Urea Cycle Flashcards
Transamination
process for removing nitrogen from amino acids, tissues can use the carbon skeleton of the aa as fuel and transport the nitrogen to the liver for conversion into urea
Where is nitrogen converted into urea?
in the liver
PLP (pyridoxal phosphate)
coenzyme, active form of vitamin B6
urea formation
proteins -> amino acids -> NH2 removed -> forms ammonia, liver converts to urea
Deamination
the removal of an amino group from an organism, particularly from an amino acid
during fast what will be broken down to produce energy?
muscle protein
the break down of muscle protein causes the generation of what?
nitrogenous waste
urea will be excreted through ….
urine
healthy adults are in nitrogen balance, which means.
amount of nitrogen taken in = amount of nitrogen excreted (mostly through urea)
the properly functioning liver has a great capacity for what?
forming urea
The greater the amount of ammonia produced =
The greater amount of urea converted
high levels of ammonia indicates a problem with what organ?
The liver
ammonia =
liver
urea =
kidney
urea will be secreted from what organ?
The kidneys
Reactive Oxygen Species (ROS)
due to oxygen having 2 single electrons in 2 different orbitals, both with the same spin, it is a biradical
2 electrons with the same spin cannot …..
easily oxidize the bonds in organic compounds because of “spin restriction” - enzyme is required
ROS are generated
naturally by cellular process
free radicals
those that can exist independently, can take other electrons from other compounds (usually H’s)
radicals formed in enzymatic reactions
intermediates that form stable’s products and do not go “free”
what will ROS initiate?
chain reactions that damage substances within the cell
Sources of ROS
- Mitochondrial electron transport chain produces ATP to run cellular processes, but accidentally forms superoxide
- Ionizing radiation (X-rays, radioactive chemicals)
Cytochrome P450 enzymes
metabolizes drugs, alcohol, and chemical toxins
job of cytochrome P450 enzymes
oxidize the drugs and other substrates to make them more soluble for excretion
Radical intermediates of Cytochrome P450 can
escape and become free radicals, causing cell damage
What damage can be caused by ROS
- Protein damage
- Mitochondrial damage
- Membrane damage
- DNA damage
- Cell swelling
- Increased Permeability
- Massive influx of CA2+
- Lipid Per-oxidation
- Respiratory
DNA damage due to ROS
strand breaks or 1/20 different alterations that can lead to mutations
Is there anything that can help repair the DNA damage done by the ROS?
If the DNA repair systems can fix the alterations than yes, if missed mutations will accumulate
Endogenous sources of ROS
Inside the body (O2, H2O2, OH, NO, O2)
Reactive Nitrogen-Oxygen Species (RNOS)
free radicals that cause damage to cellular components: DNA, cell membranes, enzymes, electron-transport chain
RNOS compounds come from where?
Produced in the cell or can be from outside sources that will damage our cells
Inflammation free radicals
destroy invading pathogen or clean up dead cells in damaged tissues, activated neutrophils
Respiratory burst (oxidative burst)
occurs in activated neutrophils, consumes oxygen to create reactive substances that will kill phagocytosed bacteria
Is inflammation helpful or harmful?
either. can lead to collateral damage to the surrounding tissues
Cellular defences put in place to do what?
fights the effects of free radicals
oxidative stress
a condition in which the production of oxidants and free radicals exceeds the body’s ability to handle them and prevent damage
endogenous antioxidants (ex. superoxide dismutases (SOD)) and catalase
have different isoforms that exist in different parts of the cells
glutatione peroxidase
function to remove peroxiding formed outside of peroxisomes
metals found in nutrients in the diet
Cu, Zn, Mn, Fe, Se
Fat soluble Vit E and Waters soluble Vit C are involved in
neutralizing free radicals
Vit E
donate an electron to radicals
Vit C
donate an electron to Vit E to regenerate its antioxidant capacity
Aged-related macular degeneration (AMD) is
A disease that blurs central vision, oxidative damage thought to be responsible for advancing the disease
Where does the urea cycle exclusively take place?
in the liver
When does nitrogen occur?
at physiological pH in the form of NH4 and ammonium in the blood
Is urea toxic to the body? what happens to it?
No it is sent to the kidney and excreted from there
What happens to the protein that is broken down and not used for protein synthesis?
deaminated
TOO much protein means
- cannot store protein
- always functional
- we turn it into glucose or fat to store
When we have more protein what happens?
- turns into glucose
- restores glycogen and the rest is stored as fat packed in VLDL
What must nitrogen be converted into to be excreted in the urine and where?
turned into urea in the liver
How can essential amino acids be made?
transamination
What is PLP involved in?
amino acid metabolism
Great amount of ammonia produced means
greater amount converted to urea
When we create nitrogen through deamination what else occurs?w
we create ammonia which is toxic to CNS
What happens to the ammonia created from deamination?
the liver will take it to create urea and send it to kidney to be excreted
Elevated ammonia means
liver problem; chronic alcohol abuse, enzymes, hepatitis
Elevated urea means
made it through the urea cycle; kidneys might be at risk
Where do most of the steps in converting urea locate?
cytosol
What is the most common X linked issue within the urea cycle?
orithine transcarbamoylase
What causes alot of chronic diseases? and what are they?
reactive oxygen species
- cancer, respiratory problems, heart disease
How are ROS generated?
by natural processes; unfortunate
Source of ROS
the mitochondrial electron transport chain produces ATP to run cellular processes but accidentally forms superoxide
What is an effective way to prevent DNA mutation when ROS occur?
base excision repair system
What are RNOS
Exogenous forms of ROS
Where do RNOS occur from?
those who smoke, poor diet etc
RNOS damage can go to cellular components such as
DNA, cell membrane, enzymes, the ETC etc
Endogenous
within our body
Exogenous and antioxidant
taken into our body
What can help reduce ROS?
vegetables and fruits
Superoxidase dismutase is what
an enzyme in a number of different forms within a number of different cells
When there is more LDL and no antioxidants to neutralize them what occurs?
atherosclerosis
What vitamins are involved in neutralizing free radicals?
Vitamin E and C
What does vitamin E do?
donate electron to free radicals
Vitamin C can?
donate electron to vitamin E to regenerate its antioxidant capacity
Carotenoids
derived from the diet and are antioxidant as well
