Photosynthesis Chapter 8. 2 PHOTOSYNTHESIS Life is powered by the sun. The vast diversity of life on...

Photosynthesis

Chapter 8

2

PHOTOSYNTHESIS

• Life is powered by the sun.

• The vast diversity of life on the Earth is due to about ____________________.

• Comes in different forms, __________

• ____________.

• In plants, photosynthesis takes place primarily in the ________.

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Photosynthesis Overview

Energy for all life on Earth ultimately comes from photosynthesis.

6CO2 + 12H2O C6H12O6 + 6H2O + 6O2

Oxygenic photosynthesis is carried out by:________________________________________________________________

4


Photosynthesis is divided into:light-dependent reactions

-_____________ from sunlight-_________and ______ NADP+ to NADPH

carbon fixation reactions or light independent -use ATP and NADPH to synthesize

_____________________________

6


Photosynthesis takes place in chloroplasts.

thylakoid membrane – ___________

_____________________________

-contain chlorophyll and other pigments

grana – _________________________

stroma – _______________________

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Discovery of Photosynthesis

The work of many scientists led to the discovery of how photosynthesis works.

Jan Baptista van Helmont (1580-1644)-soil does not account for all plant growth

Joseph Priestly (1733-1804)-”living vegetation adds something to the air”

Jan Ingen-Housz (1730-1799)-sun--leaves

F. F. Blackman (1866-1947)-multistage process

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Discovery of Photosynthesis

C. B. van Niel, 1930’s

-proposed a general formula:

CO2+H2A + light energy CH2O + H2O + 2A

where H2A________________________

-van Niel identified ______ as the source of the O2 released from photosynthesis

-Robin Hill confirmed van Niel’s proposal that energy from the light reactions ________

__________________________________

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pigments

• For plants to utilize energy of sunlight they must contain _____________________

• _______________________________

• Use the wavelengths from the_______

• _________________

• Color we see with our retinas is ______

• ______________________________-

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Review of light

• Electromagnetic spectrum is based on_______________

• Wave =_________

• Photons are based on________

• _______= energy transfers that occur during photosynthesis

• Light can remove electrons from molecules

• _________________________________

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Pigments

photon: a particle of light

-acts as a________________________

-energy content of a photon is ________

__________________________________________________________________

photoelectric effect: removal of an electron from a molecule by light

-______________________________

_____________________________________

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Pigments

Pigments: _________________

___________________________________Each pigment has a characteristic absorption spectrum, the range and efficiency of photons_______________

__________________________________

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Photoelectric photons

• Transfer energy to electrons

• In chloroplasts

• Trap energy

• Synthesize into an organic molecule

• P. 148

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Pigments

chlorophyll a –_______________in plants and cyanobacteria

-absorbs _________and _______light

500-600- we____________________

chlorophyll b – secondary pigment absorbing light wavelengths that___________________________

_______________________________

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Pigments

Structure of pigments:

porphyrin ring: complex ring structure with alternating_____________________

-magnesium ion at the ________of the ring

-photons _____________in the ring

-electrons are ____________from the ring

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Pigments

accessory pigments: secondary pigments absorbing light wavelengths_______

_______________________________

-increase the ________________ that can be used in photosynthesis

-include:______________________

___________________________

-carotenoids also________________

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Photosystem Organization

A photosystem consists of

1. an antenna complex of hundreds of

____________________________

2. a reaction center of__________

____________________________________

Energy of electrons is transferred through the antenna complex to the ____________.

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Photosystem Organization

At the reaction center, the energy from the antenna complex is transferred to

_____________________.

This energy causes an electron from chlorophyll to ________________.

The excited electron is transferred from chlorophyll a to an _______________.

__________donates an electron to chlorophyll a to replace the excited electron.

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Light-Dependent Reactions

Light-dependent reactions occur in 4 stages:1. ____________– a photon of light is

captured by a pigment molecule2. ______________ – energy is transferred

to the reaction center; an excited electron is transferred to an acceptor molecule

3. ______________ – electrons move through carriers in photosynthetic membranes. Photons move across creating a photon gradient to reduce NADP+ to NADPH/final receptor.

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cont

• Steps 1-3 capture energy from light

• 4.______________ – photons flow back across membrane through the ATP synthase

• Produces________

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In _____________, only one photosystem is used for cyclic photophosphorylation

1. an electron joins a proton to produce

__________________

2. an electron is ___________ to chlorophyll

-this process drives the chemiosmotic synthesis of ATP

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_____________, two linked photosystems are used in noncyclic photophosphorylation

1. photosystem I

-reaction center pigment (P700) with a peak absorption at 700nm

2. photosystem II

-reaction center pigment (P680) has a peak absorption at 680nm

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Photosystem II acts first:

-accessory pigments _____________ to the P680 reaction center

-__________________from P680 are transferred to b6-f complex

-electron lost from P680 is replaced by an electron _______________________

________________________________

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The b6-f complex is a series of ________

_________________.

-electron carrier molecules are embedded in the ______________________

-protons are pumped into the thylakoid ____

__________________________________

__________________________________

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Photosystem I

-receives energy from an antenna complex

-energy is shuttled to P700 reaction center

-excited electron is transferred to a membrane-bound electron carrier

-electrons are used to reduce NADP+ to NADPH

-electrons lost from P700 are replaced from the b6-f complex

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ATP is produced via chemiosmosis.

