Bootcamp.com - Photosynthesis

_____ are organisms (like humans) that obtain chemical energy from the food they eat

heterotrophs

_____ organisms are capable of making their own food

autotrophic

_____ (like plants) capture solar energy and convert it to chemical energy by photosynthesis

photoautotrophs

_____ creates chemical energy which is passed up the food web to all organisms

photosynthesis

photosynthesis releases _____, which is crucial for aerobic cellular respiration

oxygen

photosynthesis reduces _____ from the atmosphere

carbon dioxide

photosynthesis uses _____ to make _____

photons (light energy); sugars (glucose)

_____ occurs when inorganic carbon is incorporated into an organic molecule (like a sugar molecule)

carbon fixation

write the overall chemical equation for photosynthesis:

6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂

The two stages of photosynthesis are the _________ and the ____________

light dependent reactions; Calvin cycle

light dependent reactions produce _____ and _____

ATP; NADPH

the Calvin cycle (or light independent reaction) uses energy stored in _____ and _____

ATP; NADPH

photosynthesis stores solar energy in glucose chemical bonds - how do plants then use that energy?

aerobic cellular respiration

photosynthesis has a positive Gibbs free energy (+ ΔG), so it is _____ and _____

non-spontaneous; endergonic

the overall reactions of aerobic cellular respiration and photosynthesis are ______

opposites

solar energy is input to photosynthesis to convert 6 _____ & 6 _____ to 1 _____ and 6 _____

CO2; H2O; Glucose; O2

chemical energy is released as heat and ATP during aerobic cellular respiration, where 1 _____ and 6 _____ convert to 6 _____ & 6 _____

glucose; O2; CO2; H2O

ATP from the light dependent reactions is not used to _____

power the cell

ATP from the light dependent reactions is consumed to power the _____, which makes glucose

Calvin cycle

_____ tissue is the outer layer of cells - what is its function?

epidermis; it provides protection and prevents water loss

_____ mesophyll cells conduct most photosynthesis

palisade

palisade mesophyll cells contain many _____, and are well organized as a single layer below the _____

chloroplasts; upper epidermis

spongy mesophyll cells conduct some photosynthesis, but not as much as the _____ cells

palisade mesophyll

spongy mesophyll cells have few _____

chloroplasts

spongy mesophyll cells are found toward the _____

bottom of the leaf

gaps between spongy mesophyll cells facilitate the movement of _____

gases

stomata are pores mainly found in the _____ of leaves and they are the site of _____

bottoms; atmospheric gas exchange

_____ surround stomata, and they control whether the stomata are open or closed

guard cells

_____ are dual membrane organelles found in plants and photosynthetic algae

chloroplasts

organisms with chloroplasts for photosynthesis will have _____ for cellular respiration too

mitochondria

chloroplasts contain thylakoids, where _____ occur

light dependent reactions

both stages of photosynthesis occur within _____

chloroplasts

_____ are photosynthetic organisms that do not have a chloroplast

cyanobacteria

the _____ is the fluid material that fills area inside the inner membrane of a chloroplast

stroma

the Calvin cycle occurs in the _____ of the chloroplast

stroma

_____ are phospholipid bilayer structured organelles that are suspended within the stroma

thylakoids

Light dependent reactions occur in the _______ of chloroplasts

thylakoid membranes

an entire stack of thylakoids is called a _____

granum

a junction between two grana is called a _____

lamella

protons (H⁺) for chloroplast chemiosmosis accumulate in the _____

thylakoid lumen

ATP synthesis in the chloroplast occurs as protons (H⁺) flow from the _____ to the _____

thylakoid lumen; stroma

thylakoid membranes have _____ to capture photons

photosystems

photosystems contain special _____, including chlorophylls and carotenoids

pigments

photosystem _____ are directly responsible for absorbing photons

pigments

what are the 2 important photosystems for photosynthesis?

photosystem I and II

photosystems I and II each have a _____ of chlorophyll molecules located in the center of the protein. This is known as the _____

special pair; reaction center

the special pair of chlorophyll molecules in photosystem I is known as _____

P700

the special pair of chlorophyll molecules in photosystem II is known as _____

P680

_____ of water involves the splitting of H₂O molecules into electrons (e⁻), protons (H⁺), and oxygen gas (O₂)

photolysis

where do the electrons (e⁻) from photolysis travel to in photosystem II?

they travel to the special pair at P680 of photosystem II (the reaction center)

When photons reach photosystem II, they will excite electrons (e⁻) at the _______. This causes the electrons (e⁻) to be passed to a primary __________

reaction center; electron accepter

as electrons (e⁻) travel down the primary electron transport chain (ETC) of the thylakoid membrane, they release energy that is used for _____ into the _____ from the stroma.

pumping protons (H⁺); thylakoid lumen

after traveling down the primary electron transport chain (ETC) of the thylakoid membrane, electrons (e⁻) will reach _____

photosystem I (P700 special pair - reaction center)

what is the purpose of the secondary ETC (following PSI) in the light-dependent reactions?

to reduce NADP+ --> NADPH using NADP+ reductase

describe the general pathway of non-cyclic photophosphorylation:

photolysis → Photosystem II (P680) → primary ETC→ Photosystem I (P700) → secondary ETC → NADP+ reductase to make NADPH

non-cyclic photophosphorylation requires light (photons) to be absorbed _____ - one time at each photosystem

twice

electrons (e⁻) do not travel to the _____ in cyclic photophosphorylation, thus _____ is not produced

second ETC; NADPH

describe the general pathway for cyclic photophosphorylation:

photolysis → Photosystem II (P680) → primary ETC → Photosystem I (P700) → primary ETC → Photosystem I (P700) → etc.

what are the products of the light dependent reactions?

