Chapter 17 Nutrients and Metabolism Flashcards
What Is Nutrition?
Definition
* The study of nutrients in foods and also in an animal’s body
Clinical Importance of Pet Nutrition
*All cells in an animal’s body need a constant daily input of nutrients in order to stay healthy and functioning well
Difference between food and drugs
Food is any substance, usually comprised primarily of carbohydrates, fats, water and/or proteins, that can be eaten or drunk by animals (including humans) for nutrition and/or pleasure.
Drugs are any substance that enters the animal’s body that causes chemical changes in the animal’s body.
Nutrients
Substances derived from food; necessary for carrying out normal body functions
Six categories:
1. Water (most important) - inorganic
2. Carbohydrates
3. Lipids
4. Proteins
5. Vitamins
6. Minerals - inorganic
Some Nutrition Definitions
Nutrients – any substance ingested to support life
*Essential - Those that the animal species cannot manufacture and must be found in the diet every day.
* Organic - have the carbon atom multiple times in them
- carbs, fats, proteins, vitamins
Nutrient Divisions
Macronutrients
Micronutrients – nutrient molecules so small that no digestion is required before being absorbed
Macronutrients
Definition
* Large organic molecules that give structure and energy to the animal’s body (calories)
*Energy-producing nutrients
3 categories
* Carbohydrates
* Lipids (fats & oils)
*Proteins
Require digestion
Produce calories
Micronutrients
Definition
*Smaller molecules that are required by an animal for metabolism and homeostasis
* No digestion needed
* Non-energy-producing nutrients
3 categories
*Vitamins
* Minerals
* Water (H2O)
Dietary Sources of Macronutrients
Carbohydrates
-Sugars
—Simple carbohydrates (monosaccharides and disaccharides) found in fruit, honey, sugar cane, sugar beets, and immature vegetables
-Starches
—Complex Carbohydrates (polysaccharides) found in grass, nuts, rice, root vegetables and legumes
-Cellulose
—-Complex Carbohydrates (polysaccharides) found in most vegetables
Proteins
—-Meat, dairy products, soy beans, green leafy plants, eggs
Lipids
-Neutral Fats
—- Saturated: meat, milk, cheese, cream, butter, coconuts
—-Unsaturated: vegetable oi, olive, safflower
—-phospholipids: plasma membranes in plant cells and animal cells
—-Steroids: eggs, butter and cream, animal fat, some chemical insecticides in the environment
—–Cholesterol
The 6 Nutrients
(In Descending Order of Amounts Needed)
Water
Carb
Protein
Fat
Minerals
Vitamins
Caloric Values of Energy Nutrients
Carb 4 cal/g
Fat 9cal/g
Protein 4 cal/g
Carbohydrates
Sugars
* Monosaccharides and disaccharides
* Fruits, sugar cane, honey, milk, sugar beets
Starches
*Polysaccharides
* Grains, root vegetables, and legumes
Cellulose – fiber
*Polysaccharides
* Most vegetables
Glucose
Monosaccharide
*Simplest, smallest dietary carbohydrate
Used to make ATP through glycolysis
Excess converted to glycogen and stored in liver -or- converted to fat and stored in adipose tissue
Lipids
Insoluble in water
*“Fat floats!”
Soluble in other lipids and organic solvents
4 major categories
* Neutral fats (triglycerides)
*Phospholipids
*Steroids
* Other lipoid substances
Composition
* Carbon, hydrogen, oxygen
Neutral Fats
= Fats or Oils
Composed of fatty acids and glycerol
Fatty acids
* Classified by number of carbon atoms in backbone of molecule
* Long-chain, medium-chain, or short-chain
Glycerol
* modified simple sugar
Saturated Fatty Acids
Single bonds between carbon atoms
Can accommodate the greatest number of H+ atoms
Tend to have long chains
Found in meat and dairy foods
Glycerol backbone and 3 straight fatty acid chains
“bad” fats
Unsaturated Fatty Acids
One or more double bonds between carbon atoms
Can accommodate fewer H+ atoms
Tend to be liquid at room temperature (oils)
Monounsaturated fats
* Olive and peanut oils
Polyunsaturated fats
* Corn, soybean, and safflower oils
Glycerol backbone and 3 kinked fatty acid chains
Healthier- mono the best
Fatty Acids
Liver can convert one fatty acid into another
Essential fatty acids (EFA’s) cannot be synthesized and must be in the animal diet
* Linoleic acid
* Linolenic acid
*Arachidonic acid
Neutral Fats
Contain over twice as much potential energy by weight as proteins or carbohydrates
Make food taste good, stave off hunger
Help body absorb fat-soluble vitamins: A,D, E, K
Important insulator, when stored
Protect and cushion vital organs
Rebuilt by liver
* Forming different kinds of triglycerides
Major energy source for hepatocytes and skeletal muscle cells
Phospholipids
Derived primarily from cell membranes of plant and animal cells
Modified triglycerides
* Glycerol core and two fatty acid chains = diglyceride
*Also a phosphorus group attached glycerol = “polar head”
Steroids
Composed of 4 flat, interlocking rings of hydrocarbons
Examples
* Cholesterol, bile salts, sex hormones, and hormones released from the cortex of the adrenal gland
Cholesterol is essential precursor of all steroids
* Found in plasma membrane
* Nutritionally derived from egg yolks, milk, cheese
* Can be manufactured by liver
* Essential nutrient?
