Macronutrition Flashcards
What are excess carbs converted into?
glycogen
triacylglycerol
What are sources of simple carbs?
sugars
fruits, veg
milk
What is the formula for simple sugar molecules?
C6H12O6
What are the monomers in maltose?
glucose
What are the polysaccharides produced in animals?
glycogen
what are the polysaccharides produced in plants?
starch
fiber
What’s another name for glucose?
dextrose
What is the most important carb for the body?
glucose
Where is fructose found?
fruits, veg
more than half the sugar in honey
What effect does fructose consumption have?
does not have big rise in BG
increases blood lipids
What is sucrose?
common white table sugar
sugar cane, sugar beets, honey, and maple syrup
glucose + fructose
What is lactose?
milk sugar
glucose + galactose
What is maltose?
disacchardie in starch
glucose + glucose
What ar e the components of starch?
amylose
amylopectin
What is amylose?
linear chains of glucose molcules
alpha-1,4-glucosidic bonds
What is amylopectin?
branched chains of glucose molecules
branch points with alpha-1,6-glucosidic bonds
ratio of 1,4- to 1,6-glucosidic bonds is about 20:1
Describe the structure of glycogen.
like amylopectin, glycogen is branched.
What is responsible for the digestion of carbs?
alpha-amylose
enzymes on the luminal surface of small intestine
What carb unit is absorbed by the body?
monosaccharides
Describe the function of alpha-amylase.
Hydrolyzes starch and glycogen to maltose and maltotriose.
Exists in saliva and pancreatic juice.
What enzymes are on the surface of the small intestine?
maltaste
sucrase
lactase
What is the function of maltase?
aka alpha-glycosidase:
maltose and maltotriose –> glucose
What is the function of sucrase?
sucrose –> glucose and fructose
What is the function of lactase?
lactose –> glucose and galactose
What is the pathology of lactose intolerance?
not enough lactase is produced
How do bacteria contribute to carb digestion?
Bacterial enzymes converts indigestible carbs to monosaccharides. This are metabolized anaerobically by bacteria, resulting in the production of short-chain FAs, lactate, H2, CHR, and CO2.
May cause flatulence and abdominal discomfort.
What is raffinose?
oligosaccharide in leguminous seeds (beans and peas)
cannot be hydrolyzed by human enzymes (flatuence)
What is the glycemic index?
a measur eof how quickly individual foods will raise blood glucose level.
defined as the ratio of the area of the blood glucose response curve to that of glucose
What is an example of a food with a high glycemic index?
potato, white bread
What is an example of a good with a low glycemic index?
ice cream
kidney beans
What is the brain’s preferred energy source?
glucose!
What glucose transporters are not insulin -dependent?
GLUT3 in brain
GLUT2 in liver
Which glucose transporter is for muscle and adipose tissue?
GLUT4 (insulin -dep)
How to RBCs metabolize glucose?
no mitochondria so convert pyruvate to lactate
What are examples of dietary fibers?
cellulose and hemicellulose
lignin
pectin
Describe cellulose and hemicellulose.
insoluble dietary fiber.
incr stool bulk and decr intestinal transit time
found in unrefined cereals, bran, whole wheat
Describe lignin.
insoluble dietary fiber.
binds cholesterol and carcinogens.
Found in the woody parts of veg
Describe pectin.
Soluble dietary fiber.
Found in fruits.
Decreases rate of sugar uptake and decreases serum cholesterol.
What are the functions if lipid in the diet?
energy: 9kcal/g
satiety
flavor and aroma
carrier for fat-soluble vitamins
What is most dietary fat?
triacylgycerol (90%):
glycerol + three fatty acids
Which types of lipids make up <10% of dietary fat?
phospholipids, cholesterol, cholesterol esters, fatty acids.
Describe saturated FAs.
contain no double bond; higher melting temp.
associated with many health risks such as heart disease and stroke.
Which are the most common saturated FAs found in foods?
palmitic acid and stearic acid
Describe unsaturated FAs.
contain double bonds, lower melting temperature
What are the most common unsaturated fatty acids found in foods
oleic (monounsat, 18:1) and linoleic (polyunsat, 18:2)
What are the essential omega-3 FAs?
alpha-linolenic acid (18:3) in veg oils eicosapentaenoic acid (EPA) (20:5) and docosahexaenoic acid (DHA) (22:6) in fish oils
What are the essential omega-6 FAs?
linoleic acid (18:2) in corn oil arachidonic acid (20:4) in meat and fish
What are the functions of essential FAs?
used to synthesize eicosanoids in the body
What does the ratio of omega-3 to omega-6 FAs in the diet regulate in the body?
blood pressure
blood clotting
immune function
What is the prevalence of essential FA deficiency in US?
rare
need to be added to artificial infant formula
How are trans fatty acids different from cis?
higher melting point
raise blood cholesterol levels and increase the risk of heart disease
produced as byproduct of hydrogenation (to produce margarine and shortening)
How are fats digested?
solubilized
gastric and pancreatic lipases
esterase
How are fats solubilized?
bile acids
What is the function of gastric and pancreatic lipases?
Hydrolyze triacylglycerol to FAs and monoacylglycerol.
Produced FAs act as surfactants.
What is the function of esterase?
hydrolyzes monoacylglycerol and cholesterol ester.
How are lipids delivered to peripheral tissues?
directly by chylomicrons
What uses fats as an energy source?
muscle
NOT the brain
What is the fate of excess fat?
adipose tissue
What does the liver do with FAs during starvation?
converts FAs to ketone bodies, whch are utilized as energy source by brain and muscle
What are the functions of dietary proteins?
structural component (20% of wt!) enzymes, hormones, plasma proteins, antibodies
What is excess protein used for?
energy source!
glucogenic amino acids are converted to glucose
ketogenic amino acids are converted to keto acids and FAs.
eventually these are converted to triacylglycerol in adipose tissue.
What does a negative nitrogen balance indicate?
inadequate dietary intake of protein
trauma or illness
What does a positive nitrogen balance indicate
net increase in body protein stores
growing children
pregnant women, or adults recovering from illness
What does nitrogen balance describe?
balance between intake of protein in diet and excretion of urea and ammonia
What are some examples of essential amino acids?
arginine
methionine
phenylalanine
(and many more)
What is an example of a conditionally essential amino acid?
tyrosine if not enough phenylalanine
How are proteins digested?
gastric
peptidases at luminal surface
intracellular peptidases
Describe gastric digestion.
pH of gastric juice <2
denature proteins
pepsins–stable and active at acidic pH; aspartic protease
Describe the action of peptidases at the luminal surface of intestine.
brush border is rich in peptidases
produce free amino acids and di- and tripeptides
Describe the action of intracellular peptidases of intestinal cells.
amino acid and peptide transport systems.
IC hydrolysis of di- and tripeptides
practically only free amino acids are released into the blood.
What happens to absorbed amino acids?
portal vein–> liver –> high Km enzymes miss most AAs –> tRNA-charging enzymes have lower Km values so AAs are used for protein synthesis or energy in other tissues
This means that AA are metab’d only when their conc is high
What is Celiac sprue?
gluten intolerance
autoimmune disorder in genetically predisposed individuals
upon gluten exposure the intestinal lining becomes inflamed and damaged: diarrhea, weight loss, malnutrition.
What are sources of gluten?
wheat, rye, barley
What is the treatment for Celiac sprue?
life-long gluten-free diet
What is the energy content of alcohol?
7 kcal/g
What energy reserve do humans have?
adipose tissue
glycogen in liver (BG)
glycogen in muscle
NOT protein
What occurs in the well-fed state?
insulin release glycolysis glycogen synthesis catabolism of AAs FA synthesis no gluconeogenesis (Cori cycle)
What occurs in the early fasting state?
glucagon release
glycogen breakdown
gluconeogenesis –> cori and alanine cycles
no catabolism of AAs
What is the Cori cycle?
aka glucose-lactose cycle
Glucose generated by gluconeogenesis in liver is used for glyclysis in peripheral tissue.
NADH generated by glycolysis is used to reduce pyruvate to lactate.
–> important when O2 low
RBCs rely on Cori cycle bc do not have mitochondria
What occurs in the alanine cycle?
Like Cori cycle, glucose generated by gluconeogenesis in liver is used for glycolysis in a peripheral tissue.
NADH generated by glycolysis is used to produce ATP.
Amino nitrogen is transferred to liver and disposed of as urea.
What occurs in the fasting state?
glucagon release
gluconeogenesis
protein is used as a carbon and nitrogen source (alanine, glutamine)
lipolysis in adipose tissue
FA oxidation
ketogenesis
reduced thyroid hormones –> basal energy req drops by 25%
Below what concentration of glucose does coma and death result?
<1.5 mM
What are consequences of hyperglycemia?
dehydration
hyperglycemic coma
complications of diabetes
What are special aspects of energy requires of the brain?
needs a ton of glucose
maintains membrane potential through Na/K ATPase
No energy storage (no glycogen, no fat usage)
adapts to starvation using ketone bodies from acetyl-CoA in liver
How is energy utilized during low level exertion?
FA oxidation
aerobic
How is energy utilized during moderate to high actvity?
glycogen to glycolysis
switch over to FA oxidation
aerobic
How is energy utilized during maximum exertion?
phosphocreatine and glycogen anaerobic lactic acid production very little inter-organ cooperation <1 min
Describe Marasmus.
inadequate intake of both protein and energy
thin, wasted appearance
small for age
Describe Kwashiokor
inadequate protein intake
usually in children 1-3 yoa
edema
