Test: Plastids, Cilia & Flagella - 2 - NEET MCQ

Glyoxysomes are specialized peroxisomes found in plants, particularly in the fat storage tissues of germinating seeds and also in filamentous fungi. As in all peroxisomes, in glyoxysomes the fatty acids are hydrolyzed to acetyl-CoA by peroxisomal oxidation enzymes. Besides peroxisomal functions, glyoxysomes possess additionally the key enzymes of glyoxylate cycle which accomplish the glyoxylate cycle bypass. Thus, glyoxysomes contain enzymes that initiate the breakdown of fatty acids and additionally possess the enzymes to produce intermediate products for the synthesis of sugars by gluconeogenesis. The seedling uses these sugars synthesized from fats until it is mature enough to produce them by photosynthesis. Glyoxysomes also participate in photorespiration and nitrogen metabolism in root nodules.

Palade particles are ribosome.1955 George Palade discovered previously unknown organelles in the cell, as Palade particles where the cell's formation of proteins takes place. Later renamed ribosomes, and are now well known as the sites of protein synthesis. Hence, "Palade particles" are Ribosomes.

• Function: Ribosomes are responsible for synthesizing proteins by translating mRNA into amino acids.


• Structure: Ribosomes are composed of two subunits, one large and one small, that come together during protein synthesis.


• Location: Ribosomes can be found in the cytoplasm of the cell or attached to the endoplasmic reticulum.


• Process: Ribosomes read the genetic information in mRNA and use transfer RNA (tRNA) to bring the correct amino acids to the ribosome for protein assembly.


• Importance: Protein synthesis is essential for cell growth, repair, and function, making ribosomes a crucial component of cellular activity.

As the tomato ripens, its colour starts to change from green to yellow and then eventually to red. This is due to the breakdown of chlorophyll, which in turn synthesises a red carotenoid (another pigment group), lycopene. When ripe, the carotenoid can easily be seen as the dominant colour of the tomato.

• Ribosomes: Polysomes are chains of ribosomes that are responsible for protein synthesis in cells.

Polysomes play a crucial role in the translation process by coordinating the synthesis of multiple proteins simultaneously.

• Loss of Ribosomes: Ribosomes are responsible for protein synthesis in the rough endoplasmic reticulum (RER).


• Ribosomes detach: When ribosomes are lost from the RER, it converts into smooth endoplasmic reticulum (SER).


• Function of SER: The SER is involved in lipid metabolism, carbohydrate metabolism, and detoxification of drugs and toxins.


• No longer involved in protein synthesis: Since ribosomes are lost, the SER does not participate in protein synthesis like the RER.

Therefore, by the loss of ribosomes, the rough endoplasmic reticulum converts into smooth endoplasmic reticulum in the cell.

DNA of chloroplast discovered by Ris and Plaut. Chloroplasts have their own circular DNA. It is also known as the plastome. Due to the presence of DNA and own protein-forming machinery, it is called as semiautonomous organelle.

Anthocyanins are present in cell sap. They are found in flowers, fruits, leaves, stems and root. They are also present in outer layers such as epidermis and peripheral mesophylls.

Dynein forms an integral part of cilia. It is a motor protein which converts the chemical energy contained in ATP into the mechanical energy of movement. Dynein transports various cellular cargo by "walking" along cytoskeletal microtubules towards the minus-end of the microtubule, which is usually oriented towards the cell center. 

Axonemal dynein causes sliding of microtubules in the axonemes of cilia and flagella and is found only in cells that have those structures. There are parallels between the sliding filaments of skeletal muscle myosin and the sliding microtubules of cilia. Both are powered by ATP. Both motors dynein in cilia, myosin in skeletal muscle are ATPases. Both are regulated by calcium ions.

RNA is most abundant substances of ribosomes. Ribosomes are composed of proteins and ribosomes RNA.

Centrosomes are structures found inside of cells. They are made from two centrioles. Centrioles are microtubule rings. The main purpose of a centrosome is to organize microtubules and provide structure for the cell, as well as work to pull chromatids apart during cell division. Centrosome is the area where the spindle fibers begin for form. The centrosome is necessary for mitosis because without centrosome, the spindle fibers would not form, therefore there will be nothing to pull the sister chromtids apart to opposite directions and mitosis would not happen properly.

A basal body or blepharoplast is an organelle formed from a centriole, and a short cylindrical array of microtubules. It is found at the base of a eukaryotic undulipodium and serves as a nucleation site for the growth of the axoneme microtubules. Centrioles, from which basal bodies are derived, act as anchoring sites for proteins that in turn anchor microtubules within centrosomes, and are known as the microtubule organizing center (MTOC). These microtubules provide structure and facilitate movement of vesicles and organelles within many eukaryotic cells. The term, basal body is, however, reserved specifically for the base structures of eukaryote cilia and flagella which extend out from the cell.

