W5 - Fat Metabolism Flashcards by Holly Tomlinson

What are fats usually carried in around the body because they have detergent like properties?

lipoproteins

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What are simple lipids

Lipids composed of only FAs, glycerols + alcohols

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What are complex lipids

Lipids that contain FAs, glycerols + other groups

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What do lipoproteins carry?

TAGs

Cholesterol

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Which parts of a lipoprotein are hydrophilic + which are hydrophobic?

Hydrophilic shell

Hydrophobic core

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What does the outer layer of a lipoprotein contain?

Monophospholipids

Cholesterol

Protein

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There are 4 main lipoproteins in the human body.

What do they carry?

2 are main carries of TAG

2 of cholesterol esters

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List the 4 main lipoproteins

Chylomicrons

VLDL (Very low density lipoproteins)

LDL

HDL

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HDL or LDL for chylomicrons

ULDL (ultaLDL)

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Which is the biggest lipoprotein?

Chylomicrons

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What does the chylomicron carry?

90% TAG

Some Cholesterol esters (CE)

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% of protein + lipids in chylomicrons

High or low?

Protein = lowest %

Lipids = highest %

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Where are chylomicrons made?

Small intestine

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What do VLDLs carry?

TAG

Cholesterol esters

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Where are VLDLs made?

Liver

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What do LDLs carry?

ONLY cholesterol esters

LDLs - considered bad cholesterol

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What do HDLs carry?

ONLY cholesterol esters

HDLs - considered good cholesterol

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Which lipoprotein has the highest % of protein?

HDL

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What are probably the strongest lipid predictor for CV disease?

HDLs

Higher content in blood = ⬇️ risk of CV disease

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Quick overview of the consumption + absorption of fats

TAGs broken down by lipase

Packaged into myocells

Transferred into epithelial

Synthesised by chylomicrons

Into lacteal which drains into lymph, then blood + subclavian vein.

== Chylomicrons in circulation

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Fat absorption has happened in the postprandial state.

Want to store the fat.

Where do the chylomicrons travel to?

Then what happens?

Extra hepatic tissues

Bv here have LPL on their walls.

= Chylomicrons dock onto this enzyme to be broken so the TAGs can be broken down to release FAs + glycerol.

FAs enter tissues.

Repackaged into TAGs + stored.

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What is the chylomicron called once it has lost most of its TAGs when docked onto the lipoprotein lipase in bv walls?

Chylomicron/lipoprotein remnant

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Where is the Chylomicron/lipoprotein remnant transported to

Liver

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What happens to the Chylomicron/lipoprotein remnant in the liver?

Broken down + reutilised.

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What happens to the cholesterol of the Chylomicron/lipoprotein remnant once it has been broken down + reutilised in the liver?

Joins a pool of cholesterol in the liver where has many functions. 1 of which = Bile created Can also be packaged into LDL to take cholesterol to the other bodys tissues.

How can more cholesterol enter bloodstream?

Low HDL levels High LDL

What does the liver do with the fat it contains?

Packages it into VLDL VLDL sent to peripheral tissues so they can store the TAG.

What are the 4 ways of regulating FA utilisation?

Lipolysis of TAG to form FFAs Re-esterification of FAs or mobilisation from adipose tissue Transport of ACoA into mit Availability of FAD + NAD for b-oxidation

In what states can adipocytes in adipose tissue be used?

Post absorptive states + exercise

How is HSL (hormone sensitive lipase) regulated?

By phosphorylation.

What enzyme converts the inactive form of HSL to its active form and how?

Protein kinase By adding a phosphate group.

What stimulates protein kinase to convert inactive HSL to active HSL?

Ca2+ Adrenaline = Both i.e from exercise Growth hormone cortisol (i.e from stress)

When wouldn't you want HSL in its active form?

Just after eating

Enzyme to convert HSL in its active form to HSL in its inactive form?

Phosphatase

What stimulates phosphatase to convert HSL in its active form to HSL in its inactive form?

Insulin

Why is it difficult to get FAs out of the adipocytes?

Due to re-esterification

Does the glycerol in the adipocyte need to go or can it stay?

Needs to go. Can't be reused to make TAG.

How is a fatty acyl-CoA converted back into TG?

By reesterification + the addition of a-glycerol-P

What happens to lipolysis with exercise?

⬆️

What is FA transport across cell membranes dependent on?

Plasma FA conc

What are the functional protein carriers allowing FA transport across cell membranes?

FABP (FA binding protein) FAT/CD36 (FA translocase) FATP (FA transport protein)

What happens to the FA once inside the cell?

