Chapter 8 Flashcards
is energy ever created or destroyed?
no, it just changes forms
where the energy for life ultimately come from?
photosynthesis
what is the equation for photosynthesis?
6CO2 + 6H2O ————> C6H12O6 + 6O2
LI) (LD) (sunlight) (LI) (LD
what is the relationship between the chemical equations for photosynthesis and cellular respiration?
they are reverses of each other
how do autotrophs get energy?
they feed themselves
what are the two types of autotrophs?
- photoautotrophs
2. chemoautotrophs
how do heterotrophs get energy?
they feed on autotrophs and other heterotrophs
how did photosynthesis give rise to life?
by releasing oxygen to enable cellular respiration
how many major steps are there in photosynthesis?
2
what are the 2 major steps in photosynthesis?
light dependent and light independent
which step of photosynthesis requires light energy?
light dependent
which step of photosynthesis is also known as carbon fixation?
light independent
what is the source of carbon in the sugars produced by heterotrophs?
CO2
what is the main site of photosynthesis in a plant?
the leaf
does all photosynthesis occur in the leaf?
no, some also takes place in the stem
what do leaves do for photosynthesis?
they act as satellite dishes to collect light energy and focus it into photosynthesis
why are leaves thin?
to maximize the energy coming into the chloroplasts
what leaf structures moderate the amount of sunlight coming in?
2 epidermal surfaces, leaf hairs, and wax
what are stoma?
the little mouths that open and allow air (with CO2) into the leaf
where are stoma located?
on the underside of the leaf
lost 4 cellular structures inside leaves that do the work of photosynthesis?
- vacuoles
- chloroplasts
- vascular bundles
- thylakoids
what do vacuoles do for photosynthesis?
store water, which is needed for photosynthesis
what do chloroplasts do for photosynthesis?
convert sunlight into energy, similar to mitochondria, although plants also have their own mitochondria
what do vascular bundles do for photosynthesis?
they are the plant version of blood vessels, they transport water up from roots and bring the products of photosynthesis to various places around the cell
where are thylakoids located, and what do they do for photosynthesis?
they are located inside chloroplasts, and they house the photosystems in their membranes
what are stack of thylakoids called?
grana
what is special about chloroplasts compared to other organelles?
they have their own DNA, like mitochondria
describe the structure of a chloroplast
inner and outer membrane
inner membrane folds form sacks called thylakoids
thylakoids stack to form grana
the space around the thylakoids is called stroma
what is stroma?
the aqueous fluid in the space around the thylakoids
where does photosynthesis take place?
in the chloroplast
what is cholorphyll?
the pigment in the thylakoid membrane
who goes into photosynthesis?
sunlight, H2O, CO2, ATP
what comes out of photosynthesis?
O2, G3P (which forms glucose)
what kind of energy does the sun emit?
electromagnetic radiation
what is the photoelectric effect?
plants receive different energy levels over time because the wavelengths they receive have crests and troughs
what is a photon and how does it move?
a particle of light, like a wave
what is a wavelength?
the measurable distance between two crests
what kind of energy do short wavelengths have?
high energy
what kind of energy do long wavelengths have?
low energy
what kind of relationship exists between wavelength and energy?
inverse relationship
are gamma rays high or low energy?
high energy, we can’t survive exposure to gamma rays
what kind of energy do x-rays have?
high energy, they can penetrate tissue
what kind of energy do UV rays have?
high energy, can damage skin
is visible light a large part of the light spectrum?
no, light is only visible between 400-740nm
where does green fit in the visible light spectrum and why is that important?
it is right in the middle, so chlorophyll reflects green and absorbs all other wavelengths, above and below, for use
what wavelengths does black reflect?
none
what wavelengths does white reflect?
all wavelengths
where is chlorophyll a’s peak absorption?
420 and 680nm
where is chlorophyll b’s peak absorption?
