Microbiology Midterm Flashcards Flashcards

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Cell wall function

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The cell wall primarily provides structural support and protection and acts as a selectively permeable boundary that maintains cell shape and prevents lysis. In bacteria, peptidoglycan is a major component that contributes to rigidity and influences sensitivity to certain antibiotics. Different groups (Gram-positive, Gram-negative, mycobacteria) have distinctive wall chemistries that affect staining and pathogenicity.

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Glycocalyx

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The glycocalyx is an external carbohydrate-rich layer, often in the form of a capsule or slime layer, that surrounds some bacterial cells. It can serve as a virulence factor by preventing phagocytosis and aiding in adherence to surfaces and biofilm formation. Capsules are typically well-organized and contribute more to virulence than loose slime layers.

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Flagellum composition

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Bacterial flagella are primarily composed of the protein flagellin and are structurally distinct from eukaryotic flagella. Eukaryotic flagella contain microtubules arranged in a 9+2 pattern and are membrane-bound, whereas bacterial flagella are not surrounded by the plasma membrane and have a different rotary mechanism. This structural difference underlies functional and evolutionary distinctions between the two types.

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Endosymbiont theory

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The endosymbiont theory proposes that mitochondria and chloroplasts originated from free-living bacteria that were engulfed by ancestral eukaryotic cells and established a symbiotic relationship. Evidence includes double membranes, circular genomes, and prokaryote-like ribosomes in these organelles. This theory explains the bacterial ancestry of certain eukaryotic organelles.

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Biogenesis

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Biogenesis is the scientific principle that living organisms arise only from other living organisms, not from nonliving matter. This concept was supported by experiments that controlled for contamination and showed that life does not spontaneously appear in sterilized media. Biogenesis is a foundational idea in modern microbiology and biology.

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Leeuwenhoek

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Antoni van Leeuwenhoek is credited as the first person to observe and describe living microbes, which he called "animalcules," using handcrafted microscopes. His observations established microscopy as a powerful tool for studying the microbial world. Leeuwenhoek's work laid groundwork for later developments in microbiology.

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Jenner vaccination

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Edward Jenner developed the first successful smallpox vaccine by inoculating individuals with material from cowpox lesions to confer protection against smallpox. This approach demonstrated that exposure to a less virulent related agent could induce immunity to a deadly disease. Jenner's work is the historical foundation of modern vaccination.

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Ehrlich 'magic bullet'

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Paul Ehrlich's 'magic bullet' concept proposed that chemicals could be found that selectively target and kill pathogens without harming the host. This idea spurred the development of chemotherapy and antimicrobial agents, aiming for selective toxicity. Ehrlich's approach paved the way for targeted antimicrobial therapies.

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Virion

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A virion is the complete, extracellular form of a virus that is inert but transmissible between hosts. It typically consists of viral nucleic acid enclosed in a protein capsid, and sometimes an outer envelope, enabling protection and transmission. Virions are the infectious particles responsible for spreading viral infections.

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Capsid function

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The capsid is the protein shell that encloses and protects a virus's genetic material from physical and enzymatic damage outside the host cell. Capsids also play roles in attachment to host cells and in delivering nucleic acid during infection. Their structure is fundamental to viral classification and stability.

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Viral envelope

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A viral envelope is a lipid bilayer derived from the host cell membrane that surrounds some viruses, embedding viral glycoprotein spikes used for attachment. Envelopes are composed mainly of phospholipids and host-derived proteins, and they are typically acquired during the release (budding) stage of the viral lifecycle. The presence or absence of an envelope affects virus stability and modes of transmission.

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Retrovirus replication

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Retroviruses carry single-stranded positive-sense RNA genomes and use reverse transcriptase to synthesize complementary DNA (cDNA) from their RNA template. The cDNA is then integrated into the host genome, where it directs production of viral components that assemble into new virions. This replication strategy distinguishes retroviruses from many other RNA viruses and complicates treatment.

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Eukaryotic nucleus

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The presence of a membrane-bound nucleus is the defining characteristic of eukaryotic cells, separating genetic material from the cytoplasm. The nucleus houses chromosomes and coordinates processes like transcription and replication. Its compartmentalization enables complex regulation of gene expression in eukaryotes.

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Smooth ER

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The smooth endoplasmic reticulum is an organelle involved in lipid and steroid synthesis, detoxification, and calcium storage. Unlike rough ER, it lacks ribosomes and is not primarily responsible for synthesizing proteins for secretion. The smooth ER contributes to membrane biogenesis and metabolic processes in eukaryotic cells.

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Centrioles

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Centrioles are cylindrical structures composed of microtubules that form basal bodies for cilia and flagella and help organize the mitotic spindle during cell division in many eukaryotes. They play a role in cell polarity and cytokinesis in organisms that possess them. Centrioles are important for accurate chromosome segregation during mitosis.

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Bacterial membrane functions

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The bacterial plasma membrane is a selectively permeable barrier that mediates nutrient uptake, waste export, and houses enzymatic systems, including those for aerobic respiration. It lacks the phagocytic and endocytic capabilities of eukaryotic membranes and differs in lipid composition from some eukaryotic membranes. Membrane-associated enzymes and transporters are critical for bacterial metabolism and energy generation.

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Exam instructions

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Students are asked to turn off cellphones and put away books and notes before starting the exam, and to manage time wisely within the allotted period. If a student finishes early they should exit quietly after turning in the computer answersheet. These rules aim to maintain exam integrity and minimize disruptions.

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Answer key

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The provided exam instructions note that an answer key is available in the student lounge for review after the test. Students are typically instructed to turn in only their computer answersheet while retaining the questionnaire for self-assessment. This practice helps students check their performance after the graded period.

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Test format

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The exams include both True/False and multiple-choice sections, with True/False items typically worth one point and multiple-choice items worth two points each. Questions cover definitions, functions, and comparisons across microbiology topics including cell structure, viruses, and historical experiments. Understanding the format helps prioritize study and time management during the exam.

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Flashcard requirement

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Create concise flashcards where the front is a short term of one to four words and the back provides a clear definition in two to four sentences. Each card should attribute its source explicitly to allow verification and traceability. This format supports quick review and retention while maintaining academic transparency.