Becomes fatty-acyl-CoA by Acyl-CoA synthethase enzymes.

Where can the FAs come from when moving from the blood into the interstitial fluid?

Chylomicron VLDL Albumin

How do FAs move from the interstitial fluid into the sarcoplasm of a muscle cell?

⬇️ conc grad through FAT/CD36.

What happens to the Fatty-acyl-CoAs in the cell?

Can either: - be incorporated into lipid pools OR - be oxidised by mit for energy

Give an example of a lipid pool in muscles

IMTG droplets | Intramuscular TG

Lipolysis of IMTG, by what enzyme?

Active form of HSL

What is protein kinase stimulated when converting inactive form of HSL to active form for the lipolysis of IMTG?

Ca2+ Adrenaline AMP

Membranes of the mitochondria in regards to lipid permeability

Outer - permeable to lipids Inner - IMpermerable to lipids

Where is the CPT 1 located in the mitochondria?

Outer membrane

What does CPT 1 do in the carnitine shuttle?

Attaches carnitine group to acyl-CoA removes CoA from acyl-CoA == Acyl-carnitine

What in the mitochondria helps acyl-carnitine move across the inner membrane into the mit matrix?

CACT (Carnitine acyl carnitine translocase)

What must happen once the acyl-carnitine has entered the mit matrix? How does this happen?

Need to remove carnitine group Put CoA back on == By CPT2 === AcylCoA now ready in mitochondrial matrix

What happens to the AcylCoA once in the mit matrix?

Undergoes b-oxidation

What are the later forms of Acyl CoA as it goes through the b-oxidation cycle in the matrix of the mitochondria before entering the TCA cycle as Acetyl-CoA (ACoA)?

Acyl CoA 2-trans-enoyl CoA L-3-hydroxyl acyl CoA 3-ketoacyl coA

Which is the rate limiting enzyme in the b-oxidation cycle in the matrix of the mitochondria for Acyl-CoA

3rd enzyme = Beta hydroxy Acyl CoA dehydrogenase (beta HAD)

What happens to plasma FA conc during prolonged exercise?

⬆️ after an initial drop

Why is there an initial drop in plasma FA during prolonged exercise when looking at a graph?

Slow FA mobilisation from adipose tissue Uptake of FA from working muscles straight away

Why does plasma FA conc increase during prolonged exercise?

Insulin is red. so less glucose in blood Adrenaline is increased. Glycerol stores may be depleted. == ⬆️ HSL = ⬆️ lipolysis = ⬆️ FA in blood

What does increase FA in plasma result in during exercise?

Greater flux = drives a FA oxidation increase

What does an increased FA flux into plasma do to CHO?

⬆️ acetyl-CoA = inhibits PDH + PFK, ⬆️ citrate accumulation == G-6-P accumulates = glycogenolysis inhibited = ⬇️ con grad for glucose uptake == ⬇️ CHO oxidation

Which of LDL + HDL has a longer half-life ?

LDL Lasts 1.5-2 days

How long do chylomicrons VLDLs last in the body?

Few hours

What does damage to the LDL enable?

⬆️ its affinity to bind to a receptor on macrophages. Taken into macrophage,

How can LDLs be damaged?

Toxins Free radicals High glucose

Do macrophages have cholesterol sensors?

What does it mean that macrophages don't have cholesterol sensors?

They keep taking in LDLs == Changed into a foam cell (bigger than a macrophage)

Can foam cells penetrate bv walls?

yes

What can an accumulation of foam cells on vessel walls cause?

Inflammation which can lead to fatty streaks. --> Atherosclerosis

What can HDL do in regards to the foam cells?

Can dock onto its receptor + remove the excess cholesterol. Takes cholesterol to liver where used for bile acids

Monounsaturated fats have how many double bonds

After FAs have been released from fat cells, what is the name of the protein carrier that transports them in blood?

Albumin

What is lipolysis NOT stimulated by?

Insulin

How are long chain fatty acids transported from the small intestine through the body?

In chylomicrons

Transport of fatty acids across the inner mitochondrial membrane is dependent upon...

Carnitine

What is involved in the transport of short chain fatty acids around the blood

Albumin

Increased glycogenolysis in exercise is likely due to...

Increased AMP

What will inhibition of PFK do to CHO oxidation + glycolysis?

Inhibits it

What effect will a reduction in FAD have on flux through beta oxidation?

Reduce it

W5 - Fat Metabolism Flashcards

(79 cards)