Nutrition and Metabolism: Energy Balance and Appetite Regulation

Nutrition and Metabolism Overview

Nutrition and
metabolism
chapter 26Nutrition and metabolism
Dietary nutrients are broken down and absorbed
For building blocks and for energy

Nutrition Fundamentals

Key Questions in Nutrition

Nutrition
1
What are
carbohydrates,
lipids and
proteins used
for?
Metabolism
How is metabolism of
carbohydrates, lipids
and proteins?
What are the
metabolic states?
What are vitamins
and minerals for?
What is the function
of the liver?
Energy balance
1
How is food intake
regulated?
What factors affect
the metabolic rate?
How is the body
temperature
regulated?

Outline of Topics

• Nutrition
• Carbohydrate metabolism
• Lipid and protein metabolism
• Metabolic states and metabolic rates
• Body heat and thermoregulation

Appetite Regulation

Appetite Regulators

Appetite

• Short-term regulators of appetite
• Ghrelin
• Peptide YY (PYY)
• Cholecystokinin (CCK)
• Amylin
• Long term regulators of appetite
• Leptin
• insulin

Arcuate Nucleus and Appetite

Appetite regulation

• Arcuate nucleus of
  hypothalamus
• neural networks
  involved in hunger

1. neuropeptide Y (NPY)

• Gherlin stimulates
  neuropeptide Y
  secretion
• Insulin, PYY, and leptin
  inhibit it

1. melanocortin

• Leptin stimulates
  melanocortin secretion
  Satiety
  Hunger
  Arcuate nucleus
  of hypothalamus
  Melano-
  cortin-
  secreting
  neurons
  Forebrain
  NPY-
  secreting
  neurons
  Key
  -> Stimulatory
  effect
  - Inhibitory
  effect
  Ghrelin
  PYY
  CCK
  Insulin
  Leptin
  Stomach
  Large
  intestine
  Small
  intestine
  Pancreas
  Adipose tissue

Nutrients and Dietary Guidelines

Types of Nutrients

Nutrients
. Nutrients are chemicals in food that cells use for
growth, maintenance and repair

• Nutrients include:
  Water
  Carbohydrates
  Lipids
  Proteins
  Minerals
  Vitamins

Dietary Reference Intakes

Dietary Reference Intakes (DRIs)
Recommended Daily Allowances (RDA)
. Safe estimate of daily intake that would meet the
nutritional needs of most healthy people
Adequate Intake (AI)
. Used instead of RDA if less certainty established for
needs
Essential nutrients cannot be synthesized in body
. Minerals, most vitamins, eight amino acids, and one to
three of the fatty acids must be consumed in diet

Carbohydrates

Carbohydrate Structure and Function

Carbohydrates

• Carbohydrate Structure and Function
• Sugars function as:
• Structural components of other molecules including
  nucleic acids, glycoproteins, glycolipids, ATP, and related
  nucleotides (GTP, cAMP)
• Hypoglycemia-deficiency of blood glucose
• Glycemic index (GI)

Carbohydrate Classification

Carbohydrates

• Monosaccharides- 1 unit

•
Glucose

• Fructose
• galactose
• Disaccharides- 2 units
• Sucrose
• lactose
• Polysaccharides- many units
• Starch
• Cellulose (fiber)

Fibers

Fibers

•
Fibrous material that resists
digestion

• Cellulose, pectin, gums, and lignins
• Water soluble fiber
• pectin
• Water insoluble fiber
• Cellulose
• Hemicellulose
• lignin

Lipids

Lipid Characteristics and Sources

Lipids

• Hydrophobic
• Compact energy substance
• Sources
• Saturated fats
• Animal origin-meat, egg yolks, dairy products
• Some in coconut and palm oils
• Unsaturated fats
• Found in nuts, seeds, and most vegetable oils
• Cholesterol
• Found in egg yolks, cream, shellfish, organ meats, and other
  meats

Serum Lipoproteins

Serum lipoproteins
. There are four classes of lipoproteins:

1. Chylomicrons - transport dietary lipids to adipose
   tissue
2. Very-low-density lipoproteins (VLDLs) - transport
   triglycerides from hepatocytes to adipocytes
3. Low-density lipoproteins (LDLs) - carry about 75% of
   the total cholesterol in blood and deliver it to cells
4. High-density lipoproteins (HDLs) - remove excess
   cholesterol from body cells and the blood and
   transport it to the liver for elimination

Proteins

Protein Functions and Nutritional Value

Proteins

• Proteins have a wide variety of functions
• Muscle contraction
• Motility of cilia and flagella
• Structural components
• Buffer pH of body fluids
• Contribute to resting membrane potentials of all cells
• Protein RDA is 46 to 56 g/day
• Nutritional value
• 8 essential amino acids
• 12 inessential amino acids

Minerals and Vitamins

Minerals

Minerals
. Inorganic elements that plants extract from soil or
water and introduce into the food web
. Not used as fuel

