Fat storage Flashcards
Where are triglycerides and cholesterol esters synthesised?
Smooth ER
What makes up VLDL?
Triglyceride and cholesterol
Apoprotein B
Where is apoprotein B synthesised?
Rough ER
What is function of microsomal TAG transfer protein?
Add lipid components to Apoprotein B
What is rate limiting for VLDL production?
FA *
State process of Fatty Acid export?
1) Apoprotein B (ApoB) synthesised in rough ER
2) Lipid components (TG, Cholesterol esters) synthesised in smooth
ER
3) Microsomal TAG transfer protein adds lipid components to ApoB
4) Transported in vesicle to Golgi
5) ApoB is glycosylated
6) Glycosylated Apo’s with lipid components bud off golgi
7) Migrate to sinusoidal membrane of hepatocyte
8) Vesicles fuse with the membranes and VLDL is releasd
Where is ApoB glycosylated?
Golgi apparatus
Where does glycosated Apo with lipid component migrate to?
Sinusoidal membrane of hepatocyte
What occurs if excess intake triglycerides?
1) Triglycerides reach liver
Accumulation
What function of lipogenesis?
Produce triglycerides from acetyl-CoA subunits
Triglycerides used as energy reserve
Stored in adipose tissue
What controls lvls of lipogenesis?
Insulin
What is rate limiting step in lipogenesis?
Acetyl-coA to malonyl-coA
What catalyses lipogenesis?
Acetyl CoA carboxylase
Does lipogenesis increase or decrease during fasting?
Reduce
Hepatic glycogen stores depleted
Triglycerides broken down in adipocytes
Free FA released
Is lipogenesis anabolic or catabolic?
Anabolic
Store
Where are FFA oxidised for energy source?
Liver
Where do lipids flow into liver from? (3)
1) Portal vein
2) Heptatic artery
3) Lymphatics
In what form are lipids transported to liver? (4)
1) Triglycerides
2) Lipoproteins
3) Chlyomicron remnants
4) HDLs
5) FA bound albumin
How are lipids uptaken into adipocyes?
Triglycerides can’t diffuse through cell membrane
1) Lipoprotein lipase breaks down triglycerides
2) Release free fatty acids
3) Fatty acids are lipophilic so diffuse through bilayer
4) Facilitated transport into the cells
What are the 3 transport systems for fa into liver? (3)
1) Fatty acid binding protein (mitochondrial AST)
2) Fatty acid translocase (FAT)
3) Fatty acid transport polypeptide (FATP)
Can triglycerides diffuse through membrane?
If not what can?
No
FFA can
What enzyme breaks down triglycerides
Lipoprotein lipase
What occurs do FA in adipocytes?
Re-esterified to triglycerides
Stored
Where does FA move after adipocytes?
Hepatocytes
Explain process movement from adipocytes to hepatocytes?
1) Sensitive lipase releases FFA
2) Hepatic lipase enables uptake FFA into hepatocytes
What hormone releases FFA from adipocytes?
Hormone Sensitive lipase
What enzyme enables uptake of FFA into hepatocytes?
Hepatic lipase
In what form are lipids released from liver?
VLDLs
How is energy released?
Oxidation
Is demand or storage greater for lipds?
Storage
List 3 functions of insulin?
Promotes fat storage in adipocytes
Stimulates lipoprotein lipase (break TG allow FA diffuse)
Reduces the activity of HSL (release FFA from adipo)
Explain process insulin resistance?
1) Increased lipolysis– more circulating triglycerides
2) More free fatty acids for hepatocytes to take up
3) Increased glucose level means lipids are less used as an energy source
How is the liver protected from large fatty acid influx?
Chylomicrons can bypass the liver
Transported in lymphatic system
Draw process fat moving inti adipocyte and into hepatocyte?
What function of glucagon?
1) Stimulate liver break down glycogen- released in blood as glucose
2) Activate gluconeogenesis- conversion of aa into glucose
3) Break down stored triglycerides into FA
What cells secrete glucagon?
Alpha cells of pancreas
What cells secrete insulin?
Pancreatic beta cells
Hypoglycemia results in…..g and i?
Alpha cells release glucagon
Beta cells prod insulin inhibit
Hyperglycemia results in….g and i?
Inhibits glucagon secretion
Stimulate beta cells prod insulin
Effect on blood sugar: glucagon and insulin
Glucagon- increases blood suger lvl
Insulin- decrease blood sugar lvl