Pigment present in petals of tangetes is xanthophyll . And in petal of sunflower is anthrocyanin.

• Svedberg unit: The 's' in the context of ribosomes refers to Svedberg unit, a unit used to measure the rate of sedimentation of particles in a centrifuge. It is not a measure of size but rather a measure of how quickly a particle sediments in a centrifugal field.


• Procaryotic Ribosomes: These ribosomes are smaller than eukaryotic ribosomes and are measured to be 70S, consisting of a 50S subunit and a 30S subunit.


• Function: Ribosomes are responsible for protein synthesis, where they translate mRNA into proteins by assembling amino acids in the correct order.


• Comparison: Eukaryotic ribosomes are larger and are measured as 80S, with a 60S subunit and a 40S subunit.

Rhizoplast is a fibril which is a connecting link between blepharoplast, with the nucleus in flagellated cells or organisms. It is a striated contractile structure attached to the basal region of the cilium in a variety of ciliates and flagellates. Many regulate the flagellar beat pattern, and is sensitive to calcium concentration. They are composed of a 20 kD protein, rather similar to spasmin. The ciliary rootlet or rhizoplast, is a cytoskeleton-like structure that originates from the basal body at the proximal end of a cilium. It extends proximally toward the cell nucleus. Rootlets are typically 80-100 nm in diameter and contain cross stria distributed at regular intervals of approximately 55-70 nm. 

So, the correct answer is option C

• Glyoxylate pathway: The glyoxylate pathway is a variation of the citric acid cycle that allows plants, bacteria, and fungi to utilize acetyl-CoA to produce carbohydrates. It is an important metabolic pathway for organisms that need to grow on acetate or fatty acids as their sole carbon source.


• Location: The glyoxylate pathway takes place in specialized organelles called Glyoxysomes.


• Glyoxysomes: Glyoxysomes are specialized peroxisomes found in plants and some fungi. They contain enzymes necessary for the glyoxylate cycle, including isocitrate lyase and malate synthase.


• Function: In the glyoxylate pathway, isocitrate lyase cleaves isocitrate into glyoxylate and succinate, which are then converted into malate. Malate can be further metabolized to produce carbohydrates, allowing organisms to utilize acetyl-CoA for growth and energy production.

• Chromoplast: Chromoplasts are plastids that contain pigments other than chlorophyll, giving fruits and flowers their vibrant colors. These pigments include carotenoids, which are responsible for the yellow, orange, and red hues in plants.


• Pericarp: The pericarp is the wall of a fruit, formed from the ovary wall and surrounding the seeds. Chromoplasts in the pericarp contribute to the color of fruits, making them visually appealing to animals for seed dispersal.


• Petals: Petals are the colorful, often modified leaves of a flower that attract pollinators. Chromoplasts in petals produce various pigments that help in attracting pollinators like bees, butterflies, and birds.


• Function: Chromoplasts help in photosynthesis, as well as in the synthesis and storage of pigments that give plants their color. They play a crucial role in attracting pollinators and seed dispersal in plants.

Centriole - The centrosome is made up of 2 centrioles which are right angled to each other and is composed of a protein known as tubulin.
It produces spindle apparatus at the time of cell division.
Each centriole has 9 peripheral groups of microtubules (triplet) with no central microtubules thus, this type of arrangement in centriole is called 9+0 pattern.

• Number of Fibres: There are a total of 9 longitudinal peripheral fibres found in a centriole.


• Structure: These fibres are arranged in a ring-like structure around the centriole.


• Function: The longitudinal peripheral fibres play a crucial role in the organization and functioning of the centriole during cell division.


• Microtubules: Each longitudinal peripheral fibre is composed of microtubules that help in maintaining the structural integrity of the centriole.


• Centrosome: Centrioles are a part of the centrosome, which is responsible for organizing the microtubules in the cell.

• Function: Ribosomes are responsible for protein synthesis in the cell.


• Structure: Ribosomes are composed of two subunits, a larger subunit, and a smaller subunit.


• Location: Ribosomes can be found floating freely in the cytoplasm or attached to the endoplasmic reticulum.


• Size: Ribosomes are the smallest cell organelles, ranging in size from 20-30 nanometers.


• Importance: Ribosomes are essential for the functioning of the cell as they are responsible for translating messenger RNA into proteins.

