Lipids and metabolism Flashcards
what intensity does fat oxidation max occure?
65% and fat oxidation in grams per minute is around 0.60 grams
what happens to fat oxidation when exercise intensity increase?
it decreases quickly
what happens to fat and carbs metabolism as exercise time increases?
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%
what are the functions of Lipids?
Energy store (9kcal/g) Plasma membrane (phospholipids)
Insulation (subcutaneous fat) Hormone synthesis (Testosterone, Progesterone)
Protection (surrounding vital organs) Nutrient Absorption (fat soluble vitamins)
classification of Lipids
simple: fats and waxes
compound(lipids with something else):
lipoproteins
phospholipids
glycolipids
Derived: steroids and others
why is storing carbs not efficient?
Although important, stores of carbohydrate in the liver and skeletal muscles are somewhat limited. We have to store water with carbohydrate – not efficient!
why are stores of triglycerides important?
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.
where is the energy stored in compounds?
Hydrogen atoms
what is lipolysis?
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.
what happens to lipolysis after a meal?
it is suppressed because insulin is released and inhibits it by using carbs
what makes something saturated and unsaturated?
Palmitic acid has no double bonds so is a saturated fatty acid
Linoleic acid has two double bonds so is a polyunsaturated fatty acid
Transport of fat to muscle tissue: free fatty acids is carried by what?
Fatty acids released by adipose tissue pass out of the adipocyte into the bloodstream. They are carried through the bloodstream bound to albumin molecules.
Transport of fat to muscle tissue: what happens when free fatty acids get to the muscle cells
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).
Transport of fat to muscle tissue: where does metabolism of free fatty acids take place?
Metabolism of fatty acids takes place in the mitochondria. They are transported across the mitochondrial membrane by carnitine palmitoyl transferase (CPT1).
in beta oxidation what happens to the hydrogen atoms that are broken off?
Transporters:
NAD+=NADH
FAD=FADH
what is O2 in oxidation?
used as the final point, produces O2
what is beta oxidation of Fatty acid?
. 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…
when will Beta oxidation stop?
until 2 carbon units remain
beta oxidation of Fatty acids: what happens to Acyl-CoA? part 1
Acyl-CoA is first dehydrated & oxidized to trans-2-Enoyl CoA (NADPH) & in the process FAD is converted to FADH2
beta oxidation of Fatty acids: what happens to Acyl-CoA? part 2
Next, the NADPH is converted to L-3-Hydroxyacyl CoA in a hydration reaction (water is added).
beta oxidation of Fatty acids: what happens to Acyl-CoA? part 3
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 +).
beta oxidation of Fatty acids: what happens to Acyl-CoA? part 4
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.
what are the end products of beta-oxidation for “cycle”?
The end products of β-oxidation for ‘cycle’ are; one NADH+, one FADH2, & one Acetyl CoA.
what are the end products of beta-oxidation of a 16 carbon fatty acid molecule?
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
formation of Ketones:
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.
diagram of fatty acids into ketones
Fatty acids—acetyl-CoA—-Ketones (acetoacetate, beta-hydroxybutyrate) as well as TCA Cycle.
what is the role of lipoproteins?
The role of lipoprotein particles is to transport all hydrophobic fat molecules, such as triglycerides, phospholipids and cholesterol to target tissues within the body.
what makes up HDL?
majority Apolipoproteins, free cholesterol and phospholipid and the minority of triglycerides.
what makes up LDL?
majority Apolipoproteins, free cholesterol and phospholipid and the minority of triglycerides, but more free cholesterol than HDL.
what makes up IDL?
4 quarters of Apolipoproteins, free cholesterol, phospholipid and triglycerides.
what makes up VLDL?
3 quarters of Apolipoproteins, free cholesterol and phospholipid and half triglycerides.
what makes up Chylomicrons?
majority Triglycerides and a minority of Apolipoproteins (extremely low), free cholesterol and phospholipid
cholesterol: what is it?
All animal cells manufacture cholesterol thus contain cholesterol in varying amounts
Some foods (mostly plants) contain phytosterols which compete with cholesterol for absorption
what are some derived lipids-Steroid Hormones
Cholesterol, Progesterone, Aldosterone, Testosterone, Estradiol, Cortisol
what is the process of Steroid Hormones? part 1
Lipid-soluble hormone diffuses through plasma membrane
what is the process of Steroid Hormones? part 2
Hormone binds with receptor in cytoplasm, forming a receptor-hormone complex
what is the process of Steroid Hormones? part 3
Receptor-hormone complex enters the nucleus and triggers gene transcription
what is the process of Steroid Hormones? part 4
Transcription mRNA is translated into proteins that alter cell activity
summary:
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.
