Nutrition and Metabolism

1
Nutrition and Metabolism
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• Nutrition

• Nutrient
• Categories of nutrients
• Macronutrients
• Micronutrients
• Essential nutrients

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White rice, white bread, potatoes, pasta,
sweets use sparingly
Red meat, butter use sparingly
Dairy or calcium supplement 12 servings
Fish, poultry, eggs 02 servings
Nuts, legumes 13 servings
Fruits 23 servings
Vegetables in abundance
Plant oils at most meals
Whole-grain foods at most meals
Daily excercise and weight control
(b) Healthy eating pyramid
Figure 24.1b
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• Dietary Sources of Major Nutrients

• Carbohydrates
• Most from plants/Fiber (Cellulose)
• Exceptions lactose from milk and small amounts
  of glycogens from meats
• Lipids
• Saturated fats from animal products
• Unsaturated fats from nuts, seeds, and vegetable
  oils
• Cholesterol from egg yolk, meats, and milk
  products

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• Dietary Sources of Major Nutrients

• Proteins
• Complete proteins contain all essential amino
  acids
• Most are from animal products
• Legumes and beans also have proteins, but are
  incomplete
• Vitamins
• Most vitamins are used as cofactors and act with
  enzymes
• Found in all major food groups

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• Dietary Sources of Major Nutrients

• Minerals
• Play many roles in the body
• Most mineral-rich foods are vegetables, legumes,
  milk, and some meats

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Carbohydrates

• RDA 125-175g/day 45-65 of diet
• production of certain molecules (ribose,
  deoxyribose)
• stored in liver and muscles as glycogen
• converted to fats and stored in adipose tissue
• The main energy source for the body

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Lipids

• RDA 80-100g 30 or less of diet. 10 sat. fat
• production of triglycerides, phospholipids,
  lipoproteins, and cholesterol
• stored in adipose tissue
• The liver uses fatty acids to synthesize a
  variety of lipids
• Fuel source

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Proteins

• RDA .8g/Kg weight
• build cell structures
• enzymes
• hormones
• transport of oxygen
• regulation of water balance
• control of pH
• formation of antibodies
• can be converted to carbohydrates or fats
• may be broken down and oxidized for energy

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Tryptophan
Methionine (Cysteine)
Beans and other legumes
Tryptophan
Valine
Methionine
Threonine
Valine
Phenylalanine (Tyrosine)
Total protein needs
Threonine
Leucine
Phenylalanine
Isoleucine
Leucine
Corn and other grains
Isoleucine
Lysine
Lysine
Histidine (Infants)
Arginine (Infants)
Vegetarian diets providing the eight essential
amino acids for humans
(b)
Essential amino acids
(a)
Figure 24.2
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Fat Soluble Vitamins

• Vitamin A
• synthesized from carotenes
• stored in liver
• necessary for visual pigments
• necessary for bone and teeth development
• necessary for maintenance of epithelial cells
• excesses lead to nausea, headache, dizziness,
  hair loss, birth defects
• deficiencies lead to night blindness and
  degeneration of epithelial tissues

• Vitamin D
• group of steroids
• stored in liver, brain, skin, spleen, and bone
• promotes absorption of calcium and phosphorus
• necessary for bone and teeth development
• excesses lead to diarrhea, calcification of soft
  tissues, and renal damage
• deficiencies lead to bone weakening

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Fat-Soluble Vitamins

• Vitamin E
• stored in muscles and adipose tissue
• prevents oxidation of vitamin A and some fatty
  acids
• may help stability of cell membranes
• excesses lead to hypertension

• Vitamin K
• stored in liver
• necessary for prothrombin synthesis
• deficiencies lead to bruising and bleeding

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Sources of Fat-Soluble Vitamins

• Vitamin A
• liver
• fish
• milk
• leafy green vegetables
• yellow and orange vegetables and fruits

• Vitamin E
• cereal seed oils
• salad oils
• margarine
• shortening
• fruits
• nuts
• vegetables

• Vitamin K
• liver
• soy oil
• egg yolk
• leafy green vegetables
• tomatoes
• cauliflower

• Vitamin D
• skin
• egg yolk
• milk
• fish liver oils

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Water-Soluble Vitamins

• Vitamin B1 thiamine
• coenzyme for carbohydrate oxidation
• Help pyruvic acid enter TCA
• meats, liver, leafy green vegetables, eggs,
  cereals, legumes
• deficiencies lead to Beriberi, muscular
  weakness, enlargement of heart

