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192 Cards in this Set

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  • Back
378. What vitamin is pyridoxal phosphate?
Vitamin B6
379. What is the difference between the active form of pyridoxal and the reaction intermediate?
1. Active form (PLP) can take up e- and donate them back readily (it has a C=O in it)

2. Reaction intermediate (pyridoaxime phosphate) has an +NH3 instead of the carbonyl
380. Through what type of reaction do PLP catalyzed reactions proceed?
A Schiff base (imine) intermediate
381. Remember what an imine is?
382. From where are the carbon skeletons of amino acids made?

Three places...
1. Intermediates in glycolysis

2. Intermediates in the citric acid cycle

3. Intermediates in the pentose phosphate pathway
383. How are all the pathways in making amino acids regulated?
They are allosterically regulated by feedback inhibition
384. How many amino acids can humans make?

Where do we get the others from?
Humans can make only 10 of the 20 amino acids

We get the rest from our food
385. What are the 10 essential amino acids?
1. Methionine
2. Threonine
3. Lysine
4. Valine
5. Leucine
6. Isoleucine
7. Tryptophan
8. Tyrosine
9. Phenylalanine
10. Histidine
386. What are the four functions of nucleotides?
1. Precursors for RNA and DNA
2. Energy (i.e. ATP)
3. Signaling Molecules (cAMP)
4. Phosphate donors for protein modification
387. What are the three basic components of nucleotides?
1. A pentose

2. A base

3. Phosphates
388. What are the five main types of bases?
1. Adenine
2. Guanine
3. Cytosine
4. Thymine (DNA)
5. Uracil (RNA)
389. Which bases are purines and which are pyrimidines?
Purines: adenine and guanine

Pyrimidines: cytosine, thymine, and uracil
390. What are the two types of sugars in nucleotides?

How do the sugars differ?
The two sugars are ribose and deoxyribose

They differ at C2 in that ribose has a hydroxyl group (-OH) and deoxyribose does not
391. To which carbon on the sugar does the base hook itself?
The base hooks onto C1
392. What types of phosphates can be on nucleotides?
A variable number (mono-, di-, and tri-)
393. What do you call a base + a sugar?
394. How do you name nucleosides?
Purines: -sine
Pyrimidines: -dine

Adenosine/ Deoxyadenosine
Guanosine/ Deoxyguanosine
Cytidine/ Deoxycytidine
395. What do you call a base + a sugar + a phosphate?
396. How does you name nucleotides?

Adenylate/ Deoxyadenylate
Cytidylate/ Deoxycytidylate
397. What is a ribonucleotide

Two things...
1. Contains ribose and uracil

2. Used to make RNA
398. What is a deoxyribonucleotide?

Two things...
1. Contains deoxyribose and thymine

2. Used to make DNA
399. What are two important signaling molecules that are nucleotides?
1. Cyclic AMP (cAMP)

2. Cyclic GMP (cGMP)
400. What two ways do you make nucleotides?
1. In the de novo pathway

2. In the salvage pathway
401. What is the de novo pathway?
Purines and pyrimidines are assembled on an "active ribose" to first make the nucleotides
402. What is salvage pathway?
Free bases are recycled by reattachment to an "activate ribose" derivative
403. What is the "activated ribose" important for the de novo pathway and the salvage pathway?
5 phosphoribosyl-1-phosphate

*stick a base on it through group transfer
*pyrophosphate activates this bond
404. What are important de novo intermediates?

Two of them
1. Inosine: make adenosine and guanosine from it

2. Orotate: make cytosine and uridine from it
405. How do you regulate purine biosynthesis?
Feedback inhibition
406. What is enzyme is involved in the major control point of purine biosynthesis?
glutamine-PRPP amidotransferase
407. How are pyrimidines synthesized?
They are constructed from carbamoyl phosphate and aspartate
408. What enzyme catalyzes the reaction between carbamoyl phosphate and aspartate to form carbamoyl-aspartate?
Aspartate transcarbamoylase (ATC)
409. How is the carbamoyl phosphate formed?

