SBI4U - Chapter 3: Photosynthesis

Porphyrin - Mg atom surrounded by hydrocarbon ring with alternating single and double bonds. The electrons in these bonds absorb light energy and begin the photosynthetic process

Phytol tail - hydrophobic, anchors molecule to membrane

One of the firsdt cells to produce oxygn on a large scale and use sunlight in production of organic compounds from water and carbon dioxide

true

• Waxy
• Protect the leaf from excessive absoprtion of light and evaporation of water

Transparent, colourless

Allows light to pass through mesophyll cells

Spongy and palisade

Photosynthetic cells that form the bulk of a leaf

Bean shaped around stoma

Photosynthetic epidermal cells of a leaf or stem that GUARDS the size of an opening

Microscopic opening

Openings on surface of leaf that allow the exchange of gas

200 L

• Creates transpiration pull that helps move water, minerals, and other substances from roots to leaves
• Produces an evaporative cooling system that prevents leaves from heating to temperatures that could inhibit or denature enzymes that catalyze the reactions of photosynthesis

To maximize CO2 intake and limit water loss, any weather that promotes transpiration like sunny, warm, dry weather, will have guard cells reduce the size of stomata

Open

Closed

When water moves in and out of cell; follows diffusion of potassium ions.

Basically when K moves into guard cells, water follows, and guard cells swell, stoma open

Sun come out, blue light activates blue receptors, making proton pumps pump protons out of cell = gradient

Gradient makes K ions move, making water move, making guard cells swell, makinjg stomata open

Simultaneously, mesophyll cells photosynthesize thus using CO2, making stomata open

Protein rich semiliquid material

Synthesis of photosynthesis

Interconnected flattened membrane sacs

Separate compartment in stroma

Stack of thylakoids

Thylakoid connectors

Contains light-gathering pigment molecules and ETC

• Capture light energy
• Use energy to make ATP and NADPH
• Use free energy of ATP and NADPH to synthesize organic compounds from CO2

Enzymes that catalyze these reactions are activated by light and inactive in dark. Calvin Cycle also requires ATP and NADPH from light reactions

Clusters of photosynthetic pigments embedded in thylakoid membranes of chloroplasts that absorb light energy. 

Absorbed light energy goes in ADP, Pi, and NADP+ to make ATP and NADPH. The H shit is from water

An action spectrum is a graph illustrating effectiveness of wavelengths promoting photosynthesis; which wavelength is good for a specific pigment

An absorption spectrum is a graph illustrating the wavelengths of light absorbed by pigments

• Chlorophyll A is the main bitch absorbing the energy of light to the carbon fixation reactions of photosynthesis, R group is CH3
• Chlorophyll B is a side bitch accessory pigment absorbing things chlorophyll A cant, R group is CHO

• Cartenoids - absorb light that can damage chlorophyll and lose energy as heat, orange
• Xanthophylls - interspersed in thylakoid membranes, yellow
• Anthocyanins - in plant cell vacuoles, not chloroplasts, red, violet, and blue

• Photoexcitation: absorption of a photon by an electron of chlorophyll
• Electron transport: transfer of excited electron thru series of membrane bound electron carriers = gradient = reduces an electron acceptor
• Chemiosmosis: movement of protons through ATPase complexes to drive the phosphorylation of ADP and ATP

Occurs in thylakoid membrane 

Light is absorbed by photosystems -  first by PII then PI

• Antenna complex
• several hundred pigment molecules
• absorb photons and transfers to rxn centre

• Reaction centre
• chlorophyll a molecule - energy trapped in here is sent to ETC

Photon -> pigment -> pigment -> pigment -> chlorophyll a -> energy

Noncyclic electron flow

TWO THINGS HAPPENING: ATP AND NADPH

Excited e for PII moves through primary electron acceptor (pheophytin), e carriers (PQ, b6f, PC) and then ETC to replace an electron lost by photosystem I. This occurs twice

Prior to, Z protein in PII splits water into H and G+ and electrons. One of these electrons are used to replace the missing e in PII. Oxygen is diffused out of cell, leaving protons in thylakoid space. These electrons will pass a proton pump called Q cycle to create an H+ gradient for chemiosmosis to photophosphorylate ADP to ATP. Four H+ per ATP per pair of e

• e in PI is energized by photon
• e goes to ferredoxin -> NADP reductase (to reduce to produce NADPH).

Redox

There is no primary electron acceptor to receive the photoexcited electron, so they are the primary light harvesting unit of the chloroplast

Plastoquinone, b6f-complex, and plastocyanin

Pheophytin

• PI - P700
• PII - P680

Z protein in PII splits water into H and G+ and electrons. One of these electrons are used to replace the missing e in PII

Thylakoid lumen

It is another way to produce energy using only PI. It makes ATP, but not NADPH, so it can be used when NADPH is high

• Photon ejects e from PI 
• e -> Fd erredoxin -> Q cycle -> b6f-complex (cytochrome chain) -> PI

It creates the proton gradient for ATP

True

False, only PI

False; only ATP

True

Cyclic

Noncyclic

let's make some coco in da stroma

dis all bout da CO2

CO2 will be synthesized into carbs using energy from NADPH and ATP.

1) Carbon Fixation

CO2 is being added to 5-carbon molecule RuBP to make a 6-carbon shit, producing two 3-carbon shit (3 PGA). These reactions are catalyzed by rubisco

ya

• STAGE 1: Thylakoid membrane
• STAGE 2: Thylakoid lumen
• STAGE 3: Stroma of chloroplasts

• Carbon fixation
• Reduction Reaction
• RuBP

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