Download LESSON 2.5 WORKBOOK Blood glucose in sleep, a 5 mile

LESSON 2.5 WORKBOOK
Blood glucose in sleep, a 5 mile
run…and after that Big Mac
Using the things we have explored throughout Unit 2, in
this lesson we will expand upon our knowledge of how the
metabolic pathways affect specific body systems. We will
focus on which organs are primarily involved in each metabolic pathway, and relate this to how the body maintains
blood glucose homeostasis under three conditions: fasting,
feasting and exercise. We will link the steps in metabolism
that we have learned to real life experiences, and apply this
knowledge to understand potential lifestyle changes.
Now that we have an idea of how the body maintains glucose homeostasis, lets apply that knowledge
to some real-life situations. We will use two characters, Edna and Mimi, as example of how metabolism
changes depending on the food that we eat and our physical activity levels.
The metabolism of Mimi
We will begin by following our first character, Mimi, through a normal day. Mimi is a high school student that
spends her time socializing with friends or studying. The food that she eats and the exercise she does are
listed below.
Wo r k b o o k
Lesson 2.5
Time
Activity
Metablic Response
Organs Involved
7:00 am
After a full night’s
sleep Mimi wakes
up and eats a
bowl of frosted
wheat cereal with
fat free milk for
breakfast.
Mimi’s glycogen stores were
being used up while she slept,
so the sugars from the cereal
will replenish those stores. Any
extra glucose will be converted
to fat and stored.
• The pancreas senses the glucose and releases
insulin.
• The liver and muscle store glucose as glycogen.
• The liver converts extra glucose to triglycerides,
which are stored in the adipose.
• Amino acids from the milk will be used to make
new proteins.
1. What is the main source of energy
used while you sleep?
aa. Amino acids.
bb. Fatty stores.
cc. Glycogen stores.
dd. No energy is used while you
sleep.
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99
LESSON READINGS
Time
Wo r k b o o k
Lesson 2.5
Activity
Metablic Response
Organs Involved
10:00 am Mimi gets hungry
so she eats
a serving of
flavored yogurt.
Because of her high sugar
breakfast, Mimi’s blood
glucose levels have already
peaked and are lowering,
making her hungry. The fat,
protein and sugar of the yogurt
will mostly go into storage.
• The pancreas senses the glucose and releases
insulin.
• Some glucose will be stored as glycogen, but
most of it will get converted to triglycerides and
stored in the adipose.
• The fat will get stored as triglycerides.
• Amino acids will be used to make new proteins.
1:00 pm
Mimi eats a
cheeseburger
and drinks a soda
for lunch.
This meal is made up of
carbohydrates, protein and
fat, and because her glycogen
stores haven’t been used up,
energy from this meal is largely
stored as fat.
• The pancreas senses the glucose and releases
insulin.
• Almost all of the glucose will get converted to
triglycerides and stored in the adipose.
• The fat will get stored as triglycerides.
• Amino acids will be used to make new proteins.
3:00 pm
Mimi rides her
bike around her
neighborhood for
30 minutes.
Glucose that is already in the
blood will get used up first to
release energy for exercise.
Some glycogen stores may be
broken down if blood glucose
is not enough.
• Exercise acts like insulin and brings glucose into
the muscle cells to be used.
• Glycogen from the liver and muscle will be
broken down.
7:00 pm
Dinnertime!
A bean, rice,
cheese and
vegetable burrito
is for dinner
tonight.
The fiber from the beans and
vegetables will help slow the
digestion and absorption of
the carbohydrates, protein and
fat in this meal. The glycogen
that was broken down during
Mimi’s bike ride is replenished.
Extra energy goes into Mimi’s
fat stores.
• The pancreas senses the glucose and releases
insulin.
• Some glucose will be stored as glycogen, and
some will get converted to triglycerides and
stored in the adipose.
• The fat will get stored as triglycerides.
• Amino acids will be used to make new proteins.
9:00 pm
Mimi eats a bowl
of ice cream for
dessert.
Mimi hasn’t done anything to
burn off her dinner, so nearly
all of the energy from the ice
cream is stored as fat.
• The glucose is converted to triglycerides in the
liver and stored in the adipose.
• The fat will get stored as triglycerides in the
adipose.
2. Where do muscles get glucose
during exercise?
aa. From their own glycogen stores.
bb. From the livers glycogen stores.
cc. From gluconeogenesis.
dd. All of the above.
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100
LESSON READINGS
The case of exercising Edna
Edna is also a high school student, and is very active! Edna is on the cross-country team and loves to run.
Because Edna exercises regularly she has more muscle mass than Mimi. This means that Edna will burn
more energy to maintain her weight than Mimi, and will use up her glycogen stores quicker. Muscles need
glucose to make ATP to be able to contract. Once the available glucose in the blood is used up, other
sources of glucose are used. Muscles will also rely on fatty acids for energy once the glucose is gone, but
producing ATP from fatty acids takes much longer than from glucose, so fatty acids will only be used after
the quick sources of energy (glucose and glycogen) are exhausted.
Using the table below we can follow Edna through her day. To learn more about the effects of exercise on
metabolism read the notes below the table that are marked with either a * or **.