Two points...
1. Use HCO3, NH4, and 2ATP

2. Carbamoyl synthetase II is the enzyme used
410. What regulates pyrimidine biosynthesis?
Feedback inhibition of ATC by end product CTP
411. What happens in nucleotide salvage pathways?
1. Degrade the nucleotide/nucleoside to a free base
2. Remake the nucleoside by condensation w/ phosphoribosyl pyrophosphate
3. Various kinases rebuild to triphosphate form
412. What disease shows us that the salvage pathway is very important?

What can happen from this disease
Lesch-Nyhan Syndrome where there is a deficiency in the guanine phosphoribosyl tranferase

The disease causes retardation, tendency toward self-mutilation, and death in childhoo
413. What are some additional nucleotide complications?

Two things...
1. Making deoxyribose

2. Making thymidine
414. How is deoxyribose made?

Three steps...
1. Use ribonucleotide reductase
2. Reduce -OH
3. Proceed by means of free radical reactions (very sensitive to free radical inhibition)
415. What does ribonucleotide reductase do?
It uses ribonucleotide diphosphates of the 4 bases (NDP's) and NADPH to make all 4 deoxyribonucleotide diphosphates
416. How is thymidine synthesized?
Through a special pathway that has 3 moving parts
(not made as part of the de novo pathway)
417. What are the three parts of thymidine biosynthesis?
1. Thymidine synthase

2. Tetrahydrofolate

3. Dihydrofolate reductase
418. What does thymidine synthase do?
It adds a methyl group to deoxyuracil monophosphate
419. What does tetrahydrofolate do?
It provides both the carbon and the electrons

*Note that a carbon is added to dUMP to make dTMP
420. What does dihydrofolate reductase do?
It re-generates the tetrahydrofolate from dihydrofolate using NADPH
421. What are chemotherapeutic targets?

Two of them...
1. Inhibit thymidylate synthase using FdUMP

2. Inhibit dihydrofolate reductase with methotrextate aminopterin trimethoprim
422. What does inhibiting these targets result in?
Shut down proliferation of cancer cells because you cannot make DNA
423. What are folate and s-adenosylmethionine?
They are carriers of 1 carbon units in one carbon transfers in amino acid and nucleotide biosynthesis
424. What does folate do?
It transfers carbon in intermediate oxidation states (-CH2OH, -COOH)
425. What does s-adenosylmethionine do?
It transfers reduced carbon (-CH3)
426. What is tetrahydrofolate?
H4 folate (cofactor)

*Serine is the source of one-carbon units for tetrahydrofolate
427. What is sulfanilamide?
Antibiotic that competes with p-aminobenzoate in folate synthesis
428. What is the active part of s-adenosylmethionine (adoMET)

How is it made?
The active part is +S-CH3 part

AdoMET is made through condensation reation
429. List all the cofactors we know and what they transfer.

Eight total!
1. Thiamin: active acetaldehyde
2. CoA: acetyl
3. Biotin: active carbon dioxide
4. Folate: 1 carbon,various oxidation states
5. S-adenosylmethionine: activated methyl
6. Flavins: e-
7. Nicatinamide: e-
8. Pyridoxal phosphate: NH4
430. What is the first step in amino acid degradation?
Separation of the amino group from the carbon skeleton
431. Where does the NH4 go?

Where does the carbon skeleton go?
NH4 goes to urea cycle

Carbon goes to glycolysis or citric acid cycle
432. What are the ultimate two fates of carbons from amino acid degradation?
1. Become ketone bodies

2. Become glucose
433. What are the three ways in nitrogen is excreted?
1. Ammonia

2. Urea (need water to do this)

3. Uric acid (insoluble; bird crap)
434. Why do we need to get rid of ammonia?
Toxic to the body (causes our pH to vary)
435. How does our body get rid of ammonia?

Three step process...
1. Transports excess NH4 to the liver

2. Uses the urea cycle to transform NH4 into the less toxic component urea

3. Excrete urea
436. How is excess ammonia in the form of alanine and glutamine transported for disposal?
1. Alanine is a carrier for NH4 and the carbon skeleton of pyruvate from the skeletal muscle to the liver

2. NH4 is excreted and pyruvate is used to produce glucose which is returned to the muscles
437. Why is alanine amino transferase (ALT) in the blood indicative of liver damage?

