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The synthesis of ATP by chemiosmosis is endergonic and is ..

These compounds are exported to bundle-sheath cells, where they release carbon dioxide for use in the Calvin cycle.

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Light-dependent reactions are the synthesis of ATP ..

Triose phosphates produced by the Calvin cycle inbright sunlight, as we have noted, may be stored temporarilyin the chloroplast as starch, or converted to sucroseand exported to nonphotosynthetic parts of theplant, or both. The balance between the two processesis tightly regulated, and both must be coordinated withthe rate of carbon fixation. Five-sixths of the triosephosphate formed in the Calvin cycle must be recycledto ribulose 1,5-bisphosphate; if more thanone-sixth of the triose phosphate is drawn out of thecycle to make sucrose and starch, the cycle will slow orstop. However, insufficient conversion of triose phosphateto starch or sucrose would tie up phosphate, leavinga chloroplast deficient in Pi, which is also essentialfor operation of the Calvin cycle.
The flow of triose phosphates into sucrose is regulatedby the activity of fructose 1,6-bisphosphatase(FBPase-1) and the enzyme that effectively reverses itsaction, PPi-dependent phosphofructokinase.These enzymes are therefore critical points fordetermining the fate of triose phosphates produced byphotosynthesis. Both enzymes are regulated by fructose2,6-bisphosphate (F2,6BP), which inhibits FBPase-1and stimulates PP-PFK-1. In vascular plants, the concentrationof F2,6BP varies inversely with the rate ofphotosynthesis (Fig. 20–26). Phosphofructokinase-2,responsible for F2,6BP synthesis, is inhibited by dihydroxyacetonephosphate or 3-phosphoglycerate andstimulated by fructose 6-phosphate and Pi. During activephotosynthesis, dihydroxyacetone phosphate isproduced and Pi is consumed, resulting in inhibition ofPFK-2 and lowered concentrations of F2,6BP. This favorsgreater flux of triose phosphate into fructose 6-phosphate formation and sucrose synthesis. With thisregulatory system, sucrose synthesis occurs when thelevel of triose phosphate produced by the Calvin cycleexceeds that needed to maintain the operation of thecycle.
The key regulatory enzyme in starch synthesis isADP-glucose pyrophosphorylase (Fig. 18–14); it isactivated by 3-phosphoglycerate (which accumulatesduring active photosynthesis) and inhibited by Pi (whichaccumulates when light-driven condensation of ADPand Pi slows). When sucrose synthesis slows, 3-phosphoglycerateformed by CO2 fixation accumulates, activatingthis enzyme and stimulating the synthesis ofstarch.

In other words, theirgrowth and division is not linked to the cell cycle.

It is synthesized during photosynthesis and cellular respiration through chemiosmosis, the process that utilizes the proton-motive force generated by the electron transport chain.

Most ATP synthesis in cells occurs by chemiosmosis ..

The endoplasmic reticulum provides a sitefor the synthesis of lipids and proteins and for the storage andtransportof those molecules.

FIGURE 18–2 (a) Amyloplasts filled with starch (dark granules) arestained with iodine in this section of Ranunculus root cells. Starchgranules in various tissues range from 1 to 100 μm in diameter.(b) Plastids: their origins and interconversions. All typesof plastids are bounded by a double membrane, and some (notablythe mature chloroplast) have extensive internal membranes. The internalmembranes can be lost (when a mature chloroplast becomes aproplastid) and resynthesized (as a proplastid gives rise to a pregranalplastid and then a mature chloroplast). Proplastids in nonphotosynthetictissues (such as root) give rise to amyloplasts, which containlarge quantities of starch. All plant cells have plastids, and these organellesare the site of other important processes, including the synthesisof essential amino acids, thiamine, pyridoxal phosphate, flavins,and vitamins A, C, E, and K.

Chloroplast structure
Chloroplast is a plant subcellular organelle where photosynthesis takes place. Outer membrane of chloroplast is permeable. Inner membrane encloses stroma. Thylakoid is flattened membrane surrounded vesicle. This is the place where light reaction occurs. In stroma, fluid surrounding the thylakoids is the place where the dark reaction occurs. Chlorophylls are the green pigments; they are present in the thylakoid membrane of chloroplast. They absorb deep blue and red light. Secondary light absorbing pigments are called accessory pigments. They are carotenoids and phycobilins. Photosystems are the light absorbing pigments of thylakoid membrane arranged in functional sets.

starch synthesis are absent in mesophyll cells.

