Knowt
Biology - Human Health and Disease
OBJECTIVES
Week 1: Micro-organisms that Cause Disease
List the four micro-organisms that cause disease: Bacteria, Viruses, Protists, and Fungi.
Describe the main structural features of these micro-organisms.
Compare and contrast the structures of the four main microorganisms in a table.
Differentiate between types of bacteria: spherical (coccus), rod-shaped (bacillus), and curved (spirillum and vibrio).
State an example of an infectious disease caused by bacteria.
Compare DNA with RNA viruses.
Explain how viruses can replicate.
Week 2: Disease/Infectious Disease
State a disease caused by a protist, like malaria.
Describe the classification of protist pathogens.
State a disease caused by a fungus.
Define the term pathogen.
Differentiate between infectious, contagious, and non-infectious diseases.
Distinguish between health, disease, and disorder.
Define the following terms: micro-organism, infection, virulence, endemic, epidemic, pandemic, and outbreak.
Identify structural components of SARS-CoV-2.
Describe the steps in the SARS-CoV-2 replication cycle.
Explain how viruses can mutate over time.
Relate the concept of a ‘zoonotic disease’ to COVID-19.
Week 3: Non-specific Defense Against Infectious Disease
Briefly compare the innate (non-specific) and adaptive (specific) immune systems.
Describe external non-specific defenses including skin, mucous membranes, hairs, and acids.
Describe internal non-specific defenses including phagocytosis, inflammation, and fever.
Describe four protective reflexes and give an example of each.
Discuss three ways that infectious diseases are spread.
Week 4: Specific Defense
Recall major blood components: red blood cells, white blood cells, plasma, and platelets.
State the main parts of the immune system.
List different types of white blood cells and their functions.
Define antibody and antigen.
Explain the function of an antibody and its specificity to an antigen.
Define and describe active/specific immunity.
Define the terms immune and passive immunity.
Explain the role of lymphocytes in humoral (antibody) mediated immunity and in cell-mediated immunity.
Compare and contrast the similarities and differences between humoral and cell-mediated responses.
Week 5: Controlling Infectious Disease
Discuss three ways infectious diseases can be controlled: physical preventative measures, medication, and vaccination.
Explain why vaccinations were developed and what they consist of.
Discuss the specificity of antibodies and antigens.
Describe the use of nanotechnology to deliver vaccines or genetic sequencing or engineering to produce a vaccine.
Micro-organisms that Cause Disease
Bacteria
Prokaryotic as it has no membrane bound organelles, no nucleus but does have a nucleoid. It is unicellular, relatively larger than viruses but smaller thana the other.
Bacteria Types & Examples:
Spherical (Coccus):
Cocci
Example: Staphylococcus aureus
Rod-Shaped (Bacillus):
Bacilli
Example: Escherichia coli
Curved (Spirillum, Vibrio):
Spirilla and Vibrios
Example: Vibrio cholerae
Viruses - Non-cellular pathogens
A virus is a non-cellular agent composed of a protein coat (capsid) and nucleic acid either DNA or RNA (but never both).
Consists of one or more strands of nucleic acid (RNA or DNA) inside a protein coat. They are non-living as they are not made out of cells, possess no metabolic machinery for processes such as respiration and are not classified as prokaryotes or eukaryotes. The agent is microscopic, relatively small compared with all other pathogens and is usually measured at 30-300 nanometres in length.
All viruses cause some type of disease because they rely totally on host cells for their reproduction. This can also be referred to as an obligate parasite (that cannot function outside the host cell).
Viruses infect an organism by injecting its nucleic acid into a host cell. Once inside, the viral nucleic acid takes over the host cell and directs it to make multiple copies of the viral protein coat and nucleic acid. These are then assembled into new viruses and are released when the host cell undergoes lysis, or splits open. This releases many more viral articles, which can infect other cells within the host.
Protists
Fungi
Structural Features:
Bacteria
Prokaryotic
Unicellular - Possess ribosomes and a single circular strand of DNA. Can also have plasmids.
Has a nucleoid
Plasma membrane that encloses cytoplasm
Cell wall outside of their plasma membrane - Peptidoglycan
Larger than viruses but still smaller (1-10 micrometres length)
Viruses
Whether it's Cellular/Non-Cellular
Prokaryotic/Eukaryotic
Unicellular/Multicellular
Type of Cell Membrane/Wall
Relative Sizes
Protists
Eukaryotic - have membrane bound organelles and have a nucleus
Mostly Unicellular
Animal types have no cell wall but plant type do have chloroplasts (with no cell wall)
Highly diverse set of structures in the protist kingdom but have structures that allow sexual and asexual reproduction - can lay dormant for many years.
