Cell Biology Summary: Essentia­l Concepts & Structur­es Explaine­d

Cell Bio 11.11.09

-DNA

• anti parallel double helix 3´and 5´ end
• between the strands hydrogen bonds
• major groove and minor groove
• spherical hindrance makes other parings impossible
• circular molecule in bacteria chloroplasts mitochondria several viruses
• problems when denatured or during replication

·         tension in the rest

·         when opened at the middle extra twist tighter bindings to the bindings right and left

·         super-coiling (telephone)

·         structure → super-coil

• simian virus 40 → double stranded DNA virus, infects monkeys

·         picture shows super-coiling

·         we must get able to get rid of the super-coiling → special type of enzymes

·         topoisomorases

·         either bind one or two strands and “entwirren” the DNA

• DNA extraction

·         1. DNA is in the nucleus of the cell

·         2. cell membrane is disrupted with a detergent interfere with the lipid structure

·         3.alcohol is added to separate DNA from other cell components

• DNA migrates in the electric field → gel-electrophoresis

·         sort nucleotides by seize

·         restrictionendonuclease producing of predictable pieces of DNA

• DNA is able to denature and renature

melting temperature, defined by the composition of the DNA

·         DNA high in GC have higher melting temperatures

·         polymerasechainreaction depends on this melting points

• PCR

·         heat denaturation 96°

·         binding of primer → primer annealing 50-65°

·         replicating process → polymerase recognizes the free end and will start the elongation process 72°

·         in nature enzymes need the free oh of the sugar to start replication

·         taq polymerase → thermus aequaticus

-RNA

• difference between DNA and RNA

·         RNA single stranded but can form partial double stranded regions

·         not only double stranded but also loops hairpins pseudo knot

·         folding only with comparing bases!

·         Ribose instead of deoxyribose oh group in place 2

·         base uracil instead of thymine (see script)

• m-RNA

·         messenger RNA

·         most often occurs as a single strand

·         only for transfer the message from the nucleus to the ribosomes

·         same process for eucariotic and procariotic organisms

·         process of translation and transcription (nachschauen)

·         only one strand is copied → oncogenesstrand→ the other strand is used for another gene or is empty, places where both strands are codogene are very rare in eucariotics

·         t RNA is the opposite strand to the messenger RNA

·         messenger RNA is produced in the nucleus → transcription

·         translation → in the cytoplasm at the ribosomes

·         therefore a transporting process is necessary in eucariotes

·         in procariotes the two steps may occur at the same time

• t-RNA

·         special structure + binding place for a aminoacid and one for the m RNA

·         region formed by the stem and stem (region where bases pair)

·         two arms with special function

·         anticodon to the mRNA → determines which aminoacid is carried

·         other two arms responsible for folding up → fitting into the ribosome

·         3´oh end there the amino acid is attached → aminoacidbinding

• rRNA

·         needs to have a proper secondary structure

·         large subunit 60% rRNA and small subunit 70% rRNA

·         not bound bases are responsible for the folding

• extraction of total RNA

·         formaldehyde keeps rna from not folding

·         more or less the same concentration of rna al tissues

• all types work together in the translation

-ATP

• nucleotide

◦     use for forming DNA and RNA

◦     shorttime energy storage

◦     used within 2 minutes

◦     energy is in the bonds → when breaking the bond energy gets free

◦     proper enzymes have to take up substrat and atp at the same time to not loose the energy as heat

◦     same for carriers

• RNA is involved in processing of other RNAs

◦     intron must be removed → spleißing → removal is done by splisosome

▪     made up of RNA and DNA

◦     small nuclear RNA → snrnp complexes

·         catalytic activity in the RNA part not in the protein part

·         contribute to the processing of ribosomal RNA

• Ribozymes

◦     RNA with catalytic activity

◦     plant viroides

▪     no proteins detected within to form the genome from a strand to a circular structure

▪     hammerhead ribozymes or hairpin ribozymes

▪     used in biotech

▪     si RNA today

• micro RNA

◦     serve in regulation of gene expression

◦     are not translated

◦     the label complementary target mRNA for destruction

Polysaccarides and Lipids

• sugars and polysaccarides

◦     consist of repeating units of sugars

◦     sometimes alternating pattern of two kinds of sugars

• polysaccharide are used for storage of energy:

◦     starch

◦     glycogen

• structural purposes
• the structure of glucose

◦     6 carbon numbered by the highest oxidated carbon

◦     hexose

◦     ending -ose → sugar

◦     one position of the ring is Oxygen

◦     c1 → linear polymerization

◦     c4 → involved in linear polymerization

◦     c6 → involved in crosslinking polymerization

◦     orientation of the c1 oh-group identifies alpha (rauf) and beta gluccose (runter)

• disaccarides

◦     of two monosaccarides → reaction forming a glycosidic bond

◦     maltose → 2 alpha gluccose

◦     lactose → beta galactose and beta gluccose → bond with twist → special enzym needed to split up → some loose the capability to split up lactose → lactose-intolerance NOT allergy

◦     sucrose → alpha glucose and beta fructose → kristallzucker

• Starch

◦     alpha gluccose linked by alpha glycosidic bonds

◦     amylopectin → branched

◦     in plants

• Glycogen

◦     storage polysaccaride in liver and muscles

◦     animals

◦     highlyy branched

◦     every 8-10 units with sidechains of 10-12 molecules

◦     two organsystems that are involved in sythesizing glycogen: liver and muscles

▪     purpose: muscles → to get energy

liver → to release it to other systems

▪     the branches enable the enzymes to attack at any end so that energy is offered much faster

▪     no endoglycogenolases

• Cellulose

◦     beta d gluccose units

◦     beta glycosidic linkage

◦     rigid linear form

◦     Plant cell wall is composed of cellulose.

▪     Can not be digested

▪     ruminant animals are able to digest cellulose

·         have microorganisms that can split up cellulose

◦     exosceleton of insects spiders and crustanceans

◦     cell wall of fungi

• bacterial mureinsacculus

◦     cell wall of peptidogycan

◦     sugar is the backbone of the molecule

◦     5 aminoacid are attached

◦     bacteria do not have colesterol

• Lipids

◦     differ in mode of assembly

◦     several lipids are important

▪     fats

▪     waxes

▪     phospholipids

▪     glycolipids etc

◦     fatty acids

▪     long unbranched hydrocarbon chains with a carboyxl acid

▪     cooh group binds to glycerol → esterbonding

▪     saturated or unsaturated versions → double bonds

◦     mono di or triacylglycerides

▪     see script

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