Mix Example - THE FUNDAMENTAL UNIT OF LIFE Questions in English

(N/A) Chromatin is the loose,thread-like form of $DNA$ and proteins found in the nucleus during interphase. When a cell prepares to divide,this chromatin condenses into thicker,distinct structures called chromatids. $A$ chromosome is the structural unit formed by one or two identical chromatids (sister chromatids) joined at the centromere,which serves to package and organize genetic material for cell division.

(N/A) When a cell has a higher water concentration than the surrounding medium,water moves out of the cell into the medium. This process is known as exosmosis,which causes the cell to shrink or become plasmolysed.
$(b)$ When a cell has a lower water concentration than the surrounding medium,water moves from the medium into the cell. This process is known as endosmosis,which causes the cell to swell or become turgid.
$(c)$ When a cell has an equal water concentration to its surrounding medium,there is no net movement of water across the cell membrane. The cell remains in an isotonic state,and its size and shape remain unchanged.

(N/A) Nucleus: It controls all cellular activities and development.
$(b)$ Golgi apparatus: It is responsible for packaging and dispatching materials synthesized in the endoplasmic reticulum.
$(c)$ Cell wall: It provides structural support and protection,allowing the cell to withstand hypotonic environments without bursting.
$(d)$ Cytoplasm: It is the jelly-like substance where many essential biochemical reactions occur.
$(e)$ Nucleoplasm: It is the fluid matrix present inside the nucleus.

(N/A) plant cell is characterized by the presence of a rigid cell wall,large central vacuole,and plastids. The differences between a plant cell and an animal cell are summarized in the table below:

Feature	Animal Cell vs Plant Cell
$1.$ Cell wall	Absent in animal cells; Present in plant cells.
$2.$ Plastids	Absent in animal cells; Present in plant cells.
$3.$ Vacuoles	Small or absent in animal cells; Large central vacuole present in plant cells.
$4.$ Centrioles	Present in animal cells; Absent in plant cells.

(N/A) An animal cell is a eukaryotic cell that lacks a cell wall and contains various membrane-bound organelles. Key components include:
$1$. Plasma membrane: The outer boundary of the cell.
$2$. Nucleus: The control center containing genetic material.
$3$. Cytoplasm: The jelly-like substance filling the cell.
$4$. Mitochondria: The powerhouse of the cell.
$5$. Endoplasmic Reticulum (Rough and Smooth): Involved in protein and lipid synthesis.
$6$. Golgi apparatus: Responsible for packaging and modifying proteins.
$7$. Lysosomes: Known as the suicide bags of the cell.
$8$. Ribosomes: Sites of protein synthesis.
$9$. Centrioles: Involved in cell division.

(N/A) The eukaryotic nucleus is a membrane-bound organelle that contains the cell's genetic material. It consists of a nuclear envelope,nucleolus,chromatin,and nuclear pores. $A$ nucleoid,on the other hand,is an irregularly shaped region within a prokaryotic cell that contains all or most of the genetic material.

Nucleus	Nucleoid
$(i)$ Nuclear membrane is present.	$(i)$ Nuclear membrane is absent.
$(ii)$ Nucleolus is present.	$(ii)$ Nucleolus is absent.
$(iii)$ Genetic material is enclosed within the nuclear envelope.	$(iii)$ Genetic material is not contained in any membrane-bound structure.
$(iv)$ Found in eukaryotic cells.	$(iv)$ Found in prokaryotic cells.

(N/A) The ribosomes, which are present in all active cells, are the sites of protein synthesis. Endoplasmic reticulum helps in transporting these proteins to various places. The smooth endoplasmic reticulum helps in the manufacture of fat and lipids, which, along with proteins, help in building the cell membrane, a process known as membrane biogenesis.

Smooth Endoplasmic Reticulum $(SER)$	Rough Endoplasmic Reticulum $(RER)$
$SER$ does not have ribosomal particles on its surface, hence it looks smooth. It helps in the manufacture of lipids and fat molecules.	$RER$ has particles of ribosomes on its surface. Ribosomes are the sites of protein synthesis.

(N/A) Initially,the dry apricots swell due to endosmosis (water enters the cells). When transferred to a sugar solution,they shrink due to exosmosis (water leaves the cells).
$(b)$ The $RBC$ will lose water to the surrounding hypertonic environment through osmosis,causing the cell to shrink (crenation).
$(c)$ The cell will lose its integrity and die,as the plasma membrane is essential for regulating the movement of substances in and out of the cell.
$(d)$ Boiling kills the cells of the Rhoeo leaves. Since the cells are dead,they cannot perform plasmolysis,and therefore,no change will be observed when sugar syrup is added.
$(e)$ The Golgi apparatus is responsible for packaging and modifying proteins and lipids. If it is removed,all vesicle formation,packaging,and secretion processes within the cell will stop.

(N/A) The three parts that differentiate a plant cell from an animal cell are as follows:
$1$. Cell Wall: It is a rigid outer covering present only in plant cells,providing structural support and protection.
$2$. Chloroplast: These are plastids containing chlorophyll,which are responsible for photosynthesis and are absent in animal cells.
$3$. Large Central Vacuole: Plant cells typically contain a large,permanent central vacuole that occupies most of the cell volume,whereas animal cells have either no vacuoles or very small,temporary ones.

