an organized structure within the nucleus.

Enzymes act as catalysts and are not consumed during the reaction. They are regenerated at the end and can be reused multiple times.

Myosin interacts with actin filaments in muscle cells, facilitating contraction through ATP hydrolysis and the sliding filament mechanism.

Allolactose is the inducer molecule in the lac operon. It binds to the repressor protein, inactivating it and allowing transcription of the operon.

The codon AUG serves as the start codon in mRNA and codes for the amino acid methionine, initiating protein synthesis.

A peptide bond links amino acids in proteins and is not a component of nucleotides, which consist of a phosphate group, a sugar (ribose or deoxyribose), and a nitrogenous base.

Leaves are the primary site of photosynthesis due to the presence of chloroplasts, which contain chlorophyll that captures light energy for the process.

The nucleolus is a dense region within the nucleus responsible for ribosomal RNA (rRNA) synthesis and ribosome assembly.

Lysosomes contain hydrolytic enzymes that break down cellular debris, damaged organelles, and foreign materials, aiding in intracellular digestion.

A glycosidic bond
connects two monosaccharides in a disaccharide through a condensation reaction, releasing a molecule of water.

In aerobic respiration , oxygen acts as the final electron acceptor in the electron transport chain, forming water as a byproduct.

The sigma factor is a protein subunit that helps RNA polymerase recognize the promoter regions of DNA to initiate transcription in prokaryotes. It dissociates after initiation.

Active transport requires energy to move substances against their concentration gradient, unlike passive transport mechanisms like diffusion, facilitated diffusion, and osmosis.

The mitochondria are known as the powerhouse of the cell. They generate ATP through oxidative phosphorylation during cellular respiration.

Meiosis is a specialized cell division process that reduces the chromosome number by half, resulting in the formation of haploid gametes in animals.

β-pleated sheets are a type of secondary structure in proteins, stabilized by hydrogen bonds between the backbone atoms in the polypeptide chain.

Thymine is replaced by uracil in RNA, whereas DNA contains thymine as one of its nitrogenous bases.

A peptide bond
is a covalent bond that links the carboxyl group of one amino acid to the amino group of another through a condensation reaction.

Ribosomes are the site of protein synthesis, where mRNA is translated into a polypeptide chain.

A phosphodiester bond connects the 5’ phosphate group of one nucleotide to the 3’ hydroxyl group of the next nucleotide in a DNA strand.

Lysosomes are called "suicide bags" because they contain hydrolytic enzymes that can break down the cell’s own components during programmed cell death or autophagy.

The G1 phase of the cell cycle is the longest, as it is the period of cell growth and preparation for DNA synthesis in the S phase. It involves intense metabolic activity and synthesis of cellular components.

cAMP (cyclic adenosine monophosphate) is a second messenger that transmits signals from cell surface receptors to target molecules within the cell, amplifying the signal.

The Golgi apparatus modifies, sorts, and packages proteins and lipids for secretion or delivery to other organelles.

Chloroplasts are present in plant cells and are responsible for photosynthesis. They are absent in animal cells, which lack the ability to photosynthesize.

Ribosomes are the molecular machines responsible for translating mRNA into polypeptide chains, leading to protein synthesis.

tRNA (transfer RNA) carries amino acids to the ribosome, matching them to the corresponding codons on the mRNA during translation.

During photosynthesis, the oxygen released comes from the splitting of water molecules (photolysis) in the light-dependent reactions.

Retroviruses have RNA as their genetic material. They use reverse transcriptase to convert RNA into DNA, which integrates into the host genome.

Lipids , specifically phospholipids, form the bilayer structure of the plasma membrane, providing both fluidity and a barrier to external environments.

ATP (adenosine triphosphate) is the primary energy currency of the cell, providing energy for various biochemical processes.

Calcitonin is a peptide hormone secreted by the parafollicular cells (C cells) of the thyroid gland. It plays a crucial role in regulating blood calcium levels by inhibiting osteoclast activity, thus reducing bone resorption and lowering calcium levels in the blood.

Lymphoid stem cells in the bone marrow give rise to:

• Natural Killer (NK) cells: Part of the innate immune system, they help destroy infected or cancerous cells.
• B lymphocytes: Part of the adaptive immune system, they produce antibodies and regulate immune responses.

