Photosynthesis:

The process driving ALL other ecological processes

CO₂+ H₂O + sunlight = O₂ + sugar

This includes all green plant parts, esp. upper if surfaces

• Oxygen waste products bubble out of aquatic plants

• There are typically numerous chloroplasts per cell

• Leaves have denser edges of the leaves for photosynthesis

  • More stomata for photosynthetic machinery

  • Every time a stomate is open- it pulls in food and the plant will lose water vapor by doing that. If it were on the upper surface, it would lose more water vapor being pointed towards the sun.

• Chloroplasts

  • Main function is the generate food/energy and send it out to the plant

  • Contain dense stacked membrane systems

    • Known as grana

    • There is stroma inside of the thylakoids

    • Their dark reactions happen in the cytoplasm in the cyanobacteria cell

  • More surface area allows for more function to happen (photosynthesis)

  • Chloroplasts can temporarily store sugar as needed

    • Chl a: Absorbs red and purple (in the visible light spectrum)

    • Chl b: blue-purple and small of orange light

• Carotenoids

  • accessory pigments that capture wavelengths that chlorophyll doesn’t

  • Present in cyanotes

  • carrots- red/yellow/orange

  • absorbs blue/green

• In the absence of Chl b: they have Phycobilins instead that pic up wavelengths that others cannot

  • Pick up what Chl a cannot

• Accessory pigments:

  • Capture wavelengths that chlorophyll doesn’t

  • Protect photosystems from UV damage

  • Plastid types:

    • Etioplasts

    • Chromoplast

    • Chloroplast

    • Leucoplasts

    • Amyloplasts

    • Elaioplats

    • Protienoplats

      • Anthocyanins- purple

Common protectors in tundra/high elevations

• Chlorophyll – EXPENSIVE

  • A: magnesium is limited, especially in highly eroded soils

  • B: has CHO- that is the only different from chl a and b

Typical Photosynthesis

C₃:

Mesophyll: photosynthesis leaf tissue

CO₂ enters leaf air spaces---🡪 then diffuses into chloroplasts

• a chloroplast is not unlike a cyanobacteria

Light reactions: membranes of thylakoids

• sunlight is used to rip protons from water with Oxygen as the by product

  • split water with photons to produce energy

• producing ATP (main function of the mitochondria)

• input: NADPH+

• waste: O2

• Hydrogen gets ripped off to be donated to be given to the NADPH+

dark reactions: in stroma

Rubisco enzyme fixes CO2 into a solid form; and ATP and NADPH convert solid C to food/sugar

• all happens without sunlight

• Known as the Calvin cycle- where gaseous CO2 is being used to make sugar

This form of Photosynthesis is called C3 because dark reactions have a 3-carbon sugar product

• Anything green is photosynthetic and also many things not green also do

  • Because the pigments present mask the green color underneath

• Stomata generally close at night- not all are aways open (not even close)

• Many systems in AR are competing for sunlight because it is a limiting factor

• Morn graph: must cross the threshold for photosynthesis to be profitable

  • In the shade, more surface area is needed to collect sunlight

Problem with C3: Rubisco is not specific

• Rubisco sometimes is not perfect; it sometimes performs photorespiration and consumes O2 while releasing CO2 (opposite of what is needed) meaning no ATP or sugars is produced

• This mistake is why there are not C3 plants in the desert.

A general photosystem:

• Embedded in the thylakoid membranes

• Proteins complexes that harvest sunlight

  • Where pigments are found

Photosystem II

• Water is split into O2 gas waste and 2H

• That is used to generate ATP (in ATP Synthase complex)

• The water is split by light energy

  • Light + H2O 🡪 ATP

Photosystem I

• Dependent on Photosystem II

• Uses its energy (ATP) produced to fuel its process – NADPH

  • Photosystems I and II occur in the thylakoid membrane: light reactions

    • Send ions from areas of high to low concentrations

    • Electrochemical potential gradient- mores the process

Eukaryotes

Green algae

• Monophyletic group (clade)

  • Any natural group; all descendants from a node/common ancestor

• Paraphyletic group:

  • Not including all descendants from common ancestor/node

• Green algae= paraphyletic

  • Because it does not include embryotic descendants

Ceae= family, anything else= genus

Synapomorphies of Plantae

1. Chlorophyll a & b in chloroplasts

2. Starch is storage product of photosynthesis, stored in chloroplast

3. 2-7 thylakoid membranes stacked in grana

4. Loss of phycobilin/phycobilisomes

Micromonas- green algae

• Eukaryote, single celled with a flagella

  • Pyrenoid present: helps concentrate CO2

  • Free living and free swimming

Ulvophyceae- green algae- variation in morphology

• Unicellular, colonial

• Filamentous

• parenchymatous (3D colonies; cell division in 3 planes)

• coenocytic (multinucleate: mitosis takes place without cytokinesis)

3 types of gametes among the green algae

1. Isogamy

2. Anisogamy

3. Oogamy- only one swims

Zoospores-

• can swim and establish new algae- asexual and divide using mitosis

• Algae are mostly haploid most of the time

Humans are diploid

Haploid- ln

Diploid 2n

Ulva- kelp/seaweed

• Densely packed with chloroplasts

• Known as products such as “sea lettuce”

• Multicellular

• Coenocytic=multinucleate

  • Nucleus divides without cell wall

• Cladophora

Valonia- bubble algae or sailor’s eyeball

Acetabularia

• Considered one cell (largest cells on the planet)

  • Entire organism only has 1 nucleus

Life cycles-

• Diplontic

  • Multicellular diploid stage

  • Ex: animals

• Haplontic

  • Most of the green algae

  • Unicellular zygote

  • Meiosis takes place in zygote

• Alternation of generations- unique to plants

  • Multicellular sporophyte and gametophyte (haploid and diploid stage)

  • Meiosis takes place in sporophyte

Myosis in zygote🡪 spore

Chlorophyceae- phycoplast

Phycoplasts:

• Microtubules

• Ensuring daughter

• Nuclei remain separated

  • Only in the Chlorophyceae in the Phylum

Phragmoplasts:

• Extra set of Microtubules serving as scaffolding for cell plate

Cyanobacteria lack flagella

Chlamydomonas have flagella

Green algae Plant Cell

• Pyrenoid

  • Helps accumulate/concentrate CO2

  • CO2 is LESS accessible underwater then in air

• Have vacuole

• Cell Walls

• Single celled

How Chlamydomonas reproduce:

• They become the gametes- monogamy

• Find compatible gamete

• Lock flagella- adhesion and fusion

• Projects cellular contents into the other

• Now have 2 contents and is a zygote (the diploid phase)

The zygote can stay dormant if necessary until environment is suitable

Miosis always results in 4 new cells, zoospores are the asexual version or can create gametes

These games then fuse and create zygotes – this is Haplontic (defined above)

Volvox- more green algae types

• Have flagella (2 per cell)

• Eyespot- can sense light and move toward it

• Autocolony- daughter colony

• Formed asexually- clones

• Flagella are formed on the inside of the autocology- how do they get oriented to the outside of the colony?

  • It self inverts! That is how they get to the outside – they flip inside-out!!

Hydrodictyon- multiple nuclei

Multinucleate cells

Oedogonium- filamentous

• Leaves behind scars from cell division (annular scars)

• Life Cycle