(N/A) The organelle responsible for maintaining the turgidity and rigidity of mature plant cells is the $Vacuole$. In plant cells, large central vacuoles occupy up to $90\%$ of the cell volume. The cell sap contained within the vacuole exerts pressure against the cell wall, known as turgor pressure, which provides structural support and rigidity to the plant.

(B) The $Nucleus$ is called the brain of the cell because it contains the genetic material $(DNA)$ and controls all the metabolic activities and cellular functions of the cell.

(B) The cell membrane is a living structure composed of lipids and proteins that regulates the movement of substances in and out of the cell.
The cell wall is a non-living,rigid outer covering found in plant cells,fungi,and bacteria,primarily composed of cellulose,which provides structural support and protection.

(N/A) $(i)$ $Amoeba$ is a unicellular organism that constantly changes its shape by forming pseudopodia to move and capture food.
$(ii)$ $Nerve$ $cell$ (neuron) has a fixed,typical shape with a long axon and dendrites to facilitate the transmission of electrical impulses throughout the body.

(A) $(i)$ Papaya contains chromoplasts,which are colored plastids (other than green) that provide yellow,orange,or red pigments to fruits.
$(ii)$ Grass contains chloroplasts,which are green-colored plastids containing chlorophyll,essential for photosynthesis.

(B) The cell organelle that is generally small-sized in animal cells and large in plant cells is the $Vacuole$.
In plant cells, $Vacuoles$ are large, membrane-bound sacs that can occupy up to $90\%$ of the cell volume, providing turgidity and rigidity to the cell.
In animal cells, if present, $Vacuoles$ are either absent or very small in size.

(B) Whenever the cell is about to divide,i.e.,during cell division,the chromatin materials get organised into chromosomes. This condensation allows for the equal distribution of genetic material into daughter cells.

(A) Robert Hooke examined a thin slice of cork under a primitive microscope. He observed that the cork resembled the structure of a honeycomb consisting of many little compartments. He named these compartments '$cells$'.

(A) The cell was first observed by Robert Hooke in $1665$. He examined a thin slice of cork under a primitive microscope and observed that it consisted of many small,box-like compartments,which he termed 'cells'.

(N/A) cell is defined as the basic structural,functional,and biological unit of all living organisms.
In Latin,the word 'cellula' means 'a little room'.

(B) The smallest known cell is the $PPLO$ (Pleuro-Pneumonia Like Organism),also known as $Mycoplasma$.
It is approximately $0.1\, \mu m$ in diameter.
These organisms lack a cell wall,which allows them to change their shape and survive without oxygen.

(B) The largest known isolated single cell is the egg of an ostrich.
Its size is approximately $170\, mm \times 135\, mm$.

(B) The nerve cell (neuron) is the longest cell in the human body. These cells can reach lengths of up to $1 \ m$ or more,extending from the spinal cord to the extremities.

(N/A) Two examples of unicellular animals are $Amoeba$ and $Paramecium$. These organisms consist of a single cell that performs all essential life functions,such as respiration,nutrition,and reproduction.

(B) The two primary types of nucleic acids found in a cell are $DNA$ (Deoxyribonucleic acid) and $RNA$ (Ribonucleic acid).
$DNA$ serves as the genetic material that stores hereditary information.
$RNA$ is primarily involved in protein synthesis and gene expression.

(N/A) $RNA$ stands for Ribonucleic acid.
$DNA$ stands for Deoxyribonucleic acid.

(N/A) Prokaryotic cells are cells that lack a well-defined nucleus and membrane-bound organelles. Examples of organisms with prokaryotic cells include bacteria and blue-green algae (also known as cyanobacteria).

(B) Chromosomes are thread-like structures located inside the nucleus of animal and plant cells.
Each chromosome is made of protein and a single molecule of deoxyribonucleic acid $(DNA)$.
These proteins are primarily histone proteins,which help in the packaging of $DNA$ into compact structures.

(B) Genes are the functional units of heredity and are segments of $DNA$. These genes are physically located on the chromosomes,which are thread-like structures found within the nucleus of eukaryotic cells.

(B) In plants,the cell wall is primarily composed of cellulose,which provides structural support and rigidity to the plant cells.
In fungi,the cell wall is composed of chitin,a complex polysaccharide that is also found in the exoskeletons of arthropods.

(B) Vacuoles are membrane-bound organelles found in the cytoplasm of cells.
In plant cells,they are large and occupy a significant portion of the cell volume,providing turgidity and rigidity to the cell by maintaining internal pressure.
They also serve as storage sacs for various substances,including water,nutrients,and waste products.

(B) In prokaryotic cells,the genetic material is not enclosed by a nuclear membrane. This undefined nuclear region containing only nucleic acids is known as the nucleoid.

(N/A) The two cell organelles that possess a double membrane are the $Chloroplast$ and the $Mitochondria$. These organelles are unique because they contain their own $DNA$ and ribosomes,which supports the endosymbiotic theory.

