Cns Primer Sections 1 E,f,g,h

Front 1

Food substitutes and additives that are used commonly may be natural or synthetic, nutritive ornon-nutritive, physiologically active or inert chemicals added directly or indirectly to foods.

Name some types of direct additives.

Back 1

Potential direct additives include antioxidants, antispoilage agents (preservatives), vitamins,minerals, flavoring agents, colorings, emulsifiers, stabilizers, binders, bleaching agents,acidifiers, nutritive and non-nutritive sweeteners, fat replacers and leavening agents. Additivescan be added indirectly as contaminants of food processing or packaging.

Front 2

Several artificial sweeteners are available such as ... can you name 3?

Back 2

1. Acesulfame is a derivative of acetoacetic acid;large doses may raise cholesterol

2. Aspartamecontains 2 amino acids (aspartic acid and phenylalanine) plus methanol (wood alcohol); risk for individuals with phenylketonuria

3. Saccharine combines dextrose withaspartame; large doses associated with bladdercancer.

Front 3

The several available fat replacers differ in the materials from which they are derived.

Avicel is a _______ derivative.

Olestra is an unabsorbable _____ derivative.

Simplesseis a derivative of processed (microparticulated) ________proteins.

Back 3

Avicel is a carbohydrate derivative.

Olestra is an unabsorbable lipid derivative.

Simplesse is a derivative of processed (microparticulated) milk and egg proteins.

Front 4

Preservatives are chemicals added to foodproducts to prevent spoilage and increase shelf-life and may include antioxidant nutrients such as__________.

Back 4

Vitamin E

Front 5

Colorings may be natural orartificial compounds. Can you name a few examples of natural colorings?

Back 5

natural (e.g., beta-carotene, tumeric, saffron, plant dyes)

Front 6

________ are chemicals used to suspend oily material in water.

Back 6

Emulsifiers

Front 7

Stabilizers are used as thickening agents - can you name some examples?

Back 7

(e.g., carrageenan, dextrin, lecithin, xanthan gum).

Front 8

________ are used to hold food constituents together and are especially important in theformulation of dietary supplements.

Back 8

Binders

Front 9

________is the addition of nutrients to foods without adding back nutrients lost during theprocessing of those foods. The added nutrient may or may not be present in the original food andcan be added in amounts greater than those originally present.

Back 9

Fortification

Front 10

________is the addition of oneor more nutrients to one or more commonly consumed foods or food mixtures in order toimprove the dietary intake of a given target population. It makes a food morenutritious.

Back 10

Nutrification

Front 11

___________is the addition of nutrients to the diet.

Back 11

Supplementation is the addition of nutrients to the diet.

Front 12

Nutrification is the:

a. addition of a nutrient to a food in order to assure the distribution of that nutrientto a target population group.

b. specific addition of thiamin, riboflavin, niacin, and iron to white flour.

c. structural modification of complex carbohydrates.

d. addition of at least 25% of the RDA of a nutrient to a food productthat has been designed to replace a meal or food item.

Back 12

a. addition of a nutrient to a food in order to assure the distribution of that nutrient to a target population group.

Front 13

__________ are proteins whose function is to bind substrates and catalyze their conversion toreaction products differing from the substrates in chemical structure and composition byreducing the reaction's required Energy of Activation (Eac).

Back 13

Enzymes

Front 14

True or False?

Enzyme catalysts return totheir original state when the reaction is completed, so enzymes are not consumed by the reactionsthey catalyze and small numbers of enzymes can produce large amounts of products.

Back 14

TRUE

Front 15

A ______ is an organic compound required by an enzyme in order for the enzyme to beable to reduce the required Eac of a reaction.

Back 15

coenzyme

Unlike an enzyme, a coenzymeparticipates in the reaction by either transferring to the reactants an electron, reducedproton, phosphate, hydroxyl or methyl group or by accepting such a substance from thereactants, and must be regenerated.

Examples: NADPH; N-5-methyltetrahydrofolate

Front 16

A ______ is a nutrient that is required by an enzyme for full activation of the enzyme.

Back 16

cofactor

Unlike acoenzyme, a cofactor functions as part of the enzyme and is not consumed by the reaction.Examples of common cofactors are zinc, magnesium and copper.

