Cell Biology And Cell Division (MCQ) - Cell Cycle And Cell Division, Class 11, Biology - Class 11 MCQ

PPLO( pleuro pneumonia like organisms ) comes under the kingdom monerans . They lack cell wall and have size of 0.1 micrometre. That's why they are smallest.

Animal cells do not have chloroplasts. Chloroplasts work to convert light energy of the Sun into sugars that can be used by cells. The entire process is called photosynthesis and it all depends on the little green chlorophyll molecules in each chloroplast. Plants are the basis of all life on Earth.

Introduction:
The famous generalization "All cells are derived from pre-existing cells" is attributed to a scientist named Rudolf Virchow. This principle is known as the cell theory and is a fundamental concept in biology.
Rudolf Virchow and the Cell Theory:
- Rudolf Virchow was a German physician and pathologist who lived in the 19th century.
- He is considered one of the founders of modern pathology and is known for his significant contributions to medical science.
- In 1855, Virchow proposed the cell theory, which states that all living organisms are composed of cells and that cells only arise from pre-existing cells.
- This principle contradicted the prevailing belief at the time, which suggested that cells could arise spontaneously.
Supporting Evidence:
- Virchow's cell theory was supported by his observations and experiments.
- He studied cellular pathology and found that diseases were caused by abnormalities in cells.
- Virchow also examined cell division and observed that new cells formed through the replication of pre-existing cells.
- His work provided strong evidence for the idea that cells can only arise from pre-existing cells.
Significance of the Cell Theory:
- The cell theory revolutionized our understanding of biology and laid the foundation for modern cell biology.
- It provided a unifying concept that explained the organization and functioning of living organisms.
- The cell theory also contributed to advancements in medical science, as it highlighted the importance of studying cells in understanding diseases.
Conclusion:
Rudolf Virchow's generalization that "All cells are derived from pre-existing cells" has become a fundamental principle in biology. His observations and experiments led to the development of the cell theory, which revolutionized our understanding of living organisms.

The carbohydrate portion of the cell membrane:
- Contributes to the polycationic charge on the extracellular surface: This statement is false. The carbohydrate portion of the cell membrane does not contribute to the polycationic charge on the extracellular surface. The charge on the cell membrane is primarily determined by the presence of membrane proteins and lipids.
- Is 1% of the plasma membrane: This statement is true. The carbohydrate portion of the cell membrane makes up approximately 1% of the total plasma membrane. The majority of the plasma membrane is composed of lipids (around 50%) and proteins (around 50%).
- Is found primarily in the form of free saccharide groups: This statement is false. The carbohydrate portion of the cell membrane is not primarily found in the form of free saccharide groups. Instead, it is usually attached to lipids or proteins, forming glycolipids or glycoproteins.
- Has a symmetric distribution: This statement is false. The distribution of carbohydrates on the cell membrane is asymmetric. The carbohydrate chains are often longer on the extracellular side of the membrane and shorter on the cytoplasmic side.
Therefore, the correct answer is B: It is 1% of the plasma membrane.

Plasma membrane is a lipid bilayer in which the proteins, cholesterol and carbohydrates are incorporated which give it a mosaic-like appearance. The lipid bilayer renders the flexibility to the cell membrane. 

Mitosis is closely controlled by the genes inside every cell. Sometimes, this control can go wrong. If that happens in just a single cell, it can replicate itself to make new cells that are also out of control. These are cancer cells. They continue to replicate rapidly without the control systems that normal cells have. Cancer cells will form lumps, or tumours, that damage the surrounding tissues. Sometimes, cancer cells break off from the original tumour and spread in the blood to other parts of the body. When a tumour spreads to another part of the body it is said to have metastasized. They continue to replicate and make more tumours. These are called secondary tumours. Medicines that are used to treat cancer are sometimes aimed at killing cells that are rapidly dividing by mitosis. They inhibit the synthesis or function of DNA - this type of treatment is called chemotherapy. More modern medicines target specific cancers in different ways. Many inhibit the growth signals for that type of cell.

Middle lamella connects cell walls of  two adjacent cells. Pectic compounds are mainly present in the middle lamella.

The cell wall is derived from minute vesicles produced in the Golgi apparatus present in the cytoplasm. Hence, the cell wall is a secretory product of a plant cell cytoplasm. Immediately after nuclear division, the phragmoplast or cell plate appears across the equator of the cell. At the end of mitosis, granules arising from the Golgi complex arrange themselves on the equator of the cell. They then fuse to form the cell plate. The cell plate grows in thickness by the addition of new material from the complex and becomes cell wall.

In eukaryotic cells, nucleus is a membrane bound organelle. It is surrounded by double membrane. The nucleus communicates with the surrounding cell cytoplasm through the nuclear pores.

