Cell Bio Exam #3

Autotrophs

Can make glucose + other molecules from inorganic starting materials (CO2)

Heterotrophs

Make glucose from other organic material

Photosynthesis ( reverse of respiration)

6CO2 + 12H2O + energy(light) → C6H12O6 + 6O2 + 6H2O

• light reactions: dependent on light (produce O2, ATP, and NADPH for carbon reactions)

• carbon reactions: consume ATP + NADPH + CO2 to make sugars

Respiration (reverse of photosynthesis)

glucose + 6O2 + 6H2O → 6CO2 + 12H2O + energy (ATP)

Photosynthesis vs respiration

increase in O2 in atom based on photosynthetic bacteria, these two processes support each other

Chemistry of Photosynthesis

Used 18O (radioactive form)

• exp 1: H2, 18O, CO2 → 18O2 gas

• exp 2: H2O, C18O2 → not labeled

Oxygen comes from water in photosynthesis

Light energy into chemical energy (ATP)

• chloroplasts as site of ATP production, double membrane(outer and inner, both smooth membrane), thylakoid: increases SA - small individual disks, thylakoid membranes: contains ATP synthase + light reaction machinery (chlorophyll), lumen - interior of thylakoid, H+s accymmulate here (IMS of mitochondria), Stroma - exterior of thylakoid (matrix of mito) - pump protons stroma → lumen, ATP is energy source, NADPH is proton source —— (Chemiosmosis)

Properties of Light

V= c/wavelength

wavelength = distance between peaks (nm), c(speed of light) = 3×10^8 m/s, v(frequency) = # of waves passing on observation point per second (s^-1)

Wavelength and freq are inverse of each other, takes longer

Energy

wavelength is inversely proportional to energy, shorter the wavelength, higher the energy

Wavelength of light

gamma rays ( lowest wavelength, 10^-5 nm, high energy) → Radio waves (highest wavelength, 10^12 nm, lower energy)

intermediate wavelength = intermediate energy

visible light = 400-700nm

Photoexcitation

1) low Energy light

2) high Energy light(ejects electron) - transferred to good oxidizes to ETG

3) medium energy light(photon exites e-, decays to original state)

• excites e- making them able to be transferred to be used

Chlorophyll

Ring structure that absorbs photons and balances loss of e-

hydrocarbon tails embedded in thylakoid membrane (carotenoids)

Absorbance Spectrum of Pigments

Assecary pigments that support chlorophyll

Chlorophyll A, B, Caratonids, Rate of photosynthesis measured by O2 production

Start of ETC

e- excites transfers down, pigments captured by Chlorophyll molecule, which is then passed form 1 redox carrier to another

• oxidize chlorophyll molecules

• reduce transporter A → start ETC

Non-cyclic electron flow

how to make ATP with photophosphorylation, energy for proton gradient from light source, pathway has 2 photosystems

light→photosystem II —e—>Q(plastiquinone) → cytochrome p6f complex —> plastocyanain (PC) → Photosystem 1 → ferredoxin (Fd) → Ferredoxin NADP+ reductase complex (FNR) → NADPH

Phtotosystem II

gets excited, has pigment that absorbs photon and excites e-, oxidizes water and produces O2

gets e- back from oxidation of H2O, photosystem I gets them back from the e- traveling down chain from Photosystem II

Q (plastiquinone)

e- carrier

Cytochrome p6f complex

complex 2, accepts e- and pumps protons - reduces PC

Plastocyanin (PC)

mobile e- carrier

Photosystem I

struck by light particle, excites e- again

Ferredoxin (Fd)

mobile e- carrier

Ferredoxin NADP+ reductase complex (FNR)

reduces NADP+ into NADPH

Non-cyclic electron flow infor

ATP disconnected by dependent on proton gradient, and from proton pumping by cytochrome bf6

reverse of oxidative phosphorylation (starts with oxidizing, ends with reducing)

3 consequences of oxidizing H2O

1) taking e- away and giving back to photosystem II, so e- from chlorophyll pigments is replaced by oxidizing H20, H2O is e- source for photosystem II (doesnt deplete continuously from chlorophyll)

2) generates protons (adds to proton gradient)

3) makes oxygen (plants and animals use as e- acceptor in respiration

Notes on non-cyclic electron flow

2 photosystems (PSII and PSI) - associated with chlorophyll/pigment complex

use energy of photon to excite e-s for reduction of ETC carriers

PSII: also oxidizes H2O, produces 1) e- fed back into PSII, 2) proton gradient, 3) O2 for cellular respiration

ETC

PSII → Q → Cyt-b-6-7 complex → PC(plastocyanin) → PSI → Fd → FNR → NADPH

How is suns energy converted into chemical (ATP)

Oxidation of H2O