Nutrition and Metabolism Last topic of Digestive System → Test Tuesday on all of Digestive System (Review Monday for test)

Do Now: Part 1: What do you know about nutrients that are needed by the body? Make a list below.

Do Now: Part 2: What is below?______________________ Try to label it with the names of the food groups we looked at in our nutrition menu activity from yesterday. Then, predict how many servings of each group is recommended for daily consumption.

Nutrition A nutrient is a substance in food that is used by the body to promote normal growth, maintenance and repair Major nutrients: Carbohydrates, lipids and proteins (what are these called?) Vitamins and minerals Water

Dietary Sources Carbohydrates (sugars): Except for milk sugar and small amounts of glycogen in meats, all the carbohydrates we ingest are derived from plants examples: fruits, sugar cane Lipids: Most dietary lipids are neutral fats – triglycerides Saturated fat: in animal product, bad for you Unsaturated fat: in vegetable product, good for you

Dietary Source Proteins: Animal products contain the highest quality proteins Egg, milk and most meat proteins are complete proteins that meet all of the body's amino acid requirements Legumes (beans and peas), nuts are also protein- rich, but their proteins are nutritionally incomplete as they’re low in one or more of the essential amino acids

Dietary Source Vitamins: Organic nutrients of various forms that the body requires in small amounts No one food contains all the required vitamins Most vitamins function as coenzymes- they act with an enzyme to accomplish a particular type of catalysis Minerals (or elements): Body requires 7 Calcium, phosphorus, potassium, sulfur, sodium, chloride and magnesium The most mineral-rich foods are vegetables, legumes, milk and some meats

Metabolism Metabolism is a broad term referring to all chemical reactions that are necessary to maintain life: Catabolism: Substances are broken down to simpler substances Anabolism: Larger molecules or structures are built from smaller ones

Carbohydrate Metabolism The cells of the body use carbs as their fuel to carry out functions: Glucose, known as blood sugar, is the major breakdown product of carbohydrate digestion It is also the major fuel used for making ATP in most body cells

Carbohydrate Metabolism Homeostasis of blood glucose level is critically important: Hyperglycemia: excessively high levels of glucose in the blood Hypoglycemia: when blood glucose levels are too low

Fat Metabolism The liver handles most lipid metabolism that goes on in the body: The liver cells use some fats to make ATP for their own use While fats are an important energy source, cholesterol is never used as a cellular fuel What are examples of foods that contribute to good and bad cholesterol?

Protein Metabolism Ingested proteins are broken down to amino acids Cells cannot build their proteins unless all the needed amino acids (20) are present: Essential amino acid: 8 of the these amino acids cannot be made by the cells, they are available to the cells only through the diet

The Central role of the liver in metabolism The liver cells: Detoxify drugs and alcohol Make substances vital to the body: cholesterol, clotting proteins Can regenerate rapidly and easily (as little as 30% of original liver can return to full size)

The Central role of the liver in metabolism The liver helps maintain blood glucose levels within normal range (100 mg glucose/100 ml of blood) Glycogen: large polysaccharide made of glucose Glycogenesis: Glucose converted to glycogen and stored Glycogenolysis: Stored glycogen converted to glucose Gluconeogenesis: Amino acids and fats converted to glucose

Cholesterol metabolism and transport It is not used as an energy fuel It serves as the structural basis of steroid hormones and Vitamin D It is lost from the body when it is broken down and secreted in bile salts → leaves the body in feces

Lipoproteins Lipoproteins: lipid protein complexes that transport fatty acids, fats and cholesterol Low density lipoproteins (LDLs): Transport cholesterol and other lipids to body cells (bad → builds up in tissues) High density lipoproteins (HDLs): Transport cholesterol from the tissue cells to the liver for its disposal in bile and ultimately feces (good→ removes cholesterol from body)