Front 17

Coenzyme A is derived from:

a. Pantothenic acid

b. Pyrodoxine

c. Cobalamin

d. Tetrahydrobiopterin

Back 17

a. Pantothenic acid

Front 18

__________ is the hydrolysis of glycogen in the liver and muscle to glucose monomers.

Back 18

Glycogenolysis

lysis - breakdown

glycogen(n glucosyl units)+inorganic phosphate (Pi) glycogen phosphorylase→D-glucose 1-P+glycogen((n-1) glucosyl units)

Front 19

________ is the pathway during which glycogen polymers are created fromglucose monomers.

Back 19

Glycogenesis

hexokinase: glucose + ATP → glucose 6-P + ADP

phosphoglucomutase: glucose 6-P → glucose 1-P

UDP-glucose pyrophosphorylase: glucose 1-P + UTP → UDP-glucose + PPi

glycogen synthase: UDP-glucose + (glucose)n → UDP + (glucose)n+1

Front 20

_______ is the energy-producing conversion of 6-carbon glucose to 3-carbonpyruvate; it is considered an anaerobic process because oxygen is not involved.

Back 20

Glycolysis

hexokinase*: D-glucose + ATP → D-glucose 6-P + ADP

phosphoglucose isomerase: D-glucose 6-P ↔ D-fructose 6-P

6-phosphofructose-1-kinase*: D-fructose 6-P + ATP → fructose 1,6-PP + ADP

fructose bisphosphate aldolase: fructose 1,6-PP ↔glyceraldehyde 3-P + dihydroxyacetone-P

triose phosphate isomerase: dihydroxyacetone-P ↔ glyceraldehyde 3-P

glyceraldehyde 3-P dehydrogenase: glyceraldehyde 3-P + NAD + Pi ↔+1,3-bisphosphoglycerate + NADH + H

phosphoglycerate kinase: 1,3-bisphosphoglycerate + ADP ↔ 3-phosphoglycerate + ATP

phosphoglycerate mutase: 3-phosphoglycerate ↔ 2-phosphoglycerate

enolase: 2-phosphoglycerate ↔ phosphoenolpyruvate + H2O

pyruvate kinase*: phosphoenolpyruvate + ADP → pyruvate + ATP

* irreversible enzyme

Front 21

The pyruvate dehydrogenase complex activates the product of glycolysis, pyruvate, so that itmay be transported into a ________ and made available to the enzymes of thetricarboxylic acid (TCA) cycle within cells with __________.

Back 21

mitochondrion

pyruvate dehydrogenase complex (net): pyruvate + coenzyme A + NAD+ →acetyl CoA + CO2 + NADH + H+

pyruvate dehydrogenase: pyruvate + thiamin pyrophosphate →acetylthiamin pyrophosphate + CO2

dihydrolipoyl transacetylase: acetylthiamin pyrophosphate + lipoylsulfide →acetyl-S-lipoyl sulfide + thiamin pyrophosphateacetyl-S-lipoyl sulfide + coenzyme A →acetyl CoA + lipoyl disulfide

dihydrolipoyl dehydrogenase: lipoyl disulfide + FAD →lipoyl-S2 + FADH2FADH2 + NAD+ → NADH + H+ + FAD

Front 22

Some cells, such as erythrocytes, lack mitochondria and cannot metabolize pyruvate tocarbon dioxide. Instead, in such cells pyruvate is converted to ________.

Back 22

lactate

lactate dehydrogenase: pyruvate + NADH + H+ → lactate + NAD+

Front 23

The tricarboxylic acid (TCA) cycle is the metabolic pathway that oxidizes ______ derivedfrom the catabolism of fatty acids, amino acids and carbohydrates to ______.

Back 23

acetate

carbon dioxide

citrate synthase*: acetyl CoA + H2O + oxaloacetate → citrate + coenzyme A (CoA)

aconitase: citrate ↔ cis-aconitate + H2O ↔ isocitrate

isocitrate dehydrogenase: isocitrate + NAD+ ↔ α-ketoglutarate + CO2 + NADH + H+

α-ketoglutarate dehydrogenase: α-ketoglutarate + NAD+ + CoA ↔succinyl CoA + CO2 + NADH + H+

succinyl CoA synthetase: succinyl CoA + GDP + Pi ↔ succinate + GTP + CoA

succinate dehydrogenase: succinate + FAD ↔ fumarate + FADH2

fumarase: fumarate + H2O ↔ L-malate

malate dehydrogenase: L-malate + NAD+ ↔ oxaloacetate + NADH + H+

citrate synthase*: acetyl CoA + H2O + oxaloacetate → citrate + CoA

* irreversible enzyme

Front 24

The TCA cycle is considered an aerobic process because it requires the ability to transferexcess electrons to oxygen molecules via mitochondrial cytochromes (the electron transportchain) in order to regenerate _____ and ____.

