Biochemistry Flashcards
What is lipogenesis?
The formation of FAs from glucose sources (the opposite cannot happen)
Name the major sites for lipogenesis
Lipogenesis happens in a lot of cells (liver, kidneys, mammary glands, brain and adipose tissue) - only converted into triglycerides in liver and adipose tissue
What are the actions of insulin and glucagon on lipogenesis?
Insulin = increases lipogenesis Glucagon = inhibits lipogenesis
In normal physiology what is starch broken down into?
Acteyl-CoA
What is the function of citrate in lipogenesis?
To transport acteyl groups into cytoplasm
Explain the function of ACP
ACP is an acyl-carrier protein which binds to a starter chain to begin a FA
State and explain the 4 steps of FA synthesis
Condensation (release H20)
Reduction (gain e - more stable)
Dehydration (release H20)
Reduction and release
Which molecules acts as an electron donor in lipogenesis?
NADPH
What 2 molecules are used to carry C atoms in lipogenesis?
Malonyl-CoA
Acetyl-CoA
What 2 molecules are joined together to form triglycerides?
G-3-P (glycerol-3-phosphate)
+ 3x FAs
What other similar products are produced in the liver?
Cholesterol
Phospholipids
Lipoproteins
What are the 2 parts of glycogen?
Glycogenin and multiple glucose molecules
Name the bonds found in glycogen molecules
alpha 1-4 glycosidic - straight
alpha 1-6 glycosidic = branches
Where in the body are the largest quantitites of glycogen found?
Liver - to maintain blood sugars
Muscle - provide energy during exercise
What is the name of the basic process that produces glycogen from a starter molecule and monomer units?
Glyogenesis
UDP-glucose serves what role in producing glycogen?
Acts as an activated form of glucose that gets attached to glycogen chains
Glycogen synthase and transglycosylase differ largely in 1 way; what is it?
Glycogen synthase attaches straight chains
Transglycosylase attaches branches
What is the rate limiting enzyme of glycogen production?
Hexokinase
Gluconeogenesis can produce glucose from what 3 major classes of molecule?
Amino acids
Lactate
Glycerol
What is the cori cycle?
The reverse of anaerobic respiration
Turns lactate -> glucose
Where does the cori cycle take place?
Liver mitochondria
What is the “energy cost” of the cori cycle?
Cori cycle requires more energy than anaerobic respiration releases - not energy efficent
What is the name of the process that breaks glycogen to monomer subunits?
Glycolysis
What 2 fates befall the monomer subunits of glycogen break down?
Muscles -Further glycolysis
Liver - Converted into glucose
What transport molecule is involved in the fate of monomers in the liver?
GLUT2
What are the 3 types of lipid, and how do they differ?
Simple
Compound
Steroids
Increasingly complex with added groups
What are lipids soluble in?
Non-polar compounds
like dissolve like
What are the 2 components in triglycerides?
Glycerol (G-3-P) and 3 FAs
Where are triglycerides the major energy storage?
Adipose tissue
Where is acyl CoA transported into?
Cytoplasm
Draw the mechanism of acyl CoA transport
Sketch of carnitine shuffle
How is acyl carnitine formed?
acyl-CoA
+
carnitine
List the products of B-oxidation per cycle
FADH Acetyl-CoA Acyl-CoA NADH + H (FAAN)
PLUS
1x acetyl-CoA
A 14C fatty acid would produce what after B-oxidation
C/2 - 1 = 7 - 1 = 6 6x FADH 7x Acteyl-CoA 6x Acyl-CoA 6x NADH + H
Where does B-oxidation occur?
Mitochondria
Are ketones physiologically present?
Yes - in small amounts
Which states are ketones dangerous?
Starvation and diabetes - oxcalatone is used up in gluconeogenesis so can’t break down acteyl-CoA
How do ketones cause damage?
They are slightly acidic so when in high amounts causes metabolic acidosis -> organ damage
Which body locations are ketones used ?
Kidneys and heart
What atom/molecule do AA contain that mean they need to be excreted?
Nitrogen
The dangerous components of AA are excreted as which molecules? Which is most common?
Urea, uric acid, creatinine, NH4 (ammonium)
Urea = most common
What enzymes act on proteins to form AA?
Proteolytic
Where are AA absorbed?
Intestinal cells - small bowel
What is transanimation?
Moving amino group from AA to alpha keto acid
Where does transanimation occur?
In all body cells
What 2 molecules are used to transport molecule products of transanimation to the liver?
Glutamine and alanine
gluty alan
What is deanimation?
Conversion of amino groups to free ammonium ions in liver
Where is urea synthesised?
Mitochondrial matrix
What is the purpose of synthesising urea? (not to get rid of urea)
Less soluble than other forms of nitrogen compunds so less water is needed to be excreted alongside urea
What is the fate of carbon skeletons left after AA metabolism?
Converted to glucose
Oxidised in TCA cycle
