Q.1 Define cell.
Cell is defined as the structural and functional unit of a living body.
Q.2 What is the composition of the cell membrane?
The cell membrane contains proteins (55%), lipids (40%), and carbohydrates (5%).
Q.3 Name the structural models of the cell membrane. Mention the accepted one.
- Danielli-Davson model
- Unit membrane model
- Fluid mosaic model. The fluid mosaic model is the accepted one.
Q.4 What are the layers of the cell membrane?
One central lipid layer and two outer protein layers.
Q.5 What is the characteristic feature of the lipid layer of the cell membrane? What is its advantage?
The lipid layer of the cell membrane is fluid in nature. Because of this, the portions of the cell membrane move from one point to another point along the surface of the cell. The advantage of this is that the materials dissolved in the lipid layer can move to all the areas of the cell membrane.
Q.6 Name the types of proteins present in the cell membrane.
- Integral proteins
- Peripheral proteins.
Q.7 What are the functions of proteins in the cell membrane?
- Provide structural integrity to the cell membrane
- Form the channels through which the water-soluble substances can diffuse
- Function as carrier proteins, which help in the transport of substances across the cell membrane
- Form the enzymes
- Function as the receptor proteins for the hormones.
Q.8 Name the carbohydrates present in the cell membrane.
- Glycoproteins – attached to proteins
- Glycolipids – attached to lipids.
Q.9 What is the functional importance of carbohydrates in the cell membrane?
Carbohydrate molecules are negatively charged. So, these molecules do not allow the negatively charged particles to move out of the cells. This helps in the maintenance of resting membrane potential.
Q.10 Name the cytoplasmic organelles which are bound with limiting membrane.
- Endoplasmic reticulum
- Golgi apparatus
- Centrosome and centrioles
- Secretory vesicles
Q.11 Name the cytoplasmic organelles which are not bound with limiting membrane.
Ribosomes and cytoskeleton.
Q.12 What is the endoplasmic reticulum?
The endoplasmic reticulum is the interconnected network of tubular and microsomal vesicular structures in the cytoplasm.
Q.13 Name the types of endoplasmic reticulum. Mention the function of each.
• Rough or granular endoplasmic reticulum – to which the ribosomes are attached.
It is concerned with:
- Synthesis of proteins in the cell
- Degradation of toxic substances.
• Smooth or a granular endoplasmic reticulum—to which the ribosomes are not attached. It is concerned with:
- Synthesis of lipids and steroids
- Storage and metabolism of calcium
- Degradation of toxic substances.
Q.14 What are the functions of the Golgi apparatus?
Processing, packing, labeling, and delivery of proteins and lipids.
Q.15 What are the functions of lysosomes?
- Degradation of macromolecules like bacteria
- Degradation of worn-out organelles
- Secretory function.
Q.16 What are the lysozymes?
Lysozymes are the hydrolytic enzymes present in lysosomes.
Q.17 What are peroxisomes and what are their functions?
Peroxisomes are the membrane limited vesicles derived from the endoplasmic reticulum. Peroxisomes are concerned with:
- Degradation of toxic substances like hydrogen peroxide
- Oxygen utilization
- Breakdown of excess fatty acids
- Acceleration of gluconeogenesis from fats
- Degradation of purine to uric acid
- Formation of myelin and bile acids.
Q.18 What is the other name of mitochondrion? What are the functions of mitochondrion?
The other name of mitochondrion is the ‘powerhouse’ of the cell.
Functions of mitochondrion:
- Production of energy
- Synthesis of ATP
- Initiation of apoptosis.
Q.19 What are the functions of ribosomes?
Ribosomes are concerned with protein synthesis. The ribosomes attached to the rough endoplasmic reticulum are involved in the synthesis of hormonal proteins, lysosomal proteins, and proteins of the cell membrane. The free ribosomes are concerned with the synthesis of protein in hemoglobin, and proteins present in peroxisomes and mitochondria.
Q.20 What is the cytoskeleton of the cell? What are the protein components of the cytoskeleton?
The cytoskeleton of the cell is a complex network of structures in various sizes present throughout the cytoplasm. Protein components of cytoskeleton:
- Intermediate filaments
Q.21 What are the functions of the cytoskeleton?
