MIC 102 Exam Questions with Correct Answers

MIC 102 Exam Questions with Correct Answers What are the three main subgroups of Eukaryotes? - Answer-Algae, Protozoa, Fungi What subgroup does Algae and Protozoa make? - Answer-Protists DESCRIBE THE ROLE OF A PLASMA MEMBRANE AND A CELL WALL. - AnswerWhat's the difference between Basic & Differential Stain? - Answer-Basic Stain: Allows you to determine the basic structure of a bacteria (rod, etc) Differential Stain: Uses more than one stain -- most popular: the gram stain. Why would the cell wall be an important target for antibiotics? - Answer-Because the cell wall of Prokaryotes (like bacteria) has peptidoglycan, which is not found in Eukaryotes. The structure that defines the existence of a cell is the _____ - Answer-cell membrane Differences between Gram-Positive & Gram-Negative cells: - Answer-Positive: - during staining, it retains a dark purple stain after the decolorizer step - THICK. has 5 or more layers of peptidoglycan (which is why it stays purple. more layers.) -its peptidoglycan units - NAG & NAM are joined INdirectly via Pentaglycine bridge. Negative: - during staining, it eventually becomes colorless after the decolorizer step - has only 1-3 layers of peptidoglycan - its peptidoglycan units - NAG & NAM - are joined directly Archaea live in extreme conditions. What helps them accomplish this? - Answer-- having ether linkage (more stable instead of ester) - methylated groups - tighter bonds - monolayer instead of bilayer - stronger - inserting/fusing ring structures O2 & CO2 can easily pass through membrane via passive transport (aka diffusion) - Answer- If you have a high [solutes] inside the cell, water will rush in, pressure builds up, and bacterial cell may lyse. What can help prevent this? - Answer-Cell wall! - provides rigidity - antibiotics can "hurt" the cell wall, resulting in the cell to burst, bc most bacterial cells are found in hypotonic solutions (more solutes inside, less solutes outside) mycoplasmas, have a cell membrane with ______ - Answer-no outer layers. (rare) Gram-Negative bacteria have inner and outer leaflets in their outer membrane. Describe their composition. - Answer-Inner leaflet: contains phospholipid bilayer Outer leaflet: composed of LPS (lipopolysaccharide) Most bacterial cell walls are made up of _________ - Answer-peptidoglycan (or murein). -- which is basically a polysaccharide of repeating subunits of NAG & NAM for GRAM-NEGATIVE BACTERIA: In order for the cross-links between the repeating units N-acetylmuramic acid (NAM) & N-acetylglucosamime (NAG) to occur, what important step must happen? - Answer-The terminal D-Alanine group must be cleaved off in order for the cross-links to form How does Penecillin work? - Answer-It inhibits TRANSPEPTIDASE (which is the enzyme that forms the cross-links found in peptidoglycan, the structure base for the cell wall.) -- thus it weakens the cell wall **vancomyecin BINDS to terminal group What function does a "capsule" provide? - Answer-It prevents the bacterial cell (both + and -) from undergoing phagocytsosis by macrophages. (bad for us) Mycobacteria have _____ cell envelopes - Answer-Complex! (drawback -- harder for nutrients to get in) he inward-facing leaflet of the outer membrane includes - Answer-lipoproteins that connect the outer membrane to the peptide bridges of the cell wall -- w/out this lipoprotein cell wouldn't be able to divide