ATP and NADPH, O₂ (waste product)

'normal' photosynthesis can also be called _____ because the carbon fixation step of the Calvin cycle produces three-carbon molecules

C3 photosynthesis

what are the products of the Calvin cycle?

Glucose, ADP, NADP+

the Calvin cycle is sometimes referred to as the _____ because it does not use light energy directly

light independent reactions

the _____ cannot occur without light because it is dependent on the high energy molecules produced from the light reaction (ATP and NADPH)

Calvin cycle

the Calvin cycle fixes _____ into _____

inorganic carbon dioxide; organic glucose sugars

the Calvin cycle must accept _____ CO₂ molecules to synthesize _____ glucose molecule.

6 CO₂; 1 C₆H₁₂O₆ (glucose)

list the 4 steps of the Calvin cycle in order:

carbon fixation; reduction of a 3-carbon intermediate; regeneration of RuBP; carbohydrate synthesis

describe the carbon fixation step (step 1) of the Calvin cycle with an equation and in words:

6 CO₂ + 6 RuBP → 12 PGA

catalyzed by RuBisCo

CO₂ (one-carbon) combines with RuBP (five-carbons) to produce a six-carbon molecule that splits into 2 PGA molecules (three-carbons per PGA molecule)

describe the reduction step (step 2) of the Calvin cycle with an equation and in words:

12 ATP + 12 NADPH converts 12 PGA → 12 G-3-P

ATP from the light dependent reactions will phosphorylate the PGA from carbon fixation to produce another three-carbon intermediate.

NADPH from the light dependent reactions reduces the three-carbon intermediate to produce G3P sugars

describe the regeneration step (step 3) of the Calvin cycle with an equation and in words:

6 ATP converts 10 (of the 12) G-3-P → 6 RuBP

Some G3P will be used to regenerate RuBP so that the cycle can continue. This requires ATP from the light dependent reactions.

Alternatively, some G3P will be saved for step 4 of the Calvin cycle.

describe the carbohydrate (glucose) synthesis step (step 4) of the Calvin cycle with an equation and in words:

2 G3P → 1 glucose

The 2 remaining G3P (three-carbon molecule) that were leftover from step 3 are used to build glucose (six-carbon molecule).

RuBisCo can also bind _____ in a process called _____

oxygen; photorespiration

plants in hot and dry environments ____ their stomata to minimize _____. This results in ____ not being able to leave and ____ not being able to enter the leaf.

close; water loss; oxygen; carbon dioxide

when plants in hot and dry environments _____ their stomata, RuBisCo is encouraged to bind _____ and photorespiration starts to occur

close; oxygen

the byproducts of photorespiration are metabolized by _____ & _____

peroxisomes; mitochondria

what are 2 mechanisms plants have evolved to minimize photorespiration?

C4 photosynthesis and CAM (crassulacean acid metabolism) photosynthesis

In the mesophyll cell, C4 photosynthesis uses an enzyme called _____, which fixes CO₂ into a three-carbon molecule called _____

PEP carboxylase; PEP

in C4 photosynthesis, CO2 + PEP in the presence of PEP carboxylase makes _____ at the mesophyll cell

oxaloacetate

in C4 photosynthesis, oxaloacetate quickly converts to _____ at the mesophyll cell

malate

C4 photosynthesis is called C4 because..?

both oxaloacetate and malate are 4 carbon compounds

in C4 photosynthesis, malate is transported from _____ cells to _____ cells

mesophyll; bundle sheath

the CO₂ released at the bundle sheath cell of C4 photosynthesis can undergo carbon fixation using _____

RuBisCo

what is the advantage of bundle sheath cells in C4 photosynthesis?

they do not contain as much O₂, so photorespiration is less likely to occur

what happens to the three-carbon pyruvate at the bundle sheath cell of C4 photosynthesis?

it is shuttled back to the mesophyll cell alongside the hydrolysis of ATP → AMP

what does pyruvate convert into when back at the mesophyll cell of C4 photosynthesis?

PEP

C4 photosynthesis occurs in a small percentage of plants living in _____ environments

hot

C4 photosynthesis prevents photorespiration through the _____ of carbon dioxide

spatial isolation

_____ means that inorganic carbon is transported to a different location to prevent photorespiration

spatial isolation

CAM plants use _____, which prevents photorespiration through timing

temporal isolation

CAM plants close their stomata during the ___ to prevent transpiration

day

At ____, CAM plants have their stomata open, allowing carbon dioxide to enter the leaf

night

after CO₂ diffuses into the mesophyll of CAM plants (at night), what happens?

PEP carboxylase will take

CO₂ (one-carbon) + PEP (three-carbon) to produce oxaloacetate (four-carbon), which converts to malate (four-carbon)

what happens to the four-carbon malate molecule produced in CAM photosynthesis?

it is stored in the vacuole of the mesophyll cell for later use

in CAM photosynthesis, during the next day when the stomata are ______, malate will convert back into ________

closed; oxaloacetate

the overall advantage is that CAM photosynthesis can proceed during the day while stomata are _____ (reducing _____ loss)

closed; water (H₂O)