BHS 150.1 – Biochemistry I
Notetaker: Elisabeth Anderson
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Date: 10/15/2012, 1st hour
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Clicker Questions
o The process of B Oxidation of one mole of palmitic acid (C16) produces:
 7 moles each of FADH2 and NADH and 8 moles of acetyl CoA.
o So ________ moles of ATP’s are used and made during beta oxidation only while __________ are
made from total oxidation of C16? (palmitate)
 2used, 35 made, total of 131 made
Oxygen Metabolism and Toxicity
o Oxygen Metabolism
 Looking at free radicals
 This is important because free radicals steal electrons, which damages things
 Damaging DNA, protein, membrane
 Damaging viability of cell and creates inability for cell to do what it needs to do
 Need system to fix the damage that is occurring
 There are a whole host of diseases with free radical buildup that has ocular effects
 Diabetes
 Macular Degeneration
o Metabolic mismatch
o Free radicals produced but not enough antioxidants to protect against it
 Cataracts
o Damaged proteins
 Not fully linked to free radicals, but with advanced aging there is more damage
from free radicals and also higher occurrences of these diseases
 Tested in mice
o Older mice treated with antioxidants
 These mice performed better
 Sunlight is most common oxidizing agent
 Iron is an oxidizing agent
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Free radicals are inevitable with aging
 These diseases are becoming more prevalent because of increased life spans
 As we age antioxidants run out
o Free radical: An unpaired electron
 Oxygen will steal electrons to create unpaired electrons
 Stable but fairly reactive
 Slowly over time will take electrons for itself
 Reduction: Gaining an electron
 Oxidation: Losing an electron
 Antioxidant: donates electrons to prevent uncontrolled oxidation from occurring
 Willingly providing the thing that free radicals want, so no damage is occurring
 Electron Transport Chain
 All transfers are occurring in controlled membrane bound environment
 Controls reactivity and damage that can be occurring
 We have the ability to make this energy and release antioxidants
 Has to be controlled
 Oxygen creates reactive oxygen species (ROS’s)
o Oxygen is causing the problems
o Cardiac Reperfusion
o Reperfusion injury
 Occurs in brain and heart
 From massive influx of oxygen after deprivation
 Free radicals are created from deprivation state, then reactions
occur out of control when the oxygen comes back in
o First ROS is superoxide anion
 Very reactive
 Not lipophilic, does not move around much
 Steals electron right away from something near it
BHS 150.1 – Biochemistry I
Notetaker: Elisabeth Anderson
Date: 10/15/2012, 1st hour
Page2
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Converted into hydrogen peroxide
 Can be very dangerous
 Not a free radical
 Lipophilic, can move easily into membranes and
through membranes
o Steals electrons from other places
o Spread of damage
 Steals another electrons and turns into hydroxyl free
radical
o Very reactive
o Most potent ROS
 Lipophilic
 In the membrane
 Steals electrons very effectively
o Turns into water and becomes stable
Same reaction that occurs during ETC but is in uncontrolled
environment and becomes dangerous
Damage to DNA
 Fragment DNA
o Usually a sign of damage to the cell and initiates destruction of cell
o Dangerous to the cell
 Cross link DNA
o Cells have trouble replicating, dividing, making proteins
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can cause uncontrollable growth that leads to cancer
Damage to Proteins
 Cells that rely on proteins will not be able to function properly
o Decreased energy
o Other problems
o Mitochondrial damage
 Membrane damage (lipid peroxidation)
o Lipid peroxidation leads to membrane damage
 Lipids start to have their electrons taken
 Leads to membrane damage
 Influence mitochondrial damage (in the membrane)
 Decreased energy production
o Decreased ability to make ATP
 Increased permeability
 Ions will move in, water will follow, cell will swell
and burst
 Cell is no longer viable
 Results of damage are dependent on the function of the cell
 Damaged proteins affect the lens to create cataracts
 Damaged membrane affects the retina because it is
energy dependent
 Damage can be stimulated by sunlight, air pollution, toxins in cigarette smoke
 Occurring in our body all the time
 Enzymes in body that are designed to break down toxic substances can lead to problems
Lipid peroxidation
 Hydroxyl free radicals in the membrane steal electrons from lipid
 Make lipid radical
o Missing an electron
o Unpaired electron that wants to steal an electron from something else
o Steals electron from neighboring fatty acid in the membrane
o It is now complete but next fatty acid is now a radical
BHS 150.1 – Biochemistry I
Notetaker: Elisabeth Anderson
Date: 10/15/2012, 1st hour
Page3
 End up with damaged lipid radical
Oxygen binds to lipid radical
 Creates lipid peroxy radical
 Damaged lipid radical
 Steal from next fatty acid
 Changes next fatty acid into lipid radical
 Makes lipid peroxide
 Starting to get a spread of damage on the membrane
Decreased oxygen leads to limited cell death
o Isolated free radical production
o Isolated damage
Influx of oxygen
o Stimulates the oxygen free radical formation
o Spreads the damage
o Need drugs to prevent massive reperfusion of oxygen to prevent the
radicals and cell injury
o Iintroduce free radical scavengers to prevent free radicals from forming
during stroke
 Drug “Lazarus” designed for people that are having a stroke
 Reduce spread of free radicals and damage
 Free radical scavengers = antioxidants
 Provide electrons
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Protection from Oxidation
 Cell’s best way to protect against free radical damage is compartmentalization
