Lecture 19: Metabolism & Nutrition Flashcards
describe the fate of proteins
-Digested proteins are broken down into amino acids which are: Oxidized to produce ATP, or Used to synthesize new proteins
-Many proteins function as enzymes, in transportation, as antibodies, clotting blood, hormones, or part of muscle fibers
what is protein anabolism
creates new proteins by bonding together amino acids on ribosomes
what is protein catabolism
-For proteins to be used as energy: They must be converted into substances that can enter citric acid
cycle
-This conversion involves:
* Transamination
* Deamination
* Urea cycle
-Removal of amino group requires a coenzyme derivative of vitamin B6
-Cells oxidize amino acids to generate ATP via the Krebs cycle
describe transamination (protein catabolism)
-attaches amino group of amino acid to keto acid
-converts keto acid into amino acid: which then leaves mitochondrion and enters cytosol & is available for protein synthesis
-in transamination the amino group (-NH2) of one amino acid is transferred to a keto acid
describe deamination (protein catabolism)
-Removal of amino group and hydrogen atom: Generating a toxic ammonium ions in the liver
-Liver cells have enzymes that remove toxic ammonium ions by synthesizing urea: Through the urea cycle= Fairly harmless water-soluble compound excreted in urine
-Prepares amino acid for breakdown in citric acid cycle
-the amino group is removed and an ammonium ion is released
what happens in the urea cycle
it takes two metabolic waste products, ammonium ions and carbon dioxide and produced urea, a relatively harmless, soluble compound that is excreted in the urine
what are the key molecules at metabolic crossroads
Of the thousands of different chemicals in cells, glucose 6-phosphate, pyruvic acid, and acetyl coenzyme A are extremely important in metabolism
what pathways can it go from glucose 6-phosphate
- to glycogen (liver and muscle cells)
- to glucose (in blood)
- ribose 5-phospahte and NADPH -> DNA & RNA
- glycolysis (cytosol) and into pyruvic acid
what pathways can pyruvic acid go to
- anaerobic reactions with lactic acid (equillibrium)
- alanine (amino acid) (equillibrium) this is convergence of CHO and protein metabolism
- into the krebs cycle
- if low ATP & high O2-> through aerobic reactions in mitochondria into acetyl coenzyme A
what pathways can acetyl coenzyme A go to
- into the krebs cycle
- cholesterol
equilibrium with fatty acids with equillibrium with triglycerides & phospholipids
summarize glucose catabolism
complete oxidation of glucose (cellular respiration) is cheif source of ATP in cells; consists of glycolysis, krebs cycle, and electron transport chain. complete oxidationof 1 molecule of glucose yields maximum of 30 or 32 molecules of ATP
summarize glycolysis
conversion of glucose into pyruvic acid results in production of some ATP. reactions do not require oxygen
summarize krebs cycle
cycle includes series of oxidation-reduction reactions in which coenzymes (NAD+ & FAD) pick up hydrogen ions and hydride ions from oxidized organic acids; some ATP produced. CO2 and H2O are by-products. reactiosn are aerobic
summarize electron transport chain
third set of reactions in glucose catabolism: another series of oxidation-reduction reactions, in which electrons are passed from one carrier to the next; most ATP produced. reactions require oxygen (aerboic cellular respiration)
summarize glucose anabolism
some glucose is converted into glycogen (glycogenesis) for storage if not needed immediately for ATP production. glycogen can be reconverted to glucose (glycogenolysis). conversion of amino acids, glycerol, and lactic acid into glucose is called gluconeogenesis
summarize triglyceride catabolism
triglycerides are broken down into glycerol and fatty acids. glycerol may be converted into glucos (gluconeogenesis) or catabolized via glycolysis. fatty acids are catabolized via beta oxidation into acetyl coenzyme A that can enter krebs cycle for ATP production or be converted into ketone bodies (ketogenesis)
summarize triglyceride anabolism
synthesis of triglycerides from glucose and fatty acids is called lipogenesis. triglycerides are stored in adipose tissue
summarize protein catabolism
amino acids are oxidized via krebs cycle after deamination. ammonia resulting from deamination is converted into urea in the liver, passed into blood, and excreted in urine. amino acids may be converted into glucose (gluconeogenesis), fatty acids, or ketone bodies
summarize protein anabolism
protein synthesis is directed by DNA and utilizes cells’ RNA and ribosomes
what are metabolic adaptations
-Modification of body’s biochemical process to efficiently convert food into energy
-Metabolic regulation depends on: Chemicals in cells & Signals from the nervous and endocrine systems
-Some aspects of metabolism depend on time elapsed since the last meal
describe the absorptive state
-period following a mal when nutrient absorption is under way; lasts ~4 hours, three meals= 12 hour/day
