Biochemistry

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captnslo
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Biochemistry
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2010-11-17 14:47:55
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Optometry biochemistry Test
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Biochemistry of the Eye; SCO powerpoint slides
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  1. Functions of a healthy tear film
    • Optical clarity and refractive power
    • Ocular surface comfort; lubrication
    • Protection
    • Environment for corneal epithelium
  2. Definition of Dry Eye
    • multifactorial disease of tears and ocular surface
    • Symptoms: discomfort, visual disturbance, tear instability, and potential damage to ocular surface
    • Increased osmolarity of tear film
    • inflammation of the ocular surface
  3. Progression of Dry Eye
    • Increase in the osmotic gradient between the tear film and the ocular surface
    • Increases conjunctival cell desquamation.
    • Disease first affects the conjunctival morphology while the corneal morphology initially remains normal.
  4. Further Dry Eye Progression
    • attachments between corneal cells loosen
    • increase in corneal desquamation
    • severe corneal epithelial changes: glycoprotein loss and destabilization of the cornea-tear interface
  5. Artificial Tears' goal
    • replenish eyes' tears
    • delay evaporation of patients' tears
  6. Components of Artificial Tears
    • Demulcent (hydrogels)
    • Preservative
    • Buffer (oil gelling agent ions)
    • does not contain growth factor or anti-inflamatory components
  7. Artificial Tears Summary
    • Pros:
    • viscosity of polymers minimizes thinning of tear film
    • Provide temporary palliative relief
    • avoid repeated use of banzalkonium chloride (BAK), which is toxic with multiple doses per day
    • Cons:
    • fail to break the cyclic inflammatory nature of dry eye
    • lack proteins and nutrients found in normal, healthy tears
  8. Steroid Treatment
    • Prescribed in pulsated, tapered therapeutic modality (fancy word for "treatment")
    • start 3-4 times a day and taper to 2x/week
    • mild steroid is Loteprednol (Lotemax by Bausch and Lomb)
  9. Restasis
    • cyclosporine opthalmic elulsion 0.05%
    • topical anti-inflammatory
    • for moderate to severe dry eye
    • Side effects: burning, conjunctival heperemia, discharge, epiphora (overflow of tears), eye pain, foreign body sensation, pruritus (itch), stinging, and blurring
    • Function: prevents T cells from releasing cytokines
    • Dosing: one drop twice/day
    • Takes 3-4 months for relief to start
  10. Proteins
    • amino acids are fundamental building blocks
    • created from peptide bonds
    • 3 divisions: Peptides (molecular weight below 10,000), Proteins (molecular weight above 10,000), Polypeptides (basically another name for protein)
  11. Role of proteins in eye
    • Mechanical support
    • Clarity of cornea and refraction properties
    • Electrical signaling
    • Protecting eye through lysis of bacteria (tears)
  12. Classification of Aminoacids
    • Acidic (more than one carboxylic group; ex: aspartic acid, glutamic acid)
    • Basic (more than one amino group; ex: lysine, arginine)
    • Neutral (equal number of amino and carboxylic acid groups; ex: alanine, glycine)
  13. Amino Acid Types
    • Unsubstituted
    • Dicarboxylic
    • Diamino
    • Amido
    • Hydroxy
    • Aromatic
    • Sulfur
    • Cyclic
  14. Unsubstituted aminoacids
    • Glycine (can give tighter "twist" to proteins such as collagen)
    • Alanine
