7.1-7.9 Flashcards
Complete the sentence: “Life on earth is _____ powered.”
solar
How far away is the sun from earth?
150 million kilometers
What are the reactants (a) and the products (b) of photosynthesis?
(a) CO2 and H2O (b) O2, sugars, and other organic molecules
Organisms that perform photosynthesis are called what? What are the two types of these organisms?
Autotrophs. Photoautotrophs use light from the sun for energy. Chemoautotrophs use inorganic chemicals from hydrothermal vents for energy.
Organisms that feed off of autotrophs are called…
Consumers/heterotrophs
What do “autotroph” and “heterotroph” mean, and what language to they derive from?
self-feeder and other-feeder, respectively. Greek.
Besides supplying the primary level of all the world’s food, what else are autotrophs used for.
Clothing (cotton), housing (wood), warmth, light, transport, and manufacturing.
Where do fossil fuels come from?
The decomposition and pressurizing of energy-rich autotrophs from 300 million years ago.
Where, and in what form, are photoautotrophs found?
The answer to this would probably be infinite. The ones mentioned in the book include terrestrial vegetation, singular and multicellular algae, and cyanobacteria (freshwater and marine ecosystems).
What is endosymbiosis?
The theory that mitochondria and chloroplasts began as prokaryotes that were engulfed into larger cells that became eukaryotes.
How do photosynthetic bacteria work?
Infolded regions of their plasma membrane with photosynthetic pigments and enzymes.
How do you know a part of a plant has chloroplasts?
If it is green
Where is the major site of photosynthesis in plants?
Leaves
In one mm^2 of leaf, how many chloroplasts are there?
0.5 million.
Where does the green color in leaves come from?
Chlorophyll
What is chlorophyll?
A light-absorbing pigment that contributes in to the conversion of solar energy to chemical energy.
Where in a leaf cell are chloroplasts concentrated?
The green tissue of the interior of the leaves, or the mesophyll.
How does CO2 enter and O2 exit through a leaf?
Holes called stomata (sing. stoma)
How is water received by the plant?
Through the roots, to the veins of the leaves.
How many chloroplasts does a mesophyll cell have?
30-40.
Describe the structure of a chloroplast.
Two membranes. Inner one is filled with a fluid called stroma. In it there are stacks called grana (sing. granum) which are made up of circles called thylakoids.
What is the chloroplast equivalent of the mitochondrial matrix?
The thylakoid membrane/sac.
End of 7.2 question: how do the reactant molecules of photosynthesis reach the chloroplasts in leaves?
CO2 enters through stomata, H2O enters the roots and is carried to leaves through veins.
End of 7.1 question: What do “self-feeding” autotrophs require from the environment to make their own food?
Light, carbon dioxide, and water. (Minerals are also required)
What is the basic equation for photosynthesis?
6CO2 + 6H2O = C6H12O6 + 6O2
What did C. B. van Niel hypothesize about photosynthesis, and why?
Photosynthetic bacteria he was studying produced sugar from CO2, but did not release O2. This convinced him that the oxygen in carbon dioxide was not transferred to the oxygen molecule at the end of photosynthesis, the generally accepted theory.
How was Van Niel’s hypothesis confirmed?
A study using the isotope O-18 in the 1950s. The oxygen in carbon dioxide appeared both in the sugar and the product water produced by photosynthesis. The oxygen in the reactant water appeared in only the product oxygen molecules.
What does the Calvin cycle describe?
It details the intermediates on the cyclic pathway that takes CO2 and makes sugar.
End of 7.3 question: Photosynthesis produces billions of tons of carbohydrates a year. Where does most of the mass of this huge amount of organic matter come from?
Mostly from CO2 in the air, which provides both carbon and oxygen in carbohydrates. Water only supplies the hydrogens.
Photosynthesis, like cellular respiration is a ____ reaction.
Redox
How do redox reactions occur within photosynthesis?
CO2 becomes reduced and forms sugar. Water is oxidized and becomes oxygen (it literally loses its hydrogens). This is the inverse of cellular respiration.
What separates the redox reactions of photosynthesis from that of cellular respiration?
Photosynthesis needs energy. The potential energy of electrons within CO2 and water increases as photosynthesis goes along due to photons.
How is the energy captured for photosynthesis?
Chlorophyll.
What is energy being converted into in photosynthesis?
Light energy to chemical energy.
End of chapter 7.4: Which redox process, photosynthesis or cellular respiration, is endergonic?
Photosynthesis.
What are the two cycles in photosynthesis?
Light reactions and Calvin cycle.
What is the first cycle in photosynthesis?
Light reactions
What do light reactions do? Describe a bit of the process.
Convert light energy into chemical energy in the form of NADPH and ATP and release O2. Water is split into O2 and hydrogens. Chlorophyll in thylakoids are energized by light energy and bond H+ molecules from water to the electron acceptor NADP+.
What is the reduced version of NADP+?
NADPH
What separates NADP+ from NAD+
NADP+ has an extra phosphate group.
What is NADPH’s purpose?
To provide “Reducing power” to Calvin cycle.
What energy molecule can the light reactions produce?
ATP.
Give a brief overview of the Calvin Cycle
assemble sugar molecules using CO2 and high energy products from light reactions.
What is carbon fixation? What is the carbon fixed to in photosynthesis?
The incorporation of CO2 into organic compounds. Sugars.
How are sugars reduced in the Calvin cycle?
Through NADPH.
How is the Calvin cycle given energy for some steps?
From ATP from light reactions.
Does the Calvin cycle require light?
no, not directly. However, it more often than not occurs in the day time due to its reliance on the products of light-dependent reactions products.
