Related Essays

  • Shuffle
    Toggle On
    Toggle Off
  • Alphabetize
    Toggle On
    Toggle Off
  • Front First
    Toggle On
    Toggle Off
  • Both Sides
    Toggle On
    Toggle Off
  • Read
    Toggle On
    Toggle Off
Reading...
Front

Card Range To Study

through

image

Play button

image

Play button

image

Progress

1/191

Click to flip

Use LEFT and RIGHT arrow keys to navigate between flashcards;

Use UP and DOWN arrow keys to flip the card;

H to show hint;

A reads text to speech;

191 Cards in this Set

  • Front
  • Back
What do the number of protons, neutrons and electrons each specify for an atom?
Protons specify atomic number and elements. Neutrons specify isotopes. Electrons specify chemical reactivity
Which two of these specify atomic weight (mass)?
Protons and neutrons
Which two are always equal in number and why?
The number of proton and electrons is always the same to keep the electrical charge of an atom neutral
What physical parameter differentiates the isotopes of an element?
The mass of the atom
What is the difference between an electrostatic bond, a covalent bond and a covalent polarized bond?
In electrostatic bonds, electrons are donated, giving rise to charged particles, anions and cations (NaCl, CaHPO4). In covalent bonds, electrons are shared, forming molecules (glucose). A polarized bond creates a molecule in which part is electron-rich and part is electron poor.
Explain how this gives rise to hydrogen bonding in water.
In water (H2O), the polarized bond caused by the electron withdrawing property of the oxygen atom permits the more positively charged hydrogen atom to share oxygen atoms, maintaining a hydrogen bonded liquid
You found a single tooth of unknown origin.

What isotopic analysis would help you determine if it were recent or very old?
Ratio of C12 to C14
You found a single tooth of unknown origin.

What isotope would be missing if the tooth were more than about 40,000 years old?
C14
You found a single tooth of unknown origin.

Why would it be missing from the old tooth but still around today?
C14 has a half-life of 6,000 years and is constantly replenished by cosmic rays in the upper atmosphere. A dead body cannot take in new CO2 and its ratio of C14 to C12 decreases. If the tooth was more than about 40,000 years old, so little C14 would remain that only C12 would be detected
Define: respiration
Respiration is the production of energy (ATP) by oxygen gas oxidizing carbon compounds. Water (reduced oxygen) and CO2 (oxidized carbon) are the products, usually in mitochondria or their bacterial equivalent on the inner cell membrane (Slide 19).
Define: fermentation
Fermentation refers to the production of energy (ATP) from carbon compounds in the absence of molecular oxygen (Slides 19).
Name the two major classes of fermentations that utilize organic compounds?
Saccharolytic and asaccharolytic (Slides 21 and 22).
What pathway do saccharolytic fermentations utilize?
Glycolysis.
What is the starting substrate?
A free hexose such as glucose or fructose.
What is the primary end product?
Lactic acid.
What are the products of the reactions that use up ATP and the substrates and products of the two reactions that make ATP?
ATP is required to make hexose phosphate and fructose bisphosphate and ATP is made by converting glyceraldehyde-3-phosphate to 3-phosphoglycerate and PEP to pyruvate.
d) 2 ATP used but 4 ATP produced, giving a net production of 2 ATP/mole hexose (glucose or other sugar)
Why is there a net synthesis of ATP but no net synthesis of NADH?
NADH produced by oxidation of glyceraldehyde-3 phosphate to 3-phosphoglycerate is reoxidized to NAD by reducing pyruvate to lactate (Slides 19-21).
What is meant by an asaccharolytic bacterial fermentation.
) Utilizing non-sugar substrates to obtain energy for growth in the absence of oxygen (slides 19 -21).
What is the usual substrate?
Amino acids freed from proteins by proteolytic enzymes (Slide 22).
What are the two major end products that the bacteria excrete?
Ammonia from amino groups and short chain fatty acids. The short chain fatty acids are derived from enzyme shuffling the carbon skeletons of amino acids to obtain ATP and then reducing them with NADH (slides 20 & 22). [Note: Hydrogen sulfide is a minor end product because it is only derived from 2 of the 20 amino acids, cysteine and methionine.]
The gingival sulcus has a pH ~8 as a consequence of bacterial excretion of which of these bacterial fermentation end-products?
Ammonia.
What pathway in human tissues but not in bacteria avoids the production of this end-product during amino acid catabolism?
Urea cycle
How many cell membranes protect a gram negative bacterium?
Two, an inner and outer membranes separated by an inter-membrane space as in mitochondria (Slide 23)
What are the functions of its peptidoglycan and lipopolysaccharide?
Peptidoglycan is a rigid complex of protein and polysaccharide that maintains bacterial cell shape. Lipopolysaccharide is attached to the outer surface of the outer membrane and stimulates inflammation from an infected host (Slides 23 & 24).
Define: autotroph
Autotroph refers to an organism whose metabolism allows it to obtain all of its carbon from CO2, a gas.
Define: heterotroph
Heterotroph refers to an organism whose metabolism allows it to obtain its carbon from solid and liquid organic (carbon) compounds (food) (Slides 28 and 39).
What is the source (substrate) of electrons for both photosystems?
Water
What does photosystem I provide for the dark reaction (Calvin cycle) of chloroplasts?
PSI provides NADPH
What does photosystem II provide for the dark reaction (Calvin cycle) of chloroplasts?
PSII provides ATP.
What feature of the respective electron transporters results in the different products?
Photosytem I electron transporters pass hydride ions, not protons. Photosystem II electron transporters pass electrons and release protons which pass out of the thylakoid lumen to the leaf cytosol through an ATP synthase complex. (Slide 31)
What is the first product of the dark reaction?
The first product of the dark reaction is 3-phosphoglycerate from ribulose bisphosphate and CO2. (Slide 34)
What reaction of the Calvin cycle utilizes most of the photosynthesis end products?
Reduction of 3-phosphoglycerate to 3-phosphoglyceraldehyde (Slide 33)
Name the 6-carbon sugar that is first produced from photosynthesis?
The first 6-carbon sugar produced by photosynthesis is fructose-6-phosphate, a derivative of fructose (Slide 35)
A is the only Calvin cycle metabolite that moves into the cytosol from the chloroplast and B enters the chloroplast in exchange. What are A and B?
A. Dihydroxyacetone phosphate

