BCHM 102 - Module 4

What are the functions of lipids

What are the functions of lipids

• source of stored energy

• cell membranes

• vitamins

• structures of prostaglandins and steroids

What are some properties of lipids

• hydrophobic

• insoluble

• hydrophobic interactions

What are the 5 classes of lipids

• fatty acids

• triacylglycerols

• phospholipids

• glycolipids

• steroids

Describe fatty acids

• chain of hydrocarbons that end in a carboxylic acid

• most common fuel source

• most simple lipid

Describe triacylglycerols (TAGs)

• glycerol backbone attached to 3 fatty acids

• most common storage molecule

• stored in adipose tissue as liquid

Describe phospholipids

• 1 phosphate group, 1 glycerol, 2 fatty acids

• make up membranes

• amphipathic

Describe glycolipids

• sugar + fatty acid

• found on outer cell membranes

• functions in cell-cell interactions

Describe steroids

• cyclic lipids

• functions as hormones, lipid digestion, and membrane fluidity

• cholesterol is most common form

Where does dietary lipid digestion begin

in the stomach

How are dietary lipids degraded

mechanical mixing emulsifies fats in stomach, followed by emulsification using bile salt in small intestine

What is the goal with emulsification

increases the surface area of the fats and helps make peristalsis easier

What are the enzymes used to breakdown lipids

lingual lipase (from tongue glands)

gastric lipase (from stomach lining)

pancreatic lipase (from pancreas)

What are the products of lipid digestion

2 free fatty acids and a 2-monoacylglycerol

What are miscelles

they are mixtures of products and bile salts

they carry the products of lipid digestion to intestinal cells to be absorbed

What happens after absorption of lipids in intestinal cells

products are resynthesized into TAGs and packaged for transport

What are lipoproteins and what are the 4 classes

made of triacylglycerol and cholesteryl esters on inside, cholestrol & phospholipids & apolipoproteins on outside

found in blood to keep lipids in a soluble form while being delivered to tissues

classes are chylomicrons, very low density lipoproteins, low density lipoproteins, and high density lipoproteins

Describe the size, lipid/protein ratio, and plasma composition in each lipoprotein

chylomicrons

• large

• most lipid content compared to protein

• contains mostly TAGs

VLDL

• mid-size

• slightly higher content of protein compared to lipid

• contains TAGs, but also de-novo fat from liver to carry to body tissues

LDL

• smaller

• higher protein content compared to lipid

• contains cholesterol and cholesteryl esters, but also remaining TAGs after VLDL delivers TAGs

HDL

• smallest

• most dense with protein

• contains free cholesterol, phospholipids, and apolipoproteins

How are fats delivered to tissues

Chylomicron

• chylomicrons released from small intestine into blood

• fatty acids are cleaved from chylomicron TAGs by lipoprotein lipase and absorbed from capillaries into tissues

• chylomicron remnant returns to liver

VLDL

• VLDLs released from liver into blood

• fatty acids are cleaved from VLDL TAGs by lipoprotein lipase and absorbed from capillaries into tissues

• VLDL is converted to LDL in the process

What are the steps of fatty acid synthesis

1. Transport of acetyl CoA from mitochondria matrix to cytoplasm by converting to citrate to cross the membrane

2. Conversion of acetyl CoA to malonyl CoA

3. Synthesis of fatty acid by fatty acid synthase

What are the substrates of fatty acid synthesis

8 acetyl CoA, 7 ATP, 14 NADPH

What are the products of fatty acid synthesis

1 palmitate, 14 NADP+, 8 CoA, 6H2O, 7 ADP, 7 Pi

Where does fatty acid synthesis occur (in the form of TAG)

adipose tissue and liver

in the cytoplasm

What is the regulatory enzyme for fatty acid synthesis

acetyl CoA carboyxlase

• requires ATP

• committed step to activate acetyl CoA to malonyl CoA

• activated by insulin

• inhibited by glucagon and epinephrine

• phosphorylation inhibits it

Is fatty acid synthesis catabolic or anabolic

anabolic

What are the two rules for naming fatty acids

• carbon of COOH is carbon 1

• final methyl group is omega ω

What are the steps of fatty acid degradation

1. Release of fatty acids from TAG storage in adipose tissue

2. Activation of fatty acids by linkage to acetyl CoA

3. Fatty acid oxidation generates acetyl CoA, NADH, FADH2

What are the substrates of fatty acid degradation

1 Cn-acyl-CoA, 1 FAD, 1 NAD+, 1 H2O, 1 CoA

What are the products of fatty acid degradation, and what are the products of palmitate degradation in particular

fatty acid degradation: 1 FADH2, 1 NADH, 1 acetyl CoA, 12 ATP

palmitate degradation: 7 FADH2, 7 NADH, 8 acetyl CoA, 106 ATP

Where does fatty acid degradation occur

adipose tissue and liver

in the mitochondria

What are the regulatory enzymes for fatty acid degradation

hormone sensitive lipase

• activated by glucagon and epinephrine

• part of cascade to release fatty acids from adipose tissue

adipose triglyceride lipase

• activated by glucagon and epinephrine

• part of cascade to release fatty acids from adipose tissue

carnitine acyltransferase

• committed step to activate the carnitine shuttle to move acyl-CoA to the matrix

• inhibited by malonyl CoA

Is fatty acid degradation catabolic or anabolic

catabolic

Describe hypercholesterolemia

• high levels of cholesterol

• can lead to atherosclerosis

• found with high levels of LDL in plasma

• high cholesterol decreases receptors for LDL so excess becomes oxidized and macrophages engulf them to form foam cells (plaque)

What are ketone bodies

• alternative fuel source produced in mitochondria of liver from acetyl CoA by fatty acid degradation

• transported to heart, kidney, muscle, and brain

• water soluble

• good for fasting

What are the substrates of ketone body production

2 acetyl CoA

What are the products of ketone body production

1 ketone body, 1 acetone

What is the regulatory enzyme for ketone body production

HMG-CoA synthase

• activated by increased fatty acids and low glucose

• inhibited by decreased fatty acids and high glucose

Is fatty acid degradation catabolic or anabolic

catabolic

Describe ketoacidosis

• can occur in diabetics

• diabetics have lack of insulin, which creates more fatty acid degradation

• creates more acetyl CoA to be made into ketone bodies

• ketone bodies are acidic and can turn into acidosis in body if overproduced