Exam Two Study Guide Part Three

Question 1

Why is it correct to say that refined sugars such as pure sucrose, pure glucose, pure fructose, or high fructose
syrups are unhealthy if consumed in anything greater than small amounts?

Answer 1

a. Refined sugar is easily and rapidly digested and absorbed, causing spikes/surges in blood sugar levels if
consumed in more than small to moderate amounts

b. A surge of glucose can overwhelm our supply of insulin, causing damage to blood vessels & nerves

c. Liver cells are the only cells in our bodies that metabolize fructose, and refined sugar is 50% fructose, so
too much fructose can overburden the liver and cause fatty liver disease

Question 2

Why is it nonsense for someone to say that sugar is poison?

Answer 2

because glucose, which is a sugar, is the energy source our cells tend to prefer, and it’s the energy
source required by cells of our central nervous system (i.e., brain, spinal cord, etc.).

Question 3

Which organ detoxifies the ammonia, which is a by-product created when cells metabolize a protein’s amino
acids?

Answer 3

Liver. The liver converts ammonia into urea

Question 4

Where does most absorption of the molecules we eat occur?

Answer 4

Small intestine

Question 5

Why is eating too much protein unhealthy?

Answer 5

ammonia created by metabolism of amino acids that make up protein
overwhelms and damages the liver and kidneys.

Question 6

Where do amino acids and monosaccharides go after they are absorbed by small intestine cells?

Answer 6

Liver

Question 7

Where does fat go after it’s absorbed by small intestine cells?

Answer 7

Lymphatic System (then to blood, liver, etc.)

Question 8

How much energy is contained in carbohydrates, protein, and lipids?

Answer 8

carbs 4 kilocalories per gram (kcal/g); protein 4 kcal/g to 6 kcal/g; lipids 9 kcal/g

Question 9

Metabolic rate is a measure of how much energy our body uses up per unit time (e.g., kcal per hour). What
factors affect our metabolic rate, how do they affect it, and how relevant is behavior?

Answer 9

lean body mass and thyroid hormones affect metabolic rate.

• metabolic rate increases with an increase in lean body mass (i.e., with an increase in muscle per unit
  body weight). This factor can be meaningfully modified by behavior.
• metabolic rate increases with increases in two hormones produced by the thyroid gland (thyroxin and
  triiodothyronine). Behavior has little effect on levels of these hormones, but behavior can—to a
  moderate extent—counteract some effects caused by abnormalities in levels of these hormones.

Question 10

what factors affect our appetite?

Answer 10

-the hormone leptin is produced by fat cells and decreases appetite

-the hormone ghrelin is produced by stomach cells and increases appetite

-habits and emotions affect hormones and neurotransmitters and therefore appetite

Question 11

A protein is a large molecule that is made of a bunch of small molecules that are hooked together. If you
think of a protein as a chain, then each link of the chain is an amino acid. The enzymes pepsin (in the
stomach) and trypsin (in the small intestine) digest protein by breaking the bonds that bond one amino acid to
another. So, after these two enzymes and at least one other enzyme, peptidase, digest a protein, you’re left
with a bunch of single….?

Answer 11

Amino Acids

Question 12

So, when you see TV ads and internet Ads claiming that a capsule or pill containing fat burning
enzymes will melt your fat away if you just buy and swallow the capsules or pills, how do you know the claim
is nonsense?

Answer 12

.because 1) the enzymes can’t be transported from the digestive tract into our cells, and 2) enzymes
in the capsules or pills will be digested by our protein-digesting enzymes, pepsin and trypsin, leaving only a
soup of amino acids.

Question 13

If a person lacks
the enzyme sucrase, which is normally found in the lining of our small intestine, will the person be able to digest sugar sucrose?

Answer 13

No

Question 14

If a person
digests one molecule of sucrose (i.e., table sugar), what two, single molecules remain in the lumen (i.e., the
open space) of the person’s small intestine?

Answer 14

Glucose and Fructose

Question 15

Explain why it is incorrect to think or say people digest fructose or that we digest
glucose.

Answer 15

We absorb them as they are. We have a protein in the membrane of small intestine cells that is
designed to absorb fructose. Ditto for glucose.

Question 16

In other words, where’s the first place a glucose or a fructose
molecule goes in the process of being “absorbed”?

Answer 16

…absorbed into a cell at the lumen surface of the small intestine

Question 17

So, after amylase digests
starch, you’re left with a bunch of single….?

Answer 17

Glucose Molecules

Question 18

what happens to all the single glucose molecules that remain after starch is
digested by amylase in the small intestine? In other words, where’s the first place they go in the process of
being “absorbed”?

Answer 18

.absorbed into a cell at the lumen surface of the small intestine

Question 19

where’s the first place the single amino acids go in the process of being “absorbed”?

Answer 19

.absorbed into a cell at the lumen surface of the small intestine

Question 20

What happens to an item you swallow if none of your digestive system’s enzymes are able to chemically react
with the item, and if none of the cells in your digestive system are able to absorb the item or the molecules
that form the item?

Answer 20

the items is excreted as feces (i.e., you’d poop it out)

Question 21

We’re able to grind cellulose into miniscule bits with
our teeth and create a soup out of it in our stomach. Despite this fact, we’re unable to digest it. If grinding
it to bits with our teeth and then turning it into a soup in the stomach isn’t “digesting” it, what is?

Answer 21

breaking the chemical bond that connects one glucose molecule to another glucose molecule along
the length of a cellulose fiber would be “digestion” of cellulose.