Chapter 17 Nutrition and Metabolism

Use the diagrams in the book to enhance comprehension of these concepts.

This chapter is presented in conjunction with Chapter 3, Cells, because the flow of energy and nutrients are controlled at the cellular level.  This topic will be reviewed again, when the Digestive System is covered.

        98.6 F is the average.
   97.4 to  100.1 F is the range.

Define ‘average’ and ‘range’.
  How does 'range' relate to homeostasis?
    How does 'average' relate to set point?
List some negative feedback mechanisms that support the 'norm' for body temperature.
   Hint: Chapter 5, Integumentary System discusses what happens when the body gets too
     hot and too cold.

Metabolism is the sum of all the chemical reactions in the body. Reveiw Chapter 1.

There are two main types of chemical reactions

Catabolism – breaking down a molecule.
Anabolism – synthesizing a molecule.

What is an enzyme?
  How are enzymes related to metabolism?
     Review Chapter 2 and 3.

Heat is generated in the body through aerobic cellular respiration which is the metabolic breakdown of glucose so that the energy can be transferred to ATP. About 40% of the energy in a glucose molecule is captured as ATP – the other 60% is lost as heat.

Most heat is produced during muscle contractions because so much ATP is needed for that process. The human body uses that heat energy to maintain a normal, homeostatic body temperature.

When a person becomes cold, he starts to shiver, which is small, quick, skeletal muscle contractions. This produces heat in a process called Shivering Thermogenesis.

Heat is lost from the body in 4 ways:

Conduction – the transfer of heat energy from one solid to another or from one molecule to another. When two people hug each other to stay warm, they are conducting heat between their bodies. When a can of soda becomes warm while being held, the heat of the hand is conducted to the cooler soda.

Convection – is the movement of warm molecules away from a hot surface to a cooler area. Air molecules next to the skin are warmed by conduction of heat from the body. The warm air molecules are lighter than the surrounding cool air molecules and move away from the body and cooler molecules come in contact with the body.

Evaporation – is the loss of heat by converting liquid water to water vapor, which moves away from the body by convection. Remember that water has a high specific heat capacity? Water must absorb a LOT of heat to change from the liquid state to the gaseous state. When this happens, a LOT of heat energy is removed from the body.

Radiation – is the loss of heat in waveform. Picture the radiant heaters you can buy and plug into an electric wall plug. The heating ‘element’ starts off brownish gray and heats up to a glowing red. When it glows, you can ‘feel’ the heat even without a fan to blow the heat toward you. This radiation is infrared (IR) radiation. It is the same energy that is sensed by IR night vision goggles used by the military.

Describe the mechanism that produces heat.
     See the description of aerobic cellular respiration on this page.
  Where does this mechanism take place?
     Which parts of this process occur in the cytoplasm?
        Which parts occur in the mitochondria?
How much energy (percentage) is captured as ATP?
   How much (percentage) is 'lost' as heat energy?
      How does the body use this 'lost' energy?
         What is 'shivering thermogenesis?
Describe the mechanisms by which the body loses heat energy.

The hypothalamus houses the temperature control centers of the Autonomic Nervous System.
It controls the balance between heat generation and heat loss.

Describe the two Water Compartments

Review Chapter 2, the two locations of WATER
  Compare and Contrast Intracellular (ICF) vs. Extracellular (ECF)
    The Na/K pump causes a high concentration of Na+ in the Extracellular fluid
         and a high concentration of K+ in the Intracellular fluid.

What does the Na/K pump cause ECF and ICF to contain?

Review the Na/K pump.

Nutrition is the absorption of nutrients

There are 6 basic nutrients divided into 2 groups

Organic molecules:
     proteins
     lipids
     carbohydrates.
These nutrients must be broken down into their repeating units that are small enough to be absorbed.  They are modified after being absorbed so that they can be used. The 'repeating units' of each OM serve as building blocks for new molecules synthesized in the body. 
Carbohydrates and lipids are the energy source for the body.

H₂O, minerals and vitamins. These nutrients are used in the form they are absorbed (they are not modified before use). Minerals (see the list of ions in the body) and Vitamins function as coenzymes and cofactors in metabolic reactions. They support and facilitate the chemical reactions of the body.