Photosynthesis usuallyoccurs in parenchyma cells (the mesophyll), and they function in thestorage ofcarbohydrates.

Thus, there is an unequal use of the glycolysis and the citric acid cycle in anaerobic and aerobic respiration.

Welcome to the
Power of the Cell

Created By: Nisha Aggarwal, Sue Kim, and Christie Nakajima
What are 2 main types of anaerobic respiration?
The two main types of anaerobic respiration are
lactic acid fermentation
alcohol fermentation

Citric acid cycle is the aerobic, second major stage in cellular respiration involving eight steps that completes the metabolic breakdown of glucose molecules to carbon dioxide.

Within the inner membrane lies thestroma, which contains thethylakoid membranes - the site of photosynthesis.
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  • By what process do red blood cells produce ATP

    Chloroplast: Chloroplast, structure within the cells of plants and green algae that is the site of photosynthesis.

  • Both processes involve synthesis of ATP


  • Chemiosmotic hypothesis explain the mechanism of ATP synthesis in ..

    Explain how exergonic oxidation of glucose is coupled to endergonic synthesis of ATP; ..

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BioCoach Activity Concept 1: Overview of Respiration

FIGURE 18–13 Sucrose synthesis. Sucrose is synthesized fromUDPglucose and fructose 6-phosphate, which are synthesized from triosephosphates in the plant cell cytosol. The sucrose 6-phosphate synthase of most plantspecies is allosterically regulated by glucose 6-phosphate and Pi.

Plastids - Plant Cell Biology For Masters- by G. R. Kantharaj

Epidermis cells: the dermal tissue of cells of non-woody plants, usually consisting of a single layer of tightly packed cells
Mesophyll cells:
a loosely arranged photosynthetic cell located between the bundle sheath and leaf surface

Vascular tissue:
plant tissue consisting of cells joined into tubes that transport water and nutrients throughout the plant body
Chloroplast: an organelle found only in plants that absorbs sunlight and uses it to drive the synthesis of organic compounds from carbon dioxide and water.
Chlorophyll: a green pigment located within the chloroplasts of plants.
interconnected membranous sacs that segregates the stroma from thylakoid space.

Granum (Grana)
: stacks of thylakoids
Thylakoid membrane:
a flattened membrane sac inside the chloroplast, used to convert light energy to chemical energy
Thylakoid lumen:
thylakoid space; interior of the thylakoid where the proton pumps brings the ions to.
the fluid of the chloroplast surrounding the thylakoid membrane; involve in the synthesis of organic molecules from carbon dioxide and water.
Inside each Chloroplast there are Thylakoids:
Comparison between Light Reactions and the Dark Reactions of Photosynthesis:
Light Reaction:

Occurs on the thylakoid membrane
convert light energy to the chemical energy of ATP and NADPH
Split H20 and release O2 to the atmosphere
Requires water (H20) and solar energy
End products: ATP, NADPH, Oxygen

Dark Reaction (Calvin):

Occurs in the stroma
Use ATP and NADPH to convert CO2 to the sugar G3P
Return ADP and NADP+ to the light reactions
Requires carbon dioxide (C02), ATP, NADPH
End products: NADP+, ADP, G3P (sugar)

What is ATP?

Glossary of Biological Terms ← BACK

Since there is no longer an abundance of chlorophyll to mask the colors of other pigments in the leaves, the yellow and orange shades of accessory pigments like carotenoids are revealed.
Lets Dive a Little Deeper!
When discussing photosynthesis you should first understand the parts of the plant that are involved!
Here is a cross section of a leaf.

Plant Structure & Function - University of Waikato

In cellular respiration, the organic molecules constructed from the three-carbon sugar from photosynthesis are broken down to release energy in the form of ATP, which can then provide energy for cellular processes.

How are Glycolysis and the Citric Acid Cycle used in Respiration?

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