Biology Quiz Ch.10 (Exam 4)

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Photosynthesis

Which of the following products of the light reactions of photosynthesis is consumed during the Calvin cycle?

NADPH
-During the Calvin cycle electrons stored in NADPH are used to reduce carbon.

The overall function of the Calvin cycle is _____.

Making Sugar
-Using the ATP and NADPH made during the light reactions, carbon is reduced in the Calvin cycle and sugar is made.

Photosynthesis (def)

The conversion of light energy to chemical energy that is stored in glucose or other organic compounds; occurs in plants, algae, and certain prokaryotes.

Chemical energy

Energy stored in the chemical bonds of molecules; a form of potential energy.

Oxidation

The loss of electrons from a substance involved in a redox reaction.

Reduction

The addition of electrons to a substance involved in a redox reaction.

Chloraplasts

An organelle found only in plants and photosynthetic protists that absorbs sunlight and uses it to drive the synthesis of organic compounds from carbon dioxide and water.

Light reactions

The steps in photosynthesis that occur on the thylakoid membranes of the chloroplast and that convert solar energy to the chemical energy of ATP and NADPH, evolving oxygen in the process.

Thylakoid

A flattened membrane sac inside the chloroplast, used to convert light energy to chemical energy.

Calvin Cycle

The second of two major stages in photosynthesis (following the light reactions), involving atmospheric CO₂ fixation and reduction of the fixed carbon into carbohydrate.

Stroma

The fluid of the chloroplast surrounding the thylakoid membrane; involved in the synthesis of organic molecules from carbon dioxide and water.

Chlorophyll

A green pigment located within the chloroplasts of plants. Chlorophyll a can participate directly in the light reactions, which convert solar energy to chemical energy.

ATP (Adenosine triphosphate)

An adenine-containing nucleoside triphosphate that releases free energy when its phosphate bond are hydrolyzed. This energy is used to drive endergonic reactions in cells.

Which of these equations best summarizes photosynthesis?

6 CO2 + 6 H2O → C6H12O6 + 6 O2

Where does the Calvin cycle occur?

The Calvin cycle occurs in the stroma.

The light reactions of photosynthesis use _____ and produce _____.

water; NADPH
-NADPH is a reactant in the Calvin cycle.

Generation of proton gradients across membranes occurs during

Both PHOTOSYNTHESIS and RESPIRATION.

CAM plants keep stomata closed in daytime, thus reducing loss of water. They can do this because they

fix CO₂ into organic acids during the night.

Photosynthesis is a redox reaction. This means that H2O is _____ during the light reactions and CO2 is _____ during the Calvin cycle.

Oxidized; Reduced
-During the light reactions of photosynthesis, water is oxidized, and during the Calvin cycle, carbon is reduced.

Where do the enzymatic reactions of the Calvin cycle take place?

Stroma of the chloroplast

In C3 photosynthesis, the reactions that require ATP take place in

the Calvin cycle alone

Which of the following are products of the light reactions of photosynthesis that are utilized in the Calvin cycle?

ATP and NADPH

In a plant cell, where are the ATP synthase complexes located?

Thylakoid membrane and inner mitochondrial membrane

In mitochondria, chemiosmosis translocates protons from the matrix into the intermembrane space, whereas in chloroplasts, chemiosmosis translocates protons from

the stroma to the thylakoid space.

Why are C4 plants able to photosynthesize with no apparent photorespiration?

They use PEP carboxylase to initially fix CO₂

When light strikes chlorophyll molecules, they lose electrons, which are ultimately replaced by _____.

splitting water;
-The electrons removed from water are transferred to P680.

Which of the following is a product of the light reactions of photosynthesis?

Oxygen, ATP, and NADPH

Approximately what wavelength of light is best absorbed by chlorophyll a, the pigment that participates directly in the light reactions?

435 nm

Which wavelength of light is best absorbed by chlorophyll b?

455 nm

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.

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.

Which process produces oxygen?

Photosynthesis
-Oxygen is a by-product of the photosynthesis process.

