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Biochem 1. midterm > Amino acids, proteins and hemoglobin > Flashcards

Amino acids, proteins and hemoglobin Flashcards

(71 cards)

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1
Q

Nonpolar sidechains interact…

A

Only hydrophobically

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2
Q

Nonpolar amino acids are found on …

A

the inside of proteins (not on the surface) in water, in nonpolar substance it is on the surface.

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3
Q

Special about proline

A

It has a imide group not a amide group. Break a-helixes and often found in collagen

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4
Q

Lose a proton in alkaline pH (uncharged)

A

Cystein and tyrosine

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5
Q

Unpharged polar a.a. then can participate in hydrogen bonding

A

Serine, threosine and tyrosine (alcohols). Asparagine and glutamine (carbonyl group)

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6
Q

— contains a — group and forms disulfide bonds

A

Cystine, sulfhydryl

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7
Q

Can serve as attachments of other compounds

A

Serine, asparagine and threonine (rarely tyrosine)

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8
Q

Attachment for oligosaccarides (aa)

A

Serine, asparagine, threonine

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9
Q

Hisidines side chain is — at physi. pH

A

Uncharged in free amino acid. But in protein it can be positively or neutral

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10
Q

Larger Ka means…

A

Stronger acid

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11
Q

Zwitter ion

A

Isoelectric form, over all charge is zero

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12
Q

Read amino acid sequence from—

A

From N-terminal to C-terminal

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13
Q

The is no free rotation in peptide bonds around

A

Between the carbonyl carbon and the nitrogen due to partial double-bond character

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14
Q

Is a peptide usually a trans band or cis bond?

A

Trans bond

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15
Q

Reason for trans bond in peptides?

A

Steric interaction (taking up space)

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16
Q

How can you determine aa. composition?

A

Fist heat at 110 degrees for 24h. Then e.g. use cation-exchange chromatography or anion-exchange chromatography. Aa will attach differently to a column (anion-exchange column). Ninhydrin reacts and makes it purple. Amount of each aa can then be determines by spectrophotometer.

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17
Q

Used to label amino-terminal under alkaline conditions

A

Phenylisothiocynate (Edman’s reagent)

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18
Q

Aa in a a helix turn?

A

3.6

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19
Q

Alfa helix left handed or right handed?

A

Right handed

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20
Q

What disrupt a Alfa helix?

A

Proline geometrically. Charged amino acids make ionic bonds and repel. Eg glutamate, aspartate, histidine, lysine, arginine. In large numbers: tryptophan, valine, isoleucine

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21
Q

Interchain bonds

A

Hydrogen bonds are formed between separate polypeptides in b sheet

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22
Q

Interchain bonds

A

Hydrogen bonds inside the same polypeptide in b sheet

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23
Q

Two things about beta bend

A

Often four aa, often proline and glycine, stabilized by hydrogen and ionic bonds

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24
Q

How much of globular proteins are a helix or b sheet?

