Chapter 24 Nutrition & Metabolism Lecture 12 Part 1: Overview, Carbohydrates, and Fats Marieb’s Human Anatomy and Physiology Ninth Edition Marieb Hoehn.

Chapter 24Nutrition & Metabolism

Lecture 12

Part 1: Overview, Carbohydrates, and Fats

Marieb’s HumanAnatomy and

PhysiologyNinth Edition

Marieb Hoehn

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Nutrients

Nutrients – chemical substances supplied by the environment required for survival (used for growth, repair, or maintenance of the body)

Macronutrients• carbohydrates• proteins• fats

Micronutrients• vitamins• minerals

Essential Nutrients• human cells cannot synthesize• include certain fatty acids, amino acids, vitamins

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Overview of General Metabolic Pathways

Figure from: Martini, Anatomy & Physiology, Prentice Hall, 2001

Lipolysis

Lipo-

genesis

Glycogenesis

Glycogenolysis

Overall goal of catabolism: generate a pool of 2- or 3-carbon molecules and ATP

Pyruvate is used to synthesize amino acids and Acetyl CoA

Pyruvate can also be used to synthesize glucose via gluconeogenesis.

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Carbohydrates

Sources• sugars (simple)• starches (complex) - usually from plant sources• glycogen (complex) in meats• cellulose (complex) is indigestible fiber

Recommended (Dietary) Daily Allowance (RDA) is 125-175g

Excesses lead to • obesity• dental caries• nutritional deficits

Deficiencies lead to • metabolic acidosis• weight loss

*

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Utilization of Carbohydrates

Glucose is the body’s CHO energy sourceFigure from: Hole’s Human A&P, 12th edition, 2010

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LipidsSources

• meats• eggs• milk• lard• plant oils

RDA is 80-100g ( 30% of calories)( 10% saturated fat)

Excesses lead to • obesity• increased serum cholesterol• increased risk of heart disease

Deficiencies lead to • weight loss• skin lesions• hormonal imbalances

Fats generally take the longest to digest. Why?

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Utilization of Lipids

Via what structures is fat absorbed into the circulation from the digestive tract?

Know these terms (see table of these terms later in this lecture)

Figure from: Saladin, Anatomy & Physiology, McGraw Hill, 2007

*

Oxaloacetic acid

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Beta-Oxidation of Fatty Acids

Long chain fatty acids (FA) require carnitine for transport into mitochondria

FA are broken down in a step-wise manner, 2 carbons at a time in beta-oxidation

Oxidation of FA yields about 1.5-2.0 times the energy from a comparable amount of glucose

Mitochondrion

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Energy Values of Food

Carbohydrates4.1 Calories per gram

Lipids9.5 Calories per gram

Proteins4.1 Calories per gram

Calorie (kilocalorie, big calorie) – amount of heat needed to raise the temperature of 1 kg of water by 10 C

Diet is 2000 Calories. What is the maximum number of grams of fat that should be taken in daily?

How many grams of fat are there in a Whopper with cheese and a small order of french fries?

Know this - you can round these off to the 4, 4, and 9)

So, what’s going on here?

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14g CHO x 4 cal/g = 56 cal 1g protein x 4 cal/g = 4 cal Total 60 cal

Alcohol! About 7 cal/g

Why do the calories for 12 oz. of this beer seem to be more than what you would suppose based on the CHO and protein content?

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Lipoprotein Traffic

Figure From: Martini, Anatomy & Physiology, Prentice Hall, 2001

Note the role of HDLs as scavengers of tissue/blood cholesterol.

TG-richCholesterol-rich

*Cholesterol can be manufactured from Acetyl-CoA

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Summary of LipoproteinsDesignation Origin Action

Chylomicron GI tract Transports dietary fats (mainly triglycerides) to liver

for processing

Very Low Density Lipoprotein (VLDL)

Liver Transports triglycerides from liver to adipose cells

Low Density Lipoprotein (LDL)

Liver Transports cholesterol from liver to cells in body

High Density Lipoprotein (HDL)

Liver Removes excess cholesterol from cells and transports to

liver

Know this chart

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Utilization of LipidsThe liver uses fatty acids to synthesize a variety of lipids

Linoleic (Ω 6)

Linolenic acid, EPA, and DHA (Ω 3)

Chem Figures From: http://en.wikipedia.org/wiki/

Figure From: Hole’s Human A&P, McGraw Hill, 2012

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Review

• Metabolism and fate of macronutrients– Carbohydrate

• Broken down into monosaccharides

• Metabolism, glycogen, fat, pentose sugars

– Lipids• Saturated vs. unsaturated fats

• Broken down into glycerol and fatty acids

• Used for energy (or storage of energy)

– Proteins• Complete vs. incomplete proteins

• Broken down into amino acids

• Structural components or energy