Enzymes are (a) which speed up the biochemical (b) in living organisms. The enzymes themselves are not changed in these reactions, that is they are biological (c). Enzymes are (d)- each one controls only one type of reaction. They are (e)by high temperatures and by extremes of ph.

Enzymes are biological catalysts. Catalysts lower the activation energy for reactions. The lower the activation energy for a reaction, the faster the rate. Thus enzymes speed up reactions by lowering activation energy.

Explanation:

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the level of progesterone is low at the pre-ovulatory phase of the cycle but it gradually increases and the levels are high at the luteal phase. if pregnancy occurs, the level of progesterone will be high throughout the pregnancy.

if egg is fertilized and the mother gets pregnant, progesterone starts preparing the uterus for the implantation. it starts building up the lining of uterus and make it hostile of the period of pregnancy.