The non pigmented part of the chloroplast is the stroma. Lamellae of chloroplasts are known as thylakoids. A thylakoid is a membrane-bound compartment inside chloroplasts and cyanobacteria. They are the site of the light-dependent reactions of photosynthesis. Thylakoids consist of a thylakoid membrane surrounding a thylakoid lumen. Chloroplast thylakoids frequently form stacks of disks referred to as grana. Grana are connected by intergranal or stroma thylakoids, which join granum stacks together as a single functional compartment. These stroma do not possess any pigment.

Chloroplast is an organelle which is present in plant cells and green algae and carries out photosynthesis that converts light energy to chemical energy. It contains a pigment called chlorophyll and hence is green in color. This organelle is exclusively present in plant cells. 
On the other hand, mitochondria are organelles present in both plant and animal cells and their primary function is to regulate cellular metabolism and cellular respiration to provide the organism with energy. 
Hence, the correct answer is 'Both are present in animal cells'.

Thylakoids are tiny compartments found inside of chloroplasts. Their role is to help absorb sunlight in order for photosynthesis to occur. They contain all of the chlorophyll that the plant has which, in turn, allows for the absorption of sunlight. This is why the thylakoid is the site of the light dependent portion of photosynthesis, which is the portion that requires sunlight.

• Catalases: Catalases are enzymes found in the matrix of peroxisomes that are responsible for breaking down hydrogen peroxide into water and oxygen. This process helps to prevent the buildup of toxic hydrogen peroxide in the cell.


• Oxidases: Oxidases are another group of enzymes found in the matrix of peroxisomes. These enzymes play a role in the oxidation of various substrates, producing hydrogen peroxide as a byproduct, which is then broken down by catalases.

Therefore, the correct answer is option D: Catalases and oxidases are enzymes found in the matrix of peroxisomes.

• 70s ribosomes: These are ribosomes found in prokaryotic cells, chloroplasts, and mitochondria.


• Prokaryotic cells: These cells have 70s ribosomes, which are responsible for protein synthesis.


• Chloroplasts and mitochondria: These organelles also contain 70s ribosomes, which help in the synthesis of proteins within these organelles.


• Mitochondria: This organelle has its own 70s ribosomes, separate from the 80s ribosomes found in the nucleus.


• Function: The 70s ribosomes play a crucial role in translating genetic information into proteins, essential for the functioning of the cell.

A basal body (synonymous with basal granule, kinetosome and in older cytological literature with blepharoplast) is an organelle formed from a centriole, and a short cylindrical array of microtubules. It is found at the base of a eukaryotic undulipodium (cilium or flagellum) and serves as a nucleation site for the growth of the axoneme microtubules. Centrioles, from which basal bodies are derived, act as anchoring sites for proteins that in turn anchor microtubules within centrosomes, and are known as the microtubule organizing center (MTOC).

A mitochondrion is double membrane bound oval shaped organelle outer membrane and the inner membrane. But if the outer membrane is absent or less in mitochondria is called as mitoplast. It consists inner membrane and the matrix of a mitochondrion.

• Grana: Grana are stacks of disc-like structures called thylakoids within the chloroplast. They are the sites of light-dependent reactions in photosynthesis.


• Stroma Lamellae: Stroma lamellae are the extensions that connect grana in the chloroplast. They contain enzymes and molecules necessary for the light-independent reactions of photosynthesis.

• Grana: Grana contain chlorophyll and other pigments that capture light energy for photosynthesis. They also house the electron transport chain and ATP synthase for the production of ATP.


• Stroma Lamellae: Stroma lamellae provide a network for the exchange of materials between grana and the stroma of the chloroplast. They help in the synthesis of carbohydrates during the Calvin cycle.

• Photosynthesis: Grana and stroma lamellae play a crucial role in the process of photosynthesis by facilitating the light-dependent and light-independent reactions, respectively.


• Energy Production: The arrangement of grana and stroma lamellae allows for efficient energy production in the form of ATP and NADPH, which are essential for the synthesis of carbohydrates.

The mitochondria whether in plants or animals, contain complete genetic system including, a circular DNA, 70S ribosomes and all the enzymes necessary for synthesizing the DNA, and other RNAs.

• Starch: Aleuroplasts store starch as a reserve energy source in plant cells.


• Proteins: Some proteins are also stored in aleuroplasts for various cellular functions.

Aleuroplasts are specialized organelles found in plant cells that primarily store starch and proteins. They are responsible for storing and regulating the release of these substances as needed by the cell. While other organelles like oil bodies may store lipids, aleuroplasts are specifically known for their role in storing starch and proteins.