Human Bio Exam

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List the four micro-organisms that cause disease and their structural features in terms of (cellular structure, cell type, cell wall and membrane)

List the four micro-organisms that cause disease and their structural features in terms of (cellular structure, cell type, cell wall and membrane)

• Bacteria

  Cell Structure: Prokaryotic, meaning they lack a defined nucleus and membrane-bound organelles.

  Cell Type: They are unicellular organisms.

  Cell Wall: Rigid cell wall.

  Membrane: Plasma membrane that regulates substances into and out of the cell.

• Viruses

  Cell Structure: Viruses are non-cellular, meaning they lack cellular structures like a membrane.

  Cell Type: Not considered true cells due to the fact they are “non-living”.

  Cell Wall: Some viruses have an additional lipid surrounding the capsid but some do not, referred to as “naked” viruses.

  Membrane: Does not have a true membrane but some may have a protective outer layer.

• Protists

  Cell Structure: Eukaryotic, with a defined nucleus and membrane-bound organelles, including mitochondria.

  Cell Type: Unicellular organisms, although they may exist in colonies.

  Cell Wall: Protozoa lack a cell wall but have a cell membrane that allows for more shapes and movement.

  Membrane: Have a cell membrane that functions in protection and substance exchange.

• Fungi:

  Cell Structure: Eukaryotic, with a defined nucleus and membrane-bound organelles, including mitochondria.

  Cell Type: Can be both unicellular organisms and multicellular.

  Cell Wall: Their cell wall is made of a substance that provides structure and rigidity.

  Membrane: Fungal cells have a cell membrane containing a substance that helps maintain membrane fluidity.

Compare similar structures and contrast differences of the four main microorganisms that cause disease.

Cellular Structure:

• Similarities:

  • Bacteria, fungi, and protozoa have a structured arrangement with cytoplasm enclosed by a cell membrane.

  • Fungi and protozoa are eukaryotic.

• Differences:

  • Bacteria are prokaryotic, while fungi and protozoa are eukaryotic.

  • Viruses are acellular and lack a cellular structure entirely.

Cell Type:

• Similarities:

  • Bacteria, viruses, and protozoa are generally unicellular.

• Differences

  • Fungi are the only group among these four that can form multicellular.

Genetic Material:

• Differences:

  • Viruses may carry either DNA or RNA, while the others only have DNA

Cell Wall:

• Similarities:

  • Bacteria and fungi both have rigid cell walls

• Differences:

  • Viruses lack any cell membrane and protozoa only have a flexible cell membrane.

Differentiate between types of bacteria

Spherical Bacteria:

• Cocci are spherical or round-shaped bacteria. Commonly associated with respiratory, skin and wound infections

Rod-shaped Bacteria:

• Bacilli are cylindrical/rod-shaped bacteria, allowing for more movement. Found in soil, air and water, frequently causing gastrointestinal, respiratory and wound infections.

Curved Bacteria:

• There are two main types of curved bacteria

  • Curved rods or vibrio have a comma-shaped or curved rod appearance, assisting in mobility.

  • Spiral shaped Bacteria or spirillum have a more rigid spiral shaped and are generally longer and twisted like a corkscrew, helping with movement in viscous environments, like mucus.

State an example of an infection disease caused by bacteria

Salmonella is an infection transmitted through contaminated water or food, especially undercooked poultry, eggs, and raw produce. Symptoms typically include diarrhea, fever, abdominal cramps, and nausea.

Compare DNA viruses with RNA viruses simply

Genetic Material:

• DNA viruses replicate in the host cell’s nucleus which is generally slower but more stable, meaning less mutations.

• RNA viruses replicate in the host cell’s cytoplasm and if faster but less stable, meaning more mutations.

Mutation Rate:

• DNA viruses typically have a lower mutation rate compared to RNA viruses.

How does viruses replicate?

• Attach and Enter: The virus attaches to the host cell and enters it.

• Release Genetic Material: Inside the cell, the virus releases its DNA or RNA.

• Hijack Cell Machinery: The viral genetic material takes over the cell's machinery, directing it to make viral parts (like more viral DNA/RNA and proteins).

• Assemble New Viruses: The viral parts assemble into new viruses.

• Release: New viruses leave the cell to infect other cells.

