energy

how to cope with environmental variation

energy!

what forms does energy exist in

• radiant energy - sunlight

• chemical energy - stored in the bonds of food molecules

• kinetic energy - associated with movement of molecules, proportional to temperature

autotrophs

• assimilate energy from sunlight (photoautotroph) or inorganic compounds (chemoautotroph)

  • energy is converted into chemical energy stored in the bonds of organic molecules

  • bacteria, protists, plants

heterotrophs

• obtain energy by consuming organic compounds from other organisms

  • this energy originated with organic compounds synthesized by autotrophs

• includes herbivores, preators, parasites, detritivores

• bacteria, protists, fungi, animals

autotrophy: chemosynthesis

• obtain e- and energy from inorganic compound

• synthesisze atp and nadph

• fix co2 into carbohydrates

• store for later use or biosynthesis

• oxidation, to calvin cycle reduction electron gain

autotrophy: photosynthesis

• obtain e- from H2O with energy from sun

  • oxidation e- loss light reaction

• synthesis ATP and NADPH

• fix CO2 into carbohydrate

  • calvin cycle reduction electron gain

• store for later use or biosynthesis

why are plants green?

• chlorophyll b gets red lights and chlorophyll a gets uv, blue, and purple

• reflect green because thats what they dont absorb

photosynthesis constraints: light

• rate of photosynthesis determines the supply of energy to a plant for growth and reproduction much adadptive pressure to maximize photosynthesis

• light response curves

  • light compestaion point: co2 uptake by Ps is balanced by co2 loss by respiration

  • saturation point: photosyntehsis no longer increases as light increases

• acclimatization to different light levels

sun vs shade leaves

sun leaves will have more cholorphylls, thicker leaves, more stomata because they can maximize the co2 is the limiting factor not, less lobed

constraints on photosynthesis: water

• tradeoff water conservation vs. energy gain and cooling

• closing stomates also increase light damage to leaf

  • reduced and excited oxygen species peroxides radicals

constraints on photosynthesis: temperature

• rate of chemical reactions increase

• structural integrity of mebranes light reactions take place across membranes

• acclimatization: changing properties of enzymes and membranes

constraints on photosynthesis: photorespiration

• rubisco

  • carboxylase: fixes co2 in the calvin cycle

  • oxygenase: takes up oxygen and breaks down carbon compounds releases co2 net energy loss

• balances depends on

  • ratio of o2 to co2

  • temperature more o2 bound when hotter

• photorespiration can protect the plant at high light elvels but it is generally a bad thing

  • at high temps in dry places plants close stomates o2 build up

c4 photosynthesis

• spatial separtion of CO2 fixation vs calvin cycle

• pep carboxylase

  • greater affinity for co2 compared to rubisco, no oxygenase activity

• higher water use efficiency

  • c4 plants can keep their stomates closed more because PEP carboxylase has such a high affinity for co2 can limit transpiration

cam photosynthesis

• temporal separation of CO2 fixation vs calvin cycle

• open stomates at night

  • take up co2 using pep carbocylase store the 4-carbon organic acid in vacuole

• close stomates during the dau

  • 4-carbon compound borken down co2 released in cell used in calvin cycle

heterotrophs

• obtain carbon from organic sources

• herbivores predators parasites detritivores

• food sources differ in chemistry and availability- tradeoffs

  • detritus is easy to obtain but low in energy live organisms are difficult to obtain but high in energy

  • animal cells are more energy rich compared to plants harder to obtain

    • herbivores have to eat more than carnivores, carnivores expend more energy hunting

water balance

• water is the medium in which all biochemical reactions necessary for life occur

• water content of organisms must stay between 60-90% body mass

• organisms must balance uptake and loss of water and solutes (salts)

hyoposmotic

environment less saline than an organism cells, what usally happens which allows for water to be pulled throuhgt roots then xylem as water potential decreases up the plant

isoosmotic soil and plant

same salinity, what they try to do at night so the plant can rehydrate and reah equilibrium

hyperosmotic soil

more saline in the soil so it has more water potential than the roots of the plant

• it will suck the water out of the roots

water potential

• is the overall energy status of water in a system

• water will move from a system of higher to lower water potential

• psi o = osmotic potential energy associated with dissolved solutes negative value)

• psi p = pressure potential (positive if pressure exerted)

• psi m = matric potential energy associated with attractive forces of the surface of cells or soil (negative value)

• psi v = humidity potential energy associated with humidity negative (drier is negative)

resistance to water potential

any force that impedes water movement

• sin, waxy cuticle of insects, plants

pore space

soil portion of the total soil volume not occupied by solid , mineral, or organic particles filled wth water or air

matric potential

• energy associated with atttractive forces on the surfaces of soil particles

sandy soils

• store less water and doesn’t hold on to it

• low matric potential\

• gets oxygen

silt

• in between sandy and clay size medium pore space and matric potential

fine soils

• store lots of water but holds it tight

• tiny pore space high matric potential

osmotic potential in soils

• importnat for marine soils and where salinization occures

mircroorganisms and osmotic adjustment

• they just have to adjust especially in transitional psaces like tide pools, banks, sandy shores, intertidal

• they acclimitize in response and syntehsize organic solutes its important for enzyme function

saline soil is what?

• it is hyperosmotic opposite of what we think because it sucks water out f plant roots, hypoosmotic means that roots would have high salinity than soil

day and night dehydration and rehydration in plants

• during the day stomates are open and transpiration creates a gradient, negative means they are being pulled

• at night the water potential is even in all parts of the plant and the soil, and stomates are closed

turgor pressure

• hydrostatic outward force the cell membrane’s liquids push against the cell wall due to water gained from osmosis

• for non woody plant species it is important for preventing wilting