Unit 12 Review: Infectious Diseases

What are vectors of disease?

Vectors- organisms that carry pathogens from host to host, but are not sick themselves (ex. Ticks carry Lyme disease).

What are viroids, what do they infect, and how do they work?

Viroids cause disease in plants. Viroids are single-stranded RNA molecules that have no surrounding capsids. Viroids enter an infected cell and synthesize new viroids. They then disrupt the cell's metabolism and stunt the growth of the entire plant.

Envelope

protective coating on some viruses, made of proteins and lipids.

Capsid

protein coat around core; protects core from environmen

Ligands

receptor binding molecules on the surface of a virus- this is how they get "in" to cells.

Active immunity-

the kind you have once you have been exposed to a pathogen (either by getting an infection or a vaccine). It allows you to produce your own antibodies.

Passive immunity-

the kind you have when you receive pre-made antibodies from somewhere else. No lasting memory and short lived. Active lasts longer.

What are the 2 ways bacteria can produce disease in humans?

~Some bacteria damage the cells and tissues of the infected organism directly by breaking down the cells for food. ~Other bacteria release toxins (poisons) that travel throughout the body interfering with the normal activity of the host.

How are vaccines made? How do they work?

A vaccine is a preparation of weakened or killed pathogens. When injected into the body, a virus may prompt the body's immunity to the disease.

What is horizontal (lateral) gene transfer? What kind of DNA is involved? What are the 3 types of HGT that we discussed?

Horizontal gene transfer (HGT) refers to the transfer of genes between organisms in a manner other than traditional reproduction, which leads to genetic recombination. With bacteria, it usually involves plasmids. Bacteria use several methods of transferring or obtaining DNA, including: 1.Conjugation 2.Transformation 3.Transduction

What are the 3 groups/ways bacteria can release energy?

(cellular respiration only; require oxygen), obligate anaerobes (fermentation only; are harmed by oxygen), facultative anaerobes (either process)

What is happening during an allergic response? What causes most of the symptoms?

Allergies are an immune system reaction to harmless antigens. Some, such as pollen, may get in through the respiratory system. Fragments of food proteins may get through the digestive system. The next time these proteins are encountered, the immune system attacks them. Pollen is a harmless protein, yet we can become allergic to it. Most of the symptoms are caused by histamines released by mast cells. That is why antihistamines are used to treat allergies.

What are antibiotics? How do they work, and what are they effective against?

Antibiotics are drugs that can be used to destroy bacteria. Typically these compounds block the growth and reproduction of bacteria.

What is an antigen? Where do you find them, and what are they made of?

Antigen- a foreign substance (usually a protein, sometimes a polysaccharide) that your immune system responds to. They are on the surfaces of invaders such as pathogens.

What are viruses called that infect bacteria?

Bacteriophages (sometimes called just phages for short).

Describe binary fission.

Binary fission is a type of asexual reproduction in which bacteria replicates its DNA and divides in half, producing two identical daughter cells.

Describe the parts/structure of a typical eubacterial cell.

Cell wall made of peptidoglycan (which is made of protein and carbohydrate); cell membrane inside the cell wall, ribosomes to make proteins, DNA in nucleoid region (no nucleus). Some also have a capsule outside the cell wall.

What type of immunity takes over once a pathogen is inside your cells?

Cell-mediated.

What do helper T cells release that stimulates the immune response?

Cytokines.

Bacterial transformation and transduction have in common that bacteria take in foreign _____ (from the environment in ______, and from a bacteriophage in ___).

DNA; environment = transformation; phage = transduction.

What is conjugation? What temporary structure is used?

During conjugation, a hollow bridge forms between two bacterial cells, and genes move from one cell to the other. The bridge is called a pilus.

hat is function of the "first line of defense"?

Function: keep pathogens out of the body.

What is the role of histamines in an inflammatory response, and what type of cell releases them?

Histamines are released by mast cells; they attract phagocytes, dilate blood vessels so that more blood cells (including phagocytes, other white blood cells, and platelets/clotting factors) enter the site of the wound; and can also cause your airways to constrict (close off).

Which cells are part of humoral immunity? Which cells are part of cell-mediated immunity?

Humoral- B; cell-mediated- T.

Define pathogen.

Pathogen- any disease-causing agent (virus, bacteria, anything that makes you sick).

What are antibodies, and how do they work? Which B cell makes them?

Plasma cells release antibodies. Antibodies- proteins that recognize & bind to antigens. Antibodies work by binding to the antigens, which blocks the antigens from binding to your other cells, and clumping up the antigens- marking them for destruction. Antibodies can form these clumps because they are "Y" shaped- the 2 tops of the Y are both antigen binding sites.