A

Approximately half

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25
Other name for supersecondary structure
Motifs.
26
Four types of interactions stabilize tertiary structure
Disulfide bonds, hydrophobic interactions, hydrogen bonds, ionic interactions
27
Reasons why denatured proteins don't fold together
1. The protein begins to fold in stages during synthesis | 2. Chaperones (heat shock bodies) can help with folding or catalyze
28
Proteins consisting of one polypeptide is called
Monomeric protein
29
Heme is a complex of
Protoporphyrin IX and ferrous iron (Fe2+)
30
Hemeprotein in heart and skeletal muscle
Myoglobin
31
How much of myoglobin is a helix?
80%, into 8 a helices
32
Aa in a a helix turn?
3.6
33
Alfa helix left handed or right handed?
Right handed
34
What disrupt a Alfa helix?
Proline geometrically. Charged amino acids make ionic bonds and repel. Eg glutamate, aspartate, histidine, lysine, arginine. In large numbers: tryptophan, valine, isoleucine
35
Interchain bonds
Hydrogen bonds are formed between separate polypeptides in b sheet
36
Interchain bonds
Hydrogen bonds inside the same polypeptide in b sheet
37
Two things about beta bend
Often four aa, often proline and glycine, stabilized by hydrogen and ionic bonds
38
How much of globular proteins are a helix or b sheet?
Approximately half
39
Other name for supersecondary structure
Motifs.
40
Four types of interactions stabilize tertiary structure
Disulfide bonds, hydrophobic interactions, hydrogen bonds, ionic interactions
41
Reasons why denatured proteins don't fold together
1. The protein begins to fold in stages during synthesis | 2. Chaperones (heat shock bodies) can help with folding or catalyze
42
Proteins consisting of one polypeptide is called
Monomeric protein
43
Heme is a complex of
Protoporphyrin IX and ferrous iron (Fe2+)
44
Hemeprotein in heart and skeletal muscle
Myoglobin
45
How much of myoglobin is a helix?
80%, into 8 a helices
46
Cooperative binding
Binding of an oxygen molecule at one heme increases affinity on the remaining heme
47
Allosteric effect
Interaction at one side of the hemoglobin. Ability of hemoglobin is affected by the pO2, pH and 2,3-BPG. Myoglobin is not affected.
48
Bohr effect
Release of oxygen is enhanced by lowered pH, or higher pressure of CO2. Decreased affinity
49
Enzyme that converts CO2 into carbonic acid
Carbonic anhydrase
50
Mechanism of Bohr effect
Caused by N terminal and specific histidine side chain, they have higher pKa in deoxy group than oxyhemoglobin. In decreased pH the protonated group stable deoxyhemoglobin and gives decrease in oxygen affinity.
51
2,3-BPG synthesized..
From an intermediate of the glycolytic pathway
52
Effect of 2,3-BPG
Decreases oxygen affinity of hemoglobin by binding to deoxyhemoglobin but not to oxyhemoglobin.
53
2,3-BPG stabilizes ... Confirmation
The taut confirmation
54
Binding site of 2,3-BPG
Pocked formed by the two B-globin chains. Positive binds the negative BPG
55
Most carbon dioxide is transported as..
Bicarbonate ion
56
Some CO2 is carried as
Carbamate bound to uncharged a amino group of hemoglobin (stabilizes the taut form of hemoglobin)
57
Effects of CO
Binds to a heme group, makes it take up oxygen but can't release it again.
58
Hemoglobin: Forms, chain
HbA (ab) 90% HbF (agamma) HbA2 (adelta) HbA1c (abglucose)
59
Why does HbF have higher affinity for oxygen?
Bindes weakly to 2,3-BPG (few positively charged aa)
60
What is HbA1c?
Most abundant glucosylated hemoglobin. Dependent on concentration of hexose
61
Which chromosome contains the two genes for Alfa globin chain?
16 (also embryonic hemoglobin)
62
Single gene for beta globin chain?
Chromosome 11 (also fetal hemoglobin)
63
Globin synthesis steps
Begins in nucleus of red blood cell RNA becomes mRNA Introns are removed, exams remain Enters cytosol where production is done
64
What is Sickle cell disease? How is it caused?
Genetic disorder of the blog caused by a single nucleotide alteration (a point mutation, b-globin gene). Homozygous recessive disorder.
65
Symptoms of Sickle cell disease?
HbS, pain (chronic hemolytic anemia) and increased susceptibility to infection. Acute chest syndrome, renal and splenic dysfunction.
66
Anemia
Decrease of red blood cells.
67
Anoxia
Oxygen deprivation
68
What is hemoglobin C disease? Symptoms?
HbC. Aa substitute on b-globin chain. Causes mild chronic hemolytic anemia.
69
Hemoglobin SC disease? Symptoms?
Some b-globin have HbS mutation, some have HbC. Hemoglobin levels are higher
70
Methemoglobinemias cause? Symptoms?
Heme component is oxidized to ferric F3+. Chocolate colored blood, tissue hypoxia and more
71
Thalassemia cause and symptoms?
Hemolytic disease, hereditary. Imbalance in synthesis of globin chains. 1) beta thalassemias (wrong beta chain) 2) Alfa thalassemias (wrong alfa)

Biochem 1. midterm (3 decks)

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