Cytoskeleton is concerned with:
- Determination of shape of the cell
- Stability of cell shape
- Cellular movements.
Q.22 What are microtubules? What are their functions?
Microtubules are tubular organelles without limiting membrane present in the cytoplasm. These tubules are formed by the tubulin molecules.
- Determine the shape of the cell
- Give structural strength to the cell
- Act like conveyer belts which allow the movement of granules, vesicles, protein molecules, and some organelles like mitochondria to different parts of the cell
- Form the spindle fibers which separate the chromosomes during mitosis
- Are responsible for the movements of centrioles and the complex cellular structures like cilia.
Q.23 What are microfilaments? What are their functions?
Microfilaments are nontubular thread like organelles present in the cytoplasm of the cell. The microfilaments in ectoplasm are made up of actin molecules and the filaments in endoplasm are made up of actin and myosin molecules.
- Give structural strength to the cell
- Provide resistance to the cell against the pulling forces
- Are responsible for cellular movements like contraction, gliding, and cytokinesis (partition of cytoplasm during cell division).
Q.24 List the functions of the nucleus.
- Control of all activities of the cell
- Synthesis of RNA
- Formation of ribosomal subunits
- Sending genetic instruction to the cytoplasm through mRNA for protein synthesis
- Control the cell division through genes
- Storage of hereditary information (in genes) and transformation of this information from one generation of the species to the next.
Q.25 What is DNA?
DNA (deoxynucleic acid) is a nucleic acid present in the nucleus and mitochondria of cells.
Q.26 What is RNA? What are the types of RNA?
RNA (ribonucleic acid) is a nucleic acid derived from DNA.
RNA is of three types:
- Messenger RNA
- Transfer RNA
- Ribosomal RNA.
Q.27 Define gene.
A gene is a portion of a DNA molecule that contains the message or code for the synthesis of a specific protein from amino acids.
Q.28 Define transcription and translation.
Transcription is the copying of genetic code from DNA to RNA. Translation is the process by which protein synthesis occurs in the ribosome of the cell under the direction of genetic instruction given by mRNA.
Q.29 What are growth factors? Name some growth factors.
Growth factors are proteins that act as cell signaling molecules like cytokines and hormones.
- Platelet-derived growth factor
- Colony-stimulating factors
- Nerve growth factors
- Insulin-like growth factors
- Epidermal growth factor
- Basic fibroblast growth factor
Q.30 What is apoptosis?
Apoptosis is the programmed cell death under genetic control.
Q.31 What is necrosis?
Necrosis is the uncontrolled and unprogrammed death of cells due to unexpected and accidental damage.
Q.32 Define cell junction.
The cell junction is the connection between the neighboring cells or the contact between the cell and the extracellular matrix.
Q.33 Classify cell junctions.
- Occluding junctions—tight junctions
- Communicating junctions – gap junctions and chemical synapse
- Anchoring junctions—adherence junctions, focal adhesions, desmosomes, and hemidesmosomes.
Q34 What are the proteins present in tight junctions?
- Tight junction membrane proteins or integral membrane proteins—occludin, claudin, and junctional adhesion molecules (JAMs)
- Scaffold (platform) proteins or peripheral membrane proteins or cytoplasmic plaque proteins—cingulin, symplekin, and ZO–1, 2, 3.
Q.35 What are the functions of tight junction?
- Strength and stability to the tissues
- Selective permeability
- Fencing function
- Maintenance of cell polarity
- Formation of the blood-brain barrier.
Q.36 What are connexons or connexins?
Connexons or connexins are the protein subunits present in gap junctions.
Q.37 What are the functions of gap junction?
- Allows the passage of small molecules, ions, and chemical messengers
- Helps in the propagation of action potential from one cell to another cell.
Q.38 What is the basic difference between passive transport and active transport?
The basic difference between the passive transport and active transport is that the passive transport does not require expenditure of energy and the active transport requires the expenditure of energy.
Q.39 What are the types of passive transport or diffusion?
- Simple diffusion
- Facilitated diffusion.
Q.40 Explain simple and facilitated diffusion briefly.
