bio 2 2nd exam (PHOTOSYNTHESIS)

Question 1

Photosynthesis

Answer 1

•Photosynthesis is the process that converts solar energy into chemical energy

Question 2

Autotrophs

Answer 2

•Autotrophs sustain themselves without eating anything derived from other organisms

Question 3

photoautotrophs

Answer 3

• photoautotrophs-Almost all plants are photoautotrophs, using the energy of sunlight to make organic molecules from H2O and CO2

Question 4

Chloroplasts

Answer 4

• found in mesophyll-is the interior tissue of the leaf
  
  • mesophyll has 30-40 chloroplasts​
• The chlorophyll is in the membranes of thylakoids (connected sacs in the chloroplast); thylakoids may be stacked in columns called grana
• chloroplasts contain stroma
  
  • in stroma: calvin cycle of Photosys and carbohydrate fermentation occurs
• Photosynthesis takes place in specialized structures inside

plant cells called chloroplasts

takes place in specialized structures inside

plant cells called chloroplasts

Question 5

Chloroplast Pigments

Answer 5

Chloroplast Pigments

• Chlorophyll a
• Chlorophyll b
• Carotenoids (NOT cathinone, NOT bathsalts!)

Question 6

Photosynthesis equation

Answer 6

6 CO2 + 12 H2O + Light energy -> C6H12O6 + 6 O2 + 6 H2O

• H2O is oxidized and CO2 is reduced
• Carbohydrate made is glucose
• 12 H2O molecules are required and 6 new H2O molecules are made
• Water is split as a source of electrons from hydrogen atoms releasing O2 as a byproduct
• Electrons increase potential energy when moved from water to sugar therefore energy is required ******

Question 7

Two Stages of Photosynthesis

Answer 7

1. Photosynthesis consists of:

–light reactions (the photo part)

–Calvin cycle (the synthesis part)

2. The light reactions (in the thylakoids):

–Split H2O

–Relase O2

–Reduce NADP+ to NADPH

–Generate ATP from ADP by photophosphoylation***

Question 8

photophosphorylation

Answer 8

photophosphorylation:

• synthesis of ATP from ADP
• making ATP using proton gradient

Question 9

Overview of Photosynthesis

Answer 9

• light reactions convert solar energy to chemical energy
• Produce ATP & NADPH
• The Calvin cycle makes sugar from carbon dioxide (carbon fixation)
• ATP generated by the light reactions provides the energy for sugar synthesis

Question 10

Photosynthetic Pigments: The Light Receptors

Answer 10

• pigments absord visible light
• different pigments absord differernt wavelengths
• Wavelengths that are not absorbed are reflected or transmitted
• leaves appear green because chlorophyll reflects and transmits green light

Question 11

Absorption spectrum

Answer 11

• Absorption spectrum: graph plotting a pigment’s light absorption versus wavelength.
• In chlorophyll A, violet-blue and red light work best for Photosys​
• Actrion spectrum: profiles the relative effectiveness of different wavelengths of radiation in driving a process

Absorption spectra and action spectrum have the same curvature. Peaks or highs of curve means most useful for PhoSys

Question 12

Chlorophyll A

Answer 12

• Chlorophyll A : main photosynthetic pigment
• accessory pigment such as chlorophyll B broadens which wavelengths are used for PhoSys. (broadens which colors most benificail for phosys)
  *

Question 13

Excitation of Chlorophyll by Light

Answer 13

When pigment absorbs light, it goes from a ground state to excited state=unstable!

• When excited electrons fall back to the ground state, photons are given off = fluorescence
  
  • excited go back to ground state, it releases photons (gives fluorescence)
• If illuminated an isolated solution of chlorophyll will fluoresce, giving off light and hear

Question 14

Excitation of chlorophyll in a chloroplast

Answer 14

• if loss of energy bc of heat makes the photons of light to be less enegetic (loss of energy due to heat, makes protons less energy)
• less energy= longer wavelength
• Energy = (Planck’s constant) x (velocity of light)/(wavelength of light)

(a) Absorption of a photon
(b) fluorescence of isolated chlorophyll in solution

Question 15

PHOTOSYSTEMS

Answer 15

PHOTOSYSTEMS ARE CLUSTERS OF CHLOROPHYLL AND OTHER PIGMENT MOLECULES THAT ABSORB SUNLIGHT FOR PHOTOSYNTHESIS.

Question 16

photosystem consists of

Answer 16

• of Reaction-center complex ( a type of protein complex)
• is surrounded by light-harvesting complexes
  • ​light-harvesting complexes (pigment molecules bound to proteins) funnel energy of photons to reaction center
• A primary electron acceptor: in rxn center accepts excited electron from chlorophyll
• A solar-powerd transfer of electron from chlorophll a molecule to the primary electron acceptor is the first step of light rxns

Question 17

two types of photosystems

Answer 17

• Photosystem 2 (PS II) (1st discovered)- functions first, best at absorbing a wavelength of 680nm
  
  • the rxn-center of chlorophyll a of PS2 is called P680
• Photosystem I (PS I) -best at absorbing wavelength of 700nm
  
  • the rxn-centerchlorophyll a of PS1 is called P700

Question 18

Linear Electron Flow

Answer 18

@light rxns, 2 possible routes for electrons. cyclic and linear.

• Linear electron flow- the primary pathway, involves both photosystems and produces atp and nadph using light energy
• Cyclic electron flow- uses only photosystems I and produces ATP, but not NADPH

Question 19

Cyclic Electron Flow

Answer 19

• Cyclic electron flow uses only photosystem I and produces ATP, but not NADPH
• Cyclic electron flow - makes extra ATP satisfying the big demand in the calcin cycle
• electron goes back into the electron transport chain (moves in and out) IDK ABOUT THIS WHOLE BULLET
• Cyclic electron flow may protect cells from light-induced damage

Question 20

Calvin cycle (makes glyceraldehyde-3-phospate (G3P))

to make 1 G3P, need 3 CO2

3 CO2= 1 G3P

3 phases:

–CARBON FIXATION (Catalyzed by rubisco)

–REDUCTION (synthesis of G3P)

–REGENRATION OF THE CO2 ACCEPTOR (RuBP)

Answer 20

• Calvin cycle uses ATP and NADPH to convert CO2 to sugar
• Calvin cycle, like citric (kreb) cycle, regenerates its starting material after molecules enter and leave the cycle
• The cycle builds sugar from smaller molecules by using ATP and the reducing power of electrons carried by NADPH (PURPOSE OF CALVIN CYCLE)
• carbon goes in cycle as co2 and leaves as sugar: glyceraldehyde-3-phospate (G3P)