End of 7.5: For chloroplasts to produce sugar from carbon dioxide in dark, they would need to be supplied with _______ and ________.
ATP and NADPH.
In what form is sunlight’s energy in?
Electromagnetic; radiation
In an electromagnetic wave, what is a wavelength?
The distance between two crests
What is the electromagnetic spectrum?
The full range of electromagnetic wavelengths, from gamma rays to radio waves.
What is the space on the electromagnetic spectrum with visible light?
A very small fraction, between 380 nanometers and 750 nanometers. The lowest end of the spectrum is purple, the highest red.
What is a photon?
A discrete packet of fixed electromagnetic energy. The shorter the wavelength, the higher the energy.
When photons have electromagnetic waves that are shorter than visible light, what happens?
They can damage molecules, such as proteins and nucleic acids. An example is ultraviolet light.
What is a pigment, in biological terms?
A light absorbing molecule (it can also reflect and transmit light).
Why are leaves green?
In the spectrum of visible light, green is reflected by leaves. We can not see the light they absorb, only the light they reflect.
What are the benefits of a leaf having two types of chlorophyll (a and b)?
It can absorb a greater spectrum of light.
What wavelengths are absorbed by chlorophyll a? chlorophyll b?
Blue-violet and red. Blue orange. They reflect blue-green and olive green, respectively.
What other pigments do chloroplasts have? What color are they?
They have carotenoids, which are shades yellow and orange (foliage).
What are the benefits carotenoids in the chloroplast?
They broaden the spectrum of light used for photosynthesis. Their more important function is photoprotection: they absorb and dissipate excessive light energy.
What does excessive light energy do to the chloroplast?
Damages chlorophyll, interact with oxygen to form oxidative molecules that would damage the cell.
Where does the idea that carrots are good for eyesight come from?
Carrots have carotenoids in them, making their orange color. When eaten, they give photoprotective qualities to our eyes.
Why do pigments absorb specific wavelengths of light?
It can absorb the specific amount of energy in the photons.
end of 7.6 question: What color of light is least effective at driving photosynthesis? Why?
Green, because it is mostly transmitted and reflected, but not absorbed, by photosynthetic pigments.
What happens when a pigment absorbs light energy?
Some of the electrons within the molecule “jump” to a high-energy state. This is also known as jumping from ground state to an excited state.
Are excited electrons stable? How long (usually) are electrons in this state?
No. 1 billionth of a second. When it goes back to ground state, it releases energy as heat. Black pigments absorb all wavelengths of light, which is why they tend to heat up faster.
What is fluorescence?
The process in which photons, as well as heat, are released by pigments when their electrons go back to a ground state. This process can be seen if chlorophyll is isolated.
Why, when chlorophyll is in a chloroplast, does it not behave the same way as it does in isolation?
The excited electrons are passed between transfer electrons to other pigment molecules and eventually a special pair of chlorophyll molecules, which pass it off to a neighboring molecule which keeps it in its high energy state. All of this occurs in thylakoid membrane
Describe the photosystem within chloroplasts.
Has two parts: a reaction center surrounded by light-harvesting complexes. The complexes consist of pigments bonded to proteins. They absorb photons and pass them until they reach a special pair of chlorophyll a molecules, which is attached to a primary electron acceptor (it can be reduced, keeps the electron in its high-energy state).
How many types of photosystem are there. In what do they differ?
2 (Photosystem I and Photosystem II). Photosystem II works first in light-dependent reactions.
End of 7.7 question: Compared with a solution of isolated chlorophyll, why do intact chloroplasts release less heat and fluorescence when illuminated?
In the chloroplast, a light-excited electron from the reaction-center chlorophyll is trapped by a primary electron acceptor rather than giving up its energy as heat and light.
Where are photosystems located?
The inner (thylakoid) membrane of a chloroplast.
Describe the energy coupling of photosystems II and I.
Photosystem II receives the initial photon-initiated excited electrons, where they are quickly accepted by the primary electron acceptor. The electrons are transported to Photosystem I. The energy lost between the two photosystems is used for the synthesis of ATP. Upon reaching photosystem I, another photon jumps the energy level to a even higher level than before, where it reduces NADP+ to NADPH.
Where do the electrons that reduce NADP+ to NADPH come from in photosynthesis? How are the electrons isolated?
From the reactant water. An enzyme in the thylakoid space splits H2O into 2 electrons, 2 protons and 1/2O2. The H+ stays in the thylakoid space. The 1/2O2 molecule forms O2 (as we learned that H2O is where oxygen comes from). The O2 diffuses out of the stomata. The electrons go through the photosystems. A small electron transport chain.
How is ATP produced in photosynthesis?
Chemiosmosis. The exact same process as cellular respiration, except within a chloroplast. This is also known as photophosphorylation.
End of 7.8 question: why are two photons of light required in the movement of electrons from water to NADPH?
One photon excites an electron from Photosystem II, which is then passed down an electron transfer chain to photosystem I. A second photon excites an electron from photosystem I, which is then used in the reduction of NADP+ to NADPH.
Where is their a high concentration of H+ ions in photosynthesis? Where do these ions come from?
The thylakoid sac. Electron transport chain. H+ are both from water and those pumped by the chain.
Where do the NADPH and ATP produced by light-dependent reactions go?
To the Calvin cycle.
How are the processes of ATP synthesis in cellular respiration and photosynthesis opposite?
Where H+ gradient is located.
End of 7.9 question: What is the advantage of the light reactions producing NADPH and ATP on the stroma side of the thylakoid membrane?
The Calvin Cycle, which uses NADPH and ATP, occurs in the stroma.