Simple diffusion occurs through the lipid layer and the protein layer of the cell membrane. The lipid-soluble substances like oxygen, carbon dioxide, and alcohol are transported through the lipid layer. The water-soluble substances like electrolytes are transported through the protein layer. The facilitated diffusion is also known as carrier-mediated diffusion because it involves the help of a carrier protein present in the cell membrane. The substances with larger molecules like glucose and amino acids are attached to the carrier protein and are transported into the cell.
Q.41 Name the factors affecting the diffusion of substances across the cell membrane.
- Permeability of cell membrane
- Concentration gradient or electrical gradient
- Solubility of the substances
- Thickness of cell membrane
- Size of the molecules and ions
- Charge of the ions.
Diffusion is directly proportional to the permeability of cell membrane, temperature, concentration gradient, or electrical gradient, and the solubility of the substances. It is inversely proportional to the thickness of the cell membrane, size of the molecules and ions, and charge of the ions.
Q.42 Name types of active transport. Explain them briefly.
- Primary active transport: In this, the energy is liberated from the breakdown of ATP. The electrolytes like sodium, potassium, calcium, hydrogen, and chloride are transported by this method.
- Secondary active transport: In this type of active transport, a carrier protein is involved in the transport of a substance like sodium-ion and this carrier protein is capable of transporting another substance along with the primary substance. The energy is derived from the process involved in the transport of the primary substance.
Q.43 Name the types of secondary active transport. Explain them briefly.
Co-transport: In this, along with the primary substance like sodium, the carrier protein carries another substance. Substances like glucose and amino acids are transported by this method
Counter transport: In this mechanism, the substances are carried in exchange for the primary substance like sodium. The different counter transport mechanisms are
sodium-calcium counter transport,
sodium–hydrogen counter transport,
sodium–magnesium counter transport,
sodium-potassium counter transport,
calcium–magnesium counter transport,
calcium–potassium counter transport,
chloride–bicarbonate counter transport and
chloride–sulfate counter transport.
Q.44 What is bulk flow? Give example.
The movement of a large number of molecules of a substance in bulk along the concentration gradient is known as bulk flow. An example is the diffusion of respiratory gases across the respiratory membrane.
Q.45 Define and classify endocytosis.
Endocytosis is the process by which the larger molecules (which cannot enter the cell by means of active or passive transport) are transported into the cell. Endocytosis is of two types: pinocytosis and phagocytosis.
Q.46 What is pinocytosis? Give example.
The movement of larger particles by means of evagination of the cell membrane is called pinocytosis. It is otherwise known as ‘cell drinking’.
Example: Transport of macromolecules like bacteria and antigens.
Q.47 What is phagocytosis? Give example.
The process by which the particles larger than the macromolecules are engulfed into the cells is called phagocytosis. It is also known as ‘cell eating’.
Example: Transport of larger bacteria, larger antigens, and other larger foreign bodies inside the cell.
Q.48 Name the cells which show phagocytosis.
Neutrophils, monocytes and tissue macrophages.
Q.49 Define homeostasis.
The maintenance of a constant internal environment is known as homeostasis.
Q.50 What are the mechanisms involved in the homeostatic control system? Explain them briefly.
The homeostatic control system is mainly by the feedback mechanisms:
- Negative feedback: If the activity of a particular system increases, it will be immediately regulated by reduction (example—thyroxin secretion). The negative feedback controls most of the homeostatic mechanisms.
- Positive feedback: When the activity of a particular system increases, it will be further increased (examples—formation of prothrombin activator during coagulation, secretion of oxytocin during milk ejection reflex and the pain produced during labor). Positive feedback is less common than the negative feedback. However, it has its own significance, particularly during emergency conditions.
Q.51 What is pH?
The pH is the expression of hydrogen ion concentration.
Q.52 What is the normal pH of ECF?
The normal pH of ECF is 7.4. It varies between 7.38 and 7.42 in physiological conditions.
Q.53 How is the pH of ECF and plasma determined?
To determine the pH of ECF, the concentrations of bicarbonate ions and carbon dioxide dissolved in the fluid are measured. The pH is calculated by using the Hendersön-Hasselbalch equation. The pH of plasma is determined by pH meter.
