Nutrition and metabolism Flashcards
Hormones that directly activate genes are classified as
lipid soluble
Oxytocin is produced here…
Hypothalamus
What is the effect of PTH (parathyroid hormone)?
- > increase osteoclast activity
- > increase Ca 2+ reabsorption in the kidney
- > increase Ca2+ absorption in the intestine
Which hormone controls the rate of body metabolism and cellular oxidation?
T3/T4 (thyroid hormones)
Nutrient
a substance in food that promotes normal growth, maintenance and repair
Major nutrients
- carbs
- lipids
- proteins
45 essential nutrients- body cannot make
comes from the food you eat
Western diet
high in:
- meat
- sugar
- vegetable oil
- white flour
*60% of diet is fast food and processed food
Carbohydrates
-> main source of energy
Dietary sources:
-STARCH (complex carbs) in grains and vegetables- polysaccharides
-SUGARS in fruits, sugarcane, sugar beets, honey and milk- mono and disaccharides
- FIBER (cellulose):
- Insoluble: cellulose in vegetables; provides roughage (maintains health of colon. feeds useful bacteria in colon)
*soluble fiber: pectin (found in cell wall of plants) in apples and citrus fruits; reduces blood cholesterol levels.
Carbohydrates
Uses:
- > Glucose is the fuel used by cells to make ATP
- Neurons (nervous system) and RBC-> glucose
- if run low can depress brain function (diabetic coma)
- excess glucose is converted to glycogen (liver/skeletal muscles) or fat and stored
Lipids
Dietary sources:
- Triglycerides (most abundant lipid):
* Saturated fats in meat, dairy foods, and tropical oils
* unsaturated fats in seeds, nuts, olive oil, and most vegetable oils - Cholesterol in egg yolk, meats, organ meats, shellfish, and milk products
- > liver produces about 85% of blood cholesterol
Saturated Fats
usually solid at room temp (butter), only single bonds between carbon atoms
Unsaturated fats
at least one double bond, usually liquids at room temp
Lipids
essential fatty acids:
- Omega-3 and Omega-6; found in most vegetable oils
- must be ingested, liver cannot synthesize
Uses of lipids
- Absorption: fat-soluble vitamins
- Fuel: of hepatocytes and skeletal muscle (triglycerides)
- Cell membranes and myelin sheaths
- Functions of fatty deposits (adipose tissue)
* protection of body organs, insulation, concentrated source of energy - regulatory function of prostaglandins:
* control of BP, smooth MM contractions, inflammation - Function of cholesterol (not used for energy)
* stabilizes plasma membranes
* precursor of bile salts and steroid hormones
proteins
Uses:
1. structural materials: keratin, collagen, elastin, muscle proteins
- most Functional Molecules: enzymes, some hormones
- Nitrogen balance: rate of protein synthesis= rate of breakdown
- Hormonal controls:
* anabolic hormones (GH, sex hormones) accelerate protein synthesis
Proteins
dietary sources:
-> animal products: eggs, milk, fish, and most meats contain complete proteins
- > legumes (beans/peas) and cereals together contain all essential amino acids
- body can only produce 12/20 amino acids, the other 8 are the essential amino acids, need to be present in diet
vitamins
- organic compounds
- crucial in helping the body use nutrients
- most function as coenzymes
- vitamins D (skin), some B, and K are synthesized in the body (intestinal bacteria)
*if carbs, fats, and proteins are the fuel of a car, vitamins are the ignition
vitamins
2 types, based on solubility:
- water-soluble vitamins:
* B complex and C are absorbed with water
* not stored in the body, need to be ingested daily - Fat-soluble vitamins
* A,D,E and K are absorbed with lipid digestion products
* stored in the body, except for vitamin K
Minerals
7 inorganic nutrients required in moderate amounts
-calcium, phosphorus, pottassium, sulfur, sodium, chloride, and magnesium
- others required in trace amounts
- work with nutrients to ensure proper body functioning
Minerals 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 the blood
- large amounts of Na present in processed food or sprinkled on food may contribute to fluid retention and high BP
Proteins are used primarily to build all of the following except
cell membrane
Metabolsim
-> biochemical reactions inside cells involving nutrients
2 types of reactions:
-Anabolism- synthesis of large molecules from small ones
- catabolism- hydrolysis of complex structures to simpler ones
- cellular respiration: catabolism of food fuels and capture of energy to form ATP in cells
