Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

Biochem > Lecture 5 Information > Flashcards

Lecture 5 Information Flashcards

1
Q

Why do humans need more hemoglobin than earthworms?

A

Earthworms do not move as much as humans and therefore have a slower rate of metabolism and do not need as much O2

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

Is ligand binding always good?

A

No

if a toxin binds to a protein and is brought into the cell through endocytosis, the toxins can integrate themselves into the cell membrane and can potentially cause paralysis

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

How does insulin work as a ligand?

A

insulin binds to protein on the cell’s membrane which triggers the cell to uptake glucose for metabolism

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

Induced fit

A

the structure that a protein assumes as it binds its ligand

maxmizes interactions between the ligand and the protein

conformational change

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

What does induced fit have to be?

A

reversible

want to be able to reuse the proteins that are binding the ligand

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

Dissociation constant (Kd)

A

=reactants / products

*opposite of Keq

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

What does a lower Kd mean?

A

a stronger binding affinity

more likely to have products than reactants

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

Theta

A

the fraction of binding sites that are occupied

[PL] / [PL] + [L]

how many sites are occupied out of the total number of sites

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

What happens as ligand concentration increases to theta?

A

Theta generally increases as more ligand sites are occupied

Eventually theta will reach a max and plateau

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

How can you graphical find Kd?

A

plot Theta versus Ligand Concentration

look at where the graph crosses 0.5 theta

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

Why doesn’t theta ever reach 1 and all binding sites occupied?

A

this would require so many ligands that you would exceed the solubility of the ligands

the ligands would not be soluble at that high of a concentration and actually start precipitating out

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

why do we need a delivery system for O2?

A

O2 is not very soluble in water

will cause harmful bubbles in the blood rather than dissolve

need myoglobin to carry this gas through the blood

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

Why do we use Fe and Cu to bind O2?

A

these metals bind O2 reversibly

amino acids do not bind O2 reversibly

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

How is Fe coordinated in myoglobin?

A

Fe is attached to histidine residue on one side and directly across the O2 binds

This forms a straight line which allows O2 to bind more tightly

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

How is O2 allowed into the myoglobin complex?

A

through H-bonding interactions with histidines

CO does not have this same interaction and cannot get into the complex as easily

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

What is the shape of the curve of binding of myoglobin to oxygen?

A

hyperbolic curve

increases, reaches a max, and then flattens out

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

How are hemoglobin’s 4 subunits held together?

A

by noncovalent interactions

hydrogen bonds, hydrophobic interactions, ionic bonds, some disulfide, etc.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

T state of hemoglobin

A

low O2 affinity conformation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

R state of hemoglobin

A

high O2 affinity conformation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What does the binding of O2 to hemoglobin do?

A

changes the conformation of the molecule

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Cooperative binding

A

the binding of one ligand to a subunit affects the structure and the binding affinity of other sites

*same with reverse direction when O2 is lost

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What type of curve indicates cooperative binding?

A

Sigmoid binding curve

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Allostery

A

binding at one site affects the shape of another site

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Why do we use hemoglobin and not myoglobin as our primary oxygen carrier?

