Anatomy
Study of the body´s structure including -Cytology: study of cells -Histology: tissue -Organography: organs
Main compounds of plant and animal life
-water (5-95%) -carbon C (45%) -hydrogen H (8%) -oxygen O (40%)
Most important classes of organic molecules in plant cells
-saccharides (like glucose) -amino acids (like histidine) -nucleic bases (like thymine) -lipids (like fatty acids)
Character and function of organic molecules in polymers
-structural material (cellulose, lignin) -chemical protective cover (cutin, suberin) -information storage (nucleic acids) -energy storage (starch) -biocatalyst (accelerates specific reactions)
Lipids
-fat / fatlike substances -main compounds: H, C, little O -apolar -lipophilic -don´t build macromolecules
fatty acids
-simplest lipids -satured fatty acids: single bonds (C - C) -unsaturated fatty acids: also have double bonds (C = C) -fat: solid at normal temperature -oil: liquid
important fats for energy storage
-> triglycerides (like glycerol): 3C, 3OH-groups, with 3 fatty acids
Phosporlipids
-membrane lipids like glycerol with two fatty acid tails -third bond on the glycerol is occupied by a water-soluble (hydrophilic) phosphate-head -varius small molecules can also be attached to the phosphate -embedded in and attached to the lipid bilayer are proteins with various functions ->can easily move sideways but can´t switch from one side to the other
Proteins
-polymers, composed of 20 different amino acids -medium to large-sized molecules -can be extremely variable -depending on their amino acids, some are lipophilic (phenylalanine), others are hydrophilic (glutamate) -essential amino acids in our nutrition
protein structure
-primary protein structure: sequence of a chain of amino acids -secondary protein structure: local folding of the polypeptide chain into helices or sheets -tertiary protein structure: three-dimensional folding pattern of a protein due to side chain interactions -quanternary protein structure: protein consisting of more than one amino acid chain
Enzymes
-biocatalysts composed of special proteins (often with non-protein parts) -reduce required activation energy, accelerate reactions example: the enzyme invertase bonds with the sugar sucrose ->is split to glucose and fructose, these seperate from the enzyme, wich remains unchanged
membrane transport
-mostly regulated through special membrane proteins -membranes: selectively permeable -membrane transport, biochemical synthesis, destruction control which substance is available where and in which quantity
diffusion
through the random movement of particles, the concentration eventually becomes homogeneous -much faster in gases than in water -in water mostly fast enough for small distances (like inside cells), not for transports over long distances
osmosis
the cell membrane prevents passage of the dissolved substance, but water can easily pass ->in this case the concentration can become uniform if water flows through a semi-permeable membrane towards the higher concentration ->increases its volume and can produce pressure ->pressure equals the difference in concentration ->the osmotic potential characterizes a solution with the ability to absorb water or create pressure
trugor
= if the concentration inside the cell membrane is higher than outside (in the cell wall) ->water is absorbed osmotically, volume increases and puts pressure on the cell wall ->causes counter pressure of the elastic cell wall water potential of the cell = hydrostatic pressure - osmotic pressure
nucleus
-eukaryotes = organisms with a nucleus, mostly have 1 nucleus per cell where most DNA and thus information is stored
DNA - desoxyribonucleic acid
-carrier of genetic information -information is coded by the order of the nucleotides adenine (A) - thymine (T), cytosine (C) - guanine (G) -always identical pairing of the 4 bases guarantee consistent information -each strand carries the full information to build the second (mirrored) strand
DNA-replication
Topoisomerase: uncoils the DNA Helicase: splits the double-strand into single strands DNA-polymerases: complete the single strands - always from the 5´ to the 3´-end replication "in the opposite direction" works in pieces (Okazaki-fragments) that need to be joined by DNA-ligase
DNA-chromosomes
= DNA, normally bound to proteins -can be stained (colored) hence the name -chromosomes = strongly condensed chromatin, become visible under a light microscope DNA + proteins = chromatin; nucleosomes (DNA-strand wrapped around histone-proteins)
transcription
DNA´s information is copied into RNA DNA´s package in the chromatin-thread is locally loosened ->the coding strand is into a mRNA by the enzyme RNA-polymerase RNA: ribonucleic acid (with the sugar ribose instead of desoxyribose; with the base uracil instead of thymine in the single strand)
