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

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Presentation on theme: "Golgi Apparatus Golgi bodies or “dictyosomes” Stacks of cisternae Secretory function Cell wall formation."— Presentation transcript:

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

2 Golgi Apparatus: part of endomembrane system

3 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 deposited Below previously deposited microfibrils or cell wall layers.

4 Increased Golgi Activity during division

5 Progressive Stages of Cell Plate Formation

6 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

7 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


9 Plasmodesmata

10 More Cell Wall & Plasmodesmata

11 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

12 Secondary Wall

13 Photosynthesis


15 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

16 Chlorophll absorption spectra Chlorophylls absorb blue and red wavelengths primarily. Chl a maxima: Chl b maxima:



19 Chlorophyll Masking by Anthocyanins Malvidins – anthocyanins that absorb green/yellow wavelengths (+ UV) Impart blue/red/purple coloration (red wine, cherries, geraniums)

20 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.

21 Degreening and Ripening

22 Absorption spectrum of Chlorophyll and the Action Spectrum of Photosynthesis

23 Elgelmann’s Experiment (1882)

24 Overview of Photosynthesis

25 Resonance Energy Transfer in Antenna Complex Pigments

26 Non-cyclic electron flow & phosphorylation

27 Transfer of e - and H +


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