Three points...
1. ALT is normally in liver not blood stream
2. Damage to liver releases ALT into the blood serum
3. Assay the level of ALT in the blood to check for liver damage from hepatitis, cirrosis, or chronic alcoholism
438. Where is urea made?
In the urea cycle in the cytosol of liver cells
439. What two things are hydrolyzed to make urea?
1. Arginine

2. Ornithine (similar to oxaloacetate in that it accepts material at each turn of cycle)
440. Where do the two amino groups that enter the urea cycle come from?

Two places...
1. Carbamoyl phosphate (formed in the mitochondrial matrix)

2. Asparatate (formed in the mitochondrial matrix)
441. What enzyme is used in making carbamoyl phosphate from NH4, HCO3, and 2ATP?
Carbamoyl phosphate synthetase I
442. What are the four steps of the urea cycle?
1. Formation of citrulline
2. Formation of argininosuccinate
3. Formation of arginine
4. Formation of urea
443. What are the two steps at which nitrogen is incorporated?
1. First reaction catalyzed by carbamoyl phosphate synthetase I

2. In the reaction catalyzed by argininosuccinate synthetase (nitorgen enters from aspartate)
444. How many molecules of ATP are used to make one molecule of urea?
445. Describe the first reaction in the urea cycle?

Three points...
1. Ornithine and carbamoyl phosphate form citrulline
2. Ornithine transcarbamoylase catalyzes
3. Citrulline passes from mitochondria to cytosol
446. What happens to citrulline next?
It forms a citrullyl-AMP intermediate using argininosuccinate synthatase
447. Describe the second step of the urea cycle.

Four points...
1. Second amino group enters from aspartate
2. Form argininosuccinate
3. Argininosuccinate synthatase catalyzes
4. ATP is required
448. Describe the third step of the urea cycle.

Three points
1. Formation of arginine from argininosuccinate
2. Fumarate is released and goes to citric acid cycle
3. Argininosuccinase catalyzes
449. Describe the fourth step of the urea cycle.

Three points...
1. Formation of urea
2. Regenerate ornithine which goes into mitochondria for another round
3. Arginase catalyzes
450. What couples the citric acid cycle and the urea cycle?
The aspartate-argininosuccinate shunt
451. What two molecules specifically like the urea cycle and the citric acid cycle?
1. Fumarate

2. α-ketoglutamate
452. How is uric acid made?
1. From purine degradation

2. Made by the mixed function oxigenase xanthine oxidase
453. What reaction does xanthine oxidase catalyze?
Xanthine to uric acid (insoluble)
454. What do finally end up after the degradation of pyrimidines?
Urea and after further degradation succinyl-CoA
455. What is Gout?

What causes gout?
Inflammatory arthritis (painful and tends to reoccur)

Caused when uric acid crystals are deposited in connective tissue and/or in the fluid that cushions the joint
456. How is gout treated?
Long-term treatment involves blocking the activity of xanthine oxidase

*remember that enzyme is used in uric acid formation from purine degradation
457. What inhibits xanthine oxidase?

How does it inhibit?

It forms oxypurinol which doesn't dissociate from the active site of xanthine oxidase
458. Cells are not islands and need to communicate. What fulfills the necessity of intercellular communication?
459. What are the glands we need to know?

Nine of them...
1. Hypothalamus
2. Pituitary
3. Thyroid
4. Parathyroids
5. Adipose tissue
6. Adrenals
7. Pancreas
8. Kidneys
9. Ovaries or Testes
460. How do hormones work?

Three step process...
1. Glands synthesize a hormone which diffuses to target cells
2. The target has a receptor that binds the hormone
3. Hormone/receptor binding results in a response within the target cell that affects the activity of specific enzyme(s)
461. What are two basic characteristics of hormone-receptor interactions?
1. Specificity

2. High affinity

*both important since hormones are present at low concentrations
462. What is meant by specificity?
Only the correct hormone binds to the correct receptor
463. What is meant by high affinity?
Receptors bind hormones tightly
464. How can little hormones cause such a big response?

Two ways...
1. Signal transduction

2. Amplification
465. What is amplification?
When enzymes activate enzymes, the number of affected molecules increases geometrically in an enzyme cascade
(amplify effect of previous step)
466. In what ways does hormone/receptor binding lead to signal amplification?

