photosynthesis

Which molecule absorbs the energy of a photon in photosynthesis?

chlorophyll

Second step of light reactions

photons are absorbed and excite the electron 2. Both electrons captured by primary electron acceptor.

Sugar generated from Calvin cycle used for 3 things:

1. Cellular respiration 2. Starch storage 3. Cellulose

Third step of light reactions

3. Water is split to provide missing electrons to chlorophyll. Oxygen is byproduct.

fourth step of light reactions

4. Excited electrons passed from PSII to PSI via electron transport. Energy used to pump H+, making ATP. Chemiosmosis

Fifth step of light reaction

5. Photon excites PSI, boosting electrons to electron acceptor.

Sixth step of light reactions

6. Excited electrons passed to NADP+ (a high-energy electron carrier).

Photosynthesis equation

6CO2 + 6H2O --> light energy --> C6H12O6 + 6O2 reaction is the opposite of cellular resp just atp is switched with light energy

Energy captured in two photosystems

Arrangements of light catching pigments (chlorophyll) Transfer light energy to electrons, then to electron acceptors

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

Because lions eat animals that eat plants.

Where does the mass in a tree come from? (not the soil!)

CO2 gets solid

Plant cells need ATP in order to function. During which process do they make most of their ATP?

Cellular respiration

Sunlight

Electromagnetic energy •Photon: fixed amount of light energy *visible light

Calvin Cycle (Reduction)

Energy from ATP and NADPH are added to molecules to make glyceraldehyde 3 phosphate sugar (G3P). 3 phosphate sugar: half of a sugar (basic sugars have 6 carbons) Some converted to glucose or fructose.

Chemiosmosis in light reactions

Energy from electron transport pumps H+ against its concentration gradient Used to generate ATP

What is the molecule that leaves the Calvin cycle to be converted into glucose?

G3P

Leaf

Gases exchange through stomata (holes) •Water from roots via veins •Photosynthesis takes place in chloroplasts in cells

Which color(s) of light does chlorophyll a reflect?

Green is reflected, and given that plants have a lot of it, that is why plants are green. In the fall, chlorophyll breaks down in leaves, causing them to turn red, orange, and yellow as the other pigments, including the carotenoids, begin to dominate. Eventually, as the leaves start to freeze, the other pigments will be broken down as well, resulting in death for the leaves.

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

Idk

thylakoid space

LUMEN space inside thylakoid

On a hot, dry day, plants close their stomata to conserve water. What impact will this have on photosynthesis?

Levels of carbon dioxide (one of the reactants) will fall, and levels of oxygen (a product) will rise. As a result, the rate of photosynthesis will slow down.

In photo reactions, what does light energy do?

Light energy excites an electron in chlorophyll

The "synthesis" reactions:

Light-independent In stroma CO2, ATP, and NADPH used to make sugar **needs CO2 from air

Are synthesis reactions light dependent or independent? Why?

Light-independent don't need light anymore that was only for photo reactions

where are Chlorophyll located?

Located in thylakoids

Which part of the Calvin cycle would be affected if a cell could not produce the enzyme RuBisCO?

None of the cycle could take place, because RuBisCO is essential in fixing carbon dioxide. Specifically, RuBisCO catalyzes the reaction between carbon dioxide and RuBP at the start of the cycle.

In light reactions, What is left after water is used?

Oxygen, O2 H2O --> 1/2 O2 + 2H+ + 2e- 2H+: oxidative Phosphorylation 2e-: for photo reactions 1/2 O2 (O1): waste

Where does photosynthesis take place?

Photosynthesis takes place in chloroplasts in cells

Explain the reciprocal nature of the net chemical reactions for photosynthesis and respiration.

Photosynthesis takes the energy of sunlight and combines water and carbon dioxide to produce sugar and oxygen as a waste product. The reactions of respiration take sugar and consume oxygen to break it down into carbon dioxide and water, releasing energy. Thus, the reactants of photosynthesis are the products of respiration, and vice versa.

autotrophs

Photosynthesizers are autotrophs :make enough food to sustain themselves

What does photosynthesis do?

Photosynthesizers are producers:produce biosphere food supply (176 billion tons of carbohydrates per year, plus oxygen for aerobic organisms!) reaction is the opposite of cellular resp just atp is switched with light energy

Chlorophyll

Pigments that absorb light Located in thylakoids

Chlorophyll

Pigments that absorb light •Located in thylakoids

Calvin Cycle (Regeneration)

Some G3P used to regenerate RuBP. For 3 CO2 in, 6 intermediates made, 1 G3P, 5 G3P recycled to 3 RuBP

Describe the pathway of energy in light-dependent reactions.

The energy is present initially as light. A photon of light hits chlorophyll, causing an electron to be energized. The free electron travels through the electron transport chain, and the energy of the electron is used to pump hydrogen ions into the thylakoid space, transferring the energy into the electrochemical gradient. The energy of the electrochemical gradient is used to power ATP synthase, and the energy is transferred into a bond in the ATP molecule. In addition, energy from another photon can be used to create a high-energy bond in the molecule NADPH.

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

To convert solar energy into chemical energy that cells can use to do work.

Chlorophyll absorbs some wavelengths of light. What determines the colors that we see?

We see what is reflected

Why do black surfaces get hotter than white ones?

black is the absence of light, so ALL wavelengths of light are absorbed and it is hot because it absorbs a lot of light energy white has all wavelengths already so it absorbs no light and doesn't get hot

Do chloroplasts have a single or double membrane?

double

From where does a heterotroph directly obtain its energy?

eating other organisms

What is the energy of a photon first used to do in photosynthesis?

energize an electron

Photon

fixed amount of light energy, 1 unit of light energy

Why do plants need CO2?

for synthesis reactions, makes sugar in calvin cycle

What two products result from photosynthesis?

glucose and oxygen

Stroma

interior fluid

What are the two sources of photosynthesis reactions?

light dependent and light independent

Why do plants need sunlight? (be specific)

light energy, needs photons

Thylakoid

membrane sacs

For the stoma, what leaves and what comes in?

oxygen leaves and CO2 gets in

First step of light reactions

solar-powered transfer of an electron from a chlorophyll a molecule to the primary electron acceptor 1. PSII pigment absorbs photon. Energy passed, eventually exciting electron of reaction center chlorophyll. Happens again with second electron. 2 electrons from water so it needs 2 photons of light to boost up

Plants produce oxygen when they photosynthesize. Where does the oxygen come from?

splitting water molecules

Gases exchange through ____?

stomata

Where do the "synthesis" reactions take place?

stroma

Where in plant cells does the Calvin cycle take place?

stroma of the chloroplast

Calvin Cycle

synthesis reaction a biochemical pathway of photosynthesis in which carbon dioxide is converted into glucose using ATP

Calvin Cycle (Carbon Fixation)

synthesis reaction Takes CO2 from air and sticks it to something solid so it is "fixed" Carbon fixation: Enzyme rubisco takes CO2 from air and attaches it to RuBP (an organic molecule). Molecule splits into two. **in image, after rubisco, split in half

Where do the "photo" reactions take place?

thylakoid

Why do plants need water? (be specific)

to take two electrons to boost them to a higher energy state

Do plants do cellular respiration?

yes because photosynthesis does not make ATP

Chloroplast

•Double membrane •Thylakoid: membrane sacs •Thylakoid space = lumen •Stroma: interior fluid

Photo reactions

•Light energy captured •Results in high energy molecules and oxygen