Metabolism

Chapter 25 - pages 962-987

Linking anabolism & catabolism

Topics in Chapter 25

In A&P I glucose catabolism ATP was discussed

This semester in Ch 25 focus on: Glucose anabolism Lipid metabolism Protein metabolism Metabolism during absorptive and post absorptive

states Heat and energy balance Nutrition

Glucose

Most glucose catabolized to make ATP Some used in anabolic rxns:

To produce glycogen To produce more glucose from lipid and protein

components

Do not confuse these terms!

Glucose Glycogen Glucagon Glycolysis Glycogenolysis Glycogenesis Gluconeogenesis

Glycogenesis fig 25.11

Glucose storage Occurs when glucose not immediately needed for

ATP synthesis _____________- stimulates hepatocytes &

skeletal muscle cells to carry out From pancreatic beta cells

______________ - polysaccharide, polymer of glucose and only stored carb in our body 75% stored in skeletal muscle 25% in hepatocytes

Glycogenolysis fig 25.11

Glucose release Body activities require ATP glycogen stores in

hepatocytes break down Glucose blood cells for catabolism

Glucose ATP Lactic acid (in muscle) glucose (in liver)

Phosphorylase activated by ____________ (from pancreatic alpha cells) & ___________ (adrenal medulla)

Reversal of steps in glycogenesis

Glycogenesis & glycogenolysis

Insulin pg 646-649 Released in response to blood glucose

Ach released from vagus nerve _________________ Certain amino acids in blood (after protein meal) ________ – s.i. hormone released due to glucose in gi tract

Accelerates facilitated diffusion of glucose glycogenesis (glucose glycogen) a.a uptake for protein synthesis f.a. synthesis Slows glycogenolysis Slows gluconeogenesis

Fig 18.18

Figure 18.19

Glucagon

Stimulates ________________ in liver cells Stimulates ________________ Glucose released into blood Secretion stimulated by:

Low blood glucose activity of sympathetic NS (as w/exercise) a.a in blood if blood glucose is low (after high

protein meal)

Gluconeogenesis

Newly formed glucose Non carbohydrate sources:

Lactic acid Glycerol Amino acids – about 60% of a.a. in body can be

used for this Stimulated by:

_______________(glucocorticoid) _______________

Gluconeogenesis fig 25.12

Glucose tolerance

Test body’s ability to process glucose Diagnostic for hypoglycemia, __________

__________, or malabsorption syndrome Dependent upon ability of:

Pancreas to produce & release insulin Cell response to insulin (membrane sensitivity) Small intestine to absorb glucose Liver to take up & store glucose

Glucose tolerance (2)

________ mg/100 mL blood =normal, fasting “Load” glucose within 1 hour Normal – followed by gradual decline Abnormal – glucose levels remain elevated

Insulin response major factor See lab manual, exercise 3 for more info

Diabetes mellitus

Endocrine disorder, inability to produce (type 1) or use (type 2) insulin

4th leading cause of death by disease in US Type 1= insulin-dependent diabetes mellitus

____________________ destroys pancreatic beta cells Insulin injections required to prevent death

Type 2- non-insulin dependent More common than type 1 >90% of cases Often obese >35 yr, but, type 2 obese children & teens Target cells ____________ to insulin, downreg of receptors

Lipoproteins are transporters

__________________- lipid & protein combination Outer- proteins, phospholipids, & cholesterol

Proteins help solubilize lipids in body fluids Inner core- triglycerides and other lipids

Categorized by _________ (lipids = low, proteins = high density) Chylomicrons- s.i., many dietary lipids adipose VLDLs- very low density lipoproteins, form in hepatocytes,

lipids adipocytes for storage or muscle LDLs- carry ≈75% of total cholesterol in blood which goes to:

Cell membranes for repair, synthesis of steroid hormones, bile salts When in excess deposit in smooth muscle of arteries fatty plaque

HDLs- remove excess cholesterol from cells liver (elimination)

