Nutrition

What's the RDA for fats? Saturated fats?

20-30% of the daily diet should come from fats. Saturated fats should be no more than 7-10% of your daily diet.

How many molecules of CO2 per glucose are produced in the citric acid cycle?

3, if you include the one made in the transitional phase. That is per pyruvic acid. If you are talking about the number per glucose, then it is 6 or 4 if you are ignoring the transitional phase.

What's the RDA for carbohydrates?

45-65% of your daily calories.

How many molecules of NADH per glucose are produced (including the transitional phase)? FADH2? ATP?

8 NADH, 2 FADH2 and 2 ATP.

How would you define the postabsorptive state?

The GI tract is empty and the goal during this time is to maintain stable blood sugar which will ensure that the brain has access to its fuel.

Where does the citric acid cycle take place? The electron transport chain and oxidative phosphorylation?

The citric acid cycle takes place in the matrix of the mitochondria. The ETS takes place on the inner membrane of the mitochondria.

What are sources of glucose in the postabsorptive state? Explain each.

The first source is glycogen in the liver. These can maintain blood sugar levels for about 4 hours. After that your body goes to glycogen that has been stored in the skeletal muscle. This begins to be broken down before the reserves in the liver are completely gone. Once this runs low, your body starts to break down fats. Adipose and liver cells break triglycerides down into glycerol and fatty acids. The liver converts glycerol to glucose (gluconeogenesis). Fatty acids are converted to acetyl CoA, which can't be converted to glucose, so it can't fuel the brain, but it can help generate ATP. Next the body would go to protein. Amino acids would be deaminated and become citric acid cycle intermediates.

What are the major minerals? What is the main function of each?

The major minerals (those you need in larger quantities) include calcium, phosphorus, potassium, sulfur, sodium, chlorine, magnesium. Calciums' main function is to build bones and teeth. Phosphorus helps build bones and teeth and also is part of nucleotides (the molecules that build DNA, RNA). Sulfur helps build amino acids. Chlorine is a main component in gastric juices, serves in nerve function and helps with osmotic balance in the blood and interstitial fluids. Sodium helps with water balance, blood pressure, nerve and muscle function. Magnessium is a co-factor with enzymes.

What are the most important trace minerals? What is the main function of each?

The most important trace minerals include iron, zinc and iodide, but there are many more. Iron binds to oxygen and carries it through the blood. Zinc is a component of some proteins and digestive enzymes. Iodine is the main component of thyroid hormone.

What are the reactants of glycolysis? The products?

The reactants are glucose and 2 NAD+ molecules. The products are 2 ATP, 2 NADH+, and 2 pyruvic acid.

What is the response to high levels of ATP?

The slowing or stopping of cellular respiration. Glucose is then stored as glycogen (glycogenesis).

What's a complete protein? Incomplete?

There are 20 amino acids (the building blocks of protein). Some of these we can build in our body if we don't include them in our diet (non-essential). Others we can not make, so we have to get them in our diet (essential). A complete protein comes with all 20 amino acids. All animal proteins are complete. An incomplete protein doesn't come with all 20 amino acids, but if you eat several different kinds of incomplete proteins together, then you get all 20.

Which of the following include the correct reactants for glycolysis (the list might not be complete)?

glucose and NAD+

Lipolysis is:

Breakdown of fats into fatty acids and monoglycerides

What monosaccharide is used to generate ATP?

Glucose.

Catabolism is:

The breakdown of molecules and tissues

Briefly explain how lipids make it from the digestive tract to the cells of the body.

A micelle is formed in the small intestine. A micelle is made of bile salts surrounding the fatty acids and fat soluble vitamins. The micelle migrates to the enterocytes (the cells lining the small intestine). These then diffuse across the cell membrane without any trouble, as lipids are soluble in the cell membrane (phospholipids). The enterocyte then reforms the triglycerides - linking glycerol to fatty acids. This is surrounded by a phospholipid and protein coating. The whole structure is called a chylomicron. The chylomicron is actively transported out of the basement membrane of the enterocyte and diffuses into the lymph system. From there it travels to the blood. Lipoprotein lipase is an enzyme on the endothelial walls (the walls of the capillary). When chylomicrons come by this enzyme diffuses in, breaks the triglycerides into glycerol and fatty acids and the nearby cells take these nutrients in.

