Chapter 11 - Photosynthesis Flashcards
how does energy enter plants
the energy in light is absorbed by chlorophyll and transferred into chemical energy during photosynthesis
where does photosynthesis take place
chloroplasts
how are leaves adapted for photosynthesis 8
- a large surface area to absorb sunlight
- an arrangement that prevents overlapping and so shadowing of other leaves
- thin for a short diffusion pathway
- transparent cuticle to let light through to the palisade mesophyll cells
- upper mesophyll cells full of chloroplasts
- numerous stomata so mesophyll cells are never far from one
- xylem bringing water to leaf cells and phloem bringing food to the roots
- air spaces in the spongy mesophyll for a large surface area
what is the overall equation for photosynthesis
6CO2 + 6H20 -light-> C6H1206 + 6O2
what are the three main stages of photosynthesis
capturing light energy
the light dependent reaction
the light independent reaction
what happens in the first stage of photosynthesis
light energy is captured in the chlorophyll of the chloroplasts to make ATP and photolysis water
what happens in the second stage of photosynthesis
light breaks the bonds in chlorophyll causing water molecules to split by photolysis into protons, electrons and oxygen
what are the products of the light-dependent reaction
reduced NADP, ATP and oxygen
what happens in the third stage of photosynthesis
protons are used to produce sugars and other organic molecules
how long are chloroplasts typically
2-10 micrometres
what type of membrane can be found in chloroplasts
a double membrane
what are the two distinct regions in a chloroplasts
the grand and storm
what is the stroma
a fluid filled matrix containing starch grains. also where the light independent stage takes place
what are the grana
stacks of up to 100 thylakoid structures which contain chlorophyll. also where the light-dependent stage takes place
what happens when a substance is oxidised
gains oxygen, loses hydrogen or electrons
what happens when a substance is reduced
loses oxygen, gains hydrogen or electrons
what is the metabolic pathway
a series of small reactions caused by enzymes
east is phosphorylation
adding phosphate to a molecule
what is photophosorylation
adding phosphate to a molecule using light
what is photolysis
using light energy to split apart a molecule
what is photoionisation
when light energy excited electrons, causing them to be released and move to a higher energy level
what is hydrolysis
the splitting of a molecule using water
what is decarboxylation
the removal of carbon dioxide form a molecule
what is dehydrogenation
the removal of hydrogen from a molecule
what does NADP do
NADP is a coenzyme- it transfers hydrogen from one molecule to another
at what wavelength does Pi best absorb light
700 nm
at what wavelength does Vii best absorb light
680 nm
what happens in the light-dependent reaction
a chlorophyll molecule absorbs light energy, which excites the electrons in the chlorophyll and raises them to a higher energy level so they leave the chlorophyll. the chlorophyll had been photoionised. the electrons are taken up by an electron carrier molecule and passed along a chain of carriers via a series of redox reaction. because each new carrier is at a slightly lower energy level, the electrons lose a bit of energy each time. the energy is used to combine a phosphate molecules with ADP to produce ATP
describe chemiosmotic theory
protons are pumped into the thylakoid membranes using protein carriers called protein pump. the energy produced when water is photolysis is what fuels this movement, this creates a higher concentration of protons inside the thylakoid than in the stroma. protons move down the concentration gradient into the stroma via the carrier protein ATP synthase. as they move through the protein, they change the shape of the enzyme which catalyses the combination of ADP and Pi
what is the equation for the photolysis of water
2H20 -> 4H+ + 4e- + O2
what happens to the protons produced when water is photolysis
they pass out of the thylakoid via ATP synthase proteins, where they combine with electron carrier NADP reducing it. this NADP enters the light-independent stage taking with it the electrons created from the chlorophyll molecules
where does the light-dependent reaction takes place
the thylakoid of chloroplasts
how are chloroplasts adapted for the light-dependent reaction
the thylakoid membranes proved a large surface area. proteins hold the chlorophyll in a precise manner that allows maximum absorption of light. chloroplasts contain DNA and ribosomes so can quickly produce proteins required. the membranes have ATP synthase within them, which catalyses the formation of ATP
what is another name for the light-independent reaction
the Calvin cycle
where does the light-independent reaction take place
the stroma of the chloroplasts
what happens in the light-independent reaction
co2 diffuses into the leaf through the stomata and then into the stroma. here the co2 combines with RuBP in a reaction catalysed by rubisco. this forms an unstable 6 carbon compound which quickly breaks down into two molecules of GP. the hydrolysis of ATP provides energy and reduced NADP provides H+ ions to turn this GP into TP. the NADP goes back to the light-dependent reaction to accept more protons. some TP is turned into glucose and the rest continues to regenerate RuBP
how many carbons are there in RuBP
5
how many carbons are there in GP
3
how many times does the Calvin Cycle need to occur to produce one hexose sugar
6
how are the chloroplasts adapted for the light-independent reaction
the matrix of the stroma contains all necessary enzymes. the stromal fluid surrounds the grana so products of the light-dependent reaction in the grana can diffuse into the stroma. contains DNA and ribosomes so can easily make necessary proteins
what are the optimum conditions for photosynthesis
high light intensity.
temperature at 25c.
carbon dioxide at 0.4%
why is a high light intensity required for photosynthesis
it provides the energy for the light-independent reaction
why is a temperature at 25c required for photosynthesis
it is the optimum temperatures for enzymes like rubisco
what is the saturation point
where the rate of respiration = rate of photosynthesis so there is no net movement of gas in the plant