State a disease produced by protists

Malaria is a disease caused by protozoan protists. It is transmitted to humans through the bite of an infected female mosquito. The parasite infects red blood cells, leading to symptoms like fever, chills, fatigue, and anemia.

State a disease caused by fungus

A common disease caused by fungi is athlete’s foot which is a fungal infection that affects the skin, particularly the feet, causing itching, redness and peeling.

Describe the classification of protist pathogens

Unicellular eukaryotes that are not classified as plants, animals or fungi but may have some plant, animal or fungi features.

Define pathogen

Any infectious organism that causes disease.

Differentiate between infectious, contagious and non-infectious diseases

Infectious diseases:

• Caused by microorganisms such as bacteria, viruses, fungi or parasites that can spread through various methods, like the air, bodily fluids, contaminated food/water, or vector organisms.

Contagious diseases:

• Subset of infectious diseases that spread easily from person to person and are spread easily from person to person through physical touch, airborne droplets or indirect contact with contaminated surfaces.

Non-infectious Diseases:

• Not caused by pathogens but arise from other factors such as genetics or environmental conditions and cannot be spread from person to person, like cancer or diabetes.

Key Point: All contagious diseases are infectious, but not all infectious diseases are contagious.

What is health?

Health is a state of complete physical, mental and social well-being and not merely the absence of disease or infirmity.

What is disease?

Any harmful deviation from the normal structural or functional state of an organism.

What is disorder?

Disturbances of the normal state of the body or mind.

Define Micro-organism

Organism(s) you can’t see with the naked eye

Define Virulence

The amount of harm a pathogen causes

Define Endemic

Always present in the population

Define Epidemic

Something that affects a large population in a short time

Define Pandemic

At least 5 regions affected

Define Infection

An invasion of the body by harmful

Define outbreak

A disease outbreak is the occurrence of cases of disease in excess of what would normally be expected.

Discuss three ways that infectious diseases are spread

• Direct or close contact - transmission within 1-2m. For example, COVID-19.

• Indirect contact - transmission outside of 1-2m. For example, on a infected surface.

• Vectors - organisms that transmit pathogens to a susceptible host. For example, a mosquito to a unvaccinated human.

Describe the life cycle of viruses that infect animal cells

Attachment: The virus attaches to a specific receptor on the surface of the host cell.

Entry: The virus or its genetic material enters the host cell.

Uncoating: The virus's outer shell is removed, releasing its genetic material into the cell.

Replication and Protein Production: The virus takes control of the host cell to make copies of its genetic material and produce viral proteins.

Assembly: New viral particles are put together inside the host cell.

Exit: The new viruses are released from the host cell, either by budding (taking part of the cell's membrane) or by breaking the cell open (lysis).

Infection of New Cells: The new viruses go on to infect other cells.

Describe how a virus can change over time due to mutations

Sometimes when a virus makes copies of itself, sometimes mistakes occur causing changes/mutations in its genetic code. These effects can be neutral, beneficial or harmful for the virus’s effect in infecting cells or escaping the immune system. If the mutation is beneficial, the virus may survive and spread further, making it more common in the population.

Relate the concept of ‘zoonotic disease’ to Avian influenza virus and make a justified conclusion about classifying a virus a zoonotic/not zoonotic

Zoonotic diseases are diseases that can be transmitted from animal to humans. The avian influenza virus primarily affects birds but eventually, a few certain strands became know to infect humans, usually though direct contact with infected birds or droppings.

To classify a virus as zoonotic or not:

• Source: A virus that originates in animals but can be transmitted to humans is zoonotic.

• Transmission: A zoonotic virus must have the ability to cross species barriers and infect humans.

Discuss a common infectious disease, its causes, symptoms and treatment.

Norovirus is a highly contagious virus that causes stomach and intestinal inflammation, leading to symptoms like nausea, vomiting, diarrhea, and stomach cramps. It is primarily spread through contaminated food, water, or direct contact with infected surfaces or people. There is no specific treatment for norovirus, but staying hydrated is crucial, and symptoms usually resolve within 1-3 days. Preventing infection involves frequent hand washing and avoiding contact with infected individuals.

Briefly compare, the innate (non-specific) and adaptive (specific) immune systems to defend ourselves from pathogens.

