Unit 4 Lecture 31 Flashcards
How are lipids transported in the blood?
by lipoporteins
How are lipoproteins categorized?
function and denstiy
What are the 4 major classes of lipoproteins?
- chylomicrons
- very low density
- low density
- high density
What is chylomicrons made of?
- 2% protein and 85% TG
Where do chylomicrons form and what is their function?
form in intestinal epithelial cells to transport dietary fats to adipose cells
What are very low density lipoproteins made of?
10% protein and 50% TG
Where do very low density lipoproteins form and what are their functions?
Form in hepatocytes to transport triglycerides to adipose cells
- long term storage
What are low density lipoproteins made of?
25% protein and 50% BAD cholesterol
What is the function of LDL?
carry blood cholesterol to body cells
What is HDLs made of?
40% protein and 20% GOOD cholesterol
What is the function of HDLs?
carry cholesterol from cells to liver for elimination
- incorporated in bile
What happens to lipids?
- oxidized to make ATP
- excess stored in adipose or liver
- synthesize structural or other important molecules (phospholipids, lipoproteins, thromboplastin, myelin shaths, cholesterol)
What is thromboplastin?
phospholipids and tissue factor (both are needed to activate the extrinsic pathway of blood clotting)
What are the 2 stages of lipid metabolism?
- lipolysis
2. lipogenesis
Define lipolysis
TG are broken down into glycerol and fatty caids w/in liver or adipose cells in the presence of catecholemines (NE or E) and cortisol
Define lipogenesis
TG are synthesized from amino acids or glucose within liver or adipose cells in the presence of insulin
How does lipolysis connect to the krebs cycle?
TG -> fatty acids (and glycerol) -> undergoes beta oxidation in mitochondria -> Acetyl CoA -> lots of ATP in krebs cycle
Define ketogenesis
the formation of ketone bodies from acetyl coA during lipolysis
What is the difference between lipogenesis and lipolysis?
lipogenesis- makes TG from stuff
lipolysis- breaks down TG into stuff
What fuel sources, “stuff”, is used to make TG during lipogenesis?
amino acids, glycolysis metabolites (used in glycerol production), and ketone bodies
What is the fate of proteins
broken down into amino acids which are transported to the liver
What happens to amino acids?
- deaminated to enter krebs cycle
- donate amino group to form new amino acids (transamination)
- used to synthesize new protein throughout the body
What can happen to excess amino acids?
may be converted into glucose or triglycerides (no storage)
What stimulates Amino acids to be absorbed into body cells?
insulin-like growth factors (IGFs) and insulin
What are the two metabolism “states” after eating?
absorptive and post-absorptive state
What organ/s are used during the absorptive state?
Gastrointestinal tract (mostly intestines)
What organ/s are used during the post-absorptive state?
Liver
What is the absorptive state?
The time after a meal when nutrients enter the blood and need to be stored
What is the post- absorptive state?
4 hours after a meal when absorption of all nutrients is complete (like starvation)
What does the GI tract do to glucose and nutrients during the absorptive state?
sends it into blood stream to be picked up by other organs
List some places where glucose and nutrients are picked up during absorptive state
- excess fuels stored in hepatocytes, adipocytes or skeletal muscle
- glucose entering liver is converted to glycogen or triglycerides
- dietary lipids stored in adipose tissue
- AA deaminated for Krebs or turned into glucose or fatty acid
What is the biggest challenge during post-absorptive state?
maintaining normal blood glucose level (70-110 mg/dL blood)
What is the goal of the post-absorptive state?
put glucose back into bloodstream after it was taken in by liver from GI tract - or - use alternative fuel sources
During what processes does glucose enter blood from the liver?
- glycogenolysis
2. gluconeogenesis
What happens during gluconeogenesis?
- glycerol from adipose tissue
- amino acids and lactic acid from muscle
What are some of the alternative fuel sources?
- fatty acids from adipose fed into Krebs as Acetyl CoA for most cells
- oxidation of ketone bodies by heart and kidney
