Lecture 1

Question 1

Where is the photosynthetic apparatus of cyano bacteria located?

Answer 1

situated mostly within folds of outer membrane - thylakoids

Question 2

What photosynthetic pigments do thylakoids contain?

Answer 2

chlorophyll, alpha-, beta carothen and xanothophylls

Question 3

What do thylakoids contain?

Answer 3

photosynthetic pigments and photosystems to harvest light

Question 4

What are the photosystems in thylakoids called?

Answer 4

phycobilisomes

Question 5

what do phycobilisomes do?

Answer 5

harvest light using unique light harvesting attenae even in poor light conditions

Question 6

What are phycobilisomes composed of?

Answer 6

phycocyanins and phycoerythrins

Question 7

How are cyanobacteria and prokaryotes similar?

Answer 7

• 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

Question 8

How is nitrogen fixed in cyanobacteria?

Answer 8

through assimilation of N2 into biomass ( only occurs in prokaryotes)

Question 9

When/where do cyanobacteria perform nitrogen fixation?

Answer 9

must be separated from photosynthesis in two ways:

• spatial separation
• temporal separation

Question 10

What occurs for cyano bacteria during spatial separation?

Answer 10

either bound to heterocytes or diazocytes

• heterocyte: clearly morphologically different
• diazoyate: not morphologically different (spatial separation only at spatial level)

Question 11

What occurs for cyanobacteria during temporal separation?

Answer 11

(day&night)

- nitrogen activity during dark period in the absence of photosynthesis

Question 12

What are well known examples of symbiosis of cyanobacteria with other organisms

Answer 12

most common nitrogen fixing: Nostoc and anabeana

examples: sponges, amoebas, protozoans

Question 13

What is the ecological importance of cyanobacteria

Answer 13

• waterblooms: masses of cyanobacteria producing commonly toxins
• nitrogen fixation &symbiosis
• geological agents of: travertines and stromatolites
• evolutionairy: change in atmosphere, endosymbiosis

Question 14

What is primary symbiosis?

Answer 14

• endosymbionts reducded their genome size transferring most of their genes to the host
• ultimately become organelles of the host cell

Question 15

What is secondary symbiosis?

Answer 15

• engulfment of the product of primary endosymbiosis

- particulary some algal groups (euglenophytes, haptophytes, etc.)

Question 16

What evidence is there to support endosymbiotic theory?

Answer 16

• 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

Question 17

How do eukaryotes differ from cyanobacteria?

Answer 17

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

Question 18

describe the structure of a plasmid

Answer 18

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

Question 19

What are the stages of plant plasmid

Answer 19

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

Question 20

describe structure of vacuoles

Answer 20

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)

Question 21

what is the function of vacuoles

Answer 21

development of tugor pressure and rigidity maintainance

Question 22

describe structure of microbodies

Answer 22

single membrane bound organelles which are around 1 micrometer, sometimes with crystalline protein body

Question 23

What is the function of microbodies

Answer 23

• associated w/ ER
  peroximes: associated with photorespitation, catalase to remove H2O2
  glyoxysomes: contains enzymes of lipid metabolism

Question 24

function of plant cell wall

Answer 24

• role in absorption, transport, secretion, active defense against pathogens

Question 25

composition of plant cell wall

Answer 25

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

Question 26

layers of plant cell wall

Answer 26

• 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