    • Valine
    • Leucine
    • Isoleucine
    • impart hydrophobic characteristics to proteins
  15. Dicarboxylic amino acids
    • Aspartic (aspartate)
    • Glutamic (glutamate)
    • Impart negative charges to proteins due to ionization of one carboxylate.
  16. Diamino amino acids
    • Lysine
    • Arginine
    • Histidine
    • Impart positive charges to proteins due to ionization of one amine
  17. Amido amino acids
    • Asparagine
    • Glutamine
    • derived from aspartic and glutamic; hydrophilic character
  18. Hydroxy amino acids
    • Serine
    • Threonine
    • hydroxy groups give them hydrophilic character
  19. Aromatic amino acids
    • Phenylalanine
    • Tyrosine (less hydrophobic due to OH group)
    • Tryptophan
    • impart hydrophobic characteristics to proteins
  20. Sulfur amino acids
    • Cysteine (forms disulfide bonds between polypeptide chains and is hydrophilic
    • Methionine (hydrophobic)
  21. Cyclic amino acids
    • Proline
    • nonaromatic and is found in collagen, elastin, and mucin
  22. What amino acid groups are hydrophilic?
    • dicarboxylic
    • diamino
    • amido
    • hydroxy
    • Cystine in Sulfur group
    • Important in pH control
  23. Which amino acid groups are Hydrophobic?
    • Aromatic
    • Methionine
    • Proline
  24. Specialized properties of amino acids
    • Metal chelation (ex: histidine in hemoglobin)
    • Chain binding (ex: cystene in ribonuclease)
    • Tight helical turns (ex: glycine in collagen)
    • function of protein dependent on number of times each amino acid occurs
  25. Structural Classifications of Proteins
    • alpha-helical domains
    • beta-helical domains
    • alpha/beta domains which consist of "beta-alpha-beta" structural units or motifs that form parallel beta-sheats
    • alpha and beta domains formed by independent alpha helices and mainly antiparallel beta-sheets
    • multi-domain proteins
    • membrane and cell surface proteins and peptides
    • "small" proteins
    • coiled-coil proteins
    • low-resolution protein structures
    • peptides and fragments
    • designed proteins of non-natural sequence
  26. Amino acid classification based on solubility
    • Water soluble (albumin)
    • Lipid soluble (rhodopsin)
    • Insoluble (collagen)
  27. Native form
    protein that possesses its unique biological ability
  28. Denaturation
    Protein that has lost its property
  29. Primary Protein Structure
    normal sequence of amino acids
  30. Secondary Protein Structures (beta)
    • beta-sheets are sequences of primary structure connected by hydrogen bonds (ex: crystallins)
    • beta-turns connect beta-sheets
    • random coils are haphazard forms that connect secondary structures
  31. Secondary Protein Structures (alpha)
    • alpha-hlix (ex: rhodopsin)
    • alpha-helix defined as 1.2-angstrom rise for 100 degree rotation
    • stabilized by hydrogen bonds
  32. Domain
    Structural or functional part of a chain containing secondary structures or a part of tertiary structure
  33. Motif
    a simplified version of domain (contains few parts of domain; ex: helix-turn-helix)
  34. Tertiary Protein structure
    entire shape or configuration of one polypeptide chain constitutes tertiary structure
  35. Quaternary
    two or more polypeptide chains connected
  36. What are crystallins and where are they found?
    Group of proteins found in epithelium and in the fiber cells of ocular lens. Primarily eye protein but found other places as well. They help maintain shape of lens fibers and thus the structure of the lens.
  37. crystallin divisions
    beta and gamma crystallins same family on functional classification.

