Chapter 27 Nutrition and Metabolism

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Chapter 27Nutrition and Metabolism
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Overview Nutrition and Metabolism

• Nutrition food (nutrients) humans eat
• Malnutrition a deficiency of food, vitamins, and
  minerals
• Categories of nutrients
• Macronutrients nutrients needed in large amounts
  (bulk nutrients)
• Macromolecules such as carbohydrates, fats
  (lipids), and proteins
• Water
• Macrominerals
• minerals needed in large quantity
• for example, sodium, chloride, and calcium
• Micronutrients nutrients needed in very small
  amounts
• Vitamins
• Microminerals (trace elements)
• minerals such as iron, iodine, zinc, that are
  needed only in very small quantities

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Metabolism

• Metabolism use of food
• the use of nutrients
• a process made up of many chemical processes
• Catabolism- breaks food down into smaller
  molecular compounds and releases two forms of
  energy heat and chemical energy
• Anabolism a synthesis process
• Occur constantly
• Chemical energy released by catabolism must be
  transferred to ATP, which is used in the cells

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Chemical Energy in Food

• How much energy is in food?
• When 1 gram of glucose (C6H12O6) is burned in the
  presence of oxygen, 3811 calories are released.
• What is a calorie? A calorie is the amount of
  energy needed to raise the temperature of 1 gram
  of water 1 degree Celsius.
• On a food label Calories (with a capital C)
  represent kilocalories. 1 kilocalorie 1000
  calories.
• Cells use the energy in glucose by slowly
  releasing it.

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Carbohydrates

• Dietary sources of carbohydrates
• Complex carbohydrates
• Polysaccharides starches
• found in vegetables and grains
• glycogen is found in meat
• Cellulose
• a component of most plant tissue
• passes through the digestive system without being
  broken down
• Fiber, roughage

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Carbohydrates

• Disaccharides found in refined sugar
• must be broken down before they can be absorbed
• Monosaccharides found in fruits
• move directly into the internal environment
  without being processed directly
• Glucose
• carbohydrate most useful to the human cell
• can be converted from other monosaccharides

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Know for test!
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Carbohydrates

• Carbohydrate metabolism human cells catabolize
  most of the carbohydrate absorbed and anabolize a
  small portion of it
• Glycolysis the first process of carbohydrate
  catabolism
• of a series of chemical reactions (Figure 27-3)
• Glycolysis occurs in the cytoplasm of all human
  cells
• An anaerobic process provides cells with energy
  under conditions of inadequate oxygen
• It breaks down chemical bonds in glucose
  molecules and releases about 5 of the energy
  stored in them
• It prepares glucose for the 2nd step in
• catabolism the citric acid cycle
• Produces 2 pyruvic acid, 2 (net) ATP,
• and 2 NADH!

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• FYI!

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Carbohydrate metabolism

• Citric acid cycle
• formerly called Krebs cycle after Sir Hans Krebs,
  who discovered this process
• By the end of the reactions of the citric acid
  cycle, two pyruvic acids have been broken down to
  6 carbon dioxide, 6 NADH, 2 FADH2 and 6 water
  molecules (Figures 27-4 and 27-5)

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FYI!
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Know for test!
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DING! The magical world of electron transport!

• What purpose is the NADH and FADH2?
• Electron transport chain (or system) in the
  mitochondria
• http//www.science.smith.edu/departments/Biology/B
  io231/etc.html
• These molecules are very HIGH ENERGY!
• In the mitochondria, for every
• NADH ? 3 ATP
• FADH2 ? 2 ATP

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Carbohydrate metabolism

• Electron transport chain (ETC) (Figure 27-6)
• NADH and FADH2 removed during CAC enter a chain
  of molecules that are embedded in the inner
  membrane of the mitochondria
• As electrons move down the chain, they release
  small bursts of energy to pump protons between
  the inner and the outer membrane of the
  mitochondrion
• Protons move down their concentration gradient
  and across the inner membrane, driving
  ATP-synthase
• Oxidative phosphorylation the joining of a
  phosphate group to ADP (di) to form ATP (tri) by
  the action of ATP synthase
• http//www.sp.uconn.edu/terry/images/anim/etsanim
  .gif

