Nutrition, Metabolism, Nutrition, Metabolism, and Body Temperature and Body Temperature Regulation Regulation Objectives: For each major nutrient (carbohydrates, lipids and proteins) as well as vitamins and minerals, provide a description of 1.basic structure (monomers), function in body and RDA 2.Description of mechanisms of digestion and unique requirements for absorption 3.Role of the nutrient, vitamin or mineral in production of ATP 4.Diseases or syndromes associated with excess or deficits of a specific nutrient, vitamin or mineral
Transcript
Nutrition, Metabolism, Nutrition, Metabolism, and Body Temperature and Body Temperature
RegulationRegulation
Objectives:For each major nutrient (carbohydrates, lipids and proteins) as well as
vitamins and minerals, provide a description of 1.basic structure (monomers), function in body and RDA
2.Description of mechanisms of digestion and unique requirements for absorption
3.Role of the nutrient, vitamin or mineral in production of ATP4.Diseases or syndromes associated with excess or deficits of a specific
nutrient, vitamin or mineral
NutritionNutrition
Nutrient: a substance in food that promotes normal growth, maintenance, and repair
Major nutrients◦Carbohydrates, lipids, and proteins
Other nutrients ◦Vitamins and minerals (and, technically
speaking, water)
Figure 23.1a
(a) USDA food guide pyramid
Grains
Vegetables
Fruits
Meat andbeans
Oils
Milk
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
Figure 23.5
Via oxidativephosphorylationVia substrate-level
phosphorylation
MitochondrionMitochondrialcristaeCytosol
KrebscycleGlucose
Glycolysis
Pyruvicacid
Electron transportchain and oxidativephosphorylation
Chemical energy (high-energy electrons)
1 During glycolysis, each glucose molecule is broken down into two molecules of pyruvic acid in the cytosol.
2 The pyruvic acid then enters the mitochondrial matrix, where the Krebs cycle decomposes it to CO2. During glycolysis and the Krebs cycle, small amounts of ATP are formed by substrate-level phosphorylation.
3 Energy-rich electrons picked up bycoenzymes are transferred to the elec-tron transport chain, built into the cristae membrane. The electron transport chain carries out oxidative phosphorylation, which accounts for most of the ATP generated by cellular respiration.
Chemical energy
Figure 23.6 (3 of 3)
To Krebscycle
(aerobicpathway)
2
2
4 ADP
2 Lactic acid
2 Pyruvic acid
Dihydroxyacetonephosphate
Glyceraldehyde3-phosphate
Phase 3Sugar oxidationand formationof ATPThe 3-carbon frag-ments are oxidized (by removal of hydrogen) and 4 ATP molecules are formed
Carbon atomPhosphate
2 NAD+
2 NAD+
NADH+H+
NADH+H+
Glycolysis Electron trans-port chain and oxidativephosphorylation
Krebscycle
Figure 23.7
Krebs cycle
NAD+
NAD+
GDP +
NAD+
FAD
NAD+
NADH+H+
Cytosol
Mitochondrion(matrix)
NADH+H+
FADH2
NADH+H+
Citric acid
(initial reactant)
Isocitric acid
Oxaloacetic acid
(pickup molecule)
Malic acid
Succinic acidSuccinyl-CoA
GTP
ADP
Carbon atom
Inorganic phosphate
Coenzyme A
Acetyl CoA
Pyruvic acid from glycolysis
Transitionalphase
Fumaric acid
NADH+H+
CO2
CO2
CO2
-Ketoglutaric acid
Electron trans-port chain and oxidativephosphorylation
Glycolysis Krebscycle
Figure 23.8
Intermembranespace
Innermitochondrialmembrane
Mitochondrialmatrix
NADH + H+
NAD+
FAD
(carryingfrom food)
FADH2
Krebscycle
GlycolysisElectron transportchain and oxidativephosphorylation
Electron Transport Chain Chemiosmosis
ADP +
2 H+ +
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.