    • further division:
    • α-crystallins has αA and αB
    • β-crystallins has βH and βL (H = heavy, L = light)
    • γ-crystallins have six subtypes γA to γF
  38. What is the function of α-crystallins?
    • Molecular chaperones- that is help to maintain normal molecular confirmation of other lens crystallins
    • prevents crystallin aggregation- process in formation of senile cataract (age related cataract).

    α-crystallins are the only crystallin in lens epithelium
  39. Which part of the lens is a layer of epithelial cells, has mitochondria, and has high metabolic rates, uses glucose and o2?
    The lens epithelium
  40. The lens epithelium uses glucose and 02, where does it get these primarily?

    A) Blood vessels of ciliary body via lens zonules
    B) Vitreous active transport
    C) Aqueous via diffusion
    D) Unknown to science
    Glucose in aqueous higher than lens hence glucose diffuses readily
  41. Glycolytic enzymes, TCA enzymes and its intermediates and ATP are in high concentration in lens epithelium, why?
  42. What do you know about lens fibers?
    They're the bulk of lens cortex and nucleus, high in number, take up minimal space (why?).
  43. The ocular lens is made up of 65% what and 35% what?
    65% water and 35% organic matter (33% is structural proteins)
  44. Where are the soluble ocular lens proteins located? Where are the insoluble lens protein located?
    • Soluble lens - cortex
    • Insoluble lens - nucleus
    • the nucleus is more dehydrated than the cortex

    the water equilibrium is of prime importance, why?
  45. What is the proper electrolyte balance of the lens?
    High K+

    Low Na+ and Cl- and water

    If sodium moved into the lens that would increase the solutes and the water content will increase (osmotically)
  46. What is the water electrolyte balance of the concentration gradient?

    The electrical gradient?

    And the water electrolyte balance is maintained by what?
    Concentration gradient: Aqueous has more Na+ and low K+

    Electrical gradient: lens is electronegative inside

    Electrolyte balance maintained by the sodium pump
  47. What do you know about the sodium pump?
    operates in the epithelium

    for every 3Na+ removed, 2K+ are allowed

    it requires energy
  48. What effect does the aging process have on the ocular lens?
    • In general increase in phosphorylated chains of α-crystallins in lens fiber
    • Disulfide bond formation (crosslinking)between different crystallins increases
    • Peptide bond disruption in both β and γ crystallins
  49. what do you know about cataract formation?
    • General effect is change in amount of soluble and insoluble lens protein
    • Lens grows with age hence the protein content also increases with age.
    • The process of change of soluble to insoluble is by cross linking
  50. HIgh molecular (HM) weight
    • HM1, HM2, HM3 and HM4
    • HM1 and HM2 soluble kind
    • HM3 and HM4 insoluble and found in cataractous lens
    • HM4 occurs exclusively in nuclear cataract
  51. Senile Cataract Hypothesis
    HM fractions grow into the cell cytoplasm
  52. Radiation of what range has potential for being cataractogenic?

    What absorbs this wavelength and protects the retina from damage?
    range: 300-400 nm

    the lens absorbs these wavelengths
  53. Increased intracellular calcium has what effect on cataracts?

    What about hypocalcemia?
    • increased calcium
    • affects glucose metabolism,
    • inhibition of protein synthesis,
    • induction of HM aggregates
    • Direct loss of transparency
    • Inhibit sodium pump

    • Hypocalcemia
    • related to the dependency of the membrane permeability to levels of calcium
    • Marked electrolyte and water imbalance in low calcium environment
  54. Diabetic and galactosemic
    • Complications of diabetes and glactosemia
    • Conversion of excess glucose or galactose to respective sugar alcohols via sorbitol pathway.
    • Sorbitol cannot readily diffuse out of intracellular compartment.
    • Osmotic gradient favors influx of H2O
    • Sugar alcohols and sugar itself will lead to protein aggregation
  55. Hypoglycemic cataracts
    • Neonates and premature infants at greatest risk
    • Remember ocular lens needs energy
  56. Ionizing radiation and microwave cataract
    • X-ray radiation (some humans as low as 200 rads)
    • Microwave animal experiments shown to cause cataract.
    • Mechanism for microwave cataract is ----?
  57. Effects of Radiation
    • Radiation retinopathy requires 3000-3500 rads
    • 1-2 years after therapy
    • Endothelial cell DNA damage of blood vessels
    • Patients with diabetes grater risk
  58. What is Rhodopsin and where is it found?
    It is a intrinsic membrane protein found in discs and to some extent the plasma membrane or rod outer segment
  59. Rod outer segment
    • Rhodopsin is represented as egg shaped with hook.
    • Rhodopsin more prevalent in discs
    • Rhodopsin has vitamin A
    • Vitamin-A is bound to protein at amino acid lysine #296
    • Vitamin A is present rhodopsin as an aldehyde (retinal) and consists of 11-cis-form
  60. Light absorption properties
    Not a part of visual transduction process per se

    Called bleaching of rhodopsin

    • Alpha peak- 11 cis retinal
    • Beta peak- All trans retinal
    • Gamma peak- opsin
  61. Beer's Law or Beer-Lamberts
    • A=[abc]
    • A= Absorbance
    • a=absorptivity
    • b=light pathlength
    • c= concentration
  62. Photoreceptors
    • Retina: the point of contact between radiated energy, light and nervous system
    • Rod cells:

    Scotopic (dim-light) vision

    Cone cells:

    Photopic (bright-light)



    color vision



    Less sensitive than rods,



    • but they mediate
    • differentiation of colors
  63. Foveal vs Peripheral Cells
    • FOVEA: cone cells have “private line communication”; no divergence
    • PERIPHERY: mostly rod cells greatly outnumber the ganglion cells, convergence is the rule

    High sensitivity, but low acuity
  64. Additive and Subtractive Colors
    Additive Primary Colors

    • Blue (435 nm), green (545 nm), and red (700 nm)
    • Add up to produce white

    Subtractive Primary Colors

    • Yellow, magenta-red, and cyan-blue
    • From the mixing of any 2/3s of the spectrum

    • Subtractive color mixing: the mixing of color pigments or dyes to produce full spectrum of colors
    • Add up to produce black
  65. What are the three pigments?
    • Erythrolabe (red, long)
    • Chlorolabe (green, medium)
    • Cyanolabe (cyan, short)
  66. Trichromatic Vision
    • result of three independent comparisons of rates of photon absorption by the three cone types
    • dynamic output relates only to the rate of photon capture
  67. Anomalies of Color Vision
    • Congenital: inherited, non-progressive nature
    • Acquired: not inherited, secondary to disease (blue-yellow)
  68. Dichromat
    a person missing one of three photopigments
  69. Deuteranope
    person missing chlorolabe (green)
  70. Protonope
    person missing erythrolabe (red)
  71. Tritanope
    person missing cyanolabe (cyan)
  72. Anamolous trichromats
    have photopigment but absorption spectrum of one of the pigments is displaced
  73. Color Vision abnormalities
    • X-chromosome
    • 3-8% in males
    • females less frequent
    • color vision deficiency, can be a problem in certain jobs
  74. X-Chrome contact lenses
    • worn on only one eye
    • reddish brown tint
    • patients may suppress the eye
  75. Glycoprotein
    • proteins to which short chains of sugars are bound
    • Roles of glycoprotein:
    • structural orientation
    • immunological recognition
    • biological lubrication
    • Rhodopsin is a glycoprotein
  76. Mucin layer of tear film
    • made of 55% carbohydrates
    • similar to mucins in the GI tract, nasal mucosa, and trachea
    • secreted by goblet cells of conjunctiva
    • stabilizes tear film by increased viscosity
    • biological lubricant
    • prevent mechanical shock
    • rapid tear film break-up time when amount is low
  77. Pathology that decrease mucins
    • Vitamin A deficiency
    • Ocular pemphigoid (conjunctival ulcerations)
    • Steven-Johnsons syndrome
    • Alkali burns
  78. Vitamin A deficiency related to mucin
    • Xerosis (dryness of conjunctiva in the interpalpebral zone with loss of goblet cells, squamous metaplasia, and keratinization)
    • Bitot spots (triangular patches of foamy keratinizes epithelium in the interpalpebral zone thought to be caused by infection w/ Corynebacterium xerosis)
  79. Alkali burn
    • twice as common as acid burns
    • common alkalis are ammonia, sodium hydroxide, and lime
    • penetrate deeper than burns because acids coagulate surface proteins
  80. Steven-Johnsons Syndrome
    • life-threatening condition affecting the skin in which epidermis separates from the dermis due to cell death
    • caused by infections
    • hypersensitivity reactions to medication
  81. Ocular cicatricial pemphigoid
    • autoimmune mucocutaneous blistering disease
    • keratinization of the caruncle
    • adhesion between the bulbar and palpebral conjunctiva
    • hyperaemia and oedema
    • chronic conjunctivitis
  82. Collagen
    • extracellular, insoluble molecular complex
    • 80-90% of bulk of eye
    • 12 different types in eye
    • protein complex basic unit consists of triple helices (tropocollagens)
    • Roles:
    • supporting members or fibers - maintain tissue, repair tissue
    • scaffolding - platform on which basement membrane is constructed
    • anchoring devices - holds cells onto non cellular area
    • semiliquid gel in eye (vitreous body)
  83. Synthesis of collagen
    disulfide bonds that form at the c-terminal causes the chain to wrap around each other
  84. Tropocollagen
    • units are associated hydrophobically by covalent bonds
    • microfibril: 5 rows of cross-linked tropocollagen
  85. Types of collagen fibers found in Descement's membrane
    • IV
    • VIII
  86. Types of collagen fibers found in Corneal stroma
    • I
    • V
    • VI
  87. Types of collagen fibers found in Cornea
    • II
    • III
  88. Types of collagen fibers found in Sclera
    • I
    • II
  89. Types of collagen found in Vitreous
    II
  90. Types of collagen found in Blood Vessels?
    III
  91. Types of collagen found in Iris?
    III
  92. Types of collagen found in eye lids?
    III
  93. Types of collagen found in lens capsule?
    IV
  94. Type of collagen found in endothelium?
    V
  95. Type of collagen found in Anchoring fibrils of Bowman's membrane?
    VII
  96. What are lamellae?
    Fiber sheets
  97. Ocular structural roles-corneal stroma - what are the percentages of each type?
    • 70% is type I
    • 15% approx type V
    • 15% approx type VI
  98. What is the important role of type v collagen?
    maintain the optical properties of the cornea
  99. what limits the diameter of type 1 collagen?
    Type V collagen oblique running lamellae in stroma
  100. Type VI collagen
    • beaded form
    • stabilizing molecule
  101. the vitreous body
    made of parallel fibers
  102. what is attached at ora serrate and macula?
    the vitreous body
  103. what is the principal vitreous collagen type 2 called?
    vitrosin
  104. vitreous gel is what percentage water?
    99%
  105. what types of collagen hybrids are associated with type 2?
    types IX and V-XI

    type V-XI limits diameter of type II
  106. The collagen found in what membrance is type 4 (including bowman's membrane, lens capsule, and blood vessels)
    basement membrane
  107. What is a basement membrane?
    They are thin structures that occur extracellularly.
  108. What are the functions of a basement membrane?
    support and separation from the other cells
  109. What membrane is the exception to the rule of collagen of basement membrane?
    descement's membrane
  110. descement's membrane is what type and what pattern?
    type VIII and a very geometric pattern
  111. What may affect the synthesis of anchoring fibrils?
    a diabetic state
  112. what types of collagen are in anchoring fibrils?
    type VII and type I (more randomly oriented)
  113. what is characterized by blue sclera and findings of megalocornea and keratoconus?
    osteogenesis imperfecta
  114. what are the factors of osteogenesis associated with type 1 osteogenesis imperfecta?
    • Decreased synthesis of type 1 collagen
    • Clinically – fracture of long bones specially prior to puberty
    • Blue sclera
  115. what are the factors of osteogenesis associated with type 2 osteogenesis imperfecta?
    • Point mutations and rearrangements in triple helical regions
    • Malformed and soft fragile bones and perinatal lethality
  116. type IV of osteogenesis imperfecta is associated with what scleral color?
    almost normal scleral color
  117. how many subtypes of ehlers-danlos syndrome are there?
    nine
  118. what are type 6 and type 4 of ehlers-danlos syndrome known for?
    • type 6 - associated with ocular issues
    • type 4 - rare
  119. what are symptoms of ehlers-danlos syndrome?
    skin is hyperelastic, bruise easily, slow to heal, and joints are hypermobile
  120. what are common ocular features of ehlers-danlos?
    Ocular fragility with increased vulnerability to mild trauma, high myopia, retinal detachment and keratoconus
  121. what are uncommon features of ehlers-danlos?
    Epicanthic folds, microcornea, blue sclera, ectopia lentis and angioid streaks.