Which set of reactions uses H₂O and produced O₂

The light-dependent reactions.

Photosynthesis

A series of chemical reactions and electron transfers that covert the energy of light into the chemical energy stored in glucose.

Cellular Respiration

A common and efficient pathway to produce ATP, which involves a transfer of electrons from a reduced compound to an electron transport chain, and ultimately to an electron acceptor.

In photosynthesis

plants use carbon dioxide, water, and light energy to produce sugar and other complex molecules. Oxygen is released as a by-product.

The complementary process of cellular respiration

coverts oxygen and sugar into carbon dioxide and water. In the process some energy is released to make ATP, and the rest is lost as heat.

ATP

Adenosine triphosphate, a molecule consisting of adenine, a sugar, and three phosphate groups that can be hydrolyxed to release free energy. Universally used by cells to store and transfer energy.

Calvin Cycle (occurs in the Stroma)

The light-independent component of photosynthesis, in which carbon dioxide is reduced to form sugars. The carbohydrates produced by the Calvin cycle are used in cellular respiration to make ATP for the cell.

Two set of reaction of Photosynthesis?

1.) Light dependent reaction: transform the energy in sunlight to chemical energy in the form of electrons with high potential energy. These reactions result in the production of OXYGEN from water.
2.) Light independent reaction: uses ATP and NADPH to reduce carbon dioxide from the atmosphere to sugar, through a set of reactions called CALVIN CYCLE.

Light-Dependent Reactions

-The light dependent reactions of photosynthesis occur within the thylakoid membranes inside the chloroplast.
-Light dependent reaction have two photosystems. In photosystem 1, excited electrons are used to produce NADPH. In photosystem 2 they are used to produce ATP.

thylakoid

A flattened, membrane-bound disk inside a plant chloroplast. A stack of thylakoids is called a granum.

Chloroplast

A chlorphyll-containing organelle in plant cells, in which photosynthesis occurs.

Chlorophyll

A green pigment molecule found in plant cells that absorbs light energy to power photosynthesis.

photosystem

A complex of molecules and enzymes in plant chloroplasts that takes part in photosynthesis.
1. photosystem 1 (NADPH)
2. photosystem 2 (ATP)

Plastoquinone

A small, hydrophobic molecule that carries electrons across the thylakoid membrane during photosynthesis.

Plastocyanin

A small protein that shuttles electrons from photosystem 2 to photosystem 1 during photosynthesis.

Pheophytin

A molecule, very similar to chlorophyll, that acts as an electron acceptor in photosynthesis.

Calvin cycle (3 phases)

1. The fixation phase
2. The reduction phase
3. The regeneration phase

-Can occur with or without light and occurs in the stroma.

The Fixation Phase (CC)

In the fixation phase, carbon dioxide from the atmosphere combines with a 5-carbon molecule called ribulose-bis-phosphate, or RuBP. This process, in which carbon dioxide is made usable to life by incorporating it into an organic molecule called carbon fixation. The product of the initial reaction is an unstable 6-carbon compound that splits to yield two 3 carbon molecules of 3 phosphoglycerate.

Carbon Fixation

The part of the Calvin Cycle in which carbon atoms are extracted from atmospheric carbon dioxide and used to make simple organic compounds that eventually become glucose.

The Reduction Phase (CC)

The reduction phase begins when 3 phosphoglycerate is phosphorylated by ATP and concludes when it has been reduced by electrons from NAPDH. The product of the phosphorylated sugar glyceraldehyde 3 phosphate (G3P). Two G3P molecules are used to manufacture glucose.

The Regeneration Phase (CC)

If the Calvin Cycle did not go through a regeneration phase, the chloroplast would run out of the RuBP molecules required to make glucose. To make a single molecule of glucose and to regenerate RuBP, the cycle must run SIX times.

Which process produces oxygen?

Photosynthesis
-Oxygen is a by-product of the photosynthetic process

Which set of reactions uses H2O and produces O2?

The light dependent reactions.

What is the importance of the light-independent reactions in terms of carbon flow in the biosphere?

