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Biochem > Exam #3: (32-38) > Flashcards

Exam #3: (32-38) Flashcards

1
Q

Describe the LDL endocytosis process

A
  1. ) LDL binds receptor
  2. ) Vesicle containing bound LDL loses its clathrin and FUSES with other similar vesicles, forming larger vesicles called ENDOSOMES.
  3. ) The pH of the endosome FALLS (due to proton-pumping activity of endosomal ATPase), which allows for separation of the LDL from its receptor. Receptors migrate to one side of the endosome, and LDLs stay free in the lumen of the vesicle (this structure is called the Compartment for Uncoupling of Receptor and Ligand (CURL).
  4. ) Receptors are recycled, lipoprotein remnants transeffered to lysosomes and degraded by lysosomal acid hydrolases, releaseing free cholesterol, amino acids, FA, and phospholipids. These can be utilized in the cell.
    p. 427
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2
Q

What does Glutamine Synthetase do?

A
  • Removes excess ammonia (NH4+) by adding it to glutamate to form GLUTAMINE.
  • It then travels to the liver and kidney where NH4+ is removed by GLUTAMINASE to reform Glutamate.
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3
Q

What is nitrogen balance?

A

The difference between dietary intake of nitrogen (mainly protein) and its excretion (as urea and other waste products)

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4
Q

How are dietary proteins digested (3)? Describe

A
  1. ) Stomach: HCL (pH 2-3) via parietal cells, and Pepsinogen–pepsin (mainly bulky, hydrophobic amino acids)
  2. ) Pancreatic enzymes: Endo and exopeptidases
  3. ) Intestines: Enteropeptidase activates zymogens –> Aminopeptidases: exopeptidase that cleaves N-terminus, making a free amino acid and smaller peptide
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5
Q
  1. ) Under low-energy conditions, what will happen concerning amino acids?
  2. ) What stimulates this process?
A
  1. ) They will be deaminated to alpha-keto acids (alpha-ketoglutarate) in order to feed the TCA.
  2. ) ADP (or AMP) and GDP
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6
Q
  • What are the two sources of nitrogen for ammonia?

- What else is needed?

A
  • Ammonia as CARBAMOYL PHOSPHATE, and ASPARTATE
  • 4 ATP
  • 5 enzymes
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7
Q
  1. ) Which hormone(s) stimulate the production of testosterone and estrogen? Where from?
  2. ) Via which type of pathway do they operate?
A
  1. ) Leutinizing Hormone (LH) and Follicle-stimulating Hormone (FSH). Both from the anterior pituitary.
  2. ) Gs signaling pathway
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8
Q

Generally speaking, by what mechanism do ALL statins function?

A

They are all COMPETITIVE INHIBITORS of HMG-CoA REDUCTASE = Drop in cholesterol synthesis in the liver.

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9
Q

What is the medical term for chronic endothelial injury?

A

Atherosclerosis

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10
Q

What are the products of LDL metabolism (3)?

A
  1. ) Cholesterol
  2. ) Fatty acids
  3. ) Amino acids
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11
Q

What is the progression of intermediates in the synthesis of steroid hormones (corticosteroids, sex steroids, progesterone)? Give the subclasses of all.

A

Cholesterol –> Progesterone
Cholesterol –> Progesterone –> Corticosteroids (glucocorticoids and mineralcorticoids)
Cholesterol –> Progesterone –> Sex Steroid (androgens and estrogens.

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12
Q
  1. ) What is formed by transferring an amino group from alanine to alpha-ketoglutarate (2)?
  2. ) What mediates this reaction?
A

1.)Alpha-ketoglutarate –> Glutamate (glutamic acid)
Alanine –> Pyruvic acid, an alpha-keto acid
2.) Alanine Transaminase (ALT) and Vitamin B6

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13
Q
  1. ) What are the effects of progestins (2)?

2. ) What are the primary progestins (2)?

A
  1. ) Nidation (implantation), maintenance of pregnancy

2. ) Progesterone, 17-alpha-hydroxy-progesterone

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14
Q

Describe LCAT deficiency

  1. ) Causes
  2. ) Clinical presentation
A
  1. ) An inability to esterify cholesterol, thus, increased total free cholesterol in tissues.
  2. ) Diffuse corneal opacities (fish-eye disease…partial LCAT deficiency), proteinuria with renal failure, hemolytic anemia (increased cholesterol in RBCs = pts may succumb to renal failure).
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15
Q
  1. ) What is the clinical presentation for HYPERAMMONEMIA (5)?
  2. ) Glutamine and astrocytes?
  3. ) Ammonia plasma levels?
A
  1. ) Tremors, lethargy, slurring speech, vomiting, blurred vision
  2. ) Glutamine ALWAYS elevated, astrocyte swelling,
  3. ) ammonia plasma levels 2-3x higher in mild cases, 10x higher in severe
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16
Q

What does SYNTHETASE imply?

A

Use of energy in the form of ATP

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17
Q

After release from the liver, VLDL receives _____ and _____ from ______.

A

VLDL receives C-II and E from HDL.

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18
Q

Explain Glutamate and Ischemia-induced brain damage

A

Last 5 min of Lecture 37

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19
Q

Describe the apoproteins associated with chylomicrons (3):

  1. ) 4 things: Synthesis location, modifications, method of transport
  2. ) 1 thing: Function
  3. ) 2 things: Function, pathology
A
  1. ) ApoB 48: Unique to chylomicrons, synthesized in intestines, glycosylated, MTP loads lipids onto ApoB48 in SMOOTH ER.
  2. ) ApoCII: Activates lipoprotein lipase
  3. ) ApoE3: Needed for recognition by receptor. Presence of ApoE4 isozyme predisposing genetic risk factor for late-onset ALZHEIMER’S.
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20
Q

Where is the main site for ammonia detox?

A

Liver…if you want to LIVE, you need to make UREA in the LIVER

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21
Q

How does LDL synthesis regulation work on the nuclear level under HIGH [cholesterol], i.e. –> 1.) What controls the transcription the enzymes needed for synthesis, and 2.) How does it work (2 steps)?

