Chapter 10 Photosynthesis

Chapter 10 Photosynthesis - Light behaves like a wave...

Info iconThis preview shows pages 1–10. Sign up to view the full content.

View Full Document Right Arrow Icon
Waves and Photons Light behaves like a wave (interference, frequency ν , wavelength λ ), but it comes in packets (photons). It travels at c = 3 x 10 10 cm/sec. Energy = h ν λ= c Ε nergy = hc Higher frequency/shorter wavelength photons of light have more energy.
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Pigments Pigments are molecules that absorb light in the visible spectrum. The wavelength of visible light reaches from 700 nm (red) light through ROYGBIV to 400 nm (violet) light. Ultra violet light, with shorter wavelength and higher frequency , has higher energy . Infra red light, with longer wavelength and lower frequency , has lower energy . Lots of molecules absorb and reflect light in these wavelengths, which is the reason visual systems evolved to sense those wavelengths.
Background image of page 2
Absorption of a photon by a pigment molecule can kick an electron from its ground state to a higher ( excited ) energy state. The pigment can only absorb photons of particular energies, giving it a characteristic “absorption spectrum”. Photo-excitation
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
An excited pigment molecule may lose its energy by fluorescence (emission of a lower energy photon – remember the Second Law), as shown here or by transferring (most but not all of) the energy to another pigment molecule. Energy transfer
Background image of page 4
Photosynthesis Photosynthesis employs two pathways: Light reactions : light energy converted to chemical energy (in ATP and NADPH + H + ) Light-independent reactions : use the ATP and NADPH + H + plus CO 2 to produce sugars
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Photosynthesizing plants take in CO 2 , water, and light energy, producing O 2 and carbohydrate. The overall reaction is the opposite of the breakdown of glucose, which was C 6 H 12 O 6 + 6 O 2 6 CO 2 + 6 H 2 0 + 686 kcal/mol Because water is the source of the oxygen that is produced, the reaction is written as follows: 6 CO 2 + 12 H 2 O + light     C 6 H 12 O 6 + 6 O 2 + 6 H 2 O Only ~4% of the incident light energy ends up in chemical bonds! Photosynthesis
Background image of page 6
Water is the source of O 2 The common isotope of oxygen is 16 O. As a result of work during WWII, biologists obtained 18 O and were able to trace the flow of oxygen atoms, discovering that H 2 O, not CO 2 , was the source of the O 2 given off during photosynthesis.
Background image of page 7

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Stroma Thylakoids Thylakoid Chloroplast The light reaction is driven by light energy captured by chlorophyll. It produces ATP, NADPH + H + , and O 2 . The Calvin–Benson cycle, the light-independent reactions , does not use light directly. It uses ATP, NADPH + H + , and CO 2 to produce sugars. Two linked sets of reactions
Background image of page 8
A chloroplast is enclosed by a double membrane, an outer and an inner. It contains an internal system of thylakoids . Thylakoids within chloroplasts contain the chlorophyll, electron transport chains, and ATP synthase that harvest light energy for photosynthesis. The
Background image of page 9

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 10
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 04/19/2011 for the course LS 2 taught by Professor Pires during the Spring '08 term at UCLA.

Page1 / 44

Chapter 10 Photosynthesis - Light behaves like a wave...

This preview shows document pages 1 - 10. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online