In his experiments, Hammerling grafted the stalk of one species of Acetabularia onto the foot of another species.

In all cases, the cap that eventually developed on the grafted cell matched the species of the foot rather than that of the stalk.

 In this example, the cap that is allowed to grow on the grafted stalk looks like the base species one... A. mediterranea

This experiment shows that the base is responsible for the type of cap that grows. The nucleus that contains genetic information is in the base, so the nucleus directs cellular development.

Centrosome is a small body located near the nucleus. It has a dense center and radiating tubules. During cell division (mitosis), the centrosome divides and the two parts move to opposite sides of the dividing cell and produce microtubules.

Explanation:
The nucleolus is a distinct region within the nucleus of a cell that is responsible for the production and assembly of ribosomes, the cellular structures responsible for protein synthesis. The size of the nucleolus can vary depending on the level of protein synthesis occurring in the cell.
- A: Protein synthesis is active: When protein synthesis is active, the nucleolus tends to be larger in size. This is because ribosomes are actively being produced and assembled in the nucleolus to facilitate protein synthesis.
- B: Protein synthesis is less: When protein synthesis is less active, the nucleolus tends to be smaller in size. This is because there is a reduced need for ribosome production and assembly.
- C: No protein synthesis occurs: If no protein synthesis occurs, it is unlikely that a nucleolus would be present in the cell. The nucleolus is specifically involved in the production and assembly of ribosomes, which are essential for protein synthesis.
- D: None of the above: The correct answer is A, as explained above.
In summary, the size of the nucleolus is large when protein synthesis is active, as it plays a crucial role in ribosome production and assembly.

Mitochondria, organelles specialized to carry out aerobic respiration, contain an inner membrane folded into cristae, which form two separate compartments: the inner membrane space and the matrix. The Krebs Cycle takes place in the matrix. The electron transport chain is embedded in the inner membrane and uses both compartments to make ATP by chemiosmosis. Mitochondria have their own DNA and ribosomes, resembling those of prokaryotic organisms.

Heart muscle cells have high number of mitochondria(5000 mitochondria per cell).That is because constantly beating heart works more than any other organ in our body. Heart cells have a high demand for ATP to keep pumping the blood 24 by 7.

In healthy cells, cytochrome c (Cyt c) is located in the mitochondrial intermembrane/intercristae spaces, where it functions as an electron shuttle in the respiratory chain and interacts with cardiolipin (CL)

Option ( c)  Elementary particles. 

 Explanation :- 

Oxysomes refers to small round structures present within the folds of the cristae of the inner mitochondrial membrane. They are called elementary particles or Parson’s particle or Fernandez-Moran particle or F0F1 – particles.

Mitochondria consists of about 104-105 oxysomes.

Answer:
The correct answer is A: Primary lysosomes.
Lysosomes are membrane-bound organelles found in animal cells. They contain digestive enzymes that break down various macromolecules, including proteins, lipids, carbohydrates, and nucleic acids. However, these enzymes need to be kept inactive within the lysosomes to prevent them from damaging the cell.
Primary lysosomes are newly formed lysosomes that contain inactive enzymes. They are formed through the process of packaging and sorting of enzymes in the Golgi apparatus.
Here is a detailed explanation of the options:
A. Primary lysosomes: These are newly formed lysosomes that contain inactive enzymes. They are the first stage in the formation of lysosomes and are responsible for storing the enzymes before they are activated.
B. Secondary lysosomes: These are lysosomes that have fused with other vesicles or endosomes containing material to be digested. They contain active enzymes and are involved in the degradation of cellular waste and foreign material.
C. Residual bodies: These are lysosomes that have completed the digestion process and contain undigested material. They are sometimes referred to as "garbage bags" of the cell.
D. Autophagosomes: These are double-membrane vesicles that sequester damaged organelles or cytoplasmic components for degradation. They fuse with lysosomes to form autolysosomes, where the enclosed material is digested.
To summarize, the correct answer is A: Primary lysosomes, as they are the lysosomes containing inactive enzymes.

Lysosome is called suicidal bag hence contains enzymes which are capable of dissolving cellular apparatus.

Lysosomes are small vesicles which are bounded by a single membrane and contain hydrolytic enzyme in form of crystalline granules.
These enzymes are digestive enzymes also termed as ‘acid hydrolases'. Lysosomes are called suicide bags because of presence of these large number of acid hydrolases in them.

