Bio-110 Chapter 7

In photosynthesis, plants use carbon from _____ to make sugar and other organic molecules.

carbon dioxide Less than 1% of the atmosphere is CO2, but it is enough to support photosynthesis.

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.

If a home uses a large supply of solar panels to generate electricity, but has no battery system, surplus electricity that is produced is usually __________.

released into the power grid for others to use, generating a credit to the homeowner This surplus energy therefore generates value to the homeowner whenever more electricity is produced than is needed. This helps to further offset the cost of the solar panel system.

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 + 3CO2 → G3P

Incoming photons of light energy initiate photosynthesis by _____.

exciting electrons in pigment molecules within the photosystems, raising them to a higher energy level

The light reactions produce _____.

oxygen, NADPH, and ATP

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 produced in the light reactions 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.

Which of the following provides a source of energy for the Calvin Cycle?

NADPH The high-energy electrons carried by NADPH release energy that is used during the Calvin cycle, in addition to the energy carried by ATP.

Photosynthetic membranes are found in __________.

chloroplasts An elaborate system of interconnected thylakoid membranes segregates the stroma from the thylakoid space in the chloroplast. This is where photosynthesis takes place.

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.

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.

Phenol red is a chemical that turns red when carbon dioxide, CO2, is absent and yellow when CO2 is present. A small green plant seedling is placed in phenol red in the dark. Which one of the following is most likely to occur?

If the solution is red to begin with, it will turn yellow because respiration is occurring. Plants will not conduct photosynthesis in the dark, but they will continue with cellular respiration, releasing carbon dioxide, which should turn the chemical yellow.

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.

Which of the following best describes the energy conversion sequence in the solar panel system described in the video?

Photons carrying energy from the sun chemically react with silicon crystals to generate a flow of electrons. The energy of the sun has to be converted into electricity.

The end products of photosynthesis are __________ and __________.

glucose ... molecular oxygen Glucose and O 2 are used by plants and can also support consumers that eat plants.

Which one of the following colors is most strongly reflected by chlorophyll?

green Chlorophyll reflects green light, which is why leaves appear green.

Which of these wavelengths is least useful for photosynthesis?

green Most plants reflect green. If it were absorbed, plants would be colored something other than green.

The thylakoid membranes bring together the components necessary to carry out the _____.

light reactions

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.

Which of the following is a challenge to using solar-generated electricity in places not connected to a power grid?

the lack of efficient and inexpensive battery technology Current research in battery technology hopes to address this important need, which may also benefit the electric car industry.

The "photo-" part of the word "photosynthesis" refers to __________, whereas "-synthesis" refers to __________.

the light reactions that occur in the thylakoids ... the incorporation of carbon dioxide Events in the thylakoids are termed the "light reactions," whereas the incorporation of carbon into organic molecules is the province of the Calvin cycle.

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.

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.

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 the solar panel system presented in the video, which of the following was necessary to generate usable electrical current for a home?

DC power had to be converted to AC. The solar panel generates DC current, which is not usually used in homes. Thus, the DC current must be converted to AC, which is the standard in homes.

Which of the following would indicate that a home is using solar power to generate electricity and is NOT using batteries?

There are solar panels on the roof and power lines going to the home. When the solar panel system is not generating enough electricity, or any at all at night, the home can draw upon the power grid. Therefore, the home does not require or use batteries for backup.

The Calvin cycle is a series of reactions that __________.

assemble sugar molecules by incorporating carbon

The most important role of pigments in photosynthesis is to __________.

capture light energy The wavelengths most effectively absorbed by pigments are the colors most useful as energy for the light reactions.

When chloroplast pigments absorb light, __________.

their electrons become excited The absorbed energy moves the electrons to a more energetic orbital.

How does carbon dioxide enter the leaf?

through the stomata These are the openings for gas exchange in the leaf.

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.