(B) The cell organelles that lack a membrane are known as non-membrane-bound organelles.
Ribosomes are the primary example of such organelles,as they are composed of $RNA$ and proteins and are not enclosed by any lipid bilayer membrane.
Centrosomes are another example of non-membrane-bound organelles found in animal cells.

(A) The $Lysosome$ is a single membrane-bound cell organelle found in animal cells. It contains powerful digestive enzymes that help in the breakdown of waste materials and foreign substances within the cell.

(B) In the liver cells of vertebrate animals,the smooth endoplasmic reticulum $(SER)$ plays a crucial role in the detoxification of many poisons and drugs.

(A) Mature mammalian $RBCs$ (Red Blood Cells) lack both mitochondria and endoplasmic reticulum.
This adaptation allows them to carry more hemoglobin,thereby increasing their oxygen-carrying capacity.
They rely on anaerobic respiration for their energy requirements.

(A) Endocytosis is the cellular process by which cells ingest external materials,such as nutrients or fluids,by engulfing them within the plasma membrane.
This process involves the plasma membrane folding inward to form a vesicle that encloses the substance,which is then transported into the cytoplasm.

(B) Osmosis is a special case of diffusion.
It is defined as the net movement of water molecules from a region of higher water concentration (or higher water potential) to a region of lower water concentration (or lower water potential) through a selectively permeable membrane.
This process continues until equilibrium is reached.

(N/A) Yes, $I$ agree that a cell is the building unit of an organism.
$1$. Structural Basis: Just as bricks are the building blocks of a building, cells are the fundamental structural units of all living organisms.
$2$. Functional Basis: All life processes, such as metabolism, respiration, and reproduction, occur at the cellular level.
$3$. Organization: Cells organize to form tissues, which form organs, organ systems, and finally the complete organism. Therefore, the cell is the basic unit of life.

(B) The mitochondrion is known as the 'powerhouse of the cell' because it is the site of cellular respiration.
During this process,it oxidizes nutrients (food) to release energy.
This energy is stored and released in the form of $Adenosine$ $Triphosphate$ $(ATP)$,which is the energy currency of the cell.

(B) Plastids,specifically chloroplasts,contain pigments like chlorophyll that can trap solar energy.
This trapped energy is used to convert inorganic raw materials into chemical energy in the form of food,known as glucose,through the process of photosynthesis.
Since they are responsible for the production of food for the cell,they are referred to as the 'kitchens of the cell'.

(N/A) The endoplasmic reticulum $(ER)$ is called the transporting channel of the cell because it serves as a network of membranes that facilitates the transport of materials,particularly proteins and lipids,between various regions of the cytoplasm or between the cytoplasm and the nucleus.

(N/A) The movement of $CO_{2}$ into and out of the cell occurs through the process of diffusion,which is the spontaneous movement of a substance from a region of higher concentration to a region of lower concentration.
The movement of $H_{2}O$ into and out of the cell occurs through the process of osmosis,which is the movement of water molecules from a region of higher water potential to a region of lower water potential through a selectively permeable membrane.

(C) The plastid that stores starch,oils,and protein granules is known as the $Leucoplast$.
$Leucoplasts$ are primarily storage plastids that lack pigments.
Depending on the type of nutrient stored,they are further classified as $Amyloplasts$ (for starch),$Elaioplasts$ (for oils/fats),and $Aleuroplasts$ (for proteins).

(B) virus lacks its own metabolic machinery,such as ribosomes,enzymes,and energy-generating systems,which are necessary for protein synthesis and replication. Because it lacks these essential components,it must hijack the metabolic machinery of a living host cell to multiply.

(N/A) Chromosomes are thread-like structures located inside the nucleus of animal and plant cells. Each chromosome is made of protein and a single molecule of deoxyribonucleic acid $(DNA)$. The primary function of chromosomes is to carry genetic information from one generation to the next in the form of genes. They play a crucial role in cell division,heredity,variation,and evolutionary processes by ensuring that $DNA$ is accurately replicated and distributed to daughter cells.

(A) The cell organelle associated with the elimination of old and worn-out cells is the $Lysosome$.
$Lysosomes$ contain powerful digestive enzymes capable of breaking down all organic material.
When a cell gets damaged or old, $lysosomes$ may burst, and the enzymes digest their own cell, which is why they are often referred to as the '$suicide \text{ bags}$' of the cell.

(A) When a living plant cell is placed in a hypertonic solution,water moves out of the cell due to osmosis.
This loss of water causes the protoplast to shrink and pull away from the cell wall.
This specific phenomenon is known as Plasmolysis.

(B) The $Endoplasmic \text{ } Reticulum$ $(ER)$ is the cell organelle responsible for intracellular transport. It forms a network of membrane-bound tubules and vesicles that act as a transport system for materials, particularly proteins and lipids, between various regions of the cytoplasm.

(B) The functional unit of $DNA$ that carries genetic information is known as a $Gene$. Genes are specific segments of $DNA$ sequences that code for functional molecules,typically proteins,which determine the traits and characteristics of an organism.