Class 12 Biology Chapter 7 Human Health and Disease

Key Concept: Barrier Functions

b) Stomach Acid

[Solution Description] The stomach secretes gastric acid, which maintains a low pH around 1.5 to 3.5. This acidic environment is hostile for many bacteria and prevents their growth, thus acting as an important physiological barrier in innate immunity.

Key Concept: Carcinogen Types, Cancer Detection and Diagnosis

c) Chemical carcinogens, inducing characteristic cellular aberrations

[Solution Description] Histopathological examination involves analyzing tissue samples microscopically to identify cellular abnormalities indicative of cancerous transformations. Chemical carcinogens often cause morphological changes at the cellular level, such as atypical nuclei or disrupted cell architecture, making them detectable via this method.

Key Concept:Long-term Consequences

b) Heavy drinking in adulthood
[Solution Description] Adolescents using alcohol heavily are prone to continue this pattern into adulthood, often resulting in heavy drinking habits. This continuity could lead to persistent alcohol dependency and related health problems throughout their lives.

Key Concept:Withdrawal Management, Social Consequences

c) To ensure safety and address severe symptoms preventing societal disruptions
[Solution Description]
Comprehensive medical supervision during withdrawal is crucial to manage potentially life-threatening physical symptoms such as seizures or severe dehydration. Medical professionals provide necessary interventions, ensuring safety throughout the process. Moreover, addressing psychological symptoms like anxiety and depression with appropriate support prevents relapse. Without supervision, adolescents are vulnerable to social consequences, including disrupted education and strained relationships, due to unmanaged symptoms affecting their behavior and decision-making.

Key Concept:Role of T-lymphocytes

c) They assist B cells in antibody production
[Solution Description] T-lymphocytes are integral to cell-mediated immunity. They assist B cells in antibody production and help activate other immune cells through their signaling molecules.

Key Concept:Disease Impact

b) By eroding cartilage and bone
[Solution Description] In Rheumatoid arthritis, the immune system erroneously targets the synovium—the lining of the membranes that surround the joints. This attack leads to inflammation, causing joint damage, pain, stiffness, and reduced mobility.

Key Concept:Antibody Type

c) IgE
[Solution Description] The immune response involves different types of antibodies. During allergic reactions, IgE antibodies are specifically involved, as stated in the syllabus.

Key Concept:Complex Scenario Evaluation, Psychological Analysis

b) Peer pressure leading to drug/alcohol abuse
[Solution Description] The student’s shift in behavior aligns with the symptoms of drug/alcohol abuse, as mentioned in the syllabus. The combination of academic decline, isolation, and aggression are warning signs. While all options may seem plausible, peer pressure coupled with excessive use can lead to reckless behaviors.

Key Concept:Direct Benefits

b) Improving concentration and reducing stress
[Solution Description] Practicing yoga regularly can improve concentration and reduce stress levels by promoting mindfulness and relaxation techniques.

Key Concept:Metastasis Mechanism

b) Via blood circulation
[Solution Description] Cancer cells commonly metastasize through the bloodstream or lymphatic system, allowing them to travel to distant locations in the body.

Key Concept:Medical Complications, Psychological Effects

c) Contracting hepatitis B and psychological dependence
[Solution Description] Chronic substance use through intravenous methods often leads to infections due to needle sharing. One of the severe health risks includes contracting diseases such as AIDS or hepatitis B. The psychological aspect involves developing a strong dependency on the substance, leading to addiction.

Key Concept:Long-term Effects, Real-world Application

b) It helps in reducing the risk of developing chronic mental health issues.
[Solution Description] Early intervention provides adolescents with the necessary tools and support to address potential substance use issues before they escalate. It aids in developing coping mechanisms, resilience, and awareness, leading to improved long-term mental health outcomes. By intervening early, psychological complications such as anxiety, depression, or addiction can be mitigated.

Key Concept:Carcinogens

c) Tobacco smoke
[Solution Description] Tobacco smoke is a well-known chemical carcinogen that contributes to the development of cancer in humans.