A

1.) Regulated by Insulin-Induced Gene Products (INSIG): An ER membrane protein.

  1. ) Under high [cholesterol] conditions:
    a. ) INSIG binds SREBP-SCAP and prevents its movement to the Golgi by anchoring it in the ER.
    b. )This prevents movement to the NUCLEUS = NO GENE ACTIVATION OF HMG-CoA REDUCTASE or LDLR GENE.
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22
Q

Before leaving the liver, VLDL is tagged with _______, (which is related to _____…how?)

A

Tagged with ApoB100 –> which is related to Apo-B48 (i.e. translated from the same gene), except Apo-B100 is 100% translated without a STOP CODON in the middle.

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23
Q

Describe Hyperlipidemia Type 4: VLDL, aka ______.

  1. ) Caused by?
  2. ) What is it characterized by?
  3. ) Associated risks?
A

AKA: Hypertriglyeridemia (>200 mg/dL)

  1. ) Overproduction of VLDL, decreased clearance of VLDL, increased [ID] (VLDL remnant).
  2. ) Characterized by: High blood triglyceride levels and obesity, usually with mild DM.
  3. ) Associated with an increased risk for coronary atherosclerosis.
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24
Q
  1. ) Which is present in greater concentration in circulation, glucocorticoids or mineralcorticoids?
  2. ) How do tissues avoid responding to the one with a greater concentration (how do they maintain selectivity)?
A
  1. ) Glucocorticoids
  2. ) They metabolize the higher concentration to an inactive compound, e.g. Cortisol to cortisone in glucocorticoids (carbenoxolone prohibits this effect)
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25
Q

Describe Type 2a Hyperlipidemia, aka ______

  1. ) Genetics?
  2. ) Blood test presentation
  3. ) Clinical presentation
A

AKA Familial Hypercholesterolemia: Deficiency in functioning LDL receptors.

  1. ) Autosomal dominant
  2. ) Elevated LDL and plasma cholesterol (500-800mg/dL cholesterol)
  3. ) Premature atherosclerosis, low tri, xanthomas (lipid deposits) on elbows, knees, ear lobes, around the eyes (xanthelasma), Achilles tendons.
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26
Q

How are branched-chain AA metabolized?

A

In muscle, NOT BY THE LIVER

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27
Q

Describe the function and composition of the four lipoproteins

A
  1. ) Chylomicrons: Triglycerides with some cholesterol. Carry dietary lipids from intestine, to lymph, into the blood stream, and to peripheral tissues.
  2. ) VLDL: Carries hepatic lipids (TG, cholesterol, etc.) from liver to blood.
  3. ) LDL: Carries mainly hepatic cholesterol (reason for just low density) to peripheral tissues.
  4. ) HDL: “Good cholesterol.” Takes cholesterol out of tissues to be stored, or re-synthesized into bile acids, steroids, etc.
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28
Q

What mediates transamination in aspartate? cofactors?

A

Aspartate Transaminase (AST)

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29
Q
  1. ) What is formed by transferring an amino group from aspartic acid (aspartate) to alpha-ketoglutarate (2)?
  2. ) What mediates this reaction?
A

1.) Alpha-ketoglutarate –> Glutamic acid (glutamate)
Aspartic acid (aspartate) –> Oxaloacetate (OAA), an alpha-keto acid
2.) Aspartate Transaminase (AST) and Vitamin B6

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30
Q

What is the most common genetically acquired hyperammonemia?

A

Ornithine transcarbamoylase (x-linked)

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31
Q

What are the main sources for amino acids (3)?

A
  1. ) Dietary protein
  2. ) Body protein (muscle)
  3. ) Metabolic intermediates, e.g. alpha-ketoglutarate for biosynthesis of NON-ESSENTIAL AAs.
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32
Q

Once the steroid diffuses through the membrane into a cell, where does it bind its receptor?

A

Either in the cytoplasm or on the nucleus. Either way, it must get to nucleus to exert its effect.

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33
Q

As VLDL passes through the capillaries, _____ is activated by ______, which hydrolyzes the TG which are released as free FA, and subsequently delivered to peripheral tissues.

A

Lipoprotein lipase is activated by C-II.

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34
Q

In a VERY general sense, what occurs under low [cholesterol] conditions (2)?

A

There is an increase in CHOLESTEROL SYNTHESIS and LDL RECEPTORS

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35
Q

How does cholesterol released from peripheral cells stay inside of the HDL? What does this? What is HDL called afterwards?

A
  • Cholesterol is esterified (hydroxyl group becomes a fatty acid), making it more HYDROPHOBIC.
  • Cholesterol is esterified by ENZYME LECITHIN-CHOLESTEROL ACYLTRANSFERASE (LCAT).
  • It is called HDL2 afterwards (once it has cholesterol ester inside)
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36
Q

a. ) List the effects mineralcorticoids elicit in response to stress (3), and what stimulates their production (2).
b. ) What are the TWO main mineralcorticoids?

A

a.) Mineralcorticoid production stimulated by ACTH and Angiotensin II
Stress responses:
1.) Increased Na+ retention (hypertension)
2.) Increased water retention
3.) Increased Na+ absorption (low salt fluid)

b.) Aldosterone, Deoxycorticosterone

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37
Q
  1. ) What is plaque?
  2. ) What causes it?
  3. ) What combats it (3)?
A
  1. ) Cholesterol deposits along the vascular system (especially in the arteries.
  2. ) Oxidized cholesterol by Reactive Oxygen Species (ROS), smoking, etc.
  3. ) Anti-oxidants, e.g. Vitamin E, ascorbic acid, ß-carotene, etc.
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38
Q

What is a long half-life? Which has the longest?

A

Months or years

Structural proteins have the longest half-lives, e.g. collagen (approximately 1 year).

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39
Q

Describe the 1.) structure and 2.) effects of Lipoprotein(a), aka Lp(a)

A
  1. ) Consists of an LDL-like particle and the specific apo(a) protein. Contains a “kringle” protein motif (looks like a Danish pretzel).
  2. ) Major risk factor for cardiovascular disease and plaque formation. High degree of homology to plasminogen (prevents clot busting).
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40
Q

Amino acid pool is in a ______

A

Steady state

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41
Q

One mole of urea gets rid of HOW MUCH AMMONIA?