ATPsynthase
12
Figure 23.9
Glycolysis Krebscycle
Electron trans-port chain and oxidativephosphorylation
EnzymeComplex I
EnzymeComplex III
EnzymeComplex IV
EnzymeComplex II
NADH+H+
FADH2
Fre
e e
nerg
y r
ela
tive t
o O
2 (
kcal/
mol)
Figure 23.11
Mitochondrial matrix
Intermembrane space
ADP+
A stator anchored in the membrane holds the knob stationary.
As the rotor spins, a rod connecting the cylindrical rotor and knob also spins.
The protruding, stationary knob contains three catalytic sites that join inorganic phosphate to ADP to make ATP when the rod is spinning.
A rotor in the membrane spins clockwise when H+
flows through it down the H+ gradient.
CarbohydratesCarbohydrates
Dietary sources◦Starch (complex carbohydrates) in grains and
vegetables◦Sugars (simple carbohydrates) in fruits,
sugarcane, sugar beets, honey and milk◦Monosaccharides: ◦Insoluble fiber: cellulose in vegetables;
provides roughage◦Soluble fiber: pectin in apples and citrus fruits;
Digestion◦Amylase in mouth◦Pancreatic amylase in duodenum◦Maltase, lactase in brush border of intestinal
villi cellsAbsorption
◦Glucose and galactose: cotransportation with sodium ions
◦Fructose: facilitated diffusion◦All monosaccharides enter capillaries through
facilitated diffusion and head to liver through hepatic portal vein.
CarbohydratesCarbohydrates
Metabolism◦Glucose provides 32 ATP in oxidative respiration
◦Glycogenesis: production of glycogen when ATP levels are high
◦Glycogenolysis: When blood glucose levels drop, glycogen is split. Liver glycogen produces glucose for other organs and skeletal muscle
◦Carbohydrate loading is used to increase glycogen before a major race or event
◦Gluconeogenesis: When too little glucose is available, glycerol and amino acids are converted to glucose/ this is “new” glucose from noncarbohydrate sources
Carbohydrate Carbohydrate and Sugar and Sugar structuresstructures
Figure 23.13
Cell exterior
Hexokinase(all tissue cells)
Cell interior
Mutase
GlycogenesisGlycogenolysis
Mutase
ADP
Glucose-6-phosphatase(present in liver,kidney, andintestinal cells)
Glycogensynthase
Glycogenphosphorylase
Pyrophosphorylase
2
Blood glucose
Glucose-6-phosphate
Glucose-1-phosphate
Glycogen
Uridine diphosphateglucose
When glucose supplies exceed demands, glycogenesis occurs and glucose is converted to glycogen
Falling blood glucose levels stimulate glycogenolysis or the breakdown of glycogen in order to release glucose
Which of these processes would be used in carb loading?
LipidsLipids
Dietary sources◦Triglycerides: primary form of “fat” carried in the blood
from the food we eat and stored as “fat” Saturated fats (meat, dairy foods, and tropical oils) Unsaturated fats (seeds, nuts, olive oil, and most
vegetable oils)◦Cholesterol (egg yolk, meats, organ meats, shellfish,
and milk products)/ not an energy sourceEssential fatty acids
◦Linoleic and linolenic acid, found in most vegetable oils
Essential uses of lipids in the body◦Help absorb fat-soluble vitamins◦Major fuel of hepatocytes and skeletal muscle◦Phospholipids are essential in myelin sheaths
and all cell membranes
The structure shown here is a phospholipid
Synthesis of Structural MaterialsSynthesis of Structural Materials
Phospholipids for cell membranes and myelin
Cholesterol for cell membranes and steroid hormone synthesis
In the liver ◦Synthesis of transport lipoproteins for
cholesterol and fats◦Synthesis of cholesterol from acetyl CoA◦Use of cholesterol to form bile salts
Lipoproteins enable lipids to be Lipoproteins enable lipids to be carried in bloodstreamcarried in bloodstream
High Density Lipoproteins
Low Density Lipoproteins
Collect cholesterol from body tissues and carries it back to liver
Carry cholesterol from liver to cells of body
One is considered good and the other bad…both are needed, it’s the ratio of one to the other that is important. Look up correct blood levels of each.
