Energy for
tissues
Objectives
• Nutrients used for energy
• state the dietary nutrients that contribute towards daily
energy requirement and the contribution made by each
• state the major pathways used by each nutrient to
produce energy
• explain the importance of oxygen in energy production
• state giving reasons the fuels used by different types of
tissues of the body at different times of the day
Biochemical Energy
• state the currency of energy
• state the form in which energy is stored in muscle
• explain the importance of mitochondrial oxidation in
energy production
What are the dietary nutrients that
contribute towards daily energy
requirement ?
• Energy for the metabolic and physiological
functions of humans is derived from the
chemical energy bound in food and its
macronutrient constituents,
• i.e. carbohydrates, fats, proteins and
ethanol, which act as substrates or fuels
• After food is ingested, its chemical energy is
released and converted into thermic,
mechanical and other forms of energy
• Fats and carbohydrates are the main
sources of dietary energy
•
Energy provided by substrates in a mixed diet are,
Carbohydrate or protein - 4 kcal per gram
Fat -
9 kcal per gram
Ethanol -
7 kcal) per gram
Ethanol is not considered part of a food system
Major pathways used by nutrients to
produce energy
• Carbohydrates - glycolysis, TCA cycle
• Fats – TCA cycle
• Proteins – TCA cycle
• Cellular respiration
• Cells energy production mechanism is
called cellular respiration. It is the process
cells use to retrieve energy stored in
carbohydrates, fats and proteins
• Organisms that use oxygen as a final
electron acceptor in respiration are
described as aerobic
Currency of energy
• ATP is a complex nanomachine that serves
as the primary energy currency of the cell
• It is the “most widely distributed high-energy
compound within the human body”
• As fuel molecules are oxidized energy
released is stored in ATP
Forms of energy stored in muscles
•
•
•
•
Creatine phosphate
ATP
TAG
Glycogen
Fuels used by different tissues
Cardiac muscles
Free fatty acids
Ketone bodies
Glucose
Lactate
Creatinephosphate
• Skeletal red muscles
Free fatty acids
Ketone bodies
Glucose
Creatinephosphate
Glycogen
Skeletal white muscle
Glucose
Glycogen
Creatinephosphate
Free fatty acids
Ketone bodies
• State the end products of catabolism and
routes of excretion of carbohydrates, fat,
proteins, cholesterol and creatinephosphate