Golgi Apparatus

• Golgi bodies or “dictyosomes”• Stacks of cisternae• Secretory function• Cell wall formation

Golgi Apparatus: part of endomembrane system

Cell Wall Deposition: movement of cellulose synthase rosettes is guided by microtubules in the cytoplasm. Problem or error here?

UDP-glucose (uridine diphosphate-glucose; cellulose precursor)

Cellulose microfibrils can’t “jump”; new microfibrils are always depositedBelow previously deposited microfibrils or cell wall layers.

Increased Golgi Activity during division

Progressive Stages of Cell Plate Formation

Cell Wall : 3 Layers

• Middle lamella: – first layer formed during cell division– outermost wall of cell, shared by adjacent cells– Composed of pectins and proteins

• Primary (1°) wall:– formed after mid. lam.– cellulose micrifibrils in a gel-like matrix of pectins, hemicellulose,

proteins• Secondary (2°) wall:

– formed once cell enlargement is complete.– Extremely rigid and strong– Cellulose, hemicellulose, lignin

Primary Cell Wall• All plant cells (?) have a primary cell wall.• Cellulose, pectin, hemicellulose, proteins• All components are hydrophilic to a degree:

form a permeable hydrated matrix

Plasmodesmata

More Cell Wall & Plasmodesmata

Cell Expansion?

• Wall acidification: H+ pumps in cell membrane move H+ into cell wall; disrupts crosslinkages between cellulose, hemicellulose, pectins.

• Expansins : enzymes that can cause cellulose microfibrils to slip.

• Hydrolytic enzymes: cellulase, pectinase, degrade cell wall polymers

Secondary Wall

Photosynthesis

Chlorophylls

Chlorophyll a Chlorophyll b

“Tail”- Unsubstituted chain of

C and H- Hydrophobic (lipid-like)- Anchors chlorophyll in

thylakoid membrane

Chromophore- Light-absorbing portion- Conjugated ring system- Absorption spectrum

modified by substitutions.- Methyl group (chl a)

Carboxyl (chl b) - Absorption spectrum also

altered by nearby molecules/interactions

Chlorophll absorption spectra

• Chlorophylls absorb blue and red wavelengths primarily.

• Chl a maxima: • Chl b maxima:

What we see.

Chlorophyll Masking by Anthocyanins

• Malvidins – anthocyanins that absorb green/yellow wavelengths (+ UV)• Impart blue/red/purple coloration (red wine, cherries, geraniums)

Chlorophyll masking by anthocyanin: a defense for new growth?

- Predators may seek young, bright green leaves (anthocyanins camouflage the leaf).- Other defenses of these young leaves? Felty appearance?- In time, 2° defenses (tannin concentrations, etc.) may develop.Anthocyanins also become important during leaf degreening and fruit ripening

Quercus marilandica (“blackjack oak”) Bastrop, TX.

Degreening and Ripening

Absorption spectrum of Chlorophyll and the Action Spectrum of Photosynthesis

Elgelmann’s Experiment (1882)

Overview of Photosynthesis

Resonance Energy Transfer in Antenna Complex Pigments

Non-cyclic electron flow & phosphorylation

Transfer of e- and H+