M2e L22-24 Flashcards
Outline the main types of animal lipids and their biochemical/physiological functions
free fatty acids: they have a carboxylic group, fatty acid bc of presence of hydrocarbon alkyl chain, saturated or unsaturated, precursor of other lipids
triacylglycerols: major fuel source in animals, mobilized to Fprovide an energy source
phospholipids, glycolipids, cholesterol: important components of biological membranes, solubilization of non-polar substances in body fluids, glycolipids are lipids with sugar molecules attached
steroid hormones, prostaglandins: they are built upon cholesterol, synthesis starts from cholesterol
Outline the main concepts of control of fatty acid metabolism
FA synthesis is controlled by availability of glucose
FA oxidation is controlled by the availability of fatty acids
Explain why linoleic and linolenic acids are classified as essential fatty acids and why cats need arachidonic acid in their diets
linoleic acid cannot be make by animals, cant make enough linolenic. needed to make arachidonic
cats can’t make arachidonic acid
Outline fatty acid synthesis and its rate limiting step (details of each step in the cyclical process are not required)
Start with acetol bound to KS site and malonyl group bound to ACP.
condensation reaction: joining 2 molecules together, losing a carbon, CO, becomes 4c, ketoacyl. The acetyl group (ketone) is reduced to an alcohol intermediate and then further reduced to alkyl CH2CH3 using NADPH.
The 7 cycles repeat adding 2c with each cycle until C16:0 is formed, palmitate. Each cycle a new malonyl - CoA is used to add 2C (with the loss of CO 2) growing the fatty acid chain by 2C each cycle
in the cytosol
Describe the way in which reducing equivalents from fatty acid oxidation contribute to the overall yield of ATP
it yields 8 A-CoA, 7 FADH2 and 7 NADH
Explain why fat is a useful store of metabolic energy
Complete oxidation of fat yields more energy/g than carbohydrate or protein. Fatty acid synthesis is regulated, but the total capacity of fat storage is not, does not need water
Excess carbohydrates are readily converted to fat
Outline the system for transport of fatty acids from the cytosol to the mitochondrion
Acyl-CoA synthetase activates fatty acids with coenzyme A (CoA) to form fatty acyl-CoAs, which are then changed to acylcarnitine through an enzyme called CPT-1. the acylcarnitine moves from the cytosol to the intermembrane space, where a protein called acylcarnitine translocase moves it to the matrix, where an the enzyme CPT-2 changes it to acyl-coa and carnitine so acyl-coa can go through beta oxidation
Outline fatty acid oxidation and its role in ATP synthesis
Fats are mobilized by the lipases, from TAG, from adipose tissue to other tissues, signaled by glucagon hormone, once in the bloodstream the fatty acids are taken up by peripheral tissues, they then are transported into the matrix of the mitochondria where the enzymes are, they then have 2 membranes to cross, they must be activated to fatty acyl coa by acetyl CoA. The fatty acyl CoA is transported using two different membrane transporters and are released in the matrix as a fatty acyl CoA, ready for fatty acid oxidation
in the mitochondria
Describe the mobilization of triacylglycerols and the conditions under which mobilization occurs
Pancreas secretes hydrolytic enzymes so the lipases can break down the ester bonds of the TAG into their components fatty acids, glycerol backbone and monoacylglycerol absorbed through the cell membrane of the intestinal cells, the products of the dietary lipids absorb into cells and then the TAGs are reformed, packaged into chylomicron, will then circulate via the lymph system through the circulatory system in the capillaries.
Polar coat, hydrophobic cargo inside, chylomicrons fly through the tissue, attached to the cell membrane by the polysaccharide chain, which will break down TAG in the cargo of the chylomicron into the free fatty acids, the glycerol backbone, and a monoacylglycerol. The cell can either use those products for energy production or storage. fasting state or well-fed state
Describe the breakdown of dietary fats & the roles of lipoproteins in transport of lipids
the fat droplets are dispersed into smaller particles by bile salts, it makes it easier for the lipids to be broken down. the lipids are transported for absorption through the intestinal epithelial cells. the TAGs are resynthesized in the endoplasmic reticulum and Golgi complex. lumen –> small intestine. the molecules are then absorbed into cells, they can be moved around into the rest of the animal. they are packaged into chylomicrons with proteins to shield hydrophobic TAGs from aqueous solution
How many membranes does a fatty acid need to cross before it can be oxidized to carbon dioxide and water?
3
what is the structure of a triacylglycerol?
a glycerol with a long chain fatty acid
describe the fatty oxidation cycle
Dehydrogenation catalyzed by acyl-CoA dehydrogenase, which removes two hydrogens between C 2 and 3.
Hydration catalyzed by enoyl-CoA hydratase, which adds water across the double bond.
Dehydrogenation catalyzed by 3-hydroxyacyl-CoA dehydrogenase, which generates NADH.
Thiolytic cleavage catalyzed beta-ketothiolase, which cleaves the terminal acetyl-CoA group and forms acyl-CoA which is two carbons shorter than the previous one. re used in the cycle
where, when are fatty acids used for energy?
fatty acids are synthesized in adipose tissue and liver when carbs are in excess, they are esterified into triacyclglycerols and stored in adipose tissue
under low blood glucose, FA are mobilized from adipose tissue by hydrolysis of the ester linkages, in circulation FA bind to albumin
FA are oxidized and produce Acetyl-CoA which enters the TCA cycle, NADH and FADH2 are produced and re oxidized by the ETC, ATP is produced by oxidative phosphorylation