A

One urea gets rid of TWO MOLES OF NITROGEN.

approx. 20:30 Lecture 38

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42
Q

What causes fatty liver (aka ______)? In what populations is it found?

A

Fatty liver (aka HEPATIC STEATOSIS): Caused by an imbalance between TRIGLYCERIDE SYNTHESIS and VLDL SECRETION. It is common among the obese, insulin dependent diabetes mellitus (IDDM), and alcoholics.

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43
Q

____ and _____ are released following liver poisoning.

A

ALT and Bilirubin

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44
Q

What is Hartnup Disorder?

A

Cannot absorb nonpolar amino acids, e.g. Trp (MORE?) Trp used for synthesis of SEROTONIN, MELATONIN, and NIACIN.

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45
Q
  1. ) What are the effects of estrogens (5)?

2. ) What are the primary estrogens (3)?

A
  1. ) They promote…Feminization and ESTRUS CYCLE. They INCREASE fat stores and HDL. They also DECREASE testosterone production in MALES.
  2. ) Estradiol, estrone, estriol
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46
Q

What are the sources of endocytosed cholesterol (3)?

A
  1. ) Chylomicron remnant
  2. ) IDL (VLDL remnant)
  3. ) LDL
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47
Q

What AA has the highest concentration in the blood?

Second highest?

A

Highest: Glutamine
Second: Alanine

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48
Q

The stability and vulnerability of lipid-rich plaques are determined by what? What is it composed of?

A

The overlying FIBROMUSCULAR CAP, composed of SMOOTH MUSCLE CELLS and EXTRACELLULAR MATRIX.

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49
Q

A.) Concerning the deamination of D-AMINO ACIDS, what is the:
1.) enzyme
2.) cofactor
3.) products
B.) What amino acid is this reaction mainly used for?

A

A.)

  1. ) D-Amino Acid Oxidase (DAO) –> peroxisomal enzyme
  2. ) FAD
  3. ) Produces: Alpha-keto acids, NH3 (ammonia), H2O2 (peroxide)

B.) D-Serine

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50
Q

The triglycerides in VLDL are bound to _________.

A

Heparin sulfate proteoglycan

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51
Q

What causes hyperammonemic encephalopathy?

A

Cytotoxic brain swelling due to ASTROCYTE SWELLING

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52
Q
  1. ) Describe the Ub-proteasome method for protein degradation
  2. ) How does it work? Energy requirement? When (pre or post-translational)
A

1.) Ubiquitin-proteasome (UPS): Endogenous proteins that mark a protein with ubiquitin, which then tells it to be sent to proteasome for degradation. Nuclear proteins are degraded by a Nuclear Proteasome

  1. ) Ub attaches to amino group on Lys via the C-terminal Gly on Ub
    - Requires ATP
    - Occurs post-translationally
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53
Q

Deficiency in which enzyme would inhibit formation of cortisol and aldosterone, cause ambiguous genitalia, and cause accumulation of 11-deoxycorticosterone (11-DOC)

A

11ß-Hydroxylase Deficiency

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54
Q

Chylomicrons are assembled in the _______. With what?

A

In the ER of the intestines, with TAG, cholesterol esters, phospholipids.

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55
Q
  1. ) Corticosteroid hormone receptors are found in the ________.
  2. ) What keeps it there?
  3. ) What allows it to move to its final destination?
A
  1. ) Cytosol
  2. ) Chaperone or Heat Shock Proteins (HSPs)
  3. ) Binding to the hormone, after which it RELEASES the HSP and the complex migrates to the nucleus.
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56
Q
  1. ) Deficiency in which enzyme would produce diminished urination, hypotension, ambiguous genitalia, hyperpigmented gonads, increased 17alpha-hydroxyprogesterone, and increased Androstenedione?
  2. ) Which hormones are inhibited?
A
  1. ) 21-hydroxylase

2. ) Aldosterone and cortisol

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57
Q

What are the consequences of CARBAMOYL PHOSPHATE SYNTHETASE (CPS, 1st enzyme) and/or ORNITHINE TRANSCARBAMYLASE (OTC, 2nd enzyme) deficiency? What do the blood levels in these deficienies reveal?

A

Blood citrulline levels are very low or absent…If LOW citrulline and HIGH ammonia, DEFICIENCY IS RIGHT AT THE BEGINNING!

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58
Q
  1. ) What are the two major functions of apoproteins in lipoproteins?
  2. ) Where are apoproteins synthesized?
A
  1. ) Provides recognition sites for cell-surface receptors, activates enzyme activity.
  2. ) Most synthesized in the liver, some in the intestine
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59
Q

HDL (ApoA-1) takes up _______ (its main purpose) from ________ and _____

A

HDL takes up UNESTERIFIED CHOLESTEROL (HDL3) from cell membranes and peripheral tissue cells.

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60
Q

The absence of which enzyme inhibits the synthesis of corticosteroids or sex steroids

A

3ß-Hydroxysteroid Dehydrogenase (3ß-HSD)

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61
Q

What deficiency does accumulation of alanine, and finally very high levels of ammonia indicate?

A

N-acetylglutamate synthetase (NAGS)

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62
Q
  1. ) When is the nitrogen balance negative?

2. ) When is the nitrogen balance positive?

A
  1. ) Fasting, fever, burns, wasting diseases

2. ) Growth, tissue repair, pregnancy, post-starvation

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63
Q

Describe the function of CETP (cholesterol ester transfer protein). What is the result of their action?

A

CETP in plasma transfers cholesterol esters from HDL2 (?) to VLDL, while triglycerides and phospholipids are transferred to HDL. The result is that VLDL contains more cholesterol ester, and less TAG. This changes the density of VLDL.

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64
Q

What is the MAJOR regulatory step in the urea cycle?

a. ) What is the energy requirement?
b. ) What compound is necessary for regulation?
c. ) What enzyme is needed?
d. ) Where does this reaction occur?

A

Reaction #1: Carbamoyl Phosphate Synthetase – I(CPSI)

a. ) 2 ATP
b. ) N-acetylglutamate
c. ) N-Acetylglutamate Synthetase
d. ) Mitochondria

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65
Q
  1. ) Deficiency of which enzyme inhibits synthesis of cortisol and sex steroids.
  2. ) What would patients present with (5)?
  3. ) What are the general effects?
A
  1. ) 17alpha-Hydroxylase
  2. ) Infantile genitalia, high BP, low cortisol, inadequate response of cortisol to ACTH, high serum progesterone.
  3. ) Blocks production of sex hormones (ambiguous genitalia in men), reduced aldosterone (but high BP).
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66
Q

What is the release of ammonia used for in the following locations?

  1. ) Liver
  2. ) Kidney
  3. ) Intestines
A
  1. ) Urea synthesis
  2. ) Acid-base balance
  3. ) Added to PORTAL SYSTEM…[NH3] in portal vein is 10x greater than anywhere else in the body
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67
Q
  1. ) What is the name for disorders of steroid biosynthesis?
  2. ) Name them (4)
  3. ) What will their effect be?
A
  1. ) Congenital Adrenal Hyperplasia (CAH)
  2. )
    a. ) 3ß-OH steroid dehydrogenase deficiency
    b. ) 17-Hydroxylase deficiency
    c. ) 21-hydroxylase deficiency
    d. ) 11ß-Hydroxylase deficiency

3.) Decrease in cortisol production = Overproduction of ACTH

68
Q

ALT is relatively specific for _______, and thus is a good diagnostic for _______.

A
  • Relatively specific for LIVER INJURY.

- A good diagnostic for HEPATITIS

69
Q

As blood w/ chylomicrons travel through the capillaries, free fatty acids are delivered to tissue as a result of activation of ________ on the capillary walls recognizing the ________.

A

As a result of LIPOPROTEIN LIPASE recognizing the C-II RECEPTOR on the chylomicrons.

70
Q

What are some symptoms of Cushing’s Syndrome? Caused by?

A 
Moon face (fat face), Hyperglycemia, thin skin. 
-Most caused by adrenal tumor....or overuse of steroids, e.g. Prednisone
71
Q

What are the two most important AA in the blood

A

Alanine and glutamine

72
Q

What is a lipoprotein? Describe the constituents of a lipoprotein (core and outer shell)

A

Lipoprotein: Complexes of lipids and specific proteins (Lipids + Apoprotein)

  • Neutral lipid core: Triacylglycerides and cholesterol esters.
  • Outer shell: Apoprotein (amphipathic), phospholipids (phosphate facing outward), or non-esterified cholesterol (with its cholesterol facing outward).
73
Q

What are the three regions of nuclear receptor proteins? Which region is most homologous across the various types?

A
  1. ) Variable region
  2. ) DNA binding domain
  3. ) Hormone-binding domain
    * The DNA binding domain has the highest degree of homology*
74
Q

_______ is needed on LDL for receptor recognition.

75
Q

Explain the Glucose-Alanine cycle (3 steps)

A
  1. ) Muscle uses protein and creates ammonia which it transfers onto pyruvate –> pyruvate becomes ALANINE.
  2. ) Liver then picks up alanine, removes the amino group from alanine (becomes PYRUVATE) and puts the amino group onto alpha-ketoglutarate (which then becomes glutamate)
  3. ) Glutamate releases the amino group via DEAMINATION and sends it to the UREA CYCLE.
76
Q

What disorders cause over/underproduction of corticosteroids (3)?

A
  1. ) Cushing Syndrome – Overproduction of CORTISOL (glucocorticoid)
  2. ) Addison’s Disease – Underproduction of CORTISOL (glucocorticoid) and ALDOSTERONE (mineralcorticoid)
  3. ) Conn’s Disease – Overproduction of ALDOSTERONE (mineralcorticoid)
77
Q

Give the normal ranges for LFTs

A

AST: 10 - 34 IU/L
ALT: 8 - 37 IU/L

78
Q
  1. ) [HDL2] _________ to the incidence of coronary atherosclerosis, thus….
  2. ) _____ HDL cholesterol puts you at higher risk for heart disease.
A
  1. ) Inversely related.

2. ) LOW HDL

79
Q
  1. ) Give mnemonic for the ESSENTIAL AMINO ACIDS?

2. ) What does essential mean?

A 
1.) PVT TIM HALL always TRies to ARGue
Phe
Val
Thr
Trp
Ile
Met
His (may not be essential in adults) 
Arg (not essential in adults)
Leu (strictly ketogenic)
Lys (strictly ketogenic)
80
Q

What are symptoms of Conn’s syndrome? Treatments?

A

Hypervolemia = Increased: Blood volume (increased Na+), BP, Urine K+ and H+ = Metabolic acidosis

-Treated by: Unilateral adrenalectomy or ALDOSTERONE BLOCKERS

81
Q

What are the two major functions of lipoproteins?

A
  1. ) Transport lipids in SERUM

2. ) Keep lipids soluble in SERUM

82
Q
  1. ) Which hormone(s) regulate the synthesis of ALL adrenal steroid hormones, and where do they come from?
  2. ) Via which type of pathway do they operate?
A
  1. ) *Adrenocorticotropic Hormone/Corticotropin, from the Anterior Pituitary
  2. ) Gs signaling pathway
83
Q

Describe Type 3 Hyperlipoproteinemia, i.e. cause(s), clinical presentation, symptoms.

A

Characterized by ApoE2 apoprotein (ApoE3 is the normal variant), which causes LOW AFFINITY for binding of chylomicron elements –> This causes increased high blood lipid content and HYPERCHOLESTEROLEMIA.
-Lipid deposits primarily located in the PALMAR CREASES (unique to Type 3).

84
Q

How do macrophages recognize LDL in the endothelium, i.e. what receptors are utilized? How are they different from liver receptors?