Extra (not part of chromosome) DNA in bacteria is generally in the form of ___.

Plasmids

What are the 3 shapes of bacteria, and the 3 groupings? What would be the name of a cluster of round bacteria?

Shapes: Bacillus (rod shaped), coccus (sphere), spirillum (spiral) Groupings: Diplo (pairs), strepto (chains), staphylo (clusters) staphylococcus

What ways do viruses get into host cells?

al viruses enter cells through endocytosis after the viral ligands bind to host cell receptors. Enveloped viruses (those with lipid coating outside the capsid) also use endocytosis, and their lipid layer fuses with the host cell's plasma membrane.

Core

center made of viral DNA or RNA (instructions for making more viruses)

Describe the lytic cycle.

- In a lytic infection, a virus enters a cell, makes copies of itself, and causes the cell to burst. 1. Attachment Bacteriophage injects DNA into bacterium 2. Entry Bacteriophage DNA forms a circle 3. Replication Host cell can't tell the difference between host & viral DNA, so it transcribes viral mRNA, and then translates the mRNA into viral proteins, that chop the host cell's DNA to pieces, shutting down the host cell's normal processes. Then it uses the host cell's materials to make more viruses. 4. Assembly Virus protein and genetic material particles assemble into virus structure. 5. Lysis & release Virus enzyme lyses cell wall, or viruses bud out of cells without walls. Kills host cell and many new viruses go in search of new host cells.

why are bacteria important? (the "good" ones)

.Some are producers that capture energy by photosynthesis. .Others are decomposers that break down the nutrients in dead matter. .Some bacteria perform nitrogen fixation. .Still other bacteria have human uses. .We depend on bacteria for many things, including: -foods and beverages (yogurt, cheese, vinegar) -removal of waste and poisons from water -mining minerals from the ground -synthesis of drugs and chemicals via genetic engineering production of vitamins in human intestines (not to mention help digesting our food!)

What ways are diseases spread?

1.Physical contact 2.Indirect contact (droplet inhalation, 3.contaminated objects) 4.Contaminated food/water (food poisoning, bacteria, parasites) 5.Infected animals 6.Vectors

What are ways to control bacteria outside of the body?

1.Sterilization/pasteurization (both involve heat- sterilization = high heat for a long time, kills all bacteria; pasteurization is for food; high heat for short time; kills most but not all bacteria) 2.Disinfectants- kill bacteria on surfaces 3.food processing- refrigeration slows bacterial growth, cooking can sterilize some foods.

List and explain Koch's Postulates.

1.The pathogen should always be found in the body of sick organisms and never found in healthy organisms 2.The pathogen must be isolated from a sick organism and grown in a lab culture. 3.When the cultured pathogens are placed in a new host, they should cause the same disease that infected the original host. 4.The injected pathogen should be isolated from the second host, and it should be identical to the original pathogen.

What characteristics are used to classify eubacteria?

1.shape 2.the chemical nature of their cell walls (Gram + or -) 3.the way they move 4.the way they obtain energy

What do retroviruses have as genetic material? What special enzyme do they have? Which cycle do they follow? Give an example of a retrovirus.

RNA as genetic material; reverse transcriptase (enzyme) makes viral DNA from the viral RNA (the opposite of regular transcription, which is DNA RNA). They follow the lysogenic cycle; an example would be HIV.

What is antibiotic resistance? How do bacteria develop it, and once developed, how do they share it?

If a bacterium is resistant to a type of antibiotic, it means that it is not harmed by that antibiotic. Some bacteria are resistant to multiple antibiotics, which is even worse, and is a public health concern. Bacteria may naturally develop resistance to an antibiotic through a mutation or natural variation in their genes. Often, antibiotic resistance genes are carried on plasmids, and not in the bacterial chromosome. Plasmids are transferred through horizontal gene transfer methods.

How does a fever actually help you?

Immune system releases chemicals to raise your body temp when fighting infection. Higher temp kills bacteria that can't survive in that temp range. Higher temp also increases heart rate which pumps more blood to infection (including phagocytes).

Describe endospore formation.

In unfavorable growth conditions, many bacteria form spores. An endospore forms when a bacterium produces a thick internal wall that encloses its DNA and some of its cytoplasm. The endospore lies dormant until favorable conditions are found.

What is the germ theory of disease?

Infectious diseases are caused by microorganisms of different types (germs)

What are the three parts of the "second line" of nonspecific defenses?

Inflammatory response, fever, interferons.

What are interferons and how do they work?

Interferons- proteins produced by virus-infected cells that help other cells resist viral infection. Interferons inhibit the synthesis of viral proteins and help block viral replication.

What do memory B cells do?