• Major minerals
• Calcium, phosphorus
• Trace minerals
• Iron, lodine

Vitamins

Vitamins
. Small dietary organic compounds that are
necessary for metabolism

• Water-soluble vitamins
• Vitamin C, B vitamins
• Fat-soluble vitamins
• Vitamin A, D, K, E
• Disorders
• Vitamin A deficiency

Metabolism Outline

Metabolism Topics

Outline

• Nutrition
• Carbohydrate metabolism
• Lipid and protein metabolism
• Metabolic states and metabolic rates
• Body heat and thermoregulation

Glucose Metabolism

Oxidative Carbohydrate Metabolism

Glucose metabolism
. Oxidative carbohydrate metabolism is glucose
catabolism
C6H1206 + 6 02 -> 6 CO2 + 6 H O+ ATP (energy)
Major pathways

1. Glycolysis
2. Anaerobic fermentation
3. Aerobic respiration

• Electron carriers
• FAD + 2 H -> FADH2
• NAD+ + 2 H -> NADH + H+

Glycolysis Process

Glycolysis

• Process whereby a 6-
  carbon glucose
  molecule is split into
  two 3-carbon
  molecules of pyruvic
  acid
• Net products
• 2 pyruvate
• ATP
• NADH +2H
  Key
  Glucose
  Carbon atoms
  ATP

·
Phosphate
groups
1
Phosphorylation
ADP
Glucose 6-phosphate
Glycogen
Fat
Fructose 6-phosphate
ATP
2 Priming
ADP
Fructose 1,6-diphosphate
3 Cleavage
2 PGAL
2 NAD+
2 P
2 NADH + 2 H+
4
Oxidation
2
2
ADP
2 H20+
>2 ATP
2
5
Dephosphorylation
2
ADP
2.
ATP
2
2 pyruvate

Anaerobic Fermentation

Anaerobic fermentation

• Absence of oxygen
• Pyruvic acid is reduced
  to lactic acid
• NADH transfers
  electrons to lactate
• Regenerate NAD+
• Glycolysis can continue
  Key
  Glucose
  Carbon atoms
  ATP
  Phosphate
  groups
  1 Phosphorylation
  ADP
  Glucose 6-phosphate
  Glycogen
  Fat
  Fructose 6-phosphate
  ATP
  2 Priming
  ADP
  Fructose 1,6-diphosphate
  3 Cleavage
  2 PGAL
  2 NAD+
  2 P
  2 NADH + 2 H+
  4 Oxidation
  2
  2 (ADP
  2 H20+
  2 ATP
  2
  5 Dephosphorylation
  2 (ADP
  >2 ATP
  2
  pyruvate
  2 NADH + 2 H+
  2 NAD+
  No O2 used
  O2 required
  2 0
  2 lactate
  Anaerobic fermentation
  Aerobic respiration

Aerobic Respiration

Aerobic respiration

• Most ATP is generated in mitochondria, which
  requires oxygen as final electron acceptor
• In the presence of oxygen, pyruvate enters the
  mitochondria and is oxidized by aerobic respiration
• Occurs in two principal steps
• Matrix reactions: their controlling enzymes are in the
  fluid of the mitochondrial matrix
• Membrane reactions: their controlling enzymes are
  bound to the membranes of the mitochondrial cristae

Aerobic Respiration Steps

Glucose metabolism- aerobic
respiration

• The oxidation of glucose to produce ATP is cellular
  respiration
• Four sets of reactions are involved:

1. Glycolysis
2. Formation of acetyl coenzyme A
3. Citric acid cycle
4. Electron transport chain reactions

ATP Production Pathways

Electrons
via NADH
Electrons
via NADH
Electrons
via NADH
and FADH2
GLYCOLYSIS
PYRUVATE
OXIDATION
OXIDATIVE
PHOSPHORYLATION
Glucose
Pyruvate
Acetyl CoA
CITRIC
ACID
CYCLE
(Electron transport
and chemiosmosis)
CYTOSOL
MITOCHONDRION
ATP
ATP
Substrate-level
Substrate-level
ATP
Oxidative

Formation of Acetyl Coenzyme A

2- Formation of acetyl
coenzyme A

• CO2 removed from pyruvate
  to make a C compound
• Convert C2
  compound to an
  acetyl group (acetic acid)
• NAD+ removes hydrogen
  atoms from the C2 compound
• Acetyl group binds to
  coenzyme A
• acetyl-CoA is delivered to
  citric acid cycle
  Pyruvate (C3)
  6
  CO2
  NAD+
  7
  NADH + H+
  Acetyl group (C2)
  8
  Acetyl-CoA
  Coenzyme A
  H20

Citric Acid Cycle

3- citric acid cycle

• Each acetyl group
  oxidized produces
• 1 ATP
• 1 FADH2
• 2 CO2
• 3 NADH
• The NADH and FADH,
  relay electrons
  extracted from food to
  the electron transport
  chain
  Coenzyme A
  H20
  9
  Citric acid (C6)
  Oxaloacetic acid (C4)
  10
  120
  NADH + H+
  (C6)
  18
  Citric
  acid
  cycle
  H20-
  11
  NADH + H+
  (C4)
  12
  CO2
  17
  (C5)
  H2O
  NAD+
  13
  Occurs in
  mitochondrial
  matrix
  NADH + H+
  16
  FADH 2
  (C4)
  CO2
  FAD
  (C4)
  Pi
  15
  GTP
  GDP
  ADP)
  ATP
  NAD+
  NAD+
  (C4)
  14

