ch 7
The first step of the Calvin cycle is the incorporation of ________ into ________.
-CO2... RuBP
Use the absorption spectrum graph and your knowledge of plant pigments to determine which three statements are true.
-Visible light that is not absorbed by chloroplast pigments determines what color a plant will appear to your eye. -Different pigments in plant chloroplasts absorb light of different wavelengths. -The orange and yellow colors of fall foliage are mostly due to carotenoids in the plants.
Approximately what wavelength of light is best absorbed by chlorophyll a, the pigment that participates directly in the light reactions?
435nm
Which wavelength of light is best absorbed by chlorophyll b?
455nm
How many carbon dioxide molecules must be added to RuBP to make a single molecule of glucose?
6 -Six carbon dioxide molecules are required to produce two G3P molecules, which can be combined to make one glucose molecule.
Which of the following equations represents photosynthesis?
6CO2 + 6H2O → C6H12O6 + 6O2 -Photosynthesis requires carbon dioxide and water for the production of sugar and oxygen.
Which option properly summarizes the inputs and outputs of the Calvin cycle?
ATP + NADPH + 3CO 2 → G3P
The products of the light reactions of photosynthesis are ________
ATP and NADPH
What two molecules are produced by the light reactions and used to power the Calvin cycle?
ATP and NADPH -ATP and NADPH are both products of the light reactions and are used to power the Calvin cycle.
The Calvin cycle requires ________ and ________ from the light reactions in order to operate
ATP... NADPH
What connects the two photosystems in the light reactions?
An electron transport chain -An electron transport chain connects the two photosystems in the light reactions.
The Calvin cycle makes direct use of ________ to make ________.
CO2, ATP, and NADPH... sugar
What provides the carbon atoms that are incorporated into sugar molecules in the Calvin cycle?
Carbon dioxide (CO2) -Carbon dioxide provides the carbon atoms that are incorporated into sugars in photosynthesis. This is why plants need to take in carbon dioxide
In which of the following organelles does photosynthesis take place?
Chloroplast -Chloroplasts use energy from light to transform carbon dioxide and water into sugar and oxygen.
________ is the source of the oxygen gas released by a photosystem
H2O
What provides electrons for the light reactions?
H2O Electrons are stripped from water in the light reactions of photosynthesis. This is one of the reasons plants need water.
Which of the following leaf types would be the most efficient at absorbing sunlight?
Large, broad leaves -These leaves have a large surface area and would be able to most efficiently absorb sunlight.
Which of the following is produced by the light reactions of photosynthesis and is consumed by the Calvin cycle?
NADPH -During the Calvin cycle, NADPH is used as a source of electrons.
What transports electrons from the light reactions to the Calvin cycle?
NADPH -NADPH is an electron carrier that picks up electrons in the light reactions and releases them in the Calvin cycle
After 3-PGA is phosphorylated, it receives energized electrons from _____.
NADPH -NADPH supplies the electrons that reduce the phosphorylated 3-PGA
Where does the energy for the Calvin cycle come from?
NADPH and ATP -The high-energy electrons carried by NADPH release energy that is used during the Calvin cycle, in addition to the energy carried by ATP.
The Calvin cycle is sometimes called the "dark reactions." Could it take place if a plant were grown in the dark continuously?
No, because sunlight is needed to make the ATP and NADPH that the Calvin Cycle relies on.
Can you tell from these absorption spectra whether red light is effective in driving photosynthesis?
One cannot tell from this graph, but because chlorophyll a does absorb red light, we can predict that it would be effective in driving photosynthesis.
One of the important waste products of photosynthesis is oxygen gas. Where does this oxygen gas come from?
Oxygen is released when water is broken down to extract electrons and protons for use in the light reactions.
The light reactions produce _____.
Oxygen, NADPH, ATP
Carbon fixation involves the addition of carbon dioxide to _____.
RuBP -In the Calvin cycle, carbon dioxide is added to RuBP.
