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List the three domains into which living organisms are classified. Are organisms in different domains related? Explain.

eukaryote, archaea, bacteria. the base of each domain diverged from a common ancestor roughly 3 billion years ago.


Describe and compare the basic cellular organization of prokaryotic and eukaryotic cells. Is one group organized while the other is not? Explain.

prokaryotes do not have membrane-bound organelles, while eukaryotes do (specifically a nucleus, hence the name). both are organised, grocery bag vs. backpack analogy.


In a single sentence, describe the basic structure of the cell membrane. Of what types of molecules is it composed, and how are they arranged?

a polar-permeable phospholipid bilayer interwoven with cholesterol, which acts as a kind of antifreeze, and integral (internal or transmembrane) and peripheral (surface) proteins, used for enzymatic functions, transport, and signalling.


In a single sentence, describe the basic function of the cell membrane.

form the bound between interior and exterior environment by regulating movement into and out of the cell.


Describe the fluid mosaic model of membranes.

a two-dimensional fluid structure of lipids with a mosaic of proteins embedded within.


Describe the semipermeable nature of the cell membrane.

membranes are selectively permeable, they allow certain substances to pass through unrestricted (such as water) and restrict others (such as polysaccharides).


Describe the key ways in which the bacterial cell membrane differs from its eukaryotic counterpart.

cell membranes in eukaryotes and bacteria are fundamentally similar, but differ in phospholipid composition. additionally bacterial membranes generally lack sterols, are more heavily in-folded, and are involved in energy transformations.



one of the proteolytic (breakdown of protein or peptides into amino acids) enzymes found in lysosomes and other body fluids (such as tears, saliva, etc.) that catalyze (breakdown) the protein wall of bacteria, especially gram positive bacteria, making lysozymes a vital part of our first-line defense against bacterial infection.



organelles that contain powerful enzymes to assist in destroying cellular debris and the breakdown of proteins, the last compartment of the endocytic pathway.


Why do you think the cell wall structures of archaea are more diverse than those of bacteria?

archaea inhabit a wide range of extreme environments


What are archaea cell walls made of?

they are very diverse. while none possess peptidoglycan, some possess pseudopeptidoglycan which acts in a similar manner.



gell like layer external to cell wall, found in many bacteria, generally formed of polysaccharides, some are made of polypeptides or a combination of both.


what are the two main forms of glycocalyx?

capsule (which is distinct and gelatinous), and slime layer (which is diffuse and irregular)


key functions of glycocalyx

attachment (enabling bacteria to adhere to surfaces and grow as a biofilm), protection from desiccation, avoid detection by host immune system (camouflages the bacteria cell surface to mimic those of host cells so that bacteria are not immediately detected).



any group of microorganisms in which cells stick to each other on a surface. these adherent cells are frequently embedded within a self-produced matrix of extracellular polymeric substance (hmmm, like a glycocalyx maybe?).


S strain bacteria

S. pneumoniae colonies that possess a glycocaylax, pathogenic. named for its smooth appearance under a microscope.


R strain bacteria

S. pneumoniae colonies that do not possess a glycocaylax, not pathogenic. named for its rough appearance under a microscope.



in some aquatic bacteria, a tube surrounding a linear chain of cells (like tennis ball tube packaging), serves to attach bacteria to solid objects to favourable substrates while protecting bacteria from predators.


name the types of filamentous appendages

flagella (plural flagellum), fimbriae (plural fimbria), pili (plural pilus)


where would one find a filamentous appendage?

anchored in the plasma membranes of bacterial cells, protruding form the surface, not enclosed by a membrane.


what are filamentous appendages made of?

hollow tubes of repeating proteins



long, hollow tubes of repeating proteins that extend beyond the cell surface, responsible for motility, can be used to identify and characterise some types of bacteria. (singular flagellum).


are bacterial flagella the same or different from eukaryotic flagella?

different in both structure and function, eukaryotic flagellum (or cilia, a similar structure) are covered by membrane whilst bacterial flagellum are not.


what are the basic components of flagella?

filament, hook, basal body


flagella filament

long, hollow shaft of identical globular modules of repeating protein (flagellin), secreted through the hollow core and built up in helical fashion


flagella hook

a bend in the flagella beyond the cell envelope


flagella basal body

the motor of the flagella, embedded in the cell


cell envelope

cell envelope refers to both the cell wall and cell membrane



the main protein that makes up flagella in bacteria



long, hollow tubes of repeating proteins that extend beyond the cell surface, responsible for motility, can be used to identify and characterise some types of bacteria. (plural flagella.