The light-independent reactions turns CO₂, a gas, into a usable carbon in the form of sugars.
-CO₂ is unusable until plants have "fixed" this carbon into sugar.

True or false? The light-dependent reactions of photosynthesis use water and produce oxygen.

True
-The water molecules are split to replenish electrons in photosystem 2, leaving behind protons, which are used to generate a proton gradient for the formation of ATP, and oxygen, which is released as a by product.

Which of the following molecules is the primary product of photosystem I?

NADPH
-The NADPH produced by photosystem 1 is used to supply energy for the production of sugars during photosynthesis.

What is the biological significance of the light-independent reactions of photosynthesis?

They convert carbon dioxide to sugar.
-All organisms use the sugars produced by photosynthesis to generate energy.

Which of the following statements best describes the relationship between the light-dependent and light-independent reactions of photosynthesis?

The light dependent reactions produce ATP and NADPH, which are then used by the light independent reactions.

Which of the following reactions ensures that the Calvin cycle can make a continuous supply of glucose?

Regeneration of RuBP
-the regeneration of RuBP ensures that the Calvin Cycle can proceed indefinitely, since RuBP fixes carbon dioxide into an organic molecule that is used to produce sugar.

Where does the Calvin cycle take place?

Stroma of the chloroplast

The photosynthetic membranes are found in the _____ in plant cells.

chloroplasts
- An elaborate system of interconnected thylakoid membranes segregates the stroma from the thylakoid space in the chloroplast.

The reactions that produce molecular oxygen (O2) take place in

The light reactions alone.

The NADPH required for the Calvin cycle comes from

reactions initiated in photosystem 1

C4 plants occur more commonly in desert conditions because _____.

they can fix carbon at the lower CO₂ concentrations that develop when the stomata are closed.
-To conserve water during hot, dry conditions, the stomata are fully or partially closed, preventing CO₂ from reaching high concentrations.

In the electromagnetic spectrum, the type of radiation that we call visible light occurs between _____.

ultraviolet radiation and infrared radiation
-Visible light is a narrow band of the electromagnetic spectrum that lies between ultraviolet radiation and infrared radiation.

In photosynthetic cells, synthesis of ATP by the chemiosmotic mechanism occurs during

Both photosynthesis and respiration

Radiation

The emission of electromagnetic waves by all objects warmer than absolute zero

wavelength

The distance between crests of waves, such as those of the electromagnetic spectrum.

Elecromagnetic spectrum

The entire spectrum of radiation ranging in wavelength from less that a nanometer to more than a kilometer.

_____ has a longer wavelength than _____.

Red has a longer wavelength than Green

What does the chemiosmotic process in chloroplasts involve?

establishment of a proton gradient across the thylakoid membrane.

Where are the molecules of the electron transport chain found in plant cells?

thylakoid membranes of chloroplast

Which of these phosphorylates ADP to make ATP?

ATP synthase phosphorylates ADP.

_____ releases energy that is used to pump hydrogen ions from the stroma into the thylakoid compartment

Electron transport chain
-The energy released as electrons are passed along the electron transport chain is used to pump protons into the thylakoid compartment.

_____ splits water into 1/2 O2, H+, and e-

Photosystem 2

Energized electrons from ____ enter an electron transport chain and are then used to reduce NADP+.

Energized electrons from photosystem I are used to reduce NADP+

Chlorophyll can be found in _____.

The photosystems contain chlorophyll.

What is the primary function of the Calvin cycle?

Synthesize simple sugars from carbon dioxide.

mesophyll cell

A loosely arranged photosynthetic cell located between the bundle sheath and the leaf surface.

Reactions that require CO2 take place in

the Calvin cycle alone.

When oxygen is released as a result of photosynthesis, it is a direct by-product of

splitting of water molecules

Which of the events listed below occurs in the light reactions of photosynthesis?

Light is absorbed and funneled to reaction-center chlorophy 2 a.

The splitting of carbon dioxide to form oxygen gas and carbon compounds occurs during

neither photosynthesis nor respiration.

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