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Amino acids > Lecture 4 > Flashcards

Lecture 4 Flashcards

1
Q

Hemeproteins

A

Specialized proteins that contains heme as a prosthetic group.

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2
Q

Heme function

A
  • Reversibly binds oxygen, each heme group contains an iron atom.
  • Electron carrier in cytochrome.
  • Catalyzes the breakdown of hydrogen peroxide.
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3
Q

Myoglobin

  • Function
  • Consists of
  • Type of amino acids
A
  • Reservoir for oxygen and as an oxygen carrier.
  • A single polypeptide chain.
  • Non- polar AA.
  • Charged AA are located on the surface.
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4
Q

Hemoglobin

  • Found in
  • Function
  • Composed of
A
  • Red blood cells.
  • Transport oxygen from the lungs to the capillaries.
  • 4 polypeptide chains: 2 alpha and 2 beta chains.
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5
Q

Why myoglobin affinity for oxygen is higher than hemoglobin?

A

Because it has a proximal histidine group that helps it bind oxygen.

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6
Q

T and R forms of hemoglobin

A

T form: less affinity for O2, tense state, deoxyhemoglobin, weak ionic and H bonds.

R form: relaxed state, oxyhemoglobin, ionic and H bonds are broken.

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7
Q

Allosteric effects

A

Binding O2 to one of the subunits is affected by its interactions with other subunits.

  • pO2
  • pH of the environment
  • pCO2
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8
Q

Bohr effect

A

An acidic environment reduces the oxygen affinity of Hb

-Protons are released from Hb when O2 binds

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9
Q

Effect of CO2

A

CO2 reduces the oxygen affinity of hemoglobin by covalent binding to the terminal amino groups of the alpha and B chains

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10
Q

Effect of 2,3- bisphosphoglycerate on Oxygen Affinity

A
  • Binds to the T conformation
  • BPG decreases the oxygen- binding affinity.
  • Enhances the unloading of oxygen in the tissues.
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11
Q

Binding of CO

A
  • It has a much higher affinity to iron than O2.

- CO and O2 compete for the same binding site.

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12
Q

Fetal Hemoglobin (Hb F)

A
  • Major Hb found in newborns.
  • Higher affinity to O2, because it binds weakly to 2,3- BPG.
  • Higher affinity facilitates the transfer for oxygen from the maternal circulation across the placenta.
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13
Q

Hemoglobinopathies

A

Disorders caused by the production of abnormal hemoglobin molecule or synthesis of insufficient quantities of normal hemoglobin.

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14
Q
  1. Sickle cell anemia

2. Hemoglobin C disease

A
  1. Glutamic acid is replaced by Valine.

2. Glutamic acid is replaced by Lysine.

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15
Q
  1. B- Thalassemias

2. A- Thalassemias

A
  1. B- globin chains is decreased or absent.

2. A- globin chains is decreased or absent.

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16
Q

Fibrous proteins

- 3 different structures

A
  1. Alpha helix cross-linked by disulfide bonds.
  2. Beta conformation
  3. Collagen triple helix
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17
Q

Collagen

  • Characteristics
  • Types
A
  • Most abundant protein in the human body.
  • Left- handed helix.
  • 3 AA residues per turn.

-Fibril- forming (type I, II, III), Network- forming (IV, VIII), Fibril- associated (IX, XIII).

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18
Q

Collagen structure

A
  • Triple helix
  • Alpha chains (left handed helix)
  • Rich in proline and glycine
  • Glycine is found IN EVERY THIRD POSITION
  • Stabilized by hydrogen bonds

Gly- X- Y
X: proline
Y: hydroxyproline.

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19
Q

Osteogenesis imperfecta

A
  • Brittle bone syndrome.
  • Collagen related disease.
  • Gly is replaced by bulky side chains (big)
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20
Q

Plasma Proteins - Blood

-Composition

A

Composed of an aqueous solution containing molecules of varying sizes and a number of cellular elements.

21
Q

Plasma vs. Serum

A

Plasma: treated with anticoagulant, contains clotting proteins
Serum: it is allowed to clot, absence of fibrinogen.

22
Q

Major functions of blood

A

Respiration: transport of O2 from the lungs to the tissues.
Regulation of body temperature.
Excretion transport of metabolic wastes to the kidneys and intestines for removal.
Transport: of hormones, metabolites..
Coagulation

23
Q

Plasma consists of:

A 
Water
Proteins 
Electrolytes 
Metabolites 
Nutrients
24
Q

Oncotic pressure

Hydrostatic pressure

A
  • Pressure created by water moving across a membrane due to osmosis (from the outside, to the inside).
  • From inside to the outside.
25
Q

Plasma proteins

-Functions

A

Transport: albumin, transferrin
Inflammatory responses: acute phase response proteins.
Immune defense: immunoglobins, complement proteins
Antiproteases: a1- antitrypsin, a2- macroglobulin
Blood clotting: coagulation factors, fibrinogen

26
Q

Plasma proteins

  • Place of origin
  • Separation methods
A

Synthesized by the liver or immunoglobulins (produced by plasma cells of the bone marrow).