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• Must understand the concept but not the names of
  the proteins (except ATP synthase)

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ATP Synthase
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Carbohydrate Metabolism

• The anaerobic pathway- Lactic Acid Fermentation
• Without O2
• a pathway for the catabolism of glucose
• transfers energy to ATP using only glycolysis
• Converts NADH back to NAD
• paying the oxygen debt- Box 27-4

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Oxygen uptake during and after exercise
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Glucose Use

• Glycogenesis
• Glucose join together ? strand of glucose beads
  glycogen
• a process that operates when the blood glucose
  level increases above the midpoint of its normal
  range (Figures 27-11)
• Glycolysisthe first process of carbohydrate
  catabolism
• in cytoplasm of all human cells
• An anaerobic process
• It breaks down chemical bonds in glucose
  molecules and releases about 5 of the energy
  stored in them
• It prepares glucose for the second step in
  catabolismthe citric acid cycle

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Control of Glucose Metabolism

• Hormonal and neural devices maintain homeostasis
  of blood glucose concentration
• Insulin
• secreted by beta cells in pancreas
• decreases blood glucose level
• Glucagon
• Secreted by alpha cells in pancreas
• Breaks down glycogen only in liver ?
• increases blood glucose level
• Epinephrine
• hormone secreted in times of stress by adrenal
  medulla
• Breaks down glycogen in liver AND muscles ?
  increases blood glucose level

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Control of Glucose Metabolism

• Adrenocorticotropic hormone (ACTH)
• stimulates adrenal cortex to increase its
  secretion of glucocorticoids
• Glucocorticoids accelerate gluconeogenesis
• Gluconeogenesis is the formation of new glucose
  from proteins and fats
• Increases blood glucose levels
• Growth hormone
• Made by pituitary
• increases blood glucose level by shifting from
  carbohydrate to fat catabolism

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Carbohydrate Metabolism

• Hormones that cause the blood glucose level to
  rise are called hyperglycemic
• Insulin is hypoglycemic because it causes the
  blood glucose level to decrease

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Lipids

• Dietary sources of lipids
• Triglycerides
• the most common lipids
• Composed of a glycerol subunit that is attached
  to 3 fatty acids
• Phospholipids an important lipid found in all
  foods
• Cholesterol an important lipid found only in
  animal foods
• Used in cell membrane
• Dietary fats
• Saturated fats contain no double bonds
• Unsaturated fats contain some double bonds

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Lipids

• Lipoproteins and fatty acids are transported in
  the blood
• 95 of lipids are in the form of lipoproteins
• Consists of lipids protein
• Formed in the liver
• Blood contains 3 types of lipoproteins
• very low density
• Low Density (LDL)
• High Density (HDL)
• Cholesterol lipoproteins associated with heart
  disease

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Proposed Functions of Lipoproteins

• Some people have very few LDL receptors on the
  surface of their cells and cannot store excess
  cholesterol inside the cell so it accumulates in
  the blood
• High levels of LDL leads ? high risk of
  atherosclerosis (hardening of the arteries) ?
  high risk for heart attack or stroke

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Proposed Functions of Lipoproteins

• High HDL levels ? low risk of atherosclerosis
• HDL binds to the surface of a cell and stimulates
  the release of cholesterol which HDL takes to the
  liver for excretion
• High LDL (gt180mg)- lots of cholesterol is being
  delivered
• High HDL (gt60mg)- lots of cholesterol is being
  removed

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Omega-3 fatty acids

• An essential fatty acid- our body is unable to
  produce polyunsaturated fats so we must eat them
  in order to obtain them
• Fish contain this fat in their cell membranes
• This is what causes fish from very cold areas to
  be oily and not freeze
• fish oil
• Examples salmon, herring, trout

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Lipids

• Lipid metabolism
• Lipid catabolism
• beta-oxidation ? acetyl-CoA ? citric acid cycle
• Lipid anabolism
• lipogenesis
• Control of lipid metabolism is through the
  following hormones
• Insulin
• Growth hormone
• ACTH
• Glucocorticoids

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Proteins

• Sources of proteins
• 20 different amino acids
• The body synthesizes amino acids from other
  compounds in the body
• Only about half of the necessary types of amino
  acids can be produced by the body
• the rest are supplied through dietfound in both
  meat and vegetables

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Proteins

• Protein metabolism anabolism is primary, and
  catabolism is secondary
• Protein anabolism process by which proteins are
  synthesized by ribosomes
• Protein catabolism deamination takes place in
  liver cells and forms an ammonia molecule, which
  is converted to urea and excreted in urine, and a
  keto acid molecule, which is oxidized or
  converted to glucose or fat
• Protein balance rate of protein anabolism
  balances rate of protein catabolism
• Nitrogen balance amount of N taken in N out
  thru protein catabolic waste
• Two kinds of protein or nitrogen imbalance
• Negative nitrogen balance
• protein catabolism exceeds protein anabolism
• more tissue proteins are catabolized than are
  replaced by protein synthesis
• Positive nitrogen balance
• protein anabolism exceeds protein catabolism
• Control of protein metabolism achieved by
  hormones

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• This may have certain things you do NOT need to
  know for the test!

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Vitamins

• Vitamins
• organic molecules necessary for normal metabolism
• many attach to enzymes and help them work or have
  other important biochemical roles
• The body does not make most of the necessary
  vitamins
• they must be obtained through diet
• Body stores fat-soluble vitamins (D,A,K, and E)
• Taken up in the small intestine
• These molecules are predominantly non-polar
• Body does NOT store water-soluble vitamins
• These molecules are predominantly polar

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Vitamins- do NOT memorize locations
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Minerals

• Minerals
• inorganic elements or salts found in the earth
• Attach to enzymes and help them work and function
  in chemical reactions
• Essential to the fluid/ion balance of internal
  fluid environment
• Are involved in many processes in the body such
  as muscle contraction, nerve function, hardening
  of bone, etc.
• Too large or too small an amount of some minerals
  may be harmful
• Recommended mineral intakes may vary over the
  lifespan

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Metabolic Rates

• Metabolic rate means the amount of energy
  released by catabolism
• Metabolic rates are expressed in two ways
• Number of kilocalories (C) of heat energy
  expended per hour or per day
• As normal or as a percentage above or below
  normal
• Basal metabolic rate rate of energy expended
  under basal (base) conditions
• Factors
• Size Body composition
• Sex Age
• Thyroid hormone Body temperature
• Drugs other factors

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Metabolic Rates

• Total metabolic rate- the amount of energy used
  over time
• Main determinates
• Basal metabolic rate
• Energy used to do skeletal muscle work
• Thermic effect of foods
• Energy balance and weight the body maintains a
  state of energy balance
• Body maintains weight when the total calories in
  the food ingested equals the total metabolic rate
• Body weight increases when energy input exceeds
  energy output
• Body weight decreases when energy output exceeds
  energy input
• In starvation, carbohydrates are used up first,
  then fats, then proteins (Figure 27-32)

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Mechanisms for Regulating Food Intake

• Hypothalamus plays a part in food intake
• Feeding centers in hypothalamus exert primary
  control over appetite
• Appetite center
• Cluster of neurons in hypothalamus when
  stimulated, increases appetite
• Orexigenic effects factors that trigger appetite
• Satiety center
• Group of neurons in the hypothalamus that, if
  stimulated, brings about decreased appetite
• Anorexigenic effects factors that suppress
  appetite (anorexia is loss of appetite)

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Anorexia Nervosa

• Self-induced weight loss, negative perception of
  body image, and changes in their body due to
  nutritional depletion
• Predominantly in young, single females, and may
  be inherited.
• Abnormal menstruation, amenorrhea, and a lowered
  BMR
• Associated disorders are
• Osteoporosis
• Depression
• Brain abnormalities

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The Big Picture Nutrition, Metabolism, and the
Whole Body

• Every cell in the body needs the maintenance of
  the metabolic pathways to stay alive
• Anabolic pathways build the various structural
  and functional components of the cells
• Catabolic pathways convert energy to a usable
  form and degrade large molecules into subunits
  used in anabolic pathways

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The Big Picture Nutrition, Metabolism, and the
Whole Body

• Cells require appropriate amounts of vitamins and
  minerals to produce structural and functional
  components necessary for cellular metabolism
• Other body mechanisms operate to ensure that
  nutrients reach the cells