Cell Structure #2 Flashcards
Name the genus of one of the two ginormous prokaryotes discovered in the past few years.
Thiomargarita
Epulopiscium
Describe three general mechanisms by which compounds are transported into cells, and identify which are more important in prokaryotes or eukaryotes.
Fascilitated Diffusion: Eukaryotes (goes with conc. gradient, does not require energy) EUKARYOTE
Group Translocation: Modify compound upon take up (glucose for bacteria) BACTERIAL
Active Transport: expend energy to move against conc. gradient EUKARYOTE
- Describe a specific example of group translocation.
PEP phosphotransferase
PEP –> pyruvate (consuming a high energy bond, equivalent to ATP)
Adds phosphate to glucose, to prevent it from leaving
Phosphate goes from PEP –>
Enzyme I –>
Enzyme III –>
Enzyme II (Channel protein, passes phosphate to glucose-6 phosphate)
Describe two forms of active transport
Primary: Uses ATP to drive gradient
Secondary: Uses moving different ions across it’s favorable gradient to drive movement across a non favorable gradient
Describe two forms of active transport
Primary: Uses ATP to drive gradient
Secondary: Uses moving different ions across it’s favorable gradient to drive movement across a non favorable gradient
Describe the chemical structure of peptidoglycan, including three differences between Gram neg. and Gram pos. bacteria regarding the chemical composition of the peptidoglycan layer.
peptidoglycan structure:
acetylmuramic–acetylglucosamine
attached together
Muramic acid has a 4 peptide chain (ending with alanine)
3rd peptide is DAP or lysine, links too an alanine on another 4 peptide chain
3 differences
1, Gram+ uses lysine, attached to polyglycine chain, to connect to alanine (gram- use DAP)
2, Gram+ uses techoic acid anchors
3, Gram+ uses isoglutamine for its 2nd amino acid
Describe how the structure and function of the LPS layer differs from the plasma membrane.
Lipid A attached too
Core polysaccharide attached too
O side chain
O side chain can be modified to prevent immune recognition
Describe how the composition of the cell wall differs among groups such as bacteria, archaea, plants, animals, diatoms, and fungi.
Archaea: pseudo peptidoglycan (uses N-acetyl talosaminuronic acid instead of N-acetyl muramic acid)
Plants: cellulose, hemicellulose and pectin
Animals: no cell wall
Diatoms: use silica
Fungi: use chitin (long polymers of N-acetyl glucosamine)
- Compare and contrast the structure and movement of prokaryotic and eukaryotic flagella. Provide terms that describe the arrangement of flagella on the prokaryotic cell.
eukaryotes: flexible, uses a wip-like action, 20 microtubules in a 9+2 arrangement
prokaryotes: stiff, rotates with an engine like motion
amphitrichous: two flagella, one on each appex
lophotrichous: Multiple flagella on one apex
monotrichous: one flagella on one apex
peritrichous: Flagella scattered all across the bacteria
- Define chemotaxis. Describe how bacteria behave as they move along a concentration gradient. Describe the signal transduction that results in this movement. Describe the functions of Che A, B, R, W, Y, and Z, and whether the phosphorylated or non-phosphorylated forms are active.
No attractant present!!!
Nothing bound to MCP
Movement: tumble clockwise
CheA: autophosphorylates itself, phosphorylates CheY and CheB
CheY: will bind to flagellar basal body. Invoke clockwise movement
CheZ: dephosphorylates CheY, this results in a run, without attractant 50 - 50 run tumble ratio
CheB: Demethylates MCP, makes sure it is ready to bind a attractant should one appear
CheR: slowly adds methyl groups to MCP
Attractant Present!!!
Attractant bound to MCP
Movement: Counter Clockwise RUN
CheR: slowly methylates MCP, It must do this so the cell doesn’t simply respond to one signal ad infinitum, that’s it folks.
- Discuss the differences between the nuclear material of prokaryotes and eukaryotes.
Prok Circular. 1 chromosome generally ~4 mil bp. Supercoiling.
Secondary: Plasmids 5k-200k bp in size. Viruses if infected
Euk Membrane bound. Ploidy. Multiple chromosomes. 10-10000 x as much info as prok.
Linear strands. Lots of ‘unused’ space. DNA packed around Histone proteins in nucleosomes.
Secondary: Mitochondrial/chloroplast DNA. Maybe a plasmid (rare).
- Discuss at least five of the pieces of evidence discussed in class indicating that mitochondria and chloroplasts evolved from bacterial endosymbionts. Identify which of these are most convincing to you, and explain why.
Prok Mito Euk
Circular circular linear
70S 70S 80S
16S 16S 18S
double membrane double membrane single membrane
_____affected by antibiotics A____affected by antibiotics A____affected by antibiotics B_____
-Prokaryotes exist which are obligate endosymbionts (without the symbionts)
-Protozoant Cyanophora paradoxa has primitive chloroplasts called cyanelle with remnants of peptidoglycan between the two membranes.
- Describe several common storage compounds found in prokaryotes and what they store (e.g. energy, C, P, S, etc.).
Starch: stores C.
glycogen: stores carbon
PHB: poly B hydroxyl butyrate, stores C.
Volutin: Stores phosphate
Sulfur granules: stores sulfur
Carboxysomes: stores rubisco (involved in photosynthesis)
- Describe the role and structure of endospores. What physical and chemical characteristics make them so resistant and long-lived? Name two genera of organisms that produce endospores.
Cell acts as if it is going to replicate. Then instead incases replicated DNA in a spore, and degrades the rest of the DNA.
Exosporium Outermost layer of the cell, delicate coating. proteins, lipids, and carbohydrates
Spore coat Protein. Grants impermeability to chemicals.
Cortex Peptidoglycan: degrades upon germination
Core wall Peptidoglycan (structural)
Dehydration of spore 10-25% water, instead of 70-90% water
Impermeable coat.
Dipicolinic acid: found in spore, but not vegetative cell. Includes Calcium dipocolinate.
DNA binding proteins:
DNA repair enzymes: normal ones, including some activated by UV radiation.
Clostridium. Form endospore
Bacillus. Form endospore
