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106 Cards in this Set

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  • Back
What are Triglycerides also known as?
Triacylglycerols or TAG's
What are TAGs composed of?
Glycerol + 3 Fatty Acids
Describe the structure of Fatty Acids?
1. Carboxyl Group + Long Chain

2. Varying length

3. May exist as solids (fats) or liquids (oils)

4. Can be either Saturated or Unsaturated in it's physical state
Which Fatty acids have double bonds?
Give an example of a saturated FA?
Stearic Acid
Give an example of a Monounsaturated FA?
Oleic Acid
Which are the most "healthy' of the the FAs?
Polyunsaturated FAs
Name 2 important polyunsaturated FAs?
1. Linolenic Acid (Omega-3 Fatty Acid)

2. Linoleic Acid (Omega-6 FA)
Linolenic acid is aka what? Why?

Linoleic acid is aka what?
Linolenic is one of many Omega-3 FAs. The first dbl bd is on the 3rd C from the methyl end.

Linoleic is an omega-6
FA. The first dbl bd is on the 6th C from the methyl end.
What is the concern with the Omega-3 fatty acids?
The population does not get enough of these in their diet.
Omega-3 and Omega-6 are both known as ? ? ?. Why?
Essential Fatty Acids. Because the must be consumed in our diet. We can not synthesize them.
Give 2 examples of fats that are composed of mostly saturated fatty acids.
1. Animal Fats

2. Tropical oils
Give 3 examples of fats that are composed of mostly monounsaturated fatty acids?
1. vegetable oils

2. olive oil

3. canola oil
Give an example of fats that are rich in polyunsaturated fatty acids?
Many vegetable oils
Unsaturated FAs are more ? but less ? than saturated FAs.
Unsat. are more healthy but less stable.
What causes Fatty Acids to become rancid?
They oxidize (they lose electrons).
Name 3 possible ways that Unsaturated fatty acids may be protected from oxidation?
1. Air-tight seals

2. Antioxidants

3. Hydrogenation
Give 4 examples of antioxidants?
1. BHA

2. BHT

3. Vit. C

4. Vit. E
What does BHA and BHT stand for?
BHA = Butylated Hydroxyanisole

BHT = Butylated Hydroxytoluene
What is hydrogenation?
It is a way of protecting unsaturated FAs from oxidation that involves adding hydrogen. However, it rids the FA of it's double bonds. This causes it to become a saturated FA.
What makes hydrogenation possible?
The double bonds of unsaturated fats carry a slightly negative charge and readily accept positively charged hydrogen atoms, creating saturated FAs.
What is an example of a product that commonly undergoes hydrogenation by producers?
Peanut butter. The natural variety with oil on top is unsaturated and much healthier for you.
What are the 3 goals of hydrogenation?
1. Protects

2. Solidifies

3. Saturates
What happens if only PARTIAL hydrogenation occurs?
It results in some CIS double bonds becoming TRANS double bonds. This is typically unintended. It results in TRANS fatty acids.
Most naturally ocurring unsaturated fatty acids are in what conformation?
They are cis.
Why are Trans-fatty acids even more unhealthy than saturated fats?
They lead to inflammation in the arteries. They are trans and linear; unlike there cis counterparts. They also have a higher melting point and are solid at both room and body temperature.
Do Trans-fats ever occur naturally?
Yes. But generally they are artificial.
Why is their a reluctance in reducing trans-fats in the food industry?
Their is reluctance because it is expensive to carry out.
Phospholipids are lipids so they are mostly ? but the pospho- part is ?.
Mostly hydrophobic but the phospho part is hydrophilic.
Phopholipids are components of all ? ?.
They are components of all cell membranes.
In foods, phospholipids acts as good ?. Give an example.
Phospholipids are good emulsifiers. An example of this is mayonnaise which is a hydrophilic and hydrophobic compound.
What is one of the best known phospholipids?
List 3 advantages of using Triacylglycerols as storage fuels.
1. High energy density (J/g),(9kcal/g)

2. Not water-soluble (compared to carbohydrates)

3. Chemically somewhat inert.
Triacylglycerols are not water soluble (when compared to carbohydrates). This means they do not do what two things?
1. They do not increase osmotic pressure.

2. They do not bind water (so their is no extra mass).
List 3 problems with using TAGs as fuels?
1. Need to be emulsified to be transported into cells of the body.

