| Botany |

Plant Biochemistry

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Plant Biochemistry

| Botany |

Plant Biochemistry



A leaf cell consists of several metabolic compartments


A leaf cell consists of several metabolic compartments
The cell wall gives the plant cell mechanical stability
Vacuoles have multiple functions
Plastids have evolved from cyanobacteria
Mitochondria also result from endosymbionts
Peroxisomes are the site of reactions in which toxic intermediates are formed
The endoplasmic reticulum and golgi apparatus form a network for the distribution of biosynthesis products
Functionally intact cell organelles can be isolated from plant cells
Various transport processes facilitate the exchange of metabolites between different compartments
Translocators catalyze the specific transport of metabolic substrates and products
Ion channels have a very high transport capacity
Porins consist of ?-sheet structures

The use of energy from sunlight by photosynthesis is the basis of life on earth


The use of energy from sunlight by photosynthesis is the basis of life on earth
How did photosynthesis start?
Pigments capture energy from sunlight
The energy content of light depends on its wavelength
Chlorophyll is the main photosynthetic pigment
Light absorption excites the chlorophyll molecule
An antenna is required to capture light
How is the excitation energy of the photons captured in the antennae and transferred to the reaction centers?
The function of an antenna is illustrated by the antenna of photosystem II
Phycobilisomes enable cyanobacteria and red algae to carry out photosynthesis even in dim light

Photosynthesis is an electron transport process


The photosynthetic machinery is constructed from modules
A reductant and an oxidant are formed during photosynthesis
The basic structure of a photosynthetic reaction center has been resolved by X-ray structure analysis
How does a reaction center function?
Two photosynthetic reaction centers are arranged in tandem in photosynthesis of algae and plants
Water is split by photosystem II
The cytochrome-b6/f complex mediates electron transport between photosystem II and photosystem I
Photosystem I reduces NADP
In the absence of other acceptors electrons can be transferred from photosystem I to oxygen
Regulatory processes control the distribution of the captured photons between the two photosystems

ATP is generated by photosynthesis


A proton gradient serves as an energy-rich intermediate state during ATP synthesis
The electron chemical proton gradient can be dissipated by uncouplers to heat
H -ATP synthases from bacteria, chloroplasts, and mitochondria have a common basic structure
The synthesis of ATP is effected by a conformation change of the protein

Mitochondria are the power station of the cell


Biological oxidation is preceded by a degradation of substrates to form bound hydrogen and CO2
Mitochondria are the sites of cell respiration
Degradation of substrates applicable for biological oxidation takes place in the matrix compartment
How much energy can be gained by the oxidation of NADH?
The mitochondrial respiratory chain shares common features with the photosynthetic electron transport chain
Electron transport of the respiratory chain is coupled to the synthesis of ATP via proton transport
Plant mitochondria have special metabolic functions
Compartmentation of mitochondrial metabolism requires specific membrane translocators

The Calvin cycle catalyzes photosynthetic CO2 assimilation


CO2 assimilation proceeds via the dark reaction of photosynthesis
Ribulose bisphosphate carboxylase catalyzes the fixation of CO2
The reduction of 3-phosphoglycerate yields triose phosphate
Ribulose bisphosphate is regenerated from triose phosphate
Besides the reductive pentose phosphate pathway there is also an oxidative pentose phosphate pathway
Reductive and oxidative pentose phosphate pathways are regulated

Phosphoglycolate formed by the oxygenase activity of RubisCO is recycled in the photorespiratory pathway

Polysaccharides are storage and transport forms of carbohydrates produced by photosynthesis


Starch is synthesized via ADP-glucose
Degradation of starch proceeds in two different ways
Surplus of photosynthesis products can be stored temporarily in chloroplasts as starch
Sucrose synthesis takes place in the cytosol
The utilization of the photosynthesis product triose phosphate is strictly regulated
In some plants assimilates from the leaves are exported as sugar alcohols or oligosaccharides of the raffinose family
Fructans are deposited as storage compounds in the vacuole
Cellulose is synthesized by enzymes located in the plasma membrane

Nitrate assimilation is essential for the synthesis of organic matter


Nitrate assimilation is essential for the synthesis of organic matter
The reduction of nitrate to NH3 proceeds in two reactions
Nitrate assimilation also takes place in the roots
Nitrate assimilation is strictly controlled
The end product of nitrate assimilation is a whole spectrum of amino acids
Glutamate is the precursor for chlorophylls and cytochromes

Nitrogen fixation enables plants to use the nitrogen of the air for growth


Nitrogen fixation enables plants to use the nitrogen of the air for growth
Legumes form a symbiosis with nodule-inducing bacteria
N2 fixation can proceed only at very low oxygen concentrations
The energy costs for utilizing N2 as a nitrogen source are much higher than for the utilization of NO3-
Plants improve their nutrition by symbiosis with fungi
Root nodule symbioses may have evolved from a pre-existing pathway for the formation of arbuscular mycorrhiza