Key Concept:Barrier Types

d) Genetic factors
[Solution Description]
Physical barriers like skin and mucus lining provide the first line of defense in innate immunity. Genetic factors are not physical barriers; instead, they influence susceptibility to certain infections but are categorized differently.

Key Concept:Cytokine and Cellular Interaction, Comparative Analysis

c) Macrophages
[Solution Description] Macrophages, a type of leukocyte, play a vital role in antiviral defense by being activated through signals from interferons, enhancing their ability to engulf and destroy virus-infected cells.

Key Concept:Allergy, Passive Immunity

a) By blocking histamine release at cellular levels instantaneously.
[Solution Description] In allergic reactions, the body mounts an exaggerated immune response against harmless substances. Passive immunity provides immediate relief by supplying ready-made antibodies, often IgG, which neutralize allergens or block them from binding to IgE receptors on mast cells. This interrupts the allergic cascade by preventing histamine release, reducing symptoms instantly without waiting for the host’s immune system to mount its own response, which is critical in acute allergic conditions.

Key Concept: Basic Concept

b) Reverse transcriptase

[Solution Description] HIV uses the enzyme reverse transcriptase to convert its RNA genome into DNA once it enters a host cell. This process is crucial for the integration of viral genetic material into the host’s genome.

Key Concept:Statutory Warning

c) Smoking is injurious to health
[Solution Description] Cigarette packets have statutory warnings indicating that smoking is injurious to health, highlighting various health risks associated with smoking.

Key Concept:Role of Macrophages

c) By phagocytosing microbes
[Solution Description]
Macrophages play a crucial role in innate immunity by engulfing and digesting pathogens and cellular debris through a process called phagocytosis. They also help activate other immune cells by presenting antigens derived from pathogens.

Key Concept:Psychological Effects, Real-world Scenarios

b) Alcohol withdrawal syndrome.
[Solution Description] Abrupt cessation of alcohol after prolonged heavy drinking can lead to alcohol withdrawal syndrome. Symptoms may range from mild anxiety and tremors to severe cases involving hallucinations and seizures. Proper medical intervention is often required to manage severe symptoms effectively.

Key Concept:Real-world Application, Long-term Effects

b) Implementing needle-exchange programs
[Solution Description] To address both immediate and long-term risks, implementing needle-exchange programs can significantly reduce the sharing of contaminated needles among drug users. This method not only decreases the direct transmission of infections like HIV but also facilitates access to educational resources and healthcare services for drug users, thereby providing a sustainable solution to mitigate infection rates.

Key Concept:Cancer Detection Methods, Characteristics of Malignant Tumors

b) It provides better soft tissue contrast, aiding in distinguishing malignant tissues
[Solution Description] MRI offers several advantages, particularly in terms of soft tissue contrast resolution. While CT scans and X-rays provide good images of bone structures, MRIs give a much clearer picture of soft tissues, where malignant tumors typically invade. This makes MRI an invaluable tool in detecting certain types of tumors that are not easily visible with other imaging modalities, especially those located near dense bone areas like the brain or spinal cord.

Key Concept:Immune Response Intensity

b) Secondary response
[Solution Description] In active immunity, the secondary immune response is more intense than the primary response. This heightened intensity occurs because of the presence of memory cells created during the initial exposure, which allow the immune system to recognize and respond more effectively to the same antigen upon re-exposure.

Key Concept:Complex Interactions, Comparative Analysis

c) Mucus and interferons
[Solution Description] To determine which combination of barriers is most effective against a respiratory viral infection, we need to consider both physical and cytokine defenses. Mucus acts as a physical barrier by trapping pathogens before they can enter the body. Cytokines such as interferons play a critical role in inhibiting viral replication within cells. The combination of mucus lining (physical barrier) and interferons (cytokine barrier) provides a comprehensive defense mechanism against respiratory viruses.