A

SRA (scavenger receptors): They differ from liver receptors in that SRA have NO REGULATION and will continue to ingest LDL and become completely filled with LDL. They then release growth factors and cytokines, which stimulates migration of smooth muscle cells from the media to the intima, then becoming more foam cells.

85
Q
  1. ) What type of nervous system effect is elicited by angiotensin and ADH?
  2. ) What blocks the effects of these hormones?
A
  1. ) Sympathetic (dry)
  2. ) ACE inhibitors block the formation of Angiotensin II, thereby eliminating all sympathetic response in the renal system.
86
Q

What types of amino acids are alanine, aspartate, glutamic acid?

A

Glucogenic amino acids

87
Q

What is the ultimate consequence of increasing number of foam cells?

A

Foam cells form and are engulfed by the collagen layer they produce. This continues to increase and cause CONSTRICTION OF THE VASCULATURE.
ALSO, collagen can cause clots to form WHEN THE VASCULATURE IS EXPOSED TO COLLAGEN, thereby occluding the vasculature and perhaps BREAKING OFF and causing and EMBOLISM –> if it goes to heart = MI, to brain = STROKE

88
Q

What is the mechanism of LDL oxidation and plaque formation?

A
  1. ) Damage of endothelium (from environmental factors, smoking, or already oxidized LDL etc.) allow PERMEABILITY TO LIPOPROTEINS AND MIGRATION OF CELLS TO UNDERLYING LAYER.
  2. ) Once LDL leaves plasma and enters extracellular space, it becomes VERY SUSCEPTIBLE to OXIDATION OF LIPIDS. Further oxidation of LDL occurs upon arrival in endothelium (intima).
89
Q

What drug treats hyperammonemia by binding Glutamine?

90
Q

The discoidal, nascent HDL contains a surface ______, which was produced in _______.

A

Nascent HDL contains a surface ApoA-1, which was produced in the liver.

91
Q

Give the site of synthesis (from outermost to innermost) and examples (n) for the following classes of adrenal hormones:

  1. ) Mineralcorticoids (2):
  2. ) Glucocorticoids (1):
  3. ) Adrenal androgens (3):
  4. ) Catecholamines (2):
A
  1. ) Mineralcorticoids (2): Zona glomerulosa, e.g. Aldosterone, deoxycorticosterone.
  2. ) Glucocorticoids (1): Zona Fasiculata, e.g. Cortisol, Corticosterone.
  3. ) Adrenal androgens (3): Zona Reticularis, e.g. Dehydroepiandrosterone (DHEA), DHEA sulfate, androstenedione.
  4. ) Catecholamines (2): Medulla, e.g. Epinephrine, norepinephrine.
92
Q

What is the process by which LDL is taken into a cell?

A

Receptor mediated endocytosis

93
Q

What is the function of lipoprotein lipase (LPL) in general and 1.) in the fed state, and 2.) in a fasting state?
3.) Where is [LPL] highest?

A

LPL degrades TAG from chylomicrons to be released into tissue for storage or usage.

  1. ) In the FED STATE, insulin increases and…LPL is increased in ADIPOSE = storage of TAG in adipose, and decreased LPL in muscle.
  2. ) Fasting means DECREASED insulin and…INCREASED LPL in muscle = ENERGY.
  3. ) Highest [LPL] in CARDIAC TISSUE…FA = energy for contraction.
94
Q
  1. ) What is the fate of cholesterol ester inside HDL2 as it returns to the liver?
  2. ) What is the fate of HDL2 after this?
  3. ) What is this entire process called?
A
  1. ) Some of CE is transferred to VLDL via CETP, which becomes LDL, and CE is taken up by the liver.
  2. ) HDL2 is recognized by SCAVENGER RECEPTOR (SRB-1) on liver —-> Then CE is RELEASED TO LIVER —> and HDL2 becomes HDL3.
  3. ) Reverse cholesterol transport
95
Q

What disease will cause protein to be found in feces? What is compromised in the disease?

A

Cystic fibrosis: Mucus plugs pancreatic secretion.

96
Q

Mutations in which region of the nuclear receptor can cause oncogenic transformation?

A

The hormone-binding domain

97
Q

The function of HDL is called _____ ______ _______

A

Reverse cholesterol transport.

98
Q

Nascent chylomicrons receive _____ and ______ in the plasma from circulating _______. At that point, they are considered _______.

A

Receive E and C-II in the plasma from circulating HDL. At that point they are considered MATURE.

99
Q

Summarize “reverse transport of HDL (good cholesterol)” in one phrase, then in FIVE STEPS

A

“Take up cholesterol from non-hepatic (peripheral) tissue, and return it to the liver as cholesterol esters”

  1. ) Efflux of cholesterol from peripheral tissues transport proteins pumped to HDL3.
  2. ) Esterification of cholesterol by LCAT –> HDL2
  3. ) Removal of some CE to VLDL via CETP
  4. ) Binding of HDL2 to liver SR-B1 receptors and other stereogenic cells –> Transfer of CE into these cells for BILE ACID or STEROID SYNTHESIS.
  5. ) Recycling lipid depleted HDL3 into blood.
    (1: 04 lecture 32)
100
Q

Presence/expression of specific receptors on target cells can is determined by what two factors?

A
  1. ) Tissue-specific expression

2. ) Developmentally regulated expression

101
Q

What deficiency do high levels of arginine indicate?

102
Q
  1. ) What is the recommended level of total blood cholesterol for a healthy person?
  2. ) What is the DESIRABLE/IDEAL level?
  3. ) What is borderline high, and high?
A
  1. ) < 200 mg/dL
  2. ) < 130 mg/dL
  3. ) Borderline = 130-159, High = >160 mg/dL
103
Q

What is our main storage source for protein?

A

No special storage form, except… —> MUSCLE

104
Q

The liver recognizes ________ for chylomicron remnant re-uptake. What do the remnants contain at this point?

A

E-3. The remnants are rich in cholesterol ester.

105
Q

What drug is used to treat hyperammonemia by activating CPS 1?