2. Need special protein carriers that have hydrophilic and hydrophobic parts

3. "Inert" bonds are hard to break.
Getting energy from TAG/FA catabolism involves ?. This produces the product ?.
It involves Beta oxidation. It produces Acetyl CoA.
What is the simples case of Beta oxidation?
The simplest case is that of FULLY-SATURATED FAs with an EVEN number of carbon atoms. Hopefully, we do not eat a lot of these.
What do special cases of Beta oxidation involve?
They involve UNSATURATED FAs or an ODD-NUMBER of carbon atoms.
Acetyl CoA ordinarily enters the CAC. However, when it can't what does it form?
When it can't enter the CAC it forms KETONE BODIES. The body can handle these in small amounts.
What are 3 general sources of FAs?
1. Diet

2. Storage

3. Synthesis
What is important in the digestive tract concerning incoming dietary lipids?
Bile is important and is involved in the digesting of foods with FAs.
What are TAGs broken down to in the body?
They are broken down into FAs.
What are important in breaking TAGs to FAs?
Lipases are important for breaking TAGs to FAs.
Concerning the digesting of food with FAs what occurs in the intestine?
1. Emulsification by bile. Bile is important for the processing of FAs.

2. The hydrolysis of TAGs to FAs by lipases.
Concerning incoming dietary lipids what occurs in the intestinal walls?
1. FAs become TAGs

2. Incorporated into chylomicrons
Concerning incoming dietary lipids: How are they transported?
1. Lymph system

2. Blood system
What occurs in the muscle and adipose tissue concerning incoming dietary lipids?
1. TAGs broken down to FAs by lipases.

2. FAs enter into cells.

3. Oxidation and storage occurs (TAG)
What are Bile acids synthesized from?
They are salts synthesized from cholesterol.
What does fiber do to bile?
Fiber absorbs and removes bile from the digestive tract.
What happens when bile is removed from the digestive tract?
When bile is removed, more bile is synthesized from cholesterol.
When fiber absorb and removes bile what does it lower?
It lowers blood [cholesterol].
List the 5 general steps that TAGs follow from storage in adipose tissue until it gets to the tissue where it is needed?
1. TAGs from storage in adipose tissue.

2. Low energy (ex. haven't had a meal)

3. Hormones (Involves epinephrine(fight or flight), glucagon)

4. TAG hydrolysis breaks down to FA and transported to tissues that need the energy. The carrier is serum albumin.

5. FA catabolism occurs.
In the cell FAs first go to what?
FAs go to Fatty Acyl-CoA
How is the rxn of FA going to Acyl-CoA driven forward?
A lot of energy is put in and drives the rxn forward. This is an exergonic process. The result is energy stored in the bonds of Fatty Acyl-CoA.
What is Fatty Acyl-CoA aka as?
When an Adenyl group attaches to FA what does it cause the release of?
An Adenyl group attaches to an FA and causes the release of pyrophosphate. This also releases a lot of energy, even more than ATP-->ADP + Pi
What is the net energy released in the rxn of Fatty Acid to Acyl-CoA?
-15kJ/mol is the net energy released. (Remember we had put about 60kJ into the process)
What does ACS stand for?
It stands for acyl-CoA synthase (family).
Where is Acyl-CoA generated?
It is generated in the cytosol.
Explain the process that brings the FA into the mitochondria.
1. Acyl-CoA is in cytosol.

2. It then binds to CARNITINE.

3. Once it is bound to carnitine it can pass between 2 spaces of the mitochondria.

4. Once inside, the carnitine is replaced with CoA.

5. Carnitine moves back outside of membrane.
What is the ^G'" for the rxn that transports FA into the mitochondria?
^G'" = -34kJ/mol
To move FA into the mitochondria what is absolutely required?
CARNITINE is absolutely required. Most people have sufficient quantities of this in their bodies.
Once carnitine is replaced in the rxn that brings FA into the mitochondria what happens to it?
It is recycled. There is no net loss. It is regenerated and ends up back outside of the mitochondria.
What ATP equivalents are used in the process that brings FA into the mitochondria?
2 ATP. This is for the initial change of the FA. The carnitine cycle doesn't use much otherwise.
Generally, when Fatty acids are oxidized inside the mitochondria, how many Carbons do we remove at a time?
We generally remove 2 carbons at a time.
What do you end up with after the oxidation of Fatty acid in the mitochondria?
You end up with 8 Acetyl CoA, NADH, and FADH2.
Explain where the energy molecules are involved in the Beta-oxidation of Fatty Acids?
1. 2 hydrogens are removed from the FA. You get 1 molecule of FADH2.

