Find the best tutors and institutes for Class 12 Tuition
Q12:
How is a cancerous cell different from a normal cell?
Solution :
Biological Basis of Cellular Transformation
The fundamental distinction between a normal cell and a cancerous cell lies in the regulation of the cell cycle and the mechanisms of homeostatic control. While normal cells operate under strict genetic governance, cancerous cells exhibit a breakdown in these regulatory checkpoints, leading to uncontrolled proliferation.
Comparative Analysis: Normal Cells vs. Cancerous Cells
| Characteristic | Normal Cell | Cancerous Cell |
|---|---|---|
| Contact Inhibition | Present: Cells stop dividing upon contact with neighbors. | Absent: Cells continue to divide, piling up to form tumors. |
| Cell Division Control | Strictly regulated by proto-oncogenes and tumor suppressor genes. | Unregulated; mutations in DNA lead to perpetual activation of cell cycle pathways. |
| Lifespan | Finite: Programmed cell death (apoptosis) occurs when the cell is damaged or aged. | Immortal: Escape apoptosis; they possess the ability to bypass telomere shortening. |
| Metastasis | None: Cells remain anchored in their tissue of origin. | Present: Cells lose adhesion properties and migrate to distant sites via blood or lymph. |
Visualization of Cellular Proliferation Dynamics
Mechanistic Differences in Signaling Pathways
The transformation is primarily driven by genomic instability [Per the Multi-hit Hypothesis of Carcinogenesis]:
- Contact Inhibition: In normal cells, cell-to-cell contact triggers inhibitory signals (e.g., via cadherins) that suppress $CDK$ (Cyclin-dependent kinase) activity, halting the cell cycle at the $G_1$ phase. Cancer cells exhibit defective signaling receptors, ignoring these chemical stop-signals.
- Apoptotic Evasion: Normal cells detect DNA damage via the $p53$ protein, which either initiates repair or triggers apoptosis. Cancerous cells often harbor mutations in the $p53$ gene, effectively disabling the cell's "suicide switch."
- Angiogenesis: Cancerous cells secrete factors such as $VEGF$ (Vascular Endothelial Growth Factor) to induce the growth of new blood vessels, securing a dedicated nutrient supply, a characteristic absent in homeostatic tissue environments.
Final Solution: Cancerous cells differ from normal cells primarily through the loss of contact inhibition, the evasion of programmed cell death (apoptosis), unregulated cellular proliferation driven by genetic mutations, and the capacity for metastasis (the ability to spread to secondary sites).
More Questions from Class 12 Biology Human Health and Disease EXERCISES
- Q1: What are the various public health measures, which you would suggest as safeguard against infectious diseases?
- Q1: What are the various public health measures, which you would suggest as safeguard against infectious diseases?
- Q2: In which way has the study of biology helped us to control infectious diseases?
- Q2: In which way has the study of biology helped us to control infectious diseases?
- Q3(a): How does the transmission of each of the following diseases take place? (a) Amoebiasis
- Q3(a): How does the transmission of each of the following diseases take place? (a) Amoebiasis
- Q3(b): How does the transmission of each of the following diseases take place? (b) Malaria
- Q3(b): How does the transmission of each of the following diseases take place? (b) Malaria
- Q3(c): How does the transmission of each of the following diseases take place? (c) Ascariasis
- Q3(c): How does the transmission of each of the following diseases take place? (c) Ascariasis
- Q3(d): How does the transmission of each of the following diseases take place? (d) Pneumonia
- Q3(d): How does the transmission of each of the following diseases take place? (d) Pneumonia
- Q4: What measure would you take to prevent water-borne diseases?
- Q4: What measure would you take to prevent water-borne diseases?
- Q5: Discuss with your teacher what does ‘a suitable gene’ means, in the context of DNA vaccines.
- Q5: Discuss with your teacher what does ‘a suitable gene’ means, in the context of DNA vaccines.
- Q6: Name the primary and secondary lymphoid organs.
- Q6: Name the primary and secondary lymphoid organs.
- Q7(a): The following are some well-known abbreviations, which have been used in this chapter. Expand each one to its full form: (a) MALT
- Q7(a): The following are some well-known abbreviations, which have been used in this chapter. Expand each one to its full form: (a) MALT
- Q7(b): The following are some well-known abbreviations, which have been used in this chapter. Expand each one to its full form: (b) CMI
- Q7(b): The following are some well-known abbreviations, which have been used in this chapter. Expand each one to its full form: (b) CMI
- Q7(c): The following are some well-known abbreviations, which have been used in this chapter. Expand each one to its full form: (c) AIDS
- Q7(c): The following are some well-known abbreviations, which have been used in this chapter. Expand each one to its full form: (c) AIDS
- Q7(d): The following are some well-known abbreviations, which have been used in this chapter. Expand each one to its full form: (d) NACO
- Q7(d): The following are some well-known abbreviations, which have been used in this chapter. Expand each one to its full form: (d) NACO
- Q7(e): The following are some well-known abbreviations, which have been used in this chapter. Expand each one to its full form: (e) HIV
- Q7(e): The following are some well-known abbreviations, which have been used in this chapter. Expand each one to its full form: (e) HIV
- Q8(a): Differentiate the following and give examples of each: (a) Innate and acquired immunity
- Q8(a): Differentiate the following and give examples of each: (a) Innate and acquired immunity
- Q8(b): Differentiate the following and give examples of each: (b) Active and passive immunity
- Q8(b): Differentiate the following and give examples of each: (b) Active and passive immunity
- Q9: Draw a well-labelled diagram of an antibody molecule.
