photosynthesis

thylakoids

sac-like photosynthetic membranes, on the diagram they are each individual member of a stack

granum

stack of thylakoids

stroma

region outside the thylakoid membranes in chloroplasts

light dependent reactions

reactions of photosynthesis that use energy from light and water to produce ATP and oxygen that is released into the atmosphere

Calvin Cycle / Light Independent reactions

plants use ATP and CO2 to produce high-energy sugars such as glucose

What is the function of ATP?

Provides small amounts of energy for cellular reactions to take place.

What factors affect photosynthesis

temperature, light intensity and the availability of water.

Where do light dependent reactions take place?

within the thylakoid membrane of the chloroplast

Where does the Calvin Cycle take place?

stroma

What molecules are NEEDED for photosynthesis?

carbon dioxide and water

What molecules are PRODUCED in photosynthesis?

glucose and oxygen

chloroplast

organelle where photosynthesis occurs

What pigment makes plants green?

chlorophyll

light-independent reaction are also called

Calvin Cycle, named after Melvin Calvin who discovered these reactions

chloroplast

organelle found in plant cells where photosynthesis takes place

Light-Dependent reaction

uses the energy from the sun to make ATP (Energy storage) and NADPH (electron carrier)

Parts of Light-dependent Reactions

photosystem 2, photosystem 1

Step 3 LD

the electrons then become super-charged by the light that is stored in the chloroplasts

Step 2 LD

oxygen is released into the air

Step 1 LD

water is brought in and split apart into 1 oxygen atom, 2 hydrogens, and 2 electrons

Step 4 LD

the energy from the electrons is used to push the hydrogen atoms through the thylakoid membrane from the stroma

Step 5 LD

H gradient is established (high concentration to low concentration across membrane)

Step 6 LD

the electrons now travel to Photosystem 1

Step 7 LD

pigments in Photosystem 2 re-energize the electrons

Step 8 LD

NADP+ picks up the electrons and 1 hydrogen atom at the OUTER SURFACE OF THE THYLAKOID MEMBRANE.

The NADP+ then becomes NADPH

Step 9 LD

hydrogen ions start to accumulate in the thylakoid space from the splitting of water and the pumping of the electrons (makes the thylakoid space negatively charged)

this gradient provides the energy to make ATP

Step 10 LD

powered by the gradient, the H+ ions pass through the ATP synthase to reach the stroma. as it rotates, the ATP synthase takes ADP and binds a phosphorus ion to it, changing it into ATP

light dependent reaction inputs

water, NADP+, ADP

light dependent reaction outputs

NADPH, ATP, O2

NADP --> NADPH

NADP gains all the H when the photons are traveling through the membrane.

Photosynthesis net reaction (EQUATION)

6CO2 + 6H2O → C6H12O6 + 6O2

Point of LD?

-To split water so H may go into the Calvin cycle and O2 can be used as a waste product

-To change light energy into chemical energy (NADPH, ATP) for the Calvin Cycle

ADP --> ATP

gains a phosphate

H2O Split

H2O and light enter pigments

-H2O is split

-O2 becomes waste product

-2H get sent through the electron transport chain for the reaction HAPPENS IN THYLAKOID SPACE

NADP

electron carrier

constantly being recycled

-gains hydrogen in thylakoids (LD)

-Drops off hydrogen in stoma (CC)

-Goes back to get hydrogens in thylakoids

-REPEATS THE CYCLE

Light-Independent Reactions

plants use the ATP and NADPH to create sugar for the plant's energy

where do the light-independent reactions take place?

stroma

Step 1 in CC

Carbon comes in (FROM THE AIR)

Step 2 in CC

Energy from ATP and NADPH (from LD reaction) is used to make high-energy sugars

What enters CC??

CO2 (from air)

NADPH + ATP (from LD)

What leaves CC??

Glucose --> plant food

NADP & ADP+Phosphate (Go back to LD to pick up more hydrogens and get energized again)

Pigments

Photons are absorbed in pigments (chemicals that absorb different wavelengths)

Light energy is absorbed + can then be converted into chemical energy

Reflection

When a plant contains a pigment and appears a certain color → it reflects the wavelength of that color

Energy from this wavelength is NOT being used

Absorption

All other color wavelengths but the color of the plant are being absorbed

The energy from these wavelengths ARE being used

White

All colors reflected

None absorbed

Black

None reflected

All colors absorbed

More pigments

= more energy = more sugar produced!!

Factors affecting photosynthesis

temperature, light intensity, water availability

temperature and photosynthesis

photosynthesis functions best between 0°C and 35°C. Temperatures above or below this range may affect the enzymes involved in photosynthesis.

light intensity and photosynthesis

High intensity light increases rate of photosynthesis. However, after it reaches a certain level, there is no increase in photosynthesis.

water and photosynthesis

A shortage of water can slow or even stop photosynthesis. Water loss can also damage plant tissues. Many plants have adaptions to prevent water loss.

Photosynthesis under extreme conditions

C4 photosynthesis and CAM plants

CAM plants

Crassulacean Acid Metabolism(CAM) plants admit air into their leaves only at night. This is an adaption to dry climate to obtain CO2 while minimizing water loss. In the cool darkness, carbon dioxide is combined with existing molecules to produce organic acids, "trapping" the carbon within the leaves. During the daytime, when leaves are tightly sealed to prevent water loss, these compounds release CO2, enabling sugar production. Examples: pineapple trees and desert cacti.

C4 photosynthesis

have a specialized chemical pathway that allows them to capture low levels of CO2 for the Calvin Cycle. The name "C4 plant comes from the first compound formed that is made up of 4 carbon atoms. The C4 pathway allows photosynthesis to work under intense light and high temperatures, but has the drawback of needing more ATP or energy to function. Examples include: corn, sugar cane, and sorghum.