Brainscape's Knowledge GenomeTM

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


See full index

Biochemistry > Lecture 2, 3 - Proteins & Hemoglobin, Myoglobin > Flashcards

Lecture 2, 3 - Proteins & Hemoglobin, Myoglobin Flashcards

1
Q

Functions of proteins (7)

A 
catalysis
transport (in and out of cell; metabolites)
contractile mechanism
protection
hormones
regulation
structural
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is catalysis?

A

speed up reactions that typically involve changing chemical identity of a substance

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

What are the types of proteins? (5)

A 
simple
membrane
conjugated
globular
fibrous
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is a simple protein?

A

one single polypeptide chain (ex: myoglobin)

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

What’s special about membrane proteins?

A

they are hydrophobic (why they can undergo lipid addition)

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

What do conjugated proteins have?

A

tightly bound covalent factor (ex: Hb with it’s Heme covalently attached so Hb can bind to oxygen)

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

What are globular proteins?

A

alpha helical structures, globular in shape (ex: Hb)

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

What are fibrous proteins?

A

Long and strong, extracellular proteins (ex: collagen)

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

What are the 4 levels of protein structure?

A

primary, secondary, tertiary, quaternary

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

what is the primary protein structure?

A

linear sequence of AA covalently linked by peptide bonds - determines rest of protein structure

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

What is the secondary protein structure?

A

alpha helix, include H-bonding

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

what is the tertiary protein structure?

A

3D arrangement of side chains, including non-covalent interactions like hydrophobic interactions, electrostatic interactions (ionic), salt bridges, and covalent bonding (disulfide bonds)

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

What is the quaternary protein structure?

A

ONLY applies if more than one polypeptide chain (subunits). 2, 3, or 4.

non-covalent interactions b/w chains

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

What are the characteristics of the peptide bond?

A 
COO- + NH3+ (lose H2O) 
determines structure
partial double bond character 
rigid and planar molecule 
can rotate (cis, trans (more stable)) 
main chain carbons (2 alpha C and C bound to N) determines secondary structure
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What are the two amino acids that can assume cis formation?

A

glycine and proline

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

carbonyl and amino make?

A

peptide bond

uncharaged but polar so can form H bonds

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

why are peptide bonds important?

A

important for secondary structure b/c it determines how the polypeptide chains will fold to form their secondary structure due to limitations of bond angles around bond

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

What is the N terminus?

A

free NH3+ (first part of AA chain)

last AA is COO- group

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

How often is there H-bonding in an alpha helix strand?

A

every 4 AA’s

R2 and R6

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

What is a beta sheet? stabilized by?

A

parallel or anti-parallel protein strands

stabilized by H-bonds b/w strands

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

What are supersecondary structures?

A

protein combinations b/w secondary and tertiary structures - combo of secondary structures (B-a-B, Greek key, B-meander, B-barrel)

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

What is the tertiary structure?

A

3D structure

AA chain and 3D arrangement of side chains

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

What are the factors stabilizing tertiary structure?

A

non-covalent interactions (H-bond, ionic, salt bridges, hydrophobic interactions)

covalent - disulfide bonds

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

What is non-covalent binding also known as?

A

solvation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

Covalent bonding v non-covalent bonding?

A

sharing e- v not sharing e-

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

What is denaturation?

A

loss of secondary, tertiary (and quaternary) structure

unfolding and loss of disulfide bonds

protein becomes inactive and nonfunctional

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

What are hemoglobin and myoglobin?

A

major transport proteins for oxygen

28
Q

Where is myoglobin found? What is its function?

A

found in muscle cells
stores oxygen and transports oxygen to mitochondria
able to bind oxygen tightly at low oxygen tension

29
Q

What is Hb’s function?

A

oxygen carrier in blood
binds oxygen at high oxygen tension in lungs and releases it in systemic tissues at low tension
carries CO2 from tissues to lungs

30
Q

Similarities and differences in Mb and Hb tertiary structure

A

both have alpha helix secondary structure (globular and hydrophobic AA interior), both bind Heme interiorly (which allows O2 binding), both are conjugated proteins

Mb has 1 polypeptide chain, Hb has 4 chains

31
Q

What is the structure of heme?

A

extended aromatic ring with a reduced Fe in middle that binds to 4 nitrogens and forms pyrrole rings

and has 2 COO- groups on edge, close to surface of protein

32
Q

What binds oxygen in Hb and Mb? What doesn’t?

A

O2 binds only to Fe2+ heme (reduced form of Fe)

Fe3+ (ferric form) heme aka methemoglobin does not bind O2

33
Q

Fe3+ aka?

A

methemoglobin

34
Q

Heme group

A

Fe ion held in heterocyclic ring (porphyrin), which consists of 4 pyrrole mlcs cyclically linked with Fe bound in center

35
Q

How many hemes are in Hb?

A

4; each polypeptide chain has one that can bind O2

quaternary structure is impt for O2 delivery

36
Q

How many hemes are in Mb?

A

1; Mb is a single polypeptide (up to tertiary structure only) so can only bind 1 O2

37
Q

what does saturation curve tell?

A

how much O2 is bound to molecule

If 1, Mb and Hb completely saturated

38
Q

For Mb, 50% saturation at low pressure indicates?