• Vitamin B2
• riboflavin
• parts of enzymes and coenzymes (FAD)
• milk, leafy green vegetables, meats
• deficiencies lead to dermatitis and blurred
  vision

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Water-Soluble Vitamins

• Niacin
• parts of coenzymes (NAD) and NADP
• liver, meats, peanuts, legumes
• deficiencies lead to pellagra-dermatitis,
  diarrhea, or mental disorders

• Pantothenic Acid- B5
• part of coenzyme A
• meats, cereals, legumes, milk, vegetables
• deficiencies are rare

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Water-Soluble Vitamins

• Vitamin B6
• part of coenzymes needed for synthesis of
  proteins
• meats, cereals, peanuts, milk, bananas, avocados
• deficiencies lead to vomiting and convulsions

• Vitamin B12
• part of coenzyme needed for nucleic acid
  synthesis
• plays role in myelin sheath formation
• needed for RBC formation
• meats, milk, liver, cheese, eggs
• deficiencies lead to anemia

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Water-Soluble Vitamins

• Folic Acid
• coenzyme required for amino acid and nucleic
  acid metabolism
• needed for normal RBC production
• cereals, legumes, milk, leafy green vegetables
• deficiencies lead to anemia

• Biotin
• coenzyme required for metabolism of amino acids,
  fatty acids, and nucleic acids
• egg yolk, liver, legumes, nuts, mushrooms
• deficiencies lead to elevated blood cholesterol,
  fatigue, nausea, and anorexia

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Water-Soluble Vitamins

• Vitamin C
• ascorbic acid
• needed for collagen production and metabolism of
  some amino acids
• promotes absorption of iron and synthesis of
  hormones from cholesterol
• citrus fruits, tomatoes, potatoes, leafy green
  vegetables
• deficiencies lead to scurvy, lowered resistance,
  and slow wound healing

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Minerals

• Major Minerals
• calcium
• phosphorus
• potassium
• sulfur
• sodium
• chlorine
• magnesium

• Trace Elements
• iron
• manganese
• copper
• iodine
• cobalt
• zinc
• fluorine
• selenium
• chromium

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Major Minerals

• Calcium
• mostly in bones and teeth
• needed for bone structure
• essential for nerve impulse conduction
• essential for muscle fiber contraction
• essential for blood coagulation
• increases permeability of cell membranes
• activates certain enzymes
• excesses lead to kidney stones
• deficiencies lead to stunted growth and fragile
  bones

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Major Minerals

• Phosphorus
• mostly in bones and teeth
• needed for structure of bones and teeth
• component in nearly all metabolic processes
• constituent of ATP, nucleic acids, many
  proteins, enzymes, and some vitamins
• deficiency leads to stunted growth

• Potassium
• widely distributed
• maintains intracellular osmotic pressure and pH
• promotes metabolism
• required for muscle contraction and nerve
  impulse conduction
• deficiency leads to muscular weakness, cardiac
  abnormalities, and edema

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Major Minerals

• Sodium
• widely distributed
• maintains osmotic pressure of extracellular
  fluids
• regulates water movement in and out of cells
• required for nerve impulse conduction and
  contraction of muscle fibers
• excesses lead to edema and hypertension
• deficiency leads to muscle cramps and convulsions

• Sulfur
• widely distributed
• abundant in skin, nails, and hair
• component of certain amino acids, thiamine,
  biotin, and mucopolysaccharides

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Major Minerals

• Chlorine
• most concentrated in cerebrospinal fluid and
  gastric juice
• helps maintain osmotic pressure of extracellular
  fluids
• regulates pH
• essential for formation of hydrochloric acid
• aids in transport of carbon dioxide
• deficiency leads to muscle cramps

• Magnesium
• abundant in bones
• required in metabolic reactions for ATP
  production
• helps breakdown of ATP to ADP
• excess leads to diarrhea
• deficiency leads to neuromuscular disturbances

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Trace Elements

• Iron
• part of hemoglobin
• catalyzes formation of vitamin A
• incorporated into some enzymes

• Manganese
• occurs in enzymes required for fatty acid and
  cholesterol synthesis, formation of urea, and
  functioning of the nervous system

• Copper
• essential for hemoglobin synthesis, bone
  development, melanin production and myelin
  formation

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Trace Elements

• Iodine
• component of thyroid hormone

• Cobalt
• required for synthesis of several enzymes

• Zinc
• component of many enzymes
• necessary for wound healing and maintaining
  integrity of skin
• Fluorine
• component of tooth structure