Back 24

NAD+ and FAD

NADH + H+ + oxidized coenzyme Q + ADP + Pi → NAD+ + reduced coenzyme Q + ATP

FADH2 + oxidized coenzyme Q → FAD + reduced coenzyme Q

reduced coenzyme Q + oxidized cytochrome b →oxidized coenzyme Q +

reduced cytochrome b

reduced cytochrome b + oxidized cytochrome c1 + ADP + Pi →oxidized cytochrome b + reduced cytochrome c1 + ATP

reduced cytochrome c1 + oxidized cytochrome c →oxidized cytochrome c1 + reduced cytochrome c

reduced cytochrome c + oxidized cytochrome a →oxidized cytochrome c + reduced cytochrome a

reduced cytochrome a + oxidized cytochrome a3 + ADP + Pi →oxidized cytochrome a + reduced cytochrome a3 + ATP

reduced cytochrome a3 + O2 → oxidized cytochrome a3 + H2O

Front 25

The p____________ is an alternate pathway of glucose catabolism that also isinvolved in the biosynthesis of pentose sugars (especially ribose) and NADPH2 throughthe production of ribulose 5-P.

Back 25

pentose monophosphate shunt

glucose 6-P dehydrogenase: glucose 6-P + NADP+ → 6-phosphogluconolactone + NADPH + H+

6-phosphogluconolactonase: 6-phosphogluconolactone + H2O → 6-phosphogluconate + H+

phosphogluconate dehydrogenase: 6-phosphogluconate + NADP+ →ribulose 5-P + CO2 + NADPH + H+

Front 26

Ribulose 5-P is converted to _________5-P and other phosphorylated carbohydrates.

Back 26

Ribose 5-P

ribulose 5-P isomerase: ribulose 5-P → ribose 5-P

ribulose 5-P epimerase: ribulose 5-P → xylulose 5-P

transketolase: ribulose 5-P + xylulose 5-P → sedoheptulose 7-P + glyceraldehyde 3-P

transaldolase: sedoheptulose 7-P + glyceraldehyde 3-P → erythrose 4-P + fructose 6-P

transketolase: erythrose 4-P + xylulose 5-P → fructose 6-P + glyceraldehyde 3-P

Front 27

___________ is the primarily hepatic pathway by which glucose is synthesized de novo fromlactate, pyruvate or alanine in the liver (90%) and kidneys (10%).

Back 27

Gluconeogenesis

In general, gluconeogenesis isthe reverse of glycolysis. However, 3 irreversible glycolytic enzymes (glucokinase,phosphofructokinase, and pyruvate kinase) must be bypassed via additional enzymatic pathwaysthat operate only during gluconeogenesis in order to avoid futile cycling.

Front 28

As the rate of glycolysis decreases, free acetylCoaconcentration _________ and pyruvate carboxylase is stimulated.

Back 28

increases

Front 29

Pyruvate kinase, which catalyzes the irreversible conversion of phosphoenolpyruvate (PEP) topyruvate, is bypassed in 2 steps.

1. pyruvate carboxylase (needs ____) to catalyze conversionof pyruvate to oxaloacetate. This reaction uses ___ ATP andrequires free acetylCoA as an allosteric activator of the pyruvate carboxylase enzyme.

Back 29

1. Biotin and 2 ATP

pyruvate carboxylase: pyruvate + CO2 + biotin + 2 ATP + coenzyme A →oxaloacetate + biotin + coenzyme A + 2 ADP + 2 Pi

Front 30

Pyruvate kinase, which catalyzes the irreversible conversion of phosphoenolpyruvate (PEP) to pyruvate, is bypassed in 2 steps.

2. phosphoenolpyruvate carboxylase utilizes 1 molecule of high-energy____ to convert oxaloacetate to PEP.

Back 30

2. GTP

phosphoenolpyruvate carboxylase: oxaloacetate + GTP →phosphoenolpyruvate + CO2 + GDP + Pi

Front 31

Phosphofructokinase, which catalyzes the irreversible conversion of fructose 6-P to fructose1,6-PP, is bypassed by _______.

Back 31

fructose 1,6-bisphosphatase

This enzyme splits fructose 1,6-PP into fructose 6-P and inorganic phosphate.

fructose 1,6-bisphosphatase: fructose 1,6-PP + H2O → fructose 6-P + Pi

Front 32

___________, which catalyzes the irreversible formation of glucose 6-P, is bypassed byglucose 6-phosphatase, which produces glucose and inorganic phosphate.