Electron Transport Chain

4- Electron transport chain

• The electron transport chain is a series of electron
  carriers in the mitochondria
  Each carrier in the chain is reduced as it picks up
  electrons and oxidized as it gives up electrons
  Exergonic reactions release energy used to form
  ATP
  Electrons depleted of energy are delivered to
  oxygen as final electron acceptor

Chemiosmotic Mechanisms of ATP Synthesis

Chemiosmotic Mechanisms of ATP
Synthesis

• Electron transfer in the ETC
  causes proteins to pump H+
  to the intermembrane
  space
• H+ then moves back across
  the membrane, passing
  through channels in ATP
  synthase
• ATP synthase uses the
  exergonic flow of H+ to
  drive phosphorylation of
  ATP
  Intermembrane
  space
  Matrix-
  Cristae
  Inner membrane
  Outer membrane
  6 H+
  NADH + H+
  NAD+
  1/2 O2 + 2 H+
  H2O
  Matrix
  A
  2.5 ADP + 2.5 P
  2e-
  2e-
  CoQ
  Inner
  membrane
  Enzyme
  complex
  1
  Enzyme
  complex
  2
  Enzyme
  complex
  3
  ATP
  synthase
  Cyt c
  Intermembrane-
  space
  2 H+
  2 H+
  2 H+
  Outer
  membrane
  M
  2.5 ATP

Overview of ATP Production

Overview of ATP production
Glucose
Glycolysis
2 ATP
(net)
2 NADH + 2 H+
2 pyruvate
Cytosol
Mitochondria
2 NADH + 2 H+
CO2
6 NADH + 6 H+
Citric acid
cycle
2
ATP
2 FADH2
3
ATP
Electron-transport
chain
25
ATP
Total 32
ATP
O2
H2O

Glycogen Metabolism

Glycogen Metabolism

• Glycogenesis
• Synthesis of glycogen
• Glycogenolysis
• Hydrolysis of glycogen
• Gluconeogenesis
• Synthesis of glucose
  from noncarbohydrates,
  such as glycerol and
  amino acids
  Blood
  glucose
  Extracellular
  Intracellular
  Glucose
  6-phosphatase
  (in liver, kidney,
  and intestinal cells)
  Hexokinase
  (in all cells)
  Glucose 6-phosphate
  P
  Glycogen
  synthase
  Key
  - Glycogenesis
  Glucose
  1-phosphate
  Glycogen
  - Glycogenolysis
  Pİ
  Glycogen
  phosphorylase
  Glycolysis
  Major Pathways of Glucose Storage and Use

Metabolism Outline Continued

Metabolism Topics Continued

Outline

• Nutrition
• Carbohydrate metabolism
• Lipid and protein metabolism
• Metabolic states and metabolic rates
• Body heat and thermoregulation

Lipid Metabolism

Lipogenesis and Lipolysis

Lipid metabolism

• Lipogenesis
• Synthesis of fat from
  other types of
  molecules
• Lipolysis
• Breaking down fat for
  fuel
• Glycerol
• Fatty acids
  Glucose
  >
  Glucose 6-phosphate
  Glycerol
  PGAL
  Stored
  triglycerides
  Fatty acids
  Glycerol
  Beta oxidation
  Pyruvate
  New
  triglycerides
  Acetyl groups
  Fatty
  acids
  Acetyl-CoA
  Ketone bodies
  ß-hydroxybutyric acid
  Acetoacetic acid
  Acetone
  Citric
  acid
  cycle
  Key
  - Lipogenesis
  - Lipolysis
  Pathways of Lipolysis and Lipogenesis in
  Relation to Glycolysis and the Citric Acid Cycle

Protein Metabolism

Amino Acid Pool and Reactions

Protein metabolism

• Amino acid pool
• Converted to other
  aa.
• Converted to
  glucose, fat, fuel
• Chemical reactions
• Deamination
• Amination
• transamination
  Glucose
  Pyruvate
  Protein
  ->
  -
  Amino
  acids
  Keto
  acids
  Acetyl-CoA
  Citric
  acid
  cycle
  -NH2
  a-ketoglutaric
  acid
  Urea
  cycle
  .CO2
  NH3
  Glutamic
  acid
  Urea
  Urine

Liver Functions

Liver's Role in Metabolism

Liver Functions in Metabolism

• Liver plays a wide
  variety of roles in
  carbohydrate, lipid, and
  protein metabolism
• Hepatitis
• inflammation of the
  liver is caused viruses
  (HVA to HVF)
• Cirrhosis
• Irreversible
  inflammatory liver
  disease
  Liver With Cirrhosis