Key Concept:Virus Replication

c) Helper T-lymphocytes
[Solution Description] Once HIV enters the body, it primarily targets and replicates in specific immune cells. Macrophages and helper T-lymphocytes are the main sites for the replication of HIV. These cells are critical components of the immune system, playing essential roles in cellular immunity.

Key Concept:Case Study, Advanced Comparison

b) Emergency treatment following a poisonous snakebite.
[Solution Description] Passive immunity is immediately effective because it utilizes pre-formed antibodies. It is particularly useful for situations requiring urgent intervention, such as snakebites, where the rapid response outweighs the lack of long-term protection. Active immunity, conversely, takes longer to develop but offers lasting immunity.

Key Concept:Critical Thinking, Real-world Application

b) It provides alternative options for relaxation and expression
[Solution Description] Integrating sports and music provides outlets for students to channel their energy and emotions positively. It helps reduce stress and promotes healthy social interactions, which can protect against turning to drugs or alcohol as coping mechanisms. Furthermore, it instills self-discipline and enhances resilience.

Key Concept: Antibody Structure

d) IgE

[Solution Description] IgE antibodies are primarily involved in allergic reactions. They bind to allergens and trigger histamine release from mast cells and basophils.

Key Concept:Immune Response Types

c) Cell-mediated immune response
Cell-mediated immunity involves T-lymphocytes, which are responsible for directly attacking and destroying infected or cancerous cells.

Key Concept:Simple Application

a) To produce antigenic polypeptides in microorganisms
[Solution Description] Recombinant DNA technology allows for the production of vaccines by generating antigenic polypeptides in microorganisms like bacteria or yeast, facilitating large-scale production and enhanced safety.

Key Concept:Vaccine Production

a) It reduces the cost of production significantly
[Solution Description] Recombinant DNA technology enables large-scale production of vaccines efficiently, such as the hepatitis B vaccine. This method allows for better control over the production process, ensuring a consistent supply of vaccines at lower costs compared to traditional methods.

Key Concept:Withdrawal Symptoms

d) Anxiety and shakiness
[Solution Description]
Anxiety and shakiness are among the symptoms commonly experienced during withdrawal from opioids. These symptoms arise due to the body’s physical dependence on the drug being disrupted.

Key Concept:Real-world Application, Complex Interactions

b) Heart failure
[Solution Description] The combination of alcohol with other drugs can increase the risk of serious immediate effects like respiratory failure or heart failure due to compounded effects on the body’s systems. Fatigue and weight fluctuation may indicate the initial stages of such complications, leading potentially to overdose.

Key Concept:Antibody Type

c) IgE
[Solution Description] IgE antibodies play a crucial role in mediating allergic responses by binding to allergens and triggering the release of chemicals like histamine.

Key Concept:Critical Thinking, Real-World Application

b) To provide immediate protection from infections.
[Solution Description] Newborns are provided with passive immunity via maternal antibodies present in the colostrum and placenta because it gives immediate protection against infections during the early days of life when their own immune system is still developing. Waiting for natural development of active immunity would leave the newborn vulnerable to numerous pathogens.

Key Concept:Treatment Methods

c) Adrenaline
[Solution Description] Adrenaline is a drug that is commonly administered in cases of severe allergic reactions, such as anaphylaxis, to quickly alleviate symptoms.

Key Concept:Inference

c) It ensures timely intervention to prevent escalation of problems.
[Solution Description] Reporting danger signs to teachers or parents ensures that timely intervention can be made. This may involve addressing issues before they escalate to more serious problems, thereby providing the necessary support system for the student’s well-being.

Key Concept:Primary vs Secondary Response, Antibody Production, Immune Memory

b) Rapid activation of memory cells leads to efficient antibody production.
[Solution Description] The secondary response benefits from the presence of memory cells formed during the primary response, allowing for a faster mobilization of B and T cells, leading to rapid antibody production against the pathogen.

