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Step 1 Decks > Biochemistry > Flashcards

Biochemistry Flashcards

1
Q

DNA exists in the ——— form to fit into the ———

A

- Condensed, chromatin

- Nucleus

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2
Q

DNA loops —(number)— around a ——— to form a ——— (nicknamed ———)

A

- twice

- histone octamer

- nucleosome

- (“beads on a string”).

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3
Q

——— binds to the nucleosome and to ———, thereby stabilizing the chromatin fiber

A

- H1

- “linker DNA”

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4
Q

DNA has ——— charge from ———

A

- negative

- phosphate groups

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5
Q

Histones are ——— and have ———charge from ———

A

- large

- positive

- lysine and arginine (Note: LARge)

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6
Q

In mitosis, DNA ——— to form ———

A

- condenses

- chromosomes

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7
Q

DNA and histone synthesis occurs during:

A

S phase

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8
Q

Mitochondria have their own DNA, which is ——— and ———

A

- circular

- does not utilize histones

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9
Q

Heterochromatin is ———, and appears ——— on EM

A

- condensed

- darker

(HeteroChromatin = Highly Condensed)

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10
Q

Heterochromatin is sterically ———, and thus transcriptionally———, ——— methylation and ———acetylation

A

- inaccessible

- inactive

- increased

- decreased

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11
Q

Barr bodies are ———, categorized as —(heterochromatin or euchromatin)—, and may be visible on the ———

A

- inactive X chromosomes

- heterochromatin

- periphery of nucleus

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12
Q

Euchromatin is ———, and appears ——— on EM

A

- less condensed

- lighter

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13
Q

Euchromatin is transcriptionally ———, and sterically ———

A

- active

- accessible

(Euchromatin is Expressed)

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14
Q

DNA methylation changes the ——— without changing the ———

A

- expression of a DNA segment

- sequence

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15
Q

Name 5 processes DNA methylation is involved with :

A

aging, carcinogenesis, genomic imprinting, transposable element repression, and X chromosome inactivation (lyonization)

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16
Q

Methylation within gene promoter (——— ) typically ———

A

- CpG islands

- represses (silences) gene transcription

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17
Q

Dysregulated DNA methylation is implicated in ——— syndrome

A

Fragile X

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18
Q

Histone methylation usually causes ———, but can also cause ——— depending on ———

A

- reversible transcriptional suppression

- activation

- location of methyl groups

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19
Q

——— and ——— residues of histones can be methylate

A

Lysine and arginine

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20
Q

Histone acetylation results in Ž ———, which yields ——— and thus ———

A

- removal of histone’s positive charge

- relaxed DNA coiling Ž 

- increased transcription

(Histone Acetylation makes DNA Active)

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21
Q

——— hormone synthesis is altered by acetylation of ——— receptor

A

- thyroid

- thyroid hormone

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22
Q

Histone deacetylation (removal of acetyl groups) results in ———, and thus ———

A

- tightened DNA coiling Ž 

- decreased transcription

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23
Q

Histone deacetylation may be responsible for altered gene expression in ——— disease

A

Huntington

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24
Q

What is uniparental disomy?

A

Offspring receives 2 copies of a chromosome from 1 parent and no copies from the other parent

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25
Q

What are the two types of uniparental disomy, and what do they each indicate about when a genetic error occurred?

A

1. HeterodIsomy (heterozygous) indicates a meiosis I error

2. IsodIsomy (homozygous) indicates a meiosis II error or postzygotic chromosomal duplication of one of a pair of chromosomes, and loss of the other of the original pair

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26
Q

What might be suggested by an individual manifesting a recessive disorder when only one parent is a carrier?

A

Consider isodisomy

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27
Q

Would someone with uniparental disomy be euploid (correct number of chromosomes)?

A

Yes

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28
Q

Most occurrences of uniparental disomy result in what type of phenotype?

A

Normal

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29
Q

Describe genomic imprinting, and disorders of imprinting:

A

- Genomic imprinting = One gene copy is silenced by methylation, and only the other copy is expressed Ž (parent-of-origin effects)

- Disorders of imprinting: If expressed copy mutated, not expressed, or deleted altogether

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30
Q

What causes Prader-Willis syndrome?

A

Maternally derived genes are silenced; Disease occurs when the paternal allele is deleted or mutated

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31
Q

Name 5 symptoms of Prader-Willis syndrome?