The foramen ovale is a crucial structure in fetal circulation that allows blood to bypass the lungs, which are not yet functional. After birth, it closes and leaves a depression called the fossa ovalis.

Platyhelminthes lack a true body cavity (coelom). Their bodies are filled with mesodermal cells, making them acoelomates, which rely on diffusion for transport and exchange of substances.

Matching mapping methods with their respective functions ensures clarity in genetic research techniques.

Hemophilia is a genetic disorder affecting blood clotting. It is X-linked recessive, primarily affecting males. It is caused by a deficiency of clotting factors VIII (Hemophilia A) or IX (Hemophilia B).

Sphagnum, commonly known as peat moss, grows in wetlands and forms peat, a significant carbon reservoir.

The basal part of the ligule, called Glossopodium, supports and protects the ligule in Selaginella.

Gnetum is unique among gymnosperms for having vessels in its xylem, resembling angiosperms.

Key transposons matched with their respective organisms for their unique applications in genetic studies.

Peptidyl transferase catalyzes the formation of peptide bonds during protein synthesis. This activity resides in the rRNA of the large ribosomal subunit (50S in prokaryotes, 60S in eukaryotes). The small ribosomal subunit aids in mRNA decoding, while tRNA assists in amino acid recognition but lacks enzymatic activity.

TFIIA stabilizes the binding of TFIID to the promoter, while TFIIB recruits RNA polymerase II to initiate transcription. The TATA box is a DNA sequence, not a transcription factor, and small nuclear ribonucleoproteins are involved in RNA splicing, not transcription initiation.

Histone H1 is the linker histone that binds to the DNA entering and exiting the nucleosome, stabilizing the higher-order chromatin structure. It is not part of the histone octamer (H2A, H2B, H3, H4).

In eukaryotes, RNA polymerase III synthesizes tRNA along with 5S rRNA. RNA polymerase I transcribes rRNA (except 5S rRNA), and RNA polymerase II synthesizes mRNA and some snRNAs.

Crisscross inheritance is a pattern typical of X-linked traits, where a male passes his X chromosome to his daughters, who can then pass it to their sons. This highlights the X-chromosome transmission across generations.

The Barr body is an inactivated X chromosome in females, condensed to ensure dosage compensation between males and females. It is transcriptionally silent.

In the C4 cycle:

Pyruvic acid moves from bundle sheath cells to mesophyll cells for regeneration of phosphoenolpyruvate (PEP).

• A: Malic acid is formed in mesophyll cells.
• B: Malic acid is transported to bundle sheath cells for decarboxylation and CO₂ release.

In X-linked recessive inheritance, affected mothers have two defective X chromosomes and will pass one defective X chromosome to all their sons, who will exhibit the trait.

Specific matches:

• Color blindness: Caused by insensitivity to green and red light.
• Hemophilia B: Deficiency in clotting factor IX.
• Hemophilia A: Deficiency in clotting factor VIII.
• G-6-PD deficiency: Leads to anemia under oxidative stress.

Bryophytes are simple non-vascular plants that include mosses, liverworts, and hornworts. They rely on diffusion for transport and thrive in moist environments.

Taxol, a widely used chemotherapy drug, is extracted from the bark of the Pacific yew tree (Taxus brevifolia). It stabilizes microtubules, preventing their depolymerization, thereby disrupting cell division in rapidly dividing cancer cells.

Tendu leaves, obtained from the Diospyros lotus tree, are used for wrapping bidis. Their flexibility, durability, and moisture retention make them ideal for rolling tobacco.

In the light reaction:

• Pheophytin: Primary electron acceptor in Photosystem II.
• Plastoquinone: Transfers electrons to the Cytb6-f complex.
• Cytb6-f complex: Facilitates electron transfer to Plastocyanin.
• Plastocyanin: Transfers electrons to Photosystem I.

Key matches for photoperiodism:

• Short Day Plants (SDP): Require long dark periods (14–16 hours).
• PR: Absorbs light at 660–665 nm.
• Long Day Plants (LDP): Require long daylight periods (14–16 hours).
• PFR: Absorbs light at 730–735 nm.

The steps in green tea processing:

• Initial removal of moisture content: Softens the leaves.
• Twisting and rolling: Breaks up leaves and releases flavor compounds.
• Crushing, Tearing, and Curling (CTC): Ensures uniform texture.
• Fermentation and drying: Preserves flavor and aroma.