NUTR 235 Science of Foods

Which metabolic situation will activate cholesterol synthesis? 1. High levels of ATP 2. Glucagon 3. Insulin 4. Epinephrine

1 and 3

Which of the following fatty acids is an essential fatty acid (mammals cannot synthesize)? 1. C16:1c9 2. C18:2c9,12 3. C18:3c9,6,3

2 because you cannot synthesize a double bond at carbon 12.

What is the metabolic fate for ammonia?

1. Glutamate Synthesis 2. Glutamine Synthesis 3. Carbamoyl Synthesis

What is Rhizobium

A nitrogen fizing bacteria that lives in root nodules of leguminous plants, where they symbiotically fix nitrogen for the bacteria and the plant. The nodule of the plant provides a hypoxic environment, which is necessary for the nitrogen fixation reactions.

What amino acids are essential only under certain conditions?

Arginine can be essential because premature babies cannot make it. Tyrosine is synthesized from phenylalanine so if phenylalanine is deficient, so will tyrosine.

Enzymes involved in nitrogen fixation?

Dinitrogenase reductase (binds ATP) and dinitrogenase

What type of reaction does a cell use to convert palmitoleate fatty acid (C16:1c9) into cis-vaccenate (C18:1c11)

Elongation

What are the essential amino acids?

Histidine, Isoleucine, Leucine, Lysine, Methionine, Phenylalanine, Threonine, Tryptophan, Valine

What reaction does glutamate dehydrogenase catalyze?

It catalyzes the binding of alpha-KG to ammonia (NH4+). using NADPH, to make glutamate. It is found in the mitochondria of eukaryotes and most microbes. Allosterically regulated by high ATP and GTP levels inhibiting alpha-KG synthesis.

Why is N2 (nitrogen) not useful in this form?

N2 is chemically inert, requires conversion to ammonia NH3. Breaking the triple bond has a high activation energy.

What is nitrogen fixation?

Only prokaryotes can carry out nitrogen fixation. It is energetically expensive.

What is the common precursor for synthesis of triacylglycerol and glycerophospholipids?

Phosphatidic Acid

HMGCoA

The enzyme that is highly regulated in cholesterol synthesis.

Malonyl CoA

The regulated step in fatty acid synthesis. Like most carboxylation reactions, it requires Biotin as a coenzyme. It is catalyzed by the enzyme: Acetyl CoA Carboxylase during fatty acid synthesis.