- Q9: Draw a well-labelled diagram of an antibody molecule.
- Q10: What are the various routes by which transmission of human immuno-deficiency virus takes place?
- Q10: What are the various routes by which transmission of human immuno-deficiency virus takes place?
- Q11: What is the mechanism by which the AIDS virus causes deficiency of immune system of the infected person?
- Q11: What is the mechanism by which the AIDS virus causes deficiency of immune system of the infected person?
- Q12: How is a cancerous cell different from a normal cell?
- Q13: Explain what is meant by metastasis.
- Q13: Explain what is meant by metastasis.
- Q14: List the harmful effects caused by alcohol/drug abuse.
- Q14: List the harmful effects caused by alcohol/drug abuse.
- Q15: Do you think that friends can influence one to take alcohol/drugs? If yes, how may one protect himself/herself from such an influence?
- Q15: Do you think that friends can influence one to take alcohol/drugs? If yes, how may one protect himself/herself from such an influence?
- Q16: Why is that once a person starts taking alcohol or drugs, it is difficult to get rid of this habit? Discuss it with your teacher.
- Q16: Why is that once a person starts taking alcohol or drugs, it is difficult to get rid of this habit? Discuss it with your teacher.
- Q17: In your view what motivates youngsters to take to alcohol or drugs and how can this be avoided?
- Q17: In your view what motivates youngsters to take to alcohol or drugs and how can this be avoided?
CBSE Solutions for Class 12 Biology Human Health and Disease
Chapters in CBSE - Class 12 Biology
- Reproduction in Organisms
- Human Reproduction
- Reproductive Health
- Principles of Inheritance and Variation
- Molecular Basis of Inheritance
- Evolution
- Strategies for Enhancement in Food Production
- Microbes in Human Welfare
- Biotechnology: Principles and Processes
- Biotechnology and Its Applications
- Organisms and Populations
- Ecosystem
- Biodiversity and Conservation
- Environmental Issues
Top Tutors who teach Human Health and Disease
Top Tutor
Lekha Nagar, Nashik
10 yrs of
Exp
2 students
23 hrs of classes completed
400
per hour
Online Classes
Tutor's home
Taught 6 years in Junior College for class12 ( Science and Commerce stream ) as a Math teacher.
Top Tutor
Kuvempu Nagar, Bellary
20 yrs of
Exp
3 students
359 hrs of classes completed
400
per hour
Online Classes
Tutor's home
Teaching CBSE 12th Mathematics online and offline
Top Tutor
Shipra Sun City, Ghaziabad
20 yrs of
Exp
1000
per hour
Online Classes
Student's Home
Tutor's home
I have 20 years of experience in teaching classes like 9th,10th, 11th, and 12th for subjects like Physics, Chemistry, and Science. I will be providing a free demo class and can continue if satisfied. Marks above 90 % in Boards are Guaranteed.
Top Tutor
Sector-18, Faridabad
1 yrs of
Exp
7 students
1038 hrs of classes completed
600
per hour
Online Classes
Tutor's home
I have approximately 3 years of experience of teaching Mathematics across different boards including CBSE, IGCSE and state board in reputed schools like DPS International. I am post graduate in statistics and honors degree in mathematics from reputed universities like DU. I have helped many students to overcome their fear of Mathematics and Statistics. My aim is to develop a genuine love for the subject in students.
Maam is good and was able to resolve my queries. She is very calm explains the chapter thoroughly. It was just one class with her but we are going to have more in up coming days.
Top Tutor
Mulund West, Mumbai
10 yrs of
Exp
1 student
8 hrs of classes completed
700
per hour
Online Classes
Student's Home
Experienced and dedicated Science educator with a strong background in teaching Physics, ,Maths to Grade 12 students. Skilled in creating engaging lesson plans aligned with CBSE/ICSE/State Board curricula, fostering scientific curiosity, and using modern teaching aids such as smart boards, simulations, and lab experiments. Proficient in classroom management, differentiated instruction, and continuous student assessment. Committed to promoting STEM education and preparing students for board exams and competitive entrance tests.
Explanation for every chapter was on point and the notes given helped a lot and made easier to understand the concepts.