Vitamins and minerals support and enhance the activity of enzymes.
Minerals are ELEMENTS -see the periodic table of the elements-.
     They are absorbed as ions, and are also called electrolytes and solutes.

Ca++ - a cation that is essential for muscle contraction, nerve function, and blood clotting.
Na+ and K+ - sodium/potassium pump.  Maintains the normal membrane functions.
Mg+ - cofactor for enzymes
Fe - important component hemoglobin and myoglobin for oxygen binding.

Essential nutrients - amino acids and lipids that must be present in the DIET.
      Your body cannot synthesize these molecules - you MUST find them and eat them.
              Essential Amino Acids
              Essential Fatty Acids

Fat soluble vitamins - Vitamin A, D, E, and K.  (hint: spells ADEK)
     These vitamins dissolve into droplets of lipids in the food, and are absorbed along with the fat droplets. 
      Low-fat diets run the risk of causing a deficiency of fat soluble vitamins.
      Problems absorbing fats in the intestine would interfere with the absorption of fat-soluble vitamins.

List the Fat soluble vitamins.
  How are these vitamins absorbed?
    Why are these molecules able to dissolve in fat? (hint – fat is a NONpolar molecule)

List the water soluble vitamins.
  Why are these molecules water soluble?
        Hint: are they polar or nonpolar?
    What is the function of water in metabolism?
List the characteristics of water.

      Describe the Lipoproteins and Cholesterol

Cholesterol is synthesized in the liver.
     -  ESSENTIAL for proper cell membrane functions (regulates the fluidity of the CM).
     -  used by the endocrine glands to produce a class of fat derived hormones such as:
        estrogen, progesterone, testosterone, glucocorticoids, corticosteroids, etc

LDL - Low density lipoproteins
    Carry cholesterol from the liver to the cells in the peripheral tissues  - where hormones and
       cell membranes are being synthesized.

HDL - High density lipoproteins
    Carry excess cholesterol from the peripheral tissue back to the liver.

What is the function of LDL?
What is the function of HDL?

What is the function of the Organic Molecules as nutrients?

Remember - from Chapter 1.

Now- where do we get energy?
  How is that energy 'stored'?
   How do we 'release' the stored energy?
    What is the USEABLE form of energy in the body?

so... back to the most important questions:
  How do we RELEASE stored energy and
    What is the form of useable energy?

Cellular respiration is:
the transfer of stored energy from glucose to useable energy in ATP

There are two types of cellular respiration:
    Anaerobic - without oxygen.
         Produces 2 (two) useable ATPs.  This is NOT enough energy produced to sustain the life
           processes (metabolism) - the organism dies of asphyxiation.
    Aerobic - WITH oxygen.
         Produces 38 ATP.  HUMAN cells must produce at least 36 ATP from each molecule of glucose
            to sustain life processes (metabolism).

KNOW this formula! This is the simple formula for aerobic cellular respiration.
 

The useable product is ATP, which the body uses to energize metabolic reactions.
   ATP is a molecule that contains LOTS of energy that is easily used by chemical reactions in the body.
     - Aerobic cellular respiration transfers STORED energy from glucose to ATP.
        - Glucose is the energy storage molecule - lots of energy BUT in a stable, non-useable form
        - ATP - the UNSTABLE molecule with energy that is easily used

The WASTE products are
    - CO₂ which the body releases from the lungs,
    - H₂O which the body uses in other metabolic reactions or excretes as either sweat or urine or
        in the feces.
    - heat energy

About 40% of the energy in a glucose molecule is captured as ATP. The other 60% is lost as HEAT. We use this (waste energy) heat to help us maintain the normal body temperature.

List the three steps of Aerobic Cellular Respiration.
  What are the products of each step?

What percentage of the energy in a glucose molecule is transferred to ATP?
    What percentage is NOT transferred to ATP?
      What happens to the energy that is NOT transferred to ATP?
         How do we 'use' this 'waste' energy?
Which step of Cellular Respiration occurs both without or with O₂?
Which step produces pyruvic acid?
Which step produces CO₂?
Which step produces ATP?

