Nutrition and Metabolism Dietary Sources of Major Nutrients Basics of Cellular Respiration Metabolism of Carbos, Fats, and Protein Central Role

Nutrition and Metabolism Dietary Sources of Major

Nutrients

Basics of Cellular Respiration

Metabolism of Carbos, Fats, and Protein

Central Role of the Liver in Digestion/Metabolism

Cholesterol and Lipid Transport

Absorptive and Postabsorptive States

Developmental Aspects of Metabolism

Sources of Nutrients in the Diet

Macronutrients: Carbohydrates, Protein, Lipids, H2O

Micronutrients: Vitamins, Minerals

Major protein source

some vitamins

Major source of vitamins & minerals

Major source of carbohydrates & B vitamins

Major source of minerals and

vitamins A and D, some protein

Major source of lipids and

fat soluble vitamins A,D,E, K

Figure 24.1b

Red meat, butter:use sparingly

Vegetables inabundance

Whole-grainfoods atmost meals

Daily excercise and weight control

(b) Healthy eating pyramid

Dairy or calcium supplement: 1–2 servings

White rice, white bread,potatoes, pasta, sweets:

use sparingly

Fish, poultry, eggs:0–2 servings

Nuts, legumes:1–3 servings

Fruits:2–3 servings

Plant oilsat most

meals


Nutrients







In biological systems, the electrons are often associated with hydrogen atoms. Biological oxidations are often dehydrogenations.

Oxidation-Reduction is Important in Energy Production

Figure 5.10

Sugars, amino acids, fatty acids

Or FAD+ FADH2

The Energy Stored in ATP Can Be Used to Perform Work in the Cell

• The energy released by ATP breaking down into ADP and P can power a variety of needs in the cell

ADP P

PADP

Energized ATP:

Discharged ATP:

X Y+Z

Powering the synthesis of molecule Z by coupling oxidation to reduction:

Metabolic Pathways Involved in Cellular Respiration

Overall Equation for Cellular Respiration

34

An oxidation of glucose to reduce ADP to ATP

glucose

NAD

NADH2 pyruvates

mitochondrion

Cell membrane

CO2

CO2

CO2

O2

Glycolysis

Krebs Cycle

H 2OATP fuels

construction/synthesis reactions inside the cell

Acetyl CoA

4 ATP(substrate-

level phosphorylat

ion)

2 ATP(substrate-level phosphorylation)

30 ATP(oxidative

phosphorylation)

ATP Synthase

ElectronTransportChain and ATP Synthase

Linking Step

C6H12O6 + O2 CO2 + H2O + 34ATP sugar oxygen carbon dioxide water usable energy

Aerobic Cellular Respiration


Nutrients


Metabolism of the Three Macronutrients: Carbohydrates, Fats, and Protein





Fat Metabolism

acetone and

acetoacetic acid =

ketosis/acid-osis

in

liver

Body cells remove fat and cholesterol to build membranes, steroid hormones, adipose cells, and myelin sheaths

Oxidation of Fats (ß-Oxidation) for ATP

• Fat catabolism yields 9 kcal per gram (vs 4 kcal per gram of carbohydrate or protein)

• Fats must first be broken down to acetic acid, then in mito. to H2O, CO2, and ATP

• Ketones (acetoacetic acid and acetone can accumulate, producing acidosis/ketosis)

Fat metabolism handled mostly by the liver

• Some fats used to make ATP

• Used to synthesize lipoproteins, thromboplastin, and cholesterol

• Release breakdown products to the blood

Protein Metabolism

deamination

urea

Figure 24.3

Stage 1 Digestion in GI tract lumen to absorbable forms.Transport via blood totissue cells.

Stage 2 Anabolism (incorporation into molecules) and catabolism of nutrients to form intermediates within tissue cells.

Stage 3 Oxidative breakdown of products of stage 2 in mitochondria of tissue cells. CO2 is liberated, and H atoms removed are ultimately delivered to molecular oxygen, formingwater. Some energy released isused to form ATP.