106
Q

a. ) List the effects glucocorticoids elicit in response to stress (4), and what stimulates their production
b. ) What are the TWO main corticosteroids?

A

a.) Glucocorticoid production stimulated by ACTH
Responses to stress:
1.) Increased protein catabolism
2.) Increased gluconeogenesis (increased PEPCK)
3.) Increased apoptosis of T cells (= immunosuppression)
4.) Increased Na+ retention (Hypertension)

b.) Cortisol, Corticosterone

107
Q

What happens to about 40% of cholesterol in LDL?

A

40% carried to extrahepatic tissues for lipid synthesis, e.g. adrenocorticoid, gonads. Used for synthesis of steroids, vitamin D, membranes, etc.

108
Q
  1. ) Give average HDL levels in men
  2. ) Average women
  3. ) An HDL of _____ gives some higher protection against heart disease.
  4. ) HDL < _____ is higher risk.
A
  1. ) 40-50 mg/dL
  2. ) 50-60 mg/dL
  3. ) 60 mg/dL
  4. ) <50mg/dL for women
109
Q

What is the half-life of proteins influenced by (2)? give examples (two for the first)

A
  1. ) N-terminus: Ser = longer half-life, Asp = shorter half-life
  2. ) PEST sequence: Proline (P), Glutamic Acid (E), Serine (S), Threonine (T). PEST functions as a proteolytic signal to target proteins for degradation…thus, SHORTER HALF-LIVES
110
Q
  1. ) How are AA absorbed into the enterocytes?

2. ) How are Di- and Tri-peptides absorbed?

A
  1. ) Na+ secondary active transport: AA enters w/ Na+ and via carrier protein. ATPase on portal side pumps K+ in, and Na+ out.
  2. ) Absorbed via H+ transport at the small intestine brush border: Na+ in and H+ out creates proton gradient. AA enter with H+ via its created gradient.
111
Q

In a VERY general sense, what occurs under HIGH [cholesterol] conditions (2)?

A

Under HIGH [cholesterol], there is a DECREASE in HMG CoA reductase and LDL receptors.

112
Q

Which hormones (and their broad category) are made in the following organs:

  1. ) Testis (2)
  2. ) Ovary (3)
  3. ) Placenta (3)
  4. ) Peripheral tissue (2)
A
  1. ) Testis (Androgens): Androstenedione (produced in gonads and adrenal glands), Testosterone
  2. ) Ovary (Estrogens, androgens): Estradiol (estrogen), androstenedione (androgen), Progesterone.
  3. ) Placenta (Estrogens): Estradiol, estriol, progesterone
  4. ) Peripheral tissue (estrogens): Estrone, estradiol
113
Q

What are the three main ammonia transports in the body? Where from and to?

A

Glutamine: NH3 incorporated into urea
Alanine: Glucose-Alanine cycle from MUSCLE to LIVER
Ammonia: from UREASE (bacteria) –> INTESTINES to LIVER

114
Q
  1. ) What gives VLDL (pre-ß), LDL (ß), HDL (alpha), and chylomicrons their density?
  2. ) What is the largest and most dense of the above lipoproteins?
  3. ) Which is the smallest and most dense?
A
  1. ) Protein, not lipids.
  2. ) Chylomicrons
  3. ) HDL (small, with lots of APOPROTEIN)
115
Q

Which direction is favored for transamination in the following scenarios:

  1. ) After a meal and you are well-fed
  2. ) When AA’s are needed for growth or protein synthesis
  3. ) Fasting
A
  1. ) Amino acids broken down, ammonia –> urea in kidney
  2. ) Alpha-amino group added to alpha-ketoglutarate to make glutamic acid (AA)
  3. ) Muscle protein broken down, carbon skeleton used to make glucose, kidney used to remove ammonia, liver and kidney remove urea
116
Q
  1. ) What happens to the cholesterol released during LDL metabolism?
  2. ) What happens to this process when [cholesterol] is high?
A
  1. ) Prior to transport out of the lysosomes, the cholesterol is esterified for storage by Acyl CoA Cholesterol Acyltransferase (ACAT).
  2. ) Esterification is INCREASED under high [cholesterol] conditions.
117
Q

List the precursors leading up to LDL

A

VLDL –> IDL –> LDL

118
Q

What is BUN? What does high BUN indicate?

A

Blood Urea Nitrogen: Common blood test when looking at renal function. HIGH BUN indicates kidney filtration malfunction.

119
Q

What does Adenosine Deaminase do?

A

Liberates ammonia from NUCLEIC ACIDS

120
Q
  1. ) In the glutamate dehydrogenase reaction, Alpha-KG –> Glu uses _____ and occurs in the ______.
  2. ) Glu –> Alpha-KG uses _____ and occurs in the ______.
A
  1. ) Uses NADPH and occurs in the BRAIN (because the rxn needs electrons)
  2. ) Uses NAD+ and occurs in the LIVER (because the reaction needs to donate electrons)
121
Q

The DNA binding region actually binds as a _____ using ______.

A

Binds as a DIMER, using Zn2+ (Zinc) Finger Motifs.

122
Q

What does D-Serine do?

A

It is a coagonist for endogenous N-methyl D-aspartate receptor (NMDAR), which binds Glu, i.e. D-Serine increases NMDAR affinity for Glu. THIS CAN LEAD TO INCREASED [Glu] and EXCITOTOXICITY

123
Q

What are the two primary mechanisms for production and transfer of ammonia?

A
  1. ) Deamination: Removal of amino group and formation of keto acid, e.g. alpha-ketoglutarate…Amino group then removed as NONTOXIC UREA.
  2. ) Transamination: Transferring amino group between AA to carbon skeleton of AAs. Glutamate removes ammonia in liver, then released as UREA.
124
Q
  1. ) What are the effects of androgens (6)?

2. ) What are the primary androgens (5)?

