Lecture 21 -- review questions Flashcards
what is nutrition?
the process of providing or obtaining the food necessary for health and growth
what is digestion?
catabolic process that breaks down large food molecules to monomers (chemical building blocks)
what is hydrolysis?
the enzymatic breakdown of any food molecule is hydrolysis
involves adding a water molecule to each molecular bond to be broken (lysed)
what are the monomers of carbs, proteins, lipids, and nucleic acids?
carbs – monosaccharides
proteins – amino acids
lipids – fatty acid, glycerol
nucleic acids – nucleotide
what is the absorption?
the process of moving substances from the lumen of the gut into the body
capillaries (villi) –> hepatic portal system –> liver
what is metabolism?
sum of all biochemical reactions in the body
- anabolism – build
- catabolism – break down
what is the main difference between catabolism and anabolism?
both are types fo metabolism (sum of all biochemical reactions in the body)
anabolism – all reactions that build larger molecules or structures from smaller ones
catabolism – all processes that break down complex structures to simpler ones
what is a nutrient?
a substance in food the body uses to promote growth, maintenance, and repair
what is an essential nutrient?
those that are inadequately synthesized by body cells and must be ingested in the diet
what are the 6 major nutrient categories?
(1) carbs
(2) protein
(3) fats
(4) water
(5) vitamins
(6) minerals
what is the difference b/n micronutrients and macronutrients?
macronutrients
- must be consumed in relatively large quantities
- supply energy and are used as building blocks
micronutrients
- only small quantities are required
what are the 4 macronutrients?
(1) carbs
(2) protein
(3) fats
(4) water
what are the two micronutrients
(1) vitamins
(2) minerals
what is meant by percent (%) of daily caloric intake?
recommended proportion of energy supply
what percentage of your daily caloric intake should carbohydrates, proteins, and fats make up?
carbohydrates – 45-65%
proteins – 10-35%
fats – 20-35%
what macronutrient should we eat most as a percentage of total calories?
carbohydrates (45-65%)
what are calories?
1 calorie = the amount of heat (energy) needed to raise the temperature of 1 gram of water by 1 degree C
what is the difference b/n calories, Calories, and kilocalories?
1000 calories = 1 Calorie (C) = 1 kilocalorie (kcal)
what does Calorie represent?
units that represent the ability of food to be converted by the body into energy
what are the 3 energy-yielding nutrients?
(1) carbohydrates
(2) proteins
(3) fats
how many calories are produced when 1 gram of carbohydrates, fats, and proteins are fully oxidized in our body?
carbohydrates – 4 kcal/g
proteins – 4 kcal/g
fats – 9 kcal/g
what is an empty calorie?
calories that contribute to your total caloric intake but supply little or no nutritional value
ex. alcohol or sugary foods
why is alcohol not a class of nutrients despite its high-calorie content?
alcohol (7.1 kcal/g) promotes malnutrition by providing “empty calories” –> they decrease appetite but fails to provide other nutrients
which of the following vitamins are water-soluble or lipid-soluble: A, B, C, D, E, K?
water-soluble:
- B, C
“white buffalo chicken”
lipid-soluble:
- A, D, E, K
“LADEK”
“lost apples don’t eat kale”
which of the 2 vitamin groups, water-soluble or lipid-soluble, has a higher risk of accumulating in your body until reaching toxic levels? Why?
lipid-soluble
they are absorbed with dietary lipids so can be stored in body
how are water-soluble vitamins absorbed and excreted from the body?
absorbed w/ water by simple diffusion
(water is absorbed by osmosis, following the absorption of salts and organic nutrients that create an osmotic gradient)
excreted in urine –> not stored in body
how is vitamin B12 absorbed from the intestines?
needs to bind to intrinsic factor (IF) secreted by the stomach’s parietal cells – specific receptor
is ferrous (Fe2+) iron or ferric (Fe3+) iron more absorbable?
Fe2+ (ferrous iron) is more absorbable
what is the function of ferroportin?
transports iron into the bloodstream
where can you find ferroportin?
enterocytes in duodenum
liver
macrophages
what is the function of transferrin?
take up Fe2+ from FPN to transport Fe2+ throughout the body via bloodstream to various tissues
- liver (storage)
- bone marrow (hemoglobin synthesis)
- muscle (myoglobin synthesis)
what happens to the iron released by macrophage degradation of senescent red blood cells?
is it recycled?