B. Inorganic phosphate (slide 35
Why is inorganic phosphate (Pi) required in the chloroplast at night?
Break starch into glucose 1 phosphate to be utilized for energy. Pi is a co-substrate of phosphorylase (Slide 38)
Write the reaction that produces sucrose from glucose and fructose in plants.
UDP-Glc + Fru-6-phos → Sucrose 6-phosphate.
Name the enzyme.
The sucrose-6-phosphate is then hydrolyzed to sucrose and phosphate by sucrose phosphatase (slide 37)
Indicate what part of the leaf cell it occurs.
This reaction occurs in the leaf cell cytosol.
Is this the same part of the leaf cell where starch also first accumulates?
No. Starch first accumulates within chloroplasts (slide 36)
What is the enzyme that metabolizes sucrose for energy?
Invertase hydrolyzes the glucose-fructose bond to glucose and fructose. (Slide 38 2nd paragraph on right)
Where in the plant is sucrose mostly utilized?
Everywhere except in the leaf (Slide 38 1st paragraph on right)
Two other enzymes transform sucrose into an alternative storage polysaccharide outside the chloroplast. Name these two enzymes.
Sucrose phosphorylase and sucrose synthetase. Sucrose phosphorylase makes sucrose 6-phosphate and a reversal of the sucrose synthetase reaction hydrolyzes it to UDP glucose and fructose 6-phosphate as substrates for synthesis of various polysaccharides in addition to or instead of starch (Slide 37).
Match the following proteins or glycans (a through g) with their function (i through vii) in the connective tissue stroma:
a) Collagen fibers
b) Non-fibrillar collagens
c) Fibrillin
d) Thrombospondins
e) Integrins
f) Fibronectin
g) Hyaluronan


i) Resilience
ii) Strength
iii) Elasticity
iv) Foreign body reaction
v) Basal lamina
vi) Adherence of cells to stroma
vii) Adherence of cells that influences their activity.
a) – ii
b) – v
c) – iii
d) – iv
e) – vii
f) – vi
g) – i.
See Slides 42 through 47, but especially Slides 43, 44 & 47)
What amino acids primarily account for the secondary structure of collagen fibers?
Proline and hydroxyproline form the secondary structure (collagen helix). They promote an extended, coiled chain.
What amino acids primarily account for the tertiary structure of collagen fibers?
None. The chain does not fold back on itself.
What amino acids primarily account for the quaternary structure of collagen fibers?
Glycine has a hydrogen atom side chain that holds the tropocollagen triple helical monomer together. Serine and alanine have small side chains that permit tropocollagen to form side-by-side arrays that make up the collagen fibers (Slides 51 through 56, but especially slides 51, 55 and 56, item 2).
What are the two functions of hydroxyproline in the structure of collagen?
Contributes like proline to the helical tropocollagen polypeptides but stabilizes the extended chain at 37oC.
What is the effect of reduced hydroxyproline content on tropocollagen stability at 37oC?
Less hydroxyproline makes the extended chain less rigid, which prevents it from forming a triple helix at 37oC. Vertebrates such as cold water fish whose ambient temperature is 10 – 20oC have less hydroxyproline in their collagen, enabling their collagen fibers to melt at their body temperature of 10 – 20oC (Slide 55).
List four enzymes involved in the post-translational synthesis of a fibrous collagen prior to secretion
a) 2 hydroxylases (proline and lysine) and 2 procollagen peptidases (N-terminal and C-terminal peptidase)
Which of these enzymes adds the short glycan to hydroxylysine?
b) An isoenzyme (isozyme) of lysine hydroxylase, LH3
See slide 58, items 1 through 3 only
What two factors mediate triple helix formation by procollagen polypeptides in the endoplasmic reticulum?
1. C-terminal propeptide cystine bonds
2. A chaperone (hsp47) – Slide 59 (right side)
What are the 3 substrates, 3 products and 2 cofactors of proline (or lysine) hydroxylase?
Substrates: a) motif sequence containing pro (or lys) on procollagen
b) O2
c) α-ketoglutarate

