BIOL 204 Exam 4

what is nutrition?

the process of providing or obtaining the food necessary for health and growth

what is digestion?

it is the catabolic process that breaks down large food molecules to monomers (chemical building blocks)

what is hydrolysis?

the enzymatic breakdown of any food molecule; it involves adding a water molecule to each molecular bond to be broken (lysed)

what are the monomers of carbohydrates, proteins, lipids, and nucleic acids?

monosaccharides; amino acids; fatty acids; nucleotides

what is absorption?

the process of moving substances from the lumen of the gut into the body

what is metabolism?

the sum of all biochemical reactions in the body

what is the main difference between catabolism and anabolism?

anabolism includes reactions that build larger molecules from smaller ones and catabolism is the breakdown of complex structures to simpler ones

what is a nutrient?

a substance in food the body uses to promote normal 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 six nutrient categories?

carbohydrates, protein, fats, water, vitamins, and minerals

what are the four macronutrients?

carbohydrates, protein, fats, and water

what are the two micronutrients?

vitamins and minerals

what is the difference between macronutrients and micronutrients?

macronutrients must be consumed in relatively large quantities and micronutrients require small quantities of consumption

what is meant by percent of daily caloric intake?

the 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

what are calories?

the amount of heat (energy) needed to raise the temperature of 1 gram of water 1 degree Celsius

what is the difference between calories, Calories, and kilocalories?

1000 calories = 1 Calorie = 1 kilocalorie

what do Calories represent?

the ability of food to be converted by the body into energy

what are the three energy-yielding nutrients?

carbohydrates, proteins, and fat

how many calories are produced when one gram of carbohydrates, fats, and proteins are fully oxidized in our body?

carbohydrates/ 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

why is alcohol not a class of nutrients despite is high-calorie content?

alcohol provides “empty calories”- it suppresses 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

fat soluble: A,D,E,K

which of the two vitamin groups, water-soluble or lipid-soluble, has a higher risk of accumulating in your body until reaching toxic levels? Why?

fat-soluble vitamins because they are stored in the body

How are water-soluble vitamins absorbed and excreted from the body?

water-soluble vitamins are absorbed with water by simple diffusion and excreted in urine

how is vitamin B12 absorbed from the intestines?

vitamin B12 binds to the intrinsic factor, which is secreted by the stomach’s parietal cells

Is ferrous (Fe2+) iron or ferric (Fe3+) iron more absorbable?

ferrous (Fe2+) iron

what is the function of ferroportin (FPN)?

FPN transports iron into the bloodstream

where can you find ferroportin?

basolateral membranes of intestinal epithelia

what is the function of transferrin?

transports iron all over the body

what happens to iron released by macrophage degradation of senescent red blood cells?

it is recycled

why does transferrin transport iron to bones and muscles?

myoglobin synthesis

what is ferritin?

iron storage protein

which organ represents the primary storage site for iron?

the liver

what is hepcidin? what is its main goal, increase or decreased blood levels of iron? How does it achieve this?

iron absorption and mobilization are regulated by hepcidin; it decreases blood levels of iron by binding to ferroportin

will an increase in blood iron increase or decrease the production of hepcidin by the liver?

increase

will an increase in red blood cells increase or decrease the hepcidin production by the liver?

decrease

In which two main organs does digestion of carbohydrates take place?

oral cavity and small intestine

where does the digestion of carbohydrates start?

in the oral cavity

what is a polysaccharide?

polymer of carbohydrates

what enzyme is in saliva that digests polysaccharides?

salivary amylase

why does the digestion of carbohydrates not continue in your stomach if the bolus from your mouth also carries some salivary amylase?

the acidic pH of the stomach inactivates amylase

where does the amylase in your small intestine come from?

the pancreas

which two brush border enzymes act on oligosaccharides composed of more than three simple sugars?

dextrinase and glucoamylase

what are disaccharides? give three examples.

disaccharides are two units of carbohydrates; maltose, sucrose, and lactose

where can you find disaccharides in the digestive system?

in the small intestine

where are monosaccharides absorbed?

small intestine

are monosaccharides absorbed into the blood or lymph?

blood

what is the primary purpose of cellular respiration?

generate ATP in the presence of oxygen

what is the equation for aerobic respiration of glucose?

