Lecture - Chapter 6 Plant Adaptations Flashcards
Sources of energy - Autotrophs
Assimilate energy from sunlight or from inorganic compounds.
The energy is converted into chemical energy stored in the bonds of organic molecules
Sources of energy - Heterotrophs
Obtain their energy by consuming organic compounds from other organisms.
This energy originated with organic compounds synthesized by autotrophs.
Radiant and chemical energy captured by autotrophs is
converted into stored energy in carbon-carbon bonds
Autotrophy
The earliest autotrophs were probably chemosynthetic bacteria or archaea - chemoautotrophs
The atmosphere was low in O2 but rich in hydrogen, methane and CO2.
Photosynthesis
Occurs in all green parts of a plant. The majority occurs in the leaves.
Chloroplasts
Photosynthesis occurs in these cellular organelles
Chlorophyll
The green pigments in the chloroplasts. It is a light absorbing pigment that plays a central role in converting light energy to chemical energy.
photon
a fixed quantity of light energy
mesophyll
In the elaves, chloroplaasts are found here. The carbon dioxide enters the mesophyll through the stomata and water reaches the mesophyll via the veins of the leaf from the roots
Outline the process of photosynthesis
6CO2 + 12H20 —light—> C6H12O6 + 6H20+ 602
Absorption spectra of plant photosynthetic pigments
Chlorophyll absorbs red and blue light and reflects green.
Accessory pigments such as carotenoids help harvest light energy and protect cells from intense solar radiation.
light reaction
light is harvested and used to split water and provide electrons to make ATP and NADPH
dark reaction
CO2 is fixed in the calvin cycle and carbohydrates are synthesized
carbon fixation
incorporation of CO2 into organic molecules
rubsico
A key enzyme in the calvin cycle.
It catalyzes the uptake of CO2 and synthesis of a 3-carbon compound.
Rubisco and chlorophyll requires a lot of nitrogen.
Rubisco is the most abundant enzyme on Earth.
Photosynthetic rate
determines the supply of energy which in turn influences growth and reproduction
Net photosynthesis =
Net photosynthesis = photosynthesis - respiration
light saturation point
value of photosynthetically active radiation (PAR) above whihc no further in crease in photosynthetic rate occurs
Light compensation point
net photosynthesis = 0
What limits photosynthetic rate?
Light
temperature
water availability
nutrients
light response curves show the influence of light on photosynthetic rate
CO2 gained in photosynthesis = CO2 lost in respiration
Chlorophyll
Higher chlorophyll allows more light to be harvested
increases under low light
Rubisco
enzyme needed to fix CO2
Can account for 40% of nitrogen in leaf
More needed when light is harvest - increase under high light
COST: increases n demand
Temperature influences photosynthesis
affects rates of chemical reactions
affects structure of membranes and enzymes
Variation in temperature
survival and functioning of organisms is strongly tied to their internal temperature
enzymes
metabolic reactions are catalyzed by enzymes which have narrow temperature ranges for optimal function
denatured
at high temperatures, enzymes become denatured, which destroys enzyme function
enzymes have asymmetric response to temperature
declining portion represents denaturation of protein - greater kinetic energy breaks hydrogen bonds
exponential portion = effect of molecular movement on interaction rate with enzymes
