Test: Cytoplasm - 2 - Grade 12 MCQ

A eukaryotic cell has DNA in nucleus as well as cell organelles like mitochondria and chloroplasts. The DNA in cell organelles resembles prokaryotic DNA. These organelles (mitochondria and chloroplasts) not only have DNA but also their own protein synthesis machinery. These organelles are double membrane-bound and can divide through fission independent of nuclear division. Thus these cell organelles are semi-autonomous.

• Endoplasmic reticulum is a complex network of membrane bounded tubules.
• They are classified as smooth and rough endoplasmic reticulum.
• Rough endoplasmic reticulum has ribosomes attached to their surface and acts as site of protein synthesis.
• Rough endoplasmic reticulum is connected by nuclear membrane at one end and Golgi apparatus on the other end.

Chloroplasts are the site of photosynthesis.So, the end product of photosynthesis involves releasing of oxygen. As chloroplast is the site so oxygen is released from there.

Lysosomes are the small single membrane-bound organelle formed by Golgi apparatus and are rich in hydrolytic enzymes. They are polymorphic and may be of following types:
(a) Primary lysosomes are the newly formed.
(b) Hetero lysosomes are the digestive vacuoles, produced by fusion of primary lysosome and phagosomes.
(c) Residual lysosomes are the lysosomes having undigested materials.
(d) Autophagic lysosomes perform autophagy or autolysis.

They contain acid hydrolases which can digest proteins, nucleic acids, lipids and carbohydrates.

Answer:
According to the question, lysosomes are abundantly found in phagocytic cells. Here is a detailed explanation:
Phagocytic cells:
- Phagocytic cells are a type of immune cells that have the ability to engulf and digest foreign particles, such as bacteria and viruses.
- These cells play a crucial role in the body's defense against infections and diseases.
- Phagocytic cells include macrophages, neutrophils, and dendritic cells.
- They have abundant lysosomes, which are responsible for the digestion and breakdown of ingested particles.
Lysosomes:
- Lysosomes are membrane-bound organelles found in most animal cells.
- They contain digestive enzymes that help break down various biological materials, including proteins, carbohydrates, and lipids.
- Lysosomes are involved in intracellular digestion, the recycling of cellular components, and the defense against pathogens.
- They also play a role in autophagy, a process that removes damaged or unnecessary cellular components.
- Lysosomes are formed by the fusion of vesicles containing enzymes with the endocytic vesicles or Golgi apparatus.
Conclusion:
In summary, lysosomes are abundantly found in phagocytic cells, which are responsible for engulfing and digesting foreign particles. These cells play a crucial role in the immune response and defense against infections.

• They are absent in RBCs, sperm cell of Pteridophytes and Bryophytes.
• Golgi apparatus is freely distributed in plant cells and in animal cells fluid filled sac like structures called cisternae that pile parallel to each other to form Golgi bodies.
• There are three main components, namely, cisternae, tubules and vesicles.

Lysosome containing bone cells are called as osteoclasts. It is involved in maintenance and repair, and remodeling of bones of the vertebral skeleton. This process is known as bone resorption.

Chemical modification of substances like glycosidation of proteins and lipids occur in:
Golgi body:
- The Golgi body is an organelle involved in the modification, sorting, and packaging of proteins and lipids.
- It consists of a series of flattened sacs called cisternae.
- Within the Golgi body, enzymes catalyze various chemical reactions, including glycosidation, where carbohydrates are added to proteins and lipids.
- Glycosidation plays a crucial role in protein folding, stability, and cell-cell recognition.
Endoplasmic reticulum:
- The endoplasmic reticulum is another organelle involved in protein synthesis and modification.
- It consists of a network of tubules and sacs.
- The rough endoplasmic reticulum (RER) is studded with ribosomes and is responsible for protein synthesis.
- The smooth endoplasmic reticulum (SER) is involved in lipid synthesis and detoxification.
Lysosome:
- Lysosomes are organelles involved in the degradation and recycling of cellular waste materials.
- They contain various hydrolytic enzymes that break down proteins, lipids, nucleic acids, and carbohydrates.
- While lysosomes are not directly involved in glycosidation, they play a role in the degradation of glycosidated proteins and lipids.
Ribosome:
- Ribosomes are cellular structures involved in protein synthesis.
- They are made up of RNA and proteins and can be found either free in the cytoplasm or attached to the rough endoplasmic reticulum.
- Ribosomes are not directly involved in the chemical modification of proteins and lipids.
In conclusion, the chemical modification of substances like glycosidation of proteins and lipids primarily occurs in the Golgi body. The Golgi body is responsible for adding carbohydrates to proteins and lipids, playing a crucial role in their function and recognition. While other organelles like the endoplasmic reticulum and lysosomes have their own roles in protein and lipid metabolism, they are not directly involved in glycosidation.