genetic code
combinations of three nucleotides (triplets) from the RNA, so called codons, code the 20 amino acids that can be found in proteins codons UAA, UAG, UGA do not code amino acids, but indicate the end changes in the base sequence can cause changes in the amino acids, but not every mutation of single bases results in a different amino acid
translation
process, in which ribosomes in the cytoplasm / endoplasmatic reticulum synthesize proteins after the process of transcription of DNA to RNA in the cell´s nucleus entire process is called gene expression mRNA is decoded in a ribosome, outside the nucleus, to produce a specific amino acid chain or polypeptide mRNA: carries code, ribosome attaches itself tRNA: carries one amino acid and sticks to the nucleotide triplett ribosomes consist of rRNA and proteins, amino acids are merged to peptides
RNA-processing
humans have approximately 20 000 genes, can cute up to 1 000 000 proteins ->through RNA processing, different proteins can be built out of one gene
Chloroplasts
-inside them photosynthesis takes place -a type of plastids (only plants have plastids) -are surrounded by two biomembranes -inside: a strongly folded membrane (thylakoid) that is arranged in round piles (granum) in between lies the stoma -plastids contain own DNA and ribosomes -the energetic and material base of life
Photosynthesis
6 CO2 + 6 H2O ---light reaction--> C6H12O6 + 6 O2 -purpose of photosynthesis is the construction of energy-rich organic compounds -complex process with two main parts: light-dependet reaction (on the thylakoid-membranes - grana) and the dark reaction (in the plasma chloroplasts - stroma)
Thylakoid membrane
-Chlorophyll = ring containing N with magnesium as the central atom and al long hydrocarbon chain -chlorophyll is transformed and can give of electrons (e-) when absorbing light
Carotenoids
acts as antioxidants, that prevent the formation of oxygen radicals by absorbing light energy -give colour to flowers an fruits
light absorption
photosynthetically active radiation -> visible light is a small part of the spectrum -about half of the energy emitted by the sun is visible light (most of the rest is infrared radiation) -chlorophylls absorb light in the red and blue range -carotenoids additionally in blue-green but are less concentrated -green light is reflected - leaves are therefore green -plants are green because they absorb little green light -if green is not absorbed it cannot contribute much to photosynthesis
plastids
different types of plastids with different functions -chromoplast: coloured by carotenoids -leucoplasts: without pigments, storage of various substances -chloroplast: photosynthesis -etioplast: colourless (develop in absence of light) -amyloplast: starch storage plastids can be transformed from one form to another they are produced by division of plastids but cannot develop from any other source
Carbohydrates
general chemical formular: (H-C-OH)n -> n=3-7 with one C=O group -glucose: monosaccharide, primary product of photosynthesis, most important component in higher molecular carbohydrates other monosaccharides: galactose, fructose -disaccharides: made up of two monosaccharides (like glucose & fructose), most common disaccharide = saccharose (cane sugar), it is a common form to transport sugars (and thereby energy) in plants
energy storage
all plants store reserve substances in order to survive times without photosynthetic activity Problem: soluble small molecules (mono-/disaccharides) are quickly available for energy production, but high concentration would make the cytoplasm too concentrated (osmotic potential -> trugor), thus not suitable for permanent substance storage in large quantities Solutions: 1. few plants do store greater amounts of dissolved sugar inside the vacuole (sugar cane, sugar beet) 2. polymers of sugars (polysaccharides) are large molecules units that are not soluble (potatoes, cereals) 3. sugars are transformed into fats (like nuts)
oligosaccharides
consists of 3-10 monosaccharides -stachyose (galactose + galactose + glucose + fructose) -gentianose (glucose + glucose + fructose) ->common in legume seeds since we lack the necessary enzymes, bacteria use them in our intestine and produce gas
polysaccharides
= reserve substance Inulin: relatively small polysaccharides (up to 100 fructose units + 1 glucose at the end) common in roots and tubers of the sunflowers family (composites) ->sometimes used as a starch substitute for diabetics (indigestible)
starch