3 stages of metabolism
Processing of nutrients:
1. digestion, absorption and transport to tissues
- Cellular processing (in cytoplasm)
* Anabolism (synthesis) of lipids, proteins, and glycogen
* catabolism (glycolysis) into intermediates - Oxidative (mitochondrial) breakdown of intermediates into CO2, water, and ATP
Oxidation-reduction (redox) reactions
- transfer of electrons from one molecule to another
- Oxidation: gain of oxygen or loss of hydrogen ion (loss of electron)
- oxidation-reduction (redox) reactions
- oxidized substances lose electrons and energy
- reduced substances gain electrons and energy
- coenzymes act as hydrogen (or electron) acceptors
- Nicotinamide adenine dinucleotide (NAD+)
- Flavin adenine dinucleotide (FAD)
ATP synthesis
2 mechanisms:
- substrate-level phosphorylation (fast, low output)
* 1. glycolysis
* 2. Kreb (citric acid) cycle - oxidative phosphorylation (slow, high output)
- Carried out by electron transport proteins
- Nutrient energy is used to create H+ gradient across mitochondrial membrane
- H+ flows through ATP synthase
- Energy is captured and attaches phosphate groups to ADP
Carbohydrate metabolism
Oxidation of glucose:
C6H12O6 + 6O2 -> 6H2O + 6CO2 + 32 ATP + heat
- glucose is catabolized in 3 pathways
1. glycolysis
2. krebs cycle (citric acid cycle)
3. electron transport chain and oxidative phosphorylation
glycolysis
- > 10-step pathway- high speed reaction
- > anaerobic, only produces 5% of total ATP
- > occurs in cytosol
- > glucose-> 2 pyruvic acid molecules (6C to two 3C)
glycolysis
Final products of glycolysis:
- > 2 pyruvic acid
- converted to lactic acid if O2 not readily available
- enter aerobic pathways if O2 is readily availble
- > 2 NADH to electron transport
- > net gain of 2 ATP
IN: GLUCOSE
OUT: 2 ATP, 2 NADH, 2 pyruvic acid
Lactic acid
- If not enough oxygen, NADH returns its H to pyruvic acid which forms lactic acid.
- Will allow working muscles to continue at high rates for 1-3 minutes
- Lactic acid not responsible for post exercise soreness
- Is responsible for muscle burn
Krebs (citric acid) cycle
- occurs in mitochondrial matrix
- fueled by pyruvic acid and fatty acids
- pyruvic acid is broken down into CO2 in a series of energy extracting reactions
- breakdown products of fats and proteins can also enter the cycle
- primary role is to generate electrons (H)
kreb cycle products
- 2 ATP
- 4 CO2
- 6 NADH
- 2 FADH
Electron transport chain and oxidative phosphorylation
- The part of metabolism that directly uses oxygen
- Substrates NADH + H+ and FADH2 deliver hydrogen atoms
- Hydrogen atoms are split into H+ and electrons
- Electrons are shuttled along the inner mitochondrial membrane, losing energy at each step
- Released energy is used to pump H+ into the intermembrane space
Which of the following processes is likely to occur in the skeletal muscle cells during sprinting?
glycolysis
bc under 10-30 sec
glycogenesis
- > glycogen formation when glucose supplies exceed need for ATP synthesis
- > mostly in liver and skeletal muscle
glycogenolysis
- > glycogen breakdown in response to low blood glucose
- unable to store ATP, so glucose needs to be stored for later use
athletes and carbs
-Complex carbohydrates -> more glycogen storage in muscle; more effective than high-protein meal for intense muscle activity
Carbo loading
- Carbohydrate-rich diet for 3-4 days; decreased activity -> muscles store more glycogen
- > improved performance and endurance
gluconeogenesis
- glucose formation from noncarbohydrate (glycerol and amino acid) molecules
- mainly in the liver
- protects against damaging effects of hypoglycemia (especially important for nervous system)
lipid metabolism
-> fat catabolism yields 9 kcal per gram (vs 4 kcal per gram of carb of protein)
- > most concentrated source of energy:
- blood glucose- energy for a few minutes
- glycogen stores- energy for a day
- lipid stores- 30 to 40 days
-> lipolysis “fat splitting” into fatty acids and glycerol
lipid metabolism
- > only triglycerides are routinely oxidized for energy
- > the 2 building blocks are oxidized separately
- glycerol pathway- glycerol enters into glycolysis
- fatty acid pathway- fatty acids enter the kreb (citric acid) cycle
lipogenesis
- > Triglyceride synthesis occurs when cellular ATP and glucose levels are high
- > Glucose is easily converted into fat
- > Stored in subcutaneous or adipose tissues.
