Mastering Biology Chapter 7
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.
Drag the labels onto the equation to identify the inputs and outputs of photosynthesis.
INPUTS--- 6 CO2 (source of carbon and oxygen) +6 H20 (source of electron and hydrogen) +light (energy that drives photosynthesis) --> OUTPUTS-- glucose (sugar) + 6 O2 (gas produced from splitting water)
Which of the following are photoautotrophs?
corn stalks just before harvest--- Corn plants are photoautotrophs. They produce organic molecules from inorganic molecules using the energy of light.
What connects the two photosystems in the light reactions?
An electron transport chain
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
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 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.
Which statement regarding the light reactions is true?
Electrons are supplied to chlorophyll P680 as it reduces the primary electron acceptor.---- As the excited electrons of chlorophyll P680 are donated to the primary electron acceptor, they are replaced by the splitting of water.
What is the potential benefit of photorespiration in plants?
It allows plant cells to reduce the buildup of oxygen gas without opening stomata.--- Under warm, dry conditions stomata close to conserve water and prevent dehydration. Oxygen levels increase, and carbon dioxide levels decrease. Rubisco adds oxygen instead of carbon dioxide to RuBP, and the product is eventually broken down into carbon dioxide and water.
Oxygen is the final electron acceptor for cellular respiration. What is the final electron acceptor in the light reactions of photosynthesis?
NADP+----- NADP+ is the final electron acceptor in the light reactions of photosynthesis. The product is NADPH.
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.
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.
Incoming photons of light energy initiate photosynthesis by _____.
exciting electrons in pigment molecules within the photosystems, raising them to a higher energy level
The thylakoid membranes bring together the components necessary to carry out the _____.
light reactions
The light reactions produce _____.
oxygen, NADPH, and ATP
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.