M250 EXAM 4 2026 FULL QUESTIONS WITH
SOLUTIONS GRADED A+
⩥ Sterilization vs disinfection vs antisepsis.
Answer: Sterilization removes all life; disinfection removes pathogens
on objects; antisepsis is disinfection on living tissue.
⩥ Microbicidal vs microbistatic.
Answer: Microbicidal kills microbes; microbistatic inhibits growth.
⩥ Primary target of heat, pH, heavy metals.
Answer: Proteins (denaturation).
⩥ Target of penicillin and lysozyme.
Answer: Penicillin blocks peptidoglycan cross‑linking; lysozyme breaks
NAG-NAM bonds.
⩥ Autoclave conditions.
Answer: 121°C, 15 min, 15 psi.
⩥ Pasteurization purpose.
Answer: Reduces pathogens; not sterilization.
,⩥ Dry heat vs moist heat.
Answer: Dry heat needs higher temperature and longer time.
⩥ Effect of cold on microbes.
Answer: Microbistatic; does not kill.
⩥ UV radiation damage.
Answer: Forms thymine dimers in DNA.
⩥ Why UV is not good sterilization.
Answer: Poor penetration; blocked by glass/organic matter.
⩥ Filtration pore size.
Answer: 0.22 µm (bacteria).
⩥ Alcohol disinfection mechanism.
Answer: Protein denaturation and membrane damage (60-90%).
⩥ Hydrogen peroxide killing mechanism.
Answer: Free radical damage.
,⩥ QAC target.
Answer: Cytoplasmic membrane.
⩥ Heavy metals mechanism.
Answer: Bind sulfhydryl groups, inactivate enzymes.
⩥ Gram+ vs Gram− dye susceptibility.
Answer: Gram‑positive more susceptible.
⩥ Phenol coefficient meaning.
Answer: Higher value = more effective disinfectant.
⩥ Definition of antibiotics.
Answer: Natural microbial products that inhibit other microbes.
⩥ Broad vs narrow spectrum.
Answer: Broad affects many; narrow affects few.
⩥ Beta‑lactam mechanism.
Answer: Cell wall synthesis inhibition.
⩥ Aminoglycoside mechanism.
, Answer: Misreading of mRNA at 70S ribosome.
⩥ Tetracycline mechanism.
Answer: Inhibits 70S ribosome.
⩥ Vancomycin target.
Answer: Gram‑positive cell wall synthesis.
⩥ Sulfonamides mechanism.
Answer: Folic acid synthesis inhibition.
⩥ Selective toxicity.
Answer: Drug harms microbe but not host.
⩥ Why antifungals more toxic.
Answer: Fungi are eukaryotic like humans.
⩥ Neosporin components.
Answer: Bacitracin, neomycin, polymyxin B.
⩥ Antiviral targets.
SOLUTIONS GRADED A+
⩥ Sterilization vs disinfection vs antisepsis.
Answer: Sterilization removes all life; disinfection removes pathogens
on objects; antisepsis is disinfection on living tissue.
⩥ Microbicidal vs microbistatic.
Answer: Microbicidal kills microbes; microbistatic inhibits growth.
⩥ Primary target of heat, pH, heavy metals.
Answer: Proteins (denaturation).
⩥ Target of penicillin and lysozyme.
Answer: Penicillin blocks peptidoglycan cross‑linking; lysozyme breaks
NAG-NAM bonds.
⩥ Autoclave conditions.
Answer: 121°C, 15 min, 15 psi.
⩥ Pasteurization purpose.
Answer: Reduces pathogens; not sterilization.
,⩥ Dry heat vs moist heat.
Answer: Dry heat needs higher temperature and longer time.
⩥ Effect of cold on microbes.
Answer: Microbistatic; does not kill.
⩥ UV radiation damage.
Answer: Forms thymine dimers in DNA.
⩥ Why UV is not good sterilization.
Answer: Poor penetration; blocked by glass/organic matter.
⩥ Filtration pore size.
Answer: 0.22 µm (bacteria).
⩥ Alcohol disinfection mechanism.
Answer: Protein denaturation and membrane damage (60-90%).
⩥ Hydrogen peroxide killing mechanism.
Answer: Free radical damage.
,⩥ QAC target.
Answer: Cytoplasmic membrane.
⩥ Heavy metals mechanism.
Answer: Bind sulfhydryl groups, inactivate enzymes.
⩥ Gram+ vs Gram− dye susceptibility.
Answer: Gram‑positive more susceptible.
⩥ Phenol coefficient meaning.
Answer: Higher value = more effective disinfectant.
⩥ Definition of antibiotics.
Answer: Natural microbial products that inhibit other microbes.
⩥ Broad vs narrow spectrum.
Answer: Broad affects many; narrow affects few.
⩥ Beta‑lactam mechanism.
Answer: Cell wall synthesis inhibition.
⩥ Aminoglycoside mechanism.
, Answer: Misreading of mRNA at 70S ribosome.
⩥ Tetracycline mechanism.
Answer: Inhibits 70S ribosome.
⩥ Vancomycin target.
Answer: Gram‑positive cell wall synthesis.
⩥ Sulfonamides mechanism.
Answer: Folic acid synthesis inhibition.
⩥ Selective toxicity.
Answer: Drug harms microbe but not host.
⩥ Why antifungals more toxic.
Answer: Fungi are eukaryotic like humans.
⩥ Neosporin components.
Answer: Bacitracin, neomycin, polymyxin B.
⩥ Antiviral targets.
