SCO Biochemistry 2

Mechaelis-Menten enzyme

carbohydrates

• oxidative prevention mechanism
• osmotic regulator
• cataract formation in diabetics and patients with galactosemia

aldo-keto reductases

NADPH

sorbitol and galactitol

• osmotic imbalance
• lens cells to swell and burst
• cell debris causes a cataract

100 mM

high glucose levels (20 mM) in the lens of eye

• Quercitin (weak)
• Sorbinil (hypersensitivity)
• Tolrestat (?)
• none are FDA approved

zinc

• involved in the breakdown of extracellular matrix
• break down collagen
• remodel axial length in myopia
• destroy corneal collagen in alkali and other chemical burns
• hydrolyze great variety of extracellular proteins

large amount of overlap in what proteins it can break down

• Rada
• Guggenheim and McBrien

• lenghthening the eye ball
• specifically partially digests scleral protein so new proteins can be formed

• synthetic inhibitor of mettaloproteinase (SIMP)
• tissue inhibitor of mettaloproteinase (TIMP)

prevention of glaucoma or other degenerative diseases

• hydrophobicity
• hydrophilicity

• fatty acids
• triacylglycerols
• phospholipids
• isoprenoids
• esters
• eicosanoids
• glycolipids

• 3-30 carbon chain (varies)
• hydrocarbons with carboxylic acid group at one end (hydrophilic)

• chain length
• degree of unsaturation

• hydrophobic
• higher melting point

• low melting point
• more fluid

• first # = number of carbons
• # after colon = number of double bonds
• #in parentheses = carbon number closest to carboxylic acid group (COOH) with double bond

• Myristic acid (saturated, sweet smelling)
• Cervonic acid (found in membranes of retinal photoreceptors)

• increasing carbon length raises melting point and thickens membrane
• increasing double bonds lowers melting point and increases fluidity

• a glycerol and 3 fatty acids esterified together
• liquid form

lipids can be broken down to form acetyl CoA

triacylglycerols

No. It only holds a limited amount for maintaining cellular membranes

• similar to triacylglycerols
• (glycerol is frame)

phospholipids

• if you don't know what this does, you don't belong in optometry school... but here is a reminder...
• fatty acids face each other
• lipids face aqueous

a variation of phospholipids found in the mitochondrial membranes

• RBCs need to be more rigid than ROS membranes
• there is 6x more cervonic acid in ROS membranes than RBC

• lipid made from isoprenes (5-carbon unit)
• cholesterol and allied steroids (cortisol)
• vitamin A
• coenzyme Q
• essential oils in plants

• source of cholesteryl esters
• precursor to steroid hormones

precorneal tear film

rigidity

8%

• Nothing
• if found, it confirms ocular disease

• granulatmatous inflammation of eyelid margin
• not caused by meibomian glands but is from membranes of neutrophils, lymphocytes, and other WBCs

rich in cholesterol, not cholesteryl esters

• esters of long-chained fatty acids and long-chained alcohols
• solid at room temperature

• Eye: lipid layer of the precorneal tear film
• leaves
• beeswax
• skin
• hair
• wool
• fur

membranes of nervous, ocular, and other tissues

• lipids containing carbohydrates
• ex. galactose, N-acetylgalactose, and N-acetylneuraminic acid

• barrier of cell surface and interior cell structures
• hydrophobic

• lipids
• carbohydrates
• proteins
• phospholipids (make associations more complex)

• a congregation of lipids forming a spherical structure
• hydrocarbons will face towards each other

• phospholipids
• cholesterol
• glycolipids
• polar group extends toward aqueous
• nonpolar group associate together hydrophobically

• part of overall bilayer structure
• contribute short-chain carbohydrates into the outer aqueous volume
• form cellular glycocalyx

• complex lipids with short sugar arms
• plasma membrane

the "wall"

• the "doors," 2 types
• intrinsic (integral)
• extrinsic (peripheral)

• cross the membrane bilayer
• transport (glucose)
• receive (insulin)
• transduction (light)
• attachment (basement membranes)
• Ocular example: rhodopsin

• only on one side of membrane
• structural (cytoskeleton maintenance)
• anchoring (glycocalyx components)
• transduction, signaling, local movement (myosin and actin components)
• Ocular example: transducin

convert light signals into chemical signals

• smallest percentage of membrane constituents
• mostly found of extracellular surface
• form the glycocalyx
• types: glycolipids and glycoproteins

• immunological identifiers
• biological bridges/ bonding agents (ex. epithelial corneal cells to Bowman's membrane

• simple diffusion
• passive facilitated diffusion
• active facilitated diffusion

• used by small molecules, oxygen, nitrogen, pharmacological drugs
• travel from high to low concentration
• substance must be partly lipid soluble (bilipid membrane not a barrier)

• protein acts as a channel to move substance across membran
• travel high to low concentration
• can move faster than diffusion
• water transported this way through aquaporins
• glucose uses protein GLUT-1

• proteins act as mechanism to move substances
• uses energy (pumps)
• travel from low to high concentration
• Na+, K+ ATPase pump is good example

• uniport (single substance transported)
• cotransport (2 substances transported simultaneously), 2 types
• symport (same direction)
• antiport (opposite direction)

• lipid layer (most anterior)
• aqueous layer (central)
• mucus layer (most posterior)