Endoplasmic reticulum are made up of three kinds of structure, cisternae, tubules and vesicles.
Cisternae are found in cells actively involved in protein synthesis.Tubules are common in cells involved in lipid and sterol syntheis.Vesicles are found in pancreatic cells and spermatocytes.
Smooth endoplasmic reticulum when observed under a microscope give the apperance of smooth tubular structure.Smooth ER are function in the synthesis of lipids and steriods.

Eukaryotic cells are more complex than prokaryotic cells and are found in a great many different forms. The nucleus contains most of the genetic material (DNA) of the cell. Additional DNA is in the mitochondria and (if present) chloroplasts.

Smooth E.R. of animal cell does not synthesize:
- Cholesterol: The smooth endoplasmic reticulum (ER) of animal cells is involved in the synthesis of lipids, including cholesterol. Therefore, the statement that smooth ER does not synthesize cholesterol is incorrect.
- Phospholipid: The smooth ER is also involved in the synthesis of phospholipids, which are essential components of cell membranes.
- Saturated fatty acid: The smooth ER is responsible for the synthesis of saturated fatty acids, which are important for the production of membrane lipids and energy storage.
- Unsaturated fatty acid: The smooth ER is also involved in the synthesis of unsaturated fatty acids, which play a crucial role in maintaining the fluidity of cell membranes and are essential for various cellular processes.
Therefore, the correct answer is d. Unsaturated fatty acid. The smooth ER of animal cells does synthesize unsaturated fatty acids.

Option (c)  E. R is the correct answer. 

Explanation:-

Endoplasmic reticulum ( ER) is a system of membrane - lined channels found in all eukaryotic cells except mature     erythrocytes. It constitutes more than  30-60 percent of total cell membranes. It provides protein and lipid to form the structure of cell membrane.

Answer:
The oxysomes of mitochondria are primarily concerned with oxidative phosphorylation. Here is a detailed explanation of this process:
Oxidative Phosphorylation:
1. Oxidative phosphorylation is the final step in cellular respiration, where ATP (adenosine triphosphate) is produced using energy derived from the oxidation of nutrients.
2. It takes place in the inner mitochondrial membrane, specifically in the cristae, which are the folded structures within the mitochondria.
3. The oxysomes, also known as the electron transport chain, are embedded within the inner mitochondrial membrane and are responsible for generating ATP.
4. The oxysomes consist of protein complexes and coenzymes that work together to transfer electrons from NADH and FADH2 to molecular oxygen, creating a proton gradient across the inner mitochondrial membrane.
5. The energy from this proton gradient is then used by ATP synthase, which is also embedded in the inner membrane, to produce ATP through a process called chemiosmosis.
To summarize, the oxysomes of mitochondria play a crucial role in oxidative phosphorylation, which is the process responsible for generating ATP, the main source of energy for cellular activities.

Ribosomes are present on the surface of the endoplasmic reticulum.
Ribosomes are responsible for the synthesis of proteins. 

• Vacuoles are fluid filled membrane bound sacs.
• They consist of water and sap consisting of minerals, sugars, amino acids and proteins etc.
• The function of vacuoles differs from one organism to other.
• Vacuoles in plants occupy most of the cell because they act as storage units of cells in plants.

Golgi components are bound by a single unit membrane and its series forms Golgi apparatus. The Golgi apparatus is involved in proteins secretion, the formation of the lysosome, synthesis of cellulose and hemicellulose etc.