A

Hyperphagia, obesity, intellectual disability, hypogonadism, hypotonia

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32
Q

Which chromosome is involved in Prader-Willis syndrome?

A

Chromosome 15 of paternal origin

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33
Q

How often is uniparental disomy responsible for Prader-Willis syndrome and Angelman syndrome?

A

Prader-Willis syndrome: 25% of cases are due to maternal uniparental disomy

Angelman syndrome: 5% of cases are due to paternal uniparental disomy

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34
Q

What do the mnemonics POP and MAMAS stand for Prader-Willis syndrome and Angelman syndrome?

A

- POP: Prader-Willis, Obesity/overeating, Paternal allele deleted

- MAMAS: Maternal allele deleted, Angelman syndrome, Mood, Ataxia, Seizures

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35
Q

What causes Angelman syndrome?

A

Paternally derived UBE3A is silenced Disease occurs when the maternal allele is deleted or mutated

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36
Q

Name 5 symptoms of Angelman syndrome?

A

Hand-flapping, Ataxia, severe Intellectual disability, inappropriate Laughter, Seizures

(HAILS the Angels)

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37
Q

Which chromosome is involved in Angelman syndrome?

A

UBE3A on maternal copy of chromosome 15

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38
Q

If disease is autosomal recessive,
what is the probability that an unaffected individual with an affected sibling is a carrier?

A

2/3 probability

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39
Q

Cystic fibrosis is the most common lethal genetic disease in patients with:

A

European ancestry

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40
Q

What is the genetic cause of cystic fibrosis?

A

Autosomal recessive; defect in CFTR gene on chromosome 7 (deletion; ΔF508)

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41
Q

What does the CFTR gene encode and what is its function?

A

CFTR encodes an ATP-gated Cl− channel (secretes Cl− in lungs/GI tract, reabsorbs Cl− in sweat glands)

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42
Q

Describe the pathophysiology of cystic fibrosis:

A

- Phe508 deletion —>
- misfolded protein Ž —>
- improper protein trafficking Ž—>
- protein absent from cell membrane—>
- decreased Cl− (and H2O) secretion->
- increased compensatory  Na+ reabsorption via epithelial Na+ channels (ENaC) Ž —> 
- increased H2O reabsorption Ž—>
- abnormally thick mucus secreted into lungs/GI tract

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43
Q

In cystic fibrosis, more ———reabsorption = more ——— transepithelial potential difference

A

- Na+ reabsorption

- negative transepithelial potential difference

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44
Q

Name 3 clues for cystic fibrosis diagnosis:

A

1. Increased Cl− concentration in pilocarpine-induced sweat test

2. Can present with contraction alkalosis and hypokalemia (ECF effects analogous loop diuretic effect) due to ECF H2O/Na+ losses via sweating and concomitant renal K+ /H+ wasting

3. Immunoreactive trypsinogen (newborn screening) due to clogging of pancreatic duct

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45
Q

List 4 key pulmonary manifestations of cystic fibrosis:

A

1. Recurrent pulmonary infections (eg, S aureus [infancy and early childhood], P aeruginosa [adulthood], allergic bronchopulmonary aspergillosis [ABPA])

2. Chronic bronchitis and bronchiectasis Ž—> reticulonodular pattern on CXR, opacification of sinuses

3. Nasal polyps

4. Nail clubbing

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46
Q

List 7 key GI manifestations of cystic fibrosis:

A

1. Pancreatic insufficiency

2. Malabsorption with steatorrhea

3. Fat-soluble vitamin deficiencies (A, D, E, K)

4. Progressing to endocrine dysfunction (CF-related diabetes)

5. Progressing to biliary cirrhosis

6. Progressing to liver disease

7. Meconium ileus in newborns

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47
Q

List key male and female reproductive manifestations of cystic fibrosis:

A

- Infertility in males (absence of vas deferens, spermatogenesis may be unaffected)

- Subfertility in females (amenorrhea, abnormally thick cervical mucus).