• waxes
• cholesteryl esters

dissolved salts and proteins

mucoid proteins

• flow from ducts to eyelid edges
• form a film over the aqueous layer
• adhere to the eyelid skin
• barrier to aqueous layer
• form water-tight seal when lids are closed

• excessive production of keratin in ductal epithelium
• epithelial cells detach from gland and block flow
• bacteria infection may result

• transduction mechanism of converting light energy into electrical signaling
• sending signals to the brain

• gives fluidity to cell membranes
• decreases viscosity in membrane discs
• helps with rotational and lateral movements of rhodopsin

• similar to nervous tissue
• has less sphingomyelin and phosphotidyl inositol compared to nervous tissue

15%, most cells have only 1%

oxidative processes in retina

• vitamin E
• it is lipid soluble
• absorbs free radicals which attack double bonds of membrane fatty acids

hexaminodase A deficiency

• cherry red spot on retina
• blindness occurs early
• death at 3-6 years of age

• isoprenoid
• fat-soluble

• retinyl ester
• retinol
• retinal
• retinoic acid

• beta carotene (yellow vegetables -- carrots and sweet potatoes)
• retinyl esters (animal sources)

• beta carotene or retinyl esters are converted into retinol
• chylomicra transports retinol to liver or cell for storage
• retinol changed to retinyl ester for storage
• retinol binds to retinol binding protein (RBP) in cell or prealbumin in bloodstream
• retinal binds to opsin to form rhodopsin or retinoic acid makes glycoproteins in corneal epithelium

• Nyctalopia (loss of night vision)
• Xerophthalmia (dry eyes, hardening of conjunctiva)
• Keratomalacia (degeneration of cornea)

• adverse affects to any epithelial cells
• inhibition of bone elongation

• abdominal pain
• blurred vision
• drowsiness
• headache
• irritability
• nausea
• vomiting

• increased gluconeogenesis
• protein turnover

• children 400 RE
• males 1000 RE
• females 800 RE
• nursing females 1200 RE

3.33 to 1

energy can be neither created nor destroyed but can be transferred in or out of a system

4 kcal/gram

9.3 kcal/gram

4.0 kcal/gram

7.0 to 7.2 kcal/gram

O₂ + some energy molecule yields CO₂ + H₂O

it is the ratio of CO₂ produced compared to amount of O₂ used.

• carbohydrates 1.0
• proteins 0.8
• fats 0.7

glucose

• glucose
• galactose
• mannose
• fructose

• maltose
• sucrose
• lactose

• 6 membered ring
• glucose
• galactose
• mannose

• 5 membered ring
• fructose

• Aldehyde (least common)
• alpha
• beta (most common)

• 2 alpha glucose molecules
• linked at 1-4

• 1 alpha glucose and alpha 1 fructose
• linked at 1-2

• 1 beta galactose and 1 beta glucose
• linked at 1-4

• the mouth (buccal cavity)
• saliva has alpha-Amylase

• active at 6.5 to 7 pH
• denatured in stomach
• helps keep teeth clean
• digests monosaccharides or starch

it can destroy salivary glands

• attacks peptidoglycan of bacterial cell wall
• attacks gram positive bacteria only
• normal flora is resistant to it
• animals use saliva as antiseptic

stomach

• pH close to 2.0
• kills most microorganisms
• denatures proteins
• required for action of Pepsin (which works at a low pH)

the small intestine creates more digestive enzymes with the same function as gastric juice and pepsin

the pancreas

• break down of large droplets into small ones
• this is done by combination of pancreatic lipase and colipase

• fatty acids
• 2-monoacylglycerol
• cholesterol
• fat soluble vitamins (A, D, E, & K)

• fats and lipids 95%
• starch and carbohydrates 70%
• proteins variable
• plant polymers not digested

they can digest the cells that secrete them

• biosynthetic process to synthesize macromolecules
• requires energy

• degradative process
• nutrients oxidized to supply energy for cellular activity

a chemical reaction pathway is shut off when enough of end product is produced

• positive feedback loop
• a product stimulates more of a chemical reaction pathway

• storage form of glucose
• glucose cannot be stored in cells

• liver
• muscle tissue
• eye

• 4 to 5.5 mmol/liter
• same as 70-100 mg/dL

• corneal epithelium
• retinal Muller cells

2 molecules of pyruvate per glucose molecule

• formation of acetyl CoA
• TCA
• oxidative phosphorylation

pyruvate + NADH + H + lactate dyhydrogenase = lactate + NAD⁺

2 ATP per glucose molecule

• ocular tissue
• muscle tissue

• mature red blood cells (RBCs)
• skeletal muscle during vigorous exercise
• ischemic tissue cut off from blood supply (like corneal epithelium)

• 80% of glycogen used up in 8 hours of wear
• results in corneal edema (increase in corneal thickness)

pyruvate dehydrogenase complex

catalyze formation of Acetyl CoA

• 3 NADH
• 2 CO₂
• 1 FADH₂
• 1 GTP

• 4
• 5
• 6
• 7
• 9

• Complex I receives NADH for electrons
• Complex II receives FADH₂ for electrons
• Q shuttles e- from complex I or II to complex III
• C shuttles e- from complex III to complex IV
• O₂ and H+ form water
• Complex V takes H+ and ADP to form ATP

36-38 ATP per glucose molecule