Salting- out methods (fibrinogen, albumin, globulins).
Electrophoresis (albumin, a1 and a2 globulins, B and Y globulins)

27
Q

Albumin

  • Synthesis
  • Structure
A
  • Liver produces it, it is synthesized initially as a preprotein, its signal peptide is removed as it passes into the rough endoplasmic reticulum.
  • ellipsoidal shape, does not increase the viscosity of the plasma, isoelectric pH of 4.7
28
Q

Functions of Albumin

A
  • Colloidal osmotic pressure
  • Transport function: it has the ability to bind to various ligands, acting as a transporter.
  • Nutritive function: source of AA for tissue protein synthesis
  • Buffering action: it has the maximum buffering capacity, due to the large nummber of histidine.
  • Transport of hydrophobic fat acids
29
Q

Clinical significance of albumin

A
  • Blood brain carrier
  • Drug interactions
  • Hypoalbuminemia (lowered level of albumin)
  • Hyperalbuminemia
30
Q

Haptoglobin

A
  • Plasma glycoprotein that binds extra-corpuscular hemoglobin in tight non- covalent complex.
  • Function is to prevent loss of free hemoglobin into the kidney.
  • Helps to conserve iron.
  • When haptoglobin is present, hemoglobin is catabolized y the liver and iron is conserved.
31
Q

Haemopexin

A
  • B- globulin that binds free heme.
  • Synthesized in liver.
  • Bind heme formed from breakdown of Hb and other hemoproteins.
32
Q

Transferrin

A
  • Transports iron to where it is required.
  • B- globulin.
  • Synthesized in the liver.
  • It is a glycoprotein.
33
Q

Ceruloplasmin

A
  • Copper containing a2- globulin.
  • Glycoprotein with enzyme activites.
  • Blue color.
  • Each molecules bind 6 atoms of copper very tightly.
  • Albumin donates its copper to tissues more readily than ceruloplasmin.
34
Q

a2- macroglobulin

A
  • Major component of a2- globulin.
  • Synthesized by hepatocytes and monocytes.
  • Binds a great variety of proteases.
  • Protease- inhibitor complexes are ingested by phagocytes and degraded in lysosomes.
35
Q

a1- antitrypsin

A
  • Single chain of 394 amino acids, contains 3 oligossacharide chains.
  • Synthesized by hepatocytes and macrophages.
  • Principle serine protease inhibitor of human plasma.
  • It inhbits elastase, trypsin, other proteases by forming complexes with them.
  • It can be inactivated by smoking.
  • It protects the lung tissue from proteases released from macrophages.
36
Q

Inflammatory response proteins

A
  • Synthesis is controlled by cytokines and stress hormones.

- Levels change during infections and inflammation.

37
Q

C reactive protein

A
  • Reacts with C polysaccharide of capsule of pneumococci.

- Synthesized in liver.

38
Q

a1- acid glycoprotein

A
  • Acts as a transporter of progesterone.
  • Transports carbohydrates to the site of tissue injury.
  • Marker of acute inflammation.
  • Increase concentration: inflammatory diseases
  • Decrease concentration: liver disease
39
Q

Immune System

-Cells

A 
T lymphocytes (T cells): from thymus 
B lymphocytes (B cells): from bone marrow 
Antibody = immunoglobulins
40
Q

Antibody- Antigen interaction

A

Antigen: any molecule that induces the formation of a matching antibody.
It has to be large
It has to be a foreign molecule

41
Q

Structure of immunoglobin

-TRY TO LABEL THE PICTURE

A
  • 4 disulfide bonded polypeptides.
  • 2 identical light chains
  • 2 identical heavy chains
  • Y shape
  • Hinge region
  • 2 antigen- binding fragments (Fab)
  • 1 crystallizable (Fc) fragments
42
Q

Ig light chains

A

Two types

  • Kappa
  • Lambda
  • One Ig molecule contains: two K or two l light chains
  • K chains are more frequent.
43
Q

Ig classes

  • Defined by..
  • Name all of them
A
  • by their heavy chains
  • IgG, IgA, IgD, IgE and IgM

GIULIA AMA DOCE E MORANGO

44
Q
  1. IgG

2. IgA

A
  1. main antibody in the secondary response, enhances bacterial killing, crosses the placenta.
  2. prevents attachment of bacteria and viruses to mucous membranes, does not fix complement.
45
Q
  1. IgD

4. IgE

A
  1. found on the surface of B cells, where is acts as a receptor for antigen
  2. main host defense against heminthic infections, causes release of mediators from mast cells and basophils upon exposure to antigen.
46
Q

IgM

A

Produced in the primary response to an antigen, does not cross the placent, fixes complement, antigen receptor in the surface of B cells.

47
Q

Plasma electrophoresis

  • Major fractions
  • STUDY THE GRAPHIC
A
  • Albumin
  • a1- globulins
  • a2- globulins
  • B- globulins
  • y- globulins
48
Q

Monoclonal Gammopathies

A
  • Overproduction of a single antibody.

- Sharp peak on plasma protein electrophoresis.

Amino acids (6 decks)

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