Biochemistry - Cellular Structure & Biomechanics Block (II) Flashcards
A deficiency of what enzyme will lead to types A and B Niemann-Pick disease?
Acid sphingomyelinase
What substance builds up in Niemann-Pick disease types A and B?
This results in what type of cell?
Sphingomyelin;
foam cells
In what organ systems are foam cells found in cases of Niemann-Pick disease?
The spleen, liver, and CNS
What disease is characterized by acid sphingomyelinase defects and associated foam cell deposits in the CNS, spleen, and liver?
Niemann-Pick disease types A and B
Cytokine-related overactivation of what enzyme may contribute to development of multiple sclerosis?
Acid sphingomyelinase
Defects in acid sphingomyelinase lead to what disease?
Overactivation of acid sphingomyelinase may lead to what disease?
Niemann-Pick disease (types A and B);
multiple sclerosis
What effect does excess sphingomyelin have on erythrocytes?
This is commonly seen in what disease?
Acanthocytosis;
abetalipoproteinemia
What is a hematologic result of abetalipoproteinemia?
This is due to an excess of what lipid?
Acanthocytosis;
sphingomyelin
How does abetalipoproteinemia appear on a peripheral smear?
This is due to a defect involving what substance?
Acanthocytosis;
sphingomyelin (on the RBC E-face)
Cystic fibrosis involves transport of what ion into the mucus?
Chloride
What are the three main organs affected by cystic fibrosis?
Lungs, pancreas, liver
Absence of chloride movement in cystic fibrosis leads to what effect on the mucus?
Less H2O movement –> thick, dry mucus
Cystic fibrosis results as a genetic mutation in which channel?
The gene for this channel is found on which chromosome?
The CFTR
(cystic fibrosis transmembrane regulator);
7
A young child presents with progressive muscle weakness and new cardiac arrythmias. You suspect myotonic dystrophy.
What genetic results would confirm your suspicions?
CTG repeats
(in the DMPK gene on chromosome 19)
A man presents with microcephaly, cognitive deficits, indistinct philtrum, epicanthal folds, a low nasal bridge, and a short nose.
What do you suspect?
What cellular mechanism caused the issue?
Fetal alcohol syndrome;
impaired lipid rafts and signaling proteins
What effect does phalloidin (found in death cap mushrooms) have on cellular structures?
(What is the primary clinical presentation)
Stabilizes F-actin (prevents its degradation)
(acute, extreme hunger due to liver necrosis)
Cytochalasins mess with microfilaments and cause what outcome?
Apoptosis
Hereditary spherocytosis is caused by a deficiency of what protein(s)?
Spectrin, ankyrin, or band-3 proteins
Primary ciliary dyskinesia (immotile cilia syndrome) is an autosomal recessive disease known by what other name and caused by a defect in the gene coding for what protein?
Kartagener’s syndrome;
axonemal dynein
How does Kartagener’s syndrome present?
Chronic respiratory infections, situs inversus, infertility
With what cytoskeletal element does colchicine interact? How?
With what cytoskeletal element do vincristine and vinblastine interact? How?
With what cytoskeletal element does paclitaxel interact? How?
Microtubules, inhibits polymerization;
microtubules, inhibits polymerization;
microtubules, inhibits depolymerization
What stain would be most useful in diagnosing the most common type of primary brain tumor?
GFAP
(astrocytomas)
A two-year-old female toddler presents with steady loss of cognitive ability. Her father notes that she seemed cognitively normal and met all her milestones up until she was 18 mo. of age. You notice her near constant hand wringing.
What is the likely diagnosis?
Rett syndrome
What biochemical defect can lead to Rett’s syndrome?
Mutations in MECP2
(this HDAC-recruiting protein -MECP2- is no longer available upon histone methylation);
leading to inappropriate gene expression
(manifesting clinically as cognitive decline and persistent hand wringing)
Mutation in the MECP2 gene has what effect?
What is this condition called?
A lack of MECP2 protein –> inability to recruit HDAC –> inability to condense DNA –> excessive gene expression;
Rett’s syndrome
How does Rett syndrome typically present in the clinic?
Cognitive decline
(after ~18 mo. of seemingly normal childhood development);
hand wringing
An embryo is missing one autosomal chromosome. What will the result be?
This is a lethal mutation
An embryo is missing one chromosome and is 45,XO. What will the result be?
Turner’s syndrome
What are some clinical presentations of Turner’s syndrome?
Webbed neck,
widely spaced nipples,
swollen hands and feet,
short stature,
widespread nevi
Are individuals with Turner’s syndrome female or male?
Female
What is the most common human trisomy?
How does it present?
Trisomy 16;
it is lethal
(fetal death in the first trimester)
What is the most common birth defect?
How does it present?
Trisomy 21;
Down syndrome
What is unique about the 21st chromosome?
It is the smallest autosome
Do viable (non-lethal) trisomies usually happen in large or small autosomal chromosomes?