Lipoprotein figure 25.13

Pathways of lipid metabolism

Metabolic regulation depend on: Chemical environment in cell

ATP level Oxygen

Nervous system Endocrine system Some functions of metabolism depend on-

time since last meal

Absorptive state figure 25.17 Ingested ______________________

necessary for 2 main events of this state: Oxidation of glucose for ATP production Storage of excess food molecules occurring (for

later use between meals) Hepatocytes, adipocytes, skeletal muscle

4 hours for complete absorption _____________ dominates during this state

Reactions (absorptive state) figure 25.17 ≈50% glucose absorbed from meal _________ Most glu that enters liver (≈10%) ___________ Some f.a. & triglycerides syn in liver

Some stay in liver Most VLDLs to carry lipids to adipose

Adipocytes uptake glu (≈40%) _____________ Most dietary lipids adipose tissue

Chylomicrons, VLDLs, or synthesized Many a.a. liver Krebs- ATP, or syn glu & fa Some a.a. hepatocytes synthesize proteins a.a not taken up in hepatocytes body cells

synthesis of proteins, hormones, or enzymes

Absorptive state

Regulation of metabolism- absorptive

GIP+ blood glu (& some aa)______________ Insulin: (see table 25.3)

enzymes of anabolism & syn to storage molecules enzymes of catabolism Promotes glucose & a.a ____________________ Stim. phosphoyrlation of glu - hepatocytesG6P Stim. G6P glycogen in liver & muscle Enhances _____________________(liver & adipose) Stim. protein syn throughout body

Postabsorptive statefigure 25.18 ________ of nutrients from GI tract ________ Bodily energy needs being met by fuel

already created If no snacks, times 4 hours spent in

postabsorptive state (late morning, late afternoon, most night)

__________________ involved in regulation Glucose production & glucose conservation

Postabsorptive – glucose production

ATP dominant fuel in ______ (fa can’t cross bbb) RBC get ATP from glycolysis - lack mitochondria Rxns that _____________________ in this state:

Breakdown of liver glycogen Lipolysis Gluconeogenesis using lactic acid Gluconeogenesis using amino acids

Postabsorptive– glucose conservation Reactions to _______________ in this state:

Oxidation of fatty acids Oxidation of lactic acids (in cardiac muscle) Oxidation of amino acids (in hepatocytes) Oxidation of ketone bodies

Can be used by heart, kidneys, & other tissue ATP breakdown of muscle glycogen

Glycogen G6P (glycolysis) ATP

Postabsorptive state

Regulation of metabolism – postabsorb Hormones

______________ hormones: Glucagon- gluconeogenesis & glycogenolysis See table 25.4 for summary

Sympathetic NS Glucose sensitive neurons activate release of NT

norepinephrine Adrenal medulla releases

Epinephrine – stimulates glycogen breakdown Norepinephrine – both NE & E stimulate lipolysis

Metabolism- fasting & starvation ___________- w/out food several hours – few days

Glycogen stores depleted within hours Protein catabolism > anabolism, aa gluconeo

_______________- weeks or months of food deprivation or inadequate intake Triglyceride & proteins stores- last several weeks Amt of adipose tissue determines survival time

During both: Nervous tissue & RBC use glucose ATP ketone bodies in hepatocytes plasma bbb

glu needed for ATP syn, need for gluconeo, catabolism of muscle proteins

Heat and energy

Heat- form of energy Measured by temperature Expressed in units- calories

calorie (cal) = amt of heat to temp of 1g of water 1°C cal is small use kilocalories (kcal) or Calorie (Cal)

Core body temp = 37°C, shell = 1-6°C less Too high denatures body proteins Too low cause cardiac arrhythmias ( death)

Heat production

________________ Hormones–thyroid, testosterone, insulin, hGH _________________ – NE & E Body temp - body temp biochem rxns Ingestion of food – energy cost of digestion ________ – child > elderly ( during growing) Others: gender (males > females, exception-

pregnancy ), climate, sleep, malnutrition

Metabolic Rate

Overall rate at which metabolic rxns use energy _________________- body quiet, resting & fasting BMR- measure amt of oxygen used per kilocalorie

of food metabolized 1L ____________ to oxidize mix of carbs, proteins

& fats 4.8 Cal of energy released BMR ≈ 1200-1800 Cal/day in adults

Added calories needed: 500 small relatively inactive person 3000 for a person training for the Olympics

