sports nutrition_chapter 2_nutrients
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Sports Nutrition_Chapter 2_NutrientsTRANSCRIPT
Nutrients: Ingestion to
Energy Metabolism
Chapter 2
What happens to nutrients after they are ingested?
• Two types of digestion– Mechanical: includes chewing, peristalsis– Chemical: includes digestion enzymes
• Absorption
• Transport• Assimilation and/or energy production
Digestion: Anatomy and Functions of the Digestive System
Mouth to anus is 25 ft!
• Mouth (oral cavity)• Esophagus• Stomach• Small intestine• Large intestine• Rectum
Digestion: Salivary Glands
• Salivary glands– See figure to right
• Secrete saliva– Moistens food– Contains enzymes
Digestion: Stomach
• Muscular organ• Primary function:
digestion• Major secretions
– Hydrochloric acid to unravel proteins
– Mucus to protect stomach tissue from acid.
– Digestive enzymes
Digestion and Absorption: Small Intestine
• Duodenum– Majority of digestion
occurs here• Jejunum
– Little digestion– Absorption
• Ileum– Absorption
Absorption: Surface of Small Intestine
• Convoluted interior
• Villi
• Microvilli
• Result: Increased surface area for absorption
Absorption: Large Intestine• Colon
– Ascending– Transverse– Descending
• Rectum• Anus• Some absorption
– Water– Sodium– Chloride– Potassium– Vitamin K
Absorption: Mechanisms• Passive diffusion – move from high to low
concenration• Facilitated diffusion- move from high to low
concentration carried by protein carrier.• Active transport – Concentration gradient not a
factor.• Endocytosis
Absorption: Mechanisms
• Passive diffusion• Facilitated diffusion• Active transport• Endocytosis
Absorption of Nutrients
Review this figure to see where along the GI tract individual nutrients are absorbed.
Carbohydrates: Digestion
• Mouth– Mastication
(chewing)– Amylase
• Stomach– Churning– Acid
• Small intestine– Sugar enzymes
• Large intestine– Bacteria
Carbohydrates: Absorption
• Most absorption occurs in small intestine
• Mechanisms– Facilitated diffusion
• Fructose– Active transport
• Glucose• Galactose
Carbohydrates: After Absorption
• Transport via blood• Cellular uptake
– Insulin– Glucose transporters
• Fates– Storage in liver or
muscles as glycogen.– Conversion to
adipose tissue (fat).– Energy
Fats: Digestion
• Mouth– Mastication– Lingual lipase
• Stomach– Gastric lipase
• Small intestines– Bile– Pancreatic lipase– Micelle formation
[Insert Fig. 2.12 here]
Fats: Absorption
• Occurs in small intestine• Mechanism
– Passive diffusion• Very little fat makes it to
large intestine– Steatorrhea– Crohn’s disease– Cystic fibrosis
Fats: After Absorption
• Transport– Lymph
• Chylomicrons– Blood
• Cellular uptake– Lipoprotein lipase
• Fates– Storage– Energy
Proteins: Digestion
• Mouth• Mastication
• Stomach• Churning• Acid Denaturation: acid unravels proteins so
peptide bonds can be cleaved by enzymes. Very important function of the stomach.
• Small intestine• Proteases• Peptidases
Proteins: Absorption• Occurs in small intestine• Mechanism
– Facilitated diffusion– Active transport
• Very little makes it to large intestine
Proteins: Absorption
AMINO ACID SUPPLEMENTATION CAUTION
• Carrier proteins are responsible for facilitating absorption of amino acids.
• Similar amino acids share the same active transport systems and protein carriers.
• Taking amino acid supplements containing large amounts of single amino acids can affect the absorption of other amino acids if they share the same transport carrier.
• If an athlete takes a large amount of a single amino acid this may result in overabsorption of that amino acid at the expense of another amino acid.
Proteins: After Absorption• Transport
– Blood
• Become part of amino acid pool
• Fates
– Body proteins such as muscle, enzymes, hormones.
– Conversion to body fat.
– Energy : Used for energy only when carbohydrate is not available fuel source. Not preferred fuel source as it has more important and essential roles in body.
Cellular Protein Synthesis
• Transcription– DNA– mRNA
• Translation– Transfer RNA– Amino acids
• Digestion causes release from foods• Absorption occurs in small and large intestines
Vitamins, Minerals, and Water
What is energy?
• It is the entity that enables our bodies to perform work.
• It has no shape.• It has no physical mass.• Our bodies rely on
chemical energy.
Photo © Photodisc
What is the body’s source of energy?
• Macronutrients– Carbohydrates– Fats– Proteins
• Body’s direct energy source– Adenosine
triphosphate (ATP)
Adenosine Triphosphate (ATP)
• Body’s energy source• Two high-energy
bonds• Other phosphates
– ADP– AMP
Cell Structure and Organelles Necessary for ATP Production
What are the three energy systems?
• Phosphagen System
• Anaerobic Energy System
• Aerobic Energy System
Comparison of the Three Energy Systems
Metabolic Pathways
Energy Nutrients
Cellular ATP Production:The Metabolic Factory
Phosphagen Energy System
• Stores of high-energy phosphates– ATP– Creatine phosphate
(CP)• Also known as:
– Immediate energy system
– ATP-CP system
Anaerobic Energy System
• Involves only carbohydrates
• Does not require oxygen• Also known as:
– Anaerobic glycolysis
Aerobic Energy System
• Involves all macronutrients
• Requires oxygen• Also known as:
– Oxidative system
Energy System Contributions to Activities of Varying Intensity
The small storage pool of ATP is the source of energy whenever instantaneous energy is needed.
Energy System Contributions to Activities of Varying Intensity
During short bursts of intense activity (i.e., 100m run), the phosphagen system is the main energy system that supplies the ATP pool.
Energy System Contributions to Activities of Varying Intensity
During longer lasting sprint activities of lower intensity (i.e., 800m run), the main supplier is the anaerobic system with help from the phosphagen and aerobic systems.
Energy System Contributions to Activities of Varying Intensity
During longer lasting activities of even lower intensity (i.e., mile run), the main supplier becomes the aerobic system with help from the anaerobic system.
Energy System Contributions to Activities of Varying Intensity
During long lasting activities of low intensity (i.e., any sustainable activity), the main supplier becomes the aerobic system with minimal help from the other systems.
Summary:
The Energy Systems Work Together to Meet ATP Demand
How does carbohydrate intake impact protein metabolism?
• Carbohydrates are an important energy source.
• Low CHO results in muscle protein breakdown.
• Gluconeogenesis.