 Put enzymes that produce free radicals into membranes
 Compartmentalize mitochondria in membranes to keep the damage from getting
out of control
 Repair mechanism
 Try to repair anything that it can and make more of it
 Proteins will be degraded and made more
 Will fix membranes and DNA
 Nutrients
 Have to intake vitamins in order for them to be effective
 Vitamin E is only true antioxidant that we take as a vitamin
 Beta carotenes
 Vitamin C is for water environment
o Water soluble
o Won’t work well for lipid peroxidation
o Very good for recycling Vitamin E
 Series of enzymes
o Antioxidant enzymes
 Catalase
 Superoxide dismutase
 Glutathione Peroxidase System
 Vitamin E
 Excellent antioxidant for lipid peroxidation
 Will donate an electron to lipid radical or lipid peroxy radical
o Lipid is recovered
o Prevent stealing electron from another lipid so spread of damage is
stopped
o Can get into the membrane and donate electron where damage is
occurring
o Still is a damaged lipid that needs repair but not as severe as it was
BHS 150.1 – Biochemistry I
Notetaker: Elisabeth Anderson
Date: 10/15/2012, 1st hour
Page4
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Helps to convert lipid peroxy radical as well
 Donate electron from ring structure
 Resonance from multiple bonds around the ring
o Electrons can more easily be shared
o Ring structure allows stabilization
 Binds up lipid peroxy
 Stops lipid peroxy from stealing electron from anything else
 Changes lipid peroxy to lipid peroxide
 Donates two electrons to fix lipids
 Once the ring structure is broken the Vitamin E needs to take
on a structural change
 Needs to be shipped out for a new use after two
electrons are used
 Vitamin C (Ascorbic Acid)
 Has a ring structure with one double bond
 Not just an antioxidant
o Can react with Vitamin E that has lost one electron to regenerate it
o Can act as an antioxidant in a water soluble environment
o Loses an electron from OH group
o Uses ring resonance to share loss of electrons temporarily
o Can lose second electron and have altered structure
 Now a more stable structure
o Can be regenerated with addition of two more electrons
 Carotenoids
 Lipophilic, can donate electrons
 Can bind the lipid peroxy radical
o Share with ring resonance
o Can share on both ends
o Stop spread of lipid peroxy radical
Antioxidant/ Scavenging Enzymes
 Series of enzymes found in cells
 Mutations in these enzymes leads to diseases
Superoxide dismutase
 Controlled environment to get electrons from copper
 Instead of stealing electrons from proteins or DNA, electrons are being donated from the
copper
 Degenerative diseases are caused by mutations of superoxide dismutase
 Damage of them leads to massive production of free radicals
 Become demyelinating disease
 Lou Gehrig’s disease
 Mitochondrial, free radicals are escaping
 Damaged to the point where they are not as functional
o Can work ok under low oxidative stimuli
 Takes super oxide anion
 Donates electrons
 Get a safe conversion to peroxide
 Peroxide in the presence of iron quickly converts to hydroxy free radical
o So we have to have other enzymes to work with peroxide
Catalase
 Works under controlled environment
 Uses multiple hydrogen peroxides,
 Uses electrons, reconfigures
 Produces water and oxygen
 Stops formation of free radicals
 Controlled conversion of peroxide to water and oxygen
BHS 150.1 – Biochemistry I
Notetaker: Elisabeth Anderson
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Date: 10/15/2012, 1st hour
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Glutathione peroxidase
 Works with peroxide and damaged proteins
Glutathione
 Tripeptide
 Cysteine residue is important component
 Can form disulfide bonds
 Can donate electrons in a controlled environment
o Get two glutathiones
o GSSG (Oxidized Glutathione)
 Donated two electrons
 Can measure glutathione and oxidized and reduced glutathione in blood and
tissue
o Can see what the oxidative status is
 Glutathione peroxidase
o Takes electron from cysteine and gives to peroxide to form disulfide
bond
 To recycle disulfide form of the glutathione peroxidase
 Need glutathione reductase and NADPH
o Get NADPH from pentose phosphate pathway
o In order to keep glutathione system active
o Electrons come from NADPH
o Add to cysteine residue
o Ready to go again
 Efficient in working in lipid environments
 Prevent spread of lipid peroxidation
Oxidative stress
 Too many oxidizing agents and not enough antioxidants
 Need balance
 More efficient and balanced in young people
 Eyes are particularly vulnerable
o Absorb light, directly exposed to light
o Mechanisms to influence light coming in
 RPE has melanin to absorb excess light
 Iris can absorb light coming in
 Pupil size (constriction) can reduce amount of light coming in
o Polyunsaturated lipids are most susceptible to lipid peroxidation
 Highest amount of polyunsaturated fatty acids in the eye
 Cornea is out in the environment
 Opportunity to get lots of damage
o Retina is vulnerable
 Potential for lots of lipid peroxidation
 Light coming in
 High oxygen
 High energy requirement
 Theory behind macular degeneration
 Metabolical mismatch
 More in caucasions
o Less melanin to absorb light
 Less antioxidants with age enzymes aren’t as
functional
 More free radicals produced than antioxidants
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Areas of concern in the cornea
o Collagen
 Oxygen can penetrate from environment
BHS 150.1 – Biochemistry I
Notetaker: Elisabeth Anderson
Date: 10/15/2012, 1st hour
Page6
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Sunlight coming through
Damage to collagen alters regular spacing and reduces clarity
 Opacities develop
Damage to endothelial cells
 Damage to proteins or membranes will cause excess
water to come in
Clicker Question
o The best antioxidants to prevent lipid peroxidation are:
 β-carotene
 Vitamin E