Transcript 8a Nutrition and Metabolism

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 source of vitamins & minerals
Major protein source
some vitamins
Major source of carbohydrates & B vitamins
Major source of lipids and
fat soluble vitamins A,D,E, K
Major source of minerals and
vitamins A and D, some protein
White rice, white bread,
potatoes, pasta, sweets:
use sparingly
Red meat, butter:
use sparingly
Dairy or calcium
supplement: 1–2 servings
Fish, poultry, eggs:
0–2 servings
Nuts, legumes:
1–3 servings
Fruits:
2–3 servings
Vegetables in
abundance
Whole-grain
foods at
most meals
Daily excercise and weight control
Plant oils
at most
meals
(b) Healthy eating pyramid
Figure 24.1b
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
Oxidation-Reduction is Important in Energy Production
 In biological systems, the electrons are often associated with hydrogen atoms.
Biological oxidations are often dehydrogenations.
Or FAD+
FADH2
Sugars, amino acids,
fatty acids
Figure 5.10
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
Energized ATP:
ADP
Discharged ATP:
ADP
Powering the synthesis of
molecule Z by coupling
oxidation to reduction:
P
P
X
+
Y
Z
Metabolic Pathways Involved in Cellular Respiration
An oxidation of glucose to reduce ADP to ATP
34
Overall Equation for Cellular Respiration
Aerobic Cellular Respiration
C6H12O6 + O2
sugar
oxygen
CO2 + H2O
carbon dioxide water
CO2
+ 34ATP
usable energy
glucose
Glycolysis
Cell
membrane
CO2
NAD
2 ATP
(substrate-level
phosphorylation)
NADH
2 pyruvates
CO2
4 ATP
Linking Step
mitochondrion
(substrate-level
phosphorylation)
Acetyl CoA
Krebs
Cycle
Electron
Transport
Chain and
ATP Synthase
O2
H 2O
30 ATP
(oxidative
phosphorylation)
ATP Synthase
ATP fuels
construction/synthesis
reactions inside the cell
Nutrition and Metabolism
 Dietary Sources of Major
Nutrients
 Basics of Cellular Respiration
 Metabolism of the Three
Macronutrients:
Carbohydrates, Fats, and
Protein
 Central Role of the Liver in
Digestion/Metabolism
 Cholesterol and Lipid Transport
 Absorptive and Postabsorptive
States
 Developmental Aspects of
Metabolism
Fat Metabolism
 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
 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)
in liver
•
acetone and
acetoacetic
acid =
ketosis/acidosis
Protein Metabolism
urea
deamination
Three Macronutrients Used for ATP Production
Stage 1 Digestion in
GI tract lumen to
absorbable forms.
Transport via blood to
tissue cells.
PROTEINS
CARBOHYDRATES
Amino acids
Glucose and other sugars
Stage 2 Anabolism
Proteins
(incorporation into
molecules) and
catabolism of nutrients
NH3
to form intermediates
within tissue cells.
FATS
Glycerol
Glycogen
Glucose
Fatty acids
Fats
Pyruvic acid
Acetyl CoA
Stage 3 Oxidative breakdown
of products of stage 2 in
Infrequent
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
H
CO2
Oxidative
phosphorylation
(in electron
transport chain)
O2
H2O
Catabolic reactions
Anabolic reactions
Figure 24.3
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
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
Keeping membranes fluid
Vitamin D synthesis
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 high
Over 240 - high
LDL cholesterol (mg/dL)
Below 100 - optimal
100-129
- near optimal
130-159
- borderline high
160-189
- high
Above 190 - very high
HDL cholesterol (mg/dL)
Below 40
- low
60 or above - high
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
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
•
brain
damage and
retardation
in infancy
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
PKU
 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
Tracheoesophageal Fistula
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