LipidsLipids
Functions of fatty deposits (adipose tissue)◦Protective cushions around body organs◦Insulating layer beneath the skin◦Concentrated source of energy
LipidsLipids
Regulatory functions of regulatory molecules; prostaglandins◦Prostaglandins formed from linoleic acid◦Primarily act as paracrines
Smooth muscle contraction Control of blood pressure Inflammation
Functions of cholesterol◦Stabilizes membranes◦Precursor of bile salts
and steroid hormones
LipidsLipids
Dietary requirements suggested by the American Heart Association◦Fats should represent 30% or less of total
caloric intake◦Saturated fats should be limited to 10% or less
of total fat intake◦Daily cholesterol intake should be no more than
300 mg
LipidsLipids
Digestion◦Requires bileemulsion
◦Pancreatic lipases primarily in duodenum and jejunum
Absorption◦Assisted by bile to
become micelles; little “clumps” of fatty elements in intestinal lumen
◦Enter intestinal cells through diffusion
◦Chylomicrons are extruded into lacteals via exocytosis
LipidsLipids
Lipid Metabolism◦Fats are the body’s most concentrated source
of energy◦Yield 9 kcal per gram of fat◦Most fat is transported in lymph as
chylomicrons Hydrolyzed by enzymes in capillary endothelium Fatty acids and glycerol are taken up by cells
primarily through simple diffusion
Lipid MetabolismLipid Metabolism
Glycerol is converted to glyceraldehyde phosphate◦Enters the Krebs cycle◦Equivalent to 1/2 glucose
Lipogenesis Lipogenesis
Triglyceride synthesis occurs when cellular ATP and glucose levels are high
Glucose is easily converted into fat because acetyl CoA is ◦An intermediate in glucose catabolism ◦A starting point for fatty acid synthesis
LipolysisLipolysis
The reverse of lipogenesis: triglycerides are broken down or oxidized
Oxaloacetic acid is necessary for complete oxidation of fat◦Without it, acetyl CoA is converted by
ketogenesis in the liver into ketone bodies (ketones)
Figure 23.14
Krebscycle
Glycerol Fatty acids
Coenzyme A
Lipase
Oxidationin the mito-chondria
Cleavageenzymesnips off2C fragments
Glycolysis
Glyceraldehydephosphate
(a glycolysis intermediate)
Pyruvic acid
Lipids
Acetyl CoA
FAD
H2O
NAD+
NADH + H+
FADH2
Lipids (summary of metabolism)Lipids (summary of metabolism)
Lipogenesis: storage of excess glycerol and fatty acids as triglycerides in subcutaneous tissue◦Additional triglycerides can also be made from
acetyl CoA (an intermediate in glucose metabolism…feeds into the Krebs cycle). For this reason, glucose is easily converted to fat
Lipolysis: releasing fatty acids and glycerol into blood. ◦Can be used as fuel, feeding into Krebs cycle
LipidsLipids
Ketogenesis: if not enough carbohydrates for all components of Krebs, then acetyl CoA builds up◦Liver converts acetylCoA molecules to ketone
bodies or ketones, which are released into the blood
◦These ketones can be used for gluconeogenesis or put into Krebs cycle in cells
◦Excess ketones are broken down and excreted in urine
◦However, if excess builds up in blood (ketosis), causes drop in blood pH, (ketoacidosis)
LipidsLipids
Most ketone bodies can be metabolized in Krebs cycle… however excess ketones in blood indicates metabolic disease
Figure 23.15
ElectrontransportCholesterol
Stored fatsin adipose
tissue
Dietary fats
Glycerol
GlycolysisGlucose
Glyceraldehydephosphate
Pyruvic acid
Acetyl CoA
CO2 + H2O+
Steroids
Bile salts
Fatty acids
Ketonebodies
Triglycerides(neutral fats)
Certainaminoacids
Ketogenesis (in liver)
Catabolic reactions
Anabolic reactions
Lipogenesis
Krebscycle
ProteinsProteins
Dietary sources◦Eggs, milk, fish, and most meats contain complete proteins
◦Legumes, nuts, and cereals contain incomplete proteins (lack some essential amino acids)
◦Legumes and grains (cereals) together contain all essential amino acids
Figure 23.2
Corn andother grains
Beansand otherlegumes
Tryptophan
Methionine
Valine
Threonine
Phenylalanine
Leucine
Isoleucine
Lysine
Vegetarian diets providing the eightessential amino acids for humans
