KC 9

photosynthesis

converts light energy into chemical energy

where does photosynthesis occur

chloroplasts

equation

Carbon dioxide + water + light energy = glucose + oxygen

where does light-dependent reactions occur

thylakoid membrane

where does light-independent (Calvin cycle) reactions occur

stroma

outer membrane

permeable to small molecules

inner membrane

contains thylakoid membrane

stroma

fluid-filled space surrounding thylakoids

thylakoids

membrane-bound sacs where light reactions occur; stacked into grana

light-dependent reaction input

light energy, water, NADP+, ADP, and inorganic phosphate

light-dependent reaction output

Oxygen, ATP, NADPH

light-dependent process

photolysis; ETC; ATP synthesis; NADPH formation

photolysis

water is split into oxygen, protons, and electrons

ETC

electrons move through proteins in the thylakoid membrane, generating a proton gradient

Calvin cycle input

CO2, ATP, NADPH

calvin cycle output

G3P

Calvin cycle process

Carbon fixation; reduction; regeneration

Carotenoids

Accessory pigments that protect the plant by absorbing light in different wavelengths

photosystems

clusters of pigment molecules embedded in the thylakoid membrane of chloroplasts

Photosystem II

Uses light energy to split water molecules and release oxygen, initiating the ETC

Photosystem I

Uses light energy to boost electrons to a higher energy level and reduce NADP+ to NADPH

ATP synthase

proton gradient drives protons through ATP synthase, leading to the production of ATP from ADP and inorganic phosphate

photorespiration

enzyme rubisco binds to oxygen instead of carbon dioxide, leading to the production of a waste product and a decrease in photosynthetic efficiency

effect of photorespiration

It reduces the overall efficiency of photosynthesis, particularly in hot, dry conditions

C3 plants

The standard pathway; inefficient under hot, dry conditions

C4 plants

Separate initial CO2 fixation in mesophyll cells and Calvin cycle in bundle-sheath cells, increasing efficiency

CAM plants

Open stomata at night to fix CO2, minimizing water loss during the day

how light intensity affects photosynthesis

As light intensity increases, the rate of photosynthesis increases, but only to a point

how carbon dioxide concentration affects photosynthesis

More CO2 increases the rate of photosynthesis, as it is a substrate for the Calvin cycle

how temperature affects photosynthesis

High temperatures can accelerate photosynthesis up to a point. enzymes may become denatured, slowing the process

how water availability affects photosynthesis

Insufficient water limits the plant's ability to perform photosynthesis because water is necessary for the light-dependent reactions

photophosphorylation

The process of generating ATP from ADP using light energy

autotrophs

Organisms that make their own food through photosynthesis

heterotrophs

Organisms that obtain food by consuming other organisms

fitness

how good an organism is at surviving, reproducing, and passing on its genes

higher fitness

more offspring that survive and reproduce

relative fitness

How an individual compares to others in the population in terms of producing offspring

mutations

Random changes in DNA that create new traits

Gene flow

When individuals from different populations mix, bringing in new traits

Genetic drift

Random changes in gene frequencies