Glycolysis – occurs in the cytoplasm, whether O₂ is present or not.
    glyco - refers to glucose
       -lysis - means 'to break'     -  therefore, glycolysis is literally 'breaking sugar' apart.

During Glycolysis, one glucose (a 6 C molecule) molecule is broken down into two pyruvate (3 C each) molecules.
       Pyruvate is also called pyruvic acid

Glycolysis produces 2 ATP

IF O₂ is absent, then the pyruvate is converted to Lactate and the process stops for this molecule.
    What does ‘anaerobic’ mean?

IF O₂ is present, the pyruvate goes into the mitochondria and to the Krebs cycle (TriCarboxylic Acid -TCA), and the pyruvate is further decomposed into CO₂ and the energy transferred to ATP molecules.

During TCA, which occurs inside the mitochondria, pyruvate (a 3 C molecule) is broken down into 3 (three) CO₂ (1 C) molecules and transferring energy to ATP, NADH₂ and FADH.

The NADH₂ and FADH go into the Electron Transport process which occurs inside the mitochondrion, transferring electrons from one molecule the next. As the electrons are passed along the chain of protein molecules, the energy is used to pump H+ across the inner membrane of the mitochondrium creating a high concentration of H+ inside the inner membrane. When the H+ then diffuse through the ATP-ase channels to get out of the inner membrane, that kinetic energy is transferred to ATP molecules.

NAD and FAD are electron TRANSPORT molecules.

36 ATP are produced by Krebs and the Electron transport system. This is aerobic and occurs in the mitochondrion. Only 2 ATP are produced by glycolysis – for this reason, mitochondria are called the ‘powerhouse’ of the cell.

**NOTE*** in aerobic cellular respiration:

1.  An Oxygen atom accepts the electrons in the very last step of aerobic cellular respiration and
      combines with H’s to form H₂O.

  Oxygen is the final electron acceptor.

2.  Glucose is broken down into CO₂

3.  The energy from the glucose is transferred to ATP (40%) or lost as heat (60%).

How is energy transferred from one atom or molecule to another atom or molecule?
   by transferring the ELECTRONS!

What is the function of NAD and FAD?
   They 'carry' electrons from one atom/molecule to another in the process of cellular respiration.
     Why?
       Because they contain the energy that is to be transferred to the ATP.
What is the function of OXYGEN?
   It is the FINAL electron acceptor.  As electrons are 'carried' and 'passed' along the electron transport chain, a sequence of molecules 'accept' the moving electrons and pass the electrons on to the next molecule.  At the end of the line - the electron is passed to an Oxygen.

Review Chapter 2, Chemistry.
The Oxygen atom has 8 protons in the nucleus - and therefore 8 electrons orbiting the nucleus: 2 in the inner shell and 6 in the outer 'shell'.  It WANTS 2 more electrons badly - so badly that it will literally RIP electrons from other atoms. 

This 'characteristic' of oxygen - wanting electrons badly - is USED by aerobic organisms to extract lots more energy from organic molecules.   Remember: anaerobic cellular respiration releases 2 ATP, while aerobic cellular respiration releases 38 ATP.
      2 ATP vs. 38 ATP.

Atoms and molecules that lose electrons to Oxygen are said to be 'oxidized'.  Oxygen has
    taken an electron - which gives the 'loser' a POSITIVE electrical charge.
        Rust is Fe that has lost an electron - Oxidation.
Oxygen has extra electrons - which gives it a NEGATIVE electrical charge - i.e. it's electrical charge is 'lower' or 'reduced' - and therefore oxygen is said to have been 'reduced'.

Oxidant - any molecule (but primarily the oxygen atom) that WANTS electrons badly.

Now,
   any molecule that loses an electron is said to be oxidized (whether the electron went to
       oxygen or not)
   any molecule that receives an electron is said to be reduced.
RedOx reactions - chemical reactions in which an electron is stripped from one molecule and transferred to another.

Metabolism - aerobic - creates 'Oxidants' - molecules that 'badly' want an electron and will RIP it away from other molecules.  Ripping the electrons away, damages the other molecules such that they do not function properly.