    *ectopia lentis displaced lens from its normal position
  122. these are the result of crack-like dehiscences in thickened, calcified and abnormally brittle collagenous and elastic portions of Bruch's membrance
    Android streaks
  123. what are enzymes?
    proteins that have the ability to optimize rates of biochemical reaction

    catalysts
  124. what is activation energy?
    energy required for a reaction to occur
  125. what effect do enzymes have on activation energy?
    they decrease the amount of activation energy required
  126. The reaction is A to B. Which is the substrate and which is the product?
    • A- Substrate
    • B - Product

    Depending on which direction the reaction goes a biochemical substance can be substrate or a product.
  127. an enzyme involved in the principal driving reaction is called ______.
    a rate limiting enzyme
  128. what does principal driving reaction mean?
    a series of enzyme driven reactions, reaction tends to proceed in a given direction regardless of the substrate and product concentration
  129. uncatalyzed reactions are driven by what?
    heat of molecular collision
  130. what kind of reaction has an active site? the enzyme may change but will eventually return to its original state.
    catalyzed reactions
  131. what are kinds of classifications of enzymes are there?
    kinetic basis, michaelis-menten, and allosteric
  132. michaelis-menten enzymes
    kinetic and funcational properties described by michealis and menten in 1913

    example = aldose reductase
  133. change is concentration over time
    • v= {Vmax*[S]}
    • {[S]+Km}

    • Vmax is maximum velocity of enzyme
    • Km is Michealis-Menten constant
  134. michaelis-menten constant formula
    Km=(k2+k3)/k1

