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Copyright © 2011 Pearson Education, Inc.

NUTRIENTS, CHAPTER 23

Protein, carbohydrates, protein, fats and nucleic acids


Nutrition

• Major nutrients

1. Carbohydrates

2. lipids

3. proteins

• Minor nutrients:

• vitamins

• minerals

• water

Copyright © 2011 Pearson Education, Inc. Figure 23.1b

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

Revised Food Pyramid


NUTRIENT SOURCE AND FUNCTION


Carbohydrates

• Preferred energy source

• Used to make ATP

• Used by neurons and RBCs

• Excess stored as fat or glycogen

• Minimum 100g/day

• Found in:

• Complex carbohydrates (starches, grains and vegetables)

• Sugars (fruits, sugarcane, sugar beets, honey and milk)


Lipids

• Triglycerides

• Saturated fats:

• meat, dairy foods, and tropical oils

• Unsaturated fats

• seeds, nuts, olive oil, and vegetable oils

• Cholesterol, found in animal products

• Less than 300 mg/day


Lipid Function

• Functions of fatty deposits (adipose tissue)

• Protective cushions around body organs

• Insulating layer beneath skin

• Concentrated source of energy

• Cholesterol:

• Stabilizes membranes

• Precursor of bile salts and steroid hormones


Proteins

• Dietary sources:

• Eggs, milk, fish, and meat (animal products)

• Legumes, nuts, and cereals contain incomplete proteins

• Recommend: 0.8g/kg body weight


Proteins

• Uses

• Structural materials:

• Keratin

• Collagen

• Muscle proteins

• Functional molecules, enzymes

• Used for energy only when carbohydrates and fats are gone.


Vitamins

1. Water-soluble vitamins

• B complex and C

• absorbed with water

2. Fat-soluble vitamins

• A, D, E, and K

• absorbed with lipids


Minerals

• Important for body function

• Examples

• Calcium, phosphorus, and magnesium salts harden bone

• Iron is essential for oxygen binding to hemoglobin

• Iodine is necessary for thyroid hormone synthesis

• Sodium and chloride are major electrolytes in the blood


ABSORPTION OF NUTRIENTS


Absorption

• There are four main classes of nutrients

1.Carbohydrates (sugars)

2.Protein

3.Fats

4.Nucleic acids (DNA/RNA) / minerals

• water


Absorption of Carbohydrates

• Digestive enzymes – break sugars into absorbable pieces

• Salivary amylase (salivary glands)

• Pancreatic amylase (pancreas)

• Border enzymes (small intestine)


Absorption of Proteins

• Pepsin (stomach)

• Trypsin (pancreatic proteases)

• Peptidases (brush border enzymes)


Absorption of Lipids

• Bile salts (liver)

• Pancreatic lipases (pancreas)


Absorption of Nucleic Acids

• Digested by pancreatic enzymes

• Absorbed by active transport

• Used for DNA and RNA synthesis


Vitamins and Electrolyte Absorption

• Absorbed by small intestine

• Based on solubility

• Fat-soluble vitamins (A, D, E, and K) absorbed similar to fats

• Water-soluble vitamins (vitamin C and B vitamins) are absorbed by diffusion

• Ca2+ absorption is regulated by vitamin D


Water Absorption

• 95% by small intestine via osmosis

• Rest reclaimed by large intestine


CHOLESTEROL LEVELS

HDL vs LDL


Lipids and Cholesterol

• Cholesterol is a type of lipid

• Low-density lipoproteins (LDL) “bad cholesterol”

• Transport lipids to adipose tissue

• High-density lipoproteins (HDL) “good cholesterol”

• Uses lipids for hormone production

• Lowered by: stress, cigarette smoking, and coffee

• Increased by: Aerobic exercise


Cholesterol

• Made by the liver

• Saturated fatty acids

• Stimulate synthesis of cholesterol

• Unsaturated fatty acids

• Enhance excretion of cholesterol

• Trans fats

• Reduce HDLs and raise LDLs


Cholesterol

• Body shape

• “Apple”: Fat carried on upper body is correlated with high cholesterol and LDL levels

• “Pear”: Fat carried on hips and thighs is correlated with lower cholesterol and LDL levels


FOOD INTAKE REGULATION


Regulation of Food Intake

• Leptin

• Hormone secreted by fat cells (adipose tissue)

• Suppresses appetite in response to increased body fat mass


Regulation of Food Intake

• Additional factors

• Temperature

• Stress

• Psychological factors

• Adenovirus infections

• Sleep deprivation


Obesity

• Body mass index (BMI) = wt (lb) 705/ht (inches)2

• Considered overweight if BMI is 25 to 30

• Considered obese if BMI is greater than 30

• Higher incidence of atherosclerosis, diabetes mellitus, hypertension, heart disease, and osteoarthritis


DISORDERS OF THE DIGESTIVE SYSTEM


Malabsorption of Nutrients

• Celiac Disease - gluten-sensitive enteropathy

• Gluten causes an allergic reaction that damages the intestinal villi

• Symptoms: diarrhea, fatigue, weight loss

• Treatment: gluten free diet

• all grains but rice and corn


Diarrhea

•Watery stool

• Caused by any condition that rushes food through the large intestine before water has been reabsorbed.

• Cholera – diarrhea cause by bacterium Vibrio cholerae

• Found in feces

• Massive dehydration

• Can lead to death if not treated


Jaundice

• Yellowing of the skin and sclera

• Caused by build of up bilirubin (liver enzyme)

• Results from liver damage or blood disorder


Cancer

• Alimentary cancers rarely have early signs

• Polyps

• Metastasized colon cancers frequently cause secondary liver cancer

• Prevention

• Regular dental and medical examination

• Colonoscopies after age 40

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