Cell Biology Quiz: Organelles in Cells

Cell Structure and Classification

• Eukaryotic cells contain organelles such as the nucleus, mitochondria, and chloroplasts (in plants).
• Plant cells have a distinct cell wall, differing from animal cells.

Prokaryotic and Eukaryotic Development

• Prokaryotes played a critical role in the evolution of eukaryotes through a process called endosymbiosis.
• Endosymbiosis involves a prokaryotic cell's internalization by an ancient Archaea, resulting in mitochondria and chloroplasts found in eukaryotic organisms.

Universal Tree of Life

• Cells can be classified into three domains based on ribosomal RNA genes, depicting evolutionary relationships.
• This classification method is applicable across all biological lineages.

Binomial Classification

• Species are identified using the binomial nomenclature system, consisting of the genus and species name (e.g., Pseudomonas aeruginosa).
• Further classifications within a species can be made using distinct strains, with a "type strain" representing typical characteristics.

Bacterial Reproduction

• Bacteria reproduce asexually via binary fission, which involves DNA replication and subsequent cell division into identical daughter cells.

Bacterial Cell Shapes

• Bacterial shapes include:
  • Cocci (spherical) – e.g., Staphylococcus aureus (causes boils, food poisoning).
  • Bacilli (rod-shaped) – e.g., Salmonella enterica (causes gastroenteritis).
  • Spirilla (spiral) – e.g., Treponema pallidum (causes syphilis).
  • Some bacteria lack a defined shape due to no cell wall – e.g., Chlamydia trachomatis (causes chlamydia).

Surface Structures of Bacteria

• Flagella enable locomotion and may function as sensory organelles.
• Pili/Fimbriae assist in adhesion and bacterial conjugation.
• Capsules act as virulence factors, protecting against phagocytosis.
• Slime layers aid in adherence within biofilms.

Cytoplasmic Structures in Bacteria

• The nucleoid contains chromosomal DNA.
• Inclusions serve various functions, while ribosomes are vital for protein synthesis.
• Plasmids are extrachromosomal DNA that play roles in pathogenicity and antibiotic resistance.

Endospores

• Endospores form in unfavorable conditions and act as "resting cells."
• They have a robust spore coat that ensures bacterial survival against extreme environmental stressors.

Bacterial Cell Wall and Gram Staining

• The cell envelope consists of the cytoplasmic membrane, cell wall, and an outer membrane in Gram-negative bacteria.
• The cell wall maintains structural integrity and aids in bacterial classification (Gram-positive vs. Gram-negative).
• Not all bacteria possess a cell wall, such as Mycoplasma.

Peptidoglycan Structure

• Peptidoglycan is a crucial component of bacterial cell walls, comprising alternating sugar chains (NAG and NAM) cross-linked by peptides.
• This structure is targeted by certain antibiotics and is considered a virulence factor.

Gram-Positive and Gram-Negative Bacteria

• Gram-positive bacteria possess a thick peptidoglycan layer (20-80 nm) and lack an outer membrane; they contain teichoic acids.
• Gram-negative bacteria have a thin peptidoglycan layer and an outer lipid membrane composed of lipopolysaccharides.

Factors Affecting Bacterial Growth

• Environmental factors influencing bacterial growth include temperature, pH, oxygen levels, nutrients, and water activity.
• Essential nutrients for bacterial life include carbon, nitrogen, sulfur, potassium, phosphorus, magnesium, oxygen, and calcium.
• Bacteria can be classified as heterotrophs (organic carbon users) or autotrophs (CO2 users). Some bacteria are non-fastidious, growing easily in basic media, while others are fastidious and require additional nutrients.### Modes of Transmission of Bordetella pertussis
• Microorganisms survive in air; however, many do not grow in air.
• Survival rates depend on factors like organism strength, temperature, UV exposure, humidity, and mucous encasement.

Transmission Sources

• Transmission can occur from humans, animals, food, soil, or water.
• Pathogens can spread through evaporation or disturbance of environments.

Aerosol Transmission

• Involves pathogen-laden droplet nuclei measuring 1-4 µm.
• Small droplets can travel over distances greater than 1 meter.
• Main sources include coughing, sneezing, and speaking.
• Surgical masks are not always effective against small droplet transmission.

Droplet Transmission

• Larger droplets (> 5 µm) are released and impacted more by gravity.
• These droplets travel shorter distances, generally less than 1 meter.
• Surgical masks are more effective in containing larger droplet transmission.

Contact Transmission

• Occurs through direct or indirect contact with a pathogen source.
• Direct contact includes person-to-person interactions (touch, kissing, sexual contact) and mother-to-infant contact during childbirth.
• Indirect contact involves transmission via contaminated inanimate objects (fomites), such as shared utensils, bedding, or water sources.

Vector-Borne Transmission

• Involves living transmitters (vectors) crucial to the transmission cycle.
• Most vectors are arthropods (insects) like fleas, mites, ticks, and mosquitoes.
• Examples include human malaria transmission via mosquitoes and bubonic plague transmission via rat fleas.
• Vertebrates can also serve as vectors; for instance, Hendra virus transmission involves bats, horses, and humans.

Notable Vector-Borne Diseases

• Mosquitoes transmit diseases including Yellow fever, Zika virus, Dengue fever, and Chikungunya.
• Ticks are responsible for Lyme disease.
• Rat fleas are vectors for the bubonic plague.
• Fruit bats transmit Hendra disease to horses and then to humans.

Importance of Understanding Transmission

• Knowledge of transmission methods is vital for disease prevention efforts.
• Case study illustrates the importance of understanding transmission routes: a patient diagnosed with a fungal infection and suspected scabies prompted thorough cleaning measures for all potentially contaminated items.

Test your knowledge on the essential organelles found within cells, including the nucleus, mitochondria, and chloroplasts. This quiz will explore the differences between prokaryotic and eukaryotic cells, as well as the unique features of plant cells such as the cell wall. Perfect for students learning about cell structure and function.