Download Chapter 24 - WordPress.com

Lecture – 23
(24)
Nov. 9, 2011
Nutrition, Metabolism, and Body Temperature Regulation
Food provides: proteins, carbohydrates, lipids, vitamins and minerals.
What elements are found in carbohydrates? Carbon – Hydrogen – Oxygen
Where does nitrogen and sulfur come from? Proteins
Where does phosphorous come from? Fats – oils, plant oils
Food supplies us energy…
How much energy is enough? The body is aware of the threshold needed for ATP production, the
balance is stored as adipose tissue. Adipose tissues can be made from lipids, proteins, or carbs.
The pathways breakdown of food components can be obtain from various sources and converted to
other components.
Pg. 915 Vitamins function as co-enzymes – many of the B vitamins works with energy metabolism
Most vitamins function as co-enzymes, which act with an enzyme to accomplish a particular chemical
task. For example, the B vitamins act as coenzymes in the oxidation of glucose for energy.
Pg. 917 Minerals also function as co-factors; many trace minerals/elements
The body requires moderate amounts of seven minerals (calcium, phosphorus, potassium, sulfur,
sodium, chlorine, magnesium) and trace amounts of about a dozen others.
Pg. 918 Metabolic Reactions
Anabolism – is the general terms for all reactions in which larger molecules or structures are build
from smaller ones.
Catabolism – refers to all processes that break down complex structures to simpler ones
Cellular Respiration – a collection of catabolic reactions ― food fuels, particularly glucose, are broken
down in cells and some of the energy released is captured to form ATP, the cells’ energy currency.
Pg. 920 Three Stages of Metabolism of Energy-Containing Nutrients
Stage 1: Digestion in the GI tract lumen to absorbable forms; transport via blood to tissue cells
Stage 2: Anabolism (incorporation into molecules) and catabolism of nutrients to form intermediates
within tissue cells.
** Note Stage 1 & 2 do not use oxygen  therefore are anaerobic processes
1
Stage 3: Oxidative breakdown of products of stage 2 in mitochondria of tissue cells; CO2 is liberated,
and H atoms removed are ultimately delivered to molecular oxygen, forming water. Some energy
released is used to form ATP.
Stage 3 involves the Krebs cycle – electron transport chain [yielding more ( ATP by utilizing O2]
When proteins are broken down  ammonia (NH3) is a by-product that must be eliminated/urine
Glycolysis – anaerobic respiration – a process that occurs in the cells cytoplasm
Krebs Cycle – aerobic process occurs in the mitochondria
Pg. 932 – Can adipose tissue enter into this energy metabolism path way and become ATP? YES
Pg. 936 – Arrow Game
Is there a path way where proteins can be converted to fats? YES
Can proteins be converted to carbohydrates? YES – called gluconeogenesis (creation of new glucose)
Can you make glucose out of fat? YES
Can you take fats and somehow turn them into proteins? YES – convert to carbohydrate first
THEY CAN ALL BE INTERCONVERTED FROM ONE TO ANOTHER – ALL CAN ENTER INTO KREB CYCLE
Meats are complete proteins – no additional proteins sources are needed for essential amino acids.
Vegetarians must eat rice & beans together in order to get all of their essential amino acids
Essential amino acids are those that the body cannot make on it own, must be obtained from food
sources.
Pg. 940 – Glucose Sparing [memorize]
Glucose Sparing – The increase use of non-carbohydrate fuel molecules, especially triglycerides, to
conserve glucose.
With regards to prolong fasting, as the body progresses from the absorptive to the post-absorptive
state, the brain continues to take its share of blood glucose, but virtually every other organ switches to
fatty acids as its major energy source, sparing glucose for the brain. During this transition phase,
lipolysis begins in adipose tissues and released fatty acids are picked up by tissue cells and oxidized for
energy. In addition, the liver oxidized fats to ketone bodies and releases them to the blood for use by
tissue cells.
If fasting continues for more than 4-5 days, the brain will also begin to utilize fatty acids as well as
glucose in order to preserve protein (muscle) tissues.
2
Complex carbohydrates have a lower glycemic index value.
Simple carbohydrates have a higher glycemic index value.
Glycemic index is measure of what happens to blood sugar when you eat a particular kind of food
Whole grains are better.
Vegetables are better.
Sweet potato has a lower glycemic index compared to Irish potato.
Pg. 946 Many hormones are involved in Satiety signals.
Farm foods – unprocessed foods are higher in Potassium than Sodium
Processed foods are much higher in Sodium.
If Sodium intake is reduced  BP falls almost immediately
Eat fruits and vegetables and you’d be fine.
3