Biochemistry Chapter 11: Lipid and Amino Acid Metabolism Flashcards

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1
Q

Where does mechanical digestion of lipids primarily happen?

A

stomach

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2
Q

Where does chemical digestion of lipids occur?

A

the small intestine and is facilitated by bile, pancreatic lipase, colipase and cholesterol esterase

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3
Q

Digested lipids can be:

A

form micelles for absorption or be absorbed directly

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4
Q

Short-chain fatty acids are absorbed

A

across the intestine into the blood.

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5
Q

Long-chain fatty acids are absorbed

A

as micelles and assembled into chylomicrons for release into the lymphatic system

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6
Q

Lipids are mobilized from adipocytes by

A

hormone-sensitive lipase

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7
Q

Lipids are mobilized from lipoproteins by

A

lipoprotein lipase

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8
Q

Chylomicrons

A

the transport mechanism for dietary triacylglycerol molecules and are transported via the lymphatic system.

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9
Q

VLDL

A

transports newly synthesized traacylglycerol molecules from the liver to peripheral tissues in the bloodstream.

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10
Q

IDL

A

A VLDL remnant in transition between triacylglycerol and cholesterol transport; it picks up cholesteryl esters from HDL.

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11
Q

LDL

A

primarily transports cholesterol for use by tissues.

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12
Q

HDL

A

involved in the reverse transport of cholesterol.

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13
Q

Apoproteins

A

control interactions between lipoproteins

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14
Q

Cholesterol can be formed from:

A

dietary sources or through de novo synthesis in the liver

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15
Q

The key enzyme in cholesterol biosynthesis

A

HMG-CoA reductase

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16
Q

LCAT

A

catalyzes the formation of cholesteryl esters for transport with HDL

17
Q

CETP

A

catalyzes the transition of IDL to LDL by transferring cholesteryl esters from HDL

18
Q

Fatty acids

A

carboxylic acids with a (usually) single long chain, although they can be branched.

19
Q

Saturated fatty acids

A

have no double bonds between carbons

20
Q

Unsaturated fatty acids

A

have one or more double bonds

21
Q

Fatty acids are synthesized in___

A

the cytoplasm from acetyl-CoA transported out of the mitochondria

22
Q

What are the five steps of fatty acid synthesis?

A
activation
bond formation 
reduction
dehydration
2nd reduction

(Repeated, ex. 8 times to get palmitic acid)

23
Q

What is the only fatty acid that humans can synthesize?

A

palmitic acid

24
Q

Where does fatty acid oxidation occur?

A

in the mitochondria following transport by the carnitine shuttle

25
Q

Beta oxidation uses cycles of:

A

oxidation, hydration, oxidation & cleavage

26
Q

What types of fatty acids require special enzymes?

A

branched and unsaturated

27
Q

Unsaturated fatty acid enzymes

A

isomerase and an additional reductase

28
Q

When do ketone bodies form?

A

during a prolonged starvation due to excess acetyl-CoA in the liver

29
Q

Ketolysis

A

regenerates acetyl-CoA for use as an energy source in peripheral tissues

30
Q

Where does the brain get its energy during starvation?

A

from ketone bodies (up to 2/3 of energy)

31
Q

Where does protein digestion generally occur?

A

small intestine

32
Q

When does catabolism of cellular proteins occur?

A

conditions of starvation.

33
Q

How can amino acids be used for energy?

A

through either gluconeogenesis or ketone body formation.