The Golgi apparatus in the process of spermatogenesis is responsible for the formation of the acrosome. The acrosome is an organelle that develops over the anterior half of the head in the spermatozoa (sperm cells) of many animals. It is a cap-like structure derived from the Golgi apparatus. The acrosome contains digestive enzymes (including hyaluronidase and acrosin) that break down the outer membrane of the egg and allow the sperm to penetrate and fertilize the egg.

The tail of the sperm, also known as the flagellum, is formed from the centrioles, not the Golgi apparatus. The head of the sperm, which contains the genetic material, is formed from the nucleus. There is no such thing as a 'myeloid piece' in the sperm cell structure.
Correct answer is D.

Lysosomes contain acid hydrolase enzymes that break down waste materials and cellular debris. They can be described as the stomach of the cell. Lysosomes digest excess or worn-out organelles, food particles, and engulfed viruses or bacteria. The membrane around a lysosome allows the digestive enzymes to work at the pH they require. At pH 5, the lysosomal enzymes remain active and this pH is best suited for enzyme.

Golgi body is the series of flattened stacks which has two faces cis face towards the ER side and trans face opposite of ER. The main function of Golgi complex is the packaging of materials for secretion. The Golgi apparatus is a major collection and dispatch station of protein products received from the endoplasmic reticulum (ER). The Golgi apparatus is also involved in lipid transport and lysosome formation. It also involved in the synthesis of cellulose and hemicellulose.

The cell organelles having abundance of oxidizing enzymes is:
Mitochondria
- Mitochondria are known as the powerhouse of the cell because they generate most of the cell's energy in the form of adenosine triphosphate (ATP) through a process called oxidative phosphorylation.
- Oxidative phosphorylation involves the transfer of electrons from electron donors to electron acceptors through a series of redox reactions. This process occurs in the inner membrane of the mitochondria.
- The inner membrane of the mitochondria contains numerous enzymes, such as the electron transport chain and ATP synthase, which are involved in oxidative phosphorylation.
- These enzymes facilitate the transfer of electrons and the production of ATP by utilizing oxidizing enzymes.
- Oxidizing enzymes, such as cytochrome c oxidase and succinate dehydrogenase, play a crucial role in the electron transport chain by accepting electrons from electron carriers and passing them along to the next component in the chain.
- The abundance of oxidizing enzymes in mitochondria allows for efficient ATP production and energy generation in the cell.
In conclusion, mitochondria are the cell organelles with an abundance of oxidizing enzymes. These enzymes are essential for the process of oxidative phosphorylation and the production of ATP, which is crucial for cellular energy metabolism.

Packaging of materials for secretion
The main function of the Golgi apparatus is to modify, sort and package the macromolecules that are synthesized by the cells for secretion purposes or for use within the cell. 

Lysosomes are known as polymorphic cell organelles. Actually polymorphism is the occurrence in several different shapes particularly in reference to species or genetic variation. Lysosomes occur in more then one forms inside the cell.

The polymorphism of lysosomes can be explained on the basis of the types of lysosomes:

1.Primary lysosomes: They are small, newly formed structures formed in golgi apparatus, and they contain inactive enzymes.

2.Secondary lysosomes: They are formed when phagosomes fuse with already present primary lysosomes. Unlike primary lysosomes, they have enzymes against the material which is to be digested, and this is the function of lysosome.

3.Residual bodies:They are formed from digestive and autophagic vacuoles and contains undigested materials

4.Autophagic vacuoles:They are formed by union of primary lysosome around dead/dead organelles. and digest them by autodigestion.