Define the terms nutrient, macronutrient and micronutrients.

A nutrient is a substance from foods that we eat that the body can use for nourishment (growth, maintenance, repair, and daily functioning). Macronutrients make up most of what we eat. THere are three of them: carbohydrates, proteins and lipids. Micronutrients are essential, but we only need them in smaller amounts. The key micronutrients are vitamins and minerals.

Describe the structure, risks, and examples of saturated fats.

A saturated fat is solid at room temperature and is found in animal products. One example is the white fat you find marbling meat. Risks are an increased chance of cardiovascular disease (laying down plaque inside the vessels of the body which over time can become blocked, which leads to heart attack/stroke). A saturated fat is a long chain of carbon. Each carbon of the chain, except for the carbon on the ends, is bound to two hydrogen molecules. The carbon atoms on the ends are bound to three hydrogen molecules. The carbon chain is 'saturated' with hydrogen.

How much protein does the body need per day (generally)?

About 100 grams of protein per day.

How long after a meal does the absorptive state last?

About 4 hours.

What are the reactants of the citric acid cycle?

Acetyl CoA, oxaloacetic acid.

Define the terms anabolism and catabolism.

Anabolism is the building up of molecules (taking smaller parts and making bigger molecules). Catabolism is the tearing apart of bigger molecules and forming smaller parts. For example, digesting a protein into amino acids. This is catabolism. Taking amino acids and building a protein out of them would be anabolism.

Which vitamins are water soluble? Fat soluble?

B and C are water soluble. A,D,E, and K are fat soluble.

Which body cells depend solely on glucose?

Brain

What kind of polysaccharide do we eat, but can't absorb? What are the benefits of it?

Cellulose. We don't have the enzymes to break down cellulose. The benefits of this are that it adds bulk to the stool, it pulls water into the colon to moisten the stool, making it easier to pass, it blocks sugar uptake and so regulates blood sugar levels, which is great for diabetics.

The three steps of the transition phase are decarboxylation, oxidation and formation of acetyl CoA. Briefly describe each.

Decarboxylation occurs when a carbon dioxide is stripped off of the entering pyruvic acid. It is released. Oxidation: hydrogen and electrons are stripped off of what remains and they are added onto a NAD+ molecule, forming a NADH molecule. The result is acetic acid. Acetic acid combines with coenzyme a and produces acetyl CoA.

Contrast essential and non-essential nutrients.

Essential nutrients can't be made at all or fast enough by the body, so we have to get them from the diet. Non-essential nutrients can be made by the body in sufficient amounts if we don't include them in the diet.

Explain why, even when you don't eat lipids, but you eat a lot of carbohydrates, you store fat.

Excess carbs are first stored as glycogen, but after 2000 calories of glycogen are stored, any excess carbs are converted to fat and stored.

What happens to excess protein that's eaten?

Excess is converted to ATP if we need it and fat if you don't need it.

Name the functions of lipids in the body.

Fats help us feel satisfied and full by our meal, they form adipose tissue, protect and cushion organs, form phospholipids (which build cell membranes), form cholesterol (needed to make cell membranes), fuel skeletal muscle and liver cells and they help the body absorb fat soluble vitamins.

What are dietary sources of lipids? Saturated? Unsaturated?

Fats. Saturated fats come from animal products and so they include butter, eggs, all dairy, and the white fat within the meat you buy. Unsaturated fats come from plant sources and examples are seeds, nuts, olive and other cooking oils, avocado, fish.

Give examples of good fats.

Fatty fish like salmon, avocado, nuts, seeds, olive oil, and other cooking oils.

How does fiber relate to diabetes?

Fiber is a physical barrier to sugar absorption in the small intestine. So, if you eat sugar with some fiber, the sugar will be absorbed, but it will take longer. You end up getting a long, slow release of sugar over time, instead of a sugar spike. Sugar spikes lead to insulin release, which can lead to resistance to insulin and type II diabetes. Insulin causes cells to take up sugar and if you don't need it for fuel, it is stored as fat. So, fiber is good for weight control. Long, slow release of sugar keeps blood sugar levels stable over time, which is what we want.