A

Mb has high affinity for O2; hb has lower affinity for O2

39
Q

Why isn’t Mb effective in delivering O2 from lung to tissue?

A

Mb wouldn’t release O2 at level of tissues whereas Hb would deliver nearly 75% of O2

40
Q

S shaped curve for Hb in linear plot indicates?

A

cooperativity (which requires more than 1 site)

41
Q

Explain positive cooperativity

A

multiple binding sites - affinity of the binding sites for a ligand is increased, positive cooperativity, or decreased, negative cooperativity, upon the binding of a ligand to a binding site.

Hb has 4 sites

42
Q

Hb and + cooperativity

A

1st oxygen has low affinity (T confirmation) - taut

2nd oxygen has high affinity (R confirmation) - relaxed

43
Q

What confirmation is Hb in in absence of oxygen?

A

T confirmation

once O2 binds, confirmation changes to R and Hb undergoes positive cooperativity; next 3 O2 binds easily

44
Q

As O2 binds, what happens to bonds b/w 2 dimers?

A

fewer ionic and H-bonds

45
Q

What does O2 binding do to heme plane? What is link?

A

pulls Fe2+ into heme plane
coordination site with proximal histidine - without O2, Fe is out of plane. When O2 is bound to Fe, Fe is pulled into plane and changes interface

46
Q

what do allosteric modifiers do?

A

changes conformation - when ligand binding at one site influences ligand binding at a different site

47
Q

What are some allosteric modifiers?

A

pH, CO2, 2,3-bisphospoglycerate (BPG)

48
Q

If you increase 4 things, saturation will shift to the right - what are they and what do they do?

A

increased temperature, H+ (dec in pH), CO2, 2,3 BPG will increase P50 and decrease O2 affinity for Hb - aka O2 more easily released

49
Q

What is 2,3 DPG or BPG?

A

product of glycolysis in order to form ATP
when low, Hb has hi affinity for O2
when hi, Hb has lo affinity for O2 and Hb releases O2 more easily

50
Q

at high altitudes, how does saturation curve shift?

A

down and to right

51
Q

Explain how CO2 is an allosteric modifier.

A

BPG stabilizes T confirmation (low affinity confirmation)

CO2 does not bind Mb or heme
CO2 binds Hb (carbamino-Hb) and stabilizes T confirmation
During metabolism, CO2 reduces Hb affinity for O2, O2 released from Hb to tissue, which has low tension of O2

52
Q

effect of pH and CO2 binding and release of O2 by Hb is called what? Where does it occur mostly? where is the opposite effect seen?

A

Bohr effect
in systemic capillaries
reverse of Bohr effect will occur in lung capillaries

53
Q

What does Bohr effect do?

A

changes Hb from R confirmation to T confirmation (lowers affinity for O2)

54
Q

What is carbon monoxide poisoning?

A

CO kills b/c it changes O2 binding at other Heme sites in Hb so Hb is in constant R confirmation - which wants to bind O2, so O2 is not released

55
Q

Why is CO potent?

A

produced naturally from incomplete combustion of organic matter

it is 200X more affinity at heme site than O2

56
Q

CO poisoning and sickle cell anemia

A

RBCs are fragile and only have 50% functional heme - CO competes for Hb, and changes other sites to R so O2 is not released (inc affinity of O2) –> allosteric effect

57
Q

is fetal Hb more or less susceptible to CO poisoning?

A

more b/c they have a different type of Hb

58
Q

What are the types of Hb?

A

HbA - major adult form (alpha2B2)
HbA2 - minor (2%, alpha2delta2)
HbF - major Hb in fetus and newborn - much higher affinity for O2 then HbA and does not bind will to BPG (alpha2gamma2)

59
Q

What is special about fetal Hb?

A

Fetal Hb needs to extract O2 from mother’s Hb b/c lungs are non-functional in fetus

60
Q

What is used for diagnosis and treatment of diabetes mellitus?

A

hemoglobin glycations
Hb is a long-lived protein and is susceptible to non-enzymatic glycosylation - glucose aldehyde forms Schiff base with free amines in protein

61
Q

what is a predictor of sustained hyper-glycemia?

A

glycosylated Hb levels in blood

62
Q

What are some hemoglobinopathies?

A

sicke cell anemia (HbS)
HbC
HbM (methemoglobin, (Fe3+, oxidized)
Thalassemias - Hb is not synthesized (one of the polypeptide chains)

63
Q

thalassemia

A

Hb is not synthesized

64
Q

What happens in sickle cell anemia HbS?

A

glutamate to valine mutation on protein surface (point mutation) - presents hydrophobic patch
Hb polymerizes forming long strands
RBC’s have sickled shape

in low O2 conditions, Hb goes in T confirmation (lo affinity) and RBC’s aggregate
Hb polymerizes b/c of valine on surface - creates long strains within RBC, which produces elongated shape

RBC is more fragile, breaks down, and gets sticky –> stuck in capillary beds –> hypoxia

65
Q

What happens in HbM?

A

histidine to tyrosine mutation
this stabilizes Fe3+ (oxidized form which won’t bind O2) so O2 can’t bind to Fe3+ in heme –> cyanosis
normally, Hb has Fe2+ (reduced form) so oxygen can bind to reduced Fe2+

Biochemistry (5 decks)

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