Products: a) HO-pro (or HOlys) residue on procollagen
b) CO2
c) Succinate

Cofactors: a) Ferrous ions
b) Ascorbate (vitamin C)
(Slide 60)
What is ascorbate used for during collagen synthesis?
Transport of electrons to reduce a ferric ion in proline and lysine hydroxylase during the post-translational modification of collagen polypeptides in the rough ER (Slide 60).
What happens to make it deficient in the body?
It slowly disappears because its oxidized form reacts irreversibly with water to make another compound from which ascorbate cannot be regenerated (Slide 61).
How is this remedied?
The reduced form must be ingested by eating plant products especially fresh citrus fruits where this form is stable (Slide 63) – mentioned in class
What vitamin is ascorbate also known as?
Vitamin C (Slide 61)
What 2 processes make protein disulfide isomerase (PDI) an important polypeptide component of proline and lysine hydroxylases?
PDI catalyzes triple helix formation by reducing cysteine residues in the procollagen C-terminal propeptide region and passing them to oxidized glutathione (GSSG).
PDI independently regenerates ascorbate with electrons from reduced glutathione (GSH) (Slides 59 through 61; both processes are described in slide 61).
Collagen may be fibrillar or non-fibrillar, but N- and C-terminal procollagen proteases recognize only one of these groups. Which one and why?
Fibrillar Collagens!
The proteases that convert procollagen to tropocollagen recognize N- and C-terminal amino acid motifs (consensus sequences) not present on the non-fibrillar collagens (Slide 65). You need NOT remember these motifs, but they are given in the book in Chapter 8, section 8.2.1, Fibrillar Procollagen Processing.
What is tropocollagen?
The monomeric subunit precursor of collagen fibers (Slide 69).
) What is alpha (α), beta (β) and gamma (γ) tropocollagen.
) α-Tropocollagen is the monomeric polypeptide unit of collagen fibers. β- and γ-tropocollagen are post-translational modifications of α-tropocollagen. Beta-tropocollagen is a covalently linked tropocollagen dimer, and gamma-tropocollagen a covalently linked trimer (Slides 50 and 71).
What two amino acids and one enzyme are responsible for these differences?
Lysine and hydroxylysine residues. The enzyme is lysyl oxidase (Slides 72 & 73).
) What is the metal ion cofactor of this enzyme?
Copper (Slide 72)
If one were to cut out collagen fibers, subject them to amino acid hydrolysis in 6 M HCl and then examine the amino acid composition, which of the following would be found in increasing amounts with age?
a) Lysine b) Hydroxylysine c) Pyridinoline d) Proline e) Hydroxyproline.
c) Pyridinoline (Would have been discussed in lecture in connection with Slides 71 – 73; instead it is in the book, Chapter 4, section 4.2.2, ‘Fiber Cross-Linking: Formation of b- and g-Tropocollagen’ Go to the last paragraph beginning at the foot of p. 52).
In what tissue do type II collagen fibers appear?
Cartilage only (Slide 68).
What is the origin of the different types and numbers of alpha chains?
Different genes (Slide 68)
What is the origin of the differences between alpha, beta and gamma chains?
Post-translational covalent lysine crosslinking (Slides 72 and 73)
What are integrins?
Integral membrane proteins composed of alpha and beta chains (heterodimers). Each α- and β-polypeptide is one of a family and each member of the family (α1, α2, β1. β2 etc.) is encoded by a different gene. The extracellular domain of an integrin dimer possesses an N-terminal region that attaches a cell to a stromal protein such as collagen or laminin, and its C-terminal region responds to changes in the cytosol mediated by hormones and other growth factors such as cytokines.
What is meant by integrin ‘outside-in’ and inside-out’ signaling?
Outside-in refers to changes in stromal protein composition or conformation that affect integrin binding, thus altering the cytosolic conformation of the integrin so that the cell receives a signal from the exterior. Inside-out refers to internal cytosolic changes that alter the conformation to promote or inhibit binding to a stromal protein.
Give two major function of integrins in stromal collagen homeostasis?
To increase collagen synthesis after tissue damage (outside-in signaling) and to allow the cell to stop synthesizing collagen and divide in response to hormones and other growth factors (inside-out signaling).
(Slides 75 & 76).
What are the two histologically different components of basal laminas?
Lamina lucida and Lamina densa (slide 77).
Name the major classes of proteins associated with each component.
Laminin (lamina lucida) and non-fibrillar collagen (lamina densa).(Slide 77).
Name two functionally different members of the same family of proteins in a dermal-epidermal lamina?
Laminin-1 (meshwork) and laminin-5 (anchoring). Slides 77 & 78.
Which attaches basal epidermal cells to a tooth surface at the base of a gingival sulcus? e) Why?
Laminin-5 (Slide 80)
e) In the absence of a connective tissue stroma, neither laminin-1 nor type IV collagen is secreted into a basal lamina (Slide 80).
Name the 4 components of a hemidesmosome and describe their functions.
Two plakin proteins that attach the hemidesmosome to keratin filaments in the cytosol and two other proteins, integrin and collagen type XVII that protrude from the membrane and attach the cell to laminin-5 extracellularly (Slide 80, right side and Slide 85).