lipolysis
- > The reverse of lipogenesis
- stored fat-> glycerol and fatty acids for fuel (preferred by liver, cardiac muscle, resting skeletal muscle)
- > “fats burn in a carbohydrate flame”
- without it, acetyl CoA is converted by ketogenesis in the liver into ketone bodies (ketones)
homeostatic imbalance
Accumulation of ketones in blood-> ketosis
- Ketones acidic-> metabolic acidosis
- low blood pH, can lead to coma/death
- breathing rapid to release CO2 to raise pH
- common in starvation, unwise dieting, diabetes mellitus
- ketone bodies excreted in urine
Glycerol is metabolized at what stage of cellular respiration?
glycolysis
protein metabolism
- proteins deteriorate, so continually broken down and replaced
- amino acids recycled-> proteins or different compound
- protein not stored in body
- when dietary protein in excess, amino acids:
- oxidized for energy
- converted to fat for storage
Oxidation of amino acids (to use protein as fuel)
- First deaminated (NH2 removed); then converted into
- pyruvic acid
- keto acid intermediate of krebs cycle
- events include transamination, oxidative deamination, and keto acid modification
- > Deamination of AA is necessary for the carbon “skeletons” to enter catabolic pathways. The nitrogenous compounds are metabolic waste products
protein synthesis
- amino acids most important anabolic nutrients
- form all proteins; bulk of functional molecules
-hormonally controlled
- requires complete set of amino acids
- essential amino acids required in diet
catabolic-anabolic steady state of the body
Absorptive State and Postabsorptive State:
-if 3 meals a day
-> Absorptive state (fed state):
lasts 4 hours after eating begins; absorption of nutrients occuring
- > Post absorptive state (fasting state):
- morning, late afternoon, all night; GI tract empty; energy sources supplied by breakdown of reserves
- primary goal during this state is to maintain blood glucose levels
absorptive state
- anabolism exceeds catabolism
- > Carbs:
- glucose major cellular energy fuel
- glucose converted in liver to glycogen or fat
- > triglycerides:
- most glycerol and fatty acids converted to triglycerides for storage
*triglycerides are used by adipose tissue, skeletal and cardiac muscle cells and liver cells as primary energy
- > Amino acids:
- most amino acids used in protein synthesis
- excess deaminated-> stored as fat or used for ATP
absorptive state: hormonal control
-absorptive state primarily controlled by insulin
-insulin secretion stimulated by:
elevated blood levels of glucose and amino acids
insulin effects on metabolism
- > Insulin, a hypoglycemic hormone, enhances:
- Moves glucose into muscle and adipose cells (brain and liver take up glucose without insulin)
- Glucose oxidation for energy
- Glycogen and triglyceride formation
- Active transport of amino acids into tissue cells
- Protein synthesis
- Inhibits glucose release from liver, and gluconeogenesis
homeostatic imbalance
Diabetes Mellitus:
- Inadequate insulin production or abnormal insulin receptors
- >
- Glucose unavailable to most body cells ->
- Blood glucose levels high
- Glucose lost in urine
- Fats and proteins used for energy -> metabolic acidosis, protein wasting, weight loss
Post absorptive state- GI tract empty
-Catabolism of fat, glycogen, and proteins exceeds anabolism
- goal: maintain blood glucose between meals
- makes glucose available to blood
- promotes use of fats for energy (glucose sparing- save glucose for organs that need it most)
Sources of blood glucose
-Glycogenolysis in liver & skeletal muscle
- Lipolysis in adipose tissues and liver
- Glycerol used for gluconeogenesis in liver
- Catabolism of cellular protein
- Major source during prolonged fasting
-Amount of fat in body determines how long can survive without food
During starvation, the body will utilize glycogen and fat stores first, then move to muscle protein first before other tissues. The heart is primarily muscle protein and when severely catabolized the result is death. (enlarged bellies)
true
post absorptive state: hormonal and neural controls
- Glucagon: hyperglycemic hormone. release stimulated by
- declining blood glucose
- rising amino acid levels
-SNS interacts with hormones to control event in post absoptive state (epinephrine)
hyperglycemic hormones include glucagon and
epinephrine
What is the true function of molecular oxygen acquired by the lungs?
