Ch. 4 Lipids Biochem Simple

Front 1

Functions of lipids in the body

Back 1

1. Fuel-->broken down to form acetyl CoA, NADH (3 or 2 ATP depending on whether its in the cytosol) and FADH2 (2 ATP)

2. Cell membranes- (phospholipids, glycolipids, cholesterol) In the nervous system: (Sphingomyelin, cerebrosides, and gangliosides)

3. Steroid hormones: Lipids (with sterol ring--looks like a house). The side chain (attached to C17--the "chimney" determine activity.)

4. Bile acids- (they're lipids too). They're steroids w/ free -COOH group. Polar+non-polar nature infers detergent/emulsifying activity--(ie bind lipids + polar surroundings, increase surface area for emulsification/b.down in gut)

5. Prostaglanding-- lipids w/ diverse hormone-like functions

6. Fat-soluble vitamins (ADEK) = lipids

7. Lipids + carbohydrates/proteins (glycolipids, lipoproteins)

Front 2

Fat is stored as:

Back 2

Triglycerides. When attached to glycerol, fatty acids may be stored as triglycerides (fat)

Front 3

Pregnenolone, the first steroid hormone derivative of cholsterol gives rise to a # of different steroids:

Back 3

1. Sex hormones (estrogens, progesterone, testosterone)
2. Glucocorticoids (e.g.cortisol) causes a rise in serum glucose
3. Mineralocorticoids (aldosterone)--retain sodium in the body

Front 4

Glycocholate

Back 4

The main bile salt.

Front 5

aldosterone

Back 5

A mineralocorticoid. Mineralocorticoids retain sodium in the body.

Front 6

Fatty acids

Back 6

Ubiquitous, used as fuel, synthesis of other types of molecules.

Hydrocarbon chain w/ terminal -COOH. Typically 14-25 Carbons (16-18 most abundant).

Two types, unsaturated and saturated!

Front 7

Unsaturated Fatty Acids

Back 7

Contain double bonds between some carbon atoms

Ex: Linoleic acid and Arachidonic acid

Front 8

Saturated Fatty Acids

Back 8

Contain only single bonds.

Ex: Palmitic acid and Stearic acid

Front 9

Why do fatty acid chains typically contain an even number of carbons?

Back 9

They are generally built up (and broken down) in units of 2 carbons at a time.

Front 10

During fatty acid synthesis, 2 carbons are added to the fatty acid chain at a time. How are these 2 carbons added and where do they came from?

Back 10

the 2 carbons are gained as an acetyl group from Acetyl CoA with each round of synthesis.

Carbons affix to acyl (fatty acid) carrier protein (ACP).

Front 11

During lipid oxidation, two carbons are lost from the fatty acid chain during each cycle of oxidation.

Back 11

Carbons attach to CoA

Front 12

How does fatty acid breakdown provide energy?

Back 12

This is an important source of energy. NADH and FADH2 are generated!!

Moreover, ACETYL CoA IS FORMED, which can fuel the Krebs cycle.

Front 13

During fatty acid oxidation, with each round of 2 carbon loss, how much NADH, FADH2, acetyl CoA, and ATP is produced?

Back 13

Every round of 2C loss produces its own NADH, FADH2, and acetyl CoA (and a net total of 17ATPs!)

Front 14

What energy molecules are produced during fatty acid oxidation? (per 2C loss)

Back 14

1 mol NADH, 1 mol FADH2, 1 mol AcetylCoA

(can generate 17 ATP)

Front 15

Why are lipids more energy efficient molecules than carbohydrates and proteins?

Back 15

Lipids (9kcal/g) are more energy efficient than proteins and carbohydrates (4 kcal/g) because of considerable energy released in multiple cycles of fatty acid oxidation. Also non-polar nature which doesn't bind water allows for dehydrated, compact packaging).

Front 16

How can triglycerides help maintain blood sugar?

Back 16

When blood sugar is low, epinephrine, NE, and glucagon stimulate LIPASE to break down triglycerides.

The glycerol portion of the triglyceride can then be shuttled in to make more glucose.

Front 17

Hormonal signal for triglyceride breakdown?

Back 17

Epinephrine, Norepinephrine and Glucagon stimulate "lipase" via cAMP second messenger-->carrying message to activate lipase.

This is analagous to phorphorylase activation in glycogenolysis.

Front 18

How does insulin impact lipid breakdown and glycogen synthesis?

Back 18

During the well-fed state, insulin inhibits lipid breakdown and increases the following:

glycogen synthesis, fatty acids, triglycerides, and proteins.

Insulin reduces cAMP, promotes glucose uptake into cells (especially fat) where glucose can be converted and stored as triglyceride.

