Photosynthesis

What does photosynthesis do

converts light energy into chemical energy of food

what do photoautotrophs use to make organic molecules

light energy

what do chemoautotrophs use to make organic molecules

chemicals in the enviroment

mesophyll

the middle of a leaf, chloroplasts are mainly found in these cells of a leaf 

what type of reaction is photosynthesis (catabolic or anabolic)

anabolic

what is the meaning of anabolic

reaction where a large molecule is produced

is photosynthesis exergonic or endergonic 

endergonic

what does endergonic mean

energy enters the process (reactant)

what does exergonic mean

energy exits the process (product)

what are the reactants of photosynthesis

light energy + 6H2O + 6CO2

what are the products of photosynthesis

C₆H₁₂O₆ + 6O2

how do heterotrophs get organic molecules

consume them from other organisms 

stomata

pores in lead (CO2 enter/O2 exits)

thylakoids

flat green pancakes that store chlorophyll and collect sun energy for first part of photosynthesis

grana

stacks of thylakoids; a way the cells increase SA

stroma

the fluid that surrounds the thylakoids where the second half of photosynthesis occurs; contains ribosomes and chloroplast DNA

What is the light reaction step of photosynthesis

first step of photosynthesis; light energy is converted into ATP/NADPH using electrons from H₂0

where do light reactions occur

thylakoids

what is the calvin cycle of photosynthesis 

second step of photosynthesis (light independent); takes that newly made ATP to power chemical reactions (with the help from enzymes), converting CO₂ and the H from H₂0 into glucose

where does the calvin cycle take place

stroma

what are the reactants of the light reactions

H2O + light energy

what are the products of light reactions 

ATP + NADPH + O2

What reaction uses photosystems

light reactions

what is a photosystem

a cluster of pigment molecules bound to proteins, along with a primary electron acceptor

how do the pigments of photosystems change the function

different pigments absorb different wavelengths of light energy 

what is chlorophyll a (color and function)

blue-green, pigment that converts light to chemical energy

what is chlorophyll b (color and function)

yellow-green, pigment that conveys energy to chlorophyll a 

what are carotenoids (color and function)

yellow/orange, pigment that does photoprotection (protects against excess light) and broadens color spectrum for photosynthesis

how do the electrons in pigment molecules work

get excited by the absorption of light

Explain Photosystem II 

• Absorbs light best at a wavelength of 680nm

• Actually occurs first in the light dependent reaction- it was discovered after PS1

• Provides energy to create ATP

  • water gives electrons to PSII

explain Photosystem I

• Absorbs light best at a wavelength of 700nm

• Provides energy to create NADPH (another form of stored energy, like cAMP or ATP)

How is the ETC in photosynthesis similar and different from the ETC in cellular respiration

Similarities:

• use excited electrons to power active transport of H+

• create proton gradient to power ATP synthase Differences

• Source of electrons: light photon vs NADH

• Products: ATP and NADPH vs NAD+, FAD, H2O, and ATP

what is photophosphorylation

The phosphorylation of ADP to form ATP using the energy of sunlight by Photosystem II

Non-Cyclic photophosphorylation

ideal

light reactions elevate electrons in two steps (PSII and PSI)

• PSII generates energy as ATP

• PSI generates reducing power as NADPH

Cyclic photophosphorylation

Non-ideal

Calvin cycle requires more ATP than is made during the light reactions

If there is not enough ATP, electrons are cycled back to ETC

• More ATP is made

• No NADPH is made

What are the calvin cycle reactants

CO2 + ATP + NADPH

what are the Calvin Cycle products

C₆H₁₂O₆ + ADP + NADP⁺

Is the Calvin Cycle light dependent or light independent

light -independent

where does the calvin cycle ocur

stroma of chloroplasts

what does the Calvin cycle produce (not final products)

3 carbon sugar, G3P (glyceraldehyde-3-phosphate)

Explain process of Calvin cycle

uses chemical energy (ATP and NADPH) to reduce CO₂ (low energy) and synthesize C₆H₁₂O₆ (high energy)

what are the three phases of the calvin cycle

carbon fixation, reduction, and regeneration

What is the carbon fixation step of the calvin cycle

carbon dioxide is “fixed” into a carbohydrate by the enzyme Rubisco

what is the reduction step of the calvin cycle

6 ATP and 6 NADPH are used to make 6 G3P molecules.

The 6 ADP and 6 NADP⁺ go back to the light reactions to be reused and re-energized `

what is the regeneration step of the calvin cycle

1 G3P leaves the cycle, the other 5 are used to regenerate RuBP (end product that gets used in first step) so that another carbon can be “fixed” into a carbohydrate → makes it a cycle

How many times does the calvin cycle have to occur to make 1 molecule of glucose 

2 times

What is G3P and how is it used 

end product of calvin cycle

energy-rich 3 carbon sugar

important intermediate to other molecules (can be used to form glucose, lipids, amino acids, and nucleic acids)

what is the process that creates G3P called

C3 photosynthesis

what is photorespiration and why does it occur and what does it produce

on hot, dry days plants partially close their stomata to try to conserve water therefore reducing their intake of CO₂. In response, Rubisco binds oxygen instead creating a photorespiration cycle

Produces CO₂ and 1 G3P (does not produce sugar)w

why do some plants use a C4 cycle

to avoid photorespiration 

Explain C4 process, why it occurs, and what it produces

In Mesophyll cells: PEP carboxylase fixes CO₂ (4-C) and C4 pathway pumps CO₂ bundle sheath

In Bundle sheath cells: CO₂ used in Calvin Cycle

Lower photorespiration so higher sugar production

On hot, dry days the stomata close

Explain the CAM process and why it occurs

CAM = crassulacean acid metabolism

Night: Stomata open → CO₂ enters → converts to organic acid stored in mesophyll cells

Day: Stomata closed → light reactions supply ATP and NADPH; CO₂ released from organic acids for calvin cycle

Gives advantage in arid conditions