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48
Q

List 3 treatments for improved mucus clearance in cystic fibrosis:

A

1. Chest physiotherapy

2. Aerosolized dornase alfa (DNase)

3. Inhaled hypertonic saline

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49
Q

List treatment to prevents acute exacerbations in cystic fibrosis:

A

Azithromycin

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50
Q

List treatment used for anti-inflammatory effect in cystic fibrosis:

A

Ibuprofen

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51
Q

List a treatment for pancreatic insufficiency in cystic fibrosis:

A

Pancreatic enzyme replacement therapy (pancrelipase)

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52
Q

Describe the overall use and 2 mechanisms/examples of CFTR modulators:

A

- Can be used alone or in combination for treatment of cystic fibrosis

- Efficacy varies by different genetic mutations (pharmacogenomics)

Mechanisms:
- Potentiators (hold gate of CFTR channel open Ž—> Cl− flows through cell membrane; eg, ivacaftor)

- Correctors (help CFTR protein to form right 3-D shape Ž—> moves to the cell surface; eg, lumacaftor, tezacaftor)

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53
Q

Name a condition that would make females more likely to have an X-linked recessive disorder

A

Turner syndrome (45,XO)

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54
Q

Describe X-inactivation (lyonization), and what can happen if skewed inactivation occurs:

A

Description:
During development, one of the X chromosomes in each XX cell is randomly deactivated and condensed into a Barr body (methylated heterochromatin)

If skewed inactivation occurs:
XX individuals may express X-linked recessive diseases (eg, G6PD); penetrance and severity of X-linked dominant diseases in XX individuals may also be impacted

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55
Q

What is the mode of inheritance for Duchenne muscular dystrophy?

A

X-linked recessive disorder

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56
Q

Duchenne muscular dystrophy is typically due to ——— or ———, resulting in ——— protein and ——— damage

(Can also result from ———)

A

- frameshift deletions or nonsense mutations

- truncated or absent dystrophin protein and progressive myofiber damage

- splicing errors

(Duchenne = Deleted Dystrophin)

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57
Q

Why is the gene involved in Duchenne muscular dystrophy susceptible to spontaneous mutations?

A

Dystrophin gene (DMD) is the largest protein-coding human gene; thus has an increased chance of spontaneous mutation

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58
Q

What is the usual role of the protein involved in Duchenne muscular dystrophy, and what does this proteins loss lead to in this disease?

A

- Dystrophin helps to anchor muscle fibers to the extracellular matrix, primarily in skeletal and cardiac muscles

- Loss of dystrophin Žleads to myonecrosis

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59
Q

How can Duchenne muscular dystrophy be diagnosed?

A

- Elevated creatine kinase and aldolase

- Genetic testing confirms diagnosis

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60
Q

List 5 key symptoms of Duchenne muscular dystrophy:

A

- Weakness that begins in pelvic girdle muscles and progresses superiorly

- Pseudohypertrophy of calf muscles due to fibrofatty replacement of muscle

- Waddling gait

- Lordosis

- Thigh atrophy

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61
Q

In what age range does Duchenne muscular dystrophy typically onset?

A

Onset before 5 years of age

62
Q

The common cause of death in Duchenne muscular dystrophy is:

A

Dilated cardiomyopathy

63
Q

List a classical sign of Duchenne muscular dystrophy, and list a few other conditions that may also have this sign:

A

- Gowers sign—patient uses upper extremities to help stand up (eg, pushes on legs to stand)

- Also seen in other muscular dystrophies and inflammatory myopathies (eg, polymyositis).

64
Q

What is the mode of inheritance for Becket muscular dystrophy?

A

X-linked recessive disorder

65
Q

Becket muscular dystrophy is typically due to ——— in ——— gene (leading to ——— instead of ———)

A

- non-frameshift deletions

- dystrophin gene

- partially functional instead of truncated

66
Q

Contrast the severity of Becker and Duchenne muscular dystrophy:

A

Becker less severe than Duchenne

(Becker is Better)

(Deletions can cause both Duchenne and Becker muscular dystrophies. 2 ⁄3 of Becker cases have large deletions spanning one or more exons.)

67
Q

In what age range does Becker muscular dystrophy typically onset?

A

Onset in adolescence or early adulthood

68
Q

What is the mode of inheritance for myotonic dystrophy?

A

Autosomal dominant

69
Q

In what age range does myotonic dystrophy typically onset?

