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IMMS 2- Metabolism
Phase 1A
Rajpinder Singh Seehra
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Aims
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Metabolism (definition)
Metabolic Rate and Influencing Factors
Fuel types and their Effectiveness
Storing Energy
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Definitions
• Metabolism: chemical reactions that occur in a living
organism.
• Metabolic rate: total-body energy expenditure per unit
time.
• Total Energy Expenditure: internal heat produced +
external work performed+ energy stored.
(Vander’s Human Physiology 12th Edition)
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Basal Metabolic Rate (BMR)
• The metabolic rate when a person is at mental
and physical rest but not sleeping, at
comfortable temperature and has fasted at least
12 hours.
• 60% of the total energy expenditure
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Factors Affecting the Metabolic Rate
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Sleep (↓ when asleep)
Age (↓ with ↑ age)
Gender (women<men)
Fasting (BMR ↓ to conserve energy stores)
Height, Weight
Pregnancy
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The Hypothalamus
• An important organ in regulating metabolic
control.
• Functions include:
• control of the autonomic nervous system (ANS)
• regulation of food intake (thirst and feeding
centres)
• regulation of body temperature
• Very important factor in metabolic disorders.
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The Thyroid
• Endocrine organ.
• Located in the neck, two connected lobes.
• Controls how quickly the body:
• uses energy
• makes protein
• and hormone sensitivity
• Produces thyroid hormones T3 and T4 to do the above
functions.
• Regulated by thyroid-stimulating hormone from the anterior
pituitary which in turn is controlled by thyrotropin=releasing
hormone from the hypothalamus.
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Factors Affecting Daily Energy Expenditure
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Body Temperature Regulation
Infection and disease
Food intake
Exercise —> any form of muscular activity*
Stress
Hormone levels (adrenaline, thyroid hormone)
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Fuel Types and their
Effectiveness
• Carbohydrate: Used in the form of glucose. 30%
of ATP production at rest.
• Fat: Can be in the form of triglycerides or
esterified fatty acids. 70% of ATP production at
rest.
• Protein: last used, often due to longer periods of
starvation. Stores seem to decrease with age.
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Fuel Types and their
Effectiveness
• Carbohydrate: 1g converts to approximately 17
joules of energy
• Fat: 1g converts to approximately 38 joules of
energy
• Protein: 1g converts to approximately 17 joules
of energy
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Ethanol
• Alcohol.
• Converted from:
• ethanol to acetaldehyde (alcohol dehydrogenase IB, a
hepatic enzyme)
• acetaldehyde to acetic acid (aldehyde dehydrogenase 2)
• acetic acid to acetyl-CoA (acetyl CoA synthase-1 and 2)
• acetyl-CoA to water and carbon dioxide. (CAC)
• When alcohol is in excess the effects become more
predominant and thus a greater period of time is required to
clear the system.
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Storing Energy
• To keep body weight stable: Energy
used=energy intake
• Energy stored is therefore: intake - expenditure
• If this is positive the body works to store the
excess energy.
• Generally an anabolic process (synthesis a larger
molecule from smaller components)
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Carbohydrate Storage
• Account for 1 percent of body mass.
• Glycogenesis: conversion of excess glucose into
glycogen as a cellular storage mechanism.
• Stored as glycogen in skeletal muscle and the liver.
• Excess is often catabolised to form Acetly-CoA
• Insulin acts to increase the storage process and
insulin levels correlate to blood glucose.
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Lipid Storage
• Account for 15 percent of body mass.
• Primarily stored as triglycerides (ester of
glycerol and 3 fatty acids).
• Fatty acids are converted to triglycerides for
storage.
• Mainly stored in adipocytes.
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Protein Storage
• Account for 17 percent of body mass.
• Stored in muscle.
• Amino acids built into relevant proteins for the
cell functions.
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Any Questions?
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