What effect does glucagon have? What organ secretes it?

Glucagon is the main hormone being secreted (by the pancreas) during the post-fed state. This hormone stimulates the liver to release glucose (broken off of the glycogen stored there) into the blood when blood sugar levels start to fall. It also targets adipose tissues and stimulates them to break down triglycerides into glycerol and fatty acids. Glycerol is converted to glucose in the liver and fatty acids are converted to acetyl CoA.

During the absorptive state, what happens to glucose? Triglycerides? Amino acids?

Glucose is burned, stored as glycogen and then stored as fat if there is any extra. Triglycerides move through the body in chylomicrons. Lipoprotein lipase on the capillary walls of skeletal, cardiac muscle and adipose tissue breaks these down and these cells use fat as fuel. Other cell types will use fat for fuel when carbohydrates run low. Excess fat is stored. Amino acids help to re-build proteins that need replacing. They can be used for fuel if needed, but this is the last type of molecule that is used as fuel. Excess is stored as fat.

How does glucose interact with ATP when it first enters a cell?

Glucose picks up a phosphate from ATP forming ADP and glucose-6 phosphate.

Define these terms: glycogenesis, glycogenolysis, and gluconeogenesis.

Glycogenesis means building glycogen out of glucose (when we have more glucose than we need to burn at any given time). Glycogenolysis is splitting glycogen into glucose (when we need fuel). Gluconeogenesis is making glucose out of other things, like fat and protein, when we are out of glucose, but need energy.

What are the three steps of cellular respiration?

Glycolysis, Kreb's cycle and the ETS (electron transport system).

Give examples of good and bad carbohydrates. What are the advantages of good carbs?

Good carbs include fruits, veggies, beans, whole grains, organic dairy, and so forth - things with complex carbs or polysaccharides in them. These carbs release sugar into the blood slowly, instead of creating a blood sugar spike. Bad carbs are things made out of white sugar, white flour, rice or white potatoes. These cause blood sugar spikes and the problems I talked about in #58 associated with blood sugar spikes.

Define the term 'metabolism'.

Metabolism refers to the building up and tearing down of molecules in the body.

Where does glycolysis occur?

In the cytosol.

Explain the role of insulin during the absorptive state.

Insulin is the key hormone that is active during the absorptive state. Blood glucose levels rise after a meal. This stimulates the pancreas to release insulin. Insulin binds to cell membranes of the target cells. Glucose moves into these cells. Muscle and adipose cells are extremely sensitive to insulin.

When oxygen isn't present, what is produced?

Lactic acid.

What are the monosaccharides? Disaccharides? Polysaccharides?

Monosaccharides are single sugar units. Disaccharides are two monosaccharides linked together. Polysaccharides are many monosaccharides linked together. There are three types of monosaccharides: glucose, fructose and galactose. There are three kinds of disaccharides: lactose, sucrose and maltose. Sucrose is glucose and fructose linked together. lactose is glucose and galactose linked together. Maltose is glucose and glucose linked together. There are three polysaccharides: starch, cellulose and glycogen. Starch and cellulose are found in plants. Glycogen is found in animal sources.

What do we need/use vitamins for?

Most vitamins are co-enzymes. They bind to an enzyme to complete the enzymes final structure. Once that happens the enzyme is ready to do work. A,C, and E act as antioxidants, neutralizing free radicals. This has an anti-aging affect.

Is cholesterol required in the diet? Why?

No, because your liver can make all the cholesterol you need if you don't eat any.

What are two essential fatty acids? What food sources have these?

Omega 3 and Omega 6 fatty acids. Omega-3 can be found in fatty, cold-water fish, flaxseeds, walnuts....Omega-6 can be found in many cooking oils.

When oxygen is present, where to the extra electrons go? What is the final electron acceptor?

Oxygen is the final electron acceptor.

Give the overall equation for cellular respiration.

Oxygen plus glucose gives water, carbon dioxide and ATP.

How many calories per gram do carbs, proteins and lipids have?

Proteins and carbohydrates have 4 calories per gram and lipids have 9 calories per gram.

What's a simple carbohydrate? Complex?