Accounts for ≈60% of energy expenditure

Thyroid hormones & metabolism TRH (hypothalamus) TSH (pituitary)

release thyroid hormones ___________________ in skin &

hypothalamus sense temp TRH release Thyroid hormones released in bloodstream

Slowly _____________ by stimulating cell resp. Cells use more O2 body temp 1°C rise in core temp biochemical rxns by 10%

Part of negative feedback loop (fig 25.19)

Vitamins–fat vs. water soluble, table 25.6 Vitamins – organic nutrients- small amt to maintain growth & metab

Do not provide energy, function as coenzymes Most must be ingested, cannot be synthesized

_______________ vitamins- absorbed w/dietary lipids in chylomicrons, need lipids to be absorbed adequate quantities Can be stored in cells (esp. hepatocytes) Vitamins A, D, E, K -- see table for functions

Water soluble vitamins- dissolved in bodily fluids Excess quantities excreted in urine Several B vitamins, vitamin C – see table

C, E and beta-carotene-________________________

Vitamin SourceFunctionA, fat soluble Carotene (veg),

liver, milk General health of epi cells, antiox.

B complex, fat Whole grain, egg, pork, nuts, liver & yeast

metabolism, Ach synthesis, steroid hormones

C, water Citrus, tomatoes, green vegetables

Protein syn, Ab, collagen form, antioxidant

D, fat Fish-liver oil, egg yolk, fortified milk

Absorb Ca & P, works w/PTH

K, fat Intes bacteria, spinach, cauli, cabbage, liver

Synthesis of several clotting factors by liver

Importance of minerals table 25.5 Minerals – inorganic elements occur naturally in earth’s crust

4% of total body mass, heavily conc in _____________ Body generally uses ion form

Na – distribution of water, bicarbonate buffer, AP K – generation & conduction of AP Ca – form bones & teeth, clotting, nerve & muscle activity, endo

& exocytosis, cell & chromosome motility, glycogen metab, rel NT & hormones

Fe – component of Hb & cytochromes in ETC P – form bones & teeth, blood buffer system, nerve & muscle

activity, energy transfer (ATP), part of DNA, RNA I – req by thyroid to make hormones, reg metabolic rate

Nutrition figure 25.20 Nutrients- chemical substances in food body

cells use (growth, maintenance, & repair) Water, carbs, lipids, proteins, minerals, vitamins

Dietary Reference Intake (DRI)- or Recommended Daily Allowance (RDA)

http://fnic.nal.usda.gov/nal_display/index.php?info_center=4&tax_level=2&tax_subject=256&topic_id=1342&placement_default=0

Proteins listed as macronutrients on website

Amino acids

Building blocks for structural & functional cmpds in the body (enzymes, membrane carriers, hormones)

_______________amino acid or ________________amino acid – that which cannot be synthesized by the body and must be acquired through dietary intake Histidine, isoleucine, leucine, lysine, methionine,

phenylalanine, theronine, tryptophan & valine Nonessential amino acid – can be made by human

body

Protein types and sources

_____________ proteins – the 9 indispensible a.a. are found in animal sources – meat, fish, poultry, eggs, milk, cheese and yogurt

Incomplete proteins- sources that lack 1 of the 9 indispensible a.a., are found in plants, legumes, seeds, grains, nuts, & vegetables

Complementary protein combinations- those that give all the indispensible a.a. by combining incomplete with complete protein sources

DRI establishment – see www.nap.edu Are developed from recommended daily allowance

& adequate intake Increases from infancy thru childhood to adulthood-

RDA = for males & females up to the age of 13 = 34 g/day

RDA levels off: age 19-30 males = 56g/d Age 14-18 females = 46g/d

Males have higher RDA than females Pregnancy – double amt of 9-13 yr old girl (71g/d) Lactation – same as pregnancy