Biology Photosynthesis Study Guide

These are organisms that make its own food.

These are organisms that have to eat food.



Van Helmont
He did an experiment to learn where the mass of a growing plant came from. He dried out soil, weighed it, grew a plant in the soil, pulled out the plant, dried out the soil again, weighted it again, and found that the weight was the same.

He did an experiment and found out that plants produce oxygen that allows a candle to be relit in a sealed container. Light is necessary to produce this oxygen.

Photosynthesis Summary Equation
6CO2 + 6H2O (light) C6H12O6 + 6O2

Light and Pigments
Pigments can absorb, transmit, or reflect light energy. In plants, green is the main pigment. The color that we see is the color that is reflected. All the other colors are absorbed by the thing. They act as a light antenna to absorb light energy.

This is the site of the light reactions. They are membrane sacs inside the chloroplasts. Groups of these are called granum. Pigments are embedded here.

This is the space around the thylakoid where dark reactions occur.

This is an electron carrier that transports high energy electrons and hydrogen ions around during photosynthesis like a school bus going from the light to dark reactions.

Light Reactions
Absorbed light energy causes an electron to leave the chlorophyll in photosystem II. Water breaks apart through photolysis to replace the electron lost and oxygen is a waste product. The electrons passes down the electron transport chain via electron carriers. Hydrogen ions are released into the thylakoid space. A series of redox reactions occur (each carrier is reduced and then oxidized). The energy that is released by this pumps hydrogen ions into the inner thylakoid space creating a hydrogen ion concentration gradient. The electron lands in photosystem I. It then jumps off into NADP with hydrogen ions from NADPH, the hydrogen ions in the thylakoid space go through the ATP synthase enzyme to make ATP.

Calvin Cycle/Light Independent Reactions
This does not require light directly but needs it indirectly so the light reactions to work which comes before it. Carbon dioxide is added to a five carbon molecule which is very unstable so it immediately breaks apart into two three carbon molecules called 3PG or PGA by the enzyme RuBisCo. ATP and NADPH turn the 3PG to G3P (or PGA to PGAL). Some of these molecules are used to create glucose while some are reused in the Calvin cycle (form RuBP).

Chlorophyll A

Chlorophyll B

What is required for the light reactions
light, water (for replacing the electron)

Accessory Pigments
These are pigments that absorb other colors that chlorophyll cannot.

This is the process through which water splits during the light cycle. Oxygen is a waste product. The electron produced by this replaces the lost one.

Electron Transport Chain
An electron from photosystem II passes down this via electron carriers.

Photosystem I
The second photosystem, electrons jump off of this into NADP with hydrogen ions from NADPH.

Photosystem II
The first photosystem, this system has the electron transport chain

ATP Synthase
This is the enzyme that hydrogen ions go through to turn into ATP.

Hydrogen Proton Concentration Gradient
The energy that is released from the redox reactions pumps hydrogen ions into the inner thylakoid space to create this.

This is the process when the hydrogen ions diffuse through the ATP synthase.

Products of Light Reactions
oxygen as a waste, ATP, NADPH

Requirements for the Calvin Cycle
that the light cycle works

Carbon Fixation
This is also called carboxylation, carbon dioxide is added to a five carbon molecule RuBP, the unstable six carbon molecule breaks quickly into two three carbon molecules by RuBisCo.

The five carbon molecule that the carbon dioxide is added to.

This enzyme breaks apart the six carbon molecule into two three carbon molecules.

This is also 3PG, the name for the three carbon molecule

This process is also called reshuffling, ATP and NADPH turn 3PG into G3P, some of these go to make glucose (it needs two three carbon molecules)

The reshuffled form of PGA, turned into this by ATP and NADPH, some can be recycled for the next cycle or made into glucose

This process is also recycling, some G3P or PGAL molecules are recycled into RuBP, requires ATP

Products of Calvin Cycle

Light Intensity
Not enough light results in not enough energy for the light reaction to take place, photosynthesis rate goes down

If the temperature is too high or too low the photosynthesis rate will go down

Concentration of Oxygen
If there is more oxygen, the rate of photosynthesis will decrease

Concentration of Carbon Dioxide
If there is more carbon dioxide, the rate of photosynthesis will increase

If there is not enough water, the rate of photosynthesis will go down

If there is too much oxygen, the Calvin cycle will get hijacked. RuBisCo will attach oxygen to RuBp instead of carbon dioxide, this reduces the rate and efficiency by pulling off carbon, lowers 50%-100%

These are small pores on the underside of leaves that allow for air to enter and exit. These usually open during the daytime for carbon dioxide to get in for photosynthesis. Carbon dioxide goes in and oxygen goes out. Water vapor might escape during the heat.

Mesophyll cells
surround the bundle sheath cells

Bundle Sheath Cells
where the Calvin cycle occurs in C4 (and CAM?), surrounded by mesophyll cells

This is the evaporation of water from a leaf when it is hot and dry. The plant needs to close the stomata but no carbon dioxide will get in and no oxygen will go out.

CAM Photosynthesis
In this solution, the plant only opens the stomata when it is cool (night) and stores the CO2 in the central vacuole. Collection occurs after (before?) the Calvin cycle. CO2 is joined to the PEP molecule and becomes an oxaloacetic acid that is converted to a 4 carbon malic acid and is stored in the vacuole. The 4 carbon acid is converted back to CO2 during the day for the Calvin Cycle. Cactus and pineapple do this.

Oxaloacetic Acid
This is what is created when CO2 is joined to the PEP molecule and is converted to a four carbon malic acid which is stored in the vacuole.

C4 Photosynthesis
Mesophyll cells surround the bundle sheath cells, CO2 is joined to the PEP molecule and becomes oxaloacetic acid which is then converted to a four carbon malic acid in the mesophyll cells. The 4 carbon acid is converted back to CO2 for the Calvin cycle in the bundle sheath cells. Oxygen is not allowed to enter to prevent photorespiration. Corn and sugar cane both use this.

C3 Photosynthesis
This is the most common type of photosynthesis used in roses and fruit trees.

Downsides to CAM and C4
The CO2 shuttle and storage is not free, adds two ATP per Co2 to the amount of energy needed for each CO2. Only good for plants in an an environment prone to photorespiration.

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