Key Concept:Complex Interactions, Behavioral Change

b) Easy access to unhealthy food and lifestyle options
[Solution Description] Modifying lifestyle choices to prevent cardiovascular diseases is challenging primarily due to the availability of tempting unhealthy options. Despite awareness efforts, the ease of access to fast food, sugary drinks, and sedentary entertainment can undermine healthy intentions. This challenge requires addressing environmental and societal factors enabling such easy access to unhealthy options.

Key Concept: Complex Consequences, Prevention Strategies

b) Cirrhosis leading to financial instability.

[Solution Description] Chronic alcohol abuse can lead to cirrhosis of the liver, which is a severe health condition where normal liver tissue is replaced by scar tissue, impairing liver function. This not only affects physical health but also has significant social implications as it may result in reduced productivity, job loss due to health issues, and increased healthcare costs.

Key Concept:Comparative Analysis, Critical Thinking

b) Illicit drugs tend to present more severe withdrawal symptoms than alcohol.
[Solution Description] Both alcohol and illicit drugs can cause strong psychological attachments due to the euphoric effects they produce. However, psychological attachment may vary depending on the substance’s effect on neurotransmitter systems. Illicit drugs often pose a higher risk of severe withdrawal symptoms compared to alcohol due to their potent effects and interaction with brain chemistry. This requires a deeper understanding of each substance’s pharmacokinetics and its impact on the central nervous system.

Key Concept:Social Implications

b) Isolation from peers
[Solution Description] Misuse of anabolic steroids can lead to isolation from peers. Athletes using these substances may face social stigma, distrust from teammates, or exclusion from team activities if they violate ethical guidelines.

Key Concept:Real-world Application

b) Taking remedial measures
[Solution Description] Rehabilitation practices suggest that recognizing danger signs should lead to taking immediate remedial measures, such as reaching out to professionals or counsellors who can offer guidance and support to prevent relapse.

Key Concept:Neurotransmitter Interaction

b) Dopamine
[Solution Description] Cocaine specifically acts by interfering with the reuptake of dopamine in the synaptic cleft. This interference results in an increased concentration of dopamine outside the neuron, thereby prolonging its action.

Key Concept:Integration of Concepts, Advanced Reasoning

d) They complement each other by providing motivation and support.
[Solution Description] Will power acts as internal motivation, essential for resisting temptations and making conscious decisions towards sobriety. Peer involvement offers external reinforcement, providing encouragement and accountability. Combined, they form a robust framework supporting sustained recovery.

Key Concept:Tumor Cell Competition

c) Both space and nutrients.
[Solution Description] Malignant tumor cells compete with normal cells primarily for nutrients, as they rapidly proliferate, requiring more resources than normal cells. This competition can lead to starvation and damage to normal cells.

Key Concept:Comparative Analysis, Advanced Reasoning

d) Vaccination offers long-term protection through memory cells; passive immunisation provides temporary protection.
[Solution Description] Passive immunisation involves the administration of preformed antibodies for immediate but short-lived protection, as the antibodies do not trigger memory cell formation. Vaccination, on the other hand, stimulates active immunity by introducing antigens that prompt the body to produce its own antibodies and memory cells, leading to longer-lasting immunity.

Key Concept:Identification

c) Ignoring stress
[Solution Description] According to the syllabus, ignoring stress is not suggested as a method for managing stress.

Key Concept:Cancer Detection Methods, Carcinogen Avoidance

b) When molecular profiling of the tumor is required
[Solution Description] While non-invasive imaging techniques such as MRI and CT scans provide detailed images of the body’s interior structures, they cannot provide cellular-level information. A biopsy involves taking a sample of tissue directly from the suspected area, which allows for histopathological examination. This method provides definitive confirmation of malignancy based on cellular morphology and genetic markers, making it crucial when precise diagnosis is necessary.

Key Concept:Immune System Components

d) Lymphocytes
[Solution Description] Lymphocytes, including T cells and B cells, are crucial components of the immune response; they help identify and neutralize pathogens like bacteria and viruses.