A

Onset 20–30 years

70
Q

Myotonic dystrophy caused by ——- in the ——— gene Žleading to abnormal expression of ———

A

- CTG trinucleotide repeat expansion

- DMPK gene Ž

- Myotonin protein kinase

71
Q

List 6 key symptoms of myotonic dystrophy:

A

- myotonia (eg, difficulty releasing hand from handshake)

- muscle wasting

- cataracts

- testicular atrophy

- frontal balding

- arrhythmia

(CTG = Cataracts, Toupee (early balding in males), Gonadal atrophy)

72
Q

In the electron transport chain/ oxidative phosphorylation, NADH electrons are transferred to ——— FADH2 electrons are transferred to——— (—NADH or FADH2— at a lower energy level than —NADH or FADH—)

A

- complex I (NADH to NAD+)

- complex II (succinate dehydrogenase) (FADH2 to FAD)

- FADH2

-NADH

73
Q

In the electron transport chain, the passage of ——— results in the formation of a ——— that, coupled to oxidative phosphorylation, drives ———

A

- electrons

- proton gradient

- ATP production

74
Q

——— can be coupled to energetically unfavorable reactions

A

ATP hydrolysis

75
Q

Uncoupling proteins (found in ——— fat, which has more mitochondria than ——— fat) produce ——— by  ——— which Ž——— (——— stops, but ——— continues)

A

- brown

- white

- heat

- increasing inner mitochondrial membrane permeability

- decreased the proton gradient

- ATP synthesis stops

- electron transport continues

76
Q

How many ATP are produced by 1 NADH? How many ATP are produced by 1 FADH2?

A

1 NADH produces 2.5 ATP

1 FADH2 produced 1.5 ATP

77
Q

NADH electrons from glycolysis enter mitochondria via the ——— or the ———

A

malate-aspartate or glycerol-3-phosphate shuttle

78
Q

Aerobic metabolism of one ——— molecule produces ——— net ATP via ——— shuttle (in ———), ——— net ATP via ——— shuttle (in ———)

A

- glucose

- 32

- malate-aspartate

- heart and liver

- 30

- glycerol-3-phosphate

- muscle

79
Q

Anaerobic glycolysis produces ———net ATP per ——— molecule.

A

- 2

- glucose

80
Q

——— overdose can also cause uncoupling of oxidative phosphorylation resulting in ———

A

- Aspirin

- hyperthermia

81
Q

Mitochondrial diseases are rare disorders arising 2° to failure in ———

A

- oxidative phosphorylation

82
Q

Among mitochondrial diseases, tissues with ——— are preferentially affected (eg, ——— and ——— tissue)

A

- increased energy requirements

- CNS, skeletal muscle

83
Q

List two key mitochondrial myopathies:

A

MELAS (mitochondrial encephalomyopathy with lactic acidosis and strokelike episodes)

MERRF (myoclonic epilepsy with ragged red fibers)

84
Q

What is observed in mitochondrial myopathies (MELAS and MERRF) on light microscopy with stain and electron microscopy?

A

- Light microscopy with stain: ragged red fibers (due to compensatory proliferation of mitochondria)

- Electron microscopy: mitochondrial crystalline inclusions

85
Q

Leber hereditary optic neuropathy is caused by:

A

mutations in complex I of ETC

86
Q

Leber hereditary optic neuropathyŽ results in —(cell type)— death in ——— and ———, which results in main symptom of ——— in —(age group)—

A

- neuronal

- retina and optic nerve

- subacute bilateral vision loss

- teens/young adults

87
Q

Is Leber hereditary optic neuropathy more common among males or females?

Is it usually transient or permanent?

What type of dysfunction is it usually accompanied by, and list 2 examples of such dysfunction?

A

- males > females

- usually permanent

- neurologic dysfunction (eg, tremors, multiple sclerosis–like illness)

88
Q

Rett syndrome is a sporadic disorder caused by:

A

de novo mutation of MECP2 on X chromosome

89
Q

Rett syndrome is seen most with which gender, and why?

A

Seen mostly in females.
Embryonically lethal in males.

90
Q

Describe the developmental timeline for Rett syndrome, and name 4 key symptoms:

A

Developmental timeline:
Initial normal development (6–18 months) followed by regression (“RETTurn”) in motor, verbal, and cognitive abilities

Key symptoms:
Ataxia, seizures, scoliosis, and stereotypic hand-wringing.

91
Q

What is the mode of inheritance in Fragile X syndrome?