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• Metabolism

• Defined as the sum total of all chemical
  reactions in the body
• Catabolism
• Anabolism
• Energy is released during catabolism
• Oxidation is a gain Reduction is a loss

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Stage 1 Digestion in GI tract lumen to
absorbable forms. Transport via blood to tissue
cells.
PROTEINS
CARBOHYDRATES
FATS
Glucose and other sugars
Fatty acids
Amino acids
Glycerol
Stage 2 Anabolism (incorporation into
molecules) and catabolism of nutrients to form
intermediates within tissue cells.
Glycogen
Glucose
Proteins
Fats
NH3
Pyruvic acid
Acetyl CoA
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, forming water.
Some energy released is used to form ATP.
Krebs cycle
Infrequent
CO2
O2
Oxidative phosphorylation (in electron transport
chain)
H2O
H
Catabolic reactions
Anabolic reactions
Figure 24.3
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• Metabolic Pathways Involved in Cellular
  Respiration

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Cytosol
Electron trans- port chain and
oxidative phosphorylation
Glycolysis
Krebs cycle
Pyruvic acid from glycolysis
NAD
CO2
Transitional phase
NADHH
Acetyl CoA
Carbon atom
Mitochondrion (matrix)
Inorganic phosphate
Oxaloacetic acid
Coenzyme A
Citric acid
(pickup molecule)
(initial reactant)
NADHH
NAD
Isocitric acid
Malic acid
NAD
Krebs cycle
CO2
NADHH
-Ketoglutaric acid
Fumaric acid
CO2
NAD
FADH2
Succinic acid
Succinyl-CoA
NADHH
FAD
GDP
GTP
ADP
Figure 24.7
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Electron transport chain and oxidative phosphoryla
tion
Glycolysis
Krebs cycle
Intermembrane space
Inner mitochondrial membrane
1 2
2 H
ATP synthase
FADH2
FAD
NADH H
(carrying from food)
ADP
NAD
Mitochondrial matrix
Electron Transport Chain
Chemiosmosis
Electrons are transferred from complex to
complex and some of their energy is used to pump
protons (H) into the intermembrane space,
creating a proton gradient.
ATP synthesis is powered by the flow of H back
across the inner mitochondrial membrane through
ATP synthase.
Figure 24.8
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High H concentration in intermembrane space
Membrane
Proton pumps (electron transport chain)
ATP synthase
Energy from food
ADP
Low H concentration in mitochondrial matrix
(b) Oxidative phosphorylation
Figure 24.4b
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Mitochondrion
Cytosol
2 NADH H
Electron shuttle across mitochondrial membrane
2 FADH2
2 NADH H
6 NADH H
Glycolysis
Electron transport chain and oxidative phosphoryla
tion
2 Acetyl CoA
Krebs cycle
Pyruvic acid
Glucose
(4 ATP2 ATP used for activation energy)
10 NADH H x 2.5 ATP
2 FADH2 x 1.5 ATP
Net 2 ATP by substrate-level phosphorylation
about 28 ATP by oxidative phosphorylation
2 ATP by substrate-level phosphorylation
Maximum ATP yield per glucose
About 32 ATP
Figure 24.12
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• Fat Metabolism

• Handled mostly by the liver
• Use some fats to make ATP
• 9 kcal per gram (vs 4 kcal per gram of
  carbohydrate or protein)
• Synthesize lipoproteins, thromboplastin, and
  cholesterol
• Body cells remove fat and cholesterol to build
  membranes and steroid hormones

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• Use of Fats for ATP Synthesis

• Fats must first be broken down to acetic acid
• Within mitochondira, acetic acid is completely
  oxidized to produce water, carbon dioxide, and ATP

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Lipids
Lipase
Glycerol
Fatty acids
H2O
Coenzyme A
Glyceraldehyde phosphate (a glycolysis
intermediate)
NAD
NADH H
b Oxidation in the mito- chondria
FAD
Glycolysis
FADH2
Pyruvic acid
Cleavage enzyme snips off 2C fragments
Acetyl CoA
Krebs cycle
Figure 24.14
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Glycolysis Glucose
Stored fats in adipose tissue
Glycerol
Glyceraldehyde phosphate
Triglycerides (neutral fats)
Lipogenesis
Dietary fats
Fatty acids
Certain amino acids
Pyruvic acid
b
Ketone
Ketogenesis (in liver)
Acetyl CoA
bodies
CO2 H2O
Steroids
Electron transport
Cholesterol
Bile salts
Krebs cycle
Catabolic reactions
Anabolic reactions
Figure 24.15
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• Protein Metabolism

