bio chapter 9

what is the first step in the flow of energy through most of the living world?

photosynthesis

what is converted into the stored chemical energy of organic molecules?

light energy

what is the electromagnetic spectrum from low energy levels to high energy levels

• radio

• microwaves

• infrared

• visible

• UV

• X-rays

• gamma rays

if something has a longer wavelength, what is likely the color given off? what about for shorter wavelength?

• longer- red, orange

• shorter- violet, blue

which color of light has the highest energy? what about lowest energy?

• highest- violet

• lowest- red

define photons

• light is composed of small particles, or packets, of energy called photons

the energy of a photon in -1- proportional to it’s wavelength

1. inversely

when a molecule absorbs a photon of light energy, one of its electrons becomes energized. what are the two possibilities?

1. the atom returns to its lower-energy state and energy dissipates as heat or fluoresces

OR

2. the energized electron leaves the atom and is accepted by an electron acceptor (redox)

chloroplasts are found in -?- cells of leaves

• mesophyll

what is the stomata used for?

• gas exchange

xylem and phloem in the veins are used for what?

• transport water and sugary sap (sugars)

what is the third membrane system in the chloroplast? what does it enclose? what are the stacks called? what does it contain? what type of reaction is it home to?

• thylakoids

• encloses thylakoid lumen

• thylakoid sacs are arranged in stacks called grana

• contains chlorophyll in the membrane home to the light reactions

what is the stroma? what is it parallel to? what does it contain? home to what cycle?

• stroma is the fluid

• parallel to the matrix in the mitochondrion

• has DNA and 70 ribosomes

• home to the calvin-benson cycle

define chlorophyll. do thylakoid membranes contain chlorophyll?

• a pigment that reflects green light and absorbs other wavelengths

• yes, thylakoid membranes contain chlorophyll

in the thylakoid, what side chain holds the molecule?

• the hydrocarbon side chain

what is the main photosynthetic pigment?

• chlorophyll

differentiate chlorophyll A vs. chlorophyll B

• chlorophyll A initiates the light-dependent reactions of photosynthesis

• chlorophyll B is an accessory pigment that also participates in photosynthesis

what are carotenoids? how do they relate to wavelengths?

• yellow and orange accessory photosynthetic pigments

• absorb different wavelengths of light than chlorophyll

• allows more wavelengths to be used

absorption vs. action spectrums

• absorption- shows each pigment that a plant can absorb

• action- same trend as absorption, shows photosynthesis activity. goes hand-in-hand with absorption

photosynthesis equation

• 6CO2 + 6H2O → C6H12O6 + 6O2

multiple redox reactions occur in photosynthesis. what two phases does it divide into?

1. light-dependent reactions- photo part of photosynthesis (capture solar energy)

2. Carbon fixation reactions- synthesis part of photosynthesis (use energy to build sugars)

true or false; photosynthesis is an oxidation-reduction reaction

true

describe the photosynthesis equation (6CO2 + 6H2O → C6H12O6 + 6O2)

• energy from sun is used to convert CO2 to complex carbon compounds

• oxygen atoms in H2O are in a reduced state, they are oxidized to O2

• carbon atoms are in the oxidized state in CO2, they are reduced to carbohydrate (needs water, produces oxygen)

water is the donor of protons and electrons in…

• oxygenic photosynthesis (w/o oxygen being produced)

two pathways occur in different parts of the chloroplast. what are they? describe them

1. light reactions- convert light energy to chemical energy as ATP and NADPH in the thylakoid (requires light and water, releases molecular oxygen)

2. light-independent (dark) reactions- use ATP and NADPH (from the light reactions) plus CO2 to produce carbohydrates in the stroma

which part would run in the dark? light-dependent or carbon fixation reaction?

• nothing, neither one

light-dependent reactions convert what to what in the thylakoids.

begin as soon as chlorophyll captures what?

• convert light energy to chemical energy

• light energy

in light-dependent reactions, energized electrons moves down -1-, creating -2-?

1. electron transport chain

2. creating a proton (H+) gradient

in light-dependent reactions, what is the proton (H+) gradient used to make?

NADP+ is reduced to what?

• ATP

• reduced to NADPH

in the photo system structure, light energy is captured in the -1- complexes and transferred to the -2-

1. light harvesting

2. reaction centers

in the photo system structure, accessory pigments absorb light in other wavelengths, what can this do?

• increases the range of light that can be used

• types of accessory pigments characterize different groups

two types of photosynthetic units are involved in photosynthesis, what are these types and describe.

which one goes first?

• photosystem I (P700)- consists of two chlorophyll A molecules with an absorbtion peak at 700 nm

• photosystem II (P680)- consists of two chlorophyll A molecules with an absorption peak of 680 nm

• PHOTOSYSTEM II GOES FIRST

noncyclic electron transport uses two photosystems, describe this process

1. when a pigment molecule absorbs a photon, the excited state is unstable, and the energy is quickly released

2. the energy is absorbed by other pigment molecules and passed to chlorophyll A in a reaction center

• noncyclic electron transport produces what two things?

• in the presence of light, there is a continuous, one-way flow of electrons from what to what?

1. ATP and NADPH

2. H2O to NADP+

in noncyclic electron transport, describe the electrons in photosystem II

• photosystem II- electron from P680 is replaced by photolysis of water; oxygen is released.

• electrons move down ETC from PS II to PS I.

• energy of a proton gradient generated by the WTC is used to produce ATP by chemiosmosis

in noncyclic electron transport, describe the electrons in photosystem I

• the electron missing from P700 is replaced by one donated by photosystem II

• NADP+ is reduced to NADPH

what does cyclic electron transport produce? what photosystem is involved in this? what is the cyclic electron transport?

