Nutrition Exam 3: ch. 8,9,10,11,13

energy

in living organisms, power derived from sunlight or food to perform cellular work

-can neither be created nor destroyed

-can undergo transformations

ex: body cells take emergy stored in food and convert it into a usable form of energy

cellular work

activities in cells requiring energy, such as building and transporting molecules

chemical pathways

specific chemical reactions that occur in sequences

-used to access and use energy stored in “biological fuels”

energy metabolism

is the sum of all the chemical pathways in the body that break down molecules to release energy and use energy to build new molecules

catabolism

metabolic pathways that break down larger molecules into smaller ones

anabolism

metabolic pathways that build larger molecules from smaller ones

-requires energy, supplied by catabolic reactions

coenzymes

group of organic compounds that assist enzymes with chemical reactions

-many b vitamins serve as coenzymes or are components of coenzymes

nicotinamide adenine dinucleotide (NAD+)

niacin-containing coenzyme

flavin adenine dinucleotide (FAD)

riboflavin-containing coenzyme

adenosine triphosphate (ATP)

a high-energy phosphate compound that serves as energy “currency” of cells

adenosine diphosphate (ADP)

the molecule that forms when ATP loses its last phosphate group during ATP catabolism

phosphorylation

an anabolic reaction that attaches a phosphate (Pi) group to ADP

mitochondria

organelles that synthesize most of the ATP that cells need to function

-have an outer membrane and an inner membrane

aerobic metabolism

metabolic pathways for ATP production that require oxygen

-occurs in mitochondria if the cell’s oxygen supply is adequate

anaerobic metabolism

metabolic pathways for ATP production that do not require oxygen

-much less energy is made under low-oxygen conditions

glycolysis

the first phase of glucose catabolism, the splitting of the glucose molecule, leads to ATP production

occurs in cytoplasm

glucose is broken down to two molecules of pyruvate, a 3-carbon molecule

two NADH and four ATP molecules are formed; two ATP molecules are used, so there is a net gain of two

aerobic conditions

when plenty of oxygen is available, pyruvate enters mitochondria

converted to acetyl coenzyme A (acetyl CoA), a 2-carbon molecule

two molecules of acetyl CoA formed from one molecule of glucose

under anaerobic conditions, pyruvate is converted to lactic acid, another 3-carbon molecule

fate of pyruvate in anaerobic metabolism

1. in anaerobic conditions, muscle cells rapidly metabolize glucose to lactic acid and then to lactate

2. lactate enters the bloodstream

3. (A) the liver can remove lactate from blood, convert it into glucose (via Cori cycle), and release the simple sugar into the bloodstream if the fuel is needed

3. (B) certain cells can remove lactate from the bloodstream and metabolize it for energy

4. if the body does not need the energy, the liver converts glucose to glycogen

citric acid cycle

complex series of chemical reactions that are involved in energy metabolism

-oxaloacetate

oxaloaxetate

four-carbon molecule that is an important intermediate of the citric acid cycle

electron transport chain

linked series of enzymes that synthesize water and ATP during aerobic energy metabolism

-cytochrome c

cytochrome c

a component of the electron transport chain; facilitates the bonding of hydrogen ions with oxygen, forming '“metabolic water”

hormone-sensitive lipase (HSL)

enzyme in fat cells (adipocytes) that removes the three fatty acids from a triglyceride

carnitine

a molecule that helps fatty acids enter the mitochondria

beta-oxidation

chemical pathway involved in the catabolism of a fatty acid

ketogenesis

ketone body formation

ketogenic diet

high-fat, moderate- to low-protein, and very-low-carbohydrate diet

ketoacidosis

condition that occurs in the absence of insulin when excess acetoacetate and beta-hydroxybutyrate in the bloodstream lower in the blood’s pH

Summary of fat catabolism

1. hormone-sensitive lipase facilitates removal of fatty acids form triglycerides. albumin transports fatty acids in the bloodstream and releases them for uptake into cells, particularly muscle cells