A

Myoglobin has a higher affinity for oxygen

Would not release oxygen in deep tissues where it is needed

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
What 4 things contribute to the binding of hemoglobin to oxygen?
1) pO2 2) pH 3) CO2 concentration in the tissues 4) Binding of BPG
26
What state does hemoglobin arrive to the lungs in?
arrives in the T-state with BPG attached in central area
27
What happens when hemoglobin picks up O2 in the lungs?
it switches from T-state to R-state *BPG is also released before picking up O2
28
BPG
2,3-bishosphoglycerate highly negatively charged and binds to positive residues in the central portion of the hemoglobin molecule allows subunits to be held in the T state
29
How does pH influence the conformation of hemoglobin?
when CO2 concentration is high (like in the lungs), it becomes HCO3- and H+. These H+ protons lower the pH and can attach to histidine residues on hemoglobin The histidine residues become positively charged and stabilize a negatively charged aspartate these interactions help stabilize the T-state So t-state is favored a lower pHs and O2 will be released
30
How does CO2 get transported to the lungs?
around 25-30% of CO2 gets transported to the lungs through hemoglobin CO2 binds to the amino terminus and converts the terminus into a carbonyl group
31
Why does fetal hemoglobin have a higher affinity for oxygen than maternal hemoglobin?
this facilitates the transfer of oxygen from the mother to the fetus
32
What is fetal hemoglobin made out of?
gammaglobin, higher O2 affinity
33
Bohr effect
hemoglobin binds more tightly to oxygen at high pHs hemoglobin binds less tightly to oxygen at low pHs
34
pH of the lungs
7.6
35
pH of the deep tissues
7.2
36
Altitude and binding affinity
at high altitude, pO2 is much lower and you do not get as much oxygen in the lungs this means there is less oxygen to drop off in the tissues need to increase the amount of BPG so the T-state is favored and oxygen will be dropped off
37
Why do we never give up all the oxygen?
need to keep a reserve for emergency situations
38
Sickle Cell Anemia
Mutation on the B-subunit of hemoglobin and Glu is converted to Val Val can generate hydrophobic patches that come together and form a chain of hemoglobin This distorts the shape of the red blood cell
39
Are muscle fibers made up of multiple cells?
no they are actually a single cell with multiple nuclei
40
Sarcomeres
sections of myofibrils in muscle cells individual contractile units in muscle fibers include the tissue between one I-band and another
41
Thick filament
made of myosin proteins that come together intertwined dimers make up the thick filament
42
Thin filament
made up of actin monomers that have polymerized into a chain ATP is needed to combine actin monomers
43
I-band
region of thin filament without any thick filament present contracts in muscle contraction
44
A-band
center of the thick filament that holds myosins together
45
Z disks
found on either end of a sacromere are pulled together as the muscle contracts
46
What does each actin monomer have on it?
ADP and a region to bind to myosin
47
Troponin subunits
found on the thin filaments prevent actin from binding to myosin
48
Calcium and muscle contraction
Calcium triggers a conformational change in troponin to unbind it and myosin can bind to actin An electrical signal releases calcium
49
What state does myosin start in?
begins in a rigor state that has no bound nucleotide and myosin is tightly bound to actin no movement of muscle
50
How does myosin work?
ATP binds to myosin and releases it from actin Myosin then uses ATP to be in an activated state (changes conformation) Rebinds to another actin filament and releases Pi Pi triggers a "power stroke" that moves actin one unit forward
51
Power stroke
conformational change back to the original state that causes ADP to be released move one actin molecule further along the chain ADP is released and we return to the rigor state
52
A prothestic group
is permanently associated with a protein an example is the heme group
53
What is the relationship between Ka and Kd?
they are inverses as one increases, the other decreases
54
What are the similarities between myoglobin and hemoglobin's subunits?
myoglobin and hemoglobin's subunits have a very similar tertiary structure, but different primary structure
55
What is the defining secondary structure of myosin?
alpha helices | these coil around each other in a left-handed helix
56
What is the energy released by ATP by actin used for?
actin filament assembly actin requires energy to polymerize
57
What binds stronger to the heme group, O2 or CO?
CO so, have to prevent CO from entering the complex
58
Which ions/molecules does hemoglobin transport?
CO2, O2, and H+
59
What converts CO2 to HCO3-?
carbonic anhydrase
60
What do the nitrogens in the heme group do?
they have electron donating character that prevents Fe2+ from transitioning to Fe3+
61
Why does the sickle cell anemia trait continue?
the trait prevents people from getting malaria infection
62
When can you find Kd?
when half the binding sites are occupied 0.5 theta
63
What would happen if histidine changed into a nonpolar group in heme?
the iron would not be coordinated to histidine
64
How does CO bind more strongly to the heme group than O2?
CO binds perpendicular to the heme group's ring allows maximum overlap between CO and Fe2+
65
What reduces CO from binding to heme groups?
histidine residues
66
What triggers a power stroke?
the release of Pi
67
Titins
the largest single polypeptide chair discovered thus far link thick filaments to the Z disk regulates the length of the sacromere itself and prevents overextension
68
Relationship between Kd and [L]
Kd=[L] when 1/2 of the binding sites are occupied (theta=0.5)
69
When do you use a Scathard plot?
when you want a more preside measurement of Kd
70
What does Scathard plot graph?
Bound/Free versus Bound
71
How to find Kd from Scathard plot?
Slope = -1/Kd
72
Bmax
all the possible binding sites [L] + [PL]
73
How can you express the number of unbound sites?
[P] = Bmax - [PL]
74
What is the binding pattern of myoglobin to oxygen?
hyperbolic
75
What is the binding pattern of hemoglobin to oxygen?
sigmoidal when concentrations of the ligand are low, don't bind as well as when concentrations of the ligand are high there is cooperative binding taking place
76
Why can't you use Edman degradation in the deep tissues?
CO2 is bound to the N-terminus of hemoglobin
77
Why do you need capillaries in the muscles?
need them to exchange O2 with CO2
78
Sarcoplasmic reticulum
stores calcium which can be released to remove troponin
79
H-zone of the sarcomere
lacks thin filaments when extended center of the sarcomere as myosin crawls along the thin filaments, the thin filaments get pulled towards the middle of the H-Zone

Biochem (20 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions