Ch 17 Lipids/Fatty Acids Flashcards
What is the primary metabolic similarity between Ruby-throated Hummingbirds, elite marathon racers, and hibernating bears?
They all rely on β-oxidation of fatty acids for energy.
What happens to fat during winter for bears?
Fat is oxidized to produce heat via electron transport uncoupled from ATP synthesis.
What is the main storage form of fat?
Triacylglycerols.
What are the four major functions of lipids in humans?
- Structural components of biological membranes
- Energy reserves
- Vitamins
- Hormones
What are the different types of lipoproteins and their primary functions?
- Chylomicrons: transport dietary lipids
- VLDL: transport endogenous lipids
- IDL: transitional form between VLDL and LDL
- LDL: transport cholesterol to tissues
- HDL: transport cholesterol from tissues back to the liver
True or False: All individuals have plaques in their arteries from their teenage years.
True.
What is the role of lipases in lipid metabolism?
They catalyze the release of fatty acids from triacylglycerols.
What initiates the catabolism of fatty acids?
Fatty acids are oxidized via β-oxidation to produce acetyl-CoA.
Where does β-oxidation of fatty acids occur?
In the mitochondria.
What is produced in each cycle of β-oxidation?
- 1 Acetyl-CoA
- 1 NADH
- 1 FADH2
How many ATPs does the oxidation of stearic acid (18 carbon) yield?
120 ATPs.
What is one reason unsaturated fatty acids yield less free energy than saturated fatty acids?
Unsaturated fatty acids contain double bonds that reduce the amount of energy produced during oxidation.
What happens to acetyl-CoA if carbohydrates are not consumed?
Acetyl-CoA accumulates as it cannot enter the citric acid cycle without oxaloacetate.
What are ketone bodies and where are they produced?
Acetoacetