The Algae Flashcards
What are protists?
Any unicellular eukaryotic organism
* May also be defined as a member of the Protoctista, a
“kingdom” comprised of eukaryotic organisms that
don’t fit neatly into “plant”, “animal”, “fungi”.
Protoctista usually includes:
- algae, including multicellular seaweeds and other
macroalgae. - Diatoms, water moulds (oomycetes), protozoa, slime
moulds
What is algae?
Heterogeneous group of eukaryotic, photosynthetic
organisms of simple structure. Can be:
* Unicellular
* Multicellular
* Colonial
What does algae require?
an aquatic/damp habitat
algae are not…
- duckweeds
- Blue-green algae
- cyanobacteria
Example of unicellular algae?
Cyanidioschyzon
~1-2 µm
Example of colonial algae?
Volvox
1-2 mm
Example of multicellular algae?
Ulva lactuta -
a seaweed
10s of cm
What are the characteristics of red algae: rhodophyta?
- Large, multicellular
- Mostly marine
- No flagella at any stage - usually live
attached to substrate. - They are the source of agar
Red algae: Rhodophyta contains…
Phycoerythrin
What is Phycoerythrin?
Phycoerythrin - light harvesting protein pigment
* Absorbs blue light
* Reflects red light
Phycoerythrin allows…
… red algae to
photosynthesise in deeper water.
Describe Green algae: Chlorophyta
- Unicellular and multicellular
- Photosyntetic
- Mostly freshwater, some marine (e.g.
green seaweeds)
Green algae: chlorophyta is ancestral to…
plants - shared features:
* Chlorophylls a and b and carotenoids
* Store food as starch
* Cellulose cell walls
* Oxygenic photosynthesis*
Green algae examples?
1) Chlamydomonas reinhardtii
unicellular
2) Volvox carteri - colonial
3) Ulva lactuta - multicellular
Chlamydomonas is a …
… model organism
Why is Chlamydomonas a model organism?
- Unicellular
- Photosynthetic
- Easy to culture
- Genome sequenced
- Mutants available -
- Motility
- Light sensitivity
- Nutritional requirements
Characteristics of chlamydomonas?
- Paired flagella for
motility - Pyrenoid involved in
carbon dioxide fixation. - Eye spot involved in
light perception.
go look at 14
Why do clamydomonas have flagella?
- Turbulent water - get nearer to light
= positive phototaxis - Move away from light e.g when
photosynthesis saturated
= negative phototaxis.
what are phototaxis?
- photo = light
- taxis = move towards or away from stimulus
What detects light in chlamydomonas?
- Eyespot detects light.
What do chlamydononas need to differentiate for taxis?
- For taxis, need to differentiate which
direction the light is coming from.
How is the eyespot positioned in the cell?
The eyespot is asymmetrically positioned in the cell – part of the chloroplast
where is the eyespot localised?
localised near to a plasma membrane and closer to one flagella (cis) rather than the other (trans).
how does light hit the eye spot?
light hits lipid bodies containing carotenoid pigments – from one direction it is reflected back towards the plasma membrane at different wavelength. From the other direction it is blocked.
Light is reflected at a certain wavelength back
towards the …
… plasma membrane – here it is
perceived by 7 transmembrane proteins
related to rhodopsin called
channelrhodopsins
channelrhodopsins names?
CHR1 and CHR2
Two of these proteins (CHR1 and CHR2) are
associated with…
… retinal
Light causes change in…
… retinal to a different isomer.
Light causes change in retinal to a different
isomer.
* This causes a …
… conformational shift in the proteins which allows them to move cations through from the outside to the inside of the cell creating an electric current.
The voltage change is…
… transmitted along the membrane
There are voltage gated Ca2+
channels in the…
… flagellar membrane
There are voltage gated Ca2+
channels in the flagellar
membrane .
These open according to…
… the voltage in their location, allowing
Ca2+ ions to flood into the flagellae.
The Ca2+ ions interact with …
… dynein
arms in the flagella, causing
them to move.
Asymmetrical eyespot
percieves light, releases…
… Ca2+ ions
Asymmetrical eyespot
percieves light, releases Ca2+
ions.
This causes an influx of…
… Ca2+ ions into flagella.
Flagella respond differently -
…. one stops beating while the other continues, causing the cell to position towards the light.
As with many more ‘primitive’ eukaryotes the majority of the life cycle of Volvox is as…
… a haploid organism – a gametophyte
mostly reproduction is asexual
by …
‘budding’ of juveniles from
the parental colony.
Heat shock can induce …
… colonies to make a sex
pheromone which alters the
development of gonidia to
gametes rather than somatic
cells
Eyespots in the individual
cells are…
aligned – i.e. the cells are aligned so light entering from one direction can be translated into coordinated movement in the
colony
Cells differ between the
…
anterior pole (top) and the posterior pole (bottom):
- reduced eyespots in the posterior polar cells means
they do not respond to light and taxis is controlled by the
anterior part of the organism
In the multicellular green algae, Ulva,
there is an …
… alteration of generations between similar looking haploid
gametophytes and diploid sporophytes – this is known as
isomorphism.
What is Marine biofouling?
build up of unwanted marine organisms on
human infrastructure (bacteria, unicellular and
multicellular algae and barnacles)
What is biofouling detrimental to?
- Detrimental to water-related human activities – fishing
Costs caused by biofouling?
- Fuel costs (hydrodynamic drag) - US Navy alone ~$1
billion per year! - Hull cleaning required and repainting
where have algal blooms been observed?
- Observed in coastal waters in recent years
How do algal bloom form?
Human waste nutrients flow into the sea, cause rapid growth (blooms) of algae.
algal blooms disrupt…
… tourism and natural ecosystems
Zoospores of Ulva spp. are..
… motile (can swim).
Ulva spp attach to …
… surfaces by use of adhesive glycoproteins
secreted from vesicles
what are zoospores?
motile asexual spore that uses a flagellum for locomotion
Copper was placed on the hulls of ships as…
… an anti fouling mechanism
copper causes heavy metal toxicity in …
… marine organisms and is also bad for the environment.
In the 1970s tributylin (TBT) was used in paints but this was also shown to affect…
… non-target organisms - now mainly prohibited
What is used to reduce biofouling?
Low-drag and low-adhesion surfaces
what are foul release coatings used for?
allow fouling but cause easy release
with the motion of the ship.
Environmentally friendly chemical methods being developed -
degradable natural products, flocculating agents to prevent microscopic propagules from germinating.
Uses for algae
- Oil, gas reserves and coal reserves have been and are being depleted.
- We are currently seeing huge rises in fuel prices – gas and petrol for example
- Using these fuels is associated with greenhouse gas emissions
- Looking to reduce emissions – due to global warming / climate change.
Algae have potential as important alternative energy sources:
* Production of biodiesel
* Production of biohydrogen
One potential fuel to replace the
carbon economy is …
…hydrogen
It burns to release energy and
produces …
… no greenhouse gases.
But making hydrogen is…
energy
expensive
Hydrogen is currently produced by …
… electrolysis which requires energy to supply the electric current
During photosynthesis sunlight is used to…
… split water molecules producing oxygen (O2), electrons (e-) and protons (H+)
The protons are then used to…
… production of ATP and reduce NADP
to NADPH – they are then used to build carbohydrates in the Calvin
cycle.
Under certain conditions the protons can be recombined with…
… the
electrons to form hydrogen atoms
Under anaerobic conditions some
hydrogen is…
… naturally made by
Chlamydomonas.
- Under anaerobic conditions some
hydrogen is naturally made by
Chlamydomonas. - The enzyme that drives this is called
…?
hydrogenase
Photosynthesis causes…
… the splitting of water to produce molecular oxygen and also protons.
Photosynthesis causes the splitting of
water to produce molecular oxygen
and also protons –
the protons drive…
… ATP synthesis via a H+ ATPase in the
chloroplast membrane
Fe hydrogenase (HYD) is thought to
act as…
…an “electron pressure valve”
during electron transport converting
some H+ to molecular hydrogen
Fe hydrogenase is sensitive to…
… the presence of oxygen rendering it inactive
Depleting sulphur in an algal culture
decreases…
… the activity of photosystem
II, which decreases O2 production -
enabling hydrogen production instead.
What are the Problems with biohydrogen?
- The hydrogenase enzyme which converts protons
to hydrogen is intolerant of oxygen, but oxygen is
produced in photosynthesis. - Researchers attempting to genetically engineer
Chlamydomonas to tolerate higher oxygen levels. - Liquid cultures of Chlamydomonas get darker as
culture density increases, which reduces
photosynthesis and growth. - Engineer Chlamydomonas to be more transparent.
Whats an alternative to biohydogen ?
Biodiesel
Describe biodiesal?
- Grow algae in “bioreactor” to
harvest oils for fuel. - Fast-growing
- Easy to harvest
- Doesn’t use farmland
Problem with biodisel?
costs more energy to input CO2 and nutrients and
circulate algae than is output.
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