Shared Flashcard Set


CHAPTER 17 (food)
Undergraduate 3

Additional Chemistry Flashcards




main food classes

for proper nutrition, our diet should include balanced proportions of these groups, plus water, vitamins, minerals, and fiber
dietary carbohydrates include sugars and starches

sugars are mainly monosaccharides and disaccharides
starches are polysaccharides

glucose is broken down to release energy and products of CO2 and water (the REVERSE of photosynthesis)

carbs are our bodies' preferred fuels, releasing 4kcal of energy per gram
when we eat more than we can use, small amounts of carbohydrates can be stored in the liver and muscle tissue as GLYCOGEN, but large excesses are converted to fat
the sugar (made from plants via photosynthesis) used by the cells of our bodies for energy

it is often called BLOOD SUGAR as it is the sugar that circulates in the bloodstream

FRUCTOSE is sweeter than sucrose or glucose
digestion & metabolism of carbohydrates
glucose and fructose are absorbed directly into the bloodstream from the digestive tract

SUCROSE is hydrolyzed (split using water) during digestion to GLUCOSE and FRUCTOSE

the disaccharide LACTOSE occurs in dairy and is hydrolyzed to GLUCOSE and GALACTOSE

lactose intolerance comes from adult people lacking the enzyme to accomplish the breakdown of lactose

some babies lack the ability to break down galactose into glucose and have GALACTOSEMIA, and have to have special a synthetic formula instead of milk

complex carbohydrates
starch and cellulose are polymers of glucose but with different links between each glucose unit - humans cannot break the link in cellulose (BETA LINKAGES) but they can in starch (ALPHA LINKAGES)

cellulose however is an important component of DIETARY FIBER - pushing things out of our systems

starch is hydrolyzed to glucose

cellulose CANNOT be digested by humans or other meat-eating animals
esters of fatty acids and glycerol
high energy foods, yielding 9kcal energy per gram
some fats are burned as fuel, some are used to build and maintain parts of our cells
the common name for dietary fats
digested by enzymes called lipases, ultimately forming fatty acids and glycerol
fat deposits
stored throughout the body, principally in ADIPOSE tissue, around vital organs such as the heart, kidneys, and spleen, as cushioning, and under the skin to improve insulation
dietary saturated fats and health
together with cholesterol have been implicated in ARTERIOSCLEROSIS - hardening of the arteries and cardiovascular disease

blood clots tend do lodge in narrowed arteries, leading to a heart attack if the blocked artery is in the heart muscle or stroke if the blockage occurs in an artery that supplies the brain

the plaque in clogged arteries is rich in cholesterol (a fatlike steroid alcohol found in animal tissue and various foods) - normally synthesized by the liver and an important constituent of cell membranes and other hormones

exercise increases levels of high-density lipoproteins (HDL) ("good" cholesterol)
high levels of low-density lipoproteins (LDL) increase risk of blockage

oils have high percentage of monounsaturated fatty acids, proven to lower LDL levels

trans fatty acids can stack together like logs and are more likely to be solids (raising LDL levels)
cis fatty acids keep apart and are more likely to be liquid

it is recommended that fat should not exceed 30% of our daily caloric intake, and no more than 1/3 of that should be saturated fats
polymers of amino acids, responsible for serving a specific purpose and encoded for in genes

broken down into their constituent amino acids in the digestive tract

from these amino acids our bodies synthesize proteins for growth and repair of tissues, excess proteins are used for energy

there are 9 amino acids our bodies cannot synthesize needed to make proteins - called ESSENTIAL AMINO ACIDS (isoleucine, lysine, phylalanine, tryptophan, leucine, methionine, threonine, and valine)

these 9 essential amino acids must be included in our diet somewhere - each essential amino acid is a LIMITING REACTANT in protein synthesis

an "adequate" or "complete" protein source supplies all 9 essentials (lean meat, milk, fish, eggs, cheese)

but most plant proteins are DEFICIENT in one or more amino acid

our requirement is about .8 g of protein per kg of bodyweight - diets with inadequate protein supply may lead to KWASHIORKOR (a protein-deficiency disease, symptoms are bloating of the belly, discoloration of skin, etc.)
vegetarian diets and proteins
vegetarian diets are in many ways more efficient as animal production is costly and wasteful and inefficient - thus, it conserves energy

