Cell Biology Lecture 5 overview p.88-109

Condensations remove H2O, combining organic molecules; hydrolyses do opposite.

ATP energy drives condensations(1Pi = -11 to 13kcal/mol typically [energy available depends on reactant concentrations]; PiPi = -26); hydrolysis rxns.(exergonic); condensations (endergonic).

Tail polymerizations (polynucleotides, some simple polysaccharides) use energy right away (error-checking possible; if last residue from head polymerization is removed, high energy bond gone!)

Proteins, fatty acids use head polymerization (can afford errors).

Three stages of catabolism: 1.Polymers to subunits (intestines, lysosomes) 2.monomers to acetyl CoA (cytosol, mitochondrion) 3.acetyl CoA to CO₂, H₂O, (ammonia if a.a. catabolized).

Fermentation: organic molecule = both donor and acceptor of reducing power (oxidized and reduced). Glycolysis: glucose to 2 pyruvate. Energy concentrated, then harvested.

Glyceraldehyde 3-phosphate converted to 3-phosphoglycerate. Aldehyde to carboxylic acid=net energy-yielding reaction. Oxidized carbon = lower energy. 1NADH, 1ATP/3C made. -3 kcal/mole

About ½ of available energy captured as ATP (heat also useful) as glucose is converted to H₂O, CO₂. (Automobile = 20-25% efficient) 10⁹ ATP/cell; turned over every 1-2 minutes.

O₂ = best oxidizing agent. Anaerobic options for pyruvate: must regenerate NAD from NADH. Ethanol + CO₂, lactic acid, acetone (Clostridium acetobutylicum of Chaim Weissman), etc.

Pyruvate dehydrogenase of mitochondrion: clever multisubunit (60 polypeptides) complex maximizes concentrations of substrates near enzymes.

Fatty acid oxidation: 2 C at a time. Huge amounts of energy from hydrocarbon chains.

Electron transport (ox.-phos.) and Peter Mitchell. Chemiosmotic Hypothesis/Theory.

Fat = 1/6th the mass of glycogen to store equivalent energy. Animals can't convert fat to sugar (testes, brain need sugar). Glycolysis and TCA cycle: "Central metabolic clearinghouse". Anapleurotic mechanisms.

Liver, muscle cells, circulatory and respiratory system cooperation and world record average velocities for various race distances.

Why can't humans make 9 amino acids, vitamin C, etc.? Why can't humans fix nitrogen? "Use it or lose it".

The Nobel prize for Chemistry in 1997 was shared by Dr John Walker of the Medical Research Council's Laboratory of Molecular Biology (LMB) at Cambridge, Dr Paul Boyer of the University of California at Los Angeles, and Dr Jens Skou of Aarhus University in Denmark. The prize was for the determination of the detailed mechanism by which ATP shuttles energy. The enzyme which makes ATP is called ATP synthase, or ATPase, and sits on the mitochondria in animal cells or chloroplasts in plant cells. Walker first determined the amino acid sequence of this enzyme, and then elaborated its 3 dimensional structure. Boyer showed that contrary to the previously accepted belief, the energy requiring step in making ATP is not the synthesis from ADP and phosphate, but the initial binding of the ADP and the phosphate to the enzyme. Skou was the first to show that this enzyme promoted ion transport through membranes, giving an explanation for nerve cell ion transport as well as fundamental properties of all living cells. He later showed that the phosphate group that is ripped from ATP binds to the enzyme directly. This enzyme is capable of transporting sodium ions when phosphorylated like this, but potassium ions when it is not.

Balfour Declaration 1917

November 2nd, 1917

Dear Lord Rothschild,

I have much pleasure in conveying to you, on behalf of His Majesty's Government, the following declaration of sympathy with Jewish Zionist aspirations which has been submitted to, and approved by, the Cabinet.

"His Majesty's Government view with favour the establishment in Palestine of a national home for the Jewish people, and will use their best endeavours to facilitate the achievement of this object, it being clearly understood that nothing shall be done which may prejudice the civil and religious rights of existing non-Jewish communities in Palestine, or the rights and political status enjoyed by Jews in any other country."

I should be grateful if you would bring this declaration to the knowledge of the Zionist Federation.

Yours sincerely,

Arthur James Balfour