Metabolism, Thermoregulation, and Exercise Physiology

metabolism

chemical processes converting food into energy

homeostatic set point

stable body weight maintained by equal energy intake and output

Body weight is determined by..

-combination of environmental and hereditary factors
-30-50% of variation between individuals is due to heredity
-rest of variation is due to eating and exercise habits

one calorie

amount ofeat required to raise 1 g of water 1 °C

1000 calories = _____ kilocalorie

1

fats contain ____ kcal/g

9

carbohydrates and proteins contain _______ kcal/g

4

sugar and alcohol are "empty" calories, containing few nutrients (T/F).

true

substance used for fuel is..

oxidized primarily to make ATP

nutrients

ingested chemicals used for growth, repair, or maintenance

macronutrients

nutrients needed in large amounts: proteins, fats, carbs

micronutrients

nutrients needed in small amounts, like vitamins

essentrial nutrients that cannot be synthesized (must be ingested/eaten)

-minerals
-vitamins
-8 amino acids
-1 to 3 fatty acids must be consumed in the diet

carbohydrates can be found in these 3 places in the body

-muscle
-liver glycogen (storage)
-blood glucose (to be used)

most carbohydrates serve as..

fuel (neurons and RBCs depend on glucose)

blood glucose is carefully regulated by what?

insulin and glucagon

Recommended Daily Allowance (RDA)

safe estimate of daily nutrient intake

why is the RDA for carbohydrates greater than any other nutrient (175g/day)?

carbohydrates are rapidly oxidized

dietary sources for carbohydrates

-monosaccharides: glucose, galactose and fructose
-disaccharides: table sugar (sucrose), maltose, lactose
-polysaccharides: starch, glycogen, and cellulose

how does the liver make glucose?

converts galactose and fructose

normal blood sugar concentration

70-110 mg/dL

outside hepatic portal system, only blood sugar is glucose (T/F)

true

nearly all dietary carbohydrates comes from what?

plants

essential nutrients

nutrients that must be consumed, cannot be synthesized

glycogen

stored form of glucose in liver and muscles

dietary fiber

fibrous material aiding digestion, RDA is 30 g/day.

excess fiber

interferes with mineral absorption-- iron

water soluble fiber

-decreases blood cholesterol and LDL levels

-not as beneficial for intestines

-i.e. pectin

water-insoluble fiber

-absorbs water in intestines, softens stool, gives it bulk, speeds transmit time
-i.e. cellulose, lignin

lipids

-body's stored energy
-hydrophobic
-contains 2X energy/g
-compact storage
-glucose and protein sparing (no protein utilized for energy)

fat soluble vitamins (A,D,E,K) absorbed with ________ fat

dietary (ingesting less than 20 g/day risks deficiency)

structural functions of lipids

phospholipids and cholesterol are components of plasma membranes and myelin

functions of lipids as chemical precursors

-cholesterol: a precursor of steroids, bile salts, and vitamin D (rings)

-fatty acids: precursors of prostaglandins and other eicosanoids (fatty acid tails)

fat daily requirement

should be less than 30% of daily calorie intake

typical fat intake for most Americans

40-50%

are most fatty acids consumed or synthesized?

synthesized

saturated fats

animal origin (meat, egg yolks, and dairy products)

unsaturated fats

found in nuts, seeds, and most vegetable oils

where is cholesterol found?

egg yolks, cream, shellfish, organ meats and other meats

serum lipoproteins

-lipids transported in blood as lipoproteins
-protein and phospholipid coat around a hydrophobic cholesterol and triglyceride core
-soluble in plasma; bind to cells for absorption

serum lipoprotein are categorized by what?

density; more protein = higher density

chylomicrons

-transport lipids from intestines to blood

-form in absorptive cells of small intestine

-enter lymphatic system, then blood

-smallest lipoprotein

VLDL

-very low-density lipoproteins, transport lipids to adipose tissue for storage
-when triglycerides removed --> becomes LDL (mostly cholesterol)

LDL

-low-density lipoproteins, deliver cholesterol to cells
-absorbed by cells in need of cholesterol for membrane repair or steroid synthesis?

HDL

-high-density lipoproteins, remove cholesterol from arteries
-travels through blood, picks up cholesterol (plaque) and delivers to liver for elimination in bile

what is considered "bad" cholesterol

VLDL and LDL

serum lipoprotein composition

phospholipid, triglyceride, cholesterol, protein (different percentages depending on molecule)

desirable cholesterol concentration

<200 mg/dL

most cholesterol is..

endogenous

how to lower blood cholesterol levels

-by 5% with restriction of dietary cholesterol

-by 15-20% with restriction of certain saturated fats

-vigorous exercise lowers blood cholesterol (and increases HDL)

other factors affecting cholesterol?

