Lipids and metabolism

Question 1

what intensity does fat oxidation max occure?

Answer 1

65% and fat oxidation in grams per minute is around 0.60 grams

Question 2

what happens to fat oxidation when exercise intensity increase?

Answer 2

it decreases quickly

Question 3

what happens to fat and carbs metabolism as exercise time increases?

Answer 3

fat metabolism increases with time and carbs decreases

fat starts at 49% and after 100 minutes its 60%

carbs starts with 51% and after 100 minutes its 40%

Question 4

what are the functions of Lipids?

Answer 4

Energy store (9kcal/g)
Plasma membrane (phospholipids)

Insulation (subcutaneous fat)
Hormone synthesis (Testosterone, Progesterone)

Protection (surrounding vital organs)
Nutrient Absorption (fat soluble vitamins)

Question 5

classification of Lipids

Answer 5

simple: fats and waxes

compound(lipids with something else):
lipoproteins
phospholipids
glycolipids

Derived: steroids and others

Question 6

why is storing carbs not efficient?

Answer 6

Although important, stores of carbohydrate in the liver and skeletal muscles are somewhat limited. We have to store water with carbohydrate – not efficient!

Question 7

why are stores of triglycerides important?

Answer 7

Stores of triglyceride in adipose tissue are enormous, even in the most lean of people. The energy stored in adipose tissue could sustain days and days worth of low intensity physical activity.

Question 8

where is the energy stored in compounds?

Answer 8

Hydrogen atoms

Question 9

what is lipolysis?

Answer 9

Lipolysis releases three fatty acid molecules and a glycerol molecule.

Glycerol, when released, can be metabolized by the liver for energy OR converted to glucose by a process called gluconeogenesis.

The fatty acids can be taken up by various tissues, such as skeletal muscle, and used to produce energy through a process called beta-oxidation.

Question 10

what happens to lipolysis after a meal?

Answer 10

it is suppressed because insulin is released and inhibits it by using carbs

Question 11

what makes something saturated and unsaturated?

Answer 11

Palmitic acid has no double bonds so is a saturated fatty acid

Linoleic acid has two double bonds so is a polyunsaturated fatty acid

Question 12

Transport of fat to muscle tissue: free fatty acids is carried by what?

Answer 12

Fatty acids released by adipose tissue pass out of the adipocyte into the bloodstream. They are carried through the bloodstream bound to albumin molecules.

Question 13

Transport of fat to muscle tissue: what happens when free fatty acids get to the muscle cells

Answer 13

Once they arrive at the muscle cell, they are transported across the plasma membrane and to the mitochondria by various fatty acid transporters. These include fatty acid binding protein (FABP), fatty acid transport protein (FATPO), and fatty acid translocase (FAT or CD36).

Question 14

Transport of fat to muscle tissue: where does metabolism of free fatty acids take place?

Answer 14

Metabolism of fatty acids takes place in the mitochondria. They are transported across the mitochondrial membrane by carnitine palmitoyl transferase (CPT1).

Question 15

in beta oxidation what happens to the hydrogen atoms that are broken off?

Answer 15

Transporters:
NAD+=NADH
FAD=FADH

Question 16

what is O2 in oxidation?

Answer 16

used as the final point, produces O2

Question 17

what is beta oxidation of Fatty acid?

Answer 17

. Free fatty acids → Acetyl-CoA:

-Free fatty acids: long carbon chains
. Rearrange atoms
. Release some FADH2 and NADH
. Chop off 2 carbons:
Acetyl-CoA!

• Chain is 2 carbons shorter
  . Rearrange atoms
  . Release some FADH2 and NADH
  . Etc…

Question 18

when will Beta oxidation stop?

Answer 18

until 2 carbon units remain

Question 19

beta oxidation of Fatty acids: what happens to Acyl-CoA? part 1

Answer 19

Acyl-CoA is first dehydrated & oxidized to trans-2-Enoyl CoA (NADPH) & in the process FAD is converted to FADH2

Question 20

beta oxidation of Fatty acids: what happens to Acyl-CoA? part 2

Answer 20

Next, the NADPH is converted to L-3-Hydroxyacyl CoA in a hydration reaction (water is added).