Which of the following structures allows for gas exchange between the tissues of a leaf and the atmosphere?
Stomata -Stomata on the underside of the leaf control the passage of gases into and out of the leaf.
Refer to the accompanying figure. Which of the following is TRUE regarding the behavior of a chlorophyll molecule as it absorbs a photon?
The energy of a photon raises an electron to the excited state.
If only chlorophyll a were involved in the light reactions, would blue light (wavelength about 490 nm) be effective in driving photosynthesis?
The graph indicates that chlorophyll a absorbs very little blue light, so we can predict that blue light would not be effective.
If the interior of the thylakoid were not a sealed compartment ________.
The proton gradient could not be maintained
An action spectrum plots the rate of photosynthesis at various wavelengths of visible light, and it shows that blue light with a wavelength of about 490 nm is effective in driving photosynthesis. Based on this information and the absorption spectra shown at left, what role may chlorophyll b and carotenoids play in photosynthesis?
These pigments are able to absorb more wavelengths of light (and thus more energy) than chlorophyll a alone can absorb. As part of light-harvesting complexes in photosystems, they broaden the range of light that can be used in the light reactions.
You obtain the pigments called carotenoids in your diet when you eat carrots. Why do carotenoids appear yellow and orange?
They absorb blue/green light and reflect yellow and red wavelengths of light.
Plants are photosynthetic autotrophs. What does this mean?
They use light energy to drive the synthesis of organic molecules. -This is the definition of photosynthetic autotrophs.
True or false. Guard cells open during the day to allow gases to flow through the stomata.
True -During the day sunlight causes the guard cell to engorge with water which causes the cells to bow apart and open the stomata
Global climate change could be magnified by __________.
deforestation -By removing forests, trees that photosynthesize are removed. Less photosynthesis means less carbon dioxide being removed from the atmosphere, leaving more of this greenhouse gas in the atmosphere.
Incoming photons of light energy initiate photosynthesis by _____.
exciting electrons in pigment molecules within the photosystems, raising them to a higher energy level
What is the function of stomata?
gas exchange
The energy of wavelengths that appear ________ is LEAST useful to photosynthesis.
green
The light reactions of photosynthesis take place ________.
in the thylakoid membrane
The thylakoid membranes bring together the components necessary to carry out the _____.
light reactions
The overall function of the Calvin cycle is __________.
making sugar -The Calvin cycle makes sugar by using ATP and NADPH made during the light reactions
Which of the following is produced during the light reactions of photosynthesis?
o2
CAM plants conserve water by ________.
opening their stomata only at night
Which of the following is an autotroph?
pine tree
When light strikes chlorophyll molecules, they lose electrons, which are ultimately replaced by other electrons obtained by __________.
splitting water -The electrons removed from water are transferred to the water-splitting photosystem.
The ultimate energy source that supports most life on Earth is __________.
sunlight -Life on Earth is solar powered. Plants are photoautotrophs, organisms that use light as a source of energy to synthesize carbohydrates, lipids, proteins, and other organic substances.
The color that we see when looking at a pigmented object is ________.
the wavelengths that are reflected or transmitted by the pigmented object
Where are photosystems located?
thylakoid membrane
The light reactions take place in the _________ and the Calvin cycle takes place in the _________.
thylakoids; stroma -Within the chloroplast, the light reactions take place in the flattened sacs called thylakoids and the Calvin cycle takes place in the thick fluid called the stroma.
Which of the following BEST describes the direct mechanism of ATP production during photosynthesis?
use of the energy stored in hydrogen ion (H+) gradients; the potential energy of the proton gradient is released as the protons move down their gradient through special membrane protein channels; this energy is converted to chemical bond energy in the ATP molecule
Imagine a plant with carotenoids but no chlorophyll. Which color(s) of light would be most beneficial to the plant?
violet-blue -Caretenoids absorb light at wavelengths around 400-500 nm, which is violet and blue. Energy absorbed by these pigments drive photosynthesis, so violet-blue light would be most useful to this plant.
