Chapter 8 - Photosynthesis - EXAM #4

Light reactions inputs:

Sunlight Water

Where does the Calvin cycle occur?

Takes place in the stroma and does not directly require light

A synonym for the light-independent reactions of photosynthesis is?

The Calvin cycle

What 2 molecules do the light-dependent reactions give to the next stage of photosynthesis?

The energy storage molecule ATP and the reduced electron carrier NADPH.

CAM plants description

-Adapted to very dry climates -Conserve water by opening stomata and allowing CO2 to come in only at night -CO2 is incorporated into a four-carbon compound that stores it at night and releases it during the day -This process keeps photosynthesis operating when the stomata are closed during the day -Pineapples, many cacti, and water-storing plants such as aloe and jade

C4 plants description

-Called C4 plants because they incorporate carbon from CO2 into a four-carbon compound before proceeding to the Calvin cycle -In hot and dry weather, keep stomata mostly closed, conserving water -Have an enzyme that continues to incorporate carbon even when CO2 concentration is low, resulting in a four-carbon compound that acts as a carbon shuttle. It donates CO2 to the Calvin cycle in a nearby cell, which keeps on making sugars when the stomata are closed -Corn, sugarcane

Calvin Cycle steps:

-Carbon fixation - 3 molecules of CO2 attached to 3 molecules of ribulose bisphosphate (RuBP) producing 3-phosphoglycerate (3-PGA); the product splits into 2 3-carbon molecules -Reduction - ATP and NADPH are used to reduce the 3-carbon molecule to G3P -Release of 1 molecule of G3P - 1 molecule of G3P leaves the cycle to make glucose and other compounds -Regeneration of RuBP - remaining 5 G3P molecules are rearranged to regenerate 3 molecules of RuBP

Photosystems:

-Consist of a number of light-harvesting complexes surrounding a reaction-center complex -The reaction-center contains a pair of chlorophyll a molecules and a molecule called the primary electron acceptor

There are two types of photosystems, explain both:

-Photosystem II: makes ATP (electron transport protein and chemiosmosis) -Photosystem II replaces lost electrons by splitting water - O2 is giving off -Photosystem I: transfers electrons to produce NADPH (short electron transport chain) -Photosystem I's electrons are replenished Photosystem II Both are connected by an electron transport chain

C3 plants description

-Plants that use CO2 directly from the air to drive the Calvin cycle -Performs normal photosynthesis -Called C3 plants because the first organic compound produced in the Calvin cycle is a three- carbon molecule -They close their stomata on hot, dry days to help prevent dehydration reducing water loss. This also prevents CO2 from entering the leaves and as a result, CO2 gets very low in the leaves and O2 builds up in the leaves, and sugar production ceases. O2 is added to RuBP instead of CO2. A 2-carbon product is broken down in the cell instead of a 3-carbon product and CO2 is released - called photorespiration -Soybeans, oats, wheat, rice

Calvin Cycle:

-Uses the ATP and electrons from NADPH molecules from the light reactions to drive the production of sugar (ATP is energy source and NADPH provides electrons for reducing CO2 to sugar) -CO2 taken into plant from air is constructed into glyceraldehyde 3-phosphate (G3P) -G3P is then used as the raw material to make glucose and other organic compounds

What is the "cost" to make 1 molecule of glucose?

6 turns of the Calvin cycle, or 6 CO2, 18 ATP, and 12 NADPH

Calvin Cycle Inputs:

ATP NADPH Carbon dioxide

In what ways are photosynthesis and cellular respiration nearly opposite processes?

At the level of overall reactions, photosynthesis and cellular respiration are near-opposite processes. They differ only in the form of energy absorbed or released.

Autotroph vs heterotroph

Autotrophs create their own energy through sunlight, Heterotrophs eat to obtain energy.

Why is photosystem II named 2 if it comes first during photosynthesis?

Because it was discovered after photosystem 1

Why are carnivores, such as lions, dependent on photosynthesis to survive?

Because lions eat animals that eat plants.

Why do plant appear green to us?

Because they contain many chlorophyll a(alpha) and b (beta) molecules, which reflect green light

What are the roles of ATP and NADPH in photosynthesis?

Both of these molecules carry energy; in the case of NADPH, it has reducing power that is used to fuel the process of making carbohydrate molecules in light-independent reactions.