2. fatty acid binds to coenzyme A. the activated fatty acids enter the mitochondria with the help of carnitine

3. fatty acids are catabolized by beta-oxidation

4. acetyl CoA molecules enter the citric acid cycle and are catabolized

5. carriers transport electrons to electron transport chain, and ATP synthesis occurs

summary of using amino acids for energy

the amount of ATP formed by the catabolism of an amino acid carbon skeleton depends on where it entered the catabolism pathways

vitamin

a complex organic compound that regulates certain metabolic processes, and meets certain criteria:

-cannot be synthesized by the body or make enough to maintain good health

-occurs naturally in foods

-deficiency disorder occurs if substances is missing from the body or is not properly metabolized

-health is restored by supplying missing substance

fat-soluble vitamins

vitamins that are hydrophobic and found in the lipid portions of food; vitamins A, D, E, and K

-associate with lipids in the body

-digested and absorbed with fats

-stored in the body, primarily in liver and adipose tissue

-can accumulate and cause toxicity

water-soluble vitamins

vitamins that are hydrophilic and found in the watery portion of food; thiamin, riboflavin, niacin, vitamin B-6, pantothenic acid, folate, biotin, vitamin B-12, and vitamin C

-dissolve in watery components of body

-limited amounts are stored (exception is vitamin B-12)

-kidneys filter excess and eliminate them in urine

-less likely to be toxic

-the vitamin-like compounds choline, carnitine, and lipoic acid are also water soluble

roles of vitamins

-some act as hormones

-some participate in chemical reactions by accepting or donating electrons

-vitamins regulate various body processes, including cell division, development, and growth

-most have more than one chemical form that functions in the body

-some have precursors (provitamins or previtamins) that do not function as vitamins until the body converts them into active forms

oxidizing agent (oxidant)

substance that removes electrons from atoms or molecules

-an atom or a molecule that loses one or more electrons has been oxidized

free radical

substance with an unpaired electron

-generated from oxidation reaction

-highly reactive and unstable

-can remove electrons from stable molecules such as proteins, fatty acids and DNA, damaging them; if uncontrolled, a chain reaction can occur in which excessive oxidation takes place and affects many cells

antioxidant

substance that gives up electrons to free radicals to protect cells

-protects molecules in cells, such as polyunsaturated fatty acids and DNA, from being oxidized

functions of vitamins and vitamin-like compounds

bone health: vitamin A, D, K, C

energy metabolism: thiamin, riboflavin, niacin, pantothenic acid, biotin, vitamin b-12 and b-6

blood clotting: vitamin K

amino acid metabolism: vitamin b-6 and b-12, folate, vitamin c, choline

antioxidant defense: vitamin E, vitamin C (likely), certain carotenoids

immune function: vitamine A, C, D, E

red blood cell formation: vitamin b-6 and b-12, folate, riboflavin (indirect)

growth and development: vitamin A, D, choline

biological activity

a vitamin’s degree of potency or effects in the body

-may differ between natural and synthetic vitamins

multivitamin-multimineral supplement

supplement that contains two or more vitamins and minerals

bioavailability

extent to which the digestive tract absorbs a nutrient and how well the body uses it

factors that affect bioavailability include:

-life-stage and nutrient status of individual

-changes to GI transit time

-health conditions affection absorption of fats

-food processing and preparation techniques

-source of vitamin

retinoids (preformed vitamin A)

family of compounds commonly called vitamin A (retinol, retinal, retinoic acid)

retinol

alcohol form of vitamin A and the most active form of vitamin A in the body

retinyl esters

storage form of vitamin A

carotenoids

yellow-orange pigments in fruits and vegetables

beta-carotene

carotenoid that the body can convert to vitamin A

-alpha-carotene and beta-cryptoxanthin can also be converted into a biologically active retinoid

epithelial cells

cells that form protective tissues that line the body

retinol-binding protein (RBP)