Back 32

Glucokinase

glucose 6-phosphatase: glucose 6-P + H2O → glucose + Pi

Front 33

Gluconeogenesis from pyruvate produces____ glucose molecule at the cost of ____ molecules ofpyruvate, ___molecules of ATP and ___molecule of GTP.

Back 33

1 glucose

cost 2 pyruvate, 2 ATP and 1 GTP

The metabolism of glucose to pyruvateand the regeneration of glucose from that pyruvate results in a net loss of energy and, within thesame cell, would be an example of a futile cycle. However, during times of limited glucosesupply, this pathway of glucose regeneration within hepatocytes provides circulating glucose foruptake by the central nervous system.

Front 34

Alanine cycle:

pyruvate from anaerobic glycolysis is aminatedwithin muscle to produce alanine

Alanine secreted into the circulation and is taken up bythe _____.

In _______, alanine is deaminated to reform pyruvate.

Back 34

Liver; Hepatocytes

Gluconeogenesisproduces glucose from the pyruvate; the glucose then is recirculated and made available tomuscle cells to replenish their intracellular glucose reserves.

Front 35

In the _____, lactate secreted by erythrocytes is taken up by hepatocytes, converted backto pyruvate and then via gluconeogenesis to glucose for secretion into the blood.

Back 35

Cori cycle

Front 36

The synthesis of proteins results from the translation of ________, in an energy consumingprocess requiring the participation of a set of transfer RNAs (tNRA) and ribosomalRNA.

Back 36

messenger RNA

A molecule of mRNA coding for a specific protein associates with a ribosome

ThemRNA-ribosomal complex accepts amino acids from substrate-specific tRNA molecules in asequence determined by the composition of the mRNA and assembles them into a linearpolypeptide chain.

Front 37

The degradation of proteins (outside of the GI tract) occurs through theirhydrolysis within intracellular ________ or within the cellular cytoplasm following theiridentification as targets for proteolysis by binding to one or more molecules of ubiquitin.

Back 37

lysosomes

Front 38

________ is the enzymatic hydrolysis of proteins into individual amino acids, dipeptides andtripeptides.

Back 38

Proteolysis

Front 39

The deamination of amino acids produces______ and _____.

Back 39

ammonia (NH3) and keto- acids.

Ketoacidscan be oxidized through the TCA cycle.

Front 40

The hepatic urea cycle produces urea from____ and ____; urea is excreted in the urine.

Back 40

ammonia and CO2

Front 41

Free fatty acids are activated for oxidation by the addition of _______ in an ATP- requiringreaction.

Back 41

coenzyme A

Front 42

Fatty acyl CoA molecule combines with _______for mediatedtransport into mitochondria.

Back 42

Carnitine

In mitochondria, complete oxidation of the original fatty acid occurs.

Front 43

Within mitochondria, 2-carbon units (acetyl-CoA) are cleaved (decarboxylation) via ________ and transferred to TCA cycle enzymes.

T

Back 43

betaoxidation

The remaining fatty acid remnant is combined to another coenzyme A moiety and the cycle of beta-oxidation is continued until only a 2- or 3- carbon unit remains.

Front 44

Pre-formed cholesterol is obtained from food and much more cholesterol is synthesized by the_____ from carbohydrates, saturated fatty acids or alcohol.

Back 44

liver

Front 45

Because of its ______ nature, cholesterol must be transported in blood in association withspecific carrier lipoproteins (VLDL, LDL, IDL, HDL).

Back 45

sterol

Front 46

FUN FACTS

Nucleic Acids - Adenosine metabolism:

Adenosine triphosphate (ATP) is a molecule of adenosine to which 3 phosphate groups are attached

Back 46

if one phosphate is removed, adenosine diphosphate (ADP) isproduced; if 2 phosphates are removed, adenosine monophosphate (AMP) results. Because thisphosphate bond is a "high-energy" bond, it contains a large amount of potential chemical energyand its cleavage by enzymes releases this energy to perform biochemical work

Front 47

Ketones result from the metabolism of:

a. fatty acids.

b. simple sugars.

c. amino acids.

d. complex carbohydrates.

Back 47

a. fatty acids.

Front 48

Glycolysis is a metabolic process that involves:

a. glycogen synthesis

b. the conversion of glucose to glycogen

c. the conversion of glucose to pyruvate.

d. the conversion of fatty acids to ATP

Back 48

c. the conversion of glucose to pyruvate.