F.4 BIO

1) In humans, alcohol dehydrogenase contained in the lining of the stomach and in the liver. It catalyzes the oxidation of ethanol (alcohol beverage) to acetaldehyde. Alcohol dehydrogenase is also involved in the toxicity of other types of alcohol: for instance, it oxidizes methanol (also known as methyl alcohol or wood alcohol) to produce formaldehyde, and ethylene glycol (automotive antifreeze) to ultimately yield glycolic and oxalic acids. Humans have at least six slightly different alcohol dehydrogenases.

2) Amylase breaks down starch. They are classified as:
~ α-amylase breaks down long-chain carbohydrates, ultimately yielding maltotriose and maltose from amylose, or maltose, glucose and "limit dextrin" from amylopectin;
~ β-amylase produced by plants and microbes, it catalyzes the hydrolysis of the second α-1,4 glycosidic bond, cleaving off two glucose units (maltose) at a time;
~ γ-Amylase, also called glucoamylase or lysosomal α-glucosidase, found in mammalian instestine. It cleaves the last α(1-4)glycosidic linkages at the nonreducing end of amylose and amylopectin, yielding glucose, γ-amylase will cleave α(1-6) glycosidic linkages.

Amylase is most prominent in pancreatic juice and saliva.

Salivary amylase (ptyalin)
Optimum pH - 5.6 - 6.9
Human body temperature - 37 degrees Celsius
Presence of certain anions and activators:
Chlorine and Bromine - most effective
Iodine - less effective
Sulfate and Phosphate - least effective
Inactivated in the stomach by gastric acid

Pancreatic amylase
Pancreatic α-amylase randomly cleaves the α(1-4)glycosidic linkages of amylose to yield dextrin, maltose or glucose molecules. It adopts a double displacement mechanism with retention of anomeric configuration.

3)Osmosis is the movement of water through a semipermeable membrane from a region of low solute potential to a region of high solute potential (or equivalently, from a region of high solvent potential to a region of low solvent potential). The semipermeable membrane must be permeable to the solvent, but not to the solute, resulting in a pressure gradient across the membrane.

added: Theorically, osmosis occurs with diffusion at the same rate in a fully permeable membrane, therefore will not result in a change in concentration.

2) amylase

1) yeast
2) don't know
3) osmosis can only occur in differentially permeable membrane, not in fully permeable membrane.