Small
Patau’s syndrome is caused by what defect?
Trisomy 13
Edward’s syndrome is caused by what defect?
Trisomy 18
Trisomy of what chromosome in particular leads to fetal death in the first trimester?
Trisomy 16
Trisomy 16 is incompatible with life and results in fetal death at what point?
The first trimester
The sphingomyelin affected in abetalipoproteinemia is found in which leaflet of the plasma membrane?
The E-face
Defects in occludins may result in severe neurological disorders do to disruption of what structure(s)?
The fetal blood-brain barrier (tight junctions disrupted)
Loss of expression of what protein can disrupt the zona adherens and lead to increased malignancy and invasiveness of a developing carcinoma?
E-cadherins
Autoimmunity against the protein desmoglein I can lead to skin disorders characterized by reduced intercellular cohesion of what in particular?
This is due to disruption of what epithelial cell junction?
Epidermal cells
Macula adherens (desmosome)
Mutations of what protein are related to types of epidermolysis bullosa (blistering skin lesions)?
This is due to disruption of what?
Keratins 5 and 14;
hemidesmosomes
Mutations in various connexin genes have been linked to what issues?
This is due to a defect in what type of cell junction?
Peripheral neuropathy and deafness
(both in very specific situations, not just any PN and deafness);
gap junctions
What pathogens act on proteins of the zona occludens to make cell junctions more permeable?
Cholera toxin;
CMV
Cholera toxins and CMV both act on what structure to increase permeability between cells?
The zona occludens
What disease is characterized by antibody attacks on proteins of the hemidesmosome?
What disease is characterized by antibody attacks on the desmosome (specifically desmoglein I and III)?
Bullous pemphigoid;
pemphigus vulgaris
Antibody attacks on what might cause bullous pemphigoid?
Hemidesmosome proteins
Antibody attacks on what might cause pemphigus vulgaris?
Proteins of the desmosome
(e.g. desmoglein I and III)
Define aneusomy.
What are the three types?
Aberrant number of chromosomes (due to loss or addition);
nullisomy, monosomy, trisomy
Define euploidy.
Correct number of chromosome pairs
What is the term if an embryo is missing both chromosomes of one chromosomal pair?
What is the term if an embryo is missing one chromosome of a chromosomal pair?
What is the term if an embryo has both chromosomes of one chromosomal pair?
What is the term if an embryo has an extra chromosome in addition to one chromosomal pair?
Nullisomy (-2);
monosomy (-1);
eusomy (-0; just right);
trisomy (+1);
What will happen to an embryo with nullisomy of any chromosomal pair?
Embryonic death
What will happen to an embryo with monosomy of any autosomal chromosome pair?
Embryonic death
What is the only survivable true monosomy?
Turner’s syndrome
(any other survivable monosomy is only a partial deletion of a chromosome)
What is the term if an embryo has three entire, homologous sets of chromosomes?
What is the term if an embryo has four entire, homologous sets of chromosomes?
Triploidy;
tetraploidy
Which usually presents earlier in life, aneuploidy or chromatin remodeling abnormalities?
Aneuploidy
What is the typical treatment for Turner’s syndrome?
To address what issues?
Hormonal therapy (GH and estrogen);
the slow growth and lack of sexual development
True/false.
Trisomies of the sex chromosomes (e.g. XXX, XXY, XYY) are all typically associated with only minor problems and a full life span.
True
Which type of autosomal trisomy is most likely to result in a viable fetus?
Those of small autosomes (e.g. 13, 18, 21)
What is the most common human trisomy?
How does it present?
Chromosome 16;
fetal death in the first trimester
Describe the typical clinical presentation of Rett syndrome.
Normal development during first 18 months of life
Temporary stagnation
Neurodegenerative
Loss of communication skills
Constant hand-wringing
Loss of purposeful hand function
How does Rett syndrome present in males?
Embryonic death
Why is Rett syndrome extremely rare in viable males?
The MECP2 gene is on the X chromosome, so it is normally lethal in males (who only have one X chromosome)
The MECP2 gene is found on which chromosome?
The X chromosome
A tall patient with tapering fingers presents to the clinic with visual problems related to subluxation of the lens of his right eye. Three days later, he dies of a cardiovascular event.
What disorder does the patient have, and what causes it?
Of what CV event did he likely die?
Marfan’s syndrome, fibrillin-1 defect (a scaffold for tropo-elastin);
aortic dissection
A teenager presents to the clinic with hyperextensible joints and skin. You notice in his history that he has been diagnosed with a murmur of one of his heart valves in the past. The patient appears well and normal for age.
What is a likely diagnosis for this patient?
What protein is likely not being produced properly?
Ehlers-Danlos syndrome;
collagen
In what layer of the skin are skin cancers most likely to originate?
The stratum basale of the epidermis
(e.g. basal cell carcinomas and melanomas)
A defect in the anchoring fibrils that connect the epidermis to the dermis can result in what condition involving blistering and skin erosion?