Two ways...
1. Production of second messenger molecules

2. A kinase cascade
467. What do second messengers do?

What are examples of second messengers
They amplify the signal

Examples are cAMP, cGAMP, IP3, and Ca++
468. What are cAMP and cGMP?

Three things...
1. Modified purine nucleotides

2. Allosteric regulators

3. Made by adenyly cyclase and guanyly cyclase respectively
469. How is Ca++ a second messenger?

Three points...
1. Normally Ca++ is outside the cell
2. When hormone binds receptor though membrane opens
3. Ca++ enters cell and activates enzymes
470. Where do water-soluble hormones bind?
Bind external receptors on the cell surface (bind outside of the cell; don't enter it directly)
471. What interaction do water-soluble hormones stimulate?

Two things...
1. Production of second messenger molecules

2. Kinase cascades
467. What are second messengers?
Intracellular signaling molecules that allosterically regulate critical cellular enzymes
472. What happens in kinase cascades?
The message is propagated by sequential phosphorylation of proteins in a signal transduction pathwya
473. How do water soluble hormones achieve their function?

Two ways...
1. Changing the activity of a target protein

2. Opening or closing an ion channel
471. What are water-soluble hormones?
Not membrane permeable
474. What are hydrophobic hormones?
475. Where do hydrophobic hormones bind?
They bind to internal receptors inside the cell since they can diffuse through the cell membrane
476. What do hormones bound to internal receptors often stimulate?
Activate the transcription of target genes
477. What is the purpose of hydrophobic hormones?

Two things...
1. Make more of an enzyme not change its activity

2. More of a long-term acting hormone
478. What are the different groups of hormones?

Three groups...
1. Water soluble

2. Lipid soluble (hydrophobic)

3. Intracelluar
479. What are three examples of water soluble hormones?
1. Peptide hormones

2. Catecholamine

3. Eicosanoids
480. What are two examples of lipid soluble hormones?
1. Steroids

2. Thyroid
481. What is an example of an intracellular hormone?
Nitric oxide
482. Describe peptide hormones?

Four points...
1. Amino acid chains processed from longer precursors

2. Stored in internal vesicles until released into intercellular space

3. Bind cell surface receptor to start signal transduction cascade

4. Work very rapidly
483. What are three examples of peptide hormones?
1. Insulin

2. Glucagon

3. Hormones of pituitary and hypothamus
484. What do catecholamine hormones mediate?

What else do they do?
They mediate stress response

They act as neurotransmitters or hormones that cause secondary messenger production
485. What are catecholamine hormones derived from?
They are derived from catechol via tyrosine in the brain and adrenal gland
486. What do eicosanoids cause?

Three things...
1. Smooth muscle contraction

2. Inflammation

3. Blood clotting
487. How are eicosanoids made?
They are made from arachidonate on an as needed basis by most tissues of the body
488. How do eicosanoids act?
They act as paracrine hormones on adjacent cells via cell surface receptors
489. How far do eicosanoids hormones act?
They act short-range and have a local affect
490. What are steroid hormones produced from?
491. Where are steroids produced?
In adrenal cortex
492. What is the function of steroid hormones?
They act on nuclear receptors that induce transcription of target genes

*long-term effects
493. How do steroid hormones travel to their target cells?
They travel through the blood plasma bound to carrier proteins
494. What are thyroid hormones produced from?
The precursor thyroglobulin-tyr
495. What is essential to making thyroid hormones?
496. What is the regulated step in thyroid hormone synthesis?
Conversion of iodinated Tyr residues to the active hormone T3 by proteolysis
497. What is the function of thyroid hormones?

Two things...
1. Regulate transcription through nuclear receptors

2. Regulators of energy metabolism (stimulate in liver and muscles by increasing expression of certain gene)
498. How is nitric oxide formed?
Synthesized from molecular oxygen and nitrogen of arginine in reaction catalyzed by NO synthase
499. What is nitric oxide?
Relatively stable free radical (it's a gas!)
500. What is the function of nitric oxide?
Activates guanyly cyclase to make cyclic GMP (a secondary messenger)
501. Does nitric oxide travel far?
No, it works near point of origin
502. How are hormones regulated?
In a hierarchical manner
503. What is the top of the hierarchy?
504. What does the hypothalamus do?
It monitors the status of the body and responds by generating any number of specific releasing hormones
505. What do the specific releasing hormones do?
They cause the anterior pituitary to make specific tropins that regulate specific endocrine glands
506. What do the specific tropins do?
They activate the specific endocrine gland to make specific hormoones
507. Last but not least, what do the hormones do?
They target specific cell types
508. What are the master regulatory glands?

Two glands...
1. Hypothalamus

2. Pituitary
509. What is the main function of these two glands?
To act as the interface between the nervous system and the endocrine system
510. When the hormone binds the receptor, in what ways can the interaction affect the cell?

Three ways...
1. Open ion channels
2. Activate a signal transduction cascade that activates/represses specific enzymes
3. Induce transcription of target gene(s)
488. What are paracrine hormones?
They are released into the extracellular space and diffuse to neighboring target cells
511. How does acetylcholine hormone affect the cell?
It's a neurotransmitter that opens ion channels

*binding to receptor causes the affect
512. How does the binding of insulin (a peptide hormone) affect the cell?

Three points...
1. Binding causes phosphorylation

2. A kinase cascade is used to activate glycogen synthase

3. Signal transduction and amplification is illustrated
513. What does the peptide hormone glucagon use to activate glycogen phosphorylase?
Second messengers (cAMP)
514. What is the liver responsible for?

Four jobs...
1. Keeping blood sugar levels constant
2. Degrading FA's to ketone bodies when glucose supply is low
3. Remove excess NH4 through urea cycle
4. Regenerate glucose from lactate following exercise
515. What do the muscles use for mechanical work?

*But different fuels are used for ATP synthesis for various kinds of activity
516. What is used for light activity or rest?

Three fuels...
1. Fatty acids

2. Ketone bodies

3. Blood glucose

*release CO2
517. What is used for bursts of heavy activity?
Muscle glycogen

*release lactate
518. What else can be used for bursts of heavy activity?

*release creatine
519. What is phosphocreatine?

Two things
1. A storage form of ATP in the muscles

2. Able to generate ATP quickly
520. How is ATP generated by phosphocreatine?
It's dephosphorylated and gives the Pi to ADP forming ATP

*During recovery creatine is phosphorylated to reform phosphocreatine
521. Describe adipose tissue?

Two points...
1. Amorphous

2. Distributed throughout the body
522. What is the function of adipose tissue?

Two jobs...
1. Store triacylglycerides (TAG's) arriving from liver or intestine

2. Synthesize, store, and mobilize TAG's
523. What percent of mass is mostly TAG's in a fit person?
15% the mass of a fit person
524. What does the brain use to maintain electrical activity?

Two molecules...
1. Glucose (normal diet)

2. Ketone bodies (starvation)
525. What can lapses in blood glucose level to the brain?
Cause permanent brain damage (even momentary lapses)
526. What is the role of blood?
It's the main transport system for food and waste

*Blood glucose levels must be tightly controlled
527. Where does blood carry food?

Where does it carry waste?
Blood carries food (O2, glucose, ketone bodies) to peripheral tissue

Blood carriers waste (CO2, excess NH4) to liver and lungs
528. What happens in the well-fed state liver?

First three things
1. After calorie rich meal, glucose, FA's, and AA's enter the liver
2. Insulin is released (response to high blood glucose levels)
3. Glucose uptake by tissues
529. What happens to the glucose?

Three fates...
1. Some is exported to the brain

2. Some is exported to fat and muscle tissues

3. Some stored as glycogen
530. How is some glucose exported to fat and muscle tissues?

Three parts...
1. Excess glucose in the liver is oxidized to acetyl-CoA
2. Acetyl-CoA synthesized to FA
3. Export as TAG's in VLDL to fat and muscle tissue
531. What are amino acids used for in the well-fed state liver?

Two things...
1. Metabolize for protein synthesis

2. Metabolize to α-keto acids and then urea
532. What happens to the fat in the well-fed state liver?
They are not really metabolized and just go to adipose tissue
533. What is the order of use of molecules by the well-fed liver?
Carbohydrates, TAG, and then proteins (amino acids)
534. What happens in the fasting liver?

Four things...
1. Liver becomes principal source of glucose for brain
2. Break glycogen down and ship glucose to brain
3. Once all possible glucose is used, ketone bodies will be used
4. When you run out of fat, proteins in your muscles will be metabolized
535. What hormones are used for short-term, fast acting regulation of metabolism?

Three hormones....
1. Insulin: stimulates energy storage

2. Glucagon: stimulates energy release

3. Epinephrine: stimulates energy release
536. What hormones are used for slow acting regulation of metabolism?

Two hormones
1. Cortisol: activity similar to glucagon

2. Thyroid hormone: activity similar to insulin
537. What stimulates the release of epinephrine?
Stress stimulates the release of epinephrine from the adrenal glands
538. What is epinephrine important for?
Fight or flight response
(quick energy)
539. What do epinephrine's activities include?

Four things...
1. Increasing O2 to muscles
2. Stimulating an increase in blood glucose
3. Increased β-oxidation
4. Stimulates glucagon release, inhibits insulin release
540. Describe cortisol.

Three points
1. Steroid hormone

2. Made by adrenal gland

3. Used for long-term situation
541. What does cortisol do?
Adjust to stress by stabilizing blood glucose levels in a slower manner by inducing synthesis of various enzymes
542. Cortisol produces enzymes needed for...

Three reactions
1. Gluconeogensis

2. β-oxidation

3. Break down of proteins for energy
543. What does the thyroid hormone do?
It stimulates the production of adipose tissues when times are good (many of the same things insulin does)
544. How does the thyroid hormone work?
It works through induction of transcription of enzymes needed for fat synthesis (i.e. fatty acid synthase, acetyl-CoA carboxylase)
545. What does lack of the thyroid hormone cause?
Cretinism which is characterized by severe mental and physical retardation
546. How long does your glycogen supply last?
12-24 hours
547. How long does your triacylglyceride (TAG) supply last?
2.5 months for a fit person

maybe up to 4 years for a chunky beefy person...ugh
548. How long does your protein supply last?
nasty cannibal.

2 weeks if you're lucky
549. What is type 1 diabetes?
results from an inability to make insulin

very severe

treated by injection of insulin
550. What is type 2 diabetes?
results from a partial or complete inability to respond to insulin (called insulin resistant)

often late onset

treatment by diet
551. What is odd about diabetes?
With both types of diabetes although you're well fed, your body thinks it's starving
552. What are some metabolic characteristics of diabetes?
High blood glucose

High [glucose] in urine, resulting in excessive thirst and much piss

Increased degradation of TAGs with overproduction of ketone bodies and lowering of blood pH
553. What are some diseases, conditions of diabetes down the road?
heart disease


circulation problems

nerve damage
554. How does the glucose tolerance test work?
Fast the night before and then eat lots of glucose

Measure glucose levels every 30 minutes afterwards for several hours

If blood glucose levels don't decrease with time, person has diabetes
555. What are most people with Type II diabetes like?
556. How do you treat diabetes?

Four ways...
1. Insulin injection (type I)
2. Control diet (avoid simple sugars)
3. Exercise
4. Drugs are available to stimulate insulin production
557. Obesity: BMI
BMI below 25: normal

BMI bwt 25 and 30: overweight

BMI over 30: Obsese
558. What is the basis of the lipostat theory?
1. You're hungry
2. You eat something
3. You are no longer hungry
*body regulates mass so you don't become beefy chunky
559. What is the lipostat theory
The idea that adipose tissue secrets a hormone that inhibits appetite and increases energy consumption
560. What are the candidates for the lipostat theory?


561. What is Leptin?
Hormone secreted by adipose tissue that controls weight
562. What is Adiponectin?
An adipose produced hormone

Peptide hormone that increases FA uptake and β-oxidation in muscles via inhibition of acetyl-CoA carboxylase
563. Have we solved obesity?

Most obese people have increased levels of leptins

Mice lacking adiponectin have normal weight
564. What are ghrelin and obestatin?
Small hormones secreted by the lining of your stomach
565. What is ghrelin?
Appetite stimulant
566. What is obestatin?
An appetite suppressant

In mice, exogenous obestatin caused them to lose weight