Q.54 What are the mechanisms which regulate acid-base balance?
- Blood buffer system
- Respiratory mechanism
- Renal mechanism.
Q.55 What are the buffer systems in the body?
- Bicarbonate buffer system
- Phosphate buffer system
- Protein buffer system.
Q.55 What is the basic mechanism involved in the regulation of acid-base balance by the respiratory system?
The respiratory system regulates acid-base balance by regulating carbon dioxide content in the blood.
Q.57 What is the basic mechanism involved in the regulation of acid-base balance by the kidney?
The kidney regulates acid-base balance by secretion of hydrogen ions and retention of bicarbonate ions.
Q.58 What are the disturbances of acid-base status?
- Acidosis: When hydrogen ion concentration increases, it leads to a reduction in pH. It is called acidosis.
- Alkalosis: When hydrogen ion concentration decreases, it leads to an increase in pH. It is known as alkalosis.
Q.59 Classify acidosis. Explain briefly.
Respiratory acidosis that occurs during respiratory disturbances. This is due to the increase in the partial pressure of carbon dioxide above 60 mm Hg in the arterial blood.
Metabolic acidosis that occurs during metabolic disturbances. It is due to the excessive accumulation of organic acids like lactic acid, acetoacetic acid, and beta hydroxyl butyric acid.
Q.60 Name some conditions when respiratory acidosis occurs.
Respiratory acidosis occurs in conditions leading to hypoventilation like:
- Airway obstruction (as in bronchitis)
- Lung diseases (like fibrosis)
- Respiratory center depression (by anesthetics, sedatives, etc.)
- Extrapulmonary thoracic diseases (like kyphosis and scoliosis)
- Neural diseases (poliomyelitis)
- Paralysis of respiratory muscles.
Q.61 Name some conditions when metabolic acidosis occurs.
- Lactic acidosis (as in circulatory shock)
- Ketoacidosis (as in diabetes mellitus)
- Uric acidosis (as in renal failure)
- Acid poisoning
- Renal tubular acidosis
- Loss of excess of bicarbonate ions (as in diarrhea).
Q.62 What are the types of alkalosis? Explain briefly.
- Respiratory alkalosis that occurs during respiratory disturbances.
It is due to the reduction in the partial pressure of carbon dioxide (< 20 mm Hg) in arterial blood.
- Metabolic alkalosis that occurs during metabolic disturbances.
It is due to the excessive loss of hydrogen ions from the body.
Q.63 Name some conditions when respiratory alkalosis occurs.
Hyperventilation is the primary cause of loss of excess carbon dioxide from the body leading to respiratory alkalosis. Hyperventilation occurs in hypoxic conditions, cerebral disturbances, and psychological and emotional trauma.
Q.64 Name some conditions when metabolic alkalosis occurs.
Metabolic alkalosis is due to loss of excess hydrogen ions that occurs in:
- Vomiting and diarrhea
- Endocrine disorders (Cushing’s syndrome, Conn’s syndrome)
- Diuretic therapy.
Q.65 The intracellular fluid has more sodium content than potassium. Is this statement correct?
No, it is the other way around, i.e. intracellular fluid has more potassium content than sodium.
Q.66 Give a brief description of the chromosome.
Chromosomes are fine threadlike structures forming the chromatin in the nucleus, and are made up of specific tiny structures called genes. The various hereditary peculiarities of the cell are passed on from one generation to another by the chromosomes through the genes of which the chromosomes are composed of.
Q.67 What is the number of chromosomes in somatic cells of human being?
There are 46 number of chromosomes, i.e. 22 pairs of somatic chromosomes and one pair of sex chromosomes.
Q.68 What is the difference between mitotic and meiotic cell division?
In mitotic cell division, the number of chromosomes remains the same, whereas in meiotic cell division the number of chromosomes is halved.
Q.69 Name the various phases in the mitotic division of a cell.
These are interphase, prophase, metaphase, cleavage stage, anaphase, and telophase.
Q.70 What is DNA composed of?
DNA has phosphoric acid (deoxyribose) and four nitrogenous bases, i.e. two purine (adenine and guanine) and two pyrimidines (thymine and cystosine).