To determine in which of the following cells the endoplasmic reticulum (ER) is absent, we need to analyze each option.
A: Kidney cells
- Kidney cells are responsible for filtering waste products from the blood and producing urine.
- These cells require the synthesis and transport of various proteins, which is facilitated by the endoplasmic reticulum.
- Therefore, the endoplasmic reticulum is present in kidney cells.
B: Liver cells
- Liver cells, or hepatocytes, perform a wide range of functions, including detoxification and protein synthesis.
- The endoplasmic reticulum, specifically the smooth ER, is involved in the detoxification process and the synthesis of lipids.
- Therefore, the endoplasmic reticulum is present in liver cells.
C: Mammalian mature erythrocytes
- Mammalian mature erythrocytes, or red blood cells, are specialized cells that transport oxygen to tissues.
- These cells lack a nucleus and most organelles, including the endoplasmic reticulum.
- The absence of endoplasmic reticulum allows for more space to accommodate hemoglobin, the protein responsible for oxygen transport.
- Therefore, the endoplasmic reticulum is absent in mammalian mature erythrocytes.
D: Mammalian eye cells
- The term "mammalian eye cells" is quite broad, as the eyes are composed of various cell types, including photoreceptor cells, lens cells, and retinal pigment epithelial cells.
- Each of these cell types has specific functions related to vision and may require the presence of endoplasmic reticulum for protein synthesis or other cellular processes.
- Without more specific information, it is not possible to definitively determine whether the endoplasmic reticulum is present or absent in mammalian eye cells.
Therefore, based on the given options, the correct answer is C: Mammalian mature erythrocytes where the endoplasmic reticulum is absent.

Microsomes are the structures formed when cells are broken up in the laboratory. Differential centrifugation can be used to separate them from other cellular debris. They are used to imitate the activity of the endoplasmic reticulum in a test tube. They are also used to perform experiments that require protein synthesis on a membrane thus aiding in understanding the process of protein formation on the endoplasmic reticulum. 

Glycosyl transferases are enzymes that catalyze the formation of the glycosidic linkage to form a glycoside. These enzymes utilize 'activated' sugar phosphates as glycosyl donors, and catalyze glycosyl group transfer to a nucleophilic group, usually an alcohol.

The Endoplasmic reticulum (ER) is a type of organelle found in eukaryotic cells that forms an interconnected network of flattened, membrane-enclosed sacs or tube-like structures know as cisternae. Hence it forms endoskeleton.

Microtubules are the structural component of cilia.
Centrioles play role in cell division.
Perioxisomes contain enzymes that break down long and branched fatty acid chains, amino acids, and polyamines.

A genome can be defined as a set of genes present in a cell or organism or also it can also be said as a haploid set of chromosomes in a cell. Basically, it is a complete set of DNA  which includes all the genes.

The carbohydrates which project out of the lipid bilayer in animal cell membrane are linked to:
- Lipids only
- Proteins only
- Peptidoglycan
- Both lipid & protein
Answer: D. Both lipid and protein

Janus green is a basic dye used in straining mitochondria

The outer membrane of mitochondria is less proteinaceous.

The outer membrane of mitochondria is a selectively permeable barrier that separates the interior of the mitochondria from the cytoplasm. It plays a crucial role in regulating the transport of molecules in and out of the mitochondria. Here are some key points explaining why the outer membrane is less proteinaceous:

- Composition: The outer membrane is composed of a phospholipid bilayer, similar to the plasma membrane of cells. It contains a variety of proteins that are involved in various functions, such as transport, metabolism, and signaling. However, compared to the inner membrane of mitochondria, the outer membrane has a lower protein content.
- Porins: One of the unique features of the outer membrane is the presence of porin proteins. These porins form channels that allow the passage of small molecules, such as ions and metabolites, across the membrane. The presence of porins contributes to the lower protein content of the outer membrane.
- Contact sites: The outer membrane of mitochondria is in close proximity to the endoplasmic reticulum (ER) and forms contact sites with it. These contact sites are regions where the membranes of the mitochondria and the ER are closely apposed. They play a role in lipid exchange and facilitate communication between the two organelles. The presence of contact sites further reduces the protein content of the outer membrane.
In summary, the outer membrane of mitochondria is less proteinaceous compared to the inner membrane. Its unique composition, including the presence of porins and contact sites with the ER, contributes to its lower protein content.

Mitochondrial outputs:
- ATP: Adenosine triphosphate is produced during cellular respiration in the mitochondria. ATP is the primary source of energy for cellular processes.
- CO₂: Carbon dioxide is a byproduct of cellular respiration. It is produced during the breakdown of glucose in the mitochondria.
- H₂O: Water is another byproduct of cellular respiration. It is formed as a result of the electron transport chain in the mitochondria.
Therefore, the correct answer is C: ATP, CO₂, H₂O.

The overcoat of the plasma membrane means phospholipids. And the function of the golgi apparatus is to synthesise lipids and proteins. Thus, it could be said that the overcoat of the plasma membrane is the handiwork of the golgi apparatus.