2. Then H2O is added.

3. Then 2 more Hydrogens are removed. You get 1 molecule of NADH.

4. Then the molecule is cleaved and CoA is added.

5. In the end the FA has two less Carbons. These carbons are now on the product, Acetyl CoA.

BOTTOM LINE: You get an FADH2, an NADH, and an Acetyl CoA.
How many repeated cycles of beta-oxidation of Fatty acids do we go through?
We go through seven cycles.
How many Acetyl-CoA molecules do we end up with after the multiple cycles of beta oxidation of a fatty acid?
It depends on how many Carbons were in the original Fatty acid reactant. If the FA has n number of carbons there will be n/2 Acetyl-CoA produced. For example, a 16 C FA would yield 8 Acetyl-CoA.
How many molecules of FADH2 and NADH do you end up with after multiple cycles of FA oxidation?
It depends on how many Carbons the original FA had. If the FA had n number of Carbons then FADH2 and NADH will have (n/2)-1 carbons. For example, a 16 carbon FA will yield 7 NADH and 7 FADH2.
Approximately how many ATP equivalents is one molecule of FADH2 equal to?
Approximately 1.5 ATP equivalents.
Approximately how many ATP equivalents is one molecule of NADH equal to?
Approximately 2.5 ATP equivalents.
Every Acetyl-CoA that enters into the CAC yields what?
Each Acetyl-CoA yields 3 NADH, 1 FADH2, and 1 GTP or ATP. When added up this means that every Acetyl-CoA yields about 10 ATP equivalents. For example, 8 Acetyl-CoA yields about 80 ATP equivalents.
Palmitoyl-CoA is a 16 Carbon FA. How many ATP equivalents will it ultimately yield? Explain.
After seven cycles of oxidation it will yield 8 Acetyl-CoA (because 16/2), 7 FADH2 and 7 NADH (because (16/2)-1). The FADH2 yields approximately 1.5 ATPs apiece and the NADH yield approximately 2.5 ATPs apiece. So this comes out to 28 ATP equivalents from them.

The 8 Acetyl-CoA will then go on to the CAC where it will yield 3 NADH, 1 FADH2 and 1 GTP or ATP apiece. When the math is done this comes out to about 10 ATP equivalents for each Acetyl CoA for a total of 80 ATP equivalents.

When the 28 from the FADH2 and NADH are added up to the 80 from the CAC you end up with 108 ATP equivalents from a 16 carbon FA.
Palmitoyl-CoA catabolism from beta-oxidation yields 108 ATP equivalents. What happens if you begin with Palmitate?
It has to be activated to form Palmitoyl-CoA. This requires 2 ATP equivalents. This results in a net of 106 ATP. (NOTE: no matter how many Carbons you have in the FA being catabolized if he ask for the NET you only have to subtract 2 C.)
Approximately what percentage of actual energy is recovered from fatty acid catabolism in real-life situations where the molar concentration is not 1.
About 60% of the energy is usable. This makes it a pretty efficient process.
All the previous cards discussing FA catabolism were discussing saturated or unsaturated FAs?
They involved saturated FAs.
Most naturally-occurring unsaturated FAs have ? ? bonds?
Most have cis double bonds.
Do we synthesize Trans-FAs in our body?
Yes, for a moment during beta-oxidation.
In monounsaturated FA catabolism what do we convert the naturally occuring cis double bond into? What is required to achieve this?
We convert it to a Trans-FA double bond. Isomerase is required in this step.
What is the consequence of monounsaturated FA beta-oxidation?
If there is one cis-double bond at one of the beta-oxidation cycles then you will not get FADH2 for that cycle. This would reduce the energy yield by 1 FADH2.
What is required in the oxidation of a polyunsaturated FA?
Isomerase and reductase are required.
What is the consequence of the oxidation of a polyunsaturated FA?
Generally, for each double bond, the cycle of beta-oxidation involving that bond yields (net) one less NADH or one less FADH2 than the standard 1+1. This is the result of either one not being synthesized or the requirement of energy input.
What would be the result of the oxidation of a polyunsaturated FA with 18-carbons and 2 double bonds?
There would be 9 Acetyl-CoA (because 18/2). There would be 7 FADH2, not 8, (because (18/2)-1-1). There would also be only 7 NADH equivalents for the same reason.
What occurs in the beta-oxidation process of a FA with an odd number of carbon atoms?
Standard FA beta-oxidation proceeds until PROPIONYL-CoA remains. Then a carboxyl group is added to the propionyl-CoA through the aid of bicarbonate, biotin, and ATP. It is then epimerized and ultimately rearranged to for Succinyl-CoA (aka Coenzyme B-12).
What is vitamin B-12 made by?
It is only made by microorganisms.
Where does the primary regulation of FA oxidation take place? Why?
It primarily takes place at the ENTRY OF THE FAs INTO THE MITOCHONDRIA. This is an exergonic and rate-limiting step. This occurs because once the FAs are inside the mitochondria, metabolism generally moves ahead full speed.
In FA oxidation what occurs if FAs are prevented from entering the mitochondria?
They are converted to TAGs or phospholipids.
FAs are not simultaneously ? and ?.
FAs are not simultaneously SYNTHESIZED and DEGRADED.
What occurs if the liver has stored all the glycogen it can hold and is amply supplied with glucose?
The glucose is metabolized into FAs.
When the liver is amply supplied with glucose and it is metabolized into FAs what is the first intermediate in the process? What is it's purpose?
The first intermediate is MALONYL-CoA. This inhibits the transfer of the FAs into the mitochondria. So, to be specific, it inhibits carnitine acyltransferase I. This involved in the second step of this three step process.
In the process where glucose is metabolized into FAs, what occurs after the first intermediate, malonyl-CoA, inhibits the transfer of the FAs into the mitochondria? What does this cause?
The FAs are then stored as TAG or p-lipids. This is why/how carbohydrates are converted to and stored as fat.
Malonyl-CoA is an intermediate involved in the regulation of FA oxidation. Name two other allosteric regulators of the FA oxidation process?
Reaction #3 is inhibited by a high concentration of [NADH]/[NAD+].