-genetic and gender
-i.e. women going through menopause are unable to regulate cholesterol levels

desirable lipoprotein levels

-high levels of HDL (indicate cholesterol is being removed from arteries)
-low levels of LDL (high levels correlated with cholesterol deposits in arteries)

recommendations to maintain desirable lipoprotein levels

-exercise regularly
-avoid smoking, saturated fats, coffee and stress

3 pathways of processing lipoproteins

-chylomicron pathway (lymph system to blood)
-VDL/LDL pathway
-HDL pathway

proteins

-12 to 15% of body mass
-mostly in skeletal muscles

protein functions

-muscle contraction
-movement of body, cells, cell structures
-structural
-functional

examples of proteins functioning in body movement, cells and cell structures

-in cell membranes (receptors, cell identity, pumps)
-fibrous proteins (collagen, keratin)

examples of structural proteins

globular proteins (antibodies, myoglobin, enzymes)

examples of functional proteins

plasma proteins (blood osmolarity and viscosity)

RDA for protein

-44-60 g/day
-differs for activity levels, breastfeeding, pregnancy

12-15% of body mass is __________, mostly in skeletal muscles

protein

nutritional value of proteins depends on proportions of..

amino acids

8 essential amino acids CANNOT be synthesized (T/F)

true

cells store surplus protein (T/F)

false

complete proteins (dietary)

supply all amino acids in right amount needed to synthesize protein

dietary sources: animal proteins

-meat, eggs, and dairy
-are complete proteins
-closely match human proteins in amino acid composition

dietary sources: plant proteins

-must be combined in the right proportions
-beans and rice

nitrogen balance

rate of nitrogen ingestion equals rate of excretion

chief dietary source of nitrogen

proteins

positive nitrogen balance

-more nitrogen ingested than excreted
-common in child growth, a goal with athletes
-promoted by growth and sex hormoens

negative nitrogen balance

-more nitrogen excreted than ingested, leads to muscle loss
-body proteins are being broken down for fuel (muscle atrophy)
-glucocorticoids promote protein catabolism in states of stress (starvation)

calcium functions

-forms & maintains bones & teeth
-coagulates blood

phosphorus functions

phospholipids, ATP, CP, buffers, nucleic acids

calcium, magnesium, copper and manganese are..

cofactors for enzymes

iron is essential for..

hemoglobin and myoglobin synthesis

chlorine function

component of stomach acid (HCl)

mineral salts function

electrolytes; govern function of nerve and muscle cells, regulate distribution of body water

dietary source of minerals

-vegetable, legumes, milk, eggs, fish and shellfish
-animal tissues contain large amounts of salt

herbivores vs carnivores -- who lacks salt in their diets?

carnivores rarely lack salt in their diets, herbivores must often supplement by ingesting soils (salts from the earth)

RDA for sodium intake

1.1 g/day

typical American diet contains ______g sodium intake per day, outside the normal values

4.5

Urea Synthesis

Conversion of ammonia to urea in the liver.

body synthesizes these vitamins, from precursors

-niacin, vitamin A and D
-vitamin K, pantothenic acid, biotin, folic acid (produced by intestinal bacteria)

water soluble vitamins

-vitamin C, B

-absorbed with water in small intestine; not stored

fat soluble vitamins

-vitamin A, D, E & K

-absorbed with dietary lipids; stored

formula for carbohydrate metabolism (glucose catabolism)

C6H12O6 + 6O2 → 6CO2 + 6H2O

glucose carabolism

series of small steps to efficiently transfer energy to ATP (reduces energy lost as heat)

3 major pathways for glucose catabolism

-glycolysis
-aerobic respiration
-anaerobic fermentation

net ATP produced in glycolysis

2

during glycolysis, the 6C glucose molecule splits in 2 ______________ molecules, which hold 3C each

pyruvic acid

net ATP produced in aerobic respiration

34-36

during aerobic respiration, pyruvic acid is completely oxidized into _______ and _________

CO2 and H2O

anaerobic fermentation causes pyruvic acid to....

reduce to lactic acid

purpose of anaerobic fermentation

to replenish NAD+ so glycolysis can continue

ATP is quickly used after it is formed- it is not a storage molecule (T/F).

true

what will happen to extra glucose in the body?

will NOT be oxidized, will be stored as glycogen

glycogenesis

-synthesis of glycogen

-stimulated by insulin (average adult contains 450g)

glycogenolysis

-glycogen --> glucose

-stimulated by glucagon and epinephrine

the only cells that can release glucose back into bloodstream

liver cells

gluconeogenesis

-synthesis of glucose from non-carbohydrates, such as fats and amino acids