Key Concept:Advanced Mechanism, Critical Thinking

c) Due to complex genetic mutations and environmental interactions that are not yet fully understood.
[Solution Description] Autoimmunity arises when the immune system mistakenly attacks the body’s own cells, which can be triggered by complex mechanisms involving genetic predisposition and unidentified environmental factors. These unknown reasons make it challenging to fully understand the root causes of autoimmune diseases.

Key Concept:Historical Use

c) Religious ceremonies
[Solution Description] Historically, cannabinoids have been used in religious ceremonies, especially in certain cultures where cannabis has spiritual significance.

Key Concept:Treatment Methods

c) Chemotherapy
[Solution Description] Chemotherapy employs various drugs designed to destroy cancerous cells or stop them from growing and dividing.

Key Concept:Peer Pressure, Coping Mechanisms

c) It encourages experimentation with substances
[Solution Description] Peer pressure can significantly influence adolescents to adopt unhealthy behaviors like substance use, primarily because they seek acceptance within their social circle. This need for belonging often leads them to mimic peers’ habits, even if detrimental, thereby fostering reliance on harmful coping strategies that may persist into adulthood.

Key Concept:Memory Cells, Vaccination

b) They mount a stronger and faster response compared to the primary response.
[Solution Description] During a secondary immune response, memory B and T cells recognize the antigen more quickly than naive cells because they were generated in response to a prior exposure to the same pathogen. Memory B cells rapidly differentiate into plasma cells that secrete large quantities of antibodies, while memory T cells proliferate and execute their functions, such as helping B cells or killing infected cells, more rapidly than during the primary response.

Key Concept:Prevention Strategy

b) Promoting open communication
[Solution Description] Open communication is paramount in creating awareness and understanding among individuals, effectively reducing the chance of social abuse by promoting inclusive and supportive interactions.

Key Concept:Immunological Memory, Autoimmune Diseases

c) Diminished ability to recall previous pathogen exposures
[Solution Description] Immunosuppressive therapies aim to reduce abnormal immune responses in autoimmune conditions but can also affect immunological memory. This may lead to increased vulnerability to infections due to a diminished capacity to mount rapid secondary immune responses from memory cells.

Key Concept:Comparative Analysis, Complex Interactions

b) Boiling is less practical but more thorough in killing all types of pathogens.
[Solution Description] Chlorination and boiling are common methods for disinfecting water to eliminate pathogens responsible for waterborne diseases. Chlorination introduces chemical agents like chlorine to kill bacteria and viruses but may not completely eliminate resistant protozoa unless administered at appropriate concentrations over time. Boiling water, however, ensures the destruction of virtually all microorganisms, including resilient cysts and spores, making it slightly more reliable for complete disinfection. A comparative analysis shows that boiling is generally more effective in providing comprehensive pathogen elimination.

Key Concept:Memory Cells

b) They remember specific pathogens and accelerate the immune response upon re-exposure
[Solution Description] Memory B and T-cells play a vital role in ensuring the effectiveness of active immunity by remembering specific pathogens after initial exposure. Upon re-exposure to the same antigen, these cells enable the immune system to mount a faster and stronger response, often neutralizing the pathogen before it can cause significant harm.

Key Concept:Pathogen Adaptation, Disease Transmission Dynamics

d) By being more stable in cooler, less humid environments
[Solution Description] Influenza viruses are more stable and remain infectious longer at lower temperatures and lower humidity conditions found in winters. This adaptation allows them to survive in airborne droplets and enhances their ability to spread between hosts. Other factors include changes in human behavior during cold weather (e.g., staying indoors), increasing close contact transmission opportunities.

Key Concept:Real-World Application

a) To reinforce memory cell function and ensure a strong immune response
[Solution Description] A booster dose is administered to re-expose the immune system to the immunizing antigen. It helps reinforce the body’s immune memory by stimulating memory B and T-cells so that upon any future exposure to the pathogen, the body can mount a quicker and stronger immune response.

Key Concept: Acquired Immunity and Antibodies

c) IgE

[Solution Description] The antibody class involved in allergic reactions is IgE. IgE binds to allergens and triggers histamine release from mast cells and basophils, which contributes to allergic responses.

Key Concept:Mechanism Explanation

c) Through strong magnetic fields and radiofrequency pulses
[Solution Description] MRI detects physiological changes by utilizing strong magnetic fields and non-ionizing radiofrequency pulses to generate signals from hydrogen nuclei in the body. These signals are then processed to create detailed images of tissues.

Key Concept: Pathogen Identification

c) Plasmodium

[Solution Description] Malaria is caused by protozoan parasites belonging to the genus Plasmodium. These parasites are transmitted through the bite of infected Anopheles mosquitoes.

Key Concept:Basic Concept

c) To diagnose AIDS
[Solution Description] ELISA (Enzyme-Linked Immunosorbent Assay) is a widely used diagnostic test to detect antibodies against HIV in the blood, thereby diagnosing AIDS.

Key Concept: Common Allergens

a) Dust mites

[Solution Description] The syllabus mentions dust mites, pollen, and animal dander as common allergens.

Key Concept:Substance Abuse Indicators

b) Isolation
[Solution Description] A common indicator of substance abuse is isolation, where individuals withdraw from their social circles and activities they once enjoyed.

Key Concept:Withdrawal Symptoms

b) Nausea
[Solution Description] Nausea is a common symptom experienced during alcohol withdrawal. As the body adjusts to the absence of alcohol, it can react adversely, leading to symptoms like nausea, shaking, and anxiety.

Key Concept: Basic Hygiene

b) Both Assertion and Reason are true, but Reason is NOT the correct explanation of Assertion.

[Solution Description] The assertion emphasizes the significance of personal hygiene, such as washing hands and maintaining cleanliness, in preventing infections. The reason provided discusses public hygiene practices like waste management and water sanitation which are broader community actions supporting disease prevention.

Key Concept:Carcinogen Mechanism, Cancer Progression Stages

c) Physical carcinogen; Disrupts cell cycle regulation.
[Solution Description] Physical carcinogens like X-rays ionize molecules within DNA directly, breaking strands and causing mutagenic changes in the initiation phase of cancer development. Such mutations often affect genes regulating cell cycle control, impairing checkpoints, hence permitting inappropriate progression through cellular phases and fostering unregulated growth.

Key Concept:Adolescence Vulnerability

c) Need for adventure and excitement
[Solution Description] Adolescents are at higher risk for substance abuse problems due to their developmental stage characterized by curiosity, peer pressure, and sometimes unstable family environments which all contribute to experimentation with drugs or alcohol.

Key Concept:Technique Application

a) Immunochemistry
[Solution Description]
The usage of antibodies specific to cancer antigens is a hallmark of immunological techniques such as ELISA, which detects proteins by antibody-antigen interactions. Imaging methods like CT or MRI don’t utilize antibodies directly.

Key Concept:Basic Comparison

c) It provides immediate but temporary protection using pre-formed antibodies.
[Solution Description] Passive immunity is characterized by the immediate provision of pre-formed antibodies, offering temporary protection without eliciting a host’s immune response.

Key Concept:Pathogen Adaptation, Modes of Transmission

c) By producing a protective polysaccharide capsule.
[Solution Description] Streptococcus pneumoniae produce a polysaccharide capsule that protects them against phagocytosis by immune cells. This adaptation helps them survive and establish infection in the host’s respiratory tract.

Key Concept: Prevention Strategies

b) Seeking professional help

[Solution Description] Prevention strategies for adolescent substance abuse involve education and support systems. Effective strategies include seeking professional help, such as counseling, to address underlying issues and provide coping mechanisms. This approach focuses on addressing root causes and promoting healthy alternatives.

Key Concept:Effects on Pregnancy

a) Fetus
[Solution Description] The use of drugs and alcohol during pregnancy adversely affects the development of the fetus, potentially leading to developmental disorders, birth defects, or other health issues.