Reaction #4 is inhibited by it's product, Acetyl-CoA.
What is the most common genetic defect affecting FA catabolism in the U.S.?
The most common is in MEDIUM-CHAIN ACYL-CoA DEHYDROGENASE (MCAD) GENE. This results in an inability to oxidize certain (6-12 carbons) FAs. So fat accumulates in the liver. This is a major health problem for those affected. Tweny-five to 60% mortality among the 1 in 10,000 affected.
Where does the omega oxidation of FAs take place?
It takes place in the ER of liver and kidney cells.
In mammals, Acetyl-CoA from FA oxidation in the liver can do either one of what two things?
The acetyl-CoA can either enter the CAC or be converted into ketone bodies.
What is the result of ketone body formation?
It forms acetone in small amounts. However, it is toxic and volatile. So, KBs are toxic and volatile AND they are a source of fuel (energy, such as beta-hydroxybutyrate and acetoacetate).
When would acetyl-CoA enter into KB formation instead of the CAC?
When glucose is in short supply and the intermediates of CAC are being used for gluconeogenesis.
What are ketone bodies useful for?
They serve as alternative sources of fuel for extra-hepatic tissue. They also free up CoA so that beta oxidation can continue.
Name two situations that can lead to the formation of KBs?
1. Severe Starvation, or possibly the Atkins diet.

2. Untreated Diabetes.
Explain how severe starvation, or the atkins diet, can lead to KB formation?
It induces gluconeogenesis.
Explain how untreated diabetes may lead to KB formation?
With untreated diabetes (inadequate glucose uptake), there is a lack of malonyl-CoA formed. So there is no FA synthesis. So FAs enter into the mitochondria. In the mitochondria they are degraded to Acetyl-CoA. However, the Acetyl-CoA cannot enter the CAC because of active gluconeogenesis so it is metabolized into KBs.
List the 7 steps of how untreated diabetes leads to KB formation.
1. Untreated diabetes leads to glucose in cells.

2. There is little FA synthesis.

3. There is little malonyl-CoA formed.

4. FAs enter the mitochondria.

5. FAs degraded to Acetyl-CoA.

6. Acetyl-CoA cannot enter the CAC because there is a low supply of intermediates (they are in gluconeogenesis).

7. Acetyl-CoA is metabolized into KBs.
What is acidosis?
It is related to the formation of KBs. When increased blood levels of acetoacetate and hydroxybutyrate lower the pH. Extreme acidosis leads to coma and death.
What is ketosis?
When KBs in the blood and urine of untreated diabetics reach extremely high levels.
What is the term for a condition when a patient has increased blood levels of acetoacetate and hydroxybutyrate AND KBs in the blood and urine reach extremely high levels.
It is a combination of acidosis and ketosis: ketoacidosis.