Nutrition, metabolic states as related to energy pathways. I will work through the slide presentation of chapter 25, just focusing on selected slides and asking how to link back to earlier supporting information:

Protein turns over a certain rate reflected by an outflow of nitrogen in the urine. As long as the diet produces an excess of amino acids in circulation over the daily loss, there is no net loss of protein, and the excess amino acids can be catabolized. This creates a minimum daily protein requirement in the diet prevent loss of bodily protein, amounting to 0.8 to 1.5 g protein per kilogram body weight per day. Excess amino acids will be used to generate ATP, or synthesize glucose as discussed in a previous chapter. There is essentially no significant conversion of amino acids to fatty acids. In ketosis, proteins will be degraded as necessary to gain amino acids to support gluconeogenesis. slide #14

Hunt down whether you think the following are true or false: a)Protein (after digestion to amino acids) is one of three major sources of dietary calories, along with carbohydrates and fats. b)You body has a reserve supply of protein to degrade and utulize in times of starvation that is distinct from your functional proteins. c)Amino acids are funneled into the TCA cycle for oxidation. In order to do so, the nitrogen is removed and concentrated into urea for excretion. d)During a protracted fast, the liver will use amino acids derived from body protein to keep up blood glucose levels. e)All 20 amino acids can be used to synthesize glucose.

A summary of information about contribution of lipids to daily calorie usage: 1)Fatty acids are broken down to acetyl CoA which is burned in the TCA cycle. 2)Muscles use fatty acids first, and then augment that with glucose oxidation, thus sparing glucose for periods of high energy output, and sparing bodily glucose for cells that are more directly dependent on it. 3)Fatty acids are mobilized from adipocytes and transported by serum albumin to various cells that can utilize them. Serum albumin can’t pass the blood brain barrier, so the brain can not directly use fatty acids as an energy supply. 4)Fatty acids can not be converted to glucose, so when the diet is short of carbohydrates, this causes a crisis even if there is a plentiful supply of energy in the fat depot. 5)The liver can convert fatty acids to ketone bodies (a blood borne version of acetyl CoA). When this happens, you are said to be in ketosis. Ketone bodies partially replace the requirement for glucose by many kinds of cells, including cells in the brain 6)Insulin restrains the release of fatty acids from adipocytes, forcing muscles to rely more heavily on oxidizing glucose for energy.

Dietary glucose shortage: Low blood glucose will be first met by drawing on liver glycogen, then on liver gluconeogenesis. Gluconeogenesis will be supported by amino acids, either from dietary sources or as a result of degrading tissue proteins. Insufficient supply of amino acids to support gluconeogenesis depletes liver oxaloacetate and causes onset of ketogenesis. After 48 hours in ketosis, the brain increases its use of ketone bodies and reduces its reliance on glucose, thus reducing the degree of muscle wasting necessary to support ketosis. slide #17

True or False? a)During starvation, there will cease to be any urea excretion. b)The reason you need oxaloacetate to oxidize acetyl-CoA is because oxaloacetate is an allosteric stimulator of citrate synthase at the beginning of the TCA cycle. In untreated type I diabetes (caused by failure to make insulin), even though there is high blood glucose: c) The adipocytes secrete high levels of fatty acids which are imported to make acetly-CoA in the liver. d) The liver is driven into gluconeogenesis. e) There is excessive production of ketone bodies.

FED Adipocyte TAG Amino acids GUT slide #24

True or False? a)The fed state will feature a surge of insulin secretion. b)Insulin will favor making glycogen and inhibit breaking down glycogen. c)Fatty acids move from the intestines to adipocytes carried by serum albumin. d)The lipid in the diet that is a major source of calories is triacylglycerol. Cholesterol in the diet is not useful as a source of calories.

The role of NADPH in all of this is: a)NADPH is required to support reductive biosynthesis. The largest demands for reductive biosynthesis are generated by lipid synthesis and DNA replication. b)NADPH is a high energy molecule. c)NADPH is a byproduct of glycolysis. d)NADPH is interchangeable with NADH. e)NADPH is synthesized as needed by the pentose phosphate pathway.

FASTING Adipocyte TAG slide #25

True or False? a)In the fasting state liver glycogen is mobilized to support blood glucose. b)Muscle glycogen can not be used to support blood glucose levels because muscle does not have glucose-6-phosphatase.

KETOSIS Ketone bodies Adipocyte TAG slide #26

True or False? a)Ketosis will set in during starvation. b)Ketosis will also set in on a diet high in fat and protein but very low in carbohydrate. c)On any diet, ketosis will set in during uncontrolled diabetes.