Catabolic reactionsAnabolic reactions

Glycogen

PROTEINS

Proteins Fats

CARBOHYDRATES

Glucose

FATS

Amino acids Glucose and other sugars Glycerol Fatty acids

Pyruvic acid

Acetyl CoA

Infrequent CO2

NH3

H

Krebscycle

Oxidativephosphorylation

(in electron transport chain)

O2

H2O

Three Macronutrients Used for ATP Production


Nutrients







Role of the Liver in Metabolism

Produces blood proteins (albumin, clotting proteins) and lipoproteins Degrades hormones

•

•

•

•

•

•

•

Liver Modifications on Glucose Levels Glycogenesis (making glycogen)

• Glucose molecules are converted to glycogen

• Glycogen molecules are stored in the liver

Glycogenolysis (breaking glycogen)

• Glucose is released from the liver after conversion from glycogen

Gluconeogenesis (rebuilding glucose)

• Glucose is produced from amino acids and glycerol

• Protects against damaging effects of hypoglycemia

Roles of Cholesterol in the Body

Vitamin D synthesis

Keeping membranes fluid

Steroid Hormone Synthesis

Cholesterol Transport Cholesterol and fatty acids cannot freely circulate in

the bloodstream

They are transported by chylomicron lipoproteins (lipid-protein complexes)

• Low-density lipoproteins (LDLs) transport cholesterol to body cells; are increased by dietary saturated and trans-fat

Triglycerides broken down by fat and muscle tissue (lipoprotein lipase) into fatty acids and glycerol

• High-density lipoproteins (HDLs) transport from body cells to the liver for breakdown; are increased by exercise, and limited coffee, smoking, and saturated fats/trans fats

Healthy Ratios in the Blood

• Total Cholesterol/HDL < 5

• LDL/HDL < 2.5

Total cholesterol (mg/dL)Under 200 - desirable 200-239 - borderline highOver 240 - highLDL cholesterol (mg/dL)Below 100 - optimal100-129 - near optimal130-159 - borderline high160-189 - highAbove 190 - very highHDL cholesterol (mg/dL)Below 40 - low60 or above - high


Nutrients







Absorptive and Postabsorptive States Absorptive (fed) state

• During and shortly after eating; absorption of nutrients

• Muscle and fat tissue: lipoprotein lipase hydrolyzes lipids of chylomicrons in muscle and fat tissues; most glycerol and fatty acids are converted to triglycerides for storage

• Liver: Excess amino acids are deaminated and used for ATP synthesis or stored as fat in the liver

• Insulin facilitates glucose uptake, glycogenesis, triglyceride genesis, and protein synthesis

Postabsorptive (fasting) state

• When the GI tract is empty; energy sources are supplied by breakdown of reserves

• Liver: lipolysis, glycerol then fuels glycogenolysis

• Skeletal muscle: glycogenolysis; protein catabolism if starving

• Fat tissue: lipolysis tissues and the liver

• Glucagon facilitates glycogenolysis and gluconeogenesis in the liver, fat tissue lipolysis

Developmental Aspects of the Digestive System Fetal Development

• The alimentary canal is a continuous tube by the fifth week of development

• Digestive glands bud from the mucosa of the alimentary tube

• The developing fetus receives all nutrients through the placenta

Birth and Infancy

• In newborns, feeding must be frequent, peristalsis is inefficient, and vomiting is common

• Congenital conditions include cleft palate, phenylketonuria, tracheoesophageal fistula

• Teething (eruption of teeth) begins around age six months

Metabolism decreases with old age

Middle age digestive problems

• Ulcers

• Gall bladder problems

Old Age

• Fewer digestive juices

• Peristalsis slows

• Diverticulosis and cancer are more common

brain damage and

retardation in infancy

Tracheoesophageal Fistula

PKU

Nutrition and Metabolism Dietary Sources of Major Nutrients







Documents

Nutrition and Metabolism Dietary Sources of Major Nutrients Basics of Cellular Respiration Metabolism of Carbos, Fats, and Protein Central Role