Functional unit of protein synthesis is Polysome.
Definition:
- Polysome is a group of ribosomes that are simultaneously translating a single mRNA molecule.
- It consists of multiple ribosomes that are attached to a single mRNA molecule.
Explanation:
- Protein synthesis, also known as translation, occurs in the cytoplasm of the cell.
- The main steps of protein synthesis include transcription, where the DNA sequence is transcribed into mRNA, and translation, where the mRNA is used as a template to synthesize proteins.
- During translation, ribosomes play a crucial role in synthesizing proteins by reading the mRNA codons and linking amino acids together to form a polypeptide chain.
- In some cases, multiple ribosomes can attach to a single mRNA molecule, forming a polysome or polyribosome.
- The ribosomes in a polysome work simultaneously to translate the mRNA sequence into proteins.
- This allows for efficient and rapid protein synthesis, as multiple ribosomes can work on different sections of the mRNA molecule at the same time.
- Polysomes are commonly found in cells that require high levels of protein production, such as rapidly dividing cells or cells involved in protein secretion.
- Polysomes are dynamic structures that can disassemble and reassemble depending on the cellular needs.
Conclusion:
- The functional unit of protein synthesis is the polysome, which consists of multiple ribosomes attached to a single mRNA molecule.
- Polysomes allow for efficient and simultaneous translation of the mRNA sequence into proteins.

The main source of cellular membranes is the endoplasmic reticulum. Smooth endoplasmic reticulum is located towards the cell membrane produces and transports lipid molecule and the cell membrane is made up of phospholipid bilayer structure. Thus E.R. provides a backbone to the cell membrane.

The presence of mitochondria in different types of organisms:
- Aerobic organism only:
Mitochondria are commonly found in aerobic organisms, which require oxygen for their metabolic processes. These organisms include animals, plants, and fungi.
- Obligate anaerobic organism:
Obligate anaerobes are organisms that cannot survive in the presence of oxygen. Since mitochondria play a crucial role in aerobic respiration, they are not present in obligate anaerobes.
- Aerobic and obligate anaerobic organism:
Some organisms, known as facultative anaerobes, are capable of surviving in environments with or without oxygen. In these organisms, mitochondria are present but may not be actively functioning when oxygen is not available.
- Angiosperm only:
Angiosperms are flowering plants, and they do have mitochondria. However, mitochondria are not exclusive to angiosperms and are present in other types of plants as well.
In conclusion:
Mitochondria are present in aerobic organisms and facultative anaerobes that can survive in both aerobic and anaerobic conditions. They are not found in obligate anaerobes, which cannot tolerate the presence of oxygen. Additionally, while mitochondria are present in angiosperms, they are not exclusive to this group of plants.

ATPase activity occurs in:
- Head of F1-particle: The head of the F1-particle is where the ATPase activity takes place. This is the catalytic domain of the ATP synthase enzyme and is responsible for the hydrolysis of ATP to ADP and inorganic phosphate.
- Stalk of F1-particle: The stalk acts as a connector between the F1 and F0 subunits of the ATP synthase. It does not directly participate in the ATPase activity.
- Base of F1-particle: The base of the F1-particle is involved in the binding and release of ATP and ADP. It is not directly involved in the ATPase activity.
- All the above: The correct answer is actually D, as all three parts mentioned (head, stalk, and base) are involved in different aspects of the ATPase activity. The head is the main site of ATP hydrolysis, while the stalk and base are important for the overall structure and function of the ATP synthase enzyme.
Therefore, the correct answer is D: All the above.

The nuclear membrane originates from  Endoplasmic Reticulum.
It is formed by the fusion of ER elements during the telophase of cell division.
The nuclear membrane envelops the nucleoplasm of the cell and acts as a barrier between the nuclear DNA and the cytoplasm. The composition of the nuclear membrane network is complex and incompletely understood, but it provides a structural framework to support and protect the nucleus.

Ribosomes are cell organelles that are formed of two subunits. Cytosolic eukaryotic ribosomes (80S) are made up of 60S and 40S subunits, while prokaryotic ribosomes (70S) are made up of 50S and 30S subunits.
They are also capable of forming polyribosomes during which many ribosomes are attached to mRNA. The purpose of ribosomes moving on mRNA is to synthesise proteins i.e., translation. Indeed, ribosomes have a very direct role in protein synthesis.

So, the correct answer is 'Have no role in protein synthesis'.

• The outermost layer of the cell envelope is called as the glycocalyx 
• The cell wall determines the shape of the cell and provides a strong structural support
• Plasma membrane is selectively permeable in nature and interacts with the outside world.