• Proteins are conserved by body cells because they
  are used for most cellular structures
• Ingested proteins are broken down to amino acids

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• Protein Metabolism

• Cells remove amino acids to build proteins
• Synthesized proteins are actively transported
  across cell membranes
• Amino acids are used to make ATP only when
  proteins are overabundant or there is a shortage
  of other sources
• Controlled by hormones

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Transamination
1
During transamination an amine group is
switched from an amino acid to a keto acid.
Amino acid Keto acid
Keto acid Amino acid
(glutamic acid)
(a-keto- glutaric acid)
Liver
Oxidative deamination
NH3 (ammonia)
Keto acid modification
In oxidative deamination, the amine group
of glutamic acid is removed as ammonia and
combined with CO2 to form urea.
2
3
During keto acid modification the keto
acids formed during transamination are altered
so they can easily enter the Krebs cycle
pathways.
Urea
CO2
Modified keto acid

Blood
Enter Krebs cycle in body cells
Urea
Krebs cycle
Kidney
Excreted in urine
Figure 24.16
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Initial stimulus
Blood glucose
Physiological response
Stimulates
Result
Beta cells of pancreatic islets
Blood insulin
Targets tissue cells
Active transport of amino acids into tissue cells
Facilitated diffusion of glucose into tissue cells
Protein synthesis
Enhances glucose conversion to
Cellular respiration
CO2 H2O
Fatty acids glycerol
Glycogen



Figure 24.20
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• Role of the Liver in Metabolism

• Detoxifies drugs and alcohol
• Degrades hormones
• Produce cholesterol, blood proteins (albumin and
  clotting proteins)
• Plays a central role in metabolism

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• Metabolic Functions of the Liver

• Glycogenesis
• Glucose to glycogen
• Glycogen molecules are stored in the liver
• Glycogenolysis
• Glucose to glycogen
• Gluconeogenesis
• Glucose is produced from fats and proteins

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• Metabolic Functions of the Liver

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• Cholesterol Metabolism

• Serves as a structural basis of steroid hormones
  and vitamin D
• Is a major building block of plasma membranes
• Most cholesterol is produced in the liver and is
  not from diet so taking in excess from the diet
  can be bad

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• Cholesterol Transport

• transported by lipoproteins (lipid-protein
  complexes)
• Low-density lipoproteins (LDLs) transport to body
  cells
• High-density lilpoproteins (HDLs) transport from
  body cells to the liver

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• Regulation of Food Intake

• Body weight is usually relatively stable
• Energy intake and output remain about equal
• Mechanisms that may regulate food intake
• Levels of nutrients in the blood
• Hormones
• Body temperature
• Psychological factors

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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

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• Metabolic Rate and Body Heat Production

• Basic metabolic rate (BMR) heat/time
• Factors that influence BMR
• Surface area
• Gender

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• Metabolic Rate and Body Heat Production

• Factors that influence BMR (continued)
• Age
• The amount of thyroxine
• More thyroxine higher metabolic rate

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• Total Metabolic Rate (TMR)

• Total amount of kilocalories the body must
  consume to fuel ongoing activities
• TMR increases with an increase in body activity
• TMR must equal calories consumed to maintain
  homeostasis and maintain a constant weight

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Long-term controls
Short-term controls
Stretch (distension of GI tract)
Vagal afferents
Hypothalamus
Brain stem
Release melano- cortins
Release CRH
VMN (CRH- releasing neurons)
Satiety (appetite suppression)
POMC/ CART group
Solitary nucleus
Glucose Amino acids Fatty acids
Nutrient signals
Insulin PYY CCK
Gut hormones
Insulin (from pancreas)
Leptin (from lipid storage)
ARC nucleus
Ghrelin Glucagon Epinephrine
Gut hormones and others
LHA (orexin- releasing neurons)
Hunger (appetite enhancement)
NPY/ AgRP group
Stimulates
Inhibits
Release NPY
Release orexins
Figure 24.24
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• Body Temperature Regulation

• Most energy is released as foods are oxidized
• Most energy escapes as heat
• Must remain between 35.6 to 37.8C (96 to 100
  F)
• The bodys thermostat is in the hypothalamus

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• Heat Promoting Mechanisms

• Vasoconstriction of blood vessels
• Shivering

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• Heat Loss Mechanisms

• Heat loss from the skin via radiation and
  evaporation
• Skin blood vessels and capillaries are flushed
  with warm blood
• Evaporation of perspiration cools the skin