but it is easy to have protein deficiencies as plant proteins usually lack at least one of the nine essential amino acids

an ovolacto diet (including eggs and milk) can provide excellent nutrition
around the world diets combining a CEREAL GRAIN with a LEGUME supply good protein - like corn tortillas and beans, rice and tofu, etc.)
dietary minerals
they are essential to life, but not one of the main food groups

minerals serve a variety of functions
ex. iodine is necessary for proper thyroid function, iron II ions are necessary for proper function of hemoglobin in the blood (a lack results in anemia), calcium for bones and teeth, salt is essential to transferring of fluids
specific organic compounds that are required in the diet to prevent specific diseases
there are 2 broad categories of vitamins - fat (only slightly polar) and water (very electronegative / polar) soluble

fat soluble vitamins dissolve in the fatty tissue of the body, where reserves can be stored for future use

the body has a limited ability to store water-soluble vitamins, most are excreted when they cannot be used immediately

scurvy - lack of vitamin C
2 things important to life but not (carbs, proteins, fats, minerals, vitamins...)

dietary fiber can be soluble (gums and pectins) or insoluble (cellulose)
high fiber diets prevent constipation
fiber has no calories as the body does not absorb it
fiber takes up space in the stomach, making us feel full and eat less
soluble fiber lowers cholesterol levels and control blood sugar

much of the food we eat is mainly water
in addition to our foods we must drink 1 to 1.5 L a day
condition where the human body is totally deprived of food
the body's glycogen stores are depleted in less than a day and the body calls on fat reserves
increased dependence on stored fats as an energy source leads to KETOSIS (appearance of ketone bodies in the blood and urine) which rapidly develops into ACIDOSIS (the blood pH drops and oxygen transport is hindered, leading to depression and lethargy - also associated with diabetes)

insulin allows the body's cells to take up glucose from the bloodstream - lacking in it causes the liver to act as though cells are starving, and they burn fat for energy while blood sugar levels rise, leading to production of ketone bodies and acidosis

the body then draws on body protein, leading to an emaciated look
processed foods
malnutrition may be the result of eating too much highly processed food

foods loose vitamins and minerals and fiber through peeling, cooking (water soluble vitamins escape in the water), etc.

estimated 90% of the American family food budget goes to processed foods - leading to malnutrition and obesity
food additives
EVERYTHING ADDED TO FOOD IN THE UNITED STATES - a list on the FDA's website listing more than 3000 substances that are added to our foods

can increase nutritional value, replace nutrition where it has been processed out, increase shelf-life of an item, improve texture, taste, odor, sanitize, control moisture levels, or control foaming

most common: sugar, salt, corn syrup
then: citric acid, baking soda, vegetable colors, mustard, and pepper
^^ all together make up 98% by weight of additives ^^

potassium iodide (KI) was added to table salt in 1924 to reduce incidence of goiter
vitamin B1 (thiamine) added to polished rice to prevent beriberi disease in far East
ENRICHMENT to flour is adding back the B vitamins thiamine, riboflavin, folic acid, and niacin and adding iron that is all processed out
to retard spoilage
antimicrobials - to prevent the growth of molds, yeasts or bacteria

sodium nitrite is used in meat curing
some additives are potent carcinogens
preservatives include sulfur dioxide for dried fruits
one class of preservatives that inhibit the chemical spoilage of food that occurs in the presence of oxygen - added to food or packaging to prevent fats and oils from forming rancid products that make food unpalatable, and minimize the destruction of some essential amino acids and vitamins

fat turns rancid as a result of oxidation via free radicals and chain reactions
chemical additives stop the chain reaction by reacting with free radicals to form stable compounds - BHT
bruised celery produces powerful mutagens and carcinogens called psoralens

the toxin botulin is produced by bacteria growing in improperly canned food - 1g of it could kill more than a million people

aflatoxins are potent carcinogens produced by molds growing on stored peanuts and grains
Supporting users have an ad free experience!