Alternative Modes to Photosynthesis:

C3 plants, C4 plants, and CAM plants

Which color(s) of light is absorbed by carotenoids?

Carotenoids absorb violet and blue-green light.

What function(s) other than helping to capture light do carotenoids fulfill?

Carotenoids in chloroplasts help absorb the excess energy and dissipate it as heat. Also play an important role in getting rid of excess light energy.

Which color(s) of light does chlorophyll absorb?

Chlorophyll absorbs blue and red wavelengths.

Where in plants does a majority of photosynthesis take place?

Chloroplasts

Calvin Cycle Outputs:

G3P Regenerate rubisco

Where do the light-dependent reactions of photosynthesis occur?

In the thylakoid membrane

What is a photosystem?

Large complexes of proteins and pigments that are optimized to harvest light, play a key role in the light reactions.

light reactions outputs:

Oxygen ATP NAPDH

Producer vs consumer

Producer=makes own food for energy Consumer=eats food for energy

What colors have the longest wavelengths? in order from most to least

ROYGBIV

What is the overall outcome of the light reactions in photosynthesis?

The outcome of light reactions in photosynthesis is the conversion of solar energy into chemical energy that the chloroplasts can use to do work (mostly anabolic production of carbohydrates from carbon dioxide).

Where does the Calvin cycle take place?

The stroma of the chloroplast

What is the function of a pigment?

They absorb only specific wavelengths of visible light, while reflecting others

Where do the light-dependent reactions take place?

Thylakoid membranes of organelles called chloroplasts.

How are thylakoids and grana related?

Thylakoids are arranged in piles like stacks of pancakes that are known as grand—singular granum.

What is the basic structure of chloroplasts includes

Thylakoids: light-dependent reactions takes place here Stroma: light-independent reactions take place here Grana: Thylakoids are arranged in piles like stacks of pancakes that are known as grand—singular granum.

Which of the following components is not used by both plants and cyanobacteria to carry out photosynthesis? a. chloroplasts b. chlorophyll c. carbon dioxide d. water

a. chloroplasts

Which statement correctly describes carbon fixation? a. the conversion of CO2 into an organic compound b. the use of RuBisCO to form 3-PGA c. the production of carbohydrate molecules from G3P d. the formation of RuBP from G3P molecules e. the use of ATP and NADPH to reduce CO2

a. the conversion of CO2 into an organic compound

Which statement about thylakoids in eukaryotes is not correct? a. Thylakoids are assembled into stacks. b. Thylakoids exist as a maze of folded membranes. c. The space surrounding thylakoids is called stroma. d. Thylakoids contain chlorophyll.

b. Thylakoids exist as a maze of folded membranes.

From which component of the light-dependent reactions does NADPH form most directly? a. photosystem II b. photosystem I c. cytochrome complex d. ATP synthase

b. photosystem I

In which compartment of the plant cell do the light-independent reactions of photosynthesis take place? a. thylakoid b. stroma c. outer membrane d. mesophyll

b. stroma

Calvin Cycle, also called the dark reactions or light-independent reactions- because

because does not need the sunlight

Where in eukaryotic cells does the Calvin cycle take place? a. thylakoid membrane b. thylakoid lumen c. chloroplast stroma d. granum

c. chloroplast stroma

What two main products result from photosynthesis? a. oxygen and carbon dioxide b. chlorophyll and oxygen c. sugars/carbohydrates and oxygen d. sugars/carbohydrates and carbon dioxide

c. sugars/carbohydrates and oxygen

Photosystems

chlorophyll molecules and other pigments and protons clustered together

wavelengths are the distance between two ___________

crests or throughs

Which molecule must enter the Calvin cycle continually for the light-independent reactions to take place? a. RuBisCO b. RuBP c. 3-PGA d. CO2

d. CO2

Plants can absorb all but __________ light energy

green and this is why we see plants as green, because the light is reflected back

Red has the ________________ wavelength

longest

The shorter the wavelength, the ________ the energy

more

Violet has the ________ most energy, red has the _________ energy

most least

Reactants and products of photosynthesis

reactants: carbon dioxide, water, and solar energy products: glucose and oxygen oxygen is waste product

violet has the _________ wavelength

shortest

Calvin cycle occurs in the

stroma of the chloroplasts

The Calvin cycle is where ________ is actually made.

sugar

light-dependent reactions occur in the :

thylakoid membrane of the chloroplast

visible radiation

wavelengths of light that human eyes can detect