42 public questions tagged with this topic.
The chemiosmotic hypothesis explains how ATP is generated due to a proton gradient across the thylakoid membrane. This follows from NCERT principle where the relation explains the outcome clearly for students in simple steps.
Ref: NCERT Biology Textbook for Class XI and XII (Botany section), Chapter: Morphology and Anatomy of Flowering Plants, Topic: Plant structure and tissue systems.
Mitochondria generate ATP through aerobic respiration, making them the powerhouse of the ll. This follows from latest NCERT 2026-27 principle explaining the concept clearly for NEET students in simple steps as per rationalized syllabus.
Ref: NCERT Biology Textbook - Latest Edition for Academic Session 2026-27 (Botany section, Rationalized Textbook for Class XI and XII), Chapter: Biology - Botany portion (Latest NCERT Textbooks for Academic Session 2026-27 -
Paternal mitochondria enter oocyte cytoplasm at fertilization localized in midpiece, but they are actively eliminated shortly thereafter to ensure maternal uniparental mitochondrial inheritance. Ubiquitination of sperm mitochondrial proteins, recognition by oocyte autophagy machinery, mitophagy and proteasomal degradation remove them before first cleavage divisions. Occasionally low-level paternal mtDNA leakage occurs but is exceptional. Therefore mitochondria do not persist, merge or form embryonic population; embryonic mitochondria derive entirely from oocyte pool amplified during oogenesis,
Ref: NCBI, Mitochondrial inheritance review: Ubiquitin-mediated paternal mitochondria degradation and mitophagy after mammalian fertilization.
Mitochondria originated from alphaproteobacterial endosymbiont engulfed by archaeal host over 1.5 billion years ago, retaining circular mitochondrial DNA, bacterial-type transcription and translation machinery including 55S mitoribosomes, and binary fission mediated by Drp1 and dynamin-like proteins, with genomes encoding core subunits of oxidative phosphorylation. Inner membrane houses respiratory chain complexes I to IV transferring electrons from NADH and FADH2 to oxygen producing proton gradient used by F0F1 ATP synthase to generate ATP, central to aerobic metabolism. This organelle occurs
Ref: Cooper and Hausman, The Cell, 8th ed., Chapter 4: Mitochondria Distribution in Eukaryotes.
Cardiolipin, diphosphatidylglycerol, uniquely contains two phosphatidic acid moieties linked by central glycerol bridge, resulting in four acyl chains, typically tetralinoleoyl 18:2 in cardiac tissue conferring fluidity, and small headgroup with two negative charges at physiological pH. Synthesized in mitochondria by condensation of phosphatidylglycerol and CDP-diacylglycerol catalyzed by cardiolipin synthase CRLS1 on matrix side of inner membrane followed by remodeling via tafazzin transacylase exchanging chains to mature unsaturated form. Its conical shape with large hydrophobic volume impos
Ref: Lehninger Principles of Biochemistry, 8th ed., Chapter 19: Cardiolipin, Mitochondrial Signature Lipid.
F-type ATPases, often called ATP synthases, are evolutionarily related to V-type pumps but adapted for opposite physiological purpose in most contexts. Located in bacterial plasma membrane, mitochondrial inner membrane cristae and chloroplast thylakoid membrane, they consist of soluble F1 catalytic head containing alternating alpha and beta subunits around central gamma stalk and membrane embedded Fo base containing a subunit and c-ring proton channel. In respiring membranes electron transport complexes pump protons outward creating proton motive force combination of pH gradient and electrical
Ref: Boyer, Nobel Lecture 1997, F-Type ATP Synthase Rotary Mechanism and ATP Synthesis.
