Zellbiologie

phosphoanhydride bonds
Water can be added to ATP to form ADP
Delta G⁰ = -30.5KJ/mol
 

• > Important carrier molecules
• > Oxydation/reduction reaction require protons/electrons
• > Proton carriers accept temporarily protons (H + ) and high energy electrons (e - )
• > NADPH, NAD+ and FAD

Energetically unfavourable reactions (ΔG > 0 edergonic) can only occur if they are coupled to an
energetically favourable (exergonic) reaction and the net free-energy change for the pair of coupled reactions
is less than zero.

• Carbohydrates: Starch is hydrolysed by α-amylase (produced by pancreas) to disaccharides. The disaccharides are hydrolysed to monosaccharaides which can be absorbed from the intestine
• Lipids: Must be emulgated by bile from the liver. Then they are hydrolysed by lipases to fatty acids and glycerol and taken up into the cells
• Proteins: Are first denatured in the stomach by acids and shaking. In the next steps they are hydrolysed to polypeptides by pepsin and t

The glycolysis can be divided into three parts:

• In the first step, energy (2 ATP) is invested to make one molecule of fructose 1,6-biphosphat out of one molecule of glucose
• In the second step, the six-carbon sugar is cleaved to two molecules of glyceraldehyde-3-phosphate (three-carbon-sugars)
• In third step, energy is generated (4 ATP) by making two pyruvate molecules out of the two glyceraldehyde-3-phosphates.

lactate is release in blood and reach the liver. There the lactate is re-cycle in pyruvate that can be retransformed into glucose

• A carbon is cleaved from the pyruvate to form acetic acid. The cleaved carbon is released as CO 2 .
• Activation of acetic acid with CoA (a derivative of pantothenic acid = vitamin B 5 ) to form acetyl-CoA
• Formation of NADH+H+

--> This processes are all done by one multienzyme complex called pyruvate dehydrogenase

E4&4)+1&7#7.34&4).&
E4&4)+1&7#7.34&4).&
 

• Degradation of (activated) acetic acid to CO² and H² (in form of NADH or FADH 2 )
• Transfer of the bound H² to respiratory chain

--> It is the link between glycolysis and respiratory chain and the metabolic link between metabolism of carbohydrates, lipids and amino acids

• NADH gives two electrons to the first complex (NADH dehydrogenase complex) of the respiratory chain: NADH --> NAD⁺ + H⁺ + 2e^- , the H⁺ remain in the matrix of the mitochondrion
• The electrons are passed on through the different complexes of the respiratory chain, going to a lower level energy each time they “pass” a complex. The energy from the electrons is used by the complexes to transfer H⁺ form the matrix to the intermembrane space of the mitochondrion against the concentration gradient
• At the end of the electron transport chain, the electrons from, together with the H⁺ which remain in the matrix and with 1⁄2 O² , H²O
• The H⁺ which are in the intermembrane space can flow along their concentration gradient back into the matrix through a transmembrane protein called ATP synthase which uses the energy of the H⁺ flow to produce ATP from ADP.
• ATP synthase can also transport H⁺ against the concentration gradient from the matrix to the intermembrane space (energy provided by the break down from ADP to ATP)

An enzyme involved in converting glucose to glycogen. It acts as a primer, by polymerizing the first
few glucose molecules, after which other enzymes take over. Thus it is found in the middle of a glycogen
molecule.

liver 150g
muscle 250g

pancreas secrete insulin in case of high glucose concentration in blood
pancreas secrete glucagon in case of low glucose concentration in blood

cholesterol from fat

Triglycerides a cleaved hydrolytically (step-by-step) by lipases. The result is one molecule of glycerol and three
free fatty acids. The glycerol is channelled into glycolysis. The fatty acids are not soluble in water but can be
emulsified by bile acids such as cholic acids (derived from cholesterol) and their conjugated bile acids
gylocholic acid and taurocholic acid. The “output” of this process are mixed micelles of about 5nm diameter
which consist of bile salt on the outside and cholesterol and the free fatty acids on the inside. These micelles
can now be taken up by the intestine. Once in the body, the fatty acids are processed further on.

