Microbiology Exam Review - Practice Flashcards (160)

160 practice flashcards covering key microbiology concepts from the lecture notes.

What theory did Koch contribute to that linked specific microbes to specific diseases?

Germ theory—the idea that specific microorganisms cause specific diseases, supported by Koch's postulates.

What classic experiment did Louis Pasteur and others use to disprove spontaneous generation?

The swan-neck (s-shaped) flask experiment showed that airborne microbes, not spontaneous generation, caused contamination; broken flasks allowed contamination.

What immunization concept did Edward Jenner popularize using cowpox to protect against smallpox?

Vaccination—exposure to cowpox conferred immunity to smallpox through cross-reactive antibodies.

Who is credited with developing a hierarchical system for naming and classifying organisms?

Carl Linnaeus (Linnaeus) and taxonomy.

What is the mnemonic for remembering the taxonomic ranks, and what does it stand for?

Does King Philip Come Over For Good Soup; Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species.

Which taxonomic rank comes directly after Domain?

Kingdom.

If two organisms share the same genus, are they more closely related than if they share the same species but different genus?

Yes, same genus indicates closer relatedness.

How should a scientific name be formatted correctly?

Genus capitalized, species lowercase, both italicized; or genus abbreviated with capital and a period (e.g., Es. coli).

Name the four methods used to identify microorganisms.

DNA sequencing ,Biochemical testing or staining.(check notes!!!!!!!!

What is a Gram-positive bacterial cell wall characterized by?

A thick peptidoglycan layer with teichoic acids and no outer membrane.

What distinguishes a Gram-negative bacterial cell wall?

A thin peptidoglycan layer plus an outer membrane containing lipopolysaccharide (LPS).

Which molecule embedded in Gram-positive cell walls contributes to the negative charge?

Teichoic acid.

Which molecule is a major contributor to the surface charge of Gram-negative outer membranes?

Lipopolysaccharide (LPS).

Which staining method is used to identify Mycobacterium due to its waxy cell wall?

Acid-fast stain.

Why are Mycobacterium difficult to Gram stain?

Because of mycolic acids in their cell envelope that resist decolorization.

Which genera are known for forming endospores?

Bacillus and Clostridium.

Which disease is associated with Clostridium botulinum spores?

Botulism (neurotoxin-mediated illness).

Under what conditions do endospores form?

Harsh conditions or nutrient depletion (stress; stationary phase).

What is the region in a bacterial cell where chromosomal DNA is located called?

Nucleoid.

Do bacteria have mitochondria?

No; energy production occurs at the plasma membrane.

What structures are used for DNA transfer during bacterial conjugation?

Sex pili (conjugative pili).

What are fimbriae primarily used for?

Attachment to surfaces (adhesion).

What is a capsule in bacteria?

A protective, well-defined outer layer that can aid in evading host defenses.

What is a slime layer?

A loose, extracellular coating that can help bacteria adhere and form biofilms.

What is a plasmid?

Small, circular DNA molecule separate from the chromosomal DNA that can carry accessory genes.

Name the four core cellular components typical of bacteria.

Plasma membrane, cytoplasm, DNA, and ribosomes.

Why is penicillin more effective against Gram-positive bacteria?

Because it targets the thick peptidoglycan cell wall and Gram-positive bacteria lack an outer membrane barrier.

What component contributes to the rigidity of the Gram-positive cell wall?

Peptidoglycan layer.

Which molecule in Gram-positive envelopes contributes to the negative surface charge?

Teichoic acid.

What components constitute the Gram-negative outer membrane?

Phospholipids and lipopolysaccharide (LPS).

What is the major anionic component of the Gram-negative outer membrane?

LPS (lipopolysaccharide).

Where would an obligate aerobe grow in a thioglycolate tube?

At the top where oxygen concentration is highest.

Where would an obligate anaerobe grow in a thioglycolate tube?

At the bottom where oxygen is absent.

Which category of organisms grows best at around 37 degrees Celsius?

Mesophiles.

Which organisms thrive in cold temperatures?

Psychrophiles (psychrophiles/microorganisms that prefer cold).

Which organisms grow best at high temperatures?

Thermophiles.

Which microbes grow best in very high temperatures ?

Hyperthermophiles.

What is the normal human body temperature in Celsius?

Approximately 37°C.

What does a neutrophile prefer in terms of pH?

Near neutral pH, around pH 7.

What does a neutrophile prefer in terms of temperature range?

Temperatures around human body conditions (mesophilic range).

What does CHNOPS stand for in microbial nutrition?

Carbon, Hydrogen, Nitrogen, Oxygen, Phosphorus, Sulfur.

What is chemostat

a device that maintains a steady-state culture by continuous addition of nutrients and removal of waste

What is a serial dilution used for in microbiology?

To reduce a sample to countable colonies and estimate CFU per mL.

What is the term for bacterial growth when nutrients become limited and waste accumulates?

Stationary phase.

When is antibiotic effectiveness typically highest in a bacterial growth curve?

During the exponential (log) phase when bacteria are rapidly dividing.

What is binary fission?

A method of bacterial reproduction where a cell elongates, DNA replicates, and divides into two identical cells.

What is fragmentation in bacterial reproduction?

A form of asexual reproduction where a cell splits into fragments that develop into new cells.

What is budding in bacteria?

Unequal distribution of cytoplasm and DNA leading to outgrowths that become new cells.