The non-specific immune system is the body’s first and second line of defense and reacts quickly to a wide range of pathogens, includes physical and chemical barriers such as skin or phagocytosis.

The specific immune systems is slower but more targeted, involving T cells and B cells that recognize and attack specific pathogens and has the ability to “remember past infections” for faster responses in the future.

Describe 1st line of defense

Reacts quickly to a wide range of pathogens and includes:

• Skin: Act as an effective barrier against most pathogens unless it’s broken by a cut or graze.

• Mucous Membrane: Trap pathogens so they can be flushed from the body or swallowed and can also can break down bacteria’s cell walls.

• Hairs: Cilia are microscopic hairs on the cells that line the airways line the airways and mucus (that may have trapped pathogens) out of the airways.

• Acids: Kills pathogens we swallow before they can cause an infection

Describe the 2nd line of defense

Reacts quickly to a wide range of pathogens and includes:

• Phagocytosis: White blood cells called phagocytes that destroy anything they don’t recognize as part of the body. This is done by “swallowing” or engulfing it.

• Inflammation: Painful redness and swelling around the site of an infection is called inflammation. This happens because more blood, containing white blood cells that are specialized to fight off the pathogens, is directed to that part of the body.

• Fever: Fever is an increase in core body temperature above 38C and is usually accompanied by shivering and sweating, slowing down and even killing some pathogens. It also speeds up processes that help the immune system deal with the threat.

Describe inflammation in depth

When the physical impervious barrier is broken, the tissues and cells are damaged. This stimulates mast cells to release chemicals like histamine, heparin and phagocytes.

• Histamine increases the blood flow at the sit of injury, increase the permeability of capillaries therefore the site of injury looks red, swollen and is hot.

• Heparin prevents blood clotting at the site of injury. Phagocytes arrive at the site of injury and carry out phagocytosis.

Usually, mechanical damage pain receptors are impinged so pain is experienced. This is the inflammatory response and over time, mitosis results in repair to the damaged area.

Describe fever in depth

A fever is an increase in temperature above a set point, for a short period of time. The hypothalamus resets the set point at a higher level then normal and thus the person will feel colder. To combat this, shivering, the rhythmic contractions of muscles to generate heat will increase, and vasoconstrictions of blood vessels occurs so that less blood passes through and less heat is lost through radiation, conduction and convection and thus your body temperature will rise. Fever breaks, called crisis, and the hypothalamus resets the set point back to normal (37C). The person feels too hot so they sweat on the surface of the skin; the evaporation of sweat cools the person down. Vasodilation of blood also occurs to allow blood to flow so heat is lost.

Describe four protective reflexes and give an example of each.

• Coughing: Helps clear the respiratory tract of mucus or pathogens. E.g. dust or smoke may enter the airways but coughing expels these particles.

• Sneezing: Helps clear particles and pathogens from nasal passages. For example, when pollen or a virus like the common cold irritates the nasal lining, sneezing removes them forcefully.

• Vomiting: Helps remove harmful substances from the stomach. For example, the body may induce vomiting to expel harmful foods before they are absorbed.

• Tearing: Tears wash away foreign particles and pathogens from the eyes. For example, when smoke or dust enters the eyes, tear production increases to flush it out.

Define and describe active/specific immunity

Type of immune response where the body’s recognizes, targets and remembers a particular pathogen. This is highly effective because it develops specific defenses against a pathogen.

• Natural Active Immunity: When a person is exposed to a pathogen, memory cells (from B-cells) are created and remember, allowing the body to respond more quickly and effectively if exposed to the same pathogen in the future.

• Artificial Active Immunity: Achieved through vaccination where a weakened, inactive or antibody is injected into the body to stimulate the immune system/be introduced into the immune system and much like natural immunity, causes memory cells that prepare the body for future exposures.

Define immune

Totally or partially resistant to a particular infectious disease or pathogen.

Define passive immunity

A type of immunity that occurs when a person is given antibodies rather than making them through themselves. This can be observed in babies getting antibodies from their mother.

Discuss the difference between artificially acquired and naturally acquired specific immunity.

Artificial immunity involves medical intervention to provide antigens or antibodies, while natural immunity occurs through natural exposure to pathogens or antibody transfer.

Explain the role of lymphocytes (white blood cells) in humoral (antibody) mediated immunity and cell-mediated immunity

Lymphocytes play crucial roles in both humoral (antibody) immunity and cell-mediated immunity.

Humoral Immunity: B lymphocytes (B cells)

• Antigens (e.g. bacteria, toxins) is presented to the B-cell and it matches with its specific antibody receptor.

• After binding to an antigen, the b-cell is primed/sensitized.

• Mitosis occurs

• Clones produced which form (3/4 of clones) plasma cells and some memory cells (1/4)

• Plasma cells produce antibodies specific to the antigen to target and neutralize the pathogen.

• Memory B cells persist in the body, providing faster, stronger responses if the same pathogen appears in the future.

Cell-Mediated Immunity: T lymphocytes (T cells)

• Antigens (e.g. bacteria, toxins) is presented to the t-cell and it matches with its specific antibody receptor.

• After binding to an antigen, the b-cell is primed/sensitized.

• Mitosis occurs

• Clones produced which form 4 types of cells:

  • Killer T-cells: Identify and destroy infected or abnormal cells that have become cancerous by binding to antigens presented on the surface of infected cells.

  • Helper T-cells: They act as “coordinators” of the immune response. They don’t directly kill infected cells but are essential for activating other immune cells, activating b-cells in the humoral response.

  • Memory T-cells: Remain in the body long after the infection to provide a faster, stronger response if the same antigen is encountered again, leading to quicker activation of Killer T-cells and Helper T-cells.

  • Suppressor T-cells: Decreases the production once the infection is resolved.

Compare and contrast the similarities and differences between the humoral and the cell-mediated responses.

Similarities:

• Both responses are highly specific to the pathogen, meaning they target specific antigens unique to each invader.

• Both generate memory cells after an infection, allowing for quicker and stronger responses.

Differences:

• Location of Attack: Humoral immunity targets pathogens outside the cells, in bodily fluids, while cell-mediated targets pathogens hidden inside the cells.

• Mechanism of Defense: Humoral uses antibodies to neutralize pathogens where cell-mediated T-cells to directly kill infected cells.

• Primary Cells Involved: Humoral primarily uses B-cells while cell-mediated primarily uses T-cells.

Discuss three ways infectious diseases can be controlled

Physical Preventative Methods:

• Barriers and hygiene practices that reduce exposure. Simple yet effective.

  • Handwashing: Removes pathogens from skin, especially after coming in contact with contaminated surfaces

  • Protective Gear: Gloves or face masks limit direct contact

  • Insect Nets: Protects against vector diseases like malaria

Medication:

• Treat infections by directly targeting and killing pathogens but overuse or stopping before course can lead to antibiotic resistance.

  • Antibiotics: Work by targeting specific bacterial structures or functions. They tend to remove all bacteria which creates a trend of good bacteria being killed. Following through the course of antibodies is better as the bacteria tend to become more resistant to antibodies.

  • Antivirals: Inhibit replication of viruses, allowing the immune system to gain control over the infection.

Vaccination:

• A weakened, inactive or antibody is injected into the body to stimulate the immune system/be introduced into the immune system, causing immune system to recognize and respond to a pathogen.

  • Childhood Vaccines: Examples include measles, protecting children to these contagious diseases.

  • Flu Vaccine: Protect against influenza.

Explain why vaccinations were developed

They were developed to protect individuals and communities from infectious diseases. Before vaccines were invented, infectious diseases like smallpox, polio and measles caused major devastations and by creating vaccinations, these effects were reduced and established her immunity, which is when a large portion of the population is immune to a disease.

What are vaccines made out of?

Living Attenuated Microorganisms: Contain live microorganisms that have been weakened so they cannot cause disease. The immune system recognizes the weakened pathogen, providing antibodies and memory cells.

Dead Microorganisms: These contain microorganisms that have been killed by heat, chemicals or radiation, making them incapable of replication and causing disease. Triggers immune system to produce more antibodies but often requires multiple doses or booster shots.

Toxoids: Some vaccines use toxins produced by bacteria, which have been inactivated toxin as an antigen and produces antibodies.

Sub-Unit Vaccines: These vaccines consist of parts or subunits of the microorganism, such as specific proteins or sugars that are part of the pathogen but not the whole pathogen.