Epidermolysis bullosa
What are the two primary causes of albinism?
A defect/deficiency in tyrosinase;
a decreased melanin production rate
Why is the subcutaneous layer of tissue such a useful location for drug administration?
It is highly vascular
What is the term for the layers and sections of fat of the subcutaneous (hypodermic) layer?
What is the layer of striated muscle deep to the subcutaneous tissue?
The panniculus adiposus;
the panniculus carnasus
What substance binds keratin together to create the waterproofing of the skin?
Lack of this substance results in what?
Filaggrin;
ichthyosis
Filaggrin defect/deficiency leads to what immediate effect in the skin and what compensatory effect?
What is this condition called?
Dehydration/scaly skin, hyperkeratosis;
ichthyosis
What blistering condition results from defects in anchoring proteins (e.g. hemidesmosomes)
What blistering condition results as an autoimmune attack on desmosomes (specifically, desmoglein I and III)?
Epidermolysis bullosa;
pemphigus vulgaris
What disease is demonstrated here?
How is this disease classified?
Pemphigus vulgaris;
autoimmune (against desmoglein I, III)
What disease is demonstrated here?
How is this disease classified?
Epidermolysis bullosa;
genetic (hemidesmosome defect)
What disease is demonstrated here?
Psoriasis
What type of skin condition results in universally loose fragile skin? Due to a defect in what?
What type of skin condition results in universally impaired elastic recoil? Due to a defect in what?
Ehlers-Danlos, collagen fibers
cutis laxa, elastic fibers
Cutis laxa results because of a defect in what protein?
Ehlers-Danlos results because of a defect in what protein?
Elastic fibers;
collagen fibers
Cri-du-Chat syndrome is a microdeletion of the short arm of chromosome __.
5
A carrier of a Robertsonian translocation has how many chromosomes?
45
What is another name for DiGeorge syndrome?
It is due to a deletion of what genetic sequence?
Velocardiofacial syndrome;
22q11
What rare type of skin cancer spreads quickly and deeper than BCC, SCC, and melanoma?
Merkel cell carcinomas
List the types of skin cancer from most to least common.
Basal cell carc. > squamous cell carc. >> melanoma
>>>> anything else
What is the most common type of cancer worldwide?
Skin cancer
Genetic defect of hemidesmosomes causes:
Autoantibodies against hemidesmosomes causes:
Autoantibodies against desmosomes causes:
Epidermolysis bullosa;
bullous pemphigoid;
pemphigus vulgaris
Why is acne typically associated with adolescents?
Sebaceous gland activity increases in adolescence
Acne is caused by what?
Plugged hair follicles and their associated sebaceous glands
What wide-spectrum antibiotic is a bacterial topoisomerase inhibitor?
Ciprofloxacin
What is ciprofloxacin?
How does it exert its effect?
A wide-spectrum antibiotic;
inhibiting bacterial topoisomerase
What two eukaryotic topoisomerase inhibitors can be used to treat some colon and ovarian cancers?
Which topoisomerase do they inhibit?
Irinotecan and Topotecan;
type I
What are Irinotecan and Topotecan?
How do they exert their effect?
Chemotherapeutic agents;
type I topoisomerase inhibition
What are Doxorubicin (adriamycin), etoposide, and ellipticine?
How do they exert their effects?
Chemotherapeutic agents;
type II topoisomerase inhibitors
What wide-spectrum antibiotic is a bacterial topoisomerase inhibitor?
What are two chemotherapeutic agents that are type I topoisomerase inhibitors?
What are three chemotherapeutic agents that are type II topoisomerase inhibitors?
Ciprofloxacin;
Irinotecan, Topotecan;
Doxorubicin (adriamycin), etoposide, and ellipticine
By which types of UV ray are we most at-risk of being harmed?
Which UV ray is blocked by the ozone?
UVA, UVB;
UVC
What type of DNA mutation is often caused by UV rays?
Thymidine dimers
What is the underlying defect in xeroderma pigmentosum?
What is its inheiritance pattern?
A defect in nucleotide excision repair (to repair thymidine dimers, especially);
autosomal recessive
By what age have most individuals with xeroderma pigmentosum developed some sort of skin cancer (often squamous cell carcinoma)?
8
True/False.
Individuals with xeroderma pigmentosum typically live a normal lifespan.
False.
What is the most common cause of death among individuals with xeroderma pigmentosum?
Squamous cell carcinoma
In nucleotide excision repair, what enzyme typically removes the damaged section?
An endonuclease
In nucleotide excision repair, what enzyme typically refills the removed portion?
DNA polymerase
In nucleotide excision repair, what enzyme typically seals up the repaired DNA portion?
DNA ligase
Name three enzymes necessary to nucleotide excision repair.
Endonuclease, DNA polymerase, DNA ligase
True/False.
Squamous cell carcinoma is associated with mutations in the BRAF and RAS genes.
False (SCC is associated with P53 issues);
melanoma is associated with BRAF and RAS