-nutrients get to bloodstream, glucose is available for ATP formation
what are the hormonal regulation processes of metabolism in the absorptive state
-facilitated diffusion of glucose into cells, locations in most cells, stimulating hormone = insulin
-active transport of amino acids into cells, locations in most cells, stimulating hormone= insulin
-glycogenesis (glycogen synthesis), location in hepatocytes and muscle fibers, stimulating hormone= insulin
-protein synthesis, location in all body cells, stimulating hormones= insulin/ thyroid hormones/ and insulinlike growth factors
-lipogenesis (triglyceride synthesis), location in adipose cells and hepatocytes, stimulating hormone= insulin
what are the metabolic pathways in the absorptive state
describe the post absorptive state
-Complete absorption of nutrients from GI tract (SI)
-Energy needs are met by fuels already in the body – internal energy reserves: Remaining 12 h
-Normal blood glucose levels are maintained due to breakdown of nutrient stores– glycogen, fat, and gluconeogenesis
what are the hormonal regulation processes of metabolism in the postabsorptive state
-glycogenolysis (glycogen breakdown), locations= hepatocytes & skeletal muscle fibers, stimulating hormones= glucagon & epinepherine
-lipolysis (triglyceride breakdown), location= adipocytes, stimulating hormones= epinehperine/ norepinepherine/ cortisol/ insulinlike growth factors/ thyroid hormones
-protein breakdown, locations= most body cells but especially skeletal muscle fibers, stimulating hormone= cortisol
-gluconeogenesis (synthesis of glucose from noncarbohydrates), locations= hepatocytes & kidney cortex cells, stimulating hormones= glucagon & cortisol
what are the metabolic pathways in the postabsorptive state
how do heat and energy balance (and calories)
-heat production: regulated by rates of metabolic reactions in the body
-energy balance: food intake corresponds to energy expenditure
-calprie (cal): unit of released heat energy. 1kcal (cal)= 1000 cal
what is the determination of kcal of food compoents
= grams x energy content
what is the energy content of carbohydrate
4 kcal/g
what is the energy content of protein
4 kcal/g
what is the energy content of fat
9 kcal/g
what is the energy content of alcohol
7 kcal/g
how does higher calories compare to energy
-higher calorie = greater energy-> more burden on body’s systems
-more activity required to breakdown
-inactivity overweight-> cardiovascular and metabolic conditions
what is metabolic rate
-Rate of heat loss must equal rate of heat production for homeostasis of body temperature
-Metabolic Rate: overall rate at which metabolic reactions use energy
-MR is measured with the body in a quiet, resting, and fasting state: This is basal metabolic rate (BMR)
what factors affect metabolic rate (heat production)
exercise, hormones, nervous system, body temperature, ingestion of food, age, gender, climate, sleeping, malnutrition
what is total metabolic rate (TMR)
-total energy expended/unit time
-energy intake is directly dependent on the amount of food consumed
-total energy expenditure is based on: basal metabolic rate (60%), physical activity (30-35%), and food-induced thermogenesis (5-10%)
what is a balanced diet
contains all ingredients needed for imbalance
what is malnutrition
unhealthy state resulting from nutrient imbalance
what are nutrients
chemicals in food that cells use for growth, maintenance and repair
what are the six types of nutrients
water, carbohydrates, lipids, proteins, minerals, and vitamins
what are the quidelines for healthy eating
recommended calorie distribution is:
-CHOs: 50-60% (<15% simple sugars)
-fats: <30% (</=10% saturated)
-protein: 12-15%
the canadian food guide shows how people should proportion thier food intake
what are minerals
-Inorganic ions released through dissociation of electrolytes
-Important for three reasons:
* Ions such as Na and Cl- determine osmotic concentrations of body fluids
* Ions play major roles in physiological processes
* Ions are essential cofactors in many enzymatic reactions
-Bulk minerals: Na, K, Cl-, Ca, P, and Mg
-Trace minerals: Fe, Zn, Cu, Mn, Co, Se, and Cr
-Body contains reserves of several important minerals
summarize calcium and its importance
-most abunbant mineral in body. appears in combination with phosphates. about 99% sotred in bone and teeth. blood Ca2+ level controlled by parathyroid hormones (PTH). calcitriol promotes absorption of dietary calcium. excess excreted in feces and urine. sources: milk, egg yolk, shellfish, leafy green vegetables
-Importance: formation of bones & teeth, normal muscle and nerve activity, endocytosis and exocytosis, cellular motility, chromosome movement during cell division, glycogen metabolism, release of neurotransmitters and hormones
summarize phosphorus and its importance
about 80% found in bones and teeth as phosphate salts. blood phosphate level controlled by parathyroid hormone (PTH). excess excreted in urine; small amount is eliminated in feces. sources: dairy products, meat, fish, poultry, nuts
