Anatomy & Physiology 34B Lecture
Chapter 24 – Metabolism & Energy Balance
I. Overview
A. Energy Balance
B. Metabolism
C. Homeostatic Control of Metabolism
II. Energy Balance
A. Energy Balance is reflected by a person’s ________ consumption
1. Oxygen consumption is equated to ___________ rate
a. Food energy is measured via a bomb ________ in which food is burned and the
resulting heat is measured in kilocalories
b. A ___________ (kcal = Calorie) is the amount of heat needed to raise the
temperature of one liter of water by 1°C
c. The metabolic energy of carbohydrates and proteins is ___ kcal/g, whereas that of
fats is ___ kcal/g
d. A food’s energy content can be calculated by multiplying the number of _______ of
each component by its _______ content
e. A person’s _________ expenditure may be determined by measuring their oxygen
consumption or CO2 production
1) __________ consumption is relatively constant at a rate of 1 L O2 per 4.5-5 kcal
of energy
2) The ratio of CO2 : O2 is known as the _________ ________ (RQ), and varies with
the composition of the diet
2. Many factors influence metabolic ________
a. __________ rate is the amount of energy released by the body in a given time (e.g.,
2,000 kcal/day)
b. Basal metabolic rate (______) is a person’s lowest metabolic rate (i.e., when resting
after a 12 hr. fast)
c. _______ that affect metabolic rate include age, gender, amount of lean muscle mass,
activity level, diet, hormones, and genetics
1) _________ – adult male BMR averages 1.0 kcal/hr/kg wt., whereas average
female BMR is 0.9 kcal/hr/kg, mainly due to a higher lean muscle mass/adipose
tissue ratio in males
2) Age – BMR ________ with age, partially due to decrease in muscle
3) Physical activity and muscle contraction ___________ the metabolic rate above
the BMR
4) Diet induced ____________ – metabolic rate increases after a meal due to
energy required to digest and absorb nutrients
a) ______ cause little heat production
b) ____________ increase heat production the most
5) Hormone effects – BMR is increased by _______ hormones and catecholemines,
as well as other peptides that regulate food intake
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d. The two key ____________ to avoiding weight gain are
1) ______ less
2) ____________ more
B. Energy is stored in _______ & glycogen
1. An average adult male requires about ________ kcal/day
2. Carbohydrates, proteins, and fats we eat are broken down, absorbed, and used for
immediate ________ needs; excess nutrients are _________ as glycogen or fat
3. __________ is a glucose polymer stored in the liver and muscle cells, and may be
broken back down to _________ when needed
4. Most of the body’s energy reserves are stored in _____, which has over ________ the
energy content of carbohydrates or proteins, but is more difficult for the body to
access
IV. Metabolism
A. ______________ is all the chemical reactions that extract, use, or store energy in the body.
Two types of metabolic __________ are
1. ___________ pathways, whereby small molecules are synthesized into larger ones
a. In the fed, or ____________ state, after a meal, products of digestion are absorbed,
used, and stored
b. _________ from the nutrients are transferred to high-energy compounds, or stored in
chemical ________ of other molecules
2. __________ pathways, in which large molecules are broken down to smaller ones
a. In the fasting, or _____________ state, nutrients are depleted from the blood, so the
body taps into its __________ reserves
b. Energy released by breaking chemical _____ is used to do work
B. The _______ of absorbed nutrients depends upon whether it is a carbohydrate, protein, or
fat
1. Carbohydrates are absorbed mostly as __________
a. Glucose is the main ________ source in the body
b. The _______ uses glucose exclusively as its energy source, except in times of
starvation
c. Excess glucose is stored as __________ (glycogenesis), or as _____ (lipogenesis)
d. If plasma glucose levels drop, the liver breaks glycogen down to glucose
(_______________) and releases it into the blood
2. Proteins are absorbed as _________ ______
a. Amino acids are used primarily for _________ synthesis
b. If glucose intake is low, certain amino acids can be converted into glucose in the
liver via ________________
C. Fats are absorbed mainly as ________ acids and _________
1. Fatty acids can be used as an ________ source by many tissues, or stored as
_____________ in adipose tissue
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2. Glycerol and fatty acids can also be converted to glucose like products via
gluco__________ pathways during times of fasting
D. ___________ control metabolic pathways by changing enzyme activity
1. Metabolic pathways can move forward or backward by using different __________
2. _________ can stimulate some enzymes, while inhibiting others
a. __________ stimulates enzymes for glycogen synthesis, and inhibits enzymes for
glycogen breakdown
b. ___________ stimulates enzymes for glycogenolysis, and inhibits enzymes for
glycogenesis
E. ____________ metabolism dominates in the fed (absorptive) state
1. _________ provides energy; once absorbed, it travels to the liver and other body
tissues. Glucose is used for:
a. _________, via cellular respiration
b. _____________ synthesis in the liver
c. _____________ synthesis in liver and muscle
d. Excess glucose is converted to ____ via: glucose → pyruvate → acetyl CoA →
fatty acids, and stored in adipose tissue
2. _________ _______ are used to synthesize proteins
a. Once absorbed, amino acids travel to the ______, where they are used to synthesize
_____proteins and ________ proteins (e.g., albumin, clotting factors, etc.)
b. Amino acids not used by the liver are used by cells to create structural proteins
(e.g., _______ and myosin) or functional proteins (e.g., _________ and
hormones)
c. If glucose is low, the liver converts AAs into intermediates for cellular
_____________
d. Excess AAs are converted to ____ via: amino acids → acetyl CoA → fatty acids,
and stored in adipose tissue
3. _______ are stored energy, and are transported in the blood as ______proteins - tiny
droplets of __________ and triglycerides coated with proteins and phospholipids.
F. ___________ metabolism dominates in the fasted (postabsorptive) state
1. The goal of fasted state metabolism is to maintain adequate plasma __________ levels,
because glucose is normally the only fuel the _______ can utilize
2. In _________ cells, glycogen is broken down to pyruvate or __________, which are
transported to the _______ and converted to glucose
3. ______________ in adipocytes are broken down to fatty acids and glycerol
a. __________ goes to the liver, where it is converted to glucose
b. _______________ are chopped into 2 carbon acetyl units via β-oxidation
1) Acetyl joins with Coenzyme A to form ______________, and is fed into the citric
acid cycle
2) Excess fatty acid breakdown in the liver leads to the formation of __________
bodies, which are used by the brain for energy during starvation
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3) Some ketone bodies are acidic, and can cause ___________, as occurs in
uncontrolled diabetes mellitus (recognized by the smell of acetone on a person’s
breath)
4. ___________ proteins may be broken down to AAs, which can be converted to glucose
products and used in cell ____________
a. Enzymes remove amino groups (___________) and form urea, which is excreted
b. Some deaminated AAs become _________ cycle intermediates and are used to make
ATP
c. Other AAs are converted to _________ and travel to the liver, where they are
processed to glucose
V. Homeostatic Control of Metabolism - occurs largely via ________ regulation
A. Pancreatic _________ (of Langerhans) secrete insulin and glucagon
1. Beta cells secrete _________
2. Alpha cells secrete __________ when glucose levels drop below 100 mg/dl, with
maximum secretion below 50 mg/dl
B. The ______ of insulin to glucagon in the blood keeps blood glucose levels within normal
range
1. Normal blood __________ levels range from about ____ mg/dl (fasted) to _____ mg/dl
(fed)
2. After a meal when plasma glucose levels begin to rise, _________ is secreted and
promotes glucose uptake into cells
3. Between meals when glucose levels drop, __________ is secreted, which causes
glycogenolysis and gluconeogenesis in the liver
C. ____________ is the dominant hormone in the fed state.
1. Factors that _______ insulin release during & after eating include
a. Plasma _________ concentration greater than 100 mg/dl
b. Increased plasma _______ ________ concentrations
c. GI hormones, such as _____, CCK, gastrin, and glucagon-like peptide 1 (GLP-1)
cause and anticipatory release of insulin
d. ________________ activity to the GI tract and pancreas after a meal
2. Sympathetic neurons and catecholamines released during stress _________ insulin
release, and stimulate gluconeogenesis
D. Insulin promotes ____________ by binding to a cell membrane tyrosine-kinase receptor
and lowering plasma glucose levels in several ways. _________
1. Increases glucose ____________ into most insulin-sensitive cells (i.e., adipocytes and
skeletal ______ cells) by causing the insertion of ________ transporters in their
membranes
2. Indirectly influences glucose transport into _______ cells through __________
transporters that remain in the cell membrane
3. Enhances cellular _____ and __________ of glucose via
a. _____________ of enzymes for glycolysis, glycogen, and fat synthesis
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b. ____________ of enzymes for glycogenolysis, gluconeogenesis, and lipolysis
4. Activates enzymes for protein __________, and inhibits enzymes that break down
proteins
5. Promotes the conversion of excess glucose and amino acids into triglycerides
(____________), and inhibits beta-oxidation of lipids
E. ____________ is the dominant hormone in the fasted state
1. Glucagon prevents ______________ (low plasma glucose levels)
2. Glucagon release is stimulated by declining plasma ________ and amino acid levels
between meals
2. Glucagon promotes __________ and gluconeogenesis in the liver, which increases
plasma glucose levels
F. Diabetes _____________ is a group of metabolic diseases
1. ___________ is a failure to produce insulin (type I diabetes) or reduced sensitivity of
insulin receptors on target cells (type II diabetes)
2. _________ diabetes (IDDM) usually begins in childhood due to the destruction of __
cells by autoantibodies. Symptoms include
a. Catabolism of __________ and adipose tissue
b. High plasma glucose levels (_____________)
c. Excessive urine production (_______) and glucose in the urine (__________)
d. Metabolic ___________ due to production of acidic ketones, which causes
1) Increased __________
2) Acidification of the ______
3) Hyper___________
4) Can result in ________ or even death
5) Treatment is ______ replacement with fluid and electrolyte therapy
e. Insulin must be _________ to control the symptoms. Too much insulin can cause
insulin _______
3. ______ diabetes (NIDDM) usually occurs in middle aged adults, but increasing in
overweight children; insulin is still secreted, but target cells are insulin __________
a. Symptoms are similar to type 1 diabetes, but usually less ____
b. Can often be controlled by ______ and ___________, but can eventually require
insulin injection if not controlled
4. Uncontrolled diabetes mellitus is the leading cause of adult ________, renal failure,
gangrene, and limb amputations