Front 19

Essential fatty acids

Back 19

Certain modifications are required for dealing wth unsaturated and odd chain fatty acids.

Linoleate (C18) and linolenate (C18) are "essential" and are required in the diet. We cannot synthesize their double bonds.

Front 20

Lipid synthesis occurs by how many carbons at a time?

Back 20

2

Front 21

In lipid synthesis, carbons are gained in the form of _____

Back 21

an acetyl group from acetyl CoA (Gained)

Front 22

Carbons gained in fatty acid synthesis are attached to

Back 22

acyl (fatty acid) carrier protein (ACP)

Front 23

Carbons removed from fatty acid chains during fatty acid oxidation are affixed to

Back 23

CoA

Front 24

Fatty acid breakdown results in what energy molecules?

Back 24

NADH, FADH, and acetyl CoA (which can enter the Krebs cycle)

Front 25

Each round of 2 carbon losses produces:

Back 25

1 NADH, FADH2 and acetyl CoA respectively.

This results in 17 ATPs for each round of 2-carbon loss

Front 26

Why are lipids more energy efficient than carbohydrates?

Back 26

They have 9kcal/g energy vs 4cal/g for carbs and proteins.

They release a great deal of energy via multiple rounds of fatty acid ox, and they are hydrophobic, non-polar (compact/dehydrated state)

Front 27

When blood sugar is low, how are fats used?

Back 27

Epinephrine, NE, and glucagon stimulate LIPASE via cAMP 2nd messenger.

This breaks down triglycerides, freeing the glycerol portion to be used as glucose.

This is reminescent of how cAMP activates phosphorylase during glycogenolysis

Front 28

Summarize insulin activity

Back 28

1. inhibits breakdown of lipids
2. Increases synthesis of glycogen, fatty acids, triglycerides and proteins
3. lowers cAMP levels
4. promotes glucose uptake into cells like fat (where glucose can be stored as triglyceride)

Front 29

Linoleate (C18) and linolenate (C18) are what?

Back 29

Essential fatty acids, we cannot synthesize their double bonds.

Front 30

Ketones are produced when?

Back 30

during the course of fatty acid breakdown. At the point where the fatty acid is degraded to the 4-carbon acetoacetyl CoA. From that point, a # of possible events can occur:

Front 31

During fatty acid breakdown, the 4-carbon acetoacetyl can either:

Back 31

1. breakdown further to acetyl CoA
2. Change to Ketones (acetoacete (C4), hydroxybutyrate (C4), and acetone (C3))
3. Be used for synthesis of cholesterol and its many derivatives

Front 32

What might cause ketones to be elevated?

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1. In starvation, the batty mobilizes fatty acids stored as triglycerides to break down, and this leads to some of the acetoacetyl CoA produced to form ketones.

2. In diabetes mellitus, glucose may not enter cells, so triglycerides must be broken down to provide fatty acids and acetyl CoA as fuel in absence of glucose-->some of the acetoacetyl CoA can form ketones. Sometimes you can smell acetone from these patients.

Front 33

How are fatty acids stored?

Back 33

Fatty acids are stored on glycerol coat rocks in fat cells.

Front 34

Glycerol structure

Back 34

C3H8O3. 3 carbon chain with a hydroxyl group on each carbon. Think of it as a 3 carbon coat rack with a hydroxyl group on each carbon.

Fatty acids are placed on the coat rack, forming "glycerides"

Front 35

Provide examples of glycerides:

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1. monoglycerides (one fatty acid on glycerol coat rack)
2. diglycerides (Two fatty acids on glycerol coat rack)
3. triglycerides (three fatty acids on glycerol coat rack)

Front 36

Acyl CoA

Back 36

CoA attaches to the fatty acid. Acyl CoA means a fatty acid attached to CoA. ("The hand that holds the fatty acid up to the coat rack is CoA).


So, Acyl CoAs (CoA's carrying a fatty acid) can then combine with glycerol to form triglycerides.

Front 37

Triglycerides

Back 37

Primary storage form of lipids. These can revert to fatty acids + glycerol, which can be used as fuel.

Front 38

Why might we get fat from eating too many candy bars?

Back 38

Consumption of excess sugar /calories basically gives us xs. acetyl CoA, which then combines with 3-Glycerol to form Triglycerides.

Front 39

Provide examples of some biochemically important phosphoglycerides

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1. phosphatidyl inositol
2. phosphatidyl serine
3. phosphatidyl choline
4. phosphatidyl ethanolamine
5. phosphatidate

Front 40

Structure of a phosphoglycerides

Back 40

Take a glycerol mole, and attach Acyl CoA (fatty acids + CoA) to the first two carbons.

