Microorganisms and Infectious Agents

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Questions and Answers

What is one reason why viruses are unlikely to contaminate materials like gelatin?

Viruses thrive in liquid environments.

Viruses are large and multiply quickly.

Viruses are susceptible to heat and organic solvents. (correct)

Viruses have complex structures that include enzymes.

Which statement about prions is true?

Prions have a cellular structure.

Prions can induce structural changes in normal proteins. (correct)

Prions are easily inactivated by common disinfectants.

Prions possess nucleic acids.

What has contributed to the increase in antiviral drugs on the UK market since the mid-1980s?

The emergence of many bacterial infections.

The development of vaccines for all diseases.

The need for more antibiotics globally.

The HIV/AIDS pandemic. (correct)

What feature differentiates viruses from prions?

Viruses contain nucleic acids. (A) Signup and view all the answers

Which disease is linked to prion infection in humans?

Creutzfeldt–Jakob disease (CJD) (D) Signup and view all the answers

Why are antibiotics ineffective against viruses?

Viruses do not contain ribosomes. (D) Signup and view all the answers

What characteristic contributes to the stability of prions?

They are resistant to common sterilization methods. (C) Signup and view all the answers

In the context of disease causation, how do bacteria compare to protozoa and fungi?

Bacteria are responsible for a wider range of diseases. (A) Signup and view all the answers

What consequence arises from viruses having few enzymes in their structure?

Viruses rely heavily on host cell machinery for replication. (B) Signup and view all the answers

Which of the following statements about prions is least accurate?

Prions contain cellular structures. (B) Signup and view all the answers

What essential role do microorganisms play in the ecosystem?

They help in the decomposition of dead organisms. (D) Signup and view all the answers

Which of the following is NOT a characteristic of viruses?

They can reproduce independently outside a host. (A) Signup and view all the answers

Which type of microorganism is primarily responsible for spoilage in manufactured medicines?

Fungi (D) Signup and view all the answers

What is a significant feature of prions compared to traditional microorganisms?

Prions are simple rogue protein molecules. (C) Signup and view all the answers

How do probiotics protect the body from harmful bacteria?

They produce antimicrobial chemicals and compete for nutrients. (D) Signup and view all the answers

Why are viruses considered difficult to cultivate in a laboratory setting?

They must grow inside a host cell. (A) Signup and view all the answers

Which of the following statements about protozoa is true?

Protozoa are of pharmaceutical interest primarily as pathogens. (A) Signup and view all the answers

What distinguishes fungi from bacteria in terms of complexity?

Fungi can demonstrate sexual reproduction, whereas bacteria cannot. (A) Signup and view all the answers

What is the size range of the smallest common viruses?

20 nm to 200 nm (B) Signup and view all the answers

What is the primary consequence of bacteria reproducing asexually?

Bacteria rely more on mutations for genetic variation. (D) Signup and view all the answers

What is a notable exception regarding viruses and their range of hosts?

Rabies affects a wider range of species than typical viruses. (C) Signup and view all the answers

Why do antibiotic-resistant mutants have a greater chance of being selected during antibiotic treatment?

Bacteria grow rapidly but face selective pressure in the presence of antibiotics. (D) Signup and view all the answers

What role does the bacterial cell wall play in the survival of bacteria?

It protects against environmental pressure and affects nutrient uptake. (D) Signup and view all the answers

How do penicillins exhibit selective toxicity against bacteria?

They target enzymes involved in the synthesis of bacterial cell walls. (B) Signup and view all the answers

What allows antibiotics like tetracyclines to selectively target bacteria?

Bacterial ribosomes differ structurally from eukaryotic ribosomes. (C) Signup and view all the answers

How does the environment at an infection site affect bacterial growth compared to a Petri dish?

Bacterial growth is inhibited by the immune system and competition. (D) Signup and view all the answers

What is the significance of varying shapes and sizes of bacteria?

Differences aid in the classification and identification of bacterial species. (C) Signup and view all the answers

During which timeframe can one bacterial cell potentially become over 16 million cells?

8 hours (D) Signup and view all the answers

What is the primary advantage of bacteria having a cell wall compared to human cells?

It protects them against rapid changes in osmotic pressure. (A) Signup and view all the answers

What process do bacteria primarily use for reproduction?

Binary separation (B) Signup and view all the answers

What could be a disadvantage of the bacterial cell wall structure?

It can limit the types of nutrients that can enter the cell. (D) Signup and view all the answers

How quickly can some bacteria reproduce under optimal conditions?

In as little as 20 minutes (A) Signup and view all the answers

Which of the following statements accurately contrasts bacteria and human cells?

Bacteria can survive harsher environmental conditions than human cells. (C) Signup and view all the answers

What structural characteristic of bacteria allows them to withstand ultraviolet light and toxic chemicals better than human cells?

Rigid cell wall (D) Signup and view all the answers

In the context of microbial contamination, what fundamental difference between bacteria and mammals is critical?

Bacteria reproduce asexually while mammals reproduce sexually. (D) Signup and view all the answers

How does the structure of bacteria contribute to their survival when exposed to changes in osmotic pressure?

They have a protective cell wall. (D) Signup and view all the answers

What is a common misconception about bacterial growth compared to human cell growth?

Bacteria can reproduce without a mate, unlike human cells. (D) Signup and view all the answers

Which of the following is NOT a characteristic of bacteria that contributes to their robustness?

Ability to undergo photosynthesis (A) Signup and view all the answers

What is the approximate size range for bacteria in their longest dimension?

1–10 mm (C) Signup and view all the answers

Study Notes

Microorganisms

Microorganisms are essential for life on Earth, playing a vital role in the carbon and nitrogen cycles. Without them, decomposition of dead organisms and soil fertility would decrease.
Probiotic bacteria, a type of "friendly" bacteria, compete with disease-causing species for resources and attachment sites, hindering harmful bacteria from establishing infections. They produce antimicrobial chemicals to further limit infection.

Types of Infectious Agents

Infectious diseases can be caused by non-living agents, such as prions and viruses, as well as living microorganisms, like bacteria, fungi, and protozoa.
Prions are abnormal protein molecules that affect normal proteins, causing structural changes in those proteins leading to fatal nerve-degenerative diseases (e.g., "mad cow disease," Creutzfeldt-Jakob disease). Prions lack nucleic acids.
Viruses are parasites infecting various organisms (animals, plants, protozoa, bacteria). They consist of nucleic acid (DNA or RNA) and protein, but lack cellular structure. Viruses range significantly in size and structure. They are characterized by their narrow host range, requiring specific host cells for replication, making them difficult to cultivate in the laboratory; typically they are cultured in fertile chicken eggs or artificially cultured mammalian cells as hosts. Many only survive a short time outside host cells and are susceptible to heat and organic solvents. They can act as carriers (vectors) to carry genes to cells, such as in gene therapy. Though they may contain genes for enzymes produced by host cells, viruses generally possess few, if any, enzymes.
Bacteria are the simplest living cells, easily grown in the laboratory. They are the most studied microorganisms for a much of the 19th and 20th centuries. Typically spherical or rod-shaped, and are 1-10mm in diameter. Bacteria have a cell wall that protects them against osmotic pressure changes and drying, allowing them to survive longer periods in dust environments; this cell wall's structure is an important target for antibiotics (e.g., penicillins). Ribosomes in bacteria are different structurally from those in eukaryotic cells which can also be used for targeting with certain antibiotics. Despite conforming to a general prokaryotic description, they vary significantly in terms of form, size, and complexity. Individual bacteria can double in as little as 20 minutes, and large bacterial colonies are visible to the naked eye.
Fungi and protozoa are more complex than bacteria. Most fungi are not pathogenic (disease causing agents), but contaminants in manufactured medicines. Protozoa are mostly pathogenic; however, they are not usually spoilage organisms.

Additional Information

The image data shows examples of microbial entities and the ability of electron microscopy to examine small entities.
The largest common viruses, e.g. chicken pox, have a diameter of approximately 300 nm. Small viruses like the common cold virus have a diameter of approximately 20 nm. Elongated viruses like Ebola can have lengths up to 1400 nm with narrow widths..
Bacteria are often unaffected by antibiotics used against fungal and bacterial infections.
Bacteria can be resistant to various factors, such as UV light and toxic chemicals.

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Description

Explore the critical roles microorganisms play in ecological processes and human health. Learn about the different types of infectious agents, their mechanisms, and implications for diseases. This quiz delves into the complexity of life forms that influence health and the environment.