Unit 2 Review: Biochemistry, Cell Biology, & Genetics

Question 1

The catalytic rate of an enzyme is MOST sensitive to [S] when:

Answer 1

When S is much lower than Km, steep curve

Question 2

For an enzymatic reaction, If the concentration of substrate is 5mM and the Km is 2mM, what fraction of enzyme is bound to substrate?

Answer 2

5/7

[S] = 5 mM; Km = 2 mM
[S]/([S] + Km) = 5/(5+2) = 5/7

Question 3

When is Km approximately equal to Kd (the dissociation constant) for the ES complex?

Answer 3

when K2 is much greater than K3

Kd = K2/K1
Km = K2+K3/K1

when K3 is small, both are roughly equal

Question 4

which enzyme’s activity is more sensitive to the body’s concentration of glucose? Hexokinase, glucokinase, or activity is independant for both enzymes?

Answer 4

Hexokinase becomes saturated and reaches its Vmax at a low concentration.

Glucose is much more sensitive to changes in glucose concentration

Question 5

The protease of an hiv strain that is highly resistant to a protease inhibitor will show what combinations of properties?

Answer 5

High Ki indicates that the protease is highly resistant to a particular inhibitor because that inhibitor does not bind tightly to it
A high kcat/Km (or at least a kcat/Km that is approximately equal to wild type) means that the protease is highly effective at catalyzing the reaction and producing product
The most resistant HIV strains have proteases that are resistant to inhibitors but still efficient at doing their job

Question 6

Which aspect of the body’s response to blood vessel injury is affected by warfarin?

Answer 6

Localization of the clotting proteins to the site of injury

Warfarin inhibits a vit K-dependent enzyme that allows clotting proteins (factors II, VII, IX, X) to adhere to membranes at the injury site

Question 7

two requirements for a coupled enzyme reaction

Answer 7

substrate in excess. the reaction that uses the enzyme in question must be slower. the second reaction must be much faster

Coupled enzyme assays are useful when the products of the reaction catalyzed by the enzyme of interest cannot be quantified easily (either because they’re similar to the substrates or difficult to detect)
You can use the products as substrate for a second reaction for which the products CAN be measured easily
In order for this to work, the second reaction must be very fast and all substrates must be present in excess

Question 8

ALT

Answer 8

viral hepatitis

Question 9

amylase

Answer 9

pancreatitis

Question 10

creatine kinase

Answer 10

muscle disorders/MI

Question 11

Lipase

Answer 11

pancreatitis

Question 12

lactate dehydrogenase

Answer 12

liver disorders

Question 13

acid phosphatase

Answer 13

metastatic prostate carcinoma

Question 14

alkaline phosphate

Answer 14

bone disorders and obstructive liver disesae

Question 15

Hydrophobic signaling molecules

Typically bind nuclear/cytoplasmic receptors

Bind cell surface receptors and typically activate gene transcription

Tend to have relatively short half lives

Do NOT need binding proteins to be carried throughout the blood, examples include steroids and thyroid hormones.

Answer 15

typically bind nuclear/cytoplasmic receptors

Carried by binding proteins
Relatively long half lives
Freely pass through cell membranes
Bind nuclear receptors- which activate gene transcription
Steroids, retinoids, thyroid hormones
Exception: eicosinoids which are hydrophobic, but bind surface receptors, short half life, function on inflammatory responses and clotting

Question 16

eicosinoids

Answer 16

which are hydrophobic, but bind surface receptors, short half life, function on inflammatory responses and clotting

Question 17

hydrophilic signaling molecules

Answer 17

Peptides, nucleotides, amino acids, growth factors
Do NOT need carrier molecules to transport through blood
Have shorter half lives
Bind cell surface receptors and can act through
Ligand-gated ion channels
Enzyme linked receptors
Catalytic receptors,
Trimeric G-protein-linked receptors

Question 18

pemphigus results from

Answer 18

autoimmune attack of desmosomal cadherin

Question 19

adherens junctions allow for the

Answer 19

oriented contraction of actin filaments across cells, which is used to form the neural tube during development

Question 20

fibronectin

Answer 20

a dimer using disulfide bonds, self-associates into bundles and fibrils. Interacts with integrins. Plays role in loose connective tissue, blood clots, wound healing

Question 21

laminin

Answer 21

interacts with type IV collagen, integrin and proteoglycans. Major component of the basal lamina

Question 22

Bad-

BCL2-BCLX -

BAX -

Answer 22

Bad- pro-apoptotic, with no signals for the cell to grow (trophic factors). Bad is free to interact with Bcl2/Bclx

Bcl2/Bclx- anti-apoptotic, normally interact with and inhibits Bax. Interaction with Bad prevents interaction with Bax

Bax- pro-apoptotic, when NOT INHIBITED by Bcl2/Bclx, forms channels and leads to cytochrome c release into cytosol ->apoptosis

Question 23

describe trophic factors and apoptosis pathway

Answer 23

1. No trophic factors -> Bad is free
2. Bad interacts with Bcl2/Bclx(located in mitochondrial membrane)
3. Bcl2/Bclx can no longer exert their inhibitory effects on Bax
4. Bax is free to promote cytochrome c release from mitochondria into the cytosol -> procaspases become caspsases -> APOPTOSIS

Question 24

eosin does what?