Memory B cells remain in your body for a long time, and keep a record of pathogens you have encountered in the past. Long after the extra plasma cells are gone, you keep the memory B cells.

What makes up the rest of the "first line"?

Mucus membranes, mucus, cilia, digestive acids and enzymes, oil & sweat glands.

Can you treat a viral infection with antibiotics? Why or why not?

No, you can't. Antibiotics only kill bacteria, because they interfere with processes and structures bacteria have that viruses don't have.

Which cells engulf and destroy invaders?

Phagocytes, which include neutrophils and macrophages.

What are the 2 types of B cells?

Plasma cells & memory B cells

What are prions, what do they infect, and how do they work? Prions cause disease in animals.

Prions contain only protein—no DNA or RNA. Prions cause disease by forming protein clumps. These clumps induce normal protein molecules to become prions. Eventually, there are so many prions in the nerve tissue that cells become damaged. Prions build up in nerve cells and cause damage, mostly in the brain. The incubation period is long and prions induce otherwise normal proteins to fold incorrectly. Then, they stack up. Usually progress rapidly and always fatal.

What is organ rejection, and how does one overcome it?

Since all your cells have marker proteins on the surface that identify them as "self," what happens if you get a transplanted organ that displays marker proteins from someone else? Your killer T cells will recognize them as antigens and attack! (organ rejection)-- Unless you take drugs for the rest of your life to suppress your cell-mediated immunity so the killer T cells won't attack the new organ so you can keep it- which means that for the rest of your life, your immune system will be lowered, making it potentially difficult to fight off infections.

What 2 main types of lymphocytes recognize specific antigens?

T lymphocytes (T cells) and B lymphocytes (B cells).

Describe the inflammatory response. Know the 4 signs.

The inflammatory response (nonspecific) is a reaction to tissue damage caused by injury or infection. Damaged cells give off chemicals that attract mast cells. Inflammation is signaled by mast cells, which release histamine. Blood vessels near the site of injury expand, so more white blood cells enter. Many of them are phagocytes (including macrophages and neutrophils), which engulf and destroy bacteria. The phagocytes are attracted by an inflammatory response of damaged cells and histamines. Histamine causes fluids to collect around an injury to dilute toxins. This causes swelling. Infected tissue is often swollen and painful. The temperature of the tissues may rise, which can kill temperature-sensitive microbes. 4 signs: redness, swelling, increased temperature, pain.

do the ligands on the surface of a virus make it specific to its host? What are the ligands made of?

The ligands are extremely specific in the way they bind to the receptor on the surface of a host cell, like a lock and key, so it makes the type of cell a virus can infect very specific!! The ligand on the surface of the virus is like the "key" and a virus can only enter a cell that has a matching receptor ("lock.") Ligands and receptors are both made of protein.

1. Why are viruses not considered living?

Viruses are NOT cells—(remember that cells are the smallest things that can be considered alive)—viruses do not have organelles, they do not have a metabolism, and they cannot reproduce outside of a host cell.

What are some disease causing agents?

Viruses, bacteria, prions, viroids, parasites/worms, fungi, protists

What is your most important nonspecific defense?

Your skin—keeps out almost all pathogens as long as it is intact.

What is the job of your nonspecific defenses? What is included here?

_Nonspecific defenses- job is to keep pathogens out. -Include physical & chemical barriers -Do not discriminate between one type of pathogen or another

Viruses

are particles of nucleic acid, protein, and in some cases, lipids.

What are the 4 types of T cells? Describe each.

• Killer T cells- hunt down & destroy infected cells (the infected cells display a foreign antigen on their surface when a pathogen is inside- Killer T cells recognize it.) • Helper T cells produce memory T cells. • Memory T cells stick around after the infection to prompt a secondary response if the same pathogen ever returns. • Suppressor T cells shut down the killer T cells when their job is done.

Describe the lysogenic cycle. What is a provirus/prophage?

• Some viruses cause lysogenic infections in which a host cell makes copies of the virus indefinitely. In a lysogenic infection, a virus integrates its DNA into the DNA of the host cell, and the viral genetic information replicates along with the host cell's DNA. Some viruses can remain "latent" for months or even years before exiting the lysogenic phase. During this latency, some viruses are inactive, and others just appear inactive, but are really replicating and spreading. -Provirus, or prophage = the viral DNA when it's incorporated into the host cell's chromosome. Steps 1-2 are the same as the lytic cycle. Then, the viral DNA inserts itself into the host cell's genome (provirus). Cell division- every new cell contains the provirus/prophage.Eventually leaves lysogenic cycle to enter the lytic cycle- provirus/prophage pops back out of host cell's genome. Follows rest of lytic cycle from here- 6. Replication, 7. Assembly & 8. Lysis & release.