Fungi
Cell wall made of Chitin (Not all have it in all of its life cycle)
Flagellum in some - whip-like tail that enables movement in water/wet soil therefore they are motile
Unicellular or Multi-cellular
Filaments - long, thin structures that absorb nutrients(high surface area)
Hyphae — small branches of filaments
Mycelium - Interwoven mass of interconnected hyphae
Reproductive structure
Sporangia - a mature form of fungus - able to protect the growing (baby) spores (offspring).
Virus Comparison:
DNA vs RNA Viruses:
DNA Viruses: [Insert Comparison Points Here]
RNA Viruses: [Insert Comparison Points Here]
Virus Replication Explanation: Steps 1 - 6
Viruses are usually limited to infecting one specific host cell or organism because viruses are able to recognise and bind to receptors that are expressed only on respiratory tract epithelial cell surfaces. In order to replicate, viruses require host cells meaning that they are pathogenic. Host cells experience symptoms when a virus is replicating inside the host’s cells.
1-6 Steps Virus Replication - AERSAR
Attachment - The virus binds to a protein receptor on the surface of a host cell.
Endocytosis - Entry of virus nucleic acid (DNA/RNA) into the host cell. (Moving in - endo into the cytoplasm - cyto = endocytosis)
Replication - Viral DNA/RNA enters the nucleus of the eukaryotic host cell.
Synthesis - Viral DNA/RNA directs the host cell to replicate it and make copies of viral proteins via translation.
Assembly - New viral DNA/RNA and proteins assembly at the host’s cell membrane.
Release - New viruses move through the membrane - sometimes using part of the cell’s phospholipid bilayer to form an outer layer. This may cause the cell to die.
1-4 Steps Virus Replication - Diagram Annotation
Virus attaches to receptors or surface of host cell.
Endocytosis - Virus moves in to host cell and un-coats (protein coat is removed).
Replication - Replication of nucleic acid of DNA or RNA.
Synthesis - transcription and translation of new viral proteins.
Assembly - Assembly of new viruses at the cell membrane.
Release/Exocytosis - release of new viruses. Can cause the host cell lysis (to die).
Some viruses can take the cell membrane of the host cell and use it as a protective layer. This happens in only some viruses.
Apoptosis
Disease / Infectious Disease
A disease is any condition that interferes with how an organism, or any part of it, functions. Infectious diseases are caused by a pathogen and can be passed from one organism to another. Infectious diseases can be caused by viruses, bacteria, fungi and protists.
Diseases can be infectious or non-infectious and infectious comes from pathogens.
Non-infectious are typically derived from environmental heredity.
Disorder - organs/organism not functioning within the range determined as ‘normal’.
Depression, anxiety disorders, schizophrenia, eating disorders.
Key Definitions:
Infectious vs Contagious vs Non-Infectious Diseases:
Diseases are described as infections (communicable) if they are caused by an invasion of a pathogen and can be transmitted from one host to another.
If infectious disease can be transmitted from infect host to susceptible host, it becomes contagious
Communicable diseases that are spread through direct or close contact with an infected host, or by touching a contaminated object cna be referred to as contagious. A disease can be infectious but not contagious.
An infection occurs if a pathogen has entered a host, has established itself and is replicating
Pathogen: A pathogen is an infectious agent that causes disease. There are several different types of pathogens; viruses, bacteria, fungi and protists.
Transmissions - The passing of an infectious disease from an infected host to another individual. It depends on 3 different factors, the infectious agent, the susceptibility of the host and the mode of transmission
Infectious diseases are caused by a pathogen and can be passed from one organism to another. Infectious diseases can be caused by viruses, bacteria, fungi and protists.
Zoonotic diseases - Infectious diseases that can be transmitted between a different animal vertebrate group and humans. Transmission is primarily through direct contact with infected animals but can also be through close contact.
Direct Contact -
Indirect Contact - refers to when a susceptible host comes into contact with areas where the infected live or roam, where surfaces or objects have been contaminated. Vectors such as mosquitoes
Micro-organism - an organism that can only be observed by the naked human eye under a microscope.
