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