A

X-linked dominant inheritance

92
Q

Fragile X syndrome is caused by a ——— in ——— Žwith ——— residues Ž  resulting in ——— expression

A

- Trinucleotide repeat expansion [(CGG)n]

- FMR1 Ž

- hypermethylation of cytosine residues Ž 

- decreased expression

93
Q

What is the most common genetic cause of intellectual disability?
What is the most common inherited cause of intellectual disability?

A

Down syndrome is most common genetic cause, but most cases occur sporadically

Fragile X syndrome is the most common inherited cause of intellectual disability

94
Q

What is the cause of Fragile X syndrome and when does it occur?

A

Trinucleotide repeat expansion [(CGG)n] occurs during oogenesis

95
Q

For Fragile X syndrome, what are the number of repeats and symptoms associated with premutation and full mutation?

A

Premutation (50–200 repeats): Ž tremor, ataxia, 1° ovarian insufficiency

Full mutation (>200 repeats): postpubertal macroorchidism (enlarged testes), long face with large jaw, large everted ears, autism, mitral valve prolapse, hypermobile joints

96
Q

In Fragile X syndrome, —(symptom)— is common and can be confused with ——— syndrome

A

- Self-mutilation

- Lesch-Nyhan syndrome

97
Q

Trinucleotide repeat expansion diseases may show genetic anticipation meaning that:

A

disease severity increases and age of onset decreases in successive generations

98
Q

For Huntington disease, Myotonic dystrophy, Fragile X syndrome, Friedreich ataxia, what is the associated trinucleotide repeat expansion, mode of inheritance, and mnemonic?

A

Huntington disease:
- (CAG)n
- Autosomal Dominant
- CAG =Caudate has decreased ACh and GABA (increased dopamine)

Myotonic dystrophy:
- (CTG)n
- Autosomal Dominant
- CTG = Cataracts, Toupee (early balding in males), Gonadal atrophy in males, reduced fertility in females

Fragile X syndrome:
- (CGG)n
- X-linked Dominant
- CGG = Chin (protruding), Giant Gonads

Friedreich ataxia:
- (GAA)n
- Autosomal Recessive
- ataxic GAAit

99
Q

Autosomal trisomies are screened in ——— trimesters with noninvasive prenatal tests

A

first and second

100
Q

Relative incidence of trisomies 13, 18, and 21:

A

Down (21) > Edwards (18) > Patau (13)

101
Q

Why are autosomal monosomies not seen?

A

Incompatible with life (high chance of recessive trait expression)

102
Q

Name 10 key findings in Downs Syndrome:

A

- intellectual disability

- flat facies

- prominent epicanthal folds

- single palmar crease

- incurved 5th finger

- gap between 1st 2 toes

- duodenal atresia

- Hirschsprung disease

- congenital heart disease (eg, AVSD)

- Brushfield spots (whitish spots at the periphery of the iris)

103
Q

Name 3 conditions that individuals with Downs Syndrome are at higher risk of developing:

A

- Early-onset Alzheimer disease (chromosome 21 codes for amyloid precursor protein)

-AML

-ALL

104
Q

When nondisjunction occurs in meiosis I vs meiosis II, what are the results in terms of chromosome numbers?

A

Nondisjunction in meiosis I:
- 2 monosomy
- 2 trisomy

Nondisjunction in meiosis II:
- 2 normal
- 1 monosomy
- 1 trisomy

105
Q

95% of cases of Down syndrome are due to ———, most commonly ——— ( with increased risk associated with ———); 4% of cases due to ———, most typically between ———; and, 1% of cases due to ———

A

- meiotic nondisjunction

- during meiosis I

- advanced maternal age

- unbalanced Robertsonian translocation

- chromosomes 14 and 21

- postfertilization mitotic error


-

106
Q

What is a Robertsonian translocation?
(One of the most common types of translocation)

A

Occurs when the long arms of 2 acrocentric chromosomes (chromosomes with centromeres near their ends) fuse at the centromere and the 2 short arms are lost

107
Q

Balanced translocations result in ———, and relative to phenotype ———

A

- no gain or loss of significant genetic material

- normally do not cause abnormal phenotype

108
Q

Unbalanced translocations result in ———, and relative to phenotype ———

A

- missing or extra genes

- can result in miscarriage, stillbirth, and chromosomal imbalance (eg, Down syndrome, Patau syndrome)

109
Q

Robertsonian translocation commonly involves which 5 chromosome pairs?