Different types formed by attaching unique functional groups
Other Lipoid Substances
Fat-soluble vitamins
Eicosanoids
* Regulatory molecules derived from arachidonic acid
*Prostaglandins, leukotrienes, thromboxanes
Lipoproteins
Proteins
Dominant structural material of the animal body
Regulate body functions
*Enzymes and hormones
Transport oxygen
* Hemoglobin
Aid in body movement
* Contractile proteins in muscle cells
Can be used for energy in the animal body
Commonly composed of 100–10,000 amino acids
Protein Structure
Composed of amino acids linked together
*A basic amine group (-NH2)
*An organic acid group (-COOH)
*A variable R group
22 different types of amino acids
Type and order of amino acids determine structure and function of the protein
10 essential and 12 nonessential amino acids in most species
Peptide bonds
Peptide bond
*Bond between the acid group of one amino acid and the basic group on the next
Dipeptide – linking of 2 amino acids
Tripeptide – linking of 3 amino acids
Polypeptide – linking of >10 amino acids
Protein – polypeptide with 50 or more amino acids
Essential Amino Acids
Must be present in diet
Animal cannot make them at all, or cannot make them fast enough to meet body’s need for tissue maintenance and growth
Arginine
Glycine
Histidine
Isoleucine
Leucine
Lysine
Methionine
Phenylalanine
Taurine
Threonine
Tryptophan
Valine
Glycogen
A polysaccharide stored in the animal’s body
-stored in liver or skeletal muscle
-not a lot stored
(similar to how starch acts in plants)
All or None Rule for Amino Acids
For body to make a new protein –
*All of the needed amino acids
*Essential and nonessential
* Must be present in the cell
*In sufficient quantity
*And all at the same time
If one amino acid is missing, the protein cannot be manufactured
Complete Proteins
- Food products that contain all the essential amino acids for a species
- Meat, eggs, dairy
Complements (nutrients)
- Food products, when ingested together, contain all the essential amino acids for a species
- Legumes, grains, and cereals
Nitrogen Balance
Rate of protein synthesis should equal the rate of protein loss
Nitrogen balance
* Rate of protein synthesis equals rate of protein breakdown and loss
Positive nitrogen balance
*Body incorporates more protein into tissue than it is using to make energy (ATP)
* Healing, animal growth
Negative nitrogen balance
*Protein breakdown exceeds amount of protein being incorporated into tissue
*Stress, starvation, poor dietary protein
Ideal Protein Content in Foods
Includes all essential amino acids needed by a species to meet its metabolic requirements
Biologic value
*Percentage of absorbable protein available for body functions
* Not same as protein content
Ruminant Digestion of Protein
Facilitated by microbes
Microbial-made protein has consistent quality regardless of the source
*Protein in lower-quality feed is improved by microbial metabolism
*Protein in higher-quality feed may be lowered
by microbial metabolism
Rumen has ability to convert nonprotein sources of nitrogen into protein
Vitamins
Essential for life
* Do not produce energy when metabolized
*Are not broken down into building-block units
Function as co-enzymes or parts of co-enzymes
* Molecular structure is “key” to activate an enzyme
Most vitamins are not made in animal body
* Must be consumed in diet
*Essential Vitamins
*Exceptions: Vitamins D, K, biotin, A
Water-Soluble Vitamins
Absorbed through GI wall when water is absorbed
Very few stored in body
* Hypervitaminosis conditions rare
Excesses excreted in urine
Group includes:
*Vitamin C
*B-complex vitamins
Fat-Soluble Vitamins
Bind to ingested lipids before they are absorbed with ingesta
Stored in body (except for Vitamin K)
*Possible toxicity due to hypervitaminosis
Group includes:
*Vitamins A, D, E, and K
Free Radicals
Potentially harmful to body
Generated when carbohydrates, proteins, and lipids are oxidized as part of normal metabolism
* Glucose + Oxygen Water + Carbon Dioxide + ATP
Disarmed by antioxidants
*Vitamins A, Vitamin C, Vitamin E: ACE
Minerals
Inorganic substances essential for life
Elements on the Periodic Table
Non-energy producing
Work with other nutrients to ensure normal body functions
3 classes depending on how much is required by body
* Macrominerals
* Microminerals
* Trace elements
Water
The MOST Essential Nutrient of All
Water 60%
*Intracellular (ICF) 40%
*Extracellular (ECF) 20%
— Vascular 15%
—Interstitial 5%
Other elements 40%
(solutes)
Normal Hydration
Consuming the same amount of water that is lost
Animals take in water
*Eating moist foods and drinking fluids
* Metabolic water
Animals lose water
*Insensible water loss
– Diffused passively away from the skin
–Sweating, vocalizing, urinating, defeating
—-Vomiting, diarrhea, excessive sweating, hemorrhaging, and elevated body temperatures
Body Fluids
Intracellular fluid – cytosol
Extracellular fluid
*Intravascular fluid – plasma
*Interstitial fluid
Metabolism
Definition – The sum total of ALL chemical reactions going on in all of the cells of the animal’s body
* Catabolism–the breakdown of complex molecules in living organisms to form simpler ones; destructive metabolism.