Infection - signs and symptoms of a pathogen invasion and pathogen reproduction and/or pathogen toxin. The signs and symptoms can include the bodies response to the presence of the pathogen.
Virulence - the measure of severity of a disease e.g. the bacteria that causes tuberculosis is highly virulent because it’s structures and functions help it evade human host immune system cells.
Endemic - predictable number of infected hosts, for a specific disease, whether it is seasonal or unchanging, in a population
Epidemic - a sudden increase in incidence of infected hosts, for a specific disease that has spread around a local area.
Pandemic - A sudden increase in incidence of infected hosts, for a specific disease, that has spread across large regions/continents/international borders
Outbreak - a sudden increase in incidence of infected hosts, for a specific disease in one population.
Infectious | Non-infectious | Contagious |
|---|---|---|
e.g. | e.g. Cancer | e.g. |
No infectious agent present |
Health vs Disease vs Disorder
Health - all organs functioning within a normal range.
Disease - Once organs no longer function within normal range then you have a disease.
Disorder -
SARS-CoV-2
Structure - protein coat, RNA genome, membrane protein, extra lipid molecules (layer of protective protein), centre nucleic acid,
Specific replication cycle of SARS-CoV-2
Attachment - Glycoprotein (spike protein) binds to receptors proteins of the host cell.
Endocytosis - Some of the host cell membrane wrapped itself around the host virus to pull it in (triggered by attachment)
fusion of virus envelope and endosome membrane
incouting of the protein coat
with the uncoating of protein coat, the RNA is exposed
Translation of viral polymerase - Make complementary strand of RNA - negative RNA → positive RNA
Replication - producing replicates of the original RNA thorugh viral genome replication Negative RNA goes into positive RNA
Transcription - of negative RNA is making positive RNA but this time, mature RNA (short and coding for 1 protein at a time). Uses polymerase to make complementary strands of the parts of the negative RNA needed to make specific proteins. Transcriptions only involve 1 gene at a time
Translation - mRNA protein synthesis into viral proteins
Glycoprotein processing and virus assembly, Virus maturation
Fusion of virus envelope and endosome membrane
Translation of viral polymerase.
COVID-19 Analysis:
Changes to the RNA that code for the antigens in the virus
Mutated to make it more transmissible but less virulent allows it to persist
Types of Transmissions
Transmission
Respiratory disease - (infected host coughs/sneezes/talks and susceptible host inhales)
Fomite/contaminated surface - (contact/touching virus on surface e.g. table, phone, and then touching
Vectors - biological (mosquito) or inanimate vehicle (transport/transfer a pathogen to a susceptible host.
Mutation
Random permanent change in genetic material (DNA/RNA) heritable for infectious disease to persist.
Direct contact of infected host and susceptible host - sexually transmitted diseases usually
Zoonotic
transmission of agent from a different vertebrate group to a human and/or vise versa. (Different vertebrate species)
Humans
Immune Responses to Infectious Diseases
Non-Specific
first line of defence - anatomy, barriers and reflexes
Skin has oily secretion barrier sebum that kills bacteria
Mucus membranes - the lining of body cavities open to the exterior e.g. nose and ears
Trachea - idk what this is
Cilia - Tiny hair-like projections on the surface of tissue where mucous membranes are found
Acid - Stomach contains hydrochloric acid that can kill bacteria with very low pH
Oesophagus
Lysosome - Tears
Second line of defence - Phogocytosis inflamation fever processes(physiological processes
4 reflexes - removes pathogens from the body in 4 different ways
Specific
third line of defence cell-mediated + antibody-medicated processes.
Transmission
Pathogenicity - their disease-causing capacity.
Virulence - the intensity of the effect of the pathogen.
Susceptibility -
Binary Fission
The bacterium before binary fission is when the DNA is tightly coiled. Observe the cell wall, chromosome, plasmid and ribosomes.
The DNA of the bacterium is a single circular chromosome, has uncoiled and duplicated.
The chromosomes attaches to the cell membrane and are pulled to the opposite poles of the bacterium as it elongates.
The growth of a new cell wall begins to separate the bacterium.
The new cell wall (septum) fully develops, resulting in the complete split of the bacterium.
The two new daughter cells are identical to the parent cell.
Detailed Notes on Science Understanding - Response to Infection:
Pathogens and Transmission:
- Pathogens are microorganisms, such as bacteria and viruses, that can cause infectious diseases.