480 and 640nm
what are the two primary pigments for photosynthesis?
chlorophyll a and b
what do the line on the absorption spectrum represent?
where pigments accept different wavelengths of energy
do all chlorophylls absorb the same wavelengths; why or why not?
no, because of this, plants have a broader energy absorption
name another pigment besides chlorophyll and describe what it does
beta ceratine, found in carrots, reflects orange wavelengths
do either chlorophyll a or b absorb green wavelengths?
no
what is the structure of chlorophyll?
porphyrin ring with magnesium at the center
hydrocarbon tail
compare and contrast hemoglobin and chlorophyll
they both have a porphyrin ring, but hemoglobin has iron at its center instead of magnesium
where are the photosystems located?
thylakoid membrane
what happens in the light dependent stage of photosynthesis?
sunlight excites chlorophyll molecules
excited electrons eject off of chlorophyll and are bounced around to primary electron acceptors to form an electron transport chain, which, through oxidation reduction reactions, forms NADPH from NADP+
chlorophyll misses the electrons it lost, so it lyses water molecules to steal their electrons, releasing 1 molecule of O2 and 2 H+ ions (H2O –> 1/2O2 + 2H+)
the released H+ ions create a CONCENTRATION GRADIENT inside thylakoid lumen, and want to get back to the thylakoid membrane
H+ ions get back to the thylakoid membrane through ATP synthase, which takes their energy and slams ADP+P to get ATP
what happens when ATP Synthase creates ATP?
potential energy is converted to kinetic energy
what happens in the light independent phase of photosynthesis?
CO2 joins onto RUBP with help from RUBISCO, making a very unstable molecule that splits into the intermediate: 3-PGA
3PGA goes through steps, using ATP and NADPH, to form G3P
ATP is used to make RUBP to start the cycle over again
what is RUBP?
ribulose bisphosphate, a substrate
what is rubisco?
the enzyme that catalyzes the first step of the calvin cycle, or light independent reactions, by attaching to the substrate RUBP
how many times does the calvin cycle need to run to make one molecule of glucose?
6 times
why does the calvin cycle need to run 6 times to make one molecule of glucose?
glucose is a 6 carbon molecule, and 1 carbon is “fixed” during each turn of the cycle
what do accessory pigments do?
contribute to more electron excitation, they help photosynthesis along
list an accessory pigment
beta ceratine
what are the 4 stages of light dependent reactions?
PCEC
- primary photoevent
- charge separation
- electron transport chain
- chemiosmosis
what happens during the first stage, or primary photoevent of light dependent reactions?
photons strike chlorophyll and excite its electrons
what happens during the second stage, or charge separation, of photosynthesis?
electrons are ejected off of cholorphyll
what happens during the third stage, or electron transport chain, of photosynthesis?
electrons are bounced around between electron acceptors
what happens during the fourth stage, or chemiosmosis, of photosynthesis?
H+ ions are pumped across the thylakoid membrane into the lumen, forming a concentration gradient, which powers ATP synthase
is any CO2 used during the light dependent stage of photosynthesis?
no
what kind of reaction occurs during charge separation in the light dependent stage?
oxidation
list the two single photosystem organisms
- purple (nonsulfur)
- green (sulfur)
bacteria
what kind of ATP and NADPH production do single photosystem organisms achieve?
limited ATP and no NADPH production
list the three linked photosystem organisms
- cyanobacteria (used to be blue green algae)
- plants
- algae
who are the organisms that have single photosystems?
primitive prokaryotes
how do single photosystem organisms perform photosynthesis?
cyclic photophosphorylation
what 2 things happen in cyclic photophosphorylation?