Fe2+ from macrophage degradation gets taken up by transferrin to spread throughout bloodstream –> reaches organs like bone marrow, muscle, and liver
it is recycled/used again
why does transferrin transport iron to bones and muscles?
bones – hemoglobin synthesis (erythropoiesis – make RBCs)
muscles – myoglobin synthesis
what is ferritin?
iron storage protein that stores excess iron
present in liver, spleen, muscle tissue, and bone marrow
how is iron stored in the cell?
thru ferritin (iron storage protein)
which organ represents the primary storage site for iron?
liver
what is hepcidin? what is its main goal, increase or decrease blood levels of iron? how does it achieve this?
liver hormone
main goal to decrease blood levels of iron
inhibits Ferroportin –> decreases iron absorption and mobilization –> lowers blood levels of iron
will an increase in blood iron increase or decrease the production of hepcidin by the liver? why?
increase in blood iron == increase production of Hepcidin
hepcidin needs to be produced in order to lower the blood iron levels to normal
negative feedback loop
will an increase in red blood cells increase or decrease the hepcidin produced by the liver why?
increase in RBCs == decrease hepcidin production
RBCs need iron to survive == will take up all the iron and need more iron to survive == hepcidin will not be produced (this would decrease iron levels)
in which 2 main organs does digestion of carbohydrates take place?
oral cavity
small intestine
where does digestion of carbohydrates start?
oral cavity
what is a polysaccharide?
long polymer chain of monosaccharides
ex. starch
what enzyme is there in the saliva that digests polysaccharides?
amylase
why does the digestion of carbohydrates not continue in your stomach if the bolus from your mouth also carries some salivary amylase?
low pH of stomach inactivates salivary amylase
where does the amylase in your small intestine come from?
pancreas
which 2 brush border enzymes act on oligosaccharides composed of more than 3 simple sugars?
dextrinase
glucoamylase
what are disaccharides? give 3 examples
disaccharide == 2 monosaccharide units joined together
(1) maltose
(2) sucrose
(3) lactose
where can you find disaccharides in the digestive system?
brush border of the small intestine (composed of enterocytes)
where are monosaccharides absorbed?
small intestine
are monosaccharides absorbed into blood or lymph?
blood thru blood capillaries of the villus
hepatic portal system then delivers them to the liver
what is the primary purpose of cellular respiration?
generate ATP
(energy-carrying molecule that releases energy to fuel cellular processes)
what is the equation for aerobic respiration of glucose?
C6H12O6 + 6 O2 –> 6 CO2 + 6 H2O
what are the 3 consecutive pathways of glucose aerobic respiration?
(1) glycolysis
(2) citric acid cycle
(3) electron transport chain
how is energy stored in the body?
carbohydrates and fats
what is the role of ATP?
energy-carrying molecule that releases energy to fuel cellular processes
what is the role of NAD or FAD?
coenzymes that carry extracted energy to use in the electron transport chain to synthesize ATP
carry “high energy” electrons and carry them to the ETC to be used to help synthesize ATP molecules
ETC establishes proton gradient that is used to produce ATP
what molecules are the starting and end product of glycolysis?
starting – glucose
ending – pyruvate
how many pyruvate are obtained per molecule of glucose being oxidized in glycolysis?
2
what pathway does pyruvic acid enter in the absence of oxygen? and in the presence of oxygen?
absence of oxygen – anaerobic fermentation
presence of oxygen – citric acid cycle (aerobic pathway)
what is pyruvate converted to enter the citric acid cycle?
acetyl CoA
is the citric acid cycle and Krebs cycle the same?
yes
what is the final pathway to produce ATP in glucose metabolism?
electron transport chain and
oxidative phosphorylation
what ion gradient is used to make ATP?
proton (H+) gradient that is established by the ETC
what is glycolysis?
type of carbohydrate metabolism (to make sure just the right amount of glucose is present in the blood)
glucose –> pyruvic acid
what is gluconeogensis?