Sulfate assimilation enables the synthesis of sulfur containing compounds


Sulfate assimilation enables the synthesis of sulfur containing compounds
Sulfate assimilation proceeds primarily by photosynthesis
Glutathione serves the cell as an antioxidant and is an agent for the detoxification of pollutants
Methionine is synthesized from cysteine
Excessive concentrations of sulfur dioxide in the air are toxic for plants

Phloem transport distributes photoassimilates to the various sites of consumption and storage


Phloem transport distributes photoassimilates to the various sites of consumption and storage
There are two modes of phloem loading
Phloem transport proceeds by mass flow
Sink tissues are supplied by phloem unloading

Products of nitrate assimilation are deposited in plants as storage proteins

Phloem transport distributes photoassimilates to the various sites of consumption and storage


Globulins are the most abundant storage proteins
Prolamins are formed as storage proteins in grasses
2S-Proteins are present in seeds of dicot plants
Special proteins protect seeds from being eaten by animals
Synthesis of the storage proteins occurs at the rough endoplasmic reticulum
Proteinases mobilize the amino acids deposited in storage proteins

Lipids are membrane constituents and function as carbon stores


Lipids are membrane constituents and function as carbon stores
Polar lipids are important membrane constituents
Triacylglycerols are storage compounds
The de novo synthesis of fatty acids takes place in the plastids
Glycerol 3-phosphate is a precursor for the synthesis of glycerolipids
Triacylglycerols are synthesized in the membranes of the endoplasmatic reticulum
Storage lipids are mobilized for the production of carbohydrates in the glyoxysomes during seed germination
Lipoxygenase is involved in the synthesis of oxylipins, which are defense and signal compounds

Secondary metabolites fulfill specific ecological functions in plants


Secondary metabolites often protect plants from pathogenic microorganisms and herbivores
Alkaloids comprise a variety of heterocyclic secondary metabolites
Some plants emit prussic acid when wounded by animals
Some wounded plants emit volatile mustard oils
Plants protect themselves by tricking herbivores with false amino acids

A large diversity of isoprenoids has multiple functions in plant metabolism


A large diversity of isoprenoids has multiple functions in plant metabolism
Higher plants have two different synthesis pathways for isoprenoids
Prenyl transferases catalyze the association of isoprene units
Some plants emit isoprenes into the air
Many aromatic compounds derive from geranyl pyrophosphate
Farnesyl pyrophosphate is the precursor for the synthesis of sesquiterpenes
Geranylgeranyl pyrophosphate is the precursor for defense compounds, phytohormones, and carotenoids
A Prenyl chain renders compounds lipid-soluble
The regulation of isoprenoid synthesis
Isoprenoids are very stable and persistent substances

Phenylpropanoids comprise a multitude of plant secondary metabolites and cell wall components


Phenylpropanoids comprise a multitude of plant secondary metabolites and cell wall components
Phenylalanine ammonia lyase catalyzes the initial reaction of phenylpropanoid metabolism
Monooxygenases are involved in the synthesis of phenols
Phenylpropanoid compounds polymerize to macromolecules
The synthesis of flavonoids and stilbenes requires a second aromatic ring derived from acetate residues
Flavonoids have multiple functions in plants
Anthocyanins are flower pigments and protect plants against excessive light
Tannins bind tightly to proteins and therefore have defense functions

Multiple signals regulate the growth and development of plant organs


Multiple signals regulate the growth and development of plant organs and enable their adaptation to environmental conditions
Signal transduction chains known from animal metabolism also function in plants
Phytohormones contain a variety of very different compounds
Auxin stimulates shoot elongation growth
Gibberellins regulate stem elongation
Cytokinins stimulate cell division
Abscisic acid controls the water balance of the plant
Ethylene makes fruit ripen
Plants also contain steroid and peptide hormones
Defense reactions are triggered by the interplay of several signals
Light sensors regulate growth and development of plants

A plant cell has three different genomes


A plant cell has three different genomes
In the nucleus the genetic information is divided among several chromosomes
The DNA of the nuclear genome is transcribed by three specialized RNA polymerases
DNA polymorphism yields genetic markers for plant breeding
Transposable DNA elements roam through the genome
Viruses are present in most plant cells
Plastids possess a circular genome
The mitochondrial genome of plants varies largely in its size

Protein biosynthesis occurs in three different locations of a cell


Protein biosynthesis occurs in three different locations of a cell
Protein synthesis is catalyzed by ribosomes
Proteins attain their three-dimensional structure by controlled folding
Nuclear encoded proteins are distributed throughout various cell compartments
Proteins are degraded by proteasomes in a strictly controlled manner

Biotechnology alters plants to meet requirements of agriculture nutrition and industry


Biotechnology alters plants to meet requirements of agriculture, nutrition and industry
A gene is isolated
Agrobacteria can transform plant cells
Ti-Plasmids are used as transformation vectors
Selected promoters enable the defined expression of a foreign gene
Genes can be turned off via plant transformation
Plant genetic engineering can be used for many different purposes



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