- hydrogen gas is released
2. electron is recycled to a different cholorphyll molecule
how is ATP made in cyclic photophosphorylation?
chemiosmosis, but not much ATP produced still
is any oxygen released during cyclic photophosphorylation?
no, it is anaerobic
how does photosynthesis occur in linked photosystems?
noncyclic photophosphorylation
where does the electron go in noncyclic photophosphorylation?
to NADPH, not back to chlorophyll like in cyclic photophosphorylation
is linked photosystem photosynthesis aerobic or anaerobic?
aerobic
where is the reaction center in photosystem I’s peak absorption?
at 700nm
where is the reaction center in photosystem II’s peak absorption?
at 680nm
why do photons strike both photosystems?
it gives the chlorophyll more chances to make ATP and NADPH
which photosystem is technically first and why?
photosystem II, because it was discovered first
in light dependent reactions, how is ATP produced?
chemiosmosis, through ATP synthase in thylakoid membrane
what 2 things do cells need to build carbohydrates?
- energy
2. reduction potential
how do cells get the energy they need to build carbohydrates?
ATP from light dependent reactions
how do cells get the reduction potential they need to build carbohydrates?
NADPH from photosystem I
where does the calvin cycle take place?
the stroma between thylakoids
what does the calvin cycle use as energy sources?
ATP and NADPH
what does the calvin cycle do?
incorporates CO2 into organic molecules
where does the CO2 for the calvin cycle come from?
diffuses in from atmosphere
what happens in stage 1 of the calvin cycle?
rubisco attaches carbon to RUBP
what happens in stage 2 of the calvin cycle?
NADPH and ATP convert 3PGA to G3P
what happens in stage 3 of the calvin cycle?
5G3P and 3ATP regenerate 3RUBP
RUBP + rubisco = ?
a 3 carbon intermediate (3PGA) that is coverted into G3P
RUBP + CO2 —–>
2(PGA), reaction is catalyzed by rubisco
how many G3P’s does it take to make 1 glucose and why?
2, G3P is a 3-carbon molecule
what are the three phases of the calvin cycle?
- carbon fixation
- reduction
- regeneration of RUBP
give the chemical equation for PHASE 1 of the calvin cycle?
RUBP + CO2 —> 2PGA
what happens during the reduction phase of the calvin cycle?
PGA is reduced to G3P
what happens during the regeneration phse of the calvin cycle?
the other molecule of G3P is used to regenerate RUBP
where do both molecules of G3P go in the calvin cycle?
1 leaves to form 1/2 of glucose, the other is used to regenerate RUBP
is glucose a direct product of the calvin cycle?
no
where are 2 G3P’s used to make 1 glucoe?
cytoplasm
where is the energy supplied from for carbon fixation?
18 ATP molecules
12 NADPH molecules
where is the loss of ATP and NADPH recovered?
cellular respiration
how are photosynthesis and cellular respiration connected in the energy cycle?
each uses the products of the other as starting substrates of their own reactions
what is photorespiration?
oxidation of RUBP by addition of O2
when does photorespiration occur?
hot, dry conditions
what happens in photorespiration?
CO2 and O2 compete for the active site on RUBP, and when oxygen wins, photosynthesis shuts down, and no glucose is produced
how does photorespiration occur?
when the plant reduces water loss by closing its stomata, which is where the CO2 gets in, and oxygen builds up
what is the normal photosynthesis pathway?
C3, used by common plants
what photosynthesis pathway is used to avoid photorespiration?
C4
what happens in the C4 pathway?
CO2 is added to a special substrate storage device, which produces a 4-carbon compound that can release CO2 later to allow photosynthesis at the plant’s choice
do plants close their stomata in the C4 pathway?
yes
how long can plants store excess carbon, and give an example of how this is used?
for about 4-6 hours until they physical limit is reached, plants can store CO2 during the hot part of the day and then open stomata at night when it’s cooler
what cell captures CO2 in the C4 pathway?
mesophyll cells
where is the 4-carbon molecule moved to in the C4 pathway?
a bundle sheath cell
where are CAM plantsfound? give two examples
deserts; cacti, bromeliads (pineapples)
when do CAM plants capture their CO2?
at night, this is when they open their stomata
what happens to the CO2 that CAM plants capture?
it is added to a substrate that produces a different 4-carbon compound that releases CO2 during the day