• ATP ONLY

• ONLY photosystem I

• energized electrons from P700 return to P700

in cyclic electron transport, electrons flow continuously through what? describe CET

• flow continuously through the ETC

• energy of the proton gradient is used to produce ATP by chemiosmosis, but NADPH is NOT produced, H2O is NOT split, and oxygen is NOT generated

ATP synthesis by chemiosmosis. describe photophosphorylation

• ATP is made by chemiosmosis triggered by light.

• energy from electrons passing through ETC is used to pump protons from stroma into the thylakoid lumen, forming a proton gradient across the thylakoid membrane.

protons diffuse from thylakoid lumen to the stroma, through channels formed by what? describe

• ATP synthase

• ATP synthase catalyzes the photophosphorylation of ADP to ATP

intro to carbon fixation reactions.

1. CO2 fixation:

2. occurs in what, describe

3. goes by many names, like what? what is most common?

1. CO2 is reduced to carbohydrates

2. occurs in the stroma, requires energy in the form of NADPH and ATP

3. names: dark reaction, light independent reactions, calvin cycle/ calvin-benson cycle

4. light independent is most common

the calvin cycle uses energy to produce what and is stimulated by what?

• uses energy to produce carbs

• is stimulated by light

describe the steps of the calvin cycle

1. CO2 uptake (CO2 is converted to 3PG/PGA)

2. carbon reduction (PGA reduced to G3P)

3. regeneration of RuBP, the CO2 acceptor

1. for every turn of the calvin cycle, how many CO2 is fixed and how many RuBP is regenerated

2. every 6 turns of the calvin cycle= C to make how many glucose?

1. 1 CO2 and 1 RuBP

2. C to make 1 glucose

1. in CO2 uptake, CO2 reacts with what?

2. it is catalyzed by what?

3. the unstable 6-carbon product breaks down into two molecules of what

1. reacts with 5-carbon ribulose biphosphate (RuBP)

2. catalyzed by ribulose biphosphate catboxylase/oxygenase (rubisco)

3. 3-carbon phosphoglycerate (PGA)

in carbon reduction, energy from -1- and -2- are used to convert the -3- molecules to -4-

1. ATP

2. NADPH

3. PGA

4. glyceraldehyde-3-phosphate (G3P)

in carbon reduction, reaction of two molecules of -1- leads to the formation of a -2- (after photosynthesis)

1. G3P ← all sugars are made of this

2. glucose or fructose

in RuBP regeneration, -1- molecules (-2-) remain in the calvin cycle

through a series of 10 reactions, these molecules are rearranged into -3-

1. 10 G3P

2. 30 carbons

3. 6 molecules of ribulose phosphate

in RuBP regeneration, Ribulose phosphate is phosphorylated by -1- to produce -2-, which is used to restart the cycle

1. ATP

2. RuBP

what is the importance of glyceraldehyde 3-phosphate (G3P)

2 THINGS TO KNOW

• it is the product of the carbon cycle

• 2 G3P= 1 glucose

1. 3 carbon sugar

2. building block

what doe plants with G3P do to make carbs?

1. some G3P is exported to the cytosol (converted to glucose and fructose and USED IN RESPIRATION)

2. exists may be converted to sucrose (used for energy or to build other molecules)

3. some G3P is used to synthesize glucose and starch within the chloroplast (stored starch is used best at night for plants energy

can photosynthesis and respiration happen simultaneously? why or why not?

• yes, they are closely linked through the calvin cycle

1. some G3P enters what?

2. some G3P goes to what for cellular respiration

1. enters glyconeogenesis (where sugars are formed/ builds glucose)

2. cytosol

review of the calvin cycle:

1. what is required (input)

2. what is produced (output)

3. where does this occur

4. what is the equation

1. CO2, ATP, NADPH

2. G3P, RuBP

3. chloroplast, specifically the stroma

4. 6CO2 + 6H2O → C6H12O6 + 6O2

metabolic diversity:

1. the prefixes tell us the energy source.

• photo=

• chemo=

2. the suffix tells us if they can fix carbon/ what carbon source they require.

• auto (do itself/builds)=

• hetero (needs to take in molecules from other places)=

1. photo= light; chemo= chemical

2. auto= can convert CO2 into other molecules; hetero=needs carbon in an organic form

1. what are photoautotrophs?

2. what do they do?

3. what are they found in?

1. use energy from light source (light energy) to make ATP and NADPH

2. synthesize complex organic compounds from simpler, inorganic raw materials

3. plants and algae

1. what are chemoheterotrophs?

2. what do they do?

3. what are they found in?

1. obtain energy from chemicals by redox reactions

2. use organic molecules produced by other organisms as to synthesize the carbon compounds they need (basically eating or absorption of materials)

3. fungi and animals

1. what are photoheterotrophs?

2. what do they do?

3. examples?

1. use light energy, but do not carry out carbon fixation

2. obtain carbon from organic compounds

3. ex. purple non-sulfur bacteria

1. what are chemoautotrophs?

2. what do they do?

3. examples?

1. obtain energy from oxidation of reduced inorganic molecules: hydrogen sulfide (H2S), nitrite (NO2-), or ammonia (NH3)

2. use captured energy to carry out carbon fixation

3. iron-oxidizing bacteria and nitrogen-fixing bacteria

• photosynthesis and life on earth

• -1- produce virtually all organic molecules used as energy and carbon sources by -2-

• remove -3- from the atmosphere

• photolysis of water releases -4- required by all aerobic organisms for aerobic respiration

• -5- converted to -6- in the stratosphere shields the planet from damaging UV light

1. photoautotrophs

2. chemoheterotrophs

3. CO2

4. O2

5. O2

6. O3

why should we care about photosynthesis?

1. products of the calvin cycle are crucial to the entire biosphere

2. the covalent bonds generated by the cycle provide almost all the energy for life