What connects the basal lamina to the dermis? To what basal lamina component does this connector bind?
Anchoring collagen type VII. The anchoring collagen attaches to laminin-5 which protrudes through the lamina densa (type IV collagen). (Slides 77 & 85)
What 2 features of a triple helix differentiate a non-fibrillar collagen from a fibrillar collagen? They also differ in two other ways. What are they?
i. Procollagen N and C domains are incompletely or not removed.
ii. Cross-links are mediated by cysteine residues in the interrupted triple-helical region, not lysine/hydroxylysine residues (Slide 86). This is also true of type IV collagen (Slide 83)
NOTE: Non-fibrillar collagens do not bind lysyl oxidase.
What type of fiber does fibrillin make?
An elastic fiber (slide 89)
What do a) fibrillin b) collagen fibers look like under an electron microscope?
a) Beads on a string (Slide 89 #5)
b) Striated fibers (Slide 68 #1)
Name three key features of fibrillin structure.
) 1 – The C-terminus of each fibrillin polypeptide binds to the N-terminus of another fibrillin polypeptide to form a covalent polypeptide dimer that lengthens into a polymer (Slide 93)
2 – Domains around each N-C bond region in the polymer bind to calcium ions and fold with other proteins into thick beads connected by unfolded helical regions (Slide 93).
3 – The unfolded helical regions are held in the relaxed (unstretched) state by calcium ions. (Slides 92 & 93)
What role does glutaminase play in fibrillin structure?
Strengthens the bead domains by covalently bonding adjacent lysine and glutamine residues within the beads. (Slides 94 & 100)
Name another important protein whose structure is stabilized by glutaminase (You should have heard of this protein during the last section of your Fall semester Biochemistry Course).
Fibrin – see file: Transglutaminase & fibrin.pdf (From Dr DeAngelis’s fall lecture on blood clotting)
What is the name for the precursor of elastin?
Tropoelastin (Slide 96)
When secreted in developing tissues, this precursor protein loses X and binds to Y and then to Z. What are X, Y and Z?
X is a chaperone; Y is microfibril-associated glycoprotein-1 (MAGP-1); Z is fibrillin-2 (Slide 97).
To which domains do each bind?
The chaperone binds to the hydrophobic portion of the enzyme. MAGP-1 replaces the chaperone and allows the acidic residues of fibrin to bind to the precursor’s basic (lysine-rich) domains (KA and KP domains; slide 97).
What is unusual about elastin with respect to its gene and its stability?
A greater ratio of introns to exons than any other mammalian polypeptide. Also stable for longer than any other mammalian protein (slides 96).
To what does coacervation during elastic fiber development refer?
Coacervation refers to newly secreted tropoelastin molecules that have undergone a major realignment that moves its attached fibrillin microfibers from the outer surface to the inner surface of the elastin.
How is it controlled?
It is initiated from a small portion of the polypeptide encoded by one of the many hydrophobic domains.
What process follows it?
Crosslinking of polypeptides by lysyl oxidase producing desmosine crosslinks from lysine residues
(Slides 98 & 100).
Explain how desmosine contributes to the elasticity of elastin.
The cross-linker, desmosine, forms a knot such as in a net or hammock. It ties 4 elastin polypeptides together (Slides 98 & 99). In the polymer, each elastin polypeptide has hydrophobic residues that are exposed to water when elastin is stretched. Once the stretching force is released, the exposed hydrophobic residues form a coil to be free of contact with the water (Slide 99).
What tissues contain the most elastin?
Artery walls and ligaments (stated in the lecture)
List the two sugars that make up a repeating dimer within hyaluronan, chondroitin sulfate, keratan sulfate and dermatan sulfate.
Hyaluronan – Glucuronate and N-acetyl glucosamine
Chondroitin sulfate – Glucuronate and N-acetyl galactosamine
Keratan sulfate – Galactose and N-acetyl glucosamine
Dermatan sulfate – Iduronate and N-acetyl galactosamine (See slide 110)
Which of these has no attachment to a protein core?
Hyaluronan (slide 113)
What is the anomeric bond between these glycan residues?
They are beta-anomeric bonded (slides 104 and 110)
Is this the same as in glycogen, starch and cellulose?
Same as cellulose, but glycogen (and starch) glycan units are connected by alpha-anomeric bonds
Name two proteins to which a glycosaminoglycan is attached, one in the connective tissue dermis and the other in cartilage.
Decorin and aggrecan (Slide 107).
With what collagen molecules are these proteins and most associated?
Type I collagen fibers (decorin) and type II collagen fibers (aggrecan) See slide 109.
List the major, non-covalently connected components of: Cartilage
Type II collagen, hyaluronan, aggrecan, and link protein (slide 109)
List the major, non-covalently connected components of: Epidermal basement membranes
Laminin and type IV Collagen (slide 109). Note: Type XVII collagens and an integrin hold the basal lamina to the basal layer of epidermal cells. Type VII collagen holds the basal lamina to deeper type I collagen fibers (slide 79, 80 & 83). The linker is laminin-5 which protrudes through the lamina densa (type IV collagen layer).
List the major, non-covalently connected components of: Dermis of the skin and oral mucosa
