Sterilization, Disinfection, and Radiation

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Questions and Answers

In what decade did doctors begin handwashing, though without understanding its impact on microbes?

  • 1950s
  • 1780s
  • 1900s
  • 1840s (correct)

Which of the following processes completely eliminates all forms of life, including endospores?

  • Sanitization
  • Sterilization (correct)
  • Antisepsis
  • Disinfection

Why are gamma rays and X-rays considered dangerous forms of radiation?

  • They create free radicals that can cause DNA damage and destroy cells. (correct)
  • They emit non-ionizing radiation that is not strong enough to damage DNA.
  • They create thymine dimers in DNA, blocking replication.
  • They cause the vibration of molecules, leading to increased heat.

How does UV radiation primarily kill microbes?

<p>By creating thymine dimers in DNA, which block replication. (D)</p>
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Which of the following is an example of moist heat treatment that sterilizes?

<p>Autoclaving (C)</p>
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What is the primary mechanism by which alcohol kills bacteria?

<p>Disrupting membranes (B)</p>
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How do N95 masks effectively filter microbes?

<p>By using static-charged fibers to trap particles larger than 0.2 m. (C)</p>
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What is the function of chlorhexidine?

<p>To peel off cell walls. (B)</p>
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What is the main role of fluoride in preventing tooth decay?

<p>It strengthens teeth and kills bacteria. (D)</p>
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What are the primary functions that all cells must perform to facilitate growth?

<p>Make energy (ATP) from food and use that energy to build new cellular parts. (B)</p>
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What is the overall purpose of metabolism in a cell?

<p>To generate energy and build cell components (A)</p>
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What is the direct consequence of enzyme denaturation?

<p>Change in enzyme's shape, preventing it from functioning (B)</p>
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How does a competitive inhibitor affect an enzyme?

<p>It mimics the substrate and blocks the active site. (A)</p>
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What best describes the process of fermentation?

<p>ATP production from sugar without oxygen (B)</p>
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How does the amount of ATP produced by fermentation compare to that produced by aerobic respiration?

<p>Aerobic respiration produces significantly more ATP. (A)</p>
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What is the role of DNA polymerase in DNA replication?

<p>To copy DNA during replication. (B)</p>
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What is the main function of the mecA gene in S. aureus?

<p>It codes for a special protein that provides antibiotic resistance (MRSA). (A)</p>
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Which process involves making RNA from DNA?

<p>Transcription (A)</p>
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What best describes chemotaxis?

<p>Movement toward or away from chemical signals. (B)</p>
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In genetics, what are induced mutations?

<p>Mutations caused by mutagens, like UV light or X-rays. (C)</p>
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Flashcards

What is sterilization?

Removing all life forms, including endospores.

What is disinfection/antisepsis?

Reduces pathogens on a surface or tissue.

What is ionizing radiation?

Gamma rays and X-rays which create free radicals that damage DNA.

How do N95 masks filter?

N95 masks filter particles larger than 0.2 μm using static-charged fibers.

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What do standard masks do?

Block respiratory droplets, preventing the spread of disease.

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How does alcohol kill bacteria?

Alcohol disrupts membranes at 70-95% concentrations.

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How does chlorhexidine work?

Peels off cell walls, used as antiseptic.

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How do halogens work?

They form free radicals that damage cells; chlorine and iodine are examples.

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Where is fluoride found?

In toothpaste and water, it strengthens teeth, kills bacteria, and prevents cavities.

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Two tasks cells need to grow?

Make energy (ATP) and use it to build macromolecules.

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What is metabolism?

The sum of all chemical reactions in a cell to generate energy and build cell components.

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What is ATP?

Adenosine triphosphate, made by all living organisms.

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What is an enzyme?

An enzyme is a protein that catalyzes chemical reactions.

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Why is enzyme denaturation dangerous?

It changes the enzyme's shape, preventing it from functioning.

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Transcription vs. Translation?

Transcription makes RNA from DNA; translation makes protein from RNA.

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What is chemotaxis?

Movement toward or away from chemical signals.

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Mutation vs. horizontal gene transfer?

A mutation is a change in DNA sequence; horizontal gene transfer is DNA from another bacterium.

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What are thymine dimers?

UV-induced bonds between thymine bases that block DNA replication.

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Transformation, Transduction, Conjugation?

Transformation: uptake of external DNA. Transduction: DNA transferred by viruses. Conjugation: DNA transfer through pili.

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Why is conjugation concerning?

It easily spreads antibiotic resistance genes between bacteria.

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Study Notes

  • Doctors started washing hands in the 1840s to reduce sickness, not to intentionally remove microbes.

Sterilization vs. Disinfection

  • Sterilization removes all life forms, including endospores.
  • Disinfection reduces pathogens.
  • Disinfectants are for surfaces (e.g., bleach).
  • Antiseptics are safe for living tissue (e.g., alcohol).
  • Handwashing removes microbes through the physical action of soap and scrubbing.
  • Handwashing does not sterilize

Ionizing Radiation

  • Gamma rays and X-rays are two examples of ionizing radiation.
  • They are dangerous because they create free radicals that damage DNA and destroy cells.

UV Radiation

  • UV light kills microbes by creating thymine dimers in DNA, which blocks replication.
  • Microwaves are not reliably antimicrobial because they heat unevenly.
  • Powerlines and cell phones do not cause cancer because they emit non-ionizing radiation, which is not strong enough to damage DNA.

Moist Heat Treatment

  • Boiling and pasteurization disinfect but do not sterilize.
  • Autoclaving (121°C, 15 psi, 15 min) sterilizes and kills endospores.
  • Pasteurization is a brief heat treatment that kills spoilage bacteria in liquids like milk without damaging taste.
  • N95 masks filter particles larger than 0.2 μm using static-charged fibers.
  • Smaller filters aren't practical due to airflow restrictions.
  • Standard masks block respiratory droplets carrying microbes, preventing the spread of disease.
  • Alcohol kills bacteria by disrupting membranes and 70-95% concentrations are most effective.
  • Chlorhexidine peels off cell walls and is used as an antiseptic in mouthwash, body wash, and pet shampoo.

Halogens

  • Halogens like chlorine and iodine form free radicals that damage cells.
  • Chlorine can destroy endospores.
  • Iodine (e.g., Betadine) is used on the skin.
  • Fluoride is found in toothpaste and water, strengthens teeth, kills bacteria, and prevents cavities. It is considered safe.
  • Colloidal silver is an antiseptic silver solution.
  • Overuse can cause silver to deposit in skin, turning it blue (argyria).

Cell Growth

  • Cells must make energy (ATP) from food.
  • Cells must use that energy to build new cellular parts (macromolecules).
  • Metabolism is the sum of all chemical reactions in a cell to generate energy and build cell components.
  • ATP is the energy molecule produced during metabolism, made by all living organisms.
  • An enzyme is a protein that catalyzes chemical reactions, converting a substrate into a product at its active site.

Enzyme Denaturation

  • It is dangerous because it changes the enzyme's shape, preventing it from functioning.
  • Without enzymes, cells cannot survive.
  • Competitive inhibition involves an inhibitor mimicking a substrate and blocking the active site.
  • Amoxicillin blocks PBP enzyme, stopping cell wall formation.
  • Fermentation is ATP production from sugar without oxygen, occurring in the cytoplasm of bacteria and human muscle cells.
  • Only 2 ATP are made by fermentation, less than the 38 ATP produced during aerobic respiration.
  • Lactic acid (yogurt, sauerkraut) and ethanol + CO2 (beer, wine, bread) are examples of fermentation products.
  • Facultative anaerobes grow better with oxygen because they produce much more ATP via aerobic respiration.
  • The four nucleotides of DNA are Adenine (A), Thymine (T), Cytosine (C), and Guanine (G).
  • The central dogma of biology is DNA -> RNA -> Protein, where genetic information flows from DNA to RNA to protein.
  • DNA polymerase copies DNA during replication so that each new cell gets a copy.
  • The mecA gene codes for PBP2, making S. aureus resistant to antibiotics (MRSA).

Transcription vs. Translation

  • Transcription makes RNA from DNA.
  • Translation makes protein from RNA using ribosomes.
  • Ribosomes are made of protein and rRNA, and all life uses ribosomes to make proteins.
  • Chemotaxis is movement toward or away from chemical signals.
  • Bacteria swim toward food and away from toxins.
  • Quorum sensing is a chemical communication system used by bacteria to detect population density and form biofilms.
  • Life adapts to changes through mutations and horizontal gene transfer.
  • These alter DNA and allow survival under new conditions.

Mutation vs Horizontal Gene Transfer

  • Mutation is a change in DNA sequence passed to offspring
  • Horizontal gene transfer is DNA received from another bacterium.
  • Good mutations include white fur in polar bears (camouflage)
  • Bad mutations include antibiotic resistance in bacteria.

Mutations

  • Spontaneous mutations are random DNA changes during replication due to DNA polymerase mistakes.
  • Induced mutations are caused by mutagens like UV light or X-rays that damage DNA.
  • Thymine dimers are UV-induced bonds between thymine bases that block DNA replication.
  • This can kill the cell.

Transformation, Transduction, and Conjugation

  • Transformation is the uptake of external DNA.
  • Transduction is DNA transferred by viruses.
  • Conjugation is DNA transfer through pili.
  • Conjugation is concerning because it easily spreads antibiotic resistance genes between bacteria.

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