Lecture Notes Ch4: Membranes, Endospores, Evolution, and Eukaryotic Cell Organization

A set of Question-and-Answer flashcards covering membrane structure, endospores and sporulation, bacterial morphology, gene transfer, endosymbiotic theory, organelles in eukaryotes, plastids, and DNA patterns discussed in Chapters 1–6.

What is the Fluid Mosaic Model as it relates to the bacterial cell membrane?

A description of the cell membrane as a phospholipid bilayer with embedded, mobile proteins that regulate transport and signaling between the inside and outside of the cell.

What are the major components of the bacterial cell envelope mentioned, and which are associated with Gram-negative bacteria?

A plasma membrane, an outer membrane (present in some bacteria, notably Gram-negative), and a peptidoglycan layer; Gram-negative bacteria have an outer membrane in addition to a thin peptidoglycan layer, while Gram-positive lack the outer membrane and have a thicker peptidoglycan layer.

What is an endospore and why is it clinically significant?

A dormant, highly resistant form produced by some bacteria that allows survival under harsh conditions; makes certain bacteria hard to kill in healthcare settings.

What is sporulation and how does it differ from reproduction?

Sporulation is the formation of endospores for survival under stress, not reproduction; the vegetative cell can later germinate into a new bacterium when conditions improve.

What are the key structural components of an endospore and the cell that forms it?

Core containing DNA; spore coat; exosporium; dehydrated core for dormancy; the sporangium is the mother cell during endospore development.

What is meant by a vegetative cell in bacterial life cycles?

The actively growing, metabolically active form of the bacterium, not in the endospore state.

What are the three common bacterial shapes, and which example was given for the spherical form?

Coccus (spherical), bacillus (rod-shaped), and pleomorphic (variable shapes); Micrococcus luteus was given as an example of cocci.

What is lateral (horizontal) gene transfer and why does it complicate bacterial phylogeny?

The exchange of genetic material between bacteria across species, which makes tracing vertical evolutionary relationships (phylogeny) more difficult.

What is the Endosymbiotic Theory?

The idea that eukaryotic organelles like mitochondria and chloroplasts originated from engulfed bacteria that became permanent endosymbionts.

What evidence supports mitochondria and chloroplasts as endosymbionts?

They contain their own DNA and have double membranes; chloroplasts resemble cyanobacteria and perform photosynthesis, supporting a bacterial origin.

What are plastids and which types are discussed in the notes?

Organelles in plant cells involved in photosynthesis and pigment storage; chloroplasts (photosynthesis) and chromoplasts (pigment storage) are examples of plastids.

How do motor proteins and microtubules move cargo inside eukaryotic cells?

Motor proteins like dynein move along microtubules, powered by ATP, carrying cargo such as hormones and other molecules within the cell.

What are some key differences between plant and animal cells highlighted in the notes?

Plants have cell walls and plastids (e.g., chloroplasts) and chloroplasts for photosynthesis; animals lack cell walls but have mitochondria and cytoskeletal motor systems; both have nucleus and organelles with variations.

What does low GC content imply in DNA studies, as discussed in the lecture?

Patterns in DNA sequence due to base composition (low G/C content); can inform genome characteristics and aid in taxonomic classification and analysis.

What does the Huntington's disease example illustrate about DNA repeats?

A gene with CAG trinucleotide repeats; normal range is 0-35 repeats, while more than 35 repeats leads to disease; very high repeats (e.g., ~110) correlate with severe effects and earlier death.

What environmental example did the lecturer mention as a source of bacterial diversity and enzymes?

Yellowstone thermal vents and other extreme environments (heat, desiccation, chemicals, high salinity) that host extremophiles and novel enzymes.