Question 21

beta oxidation of Fatty acids: what happens to Acyl-CoA? part 3

Answer 21

The L-3-Hydroxyacyl CoA is now dehydrated & oxidised to 3-Ketoacyl CoA, & the hydrogens (H+) from the water (added in the hydration) are taken up by NAD+ to produce NADH + H +).

Question 22

beta oxidation of Fatty acids: what happens to Acyl-CoA? part 4

Answer 22

Finally, the 3-Ketoacyl CoA is cleaved in a thiolytic reaction, to form a new Acyl-CoA (two carbons shorter) & an Acetyl-CoA, which can be used in the TCA/Krebs Cycle.

Question 23

what are the end products of beta-oxidation for “cycle”?

Answer 23

The end products of β-oxidation for ‘cycle’ are; one NADH+, one FADH2, & one Acetyl CoA.

Question 24

what are the end products of beta-oxidation of a 16 carbon fatty acid molecule?

Answer 24

The end products of β-oxidation of a 16 carbon fatty acid molecule are: 7 NADH (7 x 2 ATP), 7 FADH2 (7 x 2 ATP), & 8 Acetyl CoA (8 x 12 ATP).

TOTAL ATP: 131

Question 25

formation of Ketones:

Answer 25

Certain situations increase the availability of fatty acids in the blood, such as prolonged exercise, starvation, or eating a low-carbohydrate diet.

Increased availability of fatty acids can be well handled by skeletal muscles. However, the liver is not so capable of oxidising excess fatty acids.

In these situations, acetyl-CoA is diverted to the formation of ketones in the liver. The heart, brain and kidneys can oxidise ketone bodies in times of low CHO availability, but ketone accumulation results in acidosis.

Question 26

diagram of fatty acids into ketones

Answer 26

Fatty acids—acetyl-CoA—-Ketones (acetoacetate, beta-hydroxybutyrate) as well as TCA Cycle.

Question 27

what is the role of lipoproteins?

Answer 27

The role of lipoprotein particles is to transport all hydrophobic fat molecules, such as triglycerides, phospholipids and cholesterol to target tissues within the body.

Question 28

what makes up HDL?

Answer 28

majority Apolipoproteins, free cholesterol and phospholipid and the minority of triglycerides.

Question 29

what makes up LDL?

Answer 29

majority Apolipoproteins, free cholesterol and phospholipid and the minority of triglycerides, but more free cholesterol than HDL.

Question 30

what makes up IDL?

Answer 30

4 quarters of Apolipoproteins, free cholesterol, phospholipid and triglycerides.

Question 31

what makes up VLDL?

Answer 31

3 quarters of Apolipoproteins, free cholesterol and phospholipid and half triglycerides.

Question 32

what makes up Chylomicrons?

Answer 32

majority Triglycerides and a minority of Apolipoproteins (extremely low), free cholesterol and phospholipid

Question 33

cholesterol: what is it?

Answer 33

All animal cells manufacture cholesterol thus contain cholesterol in varying amounts

Some foods (mostly plants) contain phytosterols which compete with cholesterol for absorption

Question 34

what are some derived lipids-Steroid Hormones

Answer 34

Cholesterol, Progesterone, Aldosterone, Testosterone, Estradiol, Cortisol

Question 35

what is the process of Steroid Hormones? part 1

Answer 35

Lipid-soluble hormone diffuses through plasma membrane

Question 36

what is the process of Steroid Hormones? part 2

Answer 36

Hormone binds with receptor in cytoplasm, forming a receptor-hormone complex

Question 37

what is the process of Steroid Hormones? part 3

Answer 37

Receptor-hormone complex enters the nucleus and triggers gene transcription

Question 38

what is the process of Steroid Hormones? part 4

Answer 38

Transcription mRNA is translated into proteins that alter cell activity

Question 39

summary:

Answer 39

Lipids are vital energy source during the post absorptive period (fasted) and during low-moderate intensity physical activity. However, they can only used during aerobic activity and not high-intensity “anaerobic” activity.

Lipids can be classified into fats, compound lipids and derived lipids, each of which have important functions in the human body.

Lipolysis is the breakdown of triglycerides to fatty acids which can then be transported to the cell and used to create acetyl-CoA through a process called beta-oxidation.