They transport dietary lipids from
the intestines to other locations in
the body. Chylomicrons are one of
the five major groups of lipoproteins

The fatty acids are, as described above, hydrolysed by lipases. In a next step, the fatty acids are activated in
order to produce Acyl-CoA by transferring the fatty acids to CoA. The acyl is cleaved again from CoA and added
to carnitine. The Acyl-Carnitine complex is transported into the mitochondrion. There, the complex is cleaved
again, the carnitin leaves the mitochondrion again and the acyl is once again bound to CoA. In the β-oxidation
process itself, the Acyl-CoA is (in several steps) “cleaved” in an Acetyl-CoA, which is transferred to the TCA-
cycle and another Acyl-CoA (Acly is now shorter by 2 C-atoms).

Das Proteasom (auch: Macropain) ist ein Proteinkomplex von 1700 kDa, der im Cytoplasma und bei Eukaryoten auch im Zellkern Proteine zu Fragmenten abbaut und daher zu den Peptidasen (auch Proteasen) zählt.

Eucaryotic Cells
> ATP-dependent
> > Proteins are first „marked“ Ubiquitin
> very conserved mechanism
> Degradation by a very large cytosolic Enzyme complex = Proteasome

1. digestion -->micelle (with bile acid (cholesterol))
2. activatein cytosol-->acyl-CoA
3. transport mitochondria
4. Beta-oxidation-->acetyl-CoA
5. TCA-cycle -->NADH etc
6. oxidative phosphorylation-->ATP
    

Since synthesis and degradation of body proteins (total about 10 kg) takes place all the time and there is also a
continuous excretion and uptake of proteins , there are about 70 to 100 g of free amino acids in our body at
any given time.

Proteolysis: Hydrolysis of the peptide bonds between amino acids.

• Digestion (gastrointestinal tract): Enables absorption of amino acids, provide amino acids for protein biosynthesis or as sources of energy
• Quality control: “aging”/damaged proteins or newly synthesised proteins with defects
• Regulation of biologically processes such as cell cycle, signal pathways (receptors and their ligands) and tissue remodelling

--> Proteins are typically degraded by lysosomes but there is also a lysosomal-independent degradation, which is ATP-dependant

Two part in the immune system
— Innate immunity
— Adaptive immunity

Immunity starts by a physical barrier
— skin
— respiratory tracts
— digestive tracts

> Once inside, pathogens are recognized as “foreign” molecules
> Immune system is constantly “scanning” the inner environment for organism that are not produced by the body
> Immune cells interact with other cells by cell-cell contact
> “Self” molecules induce a neutral reaction when “nonself” induce an activation

• Foreign or Non-self molecules are recognized by receptors
• Pattern recognition receptor (PRR)
• Main family: Toll-like receptors (TLR)
• Recognize broadly shared pathogen molecules (PAMPs)
• it is a “super” protein family

• TLR-1:- Bacterial lipoprotein
• TLR-2:- Bacterial peptidoglycans
• TLR-3:- Double stranded RNA
• TLR-4:- Lipopolysaccharides
• TLR-5:- Bacterial flagella
• TLR-6:- Bacterial lipoprotein
• TLR-7:- Single stranded DNA

• White blood cells (leukocytes)
• 3 types: Neutrophils (60%) Eosinophil (5%) Basophil (<0.5%)
• First line of active defense
• Respond to foreign molecule recognition by degranulation or phagocytosis

• Very aggressive cells
• Short life span (around 5 days)
• Attack pathogen by phagocytose
• granules contain anti-bacterial agents

— defensins (make pores in bacterial membranes)
— proteolytic enzymes (e.g. Cathepsin G)
— lysozyme (enzyme digesting the bacterial wall)

• Remain at the infection site and are degraded by macrophages or excreted in pus.