Lecture 1 Flashcards
Where is the photosynthetic apparatus of cyano bacteria located?
situated mostly within folds of outer membrane - thylakoids
What photosynthetic pigments do thylakoids contain?
chlorophyll, alpha-, beta carothen and xanothophylls
What do thylakoids contain?
photosynthetic pigments and photosystems to harvest light
What are the photosystems in thylakoids called?
phycobilisomes
what do phycobilisomes do?
harvest light using unique light harvesting attenae even in poor light conditions
What are phycobilisomes composed of?
phycocyanins and phycoerythrins
How are cyanobacteria and prokaryotes similar?
- are simple and DNA is devoid of histones
- true cell organells (e.g. golgi apparatus, mitochondria) are absent
- both have cell walls that contain muramic and diaminopimeltic
- mostly unicellular
- reproduction asexually via binary fission
- no flagella (but some species capable of gliding
How is nitrogen fixed in cyanobacteria?
through assimilation of N2 into biomass ( only occurs in prokaryotes)
When/where do cyanobacteria perform nitrogen fixation?
must be separated from photosynthesis in two ways:
- spatial separation
- temporal separation
What occurs for cyano bacteria during spatial separation?
either bound to heterocytes or diazocytes
- heterocyte: clearly morphologically different
- diazoyate: not morphologically different (spatial separation only at spatial level)
What occurs for cyanobacteria during temporal separation?
(day&night)
- nitrogen activity during dark period in the absence of photosynthesis
What are well known examples of symbiosis of cyanobacteria with other organisms
most common nitrogen fixing: Nostoc and anabeana
examples: sponges, amoebas, protozoans
What is the ecological importance of cyanobacteria
- waterblooms: masses of cyanobacteria producing commonly toxins
- nitrogen fixation &symbiosis
- geological agents of: travertines and stromatolites
- evolutionairy: change in atmosphere, endosymbiosis
What is primary symbiosis?
- endosymbionts reducded their genome size transferring most of their genes to the host
- ultimately become organelles of the host cell
What is secondary symbiosis?
- engulfment of the product of primary endosymbiosis
- particulary some algal groups (euglenophytes, haptophytes, etc.)
What evidence is there to support endosymbiotic theory?
- loose bond between chloroplasts and host in e.g. some Euglena protozoans (chloroplasts can be destroyed without killing the cell)
- plastids and mitochondria are formed by binary fission
- have their own ss circular DNA and smaller ribosome
- surrounded by more than one membrane
- plastids are present in unrelated groups of prostists, while some of closely related prostists lack them
How do eukaryotes differ from cyanobacteria?
Eukaryotes have:
- DNA associated with histones to form chromosomes, which bounded in a nucleo membrane
- compartmentalization of protoplast (nucleus and membrane bound organelles)
- cytoskeleton
- flagella of the 9+2 microtubules
- integrated multicellularity
- sexual reproduction
describe the structure of a plasmid
envelope of more than 2 membranes
- differentatiation into system of membranes - stacks of disc-like thylakoids (grana) + intergrana thylakoids (stroma);
- stores starch grains, oil droplets
- has nucleoids - region containing circular DNA
What are the stages of plant plasmid
1) development of chloroplast from proplastid (few or no internal membrane)
2) proplastid differentiates, and flattened vesciles form from inner membrane and eventually allign with grana/stroma thylakoids
3) thylakoid system of mature chloroplast appears discontinuous with the envelope
5) may develop into chromoplasts and leucoplasts
describe structure of vacuoles
single vacuolar membrane (tonoplast) cell sap
- originally made of many small vacuols which gradually fuse and increase up to 90% of volume in mature cell
(energy saving and large surface between cytoplasm and external environment)
what is the function of vacuoles
development of tugor pressure and rigidity maintainance
describe structure of microbodies
single membrane bound organelles which are around 1 micrometer, sometimes with crystalline protein body
What is the function of microbodies
- associated w/ ER
peroximes: associated with photorespitation, catalase to remove H2O2
glyoxysomes: contains enzymes of lipid metabolism
function of plant cell wall
- role in absorption, transport, secretion, active defense against pathogens
composition of plant cell wall
cellulose: crystalline structure of molecules united into micelles
- these build up microfibrils, which build up macrofibrils
- this forms a matrix of non cellulosic molecules to embed fibrils
layers of plant cell wall
- middle lamella: pectin layer, cementing the cell walls of adjoining cells
- primary wall: the rigid skeleton, unevenly thickened: primary pit fields
- secondary wall: not in all plants of cellulose, hemicellulose, lignin & others (after primary wall stop growing, very rigid, strengthening, water conductive cells)
- cuticle: protective layer covering the surface of cells