*Anabolism –the synthesis of complex molecules in living organisms from simpler ones together with the storage of energy; constructive metabolism.
Catabolism
Breaking down nutrients into smaller molecules to produce energy (e.g. – digestion)
Energy is stored in bonds of ATP molecule and transported where it is needed
Anabolism
Stored energy is used to assemble new molecules from small components produced from catabolism
Anabolic steroids – for starvation/emaciated cases
Stages of Catabolism
Stage 1: Hydrolysis
* Digestion in the lumen of the GI tract
* Carbohydrates, lipids (fats), proteins
*Energy produced
Stage 2: The cytosol
*Anaerobic cellular respiration in the cell’s cytosol
—Acetyl CoA is transported through cytoplasm to the mitochondria
Stage 3: The mitochondria
*Aerobic cellular respiration in mitochondria
— involves the attachment of an inorganic PO4 to a molecule of ADP to form ATP, used by the cell to “do its thing
Anaerobic Cellular Respiration
**This part is most important to know:
Glycolysis -Not the primary source of ATP
Glucose → Alcohol + Carbon dioxide + Energy
**
▪ “Sugar splitting” occurs in all animals and includes 10 biochemical steps,
▪ 2 molecules of pyruvic acid, 4 molecules of ATP, and 2 molecules of NADH are produced
▪ Net energy yield from glycolysis = 2 ATP and 2 NADH
Hydrolysis
(Catabolism)
* Carbohydrates broken down to monosaccharides
* Fats broken down to fatty acids and glycerol
*Proteins broken down to amino acids
* Nucleic acids broken down to nucleotides
Anabolic Metabolism
A biosynthetic process
Growing cells need additional proteins
* For the expanded cell membranes
* To perform many other vital functions
Replacement molecules must be manufactured continuously
* Metabolic turnover- largest demand for proteins and enzymes
Dehydration Synthesis
Important part of anabolism
*Effect is opposite of hydrolysis
Monosaccharides are assembled to form chains of polysaccharides
* 1 monosaccharide + 1 monosaccharide = 1 disaccharide + water
Fat molecules are formed from the connection of glycerol and fatty acids
Proteins are created from chains of amino acids
Control of Metabolic Reactions
Metabolism is a multi-enzyme sequence of events
Reactions are highly specific
* Cell relies on enzymes to initiate and control metabolism
Enzymes are specialized proteins
*Each enzyme reacts with one particular molecule (substrate) to produce a new molecule (product)
* Enzyme action as catalyst
—Speeds up chemical reactions by lowering the activation energy
*Product of one step is substrate of the next
May need assistance of a nonprotein cofactor in order to complete a reaction
* Completes the shape of a binding site
*Examples: iron, zinc, copper, magnesium ions
Enzyme Activity
Depends on molecular shape of the enzyme
Active site = region of enzyme that binds to the substrate
Enzymes not altered by the reactions
Co-enzymes
Nonprotein enzymes that may also act as cofactors
* Often vitamins, or derived from vitamins
May be bound temporarily or permanently to the enzyme
Energy for Metabolic Reactions
Energy is supplied to cells by breakdown of nutrients
Storage forms of energy: ATP, NADH, FADH2
Energy is released when molecular bonds are broken
Carbohydrate Metabolism
Occurs in cytoplasm
* Catabolic and anabolic processes
Sources of carbohydrates
* Diet
*Breakdown of glycogen or glycerol
*Propionate stored in the liver (ruminants)
Aerobic Respiration where and what stages
Occurs in the mitochondria
2 stages:
* Krebs cycle ( citric acid cycle)
* electron transport chain
–Final stage of aerobic cellular respiration
—Produces the majority of ATP for the cell
Types of proteins structures
Unique structures for unique functions
*Structural proteins
* Regulatory proteins
* Contractile proteins
* Transport proteins
* Membrane proteins
* Osmoregulators
*And – used to make energy (ATP)
Glucose Metabolism
Primary carbohydrate found in blood
Absorbed by all cells
* Facilitated diffusion
*Active transport
Glycolysis produces energy (ATP)
* Glucose broken down to form pyruvate (pyruvic acid)
* Cellular respiration follows
*Anaerobic or aerobic respiration
Triglycerides
Contain more carbon-hydrogen bonds than other nutrient molecules