Type 1 collagen, decorin, fibronectin, fibrillin and elastin (slide 109). Note: Integrins are part of the cells. Fibronectin (slide 43) is part of the extracellular dermis and other solid tissues. It is absent from cartilage and basement membranes.
What feature determines the protease families?
The amino acid residue or metal ion most associated with peptide cleavage (Slide 116).
Identify to which family each of the following proteases belongs to: furin
serine protease
Identify to which family each of the following proteases belongs to: pepsin
aspartate protease
Identify to which family each of the following proteases belongs to: collagenase
metalloprotease (zincin)
Identify to which family each of the following proteases belongs to: trypsin
serine protease
Identify to which family each of the following proteases belongs to: gelatinase
metalloprotease (zincin)
Identify to which family each of the following proteases belongs to: anthrax toxin protease
metalloprotease (zincin)
Identify to which family each of the following proteases belongs to: caspase
cysteine protease
Identify to which family each of the following proteases belongs to: proteasomal digestive protease
threonine protease (Slides 116 &117)
Name the three classes of matrix metalloproteases associated with fibrous collagen processing and degradation?
Astacins, adamalysins and matrilysins (Slide 117)
NOTE: Only matrilysins are matrix metalloproteases!
For each, indicate the number and types of ions involved in maintaining the structure and activity of the catalyic domain.
Astacins, 1 (Zn); Adamalysins, 2 (Zn and Ca); Matrilysins, 4 (2 Zn & 2 Ca) Slide 114
Note: In Chapter 8, Fig. 8.3, the calcium ion in adamalysins is accidentally omitted although stated as present in the figure legend. Your Slide 118 on p. 59 is correct.
What is the function of furin in relation to the procollagen peptidases?
Removes a propeptide to activate them (Slide 122)
What enzyme replaces that function of furin for matrilysins?
Plasmin (Slide 125)
How are furin and this other enzyme activated?
Furin is self-activated in the endoplasmic reticulum (Slides 118 & 119;) plasmin is made by a cutting off a propeptide from plasminogen by plasminogen activators activated in the stroma (Slide 125)
What types of enzymes are furin and this other enzyme?
Serine proteases
Cleavage of the N-terminal propeptide of matrilysins and adamalysins removes an amino acid residue that binds to the zinc ion: What is this residue?
A cysteine residue (Slides 119 & 120).
Cleavage of the N-terminal propeptide of matrilysins and adamalysins removes an amino acid residue that binds to the zinc ion: How does it function?
The cysteine –SH group bonds with the zinc ion and prevents a water molecule from binding (NOTE: slide 119 shows the OH group of tyrosine which acts instead of cysteine in astacins).
Cleavage of the N-terminal propeptide of matrilysins and adamalysins removes an amino acid residue that binds to the zinc ion: What other amino acid residue is involved in mediating the hydrolysis?
A glutamate residue that swings to position and activates the Zn ion-bound water molecule for catalysis (Slide 120).
Does not cut all three polypeptides of a collagen triple helix simultaneously
Neutral gelatinase (slide 127)
This adamalysin is attached to an integrin on the fibroblast or chondroblast surface where it processes most fibrous procollagens.
Procollagen-N-peptidase (slides 122 & 124)
A matrilysin secreted by neutrophilic white blood cells to hydrolyze intact collagen fibers at a site of tissue damage.
Neutral collagenase (slides 126 & 128)
This astacin completes tropocollagen fiber formation after secretion.
Procollagen-C-peptidase (slides 122 & 123, item 1).
Mutations that inactivate this adamalysin cause some types of Ehlers-Danlos Syndrome
Procollagen-N-peptidase (slide121)
Match the metal ions with the appropriate enzyme(s) or protein(s) involved in collagen or elastic fiber metabolism and indicate the function.
Match: Iron, Zinc, Copper, Calcium
With: Fibrillin, Astacin, Lysine hydroxylase, Lysyl oxidase.
Iron – Lysine hydroxylase (slide 60)
Zinc – Astacin (slide 118) – no calcium ions in astacins such as procollagen C peptidases!
Copper – Lysyl oxidase (slide 72)
Calcium – Fibrillin (slide 93)
What is an apatite?
An apatite is a crystal that forms from calcium monohydrogen phosphate. If carbonate replaces some of the phosphate ions, the result is a carbonated apatite. Carbonated apatite is often called carbonated hydroxyapatite, as in the slides. Carbonate ions replace phosphate ions, but they may additionally replace a hydroxide ion at high carbonate ion concentrations.
What major proteins contribute to calcification in enamel and bone?
Enamel – Amelogenin; Bone – Collagen type I (Slide 133, Item 3)
What is nucleation?
Nucleation is required to precipitate a supersaturated solution of calcium phosphate (Slide 132).
Which of these proteins is actually calcified?
Collagen type I (Slide 133, Item 4)
What cells of the undifferentiated tooth bud give rise to ameloblasts?
Inner enamel epithelium
Where do odontoblasts differentiate?
Dental papilla
Which cells differentiate and secrete their product first, odontoblasts or ameloblasts?
Odontoblasts
After what event does amelogenin start to be secreted in the tooth bud?
Newly calcified collagen fibers of dentin coming into contact with the inner enamel epithelium (slide 134).