Exchange of metabolites between cytosol and mitochondria requires regulated permeability across the outer membrane, which unlike inner membrane does not maintain large electrochemical gradient. Voltage-dependent anion channel, VDAC, also called mitochondrial porin, forms the major outer membrane channel present in thousands of copies. Mammalian cells express three isoforms VDAC1, VDAC2 and VDAC3 that assemble as 19-stranded beta-barrel pores with N-terminal helix gating, permitting diffusion of ions, ATP, ADP, succinate, citrate, malate, NADH and other molecules up to about 5 kDa with cut-off
Ref: Alberts et al., Molecular Biology of the Cell, 7th ed., Chapter 14: VDAC and Mitochondrial Metabolite Transport.
Long-chain fatty acids activated to fatty acyl-CoA by acyl-CoA synthetase on the cytosolic face of endoplasmic reticulum and outer mitochondrial membrane cannot diffuse across the inner mitochondrial membrane, so a dedicated import shuttle is essential for matrix beta-oxidation. Carnitine palmitoyltransferase I, CPT I, localized to the outer membrane with catalytic site facing cytosol, transfers the acyl group to carnitine, forming acylcarnitine plus free CoA. Acylcarnitine is then shuttled across the inner membrane by the carnitine-acylcarnitine translocase, CACT, an antiporter exchanging acy
Ref: Berg et al., Biochemistry, 9th ed., Chapter 22: Fatty Acid Oxidation and Carnitine Shuttle.
Outer membrane of mitochondrion is symmetric phospholipid bilayer containing cholesterol and porin channels that confer permeability to small solutes under five kilodaltons, distinguishing it from highly selective inner membrane bearing electron transport chain. Integral protein voltage-dependent anion channel VDAC, also called porin, forms nineteen-stranded beta-barrel with N-terminal alpha helix gating, isoforms VDAC1 most abundant, VDAC2, VDAC3 regulate metabolite exchange ADP ATP across intermembrane space, calcium transfer at mitochondria ER associated membranes interacting with IP3R via
Ref: Shoshan-Barmatz Cell Death Dis; VDAC outer membrane porin metabolite gatekeeper apoptosis regulation.
Mitochondria are multifunctional organelles originating from endosymbiosis retaining sixteen point six kilobase circular genome encoding thirteen oxidative phosphorylation polypeptides, twenty two tRNAs, two rRNAs. Inner membrane cristae house electron transport chain complexes generating proton gradient driving F1Fo ATP synthase producing up to thirty ATP per glucose, contributing most cellular ATP under aerobic conditions. Matrix contains calcium uniporter MCU complex buffering cytosolic spikes shaping NFAT signaling and buffering, also participates in heme pathway where ALA synthase in matr
Ref: Friedman Annu Rev Cell Biol; mitochondria ATP Ca++ heme Fe-S apoptosis; folding in ER.
Endosymbiosis is supported by mitochondrial translation apparatus resembling bacteria. Mitochondrial ribosomes, mitoribosomes, in mammals sediment as fifty five S composed of twenty eight S small and thirty nine S large subunits, total mass two point seven megadaltons, containing two rRNAs and about eighty two proteins where only thirty percent homologous to bacterial proteins and rest mitochondria-specific adaptations for membrane protein synthesis. They retain bacterial features such as leaderless initiation, formylmethionine start, lack of five prime cap, and sensitivity to tetracycline, ch
Ref: Gray Annu Rev Genet; mitochondria endosymbiont mitoribosome 55S homologous to bacterial 70S.
Evolutionary conservation membrane insertases bacterial plasma membrane reveals OXA family YidC Alb3 Oxa1. Mitochondrial Oxa1 45 kDa inner membrane five transmembrane helices forms co-translational insertion site adjacent matrix mitoribosome large subunit near exit tunnel via Mrpl45 interaction. Several highly hydrophobic proteins encoded mitochondrial DNA including subunit II III cytochrome oxidase Cox2 Cox3 subunit a c ATP synthase Atp6 Atp9 cytochrome b Cob synthesized matrix mitoribosomes because extreme hydrophobicity would hamper import. Oxa1 central hydrophilic groove provides aqueous p
Ref: Hennon et al., Front Physiol 2015: OXA insertase inserts proteins into mitochondrial inner membrane.