muscle proteins◦Most functional molecules: enzymes, some
hormones
ProteinsProteins
Use of amino acids in the body1. All-or-none rule
All amino acids needed must be present for protein synthesis to occur
2. Adequacy of caloric intake Protein will be used as fuel if there is
insufficient carbohydrate or fat available
ProteinsProteins
3. Nitrogen balance State where the rate of protein synthesis
equals the rate of breakdown and loss Positive if synthesis exceeds breakdown
(normal in children and tissue repair) Negative if breakdown exceeds synthesis (e.g.,
stress, burns, infection, or injury)4. Hormonal controls
Anabolic hormones (GH, sex hormones) accelerate protein synthesis
ProteinsProteins
Dietary requirements◦Rule of thumb: daily intake of 0.8 g per kg body
weight◦Amount of protein varies greatly◦Certain stages of life requiring more protein
Protein diet with exerciseused to lose weightprotein reduces hungerincreases fat lossimproves blood nutrient levelsmajor risk is related to kidney function
ProteinProteinStructureStructure
Amino Acid structureAmino Acid structure
ProteinsProteins
Digestion◦Pepsin in stomach◦Pancreatic enzymes:
trypsin, chymotrypsin, carboxypeptidase in duodenum and jejunum
◦Amino acids leave the epithelial cells by facilitated diffusion and transported to liver through hepatic portal vein
ProteinsProteins
Metabolism◦Your body replaces tissue proteins from ingested
amino acids at a rate of 100g/day (anabolic; protein synthesis)
◦If you have excess protein in diet, amino acids are oxidized for energy or converted to fat for future needs Before amino acids can be used for energy they
must be deaminated (amino acid removed) Then they can be oxidized in Krebs cycle or
converted to glucose End products: keto acid (former amino acid) and
urea made from amine/ ammonia
VitaminsVitamins
Organic compounds Crucial in helping the body use nutrients Most function as coenzymesVitamins D, some B, and K are
synthesized in the body
VitaminsVitamins
Two types, based on solubility1. Water-soluble vitamins
B complex and C are absorbed with water B12 absorption requires intrinsic factor Not stored in the body
2. Fat-soluble vitamins A, D, E, and K are absorbed with lipid digestion
products Stored in the body, except for vitamin K Vitamins A, C, and E act as antioxidants
MineralsMinerals
Seven required in moderate amounts:◦Calcium, phosphorus, potassium, sulfur,
sodium, chloride, and magnesiumOthers required in trace amountsWork with nutrients to ensure proper body
functioningUptake and excretion must be balanced to
prevent toxic overload
MineralsMinerals
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
Two types of reactions◦Anabolism: synthesis of large molecules from
small ones◦Catabolism: hydrolysis of complex structures to
simpler ones
MetabolismMetabolism
Cellular respiration: catabolism of food fuels and capture of energy to form ATP in cells
Enzymes shift high-energy phosphate groups of ATP to other molecules (phosphorylation)
Phosphorylated molecules are activated to perform cellular functions
Figure 23.3
Stage 1 Digestion in GI tract lumen to absorbable forms.Transport via blood totissue cells.
Stage 2 Anabolism (incorporation into molecules) and catabolism of nutrients to form intermediates within tissue cells.
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, formingwater. Some energy released isused to form ATP.
Catabolic reactionsAnabolic reactions
Glycogen
PROTEINS
Proteins Fats
CARBOHYDRATES
Glucose
FATS
Amino acids Glucose and other sugars Glycerol Fatty acids
Pyruvic acid
Acetyl CoA
Infrequent CO2
NH3
H
Krebscycle
Oxidativephosphorylation
(in electron transport chain)
O2
H2O
Stages of MetabolismStages of Metabolism
Processing of nutrients1. Digestion, absorption and transport to tissues2. Cellular processing (in cytoplasm)
Synthesis of lipids, proteins, and glycogen, or Catabolism (glycolysis) into intermediates
3. Oxidative (mitochondrial) breakdown of intermediates into CO2, water, and ATP
