Mendel crossed y/y; r/r (yellow wrinkled) peas with y/y; r/r (green smooth) peas and selfed the f1 to obtain an f2. in the f2 what proportion of the yellow wrinkled individuals were pure-breeding? the first number is the number that are pure breeding.

The answer is 3/36. The proportion of yellow, wrinkled peas are pure-preeding. This means that they are homozygous for this trait. There are 9 yellow,wrinkled peas. What proportion of these are R/R;Y/Y. I'm not writing out all 16 genotypes for the cross, but you'll see that only one individual is R/R;Y/Y. So the proportion of yellow,wrinkled seeds that are pure-breeding is 1/9.  If you do a punnet square for the F1 cross, you'll observe the 9:3:3:1 ratio, described above, in F2. 

both anaerobic and aerobic respiration use glucose (or other carbohydrates), proteins and lipids to produce atp and nadh. cell uses those energy molecules, obtained from food and   breaks them down during the chemical reactions of respiration. in anaerobic respiration, nadh is regenerated to nad+ by enzymes lactate dehydrogenase (lactate is produced, e.g. in muscle cells) or by alcohol dehydrogenase where ethanol is produced (alcohol fermentation), while in aerobic respiration, electrons from nadh are deposited in the mitochondria to regenerate nad+ (electron transport chain. anaerobic respiration produces 2 atp per molecule of glucose compared to aerobic respiration where about 38 atp molecules are produced.