transports vitamin A in the blood

xerophthalmia

is a condition affecting the eyes that results from a vitamin A deficiency

-eventually leads to blindness

teratogen

an agent that causes birth defects

carotenemia

yellowing of the skin that results from excess beta-carotene in the body

-harmless

age-related macular degeneration (AMD)

eye disease resulting in changes, in the macula of the eye, causing distorted vision

rickets

vitamin D deficiency disorder in children resulting in improper bone growth

-bones are soft and can become malformed

-can be prevented and treated by sunlight exposure, vitamin D supplements, and vitamin D-rich foods

ergocalciferol

form of vitamin D found in plant food sources; vitamin D2

cholecalciferol

form of vitamin D found in animal food sources; vitamin D3

7-dehydrocholesterol

precursor for vitamin D found in skin

-UV light converts it to cholecalciferol, which circulates to the liver; vitamin D is thus not considered an essential nutrient

25-hydroxyvitamin D (calcidiol)

inactive form of vitamin D, made in the liver from cholecalciferol

1,25-dihydroxyvitamin D (calcitriol)

most biologically active form of vitamin D

-made in the kidneys from calcidiol

parathyroid hormone (PTH)

hormone secreted in response to low blood calcium levels

-signals bones to release calcium, and stimulates kidneys to increase vitamin D production and decrease calcium elimination in urine

osteomalacia

a condition characterized by softening of the bones as a result of inadequate vitamin D status in adults

-adults who are confined indoors or almost fully covered when outside are at risk

tocopherols

a group of four structurally similar forms of vitamin E

alpha-tocopherol

form of vitamin E used by the body; found in most foods and vitamin E supplements

gamma-tocopherol

form of vitamin E that has significantly lower biological activity than alpha-tocopherol

-also found in foods

phylloquinone

vitamin K1, found in plants

menaquinone

vitamin K2, found in animal and fermented foods

menadione

synthetic form of vitamin K

-can be converted into menaquinone in the body

vitamin K and blood clotting

1. liver needs vitamin K1 to make certain clotting factors

2. normal conditions (inactive clotting factors and inactive platelets)

3. injury to blood vessel; tissues exposed

4. inactive platelets and inactive clotting factors in the blood activated

5. prothrombin > thrombin

6. fibrinogen > fibrin (clot)

cystic fibrosis

an inherited respiratory disease caused by a defective gene that leads to overproduction of thick and sticky mucus

-it negatively affects the lungs, pancreas, liver, intestines, sinuses, and sex organs

-left untreated, children with cystic fibrosis usually experience delayed growth and malnutrition

water-soluble vitamins

dissolve in watery components of food and the body

-excesses of water-soluble vitamins are filtered through the kidneys and eliminated in the urine

thiamin (or vitamin b-1)

the vitamin component of a coenzyme that is important for energy metabolism as part of thiamin pyrophosphate (TPP)

-necessary for the breakdown of carbohydrates to release energy and for the metabolism of branched-chain amino acids

-necessary for the synthesis of neurotransmitters

no UL has been established (rare because excess is readily excreted in urine)

neurotransmitters

chemicals produced by nerve cells that enable the cells to communicate with other nerve cells

Beriberi

the thiamin deficiency disease characterized by weakness, poor muscular coordination, and abnormal functioning of the cardiovascular, digestive, and nervous systems

Wernicke-korsakoff syndrome

-a degenerative brain disorder associated with a deficiency of thiamin

-most commonly caused by excessive alcohol consumption

-symptoms include abnormal eye movements, staggering gait, and distorted thought process

riboflavin (or vitamin b-2)

important for energy metabolism as part of flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD)

-the two coenzymes play key roles in enzymatic reactions, including those that are critical to fatty acid and folate metabolism

