Chapter 4 - Prokaryotic Cell Structure & Function II Flashcards
Prokaryotes have a _____ __________, which separates the cytoplasm from the exterior environment and allows the cytoplasm to have a chemical composition different from the environment
Cell membrane
Would life be possible without the cell membrane?
No, it would not be; compartmentalization is required for life
What are sterols?
Sterols are molecules in the membranes of eukaryotes that help fill the space caused by unsaturated fatty acid chains and help to maintain the correct fluidity of the membrane over a wide temperature range
Do prokaryotes have sterols in their membranes?
No; very few can make sterols, although a few in the animal body will incorprate host sterols into their membranes
What do prokaryotes have in place of sterols?
Hopanoids
What is the exception to the rule that prokaryotes lack sterols in their membranes?
Mycoplasmas
What are hopanoids?
They are pentacyclic compounds that fold into a shape similar to that of sterols; they are made from a sterol precursor, squalene; the pathway of squalene synthesis is nearly universal among cells, but prokaryotes and eukaryotes differ in the subsequent fate of squalene
What are hopanoids made from?
A sterol precursor called squalene
In prokaryotes, squalene is converted into _____________ while in eukaryotes it is converted into _____________.
Hopanoids
Sterols
The cell membrane is a two-dimensional __________.
Fluid
True or false? The forces that hold individual phospholipids together are weak.
True; it is because of these weak interactions that plasma membranes are fluid with components able to move laterally across the membrane
Although most components of the plasma membrane are fluid, some are not. What is one exception discussed in class?
FtsZ
What is the FtsZ ring?
A protein that starts cell division and is needed in the middle of the cell
What is required for molecules in the plasma membrane to be spatially oriented, meaning that they do not move?
They must be “anchored” in some way to limit their diffusion
The prokaryotic cell membrane has more ________ and different __________ than most membranes.
Protein
Proteins
Why does the plasma membrane of prokaryotes have so many proteins?
Because they lack the specialized membrane-bound organelles present in eukaryotes
Prokaryotic cells have to bring in nutrients and excrete wastes, but their membranes are impermeable to most polar compounds. How then do they get what they need into the cell and get rid of what they do not need?
Permeases
Most prokaryotes have membrane-embedded electron transport proteins to get _____________ from respiration or photophosphorylation.
Energy
What are three primary functions of prokaryotic cell membrane proteins?
- Membrane-embedded electron transport proteins to get energy from respiration or photophosphorylation
- Site of synthesis of cell membrane proteins, outer membrane proteins, periplasmic proteins, secreted proteins, lipids, and cell walls
- Contains sensory proteins that allow cell to determine certain aspects of the chemical or physical conditions in which it resides
Prokaryotic cell membranes are typically about ___% lipid by weight and ___% protein by weight; however, lipids weigh far less, so lipids outnumber proteins by __ to __.
25%
75%
30 to 1
Why do some prokaryotes invaginate their cell membranes?
To provide additional surface area, especially for those that have high respiratory and photophosphorylation rates
Most prokaryotes lack intracellular membrane-bound organelles; however, some prokaryotes do have membrane-bound organelles. The acidocalcisomes store __________ and the anammoxisomes oxidize ammonia and nitrate into _____________ _______.
Phosphate
Nitrogen gas
What is the ExPortal?
An organelle dedicated to the biogenesis of secreted proteins in Streptococcus pyogenes
Although bacterial and eukaryotic cell membranes are always phospholipid bilayers, _____________ cell membranes may be a bilayer or monolayer of ether lipids.
Archael