Simple carbs are mono and disaccharides. Complex carbs are polysaccharides. Simple said, simple carbs are those made out of white sugar, white flour, white potatoes, white rice, and complex carbs come from whole grains, fruits, veggies.

How much protein do you need to eat every day?

Take your healthy weight and divide by 2.2. This gives you your weight in kilograms. Multiply that number by something between .8-2.0. Use .8 if you sit at a desk all day and don't get much movement at all. Use 2.0 if you are a professional athlete, moving at least 2 hours vigorously every day.

Explain how the molecules involved in the ETS are oxidized and reduced over and over. What molecules deliver the electrons? What role does H+ play? How is so much ATP made?

There are several protein molecules in the inner membrane of the mitochondria. NADH and FADH2 come here and deliver electrons to the first protein molecule. They are oxidized to NAD+ and FAD. The protein molecule that just received the electron was reduced (it's charge reduced). Now it has too many electrons and it's looking to get rid of that extra electron. It hops next door to the next protein molecule in the chain. The first molecule was oxidized (stripped of an electron) and the second was reduced (gained an electron). This electron hops along from one molecule to the next oxidizing and reducing as it goes. Finally, oxygen is reduced (accepts this electron) at the end of the chain of these protein molecules in the membrane. As the electron 'hops' from one protein to the next, energy is released. This energy is used to pump hydrogen from the matrix to the inner membrane space, where it accumulates. It is pulled back towards the matrix by a few things: its concentration gradient, the charge gradient (as positive charges build up in the inner membrane space, they are attracted to the more negative side of the membrane), and the decreasing pH. The only way for them to move across the membrane is for them to use a transport protein called ATP synthase. When H+ moves through this protein from the inner membrane space to the matrix, it stimulates an enzyme inside of the channel to make ATP out of ADP and P.

Describe how amino acids are broken down by the body.

There are three steps to amino acid degradation (break down). First, transamination. This is when an amine group is transferred from an amino acid to alpha-ketoglutaric acid. Alpha ketoglutaric becomes glutamate when the amine group is added. The amino acid that lost the amine group becomes a citric acid intermediate, so it can enter the cycle to make ATP. Second, oxidative deamination. In the liver, the amine group of glutamate is removed. This regenerates alpha-ketoglutaric acid. This can help deaminate another amino acid, or become a citric acid intermediate. Third, keto acid modification. The citric acid intermediate (also called a keto acid) can be modified to produce a molecule that can enter the citric acid cycle.

What happens to amino acids that aren't used right away?

They are converted to fat and stored.

What happens to the other types of monosaccharides once eaten?

They are converted to glucose and then: burned, stored as glycogen, stored as fat (in that order).

What happens to excess glycerol and fatty acids? Where are they stored?

They are reassembled into triglycerides and stored as fat.

What do proteins do in the body?

They build body structures like hair, nails, ligaments, tendons, muscles. They act as enzymes, hormones and they are burned for energy during starvation.

What's the protective function of glyconeogenesis?

This protects our brain, which can only run on glucose. So, if we run out, there is a way to make more.

How much protein do you need to eat every day? What are ways you can get it at each meal?

To figure out how much protein you need, take your healthy weight, divide by 2.2 and then multiply the number you get by .8-2.0 depending on your activity level. You can get this by eating animal products (meat, dairy, eggs) or plant proteins (beans, whole grains, nuts and seeds).

If you don't eat enough carbohydrates fat is used for fuel. Explain how this happens. What tissues burn fat? Which depend on glucose?

Triglycerides are converted to acetyl CoA, when enters the Krebs cycle and then we get ATP from that. Skeletal muscle and cardiac muscle use fats for fuel this way, but the brain depends on glucose only.

What are the products of the electron transport system (ETS)?

Water (formed from oxygen binding to the electrons that are coming through the ETS), NAD+, FAD, ATP.

Why doesn't unlimited glucose lead to unlimited ATP?

We only build as much ATP as we need to burn at any given time because we can't store ATP. If we don't need it, then the extra glucose is first stored as glycogen and then stored as fat. Glycogen supply fills up at 2000 calories.

This is the monomer for proteins:

amino acids

A saturated fat has

no double bonds in the carbon chain