- ATP synthase is embedded in the thylakoid membrane

-protons have accumulated in the thylakoid space

-protons move into the stroma only through ATP synthase

-ATP is produced from ADP + Pi

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• 1.5 ATP needed to produce organic molecule

• Plants" short circuit” photosystem I

• Cyclic photophosphorylation can occur

• Relative proportions of cycles = relative amounts of ATP and NADPH

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Carbon Fixation Reactions

To build carbohydrates, cells need:1. energy

-______________________________2. reduction potential

-_____________ from photosystem I -source of _____________________ -energy rich _____________ of sugar

result

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Calvin cycle (C3 photosynthesis)

-biochemical pathway that allows for ______

_________________

-occurs in the ___________

-uses ATP and NADPH as ___________

-incorporates CO2 into ________________

__________________________________

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carbon fixation – the incorporation of ____

________________________________________-occurs in the _____step of the___________

ribulose-bis-phosphate + CO2 2(PGA)

The reaction is catalyzed by rubisco.

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The Calvin cycle has 3 phases:

1.

RuBP + CO2 2 molecules PGA

2.

PGA is reduced to G3P

3.

G3P is used to regenerate RuBP

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________ is not a direct product of the Calvin cycle.

-______________of G3P leave the cycle-each G3P contains______________-_________ are used to produce _______in reactions in the ___________-It takes _________of the cycle

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During the Calvin cycle, energy is needed. The energy is supplied from:

- ___________molecules

- ___________ molecules

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The energy cycle:

-_____________ uses the products of respiration as starting substrates

-_____________ uses the products of photosynthesis as starting substrates

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Photorespiration

Rubisco has 2 enzymatic activities:

1. _____________– the addition of CO2 to RuBP

-favored under_______________

2. photorespiration – the oxidation of RuBP __________________________ -favored in __________________

CO2 and O2 compete for the___________

__________________________________

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Photorespiration

Some plants can avoid photorespiration by

__________________________________.

-PEP carboxylase

-CO2 __________to phosphoenolpyruvate (PEP)

-_____________________is produced

-CO2 is later released from this 4-carbon compound and used by rubisco______

_________________________________

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Photorespiration

C4 plants

-use ______________to capture CO2

-CO2 is added to PEP in one cell type (_______________)

-the resulting 4-carbon compound is moved into ___________________where the CO2 is________________________________

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Photorespiration

CAM plants

-CO2 is captured ___________________

___________________________________ -PEP carboxylase adds CO2 to PEP to produce a_______________________

-this compound releases CO2__________________

-CO2 is then used by rubisco in the______

_______________________________

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How cells divide

• Bacterial cell division

• Clonal – each replicated cell is identical to parent cell

• Prokaryotes-can exchange genetic material but no sexual cycle

• Eukaryotes- sexual cycle

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Binary Fission

• Nucleoid –single, circular DNA molecule

• Replication partitioning of the chromosome occurs as a concerted effort

• Figure 10.1 p. 186

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Separation process

• Septation occurs at the midpoint of the cell

• Growth of the new membrane and production of the septum

• Protein FtsZ ancient form of tubulin and actin

• Figure 10.3 p. 187

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Eukaryotic Chromosomes

• Walther Flemming – 1879 – saw spindle fibers – mitosis

• Chromosome # varies among species

• Most between 10-50 ( humans have 23 almost identical pairs)

• Monosomy- one chromosome

• Trisomy – three chromosomes

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Eukaryotic Chromosomes

• Chromatin- chromosomal composition of 60%protein and 40% DNA

• One long double strand (human 140 million nucleotides)

• Histone proteins – act like magnetic forms that promote and guide the coiling of DNA

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Chromosome structure

• Nucleosome – DNA/ Histone complex

• Figure 10.5 p. 189

• Karyotype – particular array of chromosomes each individual possesses

• Know figure 10.7 structures

61

Chromosome number

• Haploid – one complete set

• Diploid – 2n normal number in humans – two sets

• Maternal and paternal chromosomes – homologous (homologue)

62

Chromosome replication

• Sister chromatids -

Photosynthesis Chapter 8. 2 PHOTOSYNTHESIS Life is powered by the sun. The vast diversity of life on...

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