Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

025. My MCM Test 2 > Erythrocyte Biochemistry > Flashcards

Erythrocyte Biochemistry Flashcards

1
Q

What are the steps in erythropoiesis?

A
  1. Hemocytoblast (stem)
  2. Proerythroblast (committed)
  3. Early erythroblast (phase 1-ribo syn)
  4. Late erythroblast (phase 2-Hg accum)
  5. Normoblast (Phase 2)
  6. Normoblast releasing Hemoglobin (phase 3)
  7. Reticulocyte
  8. Erythrocyte
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is the structure of hemoglobin?

A

A tetramer with 2 alpha globin chains and 2 beta globin chains

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What do heme (hydrophobic) contain and where are they located?

A

One heme per subunit (4), with iron ferrous (Fe2+) in middle which carries O2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What are the 3 different types of embryonic hemoglobin (Hb), and when are they destroyed?

A

Gower 1
Gower 2
Portland
destroyed by week 8

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is the compostion of hemoglobin as a fetus (HbF) at 10 weeks of life until birth?

A

HbF is made of alpha and gama 2, after birth gama decreases and alpha increases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is the composition of hemoglobin as an adult (HbA)?

A

Alpha 2 and beta 2 (97%) (3% sigma 2)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What chromosomes do all of the types of hemoglbin chains in embryo, fetus, and adult come from?

A

They come from chromosome # 16 & 11

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What type of mutation and what mutation occurs in hemoglobin and at which subunit?

A

Misense mutation, chaning Glutamate (-) to Valine (hydrophobic), mutation occurs in HbS, defect in beta chain!

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is one way being research to reverse sickel cell anemia?

A

use hydroxyurea to induce HbF (upregulate), reducing beta chain and increasing gama chain

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is the F8 histidine called and what does it do?

A

called the proximal histidine, which is bound to heme

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is E7 histidine called and what does it do?

A

called the distal histidine, O2 binds to iron between heme and E7, causing a conformational change, pulling down the F8 histidine

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What type of oxygen dissociation curve does myoglobin have?

A

Hyperbolic curve, with a partial saturation (p50) of 1-2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What type of oxygen dissociation curve does hemoglobin have ?

A

Sigmoidal curve, with a partial saturation (p50) of 26 torr

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Why does hemoglobin show positive cooperativity?

A

Because the binding of one O2 facilitates the binding of the second, and so forth. The binding induces a conformational change, (pulling down the F8 his)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

As the pH decreases (lets say in respiring tissues) what happens to Hb binding affinity? What does it pick up instead?

A

affinity of Hb for O2 decreases ,releasing O2 and His146 picks up H+ instead

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What does pure Hb bind O2 more tightly than erythrocyte Hb?

A

RBC Hb contain 2,3-BPG which reduces O2 affinity, allowing Hb to give the O2 to tissues (same as exercise)

17
Q

Why do fetal RBCs have a higher O2 affinity than adult Hb?

A

HbF does not bind to 2,3-BPG

18
Q

How is iron distributed in humans?

A

67% in Hb
27% is stored
- ferritin (h2o soluble)
- hemosiderin (h2o insoluble)

19
Q

How does one become iron deficient and what does it cause?

A

Poor iron in diet, menstruating women, aspirin overuse, Ulcers in gi tract, causing hypochromic microcytic anemia

20
Q

What is hereditary hemochromatosis?

A

When ograns have too much iron (overloading) (cirrhosis/arthritis), Normal Fe in body :3-5g, hemochromatosis: 15g

21
Q

What is hepcidin and What does hepcidin do?

A

Hepcidin is a regulator of iron homeostasis. It binds to ferroportin causing iron to be degraded by proteolysis

22
Q

How is iron absorption regulated by hepcidin?

A

When iron is high, there will be high hepcidin, leading to a reduction in iron absorption, and vice versa

23
Q

How is hepcidin expression regulated?

A

transferrin (alot) bind to its receptor (Tfr1) which release transcription factor Hfe, which bind to hepcidin signaling complex (Tfr2), activating hepcidin

24
Q

What happens if Hfe TF is mutated in iron regulation?

A

Hfe wont be able to turn on hepcidin expression and will have no control of ferroportin activity, leads to iron overloading (hemochromatosis)

25
Q

How does anemia affect ferroportin?

A

If anemic, has overexpression of hepcidin, leading to over regulation of ferroportin, resulting in very low iron in blood and iron accumulation in entercytes

26
Q

What causes megaloblastic (large erythrocytes) anemia?

A

Diminished synthesis of DNA due to a deficiency in B12 (cobalamin) and folate (folic acid),have normal Hb, RBC volume increased

27
Q

What are key characteristics of megaloblastic anemia in BM?

A

large erythroblast (megaloblasts) in BM, hyper segmented neutrohpils (more than 5 lobes, usually 3-4)

28
Q

How many different sections are in folate?

A

pteridine, PABA, and glutamate (THREE SECTIONS!)

29
Q

What does dihydrofolate reductase do to folate (F), and to that product?

A

Converts folate to dihydrofolate (FH2) (+2 hydrogens), and then by dihydrofolate reductase, goes to tetrahydrofolate (FH4) (+2 MORE hydrogens)

30
Q

What is the importance of THF (FH4)?

A

Is it the active form of folate and transfers carbon units

vital role in DNA synthesis

31
Q

What is a deficiency of folic acid bad?

A

Leads to decreased DNA synthesis (because THF forms this) which leads to megaloblastic anemia

32
Q

What happens once folic acid is absorbed in the intestine?

A

Folic acid is reduced to N5methyl-THF which needs B12 to make into THF

33
Q

What is the key role of vitamin B12?

A

N5methyl requires B12 to become demethylated making B12-CH3 and allowing THF to be made

34
Q

Where can vitamin B12 be found?

A

In animal products, not in plant products

35
Q

What is the general mechanism for B12 absorption?

A

B12 binds to R-binder (stomach), which binds to intrinsic factor (rbinder degraded in duodenum), carries to illeum where IF-B12 is take up by receptor mediated endocytosis, circulates through blood by transcobalamin

36
Q

What cause pernicious anemia (a type of megaloblastic macrocytic anemia)?

A

B12 deficiency due to lack of intrinsic factor (allows b12 to be absorbed)

37
Q

What is part of the Schilling test Part 1?

A

Radioactive B12 taken orally with 1000ug unlabeled (will saturate receptros so labeled ends up in urine). If labeled present in urine, due to diet. If labeled B12 not present in urine, absorption errors and move to part 2 of schillings

38
Q

What is part 2 of the schilling test?

A

give radioactive B12 plus IF along with 1000ug to saturate receptors, if present in urine, pernicious anemia is due to lack of intrinsic factor!

025. My MCM Test 2 (15 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions