ch 10

Whats the point of photosynthesis

making sugar

who does photosynthesis

protista: algae

• unicellular

Prokaryotes: bluegreen algae (cyanobacteria)

• colonial or unicellular

who does not need photosynthesis and why

deep sea vent communities that are powered by reduced molecules

these drive metabolism of prokaryotes that form the base of the food web

cells must have an outside source of energy why?

because they cant make their own energy

because they need it to fight natural breakdown (entropy) of molecules

2 laws of thermodynamics is at play here

cellular respiration bonds

in sugars, fats, and proteins most useful energy is stored in C-C and C-H bonds

• oxidized by glycolysis and aerobic respiration

C-O bonds are not useful

Photosynthesis makes what types of bonds

C-C and C-H bonds

light can be what

absorbed

reflected

transmitted

why are plants green

green light is both reflected and transmitted and all other colors are absorbed

chlorophyll structure

magnesium atom in the middle

• surrounded by 4 nitrogens and C-H bonds

Hydrocarbon tail

• same in lipids

• anchors chlorophyll to the chloroplast membrane

  • this will keep it in position and contain light

why do fall leaves turn colors

they change color in fall because as plants absorb and store chlorophyll

other pigments from leaves are discarded since they are throwaway molecules

chlorophyll A

in cyanobacteria, eukaryotic green algae, and green plants

chlorophyll B

in green algae and green plants

is accessory pigment to chlorophyll a

accessory pigments do what

help chlorophyll do photosynthesis

get energy focused in chlorophyll too

in what parts of chloroplast does photosynthesis happen

light dependent: thylakoid

calvin cycle: stroma

where did chloroplasts come from

endosymbiosis: chloroplasts descended from photosynthetic bacteria that moved inside eukaryotic cells

endosymbiosis proof

chloroplasts have

• their own DNA

• small ribosomes

• double membrane

• uses inner membrane for photosynthesis

what is oxidized and reduced in photosynthesis equation

oxidized: CO2 + H2O

reduced: C6H12O6 + O2

light dependent equation

H2O + NADP + (ADP + Pi) ———> O2 + NADPH + ATP

p680 and p700 chlorophyll

light is used

calvin cycle equation

CO2 + ATP + NADPH ———> C6H12O6 + NADP + (ADP + Pi) + H2O

uses rubisco

how do electrons work in isolated chlorophyll molecule

when light energy hits a chlorophyll the electron will go to an excited state

electron will go back to ground state and releases light and heat

how does electrons work in photosynthesis

light hits accessory pigments chlorophyll passing down energy and eventually gets to special chlorophyll a

then the electron will go the reaction center in an excited state to primary electron acceptor

p680 and p700

are both forms of chlorophyll A but different in light sensitivity

Cyclic electron flow does what instead of going the other pathway

cycles electrons producing ATP without producing NADPH

rubisco

affected by competitive inhibitor

• oxygen will get in the way of CO2

  • oxygen is the inhibitor because it tears RuBp apart by stealing electrons

• have big active site

• makes sugar

parts of leaf

cuticle

palisade

chloroplasts

spongy layer

xylem

phloem

guard cells

waxy cuticle

reduces evaportation

palisade

point toward light to capture it well

circulates chloroplasts to get their temperature optimized

chloroplast

move up to catch more light and move down to cool off

spongy layer

provides air space for CO2/O2 exchange and evaporative cooling

solution to competitive inhibitor and denaturing of enzymes?

C4 photosynthesis

C4 photosynthesis why it needs to happen

the cell has high temperature and O2, rubisco won’t work well

C4 how does it work

PEP carboxylase captures CO2 to make 4 carbon molecule

• then that molecule will get passed to bundle-sheath cell

• unmakes the carbon molecule into CO2 and rubisco does its job

bundle sheath cell

deep inside the leaf where oxygen level are low

C4 plants

night: stomata opens, allowing CO2 storage at lower temperature

day: stomata closes, keeping evaporation low.

• light is available to make sugars from stored CO2