Answer 24

is an acidic stain, binds basic structures such as cytoplasmic proteins

Question 25

metaplasia
hypertrophy
hyperplasia
atrophy
dysplasia

Answer 25

change in cell type that can protect against stress
hypertrophy - change in size
hyperplasia - increase in number
atrophy - cell death
dysplasia - change in organization

Question 26

hematoxylin

Answer 26

Hematoxylin is a basic dye and binds nucleic acids

Question 27

collagen stains

reticular fibers stain

elastic fibers stain

macrophages stain

Answer 27

Collagen: Stains homogenously PINK with eosin

Reticular fibers: Stain BLACK with silver

Elastic fibers: Special stains, pico-orcein & resorcin fuchsin

Macrophages: Stain with trypan blue

Question 28

CT in the head is derived from

Answer 28

neural crest cells

Question 29

Ehlers-Danlos syndrome type IV is caused by

Answer 29

deficient type III collagen

Question 30

Connective tissue in most of the body develops from

Answer 30

embryonic mesoderm

Question 31

marfan syndrome

Answer 31

defective fibrillin

Question 32

A morphogen is

Answer 32

a paracrine signaling molecule that produces concentration-dependent responses

Question 33

Nodal is a

Answer 33

Nodal is a TGFB signaling molecule, it’s a secreted signaling molecule

Question 34

Left-right asymmetry defects can lead to

Answer 34

melioration and volvulus in addition to congenital heart defects, asplenia, and polysplenia)

Question 35

CML

Answer 35

characterized by a t(9;22) translocation which results in the over-expression of a tyrosine kinase (proto-oncogene)

Question 36

Li-Fraumeni syndrome

Answer 36

associated with an inherited mutation of p53

Question 37

Breast Cancer is associated with

Answer 37

with losses of homologous recombination & DNA repair genes

Question 38

Which of the following is characteristic of cancer evolution?

Mutations in different cells complement each other and result in tumor development

Both somatic and germline mutations are generally seen in familial cancers

Genes must be lost in a specific sequential order to result in a given cancer

Proto-oncogenes tend to be responsible for DNA repair pathways

Answer 38

B

A - Multiple mutations must occur in a SINGLE cell to result in cancer
B – Most familial cancers are associated with an inherited loss of a tumor suppressor (from the germline) followed by somatic mutation of the second copy
C – The order of mutations is not important, but certain genes may need to be lost
D- Proto-oncogenes promote unregulated growth and proliferation - only one mutation required (gain of function)
Tumor suppressors tend to promote DNA repair, regulate the cell cycle, or inhibit growth. Both genes must be lost for tumorigenesis

Question 39

Which of the following is NOT an application of FISH for cancer genetics?

Diagnosis of particular syndromes and prognostic information

Identification of successful treatment (remission)

Identification of relapse

All of the above are potential applications of FISH

Answer 39

all

Question 40

klinefelter

Answer 40

47, XXY

infertility due to hyalninized testituclar tubules

Question 41

XYY male

Answer 41

dose not effect interlligence or fertility

due to excluisvely paternal nondisjunction error

Question 42

turner syndrome

Answer 42

45,X shield chest

Question 43

XXX female

Answer 43

tall phenotype, does not effect intelligence or fertility

Question 44

A phenotypically normal female presents to your office complaining of infertility. An ultrasound reveals the presence of testicles in the abdomen and pelvic exam reveals a blind vagina.

What underlying disorder does this patient likely have?
What is their genotype?

Answer 44

Androgen insensitivity
=inappropriate corssing over between TDF region and ARM of X chromosome, the Y then loses its Testes determining factor, end up with just one X chromosome because the Y has lost its testes determining factor (happens in male gamete). Y chromosome loses the male (TDF) region, the fetus inherits the Xy where the Y is worthless, = 46, XY

Turner females are at risk for gonadoblastoma

Due to a mutation of the androgen receptor gene on the X chromosome  no androgen receptors produced
TDF protein initiates male development, but without the androgen receptor protein, the pathway is blocked and development defaults back to female
Genotype XY

Disease is called androgen insensitivity

Y chromosome – develop testicles, but receptors don’t develop, so evefytinge sel developes in female pathway

Question 45

What genetic error could result in a Turner female phenotype with a 46, XY karyotype?

Answer 45

A translocation in which the TDF/SRY region on the Y chromosome is replaced by Xp material would yield a Y without the TDF/SRY sequence. If this Y was passed onto an offspring, normal male development would not occur and the patient would default to a female phenotype. Since the patient would only have one functional X chromosome, a Turner phenotype would occur

Question 46

In order for balanced translocation carriers to generate gametes resulting in a normal child, which type of segregation must occur?

Answer 46

alternate segregation

In alternate, get a full blue and full red, and a full blue and a full red in both. Good situation. In rest you have unequal balance. You want an alternate segregation

Question 47

robertsonian chromosome results from

Answer 47

centromere to centromete translocation of acrocentric chromosomes

Question 48

Recombination products of paracentric inversions are

Answer 48

unstable and tend to be lost

Question 49

A large pericentric inversion tends to

Answer 49

cause fewer duplications and deletions during recombination than a msall pericentric inversion

Question 50

an interstitial deletion occurs when

Answer 50

an internal region of a chromosome is lost

Question 51

TF Low AFAFP can be diagnostic of chromosomal abnormalities

Answer 51

False. It is a screening test. The first trimester screen, Quad screen, and cfDNA are all screening tests and require follow-up diagnostic testing.

Question 52

TF high maternal AFP associated with downs

Answer 52

False- high AFP is associated with neural tube defects, low AFP is associated with Down Syndrome and other chromosomal abnormalities

Question 53

common reason for high AFAFP is?

Answer 53

incorrectl reported gestational age

Question 54

CVS samples…

Answer 54

false- placental tissue, meaning that in rare instances of mosaicism there may be a confined placental mutation or confined fetal mutation)

Question 55

AFAFP may be collected by CVS

Answer 55

false, no amniotic fluid is collected

Question 56

describe proteoglycans. what gives them their unique characteristics

Answer 56

Remember that those sugars are often sulfated with many carboxyl groups, very hydrophilic. Recruit large number of water molecules. EXAM q. 90 of it is water= creates hydrated gel.