    the lower the Km value, the greater the affinity of the substrate
  135. When the Km is NOT greater than the affinity of the enzyme and substrate, what is used to indicate this?
    Kapparent
  136. Allosteric enzymes
    • "other site"
    • kinetics influenced by substrates that bind to enzymes at locations other than active sites
    • quaternary protein structure (more than one polypeptide chain)
    • each chain has its active site
    • few active sites occupied = low affinity of enzyme and substrate
  137. Allosteric enzyme active sites increased in occupation
    • conformational change in the protein
    • increased binding of substrate
    • velocity of enzyme is increased
  138. Allosteric enzymes: second method kinetics influenced:
    • activator substances occupy sites on enzyme away from active sites
    • change in form T to R form
    • Biological way of jumpstart reactions at low concentration of substrate
  139. Competitive enzyme inhibition
    inhibitor replaces or competes with substrate for active site
  140. Non-competitive enzyme inhibition
    inhibitor binds close to active site and prevents reaction despite the binding of the substrate to the active site
  141. Uncompetitive enzyme inhibition
    • two substrates are required for the reaction
    • inhibitor binds close to the active site after the attachment of the first substrate to the site; the inhibitor prevents second substrate from binding
    • Example: aldose reductase
  142. Lysozyme
    • enzyme of tear film
    • destroys gram positive bacteria by breaking glycan of peptidoglycan
    • levels of lysozyme reflect tear film dysfunction
    • aqueous deficiency
    • 1.3 mg of lysozyme found /ml of tears
  143. Lysozyme history
    • described by Alexander Flemming in 1992
    • first located in nasal mucosa
  144. Micrococcus agar diffusion assay
    • tear film on tissue paper
    • dish w/ 5x107 microorganisms
    • 24 hours at 37 degrees C
    • zone of lysis (zone of clearing) is measured and converted to enzyme activity
  145. Sodium-Pottasium ATPase
    • an enzyme located in plasma membrane of cells
    • ocular functions:
    • control of corneal hydration
    • production of aqueous humor
    • good allosteric enzyme example
  146. Endothelium of Cornea
    • single layer of polygonal cells covering posterior surface of the cornea
    • cell density declines with age
    • newborn cell density = more than 5500 cells/ square millimeter
    • adult cell density = 2500-3000 cells/square millimeter
    • minimum cell density = 400-700 cells/mm2
  147. Endothelium metabolism
    • active in transport, synthesis, and secretory functions
    • contain:
    • large nucleus
    • numerous mitochondria
    • prominent endoplasmic reticulum
    • Golgi apparatus
  148. Endothelial Cell-Cell Adhesion: Tight Junctions
    • (macula occludens)
    • function as a barrier
    • do not completely encircle cell like zonula occludens
    • they are a leaky barrier between aqueous and stroma!
  149. Endothelial Cell-Cell Adhesion: Gap Junctions
    • function is intercellular communication
    • mainly in lateral membranes
    • do not contribute to the endothelial barrier
  150. Two factors that contribute to prevent stromal swelling
    • barrier function of endothelium
    • pump function of endothelium
    • Water is maintained at 78%
  151. When endothelium is disrupted, the cornea swells at what rate?
    127 micrometers/hour
  152. When metabolic pump is disrupted, cornea swells at what rate?
    33 micrometers/hour
  153. In cool temperatures, cornea will... ?
    swell
  154. Endothelial Transport NA+ K+ ATPase Pump
    • located in the basolateral membrane
    • about 1.5x106 pump sites/cell
  155. Ouabain (drug) and Digoxin
    • inhibits Na+ K+ ATPase pump
    • stops sodium transport
    • causes corneal swelling
    • prevents temperature reversal
    • eliminates the transendothelial potential difference
  156. Guttata corneas
    • increases pump site density
    • greater capacity for the pump to counteract the leak
  157. Inflamed, Edematous cornea
    decreased pump site density despite increased permeability
  158. Na, K-ATPase pump function
    • Na ions are transported by pump into channels between endothelial cells
    • this creates osmotic pressure and water follows
    • directionality is helped by density of sodium ions in Descemets membrane
  159. Ciliary Process
    • functional unit for production of aqueous humor and its secretion
    • made of capillaries, stroma, and pigmented and non-pigmented epithelia (deep to superficial)
  160. Aqueous Fluid
    • Carefully controlled filtrate of blood
    • produced in ciliary body
    • antioxidant source for the corneal endothelium and the lens
    • carries oxygen
    • helps maintain shape of globe
    • serves as shock absorber
  161. Lactate Dehydrogenase
    • carbohydrate metabolism (aerobic and anaerobic)
    • aerobic is most efficient process
    • anaerobic requires more sugar molecules but produces energy quickly
  162. Lactate dehydrogenase (LDH) subunits
    • H - heart; aerobic
    • M - muscle; anaerobic
    • K - cancer cells, photoreceptor cells; anaerobic
    • all called "isozymes"
  163. Anaerobic sugar metabolism of corneal epithelium
    • closed eye conditions, contact lens wear, or similar unfavorable environments
    • low partial pressure of oxygen
    • can support cells survival with partial pressures of oxygen of 15-20 mmHg
  164. Anaerobic sugar metabolism of crystalline lens
    • energy demand is low
    • lack of blood vessels
    • deep fibers lack subcellular organelles
  165. Anaerobic sugar metabolism of Retina/Photoreceptors
    • energy demand high
    • aerobic tissue (blood supply present)
    • Warburg effect: production of lactate coupled with high consumption of glucose and oxygen
  166. Co-enzyme
    • small organic non-protein molecules that carry chemical groups between enzymes
    • sometimes called "co-substrates"
  167. Vitamin B3 deficiency
    Pellagra (dermatitis, depression, and diarrhea)
  168. Vitamin B2 deficiency
    Skin gland malfunction, dryness/scaling of mouth, photophobia
  169. Vitamin B1 deficiency
    Berberi (muscle loss, gatigue, depression, loss of eye coordination
  170. Vitamin B6 deficiency
    similar to others
  171. Vitamin B12 deficiency
    Pernicious anemia and brain demyelination
  172. Vitamin C deficiency (ascorbic acid)
    Scurvy (incomplete formation of collagen)

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