A

21, 22, 13, 14, and 15

(Note: 1, 2, 3, 4, 5)

110
Q

What is the most common viable chromosomal disorder and most common cause of genetic intellectual disability?

A

Down syndrome

111
Q

With Down syndrome, first-trimester ultrasound commonly shows which two findings?

A

- increased nuchal translucency and hypoplastic nasal bone

112
Q

Markers for Down syndrome:

A

Increased hCG and increased inhibin
(hi up)

113
Q

With Down syndrome, there is an increased risk of what type of hernia?

A

 - umbilical hernia (incomplete closure of umbilical ring)

114
Q

List the 5 A’s of Down syndrome:

A

- Advanced maternal age ƒ
- Atresia (duodenal) ƒ
- Atrioventricular septal defect ƒ
- Alzheimer disease (early onset) ƒ
- AML (<5 years of age)/ALL (>5 years of age)

115
Q

List 10 key features of Edwards syndrome (trisomy 18):

A

- Prominent occiput

- Rocker-bottom feet

- Intellectual disability

- Nondisjunction

- Clenched fists with overlapping fingers

- low-set Ears

(PRINCE Edward)

- micrognathia (small jaw)

- congenital heart disease (eg, VSD)

- omphalocele

- myelomeningocele

116
Q

In Edwards syndrome (trisomy 18), death usually occurs by age———

A

One

117
Q

What are the two most common autosomal trisomy resulting in live birth?

A

Most common Down syndrome followed by Edwards syndrome

118
Q

List 11 key features of Patau syndrome (trisomy 13):

A

- severe intellectual disability

- rockerbottom feet

- microPhthalmia

- microcePhaly

- cleft liP/Palate

- holoProsencephaly

- Polydactyly

- cutis aPlasia

- congenital heart (Pump) disease

- Polycystic kidney disease

- Omphalocele

119
Q

In Patau syndrome (trisomy 13), death usually occurs by age———

A

One

120
Q

Patau syndrome associated with defect in fusion of ——— Žresulting in ———

A

- prechordal mesoderm

- midline defects

121
Q

Name 2 important 1st trimester screening tests for trisomy 21, 18, and 13; and their findings for each trisomy:

A

β-hCG:
- increased with Down syndrome
- decreased with Edward and Patau syndrome

PAPP-A:
- decreased with Down, Edward, and Patau syndrome

(In EDwards syndrome, every prenatal screening marker Decreases )

122
Q

Name 4 important 2nd trimester screening tests for trisomy 21, 18, and 13; and their findings for each trisomy:

A

hCG:
- increased with Down syndrome
- decreased with Edward syndrome
- unchanged with Patau syndrome

Inhibin A:
- increased with Down syndrome
- decreased or unchanged with Edward syndrome
- unchanged with Patau syndrome

Estriol:
- decreased with Down and Edward syndrome
- unchanged with Patau syndrome

AFP:
- decreased with Down and Edward syndrome
- unchanged with Patau syndrome

(In EDwards syndrome, every prenatal screening marker Decreases )

123
Q

What is the full name of vitamin D3 vs D2 and where is each produced?

A

D3 Name: cholecalciferol

D3 Produced from: exposure of skin (stratum basale) to sun, ingestion of fish, milk, plants

D2 Name: ergocalciferol

D2 Produced from: ingestion of plants, fungi, yeasts

124
Q

Vitamin D2 and D3 are both converted to ——— (storage form) in ——— (associated enzyme ———) and to the active form ——— (called ———) in ———(associated enzyme ———)

A

- 25-OH D3

- liver

- 25-hydroxylase

- 1,25-(OH)2 D3 (called calcitriol)

- kidney

- 1α-hydroxylase

125
Q

List the 3 key functions of vitamin D:

A

- increase intestinal absorption of Ca2+ and PO4 3– (increased release from bone, increased absorption in intestines, and increased reabsorption in renal tubular cells (thus decreased in urine))

- increase bone mineralization at low levels (calcium and phosphate when present together in the blood bond very well to each other and they then mineralise or precipitate into the bone)

- increase bone resorption at higher levels

126
Q

Low calcium and low phosphate stimulates ———; When calcium is low, it triggers ——— to be released, which activates the ———

A

- 1 alpha hydroxylase

- parathyroid hormone (PTH)

- 1 alpha hydroxylase

127
Q

1,25-(OH)2D3 production is increased by what and decreased by what:

A

- increased by: increased PTH, and decreased Ca2+, PO4 3– Ž 

- decreased by: 1,25-(OH)2D3 feedback (inhibits its own production)

128
Q

Increased PTH Ž has what effect on reabsorption in the kidneys?