* Contain 2 times the chemical energy of carbohydrates
*Store 6 times the chemical energy of glycogen
Can be removed from blood by liver and structurally altered
* Lipolysis
Protein Metabolism
Amino acid catabolism occurs in most tissues
Amino acid molecules may undergo transamination or deamination
*Intestinal mucosa, kidney, brain, liver, skeletal muscle
NADH
Nicotinamide adenine dinucleotide
Common coenzyme that acts as a cofactor
FAD
Flavin adenine dinucleotide
Common coenzyme that acts as a cofactor
Cofactor
Elements, such as coenzymes, that act concurrently with another element to carry out a chemical reaction
Important for digestion
Trace elements
Chromium
Cobalt
Fluorine
Molybdenum
Nickel
Silicon
Sulfur
Vanadium
Macrominerals
Calcium
Chlorine
Magnesium
Phosphorus
Potassium
Sodium
Microminerals
Copper
Iodine
Iron
Manganese
Selenium
Zinc
Cellular Metabolism
Encompasses all biochemical events *building molecules *breaking down nutrients
*manufacturing and packaging
*excreting
Making protein is an important example
Krebes cycle
▪ Pyruvic acid enters the mitochondria
▪ Before it enters the Krebs Cycle, it is transformed from a three-carbon molecule of pyruvic acid into a two-carbon acetyl group;
this binds to a compound known as coenzyme A to form acetyl CoA,
***link between glycolysis and the Krebs cycle.
**1 molecule of CO2 and 1 NADH are generated for every
molecule of pyruvic acid
▪ Acetyl CoA enters the Krebs cycle and reacts with oxaloacetic acid to form citric acid;
▪ As citric acid is produced, coenzyme A is released and is used repeatedly to make acetyl CoA.
▪ After seven additional steps, citric acid is converted back to oxaloacetic acid, and the entire process is repeated.
▪ Each turn of the Krebs cycle generates energy in the form of 1 ATP, 1 FADH2, and 3 NADH molecules
▪ For every molecule of glucose, the Krebs cycle can run twice and produce 2 ATP, 2 FADH2, and 6 NADH
▪ CO2, which is a by-product of respiration, diffuses out of the cell and into the bloodstream
Electron transport system
▪ Occurs in the inner wall of the mitochondrion and produces the majority of ATP for the cell
▪ NAD and FAD molecules released from the conversion of pyruvic to acetyl CoA, glycolysis, and the Krebs cycle bind to hydrogen atoms to form NADH and FADH2.
The electrons in NADH and FADH2 hold most of the energy once held by the original glucose molecule.
**they are carried down a chain of electron carrier molecules, collectively known as the cytochromes
▪ Each cytochrome molecule contains a central core of iron that accepts electrons and then releases them at a lower energy level.
**At each step, large amounts of free energy are released and used to pump protons from the mitochondrial matrix
**This establishes a difference in electrical charge, because more positive hydrogen ions are pumped to the
outside than remain on the inside of the inner mitochondrial membrane.
** Thus, the outside has a positive charge relative to the matrix side of the membrane resulting in the formation of potential energy
▪ The energy released during the downhill pathway is captured in the formation of ATP from ADP.
**At the end of the electron transport chain, oxygen accepts the low-energy electrons, joins with hydrogen ions, and forms water. Thus, oxygen is the final acceptor of the electrons
Enzyme structure
Amino Acids in the body
Amino acids cannot be stored
*If not used immediately to make proteins
* Oxidized by cell to make energy
* Converted to carbohydrates or fats
Phase 1 Glycolysis
Phosphorylation -> energy
*(1 ATP) is invested in the process of adding a phosphate molecule to glucose to form glucose-6-phosphate (G6P). —– —-costs energy,
*G6P is rearranged to form fructose-6- phosphate.
-From here phosphorylation occurs again using another ATP to form fructose-1,6-diphosphate
Phase 2 Glycolysis
Cleavage of sugar
* fructose-1,6-diphosphate is cleaved.
*A pair of three-carbon molecules is formed
– they can be one of two reversible isomers:
—- (less important) dihydroxyacetone phosphate and glyceraldehyde phosphate
–The molecules change back and forth between these two forms
Phase 3 Glycolysis
Formation of ATP via oxidation of sugar
▪ Net energy yield from glycolysis = 2 ATP and 2 NADH