Wo r k b o o k
Lesson 2.5
Time
Activity
Metablic Response
Organs Involved
6:00 am
Edna wakes up
early and runs a
mile before going
to class.
Glycogen stores were already
being used up as Edna slept,
so energy for her run comes
from gluconeogenesis and
breaking down amino acids
and triglycerides.
• The pancreas senses low glucose and releases
glucagon.
• Exercise causes glucose to enter muscle cells**
• The liver and muscle break down glycogen into
glucose.
• The liver converts amino acids, lactic acid* and
triglycerides to new glucose.
• Triglycerides are broken down into glycerol and
fatty acids and released from the adipose.
7:00 am
For breakfast
Edna eats a
protein shake and
a banana.
This is a low carbohydrate
meal, but Edna’s glycogen
stores are getting low!
Fructose from the banana will
be converted to glucose in the
liver and stored. Amino acids
and triglycerides are used in
gluconeogenesis.
• The pancreas senses the glucose and releases
insulin.
• Glycogen stores in the liver and muscle will be
filled up.
• Amino acids will be used to make new proteins.
1:00 pm
At lunch Edna
eats the same
things as Mimi:
a cheeseburger
and a can of
soda.
Because Edna burns glucose
faster than Mimi, her glycogen
stores are already being used
by lunch. The glucose replenishes glycogen stores, and the
fat will be used both for energy
now and stored for later.
• The pancreas senses the glucose and releases
insulin.
• The glucose will replenish glycogen stores and
be used for energy now.
• The fat will be used for energy and get stored as
triglycerides.
• Amino acids will be used to make new proteins.
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101
LESSON READINGS
Time
Activity
Metablic Response
Organs Involved
3:00 pm
Edna skips an
afternoon snack
to go to her
one-hour crosscountry practice.
Glycogen will be broken down
to glucose during practice.
By the end of practice Edna’s
glycogen stores are used
up and her liver is creating
new glucose for her muscles.
Glucose is made from amino
acids as well as from the lactic
acid being produced in her
muscles*.
• Exercise acts like insulin and brings glucose into
the muscle cells to be used.
• Glycogen from the liver and muscle will be
broken down.
The fiber from the vegetables
will help slow the digestion and
absorption of the carbohydrates, protein and fat in this
meal. The glucose from the
starch in the baked potato
replenishes the glycogen
that was broken down during
exercise. Extra energy goes
into Edna’s fat stores.
• The pancreas senses the glucose and releases
insulin.
• Most glucose will be stored as glycogen.
• The fat will get stored as triglycerides.
• Amino acids will be used to rebuild the proteins
that were broken down during exercise.
DEFINITIONS OF TERMS
7:00 pm
Lactic acid — An acid containing three carbons that is formed
in the muscles during strenuous
exercise.
For a complete list of defined
terms, see the Glossary.
Wo r k b o o k
Lesson 2.5
For dinner Edna
eats a baked
potato, green
beans and
roasted chicken
breast.
*Lactic acid can be used to make glucose
During exercise the rate of the citric acid cycle can’t
always keep up with the amount of glucose that is
being supplied to the muscles. This is because the
citric acid cycle requires oxygen to be delivered from
the lungs via the blood. During anaerobic exercise
like running or dancing you breathe heavily because
not enough oxygen is being supplied to your brain
and muscles. The citric acid cycle slows down and
molecules from glycolysis build up, namely pyruvate.
(Pyruvate is the molecule in the last step of glycolysis
before acetyl CoA is made.) Pyruvate is converted into
lactic acid, which causes the burning sensation you
may feel in your muscles during exercise. Lactic acid
can be converted back to glucose in the liver, where it
is re-released into the blood.
• Proteins in the muscle will break down to
release amino acids.
• The liver will make new glucose from amino
acids, lactic acid and fat.
Figure 1: During exercise glucose
can be converted into lactic acid, or
lactate in the muscle because of limited
oxygen. This is transported to the liver
where it is converted to glucose through
gluconeogenesis.
3. Why do we breath heavier during
strenuous exercise?
aa. To increase oxygen for
glycolysis.
bb. To increase oxygen for the citric
acid cycle.
cc. To breathe out lactic acid.
dd. All of the above.
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LESSON READINGS
**Exercise can act like insulin
The act of using your muscles can trigger a response that is similar to the effects of insulin. We previously
learned that insulin tells the liver to store extra energy. Insulin also has an important role in the muscles: to
bring glucose into the cells so that it can be used. During exercise, glucose from the blood can be brought
into the muscle cells without the aid of insulin. This is important for people who are living with diabetes and
do not have normal absorption of glucose. In this way, incorporating exercise into their daily routine can
help regulate the blood glucose concentrations of someone with diabetes.
Wo r k b o o k
Lesson 2.5
4. Which of the two characters likely
burns more calories in a day?
aa. Mimi.
bb. Edna.
cc. They are likely the same.
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103
STUDENT RESPONSES
What would the difference in glucose homeostasis be if someone were to go for a long run in the morning before they ate
anything, compared to running an hour after eating lunch?
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Wo r k b o o k
Lesson 2.5
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TERMS
TERM
Lactic Acid
DEFINITION
An acid containing three carbons that is formed in the muscles during strenuous exercise.
For a complete list of defined
terms, see the Glossary.
Wo r k b o o k
Lesson 2.5
105