Because oxygen wants electrons so badly that it will literally rip them away from other
   molecules, oxygen is actually DAMAGING the other molecules and is therefore TOXIC,
   or a poison.
Anti-oxidant is an atom or molecule that easily releases electrons to oxygen, thereby preventing the oxygen atom from damaging other molecules (and therefore cells and tissues).

Define oxidation, oxidized, reduced, RedOx reaction, and antioxidant.
What is 'rust' (as in iron that is 'rusted')?

A calorie - a measure of the energy content of foods.

One calorie is the amount of energy that will raise the temperature of 1 gram of water, 1 degree C.

One kilocalorie is the amount of energy that will raise the temperature of 1000 g of water, 1 degree C. (Kilo means 1000. One kilometer is 1000 meters, 1 kilocalorie is 1000 calories).

A kilocalorie is written on the food guides as C  (upper case C).

A candy bar with 440 C (Note the capital C = kilocalorie!) contains 440,000 calories. Or enough energy to raise the temperature of 440,000 grams of water, 1 degree C.
How can we USE this information?

Now, 1000 grams of water = 1000 ml of water = 1 liter of water = 1 kilogram of water

1 kg = 2.2 lbs,

ASSUMPTION: the human body is 90% H2O, and therefore we can ASSUME that the body is all water (100% water).

a man that weighs 220 lbs therefore weighs 100 kg. 
        (220 lb X 1 kg/ 2.2 lb; the lb's cancel and we get 220 / 2.2 = 100 kg)
Since 1 kg of water weighs 1000 grams - the man weighs 220,000 g.

A candy bar with 440 Calories has enough energy to raise the temperature of a 220 lb man by 2 degrees C!

What is a calorie?
Define 'kilo'.
  What is a kilocalorie?
    What is a kilogram?

NOTE: the average daily caloric intake (food nutrition labels) is
   2000 C = 2000 kilocalories

2000 X 1000 = 2,000,000 calories

Why do we need all that energy?

Fats contain about 9.5 kilocalories of energy per gram

Carbohydrates (glucose) contain about 4.2 kilocalories of energy per gram

Proteins contain about 4.3 kilocalories of energy per gram

The important thing to note is that Fat contains twice as much energy per unit mass as proteins or carbohydrates.

What is the most efficient molecule for energy storage?
   What is the most common 'weight' problem?
      Hint: Too much 'fat' or too much 'protein?

Why is this the most common 'weight' problem?
   Hint: what is the most efficient way to store energy?

Basal Metabolic Rate (BMR) is a measure of the energy used by a person at rest during a unit of time.

It is about 70 C/hour or about 1800 C/day.

The BMR depends on:
   Physical condition - folks who are in good shape have more muscle - maintaing muscle burns more
       calories than maintaing fat.  
   Gender - men typically have more muscle than women - muscle needs more calories
   Ethnicity - genetic differences in metabolism
   Age - babies have really HIGH metabolism because they are growing.
   Body weight - moving mass around requires energy - big folks need more energy than little people.
  

What are the two water compartments in the body?
Intracellular - water is INSIDE the cell; enclose within the cell membrane
Extracellular - water OUTSIDE the cell membrane.

See the prior discussion in Chapter 3, Cellular transport mechanisms, on
   Diffusion,
   Osmosis,
   Active Transport.

The cell membrane prevents the 'passive' movement of atoms and molecules - therefore the concentration of solutes on one side of the cell membrane is different than on the other side.

Water moves (osmosis) to the solution with the HIGHEST concentration of solutes.

Define Osmosis

Explain why water is moving toward the solution with the highest concentration of solutes.

Water is gained by the body in 3 ways
   - Drinking supplies about 40% of the water needed by the body per day.
   - Eating supplies about 48% of the water needed by the body per day.
   - Metabolism (cellular respiration) creates about 12% of the water needed by the body per day.
        (remember: water is an 'essential reactant'?)

Water is lost by the body through several processes.
   - Urine
   - Sweat
   - Evaporation
   - Feces

The total water lost per day is about 2.5 liters.

This is the Simple formula for Cellular Respiration: KNOW IT!