The last (3rd) glycerol carbon gets a phosphate linkage to another group, AKA "something nice!"

Front 41

Phosphoglycerides are important in the body for what reasons?

Back 41

1. important membrane omponents
2. Starting point for the synthesis of many prostaglanding-like molecules

Front 42

Prostaglandin Structure

Back 42

"Frog looking" with 20 Carbons arranged as a 5-Carbon ring with 2 legs (one of which contains a -COOH group)

Front 43

Prostaglandins, thromboxanes, and leukotrienes are derived from:

Back 43

polyunsaturated fatty acids such as arachidonic acid

Front 44

How do prostacyclins, thromboxanes, and leukotrienes differ structurally from prostaglandins?

Back 44

Prostacyclins have an extra ring, thromboxanes have an additional oxygen, and leukotrienes do not have an enclosed ring.

Front 45

Name some of the physiological functions of prostaglandins:

Back 45

1. smooth muscle contraction (ie. in asthma)-- affected are blood pressure, blood flow, the degree of bronchial constriction, and uterine contraction

2. Platelet aggregation. (Thromboxane is potent enhances of platelet aggregation, while proastacyclin inhibits and is a vasodilator")

3. Certain prostaglandins promote the inflammatory response. The leukotrienes act as chemotactic agents, attracting leukocytes to the site of inflammation.

4. Appear to incrase pain and fever, or induce sleep/wakefulness-->perhaps acting on certain regions of the hypothalamus.

Front 46

Differences between sphingolipids and triglycerides

Back 46

In triglycerides, the 3-carbon glycerol molecule serves rather like "coat rack" for fatty acids.

In the case of sphingolipids, the "coat rack" is made from serine (another 3-Carbon molecule), but it's an amino acid (an NH2 and -COOH group replacing 2/3 of glycerol's -OH groups).

Front 47

Sphingosine

Back 47

A sphingosine takes serine (a 3-carbon amino acid), and links the -COOH group with a direct carbon-carbon bond to palminitoyl CoA (palmitic acid is a long saturated fatty acid).

Front 48

Ceramide

Back 48

Palmitoyl CoA joins Serine to form Sphingosine (saturated fatty acid joined via C-C to -COOH of Serine0.

In "ceramide" a second fatty acid joins with the -NH2 group. Now there are 2 fatty acids on the "serine" rack.

Front 49

After the -COOH group and -NH2 group of serine combines with fatty acids to form 2 fatty acid chains, what other subclasses of sphingolipids can form when the remaining -OH group combines with other molecules?

Back 49

1. Sphingomyelin--has a phosphoryl choline attached to the third carbon -OH. It is the only phospho-sphingolipid.

2. Sugars may attach to the 3rd carbon -OH group. Now we're talking about glycolipids (which are important components of cell membranes.)

Front 50

Name the 3 ketones

Back 50

1. acetoacetate
2. 3-hydroxybutyrate
3. acetone

Front 51

Cholesterol structure

Back 51

Cholesterol contains a "sterol" ring, is the precusor to other sterol-containing molecules such as steroid hormones and bile acids.

Front 52

All of the carbons of cholesterol come from?

Back 52

Acetyl CoA.

Acetyl CoA units combine to form the 6-carbon molecule, 3-methl-glutaryl CoA (HMG-CoA), and then a 5-carbon building block isoprene which links up in multiple units with other isoprene units. The C5 becomes C10, C15, C30-->and then some last minute modifications, cholesterol, which has 27 CARBONS!

Front 53

Isoprenoid molecules

Back 53

Isoprenes give rise to many things:

1. Vitamin E, all the fat-soluble vitamins (ADEK), coenzyme Q (used in e. transport in krebs cycle), and dolichol (isoprene polymer that participates in transfer of oligosaccharides during glycoprotein synthesis).

Front 54

Cytochrome P450

Back 54

Facilitates the incorporation of oxygen in a # of reactions. Hydroxylation (occurs at a number of points in synthesis of cholesterol involves oxygen incporation).

This hydroxylation is used to detoxify certain drugs (like barbiturates).

Front 55

Steroid hormones (including mineralocorticoids, glucocorticoids and sex hormones) and bile salts are derived from:

Back 55

cholesterol

Front 56

Cholesterol is converted to what molecule that is the precursor to all steroid hormones (and prevents the cholesterol from becoming bile derivatives)?

Back 56

Pregenolone

Front 57

What molecule is key in fatty acid synthesis?

Back 57

Acetyl CoA

Front 58

Triglycerides break down into:

Back 58

glycerol and AcetylCoA