Plant and Animal Physiology Flashcards
ecosystem
Earth is a closed system with respect to matter, but open with respect to
energy – driven by the sun
what elements move around the earth in cycles through living organisms and nonliving
oxygen, carbon, nitrogen, phosphorous and sulfur
flux
the rate at which elements are moved through the cycle
pool
where elements accumulate
sinks
where elements are taken out of the cycle for a long time
photosynthesis
Evolved 2.5 bil yrs ago
• Converts sunlight energy to biological energy
cyanobacteria
earliest photosynthetic organisms, changed the atmosphere
so aerobic organisms could exist
atmosphere is made up of
mostly N (78%), some O (21%) and very little CO2 (0.03%)
CO2
most oxidized form of Carbon, also most stable
Organisms became able to reduce CO2
o Energetic uphill battle so used energy from the sun
• Made Carbon form CO2 useful for other organisms
photosynthesizers
Primary producers
o Solar energy enters the ecosystem through these organisms
o Use some of the energy they assimilate for their own metabolism – the
rest is available to consumers (net primary production)
Net primary production
a rough measure of energy flow through ecosystems
can be a measure of energy flowing in
Ocean and tropics are the most important – over 2/3 of the
world’s net primary production!
Carbon Cycle
All organisms contain carbon and their
energy comes from carbon compounds.
Carbon is removed from the atmosphere
as CO2 and incorporated into reduced
organic (carbon-containing) molecules
by photosynthesis.
Carbon is returned to the atmosphere as
CO2 by organisms in their metabolism
of reduced organic molecules.
where does carbon pool
in oceans
where does carbon sink
in fossil fuels and rocks
total production vs total consumption
CO2 production exceeds its consumption, but studies on global
warming must be analyzed skeptically
auxotrophs
producers
plants, algae, bacteria
photosynthetic organisms
Waste products of producers are fuels for consumers
formula of photosynthesis
CO2 + H2O +energy –> CH2O + O2
reduced form of oxygen (H2O) to oxidized form of oxygen
CO2 is oxidized, goes to reduced form (CH2O)
H2O is vary stable so it contributes to the energetic uphill battle
Heterotrophs
consumers (animals, fungi, bacteria)
Respiration (aerobic metabolism): O2 + CH2O –>energy + H2O
+CO2
heterotroph waste products are autotroph fuels
aerobic metabolism
•Energy is derived from carbohydrates. Oxygen from the
atmosphere is combined with carbohydrates to liberate the stored
energy. Water and carbon dioxide are waste products.
angiosperms
dominant plant life
3 types of vegetative organs: roots, stems, and leaves organized into shoot systems and root systems
shoot system
stems, leaves, flowers
Leaves: main organs for photosynthesis; absorb light and make sugar
stem: holds things together, holds leaves to face the sun; connections btw roots and leaves
root system
anchors plant, absorbs water and mineral nutrients; stores products of photosynthesis
water pathway in plants
water comes in through roots, moves up to leaves.
sunlight pathway
comes into leaves
CO2 pathway
enters through stoma on leaves
Photosynthesis (MAIN POINTS)
Synthesis from light
plants take in CO2, produce carbohydrates, and use water and release O2
Light is REQUIRED AS ENERGY SOURCE
6CO2 + 6H2O –>C6H12O6 + 6O2
Two pathways of photosynthesis
light reactions and light independent reactions
light reactions
convert light to ATP and NADPH
light independent reactions
use ATP and NADPH from the light reaction plus CO2 to
produce carbohydrates
light cycle
converting light energy into chemical energy
chloroplasts
similar to but different from mitochondria
have double membrane
thylakoid membrane
thylakoid membrane
has the proteins embedded that can absorb light
H2O:O2, ADP:ATP, NADP: NADPH
visible light
specific wavelengths that plants can absoorb
why are plants green
don’t absorb green, absorobs best around red or purple
absorption spectrum of chlorophyll is
smaller than the action spectrum of photosynthesis, proving there are other light absorbing molecules
stroma
blue space
thylakoid space
yellow space
chlorophyll
embedded in photosystem
similar to heme group in hemoglobin
magnesium in the middle causes all light except green to be absorbed, whereas iron in heme causes red blood cell to be green
what occurs at reaction center
light energy is converted to chemical energy
chlorophyll molecules (hydrophobic) are buried in photosystem
reducing agent at reaction center
excited chlorophyll-a molecule (Chl*); electron donor (loves electrons)
oxidizing agent at reaction center
A is an electron acceptor molecule (hates electrons)
reaction formula
Chl* + A–> Chl+ + A-
products of reaction center
Chl+ : loves electrons
takes electrons from water in photosystem II
A-: hates electrons
donates electrons to electron transport in Photosystem II
Net of photosystem II
ATP and O2
Photosystem II
Chl returns to ground state
2 e- are taken from H2O and oxidized Chl+ to Chl*
H2O becomes 1/2 O2 + 2H+
2H+ dumped into thylakoid membrane
Photosystem I
A- donates e- to NADP+
NADP+ + H+–>NADPH
all occurs in thylakoid membrane
Net of photosystem I
NADPH
low concentration of H+
stroma
high concentration of H+
thylakoid interior
Z scheme
another name for light reactions
CO2 fixation
inorganic CO2 reduced to be be useful for biological organisms aka CARBOHYDRATES
Enzymes in stroma (like NADPH reductase) use energy in ATP and NADPH to reduce
CO2 and make sugar
• CO2 fixation also takes place in light, since reactions before are light-dependent
Calvin and Benson
used 14C radioisotope to determine sequence of rxns in CO2 fixation
exposed chlorella to 14CO2 and then extracted organic compounds and separated them by paper chromotarophy
found only 3PG showed up on X-ray to detect radioactivity
paper chromatography
separates similar but different molecules/compounds
3PG
3-phosphoglycerate
3 carbon sugar phosphate
product of CO2 fixation, first compound to be formed
intermediate in glycolysis
Calvin cycle
pathway of CO2 fixation
steps of calvin cycle
CO2 is first added to an acceptor molecule — the 5-C Ru1,5P2
(Ribulose 1,5-bisphosphate);
6-C compound immediately
breaks down into two molecules of 3PG.
rubisco
ribulose bisphosphate carboxylase/oxygenase
enzyme that catalyzes intermediate formation
most abundant enzyme in the world
calvin cycle consists of 3 processes
1) Fixation of CO2
2) Reduction of 3PG to G3P
3) Regeneration of RuBP
2&3 are energy using steps
reduction
sugar production
acid to aldehyde
12 ATP and 12 NADPH
regeneration
6 ATP used
what does photosynthesis result in
only 5 percent
of total sunlight energy being
transformed to the energy of chemical
bonds.
Energy losses During Photosynthesis
From 100% Sunlight:
Only 50% absorbed by photosynthetic pigments
Only 30% absorbed due to plant structure
Only 10% efficiency in light reactions
Only 5% efficient in CO2 fixation pathways