What enzyme processes amelogenin so that it forms large nanospheres aggregates on carbonated hydroxyapatite ribbons within the developing enamel matrix?
Enamelysin
What class and subclass of enzyme is it?
Zincin Matrilysin. (Slide 138)
Match the following proteins with their function.
Proteins: a) Ameloblastin; b) Enamelin; c) Enamel matrix serine protease-1; d) Collagenase; e) Amelogenin:
Functions: 1) Forms nanospheres; 2) Degrades nanospheres; 3) Holds large nanospheres together; 4) No role; 5) Delineates inter-rod region.
a) Ameloblastin – 5 (Slides 137)
b) Enamelin – 3 (Slides 137, 139 & 140 #5)
c) Enamel matrix serine protease-1 – 2 (Slides 138 & 139)
d) Collagenase – 4
e) Amelogenin – 1 (Slide 139)
What feature of amelogenin causes it to form nanospheres?
It is strongly hydrophobic (side 136)
What two regions initially hold nanospheres to carboxyapatite ribbons?
The amelogenin C-terminal domain and the amelogenin serine phosphate in the N-terminal TRAP region (slides 136 & 139)
Loss of which region causes large nanosphere aggregations to form on the ribbons.
The C-terminal domain (slides 136 &139)
What is the purpose of the nanosphere aggregations?
Increase carbonated apatite ribbon length (long axis) over thickness
(Slide 139 & Slide 140, item 5)
What does the Tomes process do?
The organ of the ameloblast that secretes the proteins required to make enamel matrix (Slide 135)
Which cells differentiate and secrete their product first, odontoblasts or ameloblasts?
Odontoblasts
After what event does amelogenin start to be secreted in the tooth bud?
Newly calcified collagen fibers of dentin coming into contact with the inner enamel epithelium (slide 134).
What enzyme processes amelogenin so that it forms large nanospheres aggregates on carbonated hydroxyapatite ribbons within the developing enamel matrix?
Enamelysin
What class and subclass of enzyme is it?
Zincin Matrilysin. (Slide 138)
Match the following proteins with their function.
Proteins: a) Ameloblastin; b) Enamelin; c) Enamel matrix serine protease-1; d) Collagenase; e) Amelogenin:
Functions: 1) Forms nanospheres; 2) Degrades nanospheres; 3) Holds large nanospheres together; 4) No role; 5) Delineates inter-rod region.
a) Ameloblastin – 5 (Slides 137)
b) Enamelin – 3 (Slides 137, 139 & 140 #5)
c) Enamel matrix serine protease-1 – 2 (Slides 138 & 139)
d) Collagenase – 4
e) Amelogenin – 1 (Slide 139)
What feature of amelogenin causes it to form nanospheres?
It is strongly hydrophobic (side 136)
What two regions initially hold nanospheres to carboxyapatite ribbons?
The amelogenin C-terminal domain and the amelogenin serine phosphate in the N-terminal TRAP region (slides 136 & 139)
Loss of which region causes large nanosphere aggregations to form on the ribbons.
The C-terminal domain (slides 136 &139)
What is the purpose of the nanosphere aggregations?
Increase carbonated apatite ribbon length (long axis) over thickness
(Slide 139 & Slide 140, item 5)
What does the Tomes process do?
The organ of the ameloblast that secretes the proteins required to make enamel matrix (Slide 135)
What is it gradually replaced with on either side?
A ruffled membrane (Slide 144, item iii)
What does the replaced structure do?
Excretes calcium phosphate and absorbs peptides as the matrix is removed and calcification peaksto complete mineralization (Slide 144, item iii)
Primary and secondary amelogenesis imperfecta are differentiated by their systemic effects; the presence of disease elsewhere in the body, not just the teeth. a) Which has no systemic effects?
The primary form has no systemic effects – only the enamel is affected.
Mutations to which of the following proteins are responsible for primary amelogenesis imperfecta, secondary amelogenesis imperfecta or neither: Fibrillin; integrin; amelogenin; enamelysin.
Fibrillin – secondary
Integrin – neither
Amelogenin – primary
Enamelysin – primary (Slides 142 & 143)
Why do mutations of type I collagen polypeptides, but not of type II or other collagen polypeptides associate with secondary amelogenesis imperfecta?
Dentin calcification is necessary to orient enamel crystals and that requires only type I collagen (Slides 142). Other types of collagen do not calcify.
Osteoblasts concentrate free calcium ions in osteoid (extracellular) matrix vesicles. Protein A transports calcium ions from blood plasma across the osteoblast and extrudes them into the osteoid extracellular matrix. Protein B transports them from the osteoid matrix into vesicles: name proteins A and B.
A: Calbindin (slide 148); B: Annexin (slide 151)
When osteoid matrix vesicles are extruded into the extracellular osteoid matrix, what ions are transported inside?
Calcium and phosphate ions.
What extracellular ion spontaneously diffuses through the matrix vesicle from the extracellular fluid and gets transported OUT?
Sodium ions.
How is the energy for this outward transport initiated and maintained?
The energy is due to calcium phosphate precipitating around phosphatidylserine inside matrix vesicles. The low concentration of free calcium and phosphate ions in solution causes phosphate ions to move in spontaneously, driving the sodium ions out.
During this process where does the matrix vesicle go?
From the osteoblast surface to the new bone surface (Slides 149 & 151).
The osteoid matrix possesses relatively high concentrations of type I collagen fibers, calcium ions and monohydrogen phosphate ions:

What small molecule prevents premature nucleation of this matrix?
Pyrophosphate – PPi (slide 152, item 3, & slide 154).
The osteoid matrix possesses relatively high concentrations of type I collagen fibers, calcium ions and monohydrogen phosphate ions:

What protein transports this inhibitor from the cytosol of osteoblasts to the osteoid matrix?
PPi transporter called the ANK (ankylosis) protein (slide 154).
The osteoid matrix possesses relatively high concentrations of type I collagen fibers, calcium ions and monohydrogen phosphate ions:

What enzyme on the outer surface of matrix vesicles makes more of this inhibitor?
NTP-PPi hydrolase (slide 154).
The osteoid matrix possesses relatively high concentrations of type I collagen fibers, calcium ions and monohydrogen phosphate ions:

What is the major substrate of this enzyme?
Extracellular ATP (slide 154).
The osteoid matrix possesses relatively high concentrations of type I collagen fibers, calcium ions and monohydrogen phosphate ions:

What change in the matrix vesicles activates an enzyme that removes this inhibitor?
Calcified material ruptures the vesicle (Slide 152, item 1).
The osteoid matrix possesses relatively high concentrations of type I collagen fibers, calcium ions and monohydrogen phosphate ions:

What is the name of this enzyme?
Alkaline phosphatase, also called tissue non-specific alkaline phosphatase, TNAP (Slides 155 & 158, item 6).
How does collagen nucleate calcium phosphate precipitation around itself?
By the spontaneous covalent attachment of phosphate ions to serine residues sticking out from gaps in the array of type I collagen fibers in the osteoid matrix (slide 152, item 4).
Which protein in bone prevents excessive calcification at the bone surface?
Osteocalcin
What amino acid is modified in this protein and important for its action?
Glutamate
What cofactor binds to an adjacent domain to process this modification?
Vitamin K
What dietary factor activates the synthesis of this protein in osteoblasts?
Vitamin D (slide 159)
What does the term ‘SIBLING proteins’ mean?
Small integrin binding ligand N-linked glycoproteins.
These proteins have a double binding specificity. What are they?
One surface binds to an integrin on the surface of an odontoblast or osteocyte process and the other binds to hydroxyapatite or calcium ions.
What important bone and dentinal structures are SIBLING proteins best known to form?
They limit calcification, especially around osteocyte or odontoblast processes, forming canaliculi or tubules
Name one sibling protein prominent in bone and one prominent in dentin. .
Bone sialoprotein or matrix extracellular phosphoglycoprotein in bone; dentin matrix protein-1 or dentin sialophosphoprotein in dentin (slide 160)
There are two zincin enzymes involved in osteoblast functioning, one in development and the other during function. What are their names?
Bone morphogenic protein, an astacin (slide 148, item 1) and alkaline phosphatase (slide 155).
What are the functions of vitamins A, C, D and K in the formation of enamel, dentin and bone?
Vitamin A – differentiation of ameloblasts
Vitamin C – type 1 collagen
Vitamin D – transfer of calcium ions through osteoblasts to osteoid matrix
Vitamin K – formation of osteocalcin that controls bone thickness
(Slide 164)
Primary amelogenesis imperfecta, dentinogenesis imperfect type II, and osteogenesis imperfecta all lead to improperly calcified or absent teeth. Name a key protein that is mutated or not produced in proper amounts for each disease.
Primary amelogenesis imperfecta – Amelogenin, enamelysin or ameloblastin (slide 142)
Type II dentinogenesis imperfecta – Dentin sialophosphoprotein (DSPP) (slides 162 & 163)
Osteogenesis imperfecta – Type I collagen – (slide 162)
Apart from its multinuclear composition, what is the other major feature of a fully differentiated osteoclast? Describe three functions of this feature?