A

Increased Ca2+ reabsorption and  decreased PO4 3– reabsorption in the kidney

129
Q

List 3 conditions that result from vitamin d deficiency:

A

- Rickets in children (deformity, such as genu varum “bowlegs”)

- osteomalacia in adults (bone pain and muscle weakness)

- hypocalcemic tetany

130
Q

List 5 causes of vitamin d deficiency:

A

- malabsorption

- lack of sun exposure

- poor diet

- chronic kidney disease (CKD)

- advanced liver disease

131
Q

List 2 factors that predispose to vitamin d deficiency:

A

Darker skin and prematurity

132
Q

Provision of oral vitamin D is important for:

A

breastfed infants

133
Q

Excess vitamins d cause what 4 findings:

A

- hypercalcemia

- hypercalciuria

- loss of appetite

- stupor

134
Q

Vitamin d excess is observed in ——— (due to increased activation of vitamin D by ———)

A

- granulomatous diseases

- epithelioid macrophages

135
Q

Lipoproteins are composed of varying proportions of —(4 components)—; LDL and HDL carry the most ———

A

- proteins, cholesterol, TGs, and phospholipids

- cholesterol

136
Q

List 4 key functions of cholesterol:

A

- maintain cell membrane integrity

- synthesize bile acids

- synthesize steroids

- synthesize vitamin D

137
Q

Chylomicron are secreted by:

A

intestinal epithelial cells

138
Q

Chylomicron deliver ——— to ———, as well as delivering ——— to ——— in the form of ———, which are mostly depleted of their ———

A

- dietary TGs

- peripheral tissues

- cholesterol

- liver

- chylomicron remnants

- TGs

139
Q

VLDL are secreted by:

A

liver

140
Q

VLDL deliver ——— to ———

A

- hepatic TGs

- peripheral tissue

141
Q

IDL is formed from:

A

degradation of VLDL

142
Q

IDL delivers ——— to ———

A

- TGs and cholesterol

- liver

143
Q

LDL is formed by ——— modification of ——— in the ———

A

- hepatic lipase

- IDL

- liver and peripheral tissue

144
Q

LDL delivers ——— to ———; Taken up by target cells via ———

A

- hepatic cholesterol

- peripheral tissues

- receptor-mediated endocytosis

145
Q

HDL is secreted from both ———; ——— increases synthesis

A

- liver and intestine

- alcohol

146
Q

HDL mediates ——— transport from ——— to ———

A

- reverse cholesterol

- peripheral tissues

- liver

147
Q

HDL acts as a repository for ——— and ——— (which are needed for ———)

A

- apoC

- apoE

- chylomicron and VLDL metabolism

148
Q

List function of apoE and where it is present:

A

Function:
Mediates remnant uptake (everything except LDL)

Present on:
Chylomicron, Chylomicron remnant, VLDL, IDL, HDL

149
Q

List function of apoA1 and where it is present:

A

Function:
Found only on alphalipoproteins (HDL), activates LCAT (lecithin-cholesterol acyltransferase = Catalyzes esterification of 2 ⁄3 of plasma cholesterol (ie, required for HDL maturation))

Present on:
HDL

150
Q

List function of apoCII and where it is present:

A

Function:
Lipoprotein lipase Cofactor that Catalyzes Cleavage

Present on:
Chylomicron, VLDL, IDL, HDL

151
Q

List function of apoB48 and where it is present:

A

Function:
Mediates chylomicron secretion into lymphatics; Only on particles originating from the intestines

Present on:
Chylomicron, Chylomicron remnant

152
Q

List function of apoB100 and where it is present:

A

Function:
Binds LDL receptor; Only on particles originating from the liver (I hope I live to Be 100)

Present on:
VLDL, IDL, LDL

Step 1 Decks (8 decks)

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