What are the three main ways bacteria can transfer DNA between cells?

Transformation, transduction, and conjugation.

What is transformation in bacteria?

Uptake and incorporation of naked DNA from the environment into the genome.

What is transduction in bacteria?

DNA transfer mediated by a bacteriophage (virus) that infects bacteria.

What is conjugation in bacteria?

DNA transfer between bacteria via a sex pilus (conjugative plasmid).

What is a bacteriophage?

A virus that infects bacteria.

What is an operon?

A cluster of genes regulated together by a single promoter and operator in bacteria.

What is a promoter in genetics?

A DNA sequence where RNA polymerase binds to initiate transcription.

What is the start codon for translation in the genetic code?

AUG, which codes for Methionine.

What are the three stop codons?

UAA, UAG, and UGA.

What is an anticodon?

A three-nucleotide sequence on tRNA that pairs with a complementary codon on mRNA.

What is a codon?

A triplet of nucleotides on mRNA that specifies a particular amino acid.

What is RNA’s nucleotide that replaces thymine?

Uracil (U) replaces thymine (T) in RNA.

What carries amino acids to the ribosome during translation?

Transfer RNA (tRNA).

What is the ribosome’s main function?

To synthesize proteins by translating mRNA into a polypeptide chain.

Where does transcription occur in bacteria?

In the cytoplasm (no nucleus).

Where does translation occur in bacteria?

In the cytoplasm at the ribosome.

What are the two main organelles in eukaryotic cells that contain their own DNA and ribosomes?

Mitochondria and chloroplasts.

What theory explains why mitochondria and chloroplasts exist inside eukaryotic cells?

Endosymbiotic theory.

What evidence supports endosymbiotic theory for mitochondria and chloroplasts?

They have their own DNA, double membranes, and ribosomes similar to bacteria; they replicate by binary fission.

What region of bacterial DNA is not surrounded by a membrane and is called the 'nucleoid'?

The area of chromosomal DNA in the cytoplasm, not a true nucleus.

What term describes the complete genetic content of an organism?

Genome.

What is the difference between chromosomal DNA and plasmid DNA in bacteria?

Chromosomal DNA makes up the main genome; plasmids are extra-chromosomal DNA that can carry accessory genes.

What are histones and where are they found?

Proteins around which DNA is wrapped in eukaryotes; bacteria do not have true histones.

What is the basic structure of DNA?

A double helix made of nucleotides with a sugar-phosphate backbone and paired bases (A-T, C-G).

What holds the two DNA strands together in the double helix?

Hydrogen bonding between complementary bases.

What three components make up a nucleotide?

A phosphate group, a sugar (deoxyribose in DNA; ribose in RNA), and a nitrogenous base.

What does DNA replication require to unzip the double helix?

Enzymes like helicase topo

Which enzyme seals Okazaki fragments on the lagging strand?

DNA ligase.

Which enzyme proofreads newly synthesized DNA?

DNA polymerase (has proofreading activity).

What enzyme destabilizes and relieves supercoiling ahead of replication forks?

Topoisomerase.

What enzyme is responsible for synthesizing new DNA strands by adding nucleotides?

DNA polymerase.

Which molecule carries genetic information from DNA to ribosomes for protein synthesis?

Messenger RNA (mRNA).

What is the first amino acid typically used to start protein synthesis in bacteria?

Methionine (via AUG start codon).

What is the term for a sequence on mRNA that marks where translation begins and ends?

Start codon (AUG) and stop codons (UAA, UAG, UGA).

What is the term for the three-nucleotide sequence on mRNA that encodes one amino acid?

Codon.

What is the term for the RNA sequence that pairs with codons during translation?

Anticodon.

What is a 'start site' region in bacteria where RNA polymerase begins transcription?

Promoter.

What is the region where repressor proteins can block transcription called?

Operator.

What is the overall process from DNA to a functional protein called?

Gene expression (transcription and translation).

What is the term for all genetic material in a cell?

Genome.

What is a 'nucleoid' region?

Region in bacteria where chromosomal DNA resides; not a true nucleus.

What is the difference between eukaryotic and prokaryotic DNA organization?

Eukaryotes have DNA wrapped around histones in a nucleus; prokaryotes have naked DNA (nucleoid) without a membrane-bound nucleus.

What region of a bacterial cell contains the chromosome and is not membrane-bound?

Nucleoid.

Which component is unique to Gram-negative bacteria and contributes to pathogenicity and immune response?

Lipid A component of LPS (endotoxin).

What type of bacterial structure helps evade phagocytosis and often contributes to virulence?

Capsule.

Which bacterium genus forms endospores and is a common cause of botulism?

Clostridium (botulinum) and bacillus

What is the function of teichoic acids in Gram-positive cell walls?

Contribute to the overall negative charge and cell wall structure.

What is the role of the bacterial outer membrane in Gram-negative cells?

Protects the cell and contains LPS; acts as a barrier to many antibiotics.

Which organism is typically stained with acid-fast stain due to a waxy coat?

Mycobacterium (mycolic acids in the cell wall).

What is an autotroph?

An organism that obtains carbon from carbon dioxide (CO2).

What is a heterotroph?

An organism that obtains carbon from others

What are the terms for microbes that require oxygen, tolerate it, or avoid it?

Obligate aerobes, facultative anaerobes, obligate anaerobes (and microaerophiles).