Lecture 44 11/29/23 Flashcards
What are the sources of carbohydrates?
-starches and polysaccharides
-glycogen
-disaccharides
-fiber
What are the possible fates of carbohydrates in the body?
-metabolized to produce ATP
-stored in liver and muscle as glycogen
-converted to fatty acids and stored as triglycerides in adipose tissue
What are the steps of glucose metabolism?
-glycolysis converting glucose to pyruvate
-conversion of pyruvate to acetyl-CoA
-citric acid cycle converting acetyl-CoA to CO2
-electron transport chain to create ATP from released energy
What are the characteristics of anaerobic glycolysis?
-converts pyruvate to lactate
-occurs in the absence of oxygen
What are the characteristics of glucose storage?
-primarily stored in liver and muscle as glycogen
-liver stores are available for all tissues
-muscle stores are only available for muscle
-liver stores affect blood glucose levels
What happens after a carbohydrate-containing meal?
-glucose enters portal circulation and liver hepatocytes
-insulin is released by pancreas
-insulin stimulates glycogen synthase to convert glucose to glycogen in glycogenesis
What are the steps of glucose storage in adipose tissue?
-excess glucose is converted to fatty acids
-fatty acids are converted to triglycerides
-triglycerides are converted to adipose tissue
What are the characteristics of glycogenolysis?
-break down of glycogen to release glucose
-stimulated by glucagon and epinephrine
What are the characteristics of gluconeogenesis?
-formation of glucose from non-carbohydrate substrates
-occurs mostly in liver and somewhat in kidneys
-occurs when blood glucose levels are low
Which types of fats are ingested?
-triglycerides
-phospholipids
-cholesterol esters
What are saturated fatty acids?
fatty acids with no double bonds
What are unsaturated fatty acids?
fatty acids with one or more double bonds
What are omega 3 polyunsaturated fatty acids?
fatty acid in which the third bond from the methyl end is the first double bond present
What are omega 6 polyunsaturated fatty acids?
fatty acid in which the sixth bond from the methyl end is the first double bond present
What are the characteristics of fatty acid oxidation?
-fatty acids are broken down into acetyl-CoA, which enters citric acid cycle
-occurs in the mitochondria
-carnitine required for fatty acids to enter mitochondria
When does ketone formation occur?
when glucose metabolism is low
What are the characteristics of ketone formation?
-liver forms beta-hydroxybutyrate and acetoacetate from acetyl-CoA
-ketones are converted to acetyl-CoA when entering the Kreb’s cycle to produce energy
Where do the FFAs used to form ketones come from?
lipolysis
What are the general characteristics of plasma lipids?
-free fatty acids bound to albumin
-major lipids do not circulate in free form
What are the characteristics of chylomicrons?
-transport dietary lipids
-very large lipoproteins created in enterocytes
-cleared by lipoprotein lipase/LPL on the surface of capillaries
What is the function of LPL?
-breaks down the triglyceride in chylomicrons and VLDLs
-produces free fatty acids and glycerol
What are the characteristics of VLDLs?
-deposit triglycerides into tissue
-become IDL after LPL removes triglycerides
What are the characteristics of IDL?
-removes cholesterol esters from HDL via cholesterol ester binding protein (CETP)
-eventually becomes LDL cholesterol
Why are dogs and cats not prone to heart attacks?
they lack cholesterol ester binding protein
What is the main function of LDL?
depositing cholesterols into peripheral tissue
What is the main function of HDL?
transferring cholesterol from peripheral tissues to the liver, where it is excreted as bile
What are the characteristics of essential fatty acids?
-required in the diet
-involved in fat-soluble vitamin absorption
-make eicosanoids and other signaling compounds
Which omega-6 fatty acid is an important essential fatty acid?
linoleic acid
What are the potential sources of omega-3 fatty acids?
-alpha-linolenic acid found in plant oils
-eicosapentanoic acid and docosahexanoic acid found in marine oils
Which eicosanoid type is produced from omega-6 fatty acids?
pro-inflammatory and pro-thrombotic
Which eicosanoid type is produced from omega-3 fatty acids?
anti-inflammatory and anti-thrombotic
What signs are seen with essential fatty acid deficiencies?
-dull, dry coat
-seborrhea
-alopecia
-greasy skin
-pyoderma
What is provided by dietary protein?
-essential amino acids
-nitrogen and carbon skeletons
What is the fate of both essential and non-essential amino acids?
become part of the AA pool for protein synthesis in the tissues
What are the functions of protein?
-structural components of organs and tissues
-source of energy
What are the characteristics of endogenous protein as an energy source?
-not intended to be a source of energy; only structural
-used for energy when exogenous energy/protein intake is too low
What are essential amino acids?
AAs that cannot be synthesized by the body and therefore must be obtained via diet
What are the characteristics of dispensable amino acids?
-can be synthesized if appropriate nitrogen and carbon sources are available
-required for hormone synthesis, DNA synthesis, and neurotransmitter production
Which amino acid is only essential in strict carnivores?
taurine
What happens in protein catabolism?
-amine group is broken off carbon skeleton
-amine group becomes ammonia, which is processed into urea
-carbon skeleton becomes a source of energy
What is the role of the urea cycle?
to reduce ammonia levels by converting it into urea