type of carbohydrate metabolism (to make sure just the right amount of glucose is present in the blood)
forms glucose from noncarb precursors (fat or protein)
pyruvate –> glucose
what is glycogenesis, and when does it occur?
type of carbohydrate metabolism (to make sure just the right amount of glucose is present in the blood)
when cellular ATP reserves are high, glucose is converted to glycogen (glycogenesis)
glucose –> glycogen
what is glycogenolysis, and when does it occur?
type of carbohydrate metabolism (to make sure just the right amount of glucose is present in the blood)
hydrolyzes glycogen to glucose monomers
when blood glucose levels begin to fall
glycogen –> glucose
what is the general name of the enzymes that act on proteins?
peptidases/proteases
what enzyme begins the digestion of proteins, and where is it located?
pepsin –> stomach
what enzymes from the pancreas digest proteins? (ie 4 in your slides)
which of those enzymes are zymogens?
trypsin
chymotrypsin
elastase
carboxypeptidase
elastase is a zymogen
- trypsinogen –> trypsin
- chymotrypsinogen –> chymotrypsin
- procarboxypeptidase –> carboxypeptidase
what 3 brush border enzymes digest proteins?
carboxypeptidase
aminopeptidase
dipeptidase
what is the function of dipeptidase?
split dipeptides into separate aas
what is contact digestion?
food/chyme comes in contact with brush border enzymes in small intestine
(carboxypeptidase, aminopeptidase, dipeptidases)
where are the brush border enzymes located? (structure and cells)
microvilli on the surface of enterocytes of the small intestine
what is nitrogen balance?
state in which:
rate of N ingestion = rate of N excretion
how do you get nitrogen for your body? (type of nutrient)
dietary proteins
what happens when you have too little nitrogen in your body (state of negative nitrogen balance)?
muscle atrophy (muscle proteins are more easily broken down than others)
if carb and fat intake are insufficient to meet the need for energy – protein catabolism
- proteins are broken down to be used as fuel
greater nitrogenous waste in urine that gets excreted
what can cause a state of negative nitrogen balance?
insufficient carb and fat intake –> can’t meet need for energy –> protein catabolism (proteins are broken down to be used as fuel)
why is positive nitrogen balance associated w/ periods of growth?
ingesting more nitrogen than excreted == ingesting more protein == more protein is retained for tissue growth
what 3 steps comprise the amino acid catabolic pathway?
1) transamination
- amine group is switched from an amino acid to a keto acid
2) oxidative deamination
- amine group of glutamic acid is removed as ammonia and combined w/ CO2 to form urea
3) keto acid modification
- keto acids formed during transamination are altered so they can easily enter the citric acid cycle
how does the body get rid of the amine group of the amino acids?
what is the name of that reaction?
transamination:
amine group is transferred from amino acid to a-ketoglutaric acid –> transforms a-ketoglutaric acid to glutamic acid
original aa becomes a-keto acid
how is urea produced in the body?
oxidative deamination:
amine group of glutamic acid is removed as ammonia and combined with CO2 to form urea
what happens during the keto acid modification? what is the goal of this reaction? (tip: enter to 1 pathway)
keto acids formed during transamination are altered –> so they can easily enter the citric acid cycle
can you obtain energy from proteins?
yes
amino acids have to be converted to keto acids that are then modified to enter the citric acid cycle to synthesize ATP
what is the name of this functional group: –NH2?
amine
what is transamination?
de-aminate an amino acid by taking off its amine group and transferring it over to a-ketoglutaric acid
a-ketoglutarate then becomes glutamate
original amino acid now becomes alpha-keto acid
this newly formed a-keto acid can now be modified or converted to pyruvate, acetyl-CoA, or an acid to enter the citric acid cycle
deaminated aas can also be converted to fatty acids and glucose
during transamination, an amine group is transferred from an amino acid to which molecule?
after this process, what is the name of the molecule comprising the remaining structure of the amino acid (ie without the amino group)?
amine group is transferred from aa to a-ketoglutarate (aka a-ketoglutaric acid)
amino acid w/o the amine group is now an a-keto acid
