BIOL 261 - FINAL EXAM SHORT ANSWER QUESTIONS

Identify the components of prokaryotic and eukaryotic cell structure giving examples of each including the function and description of each structure. Identify the major contributors to the field of microbiology.

• Prokaryotic cell components:

  • Cell wall: provides structural support (e.g., peptidoglycan in bacteria)

  • Plasma membrane: controls movement of substances in/out of cell

  • Cytoplasm: site of metabolic activity

  • Nucleoid: area containing circular DNA

  • Ribosomes (70S): site of protein synthesis

  • Plasmids: small, circular DNA, often carrying antibiotic resistance

  • Flagella: for motility

  • Pili: used in attachment and conjugation

• Eukaryotic cell components:

  • Nucleus: contains DNA, site of transcription

  • Mitochondria: ATP production

  • Endoplasmic Reticulum (smooth and rough): protein and lipid synthesis

  • Golgi apparatus: modification and transport of proteins

  • Lysosomes: digestive enzymes for breakdown of waste

  • Ribosomes (80S): protein synthesis

  • Plasma membrane: regulates transport

  • Cytoskeleton: structural support and transport

Recall the processes of replication, binary fission, transcription, translation, and conjugation in bacteria.

• Replication: DNA is copied using DNA polymerase; semi-conservative.

• Binary fission: asexual reproduction in bacteria; DNA replicated, cell elongates, divides into two identical cells.

• Transcription: DNA → mRNA using RNA polymerase in the cytoplasm (no nucleus in prokaryotes).

• Translation: mRNA → protein using ribosomes, tRNA brings amino acids.

• Conjugation: transfer of plasmid DNA via sex pilus from donor (F+) to recipient (F−) cel

Identify the processes of transduction (general and specific), transformation and transfection.

• General transduction: bacteriophage accidentally packages host DNA and transfers it to another bacterium.

• Specialized transduction: phage integrates into host genome and upon excision takes some host genes with it.

• Transformation: uptake of free DNA from the environment by a bacterium.

• Transfection: introduction of foreign DNA into eukaryotic cells using chemical, physical or viral methods.

Differentiate lytic and lysogenic infections in bacteria and humans.

• Lytic cycle: virus infects, replicates rapidly, lyses the host cell (e.g., T4 bacteriophage).

• Lysogenic cycle: viral DNA integrates into host genome (prophage), replicates with host; can later enter lytic cycle (e.g., lambda phage).

• In humans:

  • Lytic: active viral replication (e.g., influenza, HIV during acute phase)

  • Lysogenic (latent): viral genome persists, reactivates later (e.g., herpes simplex virus)

Recall the steps involved in the cloning of a gene of interest in E. coli.

• Isolate gene of interest

• Cut gene and plasmid vector with the same restriction enzyme

• Ligate gene into plasmid using DNA ligase

• Transform E. coli with recombinant plasmid

• Select for transformants (e.g., using antibiotic resistance)

• Screen for expression or presence of gene

Recognize how mutations occur in bacteria and the possible results of the mutations including specific examples of mutagens.

• Mutations: changes in DNA sequence

• Can occur spontaneously or via mutagens

• Mutagens:

  • Physical: UV light (thymine dimers)

  • Chemical: nitrous acid, base analogs

  • Biological: transposons

• Results:

  • Silent mutation (no change in protein)

  • Missense mutation (amino acid change)

  • Nonsense mutation (premature stop codon)

  • Frameshift mutation (insertion/deletion)

Differentiate classical and serological identification of bacterial, viral, fungal and parasitic human pathogens.

• Classical identification:

  • Culture, staining (Gram stain, acid-fast), microscopy, biochemical tests

• Serological identification:

  • Detect antigens or antibodies using tests like ELISA, agglutination, Western blot

  • Faster, does not require culturing

Distinguish between innate, humoral and cell mediated immunity.

• Innate immunity:

  • Non-specific, immediate

  • Includes physical barriers (skin), phagocytes, NK cells, inflammation, complement

• Humoral immunity (adaptive):

  • B cells produce antibodies specific to antigens

  • Memory B cells provide long-term protection

• Cell-mediated immunity (adaptive):

  • T cells target and kill infected or cancerous cells

  • Helper T cells (CD4+) activate other immune cells

  • Cytotoxic T cells (CD8+) destroy infected cells

Recall how food and water are made safe to consume.

• Food safety:

  • Pasteurization (e.g., milk)

  • Cooking to proper temperatures

  • Refrigeration and freezing

  • Preventing cross-contamination

  • Canning and preservatives

• Water safety:

  • Filtration

  • Chlorination (kills pathogens)

  • UV treatment

  • Monitoring for contaminants and pathogens (e.g., coliform testing)