-the liver, kidneys, and heart store small amounts of riboflavin: any excess intake is rapidly excreted in the urine (no UL)

ariboflavinosis

a riboflavin deficiency disease characterized by fatigue, inflammation of the mucous membranes that line the mouth and throat, and glossitis

glossitis

refers to a swollen and sore tongue

cheilosis

scaling and cracking of the skin around the corners of the mouth

niacin (or vitamin b-3)

important for energy metabolism as part of nicotinamide adenine dinucleotide (NAD) and nicotinamide adenine dinucleotide phosphate (NADP) coenzymes

-niacin coenzymes participate in at least 200 reactions, including pathways involved in the release of energy from macronutrients

Ul is 35 mg/day

pellagra

the niacin deficiency disease characterized by dermatitis, diarrhea, dementia, and death

-the “4 D’s of pellagra”

pantothenic acid

a vitamin component of coenzyme A (CoA)

-helps release energy from carbohydrates, fat, and protein

-necessary for fatty acid synthesis

no UL

biotin

the vitamin component of a coenzyme that participates in chemical reactions that add carbon dioxide to other compounds

-promotes the synthesis of glucose and fatty acids and the breakdown of certain amino acids

-essential for regenerating oxaloacetate in the TCA cycle

no UL

avidin

a protein found in raw egg whites that binds biotin, thus preventing absorption of the vitamin

vitamin b-6

a vitamin component of the coenzyme pyridoxal phosphate (PLP); important for energy metabolism, particularly protein metabolism

-PLP facilitates enzymatic reactions involved in amino acid metabolism; conversion of tryptophan to niacin; transamination reactions that form nonessential amino acids

PLP helps reduce heme, a component of hemoglobin

UL is 100 mg/day

hemoglobin

the iron-containing protein in red blood cells (RBCs) that transports oxygen; if vitamin b-6 is unavailable, anemia can develop

peripheral neuropathy

a condition characterized by severe sensory nerve damage

-can be caused by megadoses of vitamin b-6

folate

b vitamin that is a component of the coenzyme tetrahydrofolate (THF), and is important for energy metabolism, DNA synthesis, and homocysteine metabolism

Ul for synthetic form (folic acid) is 1,000 ug/day

megaloblastic anemia

a type of anemia characterized by large, immature RBCs; a deficiency of folate and/or vitamin b-12 can lead to this form of anemia

neural tube

an embryonic structure that eventually develops into the brain and spinal cord

-pregnant women who are deficient in folate increase the risk of their infant being born with neural tube defects (NTDs)

spina bifida

type of neural tube defect in which the spine does not form properly before birth and fails to enclose the spinal cord

anencephaly

type of neural tube defect in which much of the brain does not form properly or is missing

-can result from genetic causes and from folate deficiency

vitamin b-12 (or cobalamin)

the vitamin that is a component of coenzymes that participate in a variety of cellular processes, including transfer of CH3 groups in the metabolism of folate

-also needed for homocysteine metabolism and folate conversion to coenzymes involved in metabolic reactions, such as DNA synthesis

myelin sheath

a structure that wraps around and insulates a part of a certain nerve cell cells

-vitamin b-12 is needed for maintenance of this structure, which is needed for nervy communication

food-cobalamin malabsorption

malabsorption of vitamin b-12 due to the inability to release the vitamin from animal protein during the digestive process

gastritis

inflammation of the stomach lining

pernicious (“deadly”) anemia

a condition caused by lack of intrinsic factor and characterized by vitamin b-12 deficiency, nerve damage, and megaloblastic red blood cells

scurvy

a vitamin C deficiency disease

-deathly disease first associated with lengthy ocean voyages

vitamin C (or ascorbic acid)

a cofactor that performs a variety of important cellular functions, primarily by donating electrons to other compounds

UL is 2,000 mg/day

collagen

is a fibrous protein that gives strength to connective tissue such as bone, cartilage, and tendons

prooxidant

a substance that promotes production of free radicals

vitamin-like compounds

substances that maintain normal metabolism but are not essential since the body can synthesize them. EX: choline, carnitine, inositol, taurine, and lipoic acid