Urea Cycle Flashcards by Brooke Murphy

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

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Where is nitrogen converted into urea?

in the liver

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PLP (pyridoxal phosphate)

coenzyme, active form of vitamin B6

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urea formation

proteins -> amino acids -> NH2 removed -> forms ammonia, liver converts to urea

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Deamination

the removal of an amino group from an organism, particularly from an amino acid

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during fast what will be broken down to produce energy?

muscle protein

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the break down of muscle protein causes the generation of what?

nitrogenous waste

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urea will be excreted through ….

urine

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healthy adults are in nitrogen balance, which means.

amount of nitrogen taken in = amount of nitrogen excreted (mostly through urea)

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the properly functioning liver has a great capacity for what?

forming urea

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The greater the amount of ammonia produced =

The greater amount of urea converted

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high levels of ammonia indicates a problem with what organ?

The liver

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ammonia =

liver

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urea =

kidney

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urea will be secreted from what organ?

The kidneys

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Reactive Oxygen Species (ROS)

due to oxygen having 2 single electrons in 2 different orbitals, both with the same spin, it is a biradical

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2 electrons with the same spin cannot …..

easily oxidize the bonds in organic compounds because of “spin restriction” - enzyme is required

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ROS are generated

naturally by cellular process

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free radicals

those that can exist independently, can take other electrons from other compounds (usually H’s)

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radicals formed in enzymatic reactions

intermediates that form stable’s products and do not go “free”

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what will ROS initiate?

chain reactions that damage substances within the cell

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Sources of ROS

Mitochondrial electron transport chain produces ATP to run cellular processes, but accidentally forms superoxide
Ionizing radiation (X-rays, radioactive chemicals)

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Cytochrome P450 enzymes

metabolizes drugs, alcohol, and chemical toxins

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job of cytochrome P450 enzymes

oxidize the drugs and other substrates to make them more soluble for excretion

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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