Nutrition-exam 2- Metabolism Flashcards
Catabolism
Break down (releases energy)
Metabolism
Chemical reactions necessary to maintain life
Anabolism
Synthesis (requires energy)
Coenzyme
Help enzymes work
Ex: NAD “nicotinamide” (niacin B3) and FAD”flavin adenine dinucleotide” (riboflavin B2)
Glycolysis
⋅ occurs in the cytoplasm
⋅ anaerobic - doesn’t require O2
Energy investment steps:
2 ATP and a glucose molecule, each ATP loses a phosphate turns into ADP ( from tri- to di-) then it is able to divide and you get two G3P
Energy harvesting steps:
Some stuff happens and 4 ATPs are produced, making the net gain 2 ATP
And the final product of 2 pyruvates
Krebs cycle
⋅occurs in the mitochondria
⋅aerobic - in presence of oxygen
After glycolysis: The 2 pyruvates bind with coenzyme A by releasing one carbon each to produce two carbon dioxides. You now have 2 Acetyl Co A which goes into the Krebs cycle
2 Acetyl CoA bind with oxaloacetate producing citric acid ( 6 carbon). Coenzyme NAD and FAD turn into NADH and FADH
Electron transport chain
⋅occurs in the mitochondria
⋅ requires oxygen
H+, Electron, NADH, FADH are continuously transported in and out of the cell membrane to pump hydrogen ions across the membrane. Oxygen (the last acceptor in the ETC) accepts the electrons with hydrogens to form H2O
What happens when oxygen us not present or there is not enough to go through the Krebs cycle?
Lactic acid (for humans) or alcohol fermentation takes place
What is the effect of lactic acid formation?
Muscle pain and fatigue
Cori cycle
Removes lactic acid fermentation accumulation from muscles. Lactic acid is recycled by the liver and turned back into glucose
Which carbon chain can the body convert back into glucose?
3 carbon components
What will happen to 2 carbon components?
2carbon components will either go into the Krebs cycle or Fatty Acid synthesis if the body doesn’t need energy.
What happens to fatty acids after absorption?(fat metabolism)
Beta oxidation - the breakdown of fatty acids into 2 carbon fragments
Remrber: fatty acids are long chains of carbon with a glycerol (3 carbon) backbone
Keeps breaking off 2 carbons at a time. The 2 carbon fragments then go into the Krebs cycle. The glycerol backbone is the only part that can be turned into glucose.
Why is high fat /low carb diet bad for you?
Fat metabolism is very inefficient because the only part that can be turned into glucose is the glycerol backbone. Glucose is needed for brain and nervous system. Carbs give you much more glucose
Amino acid metabolism
Deamination
⋅ removal of amine group
⋅formation of keto acid and ammonia
Transamination
⋅transfer of the amino group from an amino acid to a keto acid
⋅which is important for synthesis of non essential amino acid
No oxaloacetate means
acetyl CoA can’t bind with anything, Krebs cycle slows down
Ketones
Ketones are produced under severe carbohydrate deficiency b/c glucose is needed for the brain
If oxaloacetate is converted to glucose and breaking down of proteins and fats are not sufficient for glucose levels then ketosis occurs.
The production of Ketones suppress the appetite, metabolism slows down, blood pH decreases and blood thickens
Alcohol
Ethanol : CH3CH2OH
Alcohol is hydrophobic… It dissolves phospholipids in cell membrane and also disrupts proteins killing cell organelles
What is alcohol proof?
Half the number is the percentage
200 proof = 100% ethanol
190 proof= 95% ethanol
Alcohol metabolism
⋅Approximately 20% of absorption occurs in the stomach w/ alcohol dehydrogenase
⋅the rest gets absorbed in the intestines by “priority treatment” b/c body knows it is toxic
Alcohol metabolism and the Liver
Once alcohol is absorbed it goes to the hepatic portal vein to the liver. The liver focuses on alcohol so other processes won’t occur. This results in accumulation of fatty acids
The liver is the only organ that can produce the enzymes needed to metabolize alcohol at a quick enough to keep up
Oxidation of alcohol creates….
A considerable decrease in NAD
(NAD us focused in the liver and cannot go anywhere else)And decreases metabolic processes
NADH Accumulates so the Krebs cycle stops and acetyl CoA goes to fatty acid synthesis which is why alcohol abuse is associated with fatty liver
What is associated with vitamin B6 deficiency
Acetyl dehydration - leashes vitamin B6 from the muscle
Fibrosis
Formation of scar tissue on the liver
Reversible (liver can regenerate itself if the drinking stops and liver is allowed time to heal)