- They spread from one host to another through various transmission mechanisms:
- Direct contact: Occurs when an infected person directly touches or contacts another person.
- Indirect contact: Happens when a person touches contaminated objects or surfaces.
- Body fluids: Pathogens can be transmitted through blood, saliva, semen, and other bodily fluids.
- Disease vectors: Certain organisms like mosquitoes or fleas can carry and transmit pathogens.
- Contaminated food and water: Consuming contaminated food or water can lead to infections.
External Defense Mechanisms:
- The body's external defenses serve as the first line of protection against invading pathogens:
- Skin: The skin acts as a physical barrier that prevents pathogens from entering the body. It's especially effective when intact.
- Mucous membranes: These line body cavities that open to the exterior (e.g., respiratory and digestive tracts) and secrete mucus. Mucus helps trap and inhibit the entry of microorganisms.
- Hairs and cilia: Found in the nose and ears, these structures help filter out particles from the air, reducing the risk of pathogens entering the respiratory system.
- Stomach acid: The strongly acidic gastric juices in the stomach can kill many ingested pathogens.
- Other acidic secretions: Some body fluids, like vaginal fluids, are acidic, which can inhibit the growth of certain bacteria.
- Fluid movement: Urine flow and the flushing action of fluids help remove pathogens from certain areas, such as the urinary tract and mouth.
Phagocytosis:
- Phagocytes are specialized white blood cells (leucocytes) that play a crucial role in the immune response by engulfing and digesting pathogens.
- There are different types of phagocytes:
- Monocytes: These cells can leave the bloodstream and differentiate into macrophages, which are large phagocytic cells. Macrophages can move through tissues or remain fixed.
- Neutrophils: These are granulated leucocytes with a lobulated nucleus. They are the most abundant and are the first responders to infections.
- Dendritic cells: These cells have projections from their cytoplasm and are involved in not only phagocytosis but also processing foreign particles to assist with specific immunity.
Inflammatory Response:
- Inflammation is a complex protective response to tissue damage caused by pathogens or injury.
- It aims to achieve several goals:
- Reduce pathogen spread: Inflammation helps to limit the spread of pathogens, preventing them from invading healthy tissues.
- Remove damaged tissue: It clears away damaged cells and cellular debris.
- Initiate tissue repair: Inflammatory processes initiate the repair of damaged tissues.
Signs of Inflammation:
- There are four classic signs of inflammation:
- Redness: Increased blood flow to the affected area causes redness.
- Swelling: Increased vascular permeability allows fluid and immune cells to move into the tissue, leading to swelling.
- Heat: Increased blood flow results in a warm sensation.
- Pain: Stimulation of pain receptors in the affected area causes localized pain.
Steps of the Inflammatory Response:
- The inflammatory response includes several steps:
1. Mast cells activation: These specialized cells release histamine, heparin, and other chemicals when tissues are damaged.
2. Histamine action: Histamine causes vasodilation, which increases blood flow and the permeability of blood capillary walls.
3. Heparin function: Heparin prevents clotting in the immediate area of injury, forming a fluid clot around the damaged area.
4. Phagocyte attraction: Complement system proteins and mast cell chemicals attract phagocytes, particularly neutrophils, to the site of infection.
5. Pain sensation: Abnormal conditions in the tissue stimulate pain receptors, leading to the sensation of localized pain.
6. Phagocytic activity: Phagocytes engulf and consume pathogens and cellular debris.
7. Pus formation: Dead phagocytes and tissue fluid combine to form pus, a yellowish liquid.
8. Tissue repair: Inflammatory processes trigger the repair and regeneration of damaged tissue.
Chapter 7: The Body's Protection Against Infection
Key Concepts:
- Fever results from the body's increased temperature set point due to pyrogens acting on the hypothalamus.
- Fever can help fight infections but can be dangerous if it goes too high.
Fever:
- Infections often lead to a fever, where the body's thermostat is reset to a higher level.
- Pyrogens, such as interleukin-1, released by white blood cells, cause this temperature increase.
- Fever begins gradually, with the body responding by vasoconstriction and shivering to raise temperature.
- When the fever breaks, vasodilation and sweating occur, resetting the thermostat to normal.
- Fever can be beneficial, inhibiting the growth of some pathogens and speeding up body cell repair.
- However, extremely high temperatures can lead to convulsions and brain damage.
Immune Response:
- Immune responses are homeostatic mechanisms that protect the body from invading microorganisms.
