Chapter 7 - Photosynthesis

40 terms by krissyc39 

Create a new folder

Advertisement Upgrade to remove ads

autotrophs

- produce their organic molecules
- source of organic compoundsfor heterotrops
-- producers
-- autorophtic bacteria
- ex. plants, algae, other protists and some prokaryotes

autotrophic bacteria

use CO2 to synthesize organic molecules without solar energy

needs of photoautotrophs

- light energy
- water
- minerals
- CO2

Heterotrophs

- unable to produce their own organic materials
- consumers
- completely dependent on Photoautotrophs

chloroplasts

[photosynthesis]
- the major sites of photosynthesis in green plants
- organelles consisting of photosynthetic pigments, enzymes, and other molecules grouped together in membranes
- found in the cells of the mesophyll
- chlorophyll

chlorophyll

[photosynthesis]
- an important light absorbing pigment in chloroplasts
- responsible for the green color of plants
- plays a central role in converting solar energy to chemical energy
- absorbs light energy and drives the synthesis of organic molecules

mesophyll

[photosynthesis]
- interior tissue of the leaf
- 30-40 in a cell
- stroma
- the place where chloroplasts are found

stroma

[photosynthesis]
- fluid within the chloroplast

stomata

[stoma]
- Pore-like openings in leaves that allow gases (CO2 and O2) and water to diffuse in and out of the leaves
- CO2 enters
- O2 exits

veins

[photosynthesis]
- H2O Roots --> Leaves and SUgar --> Roots/ Other parts (nonphotosynthetic)

photosynthetic equation

[6CO2 + 12H2O + Light Energy --> C6H12O6 + 6O2 + 6 H2O]
- used a heavy isotope of Oxygen
- use isotope to trace Oxygen during the reaction
- Glucose
- 12 H2O consumed, 6 produced

photosynthesis redox process

- photosynthesis, like respiration, is a redox (oxidation/reduction) process
- water molecules are split apart by oxidation
-- they lose electrons along with hydrogen ions
- CO2 is reduced to sugar
-- electrons and hydrogen ions are added to it

energy hill

- in photosynthesis, electrons gain energy when they are pushed up this
- light energy captured by chlorphyll moelcues provides the boost for the electrons
- light energy is converted to chemical energy which is stored in the chemical bonds of sugar molecules
- the sugar produced in photosynthesis is stored for later use or as raw material for biosynthesis of new plant material

light reaction

- linked by ATP and NADPH
-- solar energy --> Chemical energy
--- chlorophyll absorb light
--- water split
--- e-(H+) H2O --> NADP+
---- NADP+ reduced to NADPH (2e- + H+)
---- ADP --> ATP (chemiosmosis)
--- O2 as a byproduct

Calvin Cycle

- often called the dark (or light -independent) reactions
- occurs during daytime in most plant when the light reactions are powering the cycle's sugar assembly line
- carbon fixation
- fixed CO2 reduced (e- added) --> Carbohydrate
-- NADPH reducing power (from light reaction)
- ATP chemical power (from light reaction)

carbon fixation

CO2 from the atmosphere incorporated into existing C compound

light energy

[sunlight]
- both electromagnetic energy and radiation
- travels in rhythmic waves
-- measured in wavelength

visible light

- 380 nm - 750 nm
- detected by human eye
- drives photosynthesis

wavelength

the distance between the crests of two adjacent waves

photons

- light behaves as photons
- particles of light explain light's behavior
- fixed quantity of energy
- energy = 1/wavelength
-- shorter wavelength = greater energy
-- longer wavelength = less energy

photons

discrete packets of energy

pigments/ light receptors

- different pigments absorb light at different wavelengths
- absorbed light disappear
- color seen is reflected or transmitted (spectrophotometer)

spectrophotometer

- also called galvinometer
- device that measures the fraction of light transmitted at a specific wavelength
- absorption spectrum

absorption spectrum

the spectrum of electromagnetic radiation that has passed through a medium that absorbed radiation of certain wavelengths
- different for each pigment
- light absorption vs Wavelength

action spectrum

- the efficiency with which electromagnetic radiation produces a photochemical reaction plotted as a function of the wavelength of the radiation
- resembles absorbtion spectrum

chlorophyll A

[pigment involved in photosynthesis]
absorbance spectrum
-- violet-blue-red = high
-- green = less efficiently
-- blue-green = transmittance

Chlorophyll B

[pigment involved in photosynthesis]
- accesory pigment
- almost identical to Chlorophyll A but has a slight structural difference
- transmittance = yellow-green

Carotenoids

[pigment involved in photosynthesis]
- accessory pigment
- absorb violet and blue-green
- transmit yellow-orange shades
- function mostly in photoprotection
-- antioxidant

photoprotection

- absorbs excess light energy that would damage chlorophyll
- ex. carotenoids

antioxidant

- ex. Carotenoids
- prevents energy from interacting with oxygen to form oxidative molecule

Chlorophyll interaction with light

- color disappears but not energy
- absorbs light photon
- e- elevated to where it has a higher potential energy
-- ground state, excited state
- can absorb only the amount of energy difference in potential energy between ground and excited
- differs between different pigments: why the absorption spectrum differs
- excited (unstable) --> ground; release energy as heat
- isolate chlorophyll also emits light

ground state

- the lowest energy state of an atom
- e- at normal level

excited state

- condition of an atom whose electrons are at higher energy levels than the ones they normally occupy
- e- has higher potential energy

photosystems capture solar power

- the energy released could be lost as heat or light, but rather it is conserved as it is passed from one molecule to another
- all of the components to accomplish this are organized in thylakoid membranes in clusters called photosystems

photosystems

- light harvesting complexes surrounding a reaction center complex (proteins)
- chlorophyll, small organic compounds, proteins
- reaction center surrounded by light harvesting complexes (complex and reaction center)

protein complex

- pigment bound to proteins
- reaction center in photosystems
-- two special chlorophyll A molecules use energy from light to boost 1 e- to an excited state
-- primary e- acceptor

light reactions

- first step: e- (chlorophyll) is excited by the light energy
- as it drops from this unstable state the energy is passed from molecule to molecule within the photosystem
- finally it reaches the reaction center where a primary electron acceptor accepts these electrons consequently becomes reduced
- this solar powered transfer of an electron from the reaction center pigment to the primary electron acceptor is the first step of the light reaction
- redox reaction
- light energy --> chemical energy --> sugar
- isolated chlorophyll give off light because there is no e- acceptor so the e- drops from excited --> ground state

photosystem I and II

- 2 systems in light reactions
- the chylorophyll are identical but their association with other proteins causes their difference in absorbance

PS II

- chlorophyll a P680
- most effective at 680 nm

PS I

- chlorophyll a P700
- most effective at 700 nm

Please allow access to your computer’s microphone to use Voice Recording.

Having trouble? Click here for help.

We can’t access your microphone!

Click the icon above to update your browser permissions above and try again

Example:

Reload the page to try again!

Reload

Press Cmd-0 to reset your zoom

Press Ctrl-0 to reset your zoom

It looks like your browser might be zoomed in or out. Your browser needs to be zoomed to a normal size to record audio.

Please upgrade Flash or install Chrome
to use Voice Recording.

For more help, see our troubleshooting page.

Your microphone is muted

For help fixing this issue, see this FAQ.

Star this term

You can study starred terms together

NEW! Voice Recording

Create Set