A
  1. ) They promote…spermatogenesis, virilization (development of secondary sex characteristics), and bone maturation. They also DECREASE fat deposition, and INCREASE muscle mass. They also control aggression.
  2. ) DHEA, DHEA-S, Androstenedione, Testosterone, 5-alpha-Dihydrotestosterone.
125
Q
  1. ) What is the main constituent(s) of LDL? What is comparatively low?
  2. ) What is the most significant apoprotein on LDL, and what other protein does it shares the same gene with?
A
  1. ) Cholesterol and cholesterol esters. It has low triglycerides.
  2. ) ApoB-100. It shares the gene with ApoB-48 (in the intestines), but ApoB-100 is a 100% transcribed version of this gene.
126
Q
  1. ) What is the cause of osteoporosis after menopause?

2. ) What is an effective treatment?

A
  1. ) Menopause causes loss of Estradiol (E2), which inhibits the activation of osteoclasts. Thus, osteoclast activity is increased, causing increased bone resorption.
  2. ) Estrogen replacement therapy after menopause. Less risky PRIOR to age 60.
127
Q

List and describe the steps (4) in conversion of cholesterol to pregnenolone first step of steroid hormone biosynthesis (i.e. location, enzymes, reactants/product/intermediates, and regulation)

A

Conversion of cholesterol to pregnenolone in mitochondria:

a. ) Cholesterol esters broken down in cytosol to cholesterol and FA by…Cholesterol Ester Hydrolase (CEH).
b. ) Cholesterol transported to mitochondria by Steroidogenic Acute Regulatory Protein (StAR).
c. ) Then, P450scc enzyme cleaves cholesterol side chain to produce…PREGNENOLONE.
d. ) Pregnenolone then transported out of mitochondria and into the ER to be converted to steroids.
- Regulation: Hormonal control by PITUITARY HORMONES (positive regulation)

128
Q

ApoB gene RNA editing in the intestines occurs ________

A

Post-translationally (around 34:00 of lecture 32)

129
Q

How are extra degraded protein byproducts used (2)?

A
  1. ) Nitrogen: Removed as urea

2. ) Carbon: Glucogenic or Ketogenic

130
Q

Describe the regulation processes of cholesterol synthesis in conditions of high cholesterol concentration (2 different methods)

A
  1. ) Transcriptional regulation by [cholesterol]
    - Under HIGH [cholesterol]:
    a. ) Decrease in expression of HMG-CoA reductase = DECREASE in DE NOVO (from the beginning) cholesterol synthesis.
    b. ) Decrease in expression of LDL receptors (down regulation) = Decreased cholesterol uptake and increased LDL cholesterol is plasma.
  2. ) Inhibition BY CHOLESTEROL (negative feedback)
    - Under high [cholesterol]: Inhibition of HMG-CoA reductase = decrease in DE NOVO (from the beginning) cholesterol synthesis.
131
Q

What are symptoms of Addison’s disease? Cause?

A

Bronzing of skin, hypoglycemia, changes in distribution of body hair, weight loss, etc.
-It is an autoimmune disorder

132
Q

Concerning TC/HDL ratio, what is:

  1. ) The goal ratio
  2. ) Optimum ratio
  3. ) What does an increased and decreased ratio indicate?
A
  1. ) < 5:1
  2. ) 3.5:1
  3. ) Increased = higher risk of heart disease, decreased = lower risk
133
Q

How does LDL synthesis regulation work on the nuclear level under LOW [cholesterol] conditions, i.e. –> 1.) What controls the transcription the enzymes needed for synthesis, and 2.) How does it work (3 steps)?

A

1.) Controlled by Sterol Regulatory Element-Binding Protein (SREBP2): An integral ER membrane-bound TRANSCRIPTION FACTOR (protein).

  1. ) Under LOW [CHOLESTEROL]:
    a. ) SREBP2 is cleaved from ER and brought to Golgi with SREBP cleavage-activating protein (SCAP).
    b. ) In Golgi, two proteases activate SREBP2, which then moves to the NUCLEUS.
    c. ) In the nucleus, SREBP2 binds to Sterol Binding Element (SRE) upstream from the target genes and INCREASES EXPRESSION of target genes: HMG-CoA reductase, LDL receptor, HMG-CoA reductase.
134
Q

What amino acid has the highest blood concentration?

135
Q

The Urea Cycle involves _____ high energy bonds

136
Q

What induces the urea cycle (2)?

A
  1. ) High protein diet = increased [amino acid] = increased Arg = increase in N-Acetylglutamate = increase in CPS1 = Increase in ORNITHINE in UREA CYCLE and INDUCTION of synthesis of urea enzymes
  2. ) Starvation: HIGH GLUCAGON LEVELS.
    - Breakdown of AA –> glucose (decreases as brain starts to use ketones)
    - Glucagon increases transport of Ala into liver for gluconeogenesis.
137
Q

Excess fatty acids that are converted to TG in the liver are sent via _____ into the blood.

138
Q

All steroid hormones are made from ______

A

Cholesterol

139
Q

Describe the LDL receptors within the membrane of target tissues (two main things)

A
  1. ) LDL receptors are NEGATIVELY CHARGED GLYCOPROTEINS that are clustered in pits on cell membranes.
  2. ) The CYTOSOLIC SIDE of the pit is coated with the protein CLATHRIN, which STABILIZES the pit.
    p. 426
140
Q

ApoCII and ApoE are donated and received back by _______

141
Q

LDLs are recognized by _______ receptor on target tissues. What type of protein?

A

ApoB-100/E, and integral protein in plasma membrane of tissues.

142
Q
  1. ) HDL is mainly formed in ________
  2. ) Chylomicrons made in _______
  3. ) VLDL made in ______
A
  1. ) The blood, to a lesser extent in the intestines and liver.
  2. ) Intestines
  3. ) Liver
143
Q

If urea happens to get into the intestine, how can it become ammonia?

A

via intestinal bacterial UREASE

144
Q
  1. ) How long do steroid hormones generally take to work?

2. ) How do they affect target tissue?

A
  1. ) Slow – Hours to days.
  2. ) They bind to specific receptor proteins in target cells and activate Hormone or Steroid Response Elements (HREs and SREs), which either INCREASE or DECREASE TRANSCRIPTION of specific genes.
145
Q

What is the mechanism for the “morning after pill,” i.e. what does it act upon?

