Cell Biology and Structure

The mitochondria are known as the powerhouse of the cell because they are the site of cellular respiration, where ATP is generated.

Ribosomes are the cellular structures responsible for protein synthesis. The stomach and liver are organs, not organelles, and lysosomes are involved in waste breakdown.

Fermentation is an anaerobic process that occurs entirely in the cytoplasm of the cell, as it does not require the mitochondria, which are used for aerobic respiration.

Phagocytosis is the process of engulfing large particles (cellular eating), while pinocytosis is the process of taking in extracellular fluid and dissolved solutes (cellular drinking).

The cell is considered the fundamental structural and functional unit of all living organisms.

The process that converts light energy into chemical energy takes place in a multi-protein complex called a photosystem. Two types of photosystems are embedded in the thylakoid membrane:- photosystem II ( PSII) and photosystem I (PSI). Each photosystem plays a key role in capturing the energy from sunlight by exciting electrons. These energized electrons are transported by “energy carrier” molecules, which power the light-independent reactions.

The human body hosts a vast ecosystem of microorganisms, including bacteria, fungi, and viruses, which collectively number in the trillions. The other options significantly underestimate or misrepresent biological counts.

Cells are microscopic structures that form the basic unit of life, making them larger than individual molecules but smaller than visible organisms or tissues. The other options are nonsensical in this context.

Cells are the fundamental building blocks of all living organisms. While organisms contain blood and body parts, those are composed of cells.

Porins are beta barrel proteins that cross a cellular membrane and act as a pore, through which molecules can diffuse. Unlike other membrane transport proteins, porins are large enough to allow passive diffusion, i.e., they act as channels that are specific to different types of molecules. Porins from non-green plastids and from the outer mitochondrial membrane were re- constituted into planar lipid bi-layers. The proteins showed high pore-forming activities and similar single- channel conductance. So, the correct option is "Not associated with the inner membrane of plastids".

Oxysomes are found in inner mitochondrial membrane and also called ad $F _1$ or elementary particles. It contains enzymes ATP synthase responsible for synthesis of ATP. They act as phosphorylating unit.

Spherosomes are membrane covered small spherical organelles which synthesize and store fats. They are covered with a single half unit membrane.

Endomembrane system of a eukaryotic cell is a membrane system that involves flow of membranes from one component to another by means of small membrane vesicles. The endomembrane system of a eukaryotic cell consists of endoplasmic reticulum, Golgi apparatus, lysosomes and plasma membrane.

Spherosomes are membrane covered small spherical organelles which synthesize and store fats. They develop from endoplasmic reticulum. In some plants, spherosomes have lysosomal activity, e.g., maize root tip.

Peroxisomes are microbodies which have enzymes for peroxide metabolism. They include :
(a) Peroxide producing oxidative enzymes like peroxidase, urate oxidase or uricase, amino acid oxidase.
(b) Peroxide destroying enzymes like catalase.