A ruffled membrane whose functions are to: 1) seal an osteoclast demineralizing compartment; b) acidify the compartment; and c) form transport the products of demineralization through the cell to the periosteum and blood (Slides 169 & 170).
What are the three major products of osteoclast action?
Calcium ions, phosphate ions, and collagen peptides
Name an important protease secreted into the acidic compartment of osteoclasts.
Cathepsin K, a thiol (cysteine) protease.
Why is this protease not a matrilysin?
The demineralizing compartment has a pH of 4.5, too low for matrilysins which act mostly at neutral pH.
What is the collagen substrate?
Type I collagen (Slides 171 & 172).
Name an important minor product of osteoclast action that is found in vesicles that are endocytosed out of the acidic compartment. What is the function of that product and how does it get to its site of action?
Transforming growth factor-β (TGF-β) and acid phosphatase; TGF-β activates osteoblasts in the periosteum. It is released from bone in the demineralizing compartment and is incorporated into endocytotic vesicles which transfer it to the periosteum Slides 168 & 174).
How does HCl reach the interior of the ruffled membrane compartment of osteoclasts?
H+1 and Cl-1 ions reach the acidic compartment independently. Protons are transported into the ruffled membrane in exchange for Na+ ions (present with calcium and phosphate in the sealed extracellular resorption compartment). Independently, chloride enters the cell in exchange for bicarbonate and diffuses into the resorption compartment through a chloride ion channel in the ruffled membrane. The acidic compartment remains electrically neutral by losing Na dihydrogen phosphate from bone (NaH2PO4) through a proton-dependent phosphate transporter. Dihydrogen phosphate (H2PO4-1) is exchanged for monohydrogen phosphate (HPO4-2) in extracellular fluid, and Na+ ions for K+ in extracellular fluid by the ATP-mediated Na+/K+ exchanger used by all cells. Some Na+ ions in the cytosol interact with carbonic acid to form the bicarbonate which is excreted in exchange for chloride (Slides 171 & 172).
What are bisphosphonates related to?
Pyrophosphate.
Why do some reduce bone resorption more than bone deposition?
All bisphosphonates have a substituted central carbon atom that causes the outer phosphate residues to bind strongly to bone and slow demineralization by preventing proton access (Slide 167, at foot of p. 88 in your handout). Note: Commonly prescribed bisphosphonates such as Fosamax do not inhibit bone formation unless taken at 5 – 10 times the recommended dose.
What physical effect stimulates osteoclast development? What two things are induced to bring this about?
Stress! Stresses cause micro-cracks in the trabecular and cortical bone. The micro-cracks attract monocytes from periosteal blood capillaries and causes adjacent osteoblasts to produce membrane colony stimulating factor (mCSF) which stimulates monocytes to attach, grow and form osteoclast precursors (Slides 162 & 169).
What is osteoprotegerin and how does it work?
Osteoprotegerin is a secreted osteoblast protein whose structure resembles the osteoclast differentiation and activation receptor, ODAR. It inhibits bone loss by interfering with the binding of osteoclast differentiation factor (a ligand) to ODAR on osteoclast precursor cell surface;
What cell secretes it?
It is secreted mainly by osteoblasts and osteoblast-like cells;
What is its other name?
Its other name is secreted RANK protein (secreted Receptor Activator of Nuclear factor KappaB protein). Note: ODAR is known as RANK, ODF as RANK ligand and OPG as secreted RANK (Slides 175 through 177).
Why does the onset of menopause cause osteoporosis?
At menopause, the loss of estrogen stimulates osteoblasts to secrete osteoclast differentiation factor (ODF), causing a sharp burst of bone loss. Only after a few years is there is an accompanying increase in osteoprotegerin (OCIF) which binds to ODF before it can activate osteoclasts by binding to ODAR (slides 177 & 178, item v).