A

Since progesterone is needed for nidation (implantation), the morning after pill is a PROGESTERONE ANTAGONIST that blocks the receptor for progesterone.

146
Q

What purpose can ammonia (NH3) serve in the kidney

A

Induced under acidosis, it can remove excess acid [H+], i.e. buffer, become AMMONIUM, and be excreted as urine.

147
Q

1.) What is a short half-life (in general). What type of proteins have short half-lives (2)? Which has the shortest?

A
  • Minutes or hours*
    1. ) Misfolded proteins
    2. ) Some regulatory proteins
  • Ornithine carboxylase has the shortest (11 minutes)
148
Q

Describe Tangier Disease

  1. ) What is it caused by?
  2. ) Clinical presentation (7)
A
  1. ) Defective ABCA1 transporters (used to transport cholesterol out of the cells)…thus, CHOLESTEROL ESTERS remain inside of the cells and accumulate.
  2. ) Blood hypercholesterolemia, tonsils appear orange-yellow and enlarged, hepatosplenomegaly, MARKEDLY REDUCED HDL levels, neurologic abnormalities (e.g. peripheral neuropathy), clouding of cornea, premature cardiovascular disease.
149
Q

Describe the body’s response to endothelial injury caused by oxidized LDL (3 steps)

A
  1. ) Monocytes adhere to endothelial cells, move to the subendothelium (intima), and are transformed into macrophages.
  2. ) Macrophages consume excess modified (oxidized) lipoprotein (LDL), becoming FOAM cells.
  3. ) Foam cells accumulate, releasing growth factors and cytokines that stimulate the migration of smooth muscle cells from the media to the intima. There, they proliferate, produce collagen, and take up lipid, potentially becoming foam cells.
150
Q

What is the clinical presentation of CYSTINURIA?

A

Defect in reabsorption of BASIC AAs at PROXIMAL TUBULE – These AA then appear in URINE.
*Clinically: High concentration of Cystine in urinary tract = precipitation of cystine = KIDNEY STONES

151
Q

How does a proteasome degrade a protein (4)?

A
  1. ) Proteins tagged with Ub are recognized by the proteasome (a barrel-shaped protein complex)
  2. ) The proteasome unfolds the protein, de-ubiquitinates protein, then degrades it into fragments.
  3. ) Protein further degraded by cytosolic proteases into AMINO ACIDS
  4. ) Ub is recycled
152
Q

Describe Hyperlipidemia Type 5 (four things)

A
  1. ) Combination of hypertriglyceridemia and hyperchylomicronemia.
  2. ) Increased VLDL production.
  3. ) Decreased LPL production
  4. ) Chylomicrons and VLDL are elevated.
153
Q
  • Describe the cleaving specificity for the following proteolytic enzymes and give examples*
    1. ) Trypsin
    2. ) Chymotrypsin
    3. ) Elastase
    4. ) Carboxypeptidase
A
  1. ) Basic AA, e.g. Arg, Lys (KNOW THE BASIC AAs)
  2. ) Bulky AA, e.g. Met, Leu, Phe, Tyr, Trp
  3. ) Small AA, e.g. Ala, Gly, Ser
  4. ) Carboxyl terminus, e.g. Ala, Ile, Leu, Val, or Arg, Lys
154
Q

After a fat-rich meal, the lymph appears ______ due to _______.

A

Appears MILKY due to CHYLOMICRONS.

155
Q

Oxidative deamination occurs most rapidly with _____ via _______ in the liver and kidney.

A

With GLUTAMATE via GLUTAMATE DEHYDROGENASE

156
Q
  1. ) IDL is converted to LDL via what? How does it accomplish this?
  2. ) What receptor is left on the LDL?
A
  1. ) Hepatic triglyceride lipase (HTGL): Removes TG from IDL (which goes on to the liver). Leaving a high concentration of cholesterol (after removing TG) means that there is now LDL.
  2. ) Only B-100 remains on LDL.
157
Q

What is the only location where free AA are found?

A

Portal vein of liver

158
Q

How can neurotransmitters be a source of ammonia?

A

Through MONOAMINE OXIDASE (MAO): They can convert CATECHOLAMINES, e.g. epinephrine, norepinephrine, L-dopa, to ammonia.

159
Q

Describe Type 1 Hyperlipoproteinemia, i.e. what it is called, what is the physiologic cause, symptoms (4)

A

AKA – Familial lipoprotein lipase deficiency = The accumulation of chylomicrons in plasma…causes the following –>

  • Serum appears milky
  • Hypertriacylglyceroemia
  • No lipid deposits
  • Increased risk for acute pancreatitis
160
Q

What is the method extracellular protein degradation?

A

Lysosomal degradation via acid hydrolases

161
Q

What is the role of Vitamin B6 in transamination?

A

It is the intermediate carrier of the amino group.

162
Q
  1. ) What enzyme is involved in TRANSAMINATION?

2. ) What enzyme is involved in DEAMINATION?

A
  1. ) Aminotransferase

2. ) Glutamate Dehydrogenase

163
Q

What is the fate of VLDL after passing through peripheral capillaries (explain as percentages)?

A
  • 50% of VLDL remnant picked up by liver apoE receptor, while some VLDL will become INTERMEDIATE DENSITY LIPOPROTEIN (IDL)…some of which can be endocytosed by liver.
  • other 50% of remnant VLDL will change density from INTERMEDIATE DENSITY LIPOPROTEIN (IDL) to LDL.
164
Q

When will see ALT and AST in the blood stream? Why?

A

When there is LIVER DAMAGE. Why? Because the majority of ALT and AST are in LIVER HEPATOCYTES (intracellularly). Therefore, they are released when after liver injury.

165
Q

What mediates TRANSAMINATION in alanine? Cofactor?

A 
DEAMINATION OF ALANINE
Alanine Transaminase (ALT): Using Vitamin B6 as cofactor.
166
Q

What two treatments for hyperammonemia does Ammonul incorporate?

A

Phenylacetate and Benzoate

Biochem (7 decks)

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