- B-cells and T-cells, types of lymphocytes, play key roles in immune responses.
Antibody-Mediated Immunity (Humoral Immunity):
- B-cells are activated by antigens and differentiate into plasma cells.
- Plasma cells produce specific antibodies that circulate to neutralize antigens.
- Memory cells are formed for faster future responses to the same antigen.
Cell-Mediated Immunity:
- T-cells are responsible for cell-mediated immunity.
- They recognize and destroy infected body cells.
- Memory T-cells are formed to provide rapid responses upon re-exposure.
Antigens and Antibodies:
- Antigens are substances capable of triggering a specific immune response.
- Antibodies, produced by plasma cells, bind to antigens and neutralize them.
Types of Immunity:
- Immunity can be natural or artificial, and either passive or active.
- Natural immunity arises without human intervention, e.g., through previous infections.
- Artificial immunity results from interventions like vaccination.
- Passive immunity involves receiving antibodies produced by someone else, while active immunity involves the body making its antibodies.
Summary of Immune Responses:
- Antibody-Mediated Immunity (Humoral Immunity):
- Targets bacteria, toxins, and viruses outside body cells.
- Involves B-cells, plasma cells, antibodies, and memory cells.
- Antibodies neutralize antigens through various mechanisms.
- Cell-Mediated Immunity:
- Targets intracellular pathogens, transplanted tissues, and cancer cells.
- Involves T-cells, killer T-cells, helper T-cells, suppressor T-cells, and memory cells.
- Killer T-cells destroy infected cells directly, while helper T-cells assist immune responses.
Types of Immunity:
- Natural Active: Developing immunity through exposure to an infectious agent.
- Natural Passive: Receiving antibodies from another source, such as mother to baby.
- Artificial Active: Developing immunity through vaccination.
- Artificial Passive: Receiving pre-formed antibodies, e.g., through an injection.
Benefits of Immunity:
- Memory cells enable rapid responses upon re-exposure to antigens.
- Active immunity, whether natural or artificial, provides longer-lasting protection.
- Passive immunity provides immediate but temporary protection.
Questions:
- Specific immune defenses involve lymphocytes, B-cells, and T-cells.
- Antigens are substances that trigger immune responses.
- Antibodies are Y-shaped proteins produced by plasma cells.
- Antibody-mediated immunity involves B-cells, plasma cells, antibodies, and memory cells.
- Cell-mediated immunity is important against intracellular pathogens, cancer, and transplants.
- Antigen-antibody complexes can neutralize, agglutinate, or enhance phagocytosis.
- Helper T-cells promote and regulate immune responses.
- Memory cells allow rapid responses upon re-exposure to antigens.
- Immunity can be natural or artificial, and either passive or active.
Phagocytosis
Non-specific process performed by phagocytes (various white blood cells) to ingest and destroy pathogens.
Process
White blood cell (phagocyte) changes shape to engulf/ingest a pathogen, e.g. Bacteria
Lysosomes (an organelle containing digestive enzymes), release enzymes
Bacteria/pathogen breaks down and is killed
Inflammation
Non-specific process of increasing blood flow to an area where organ/tissue damage has occurred, where a pathogen may invade.
4 signs of inflammation
Redness
Pain
Swelling
Heat
Purpose
Defend against invading pathogens
Removes damaged tissue
Enable repair (mitosis)
3rd Line of Defence
The specific immune response
Antibody mediated (humeral mediated)
Cell mediated responses. due to T-cells and involves the formation of special lymphocytes that destroy invading agents. T-lymphocytes (cells) differentiate to become highly specialised T-cells e.g. cytotoxic/Killer T-cells
An antigen is any substance capable of causing or triggering a specific immune response. Can come in different forms particles/toxins/protein on the surface of pathogens
Our own body contains cells with antigens on the outside?
Antibodies - is a y shaped specialised protein that is produced by plasma cells in response to a non-self antigen.
Test Questions
4 Structual features of viruses and virus replication
Are viruses prokaryotes or eukaryotes? (Ans - None) Why?
No ribosomes
Mrs Gren
A cellular - No ribosomes no nucleus
Be able to draw an antibody
Nucleic Acid
Protein Coat
Size (tiny) 2-4 nanometers and include relative sizes of bacteria, fungi and protists
Classification through shapes
Draw and label immune system - 5 things given from Onenote diagram label
Bone and bone marrow
Lymph nodes - groin and arms
Phynus,