-Importance: formation of bones and teeth. phosphates (H2PO4-, HPO42-, & PO43-) constitute a major buffer system of blood. role in muscle contraction and nerve activity. componenet of many enzymes. involved in energy trnasfer (ATP). componenet of DNA & RNA
summarize potassium and its importance
major cation (K+) in intracellular fluid. excess excreted in urine. present in most foods (meats, fish, poultry, fruits, nuts)
-Importance: needed for generation and conduction of action potentials in neurons and muscle fibers
summarize sulfur and its importance
componenet of many proteins (such as insulin and chondroitin sulfate), electron carriers in electron transport chain, and some vitamines (thiamine and biotin). excreted in urine. sources: beef, liver, lamb, fish, poultry, eggs, cheese, beans
-Importance: as components of hormones and vitamins, regulates various body activities. needed for ATP production by electrontransport chain
summarize sodium and its importance
most abundant cation (Na+) in extracellular fluid; some found in bones. excreted in urine and perspiration. normal intake of NaCl supplies more than requires amounts
-Importance: strongly affects distribution of water through osmosis. part of bicarbonate buffer system. functions in nevre and muscle action potential conduction
summarize chloride and its importance
major anion (Cl-) in extracellular fluid. excess excreted in urine. sources: table salt, soy sauce, processed foods
-Importance: role in acid-base balance of blood, water balance, and formation of HCl in stomach
summarize magnesium and its importance
important cation in intracellular fluid. excreted in urine and feces. widespread in various foods
-Importance: required for normal functioning of muscle and nervours tissue. participates in bone formation. constituent of many coenzymes
summarize iron and its importance
~66% found in hemoglobin of blood. normal losses of iron accur by shedding of hair, epithelial cells, and mucosal cells, and in sweat, urine, feces, bile, and blood lost during menstruation. sources: meat, liver, shellfish, egg yolk, beans, etc
-Importance: as componenet of hemoglobin, reversibly binds O2. component of cytochromes involved in electron transport chain
summarize iodide and its importance
essential component of thyroid hormones. excreted in urine. sources: seafood, iodized salt, vegetables grown in iodine-rich soils
-Importance: required by thyroid gland to synthesize thyroid hormones which regulate metabolic rate
summarize maganese and its importance
some stored in liver and spleen. most excreted in feces. sources: spinach, romaine lettuce, pineapple
-Importance: activates several enzymes. needed for hemoglobin synthesis, urea formation, growth, reproduction, lactation, bone formation, and possibly production and release of insulin and inhibition of cell damage
summarize copper and its importance
some stored in liver and spleen. most excreted in feces
-importance: required with iron for synthesis of hemoglobin. component of coenzymes in electron trnasport chain and enzyme necessary for melanin formation
summarize cobalt and its importance
constituent of vitamin B12
-imporrtance: as part of vitamin B12, required for erythropoiesis
summarize zinc and its importance
important component of certain enzymes. widespread in many foods, especially meats
-Importance: as component of carbonic anahydrase, important in carbon dioxide metablism. necessary for normal growth and wound healing, normal taste sensations and appetite, and normal sperm counts in males. as component of peptidases, involved in protein digestion
summarize flouride and its importance
component of bones, teeth, other tissues. sources: seafood, tea, gelatin
-Importance: appears to improve tooth structure and inhibit tooth decay
summarize selenium and its importance
important comonnent of certain enzymes. sources: seafood, meat, chicken, tomatoes, egg yolk, milk, mushrooms, garlic, cereal grains gorwn in selenium rich soil
-Importance: needed for synthesis of thyroid hormones, sperm motility, and proper functioning of immune systems, also functions as antioxidant. prevents chromosome breakage and may play role in preventing certain birth defects, miscarriage, prostate cancer, and coronary artery disease
summarize chromium and its importance
found in high concentrations in brewer’s yeast. also found in wine and some brands of beer
-Importance: needed for normal activity of insulin in carbohydrate and lipid metabolism
describe vitamins
Essential organic nutrients that function as coenzymes in vital enzymatic reactions
Two Groups Based on Chemical Structure and Characteristics:
Fat-soluble Vitamins: A, D, E, K
-Absorbed primarily from digestive tract along with lipids of micelles
Water-soluble Vitamins: C and B complexes
-Components of coenzymes
-Rapidly exchanged between fluid in GI tract and circulating blood
-Excesses are readily excreted in urine
-Thus, hypervitaminosis is relatively uncommon in water-soluble vitamins
review slides 27-29 for vitamins