O2 serves as the final electron acceptor for the oxidation of food molecules.
effects of glucagon
glucagon promotes:
-glycogenolysis and gluconeogenesis in the liver
-lipolysis in adipose tissue-> fatty acids and glycerol to blood
metabolic role of the liver
Hepatocytes:
-~500 metabolic functions
- Process nearly every class of nutrient
- Play major role in regulating plasma cholesterol levels
- Store vitamins and minerals
- Metabolize alcohol, drugs, hormones, and bilirubin
**Mechanical contraptions can stand in for heart, lungs or kidney but nothing can do the work of the liver.
cholesterol
- structural basis of bile salts, steroid hormones, and vitamin D
- major component of plasma membranes
- 15% of blood cholesterol ingested; rest made in body, primarily liver
- lost from body when catabolized or secreted in bile salts
- not used as an energy source
cholesterol transport
Lipoproteins:
-transport water-insoluble cholesterol and triglycerides in blood
- Higher percentage of lipids -> lower density, hence VLDLs, - very low density lipoproteins
- LDLs, - low density
- HDLs – high density
Lipoproteins
- > VLDLs:
- Transport triglycerides from liver to peripheral tissues (mostly adipose)
- > LDLs (”bad cholesterol”)
- Transport cholesterol to peripheral tissues for membranes, storage, or hormone synthesis
- > HDLs (“good cholesterol”)
- Transport excess cholesterol from peripheral tissues to liver to be broken down and secreted into bile
*Also provide cholesterol to steroid-producing organs
Plasma cholesterol levels
-Ratio of saturated/unsaturated fatty acids affects blood cholesterol levels
- > Saturated fatty acids:
- Stimulate liver synthesis of cholesterol
- Inhibit cholesterol excretion from body
- > Unsaturated fatty acids:
- Enhance excretion of cholesterol
- Enhance cholesterol catabolism to bile salts
- > Trans fats (partially hydrogenated vegetable oil)
- Healthy oils forced to be solids (margarine)
*Increase LDLs and reduce HDLs
plasma cholesterol levels
- unsaturated omega-3 fatty acids (found in cold-water fish)
- lower proportions of saturated fats and cholesterol
- make platelets less sticky-> help prevent sponataneous clotting
- lower blood pressure
Non-dietary factors affecting cholesterol
- Stress & cigarette smoking lower HDL levels
- Aerobic exercise and estrogen increase HDL levels and decrease LDL levels
- Body shape:
- “Apple”: Fat carried on upper body correlated with high cholesterol and LDL levels
-“Pear”: Fat carried on hips and thighs correlated with lower cholesterol and LDL levels
metabolic syndrome
5 risk factors that increase the chance of heart disease, stroke and type 2 DM Inc waist circumference Inc BP Inc blood glucose Inc blood triglycerides Dec blood HDL cholesterol
Obesity
- BMI= weight x 705/height in (inches)^2
- considered overweight if BMI 25 to 30
- considered obese if BMI greater than 30
Obesity
Higher incidence of atherosclerosis, type 2 diabetes mellitus, hypertension, heart disease, and osteoarthritis
short term regulation of food intake
Short term regulation of apetite involves:
-> Neural signals GI tract –
Vagus nerve suppresses hunger center
- > Blood level of nutrients-
- Increased nutrients in blood suppress eating
- ingesting sugar sets off the brain’s reward (pleasure) center releasing dopamine, this may be genesis for overeating
- > GI tract hormones-
- Gut hormones (e.g., insulin and CCK) depress hunger
long term regulation of food intake
Leptin:
-Hormone secreted by fat cells in response to increased body fat mass
- Increased fat cells = increased leptin
- High leptin lowered appetite
- Rising leptin -> some weight loss but to a point; not “magic bullet” for obese patients
- High leptin levels in obese patients; resistant to its action
- Main function: Protects against weight loss in times of nutritional deprivation
additional factors in regulation of food intake
- Temperature – cold activates hunger
- Stress – depends on individual, “survival mode” – store fuel. Increase COH comfort food, increase serotonin – calming effect
- Psychological factors
- Sleep deprivation