C6H12O6 + 6O2 → 6CO2 + 6H2O

what are the three consecutive pathways of glucose aerobic respiration?

glycolysis, citric acid cycle, and electron transport chain

what is the role of ATP?

energy carrying molecule that releases to fuel cell processes

what is the role of NAD or FAD?

coenzymes that carry the extracted energy

what molecules are the starting and end products of glycolysis?

converts glucose to pyruvic acid

How is energy stored in the body?

energy is stored at carbohydrates and fats and converted into ATP when energy is needed

how many pyruvates are obtained per molecule of glucose being oxidized in glycolysis?

two pyruvates

what pathway does pyruvic acid enter in the absence of oxygen? and in the presence of oxygen?

in the absence of oxygen: pyruvate processing (pyruvic acid to lactic acid)

presence of oxygen: citric acid cycle

what is pyruvate converted into 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/ oxidative phosphorylation

what ion gradient is used to make ATP?

H+ (proton) gradient

what is glycolysis?

conversion of glucose to pyruvic acid

what is gluconeogenesis?

formation of glucose from noncarbohydrate precursors

what is glycogenesis, and when does it occur?

polymerization of glucose to form glycogen; occurs when cellular ATP reserves are high

what is glycogenolysis, and when does it occur?

hydrolyzation of glycogen to glucose monomers; occurs when blood glucose levels begin to fall

what is the general name of enzymes that act on proteins?

peptidases

what enzyme begins the digestion of proteins and where is it located?

pepsin; stomach

what enzymes from the pancreas digest protein? which are zymogens?

trypsin, chymotrypsin, carboxypeptidase (zymogens) and elastase

what three brush border enzymes digest proteins?

carboxypeptidase, aminopeptidase, and dipeptidase

what is the function of dipeptidase?

split dipeptides into separate amino acids

what is contact digestion?

action of brush border enzymes

where are brush border enzymes located?

small intestine (simple cuboidal epithelium?)

what is nitrogen balance?

state in which the rate of N ingestion = rate of N excretion

how do you get nitrogen for your body?

via proteins

what happens when you have too little nitrogen in your body (state of negative nitrogen balance)?

increase of nitrogenous wastes in urine; muscle atrophy; protein catabolism

what can cause a state of negative nitrogen balance?

nitrogen excretion>ingestion

what is positive nitrogen balance associated with?

periods of growth (during adolescence and pregnancy)

what three steps comprise the amino acid catabolic pathway?

transamination, oxidative deamination, keto acid modification

how does the body get rid of the amino group of amino acids?

transamination; the amino group is switched from an amino acid to a keto acid (glutamic acid)

how is urea produced in the body?

oxidative deamination; the amine group of glutamic acid is removed as ammonia and combined with CO2 to form urea

what happens during keto acid modification?

the keto acids formed during transamination are altered so they can easily enter the citric acid cycle

can you obtain energy from proteins?

yes; 4 kcal/ g

what is the name of this functional group: -NH2?

amine group

what is bile made of?

95% water

5% solute

* bile acids
* lecithin
* cholesterol
* bilirubin
* proteins

what is the main component of bile?

water

what are bile salts made of?

bile acids that are often bonded to glycine or taurine to increase water solubility (= conjugated bile acids)

what is the role of bile salts in the digestive process

increase water solubility

where is bile produced? from which molecule?

produced in the liver from cholesterol

what are conjugated bile salts?

bile acids bonded to glycine or taurine

what is the only way for the body to get rid of cholesterol?

in feces

what percentage of bile salts are lost in the feces?

20%

in what part of the intestine are bile salts recycled?

the ileum

what is the role of emulsification?

bile salts in the duodenum break large fat globules into smaller fat droplets: increases surface area available to lipase enzymes

what are miscelles?

aggregates of bile salts that forms a polar outer shell and a hydrophobic inner core

what are triglycerides composed of?

three fatty acids and a glycerol

which enzyme is mainly responsible for digesting triglycerides in the small intestine?

pancreatic lipase

what is the function of micelles in the absorption of lipids?

since micelles are water-soluble, this allows for lipid digestion products to be transported into the small intestine

why do lipids need to be transported in the core of the micelles to to enter the enterocytes?

lipids are not water-soluble and micelles are

what happens to the fatty acids and monoglycerides once inside of the enterocytes?

the fatty acids and monoglycerides are converted into triglycerides