-most important polysaccharide for storage in plants -consists of hundreds to thousands of glucose molecules -is composed of amylose and amylopectin starch molecules are aggregated in starch grains: concentric (or excentric) layers develop by alternating layers of amorphous and crystalline starch
reserve proteins
can be found in cereal seeds such as wheat ->starch and protein are stored in different tissues of the seed
reserve proteins
can be found in cereal seeds such as wheat ->starch and protein are stored in different tissues of the seed -Protein in the aleurone layer -starch in the endosperm protein as a reserve substance is especially important in the seed to sustain the young plant storage in form of small aleurone granules, for example in legumes (like in a garden bean), protein and starch are stored in the same cells of the cotyledons some plant seeds such as beans are composed mainly by the cotyledons - the first pair of leaves
fat / oil reserves
-usually found in seeds and fruits -have the highest energy density -form small drops in cells (oils) or are solid (fats)
Mitochondria
-build of a double membrane, the inner one heavily folded -has its own DNA, ribosomes and protein production (like plastids) -cellular respiration provides all aerobic eukaryotes - living organisms with a nucleus - with energy ->like a reverse reaction of photosynthesis without light and pigments; the colourless, small mitochondria is difficult to see under a light microscope
global plant photosynthesis and respiration
globally, photosynthesis binds 122 Pg (1 petagramm = 1 billion tons) carbon per year from the atmosphere ->about half of this carbon is released back into the atmosphere by respiration in plants, resulting in a net primary production of 61 Pg per year
Endosymbiosis theory
plastids an mitochondria have (a few) own genes ->chloroplasts and mitochondria originate from free-living procaryotes and were absorbed by bigger cells Evidence: -own DNA, ribosomes and protein synthesis like bacteria -plastids, mitochondria and nucleus can only develop through division -genes in plastids and mitochondria are transmitted completely differently, usually only maternally
Cytoskeleton
responsible for dynamic processes and movement inside the cell -made up of individual proteins that congregate to tubes (microtubules made up of tubulin) or microfilaments (composed of actin) -motor proteins move organells along the cytoskeleton´s microtubules
Endoplasmatic reticulum and Golgi-apparatus
-complex system of membranes for synthesis and transport of cellular products -ER is connected to nucleus -rough ER has ribosomes for protein (incl. enzyme) synthesis -golgi-vesicles can excrete products from the cell including the bulding blocks of cell walls
Cell wall components: Cellulose
-in cellulose, adjacent molecules attach in parallels by hydrogen (H) bonds - strict nearly crystallin structure ->it is not easily degradable (by enzyme cellulase) ->is the most common organic molecule on earth ->cellulose in the cell wall is in the form of large packages (fibrils) made up of many parallel molecules ->other compounds connect these fibres an fill the space in between
Cell wall components: Hemicellulose
-composed of glucose and other sugars -it is branched and amorphous - no strictly crystalline structure -a few species use hemicellulose as a reserve substance in seeds ->very hard seeds with "plant-based ivory"
Cell wall components: (Proto) Pectine
Enzyme (pectinase) or inorganic chemicals (KCI + nice acid) dissolves pectins in the cell wall ->cell wall splits and cells separate (maceration)
Cell wall components: Pectic acid
-similar to carbohydrates but with acid groups -positive ions can bind to their negative charge -thus, molecules are reversibly connected by bivalent ions (Ca, Mg) and are swellable through water retention ->used for food (like jam)
structure of primary cell wall
the linkage can be undone by structural proteins and enzymes ->thin cell walls are elastic
Cell wall structure
large cellulose fibres are arranged (more or less) in parallel, connected by cellulose, pectin and proteins connecting in between
Cell wall texture
-primary cell wall: loose texture, rich in pectins, thin and elastic -when cells grow fibrils are pulled apart, cell wall layers are deposited on the inside (from the cytoplasm - the secondary cell wall has parallel texture, poor in pectin, thick and becomes rigid) -interaction between the alignment of microfibrils and the cell´s direction of growth
secondary cell wall modification
in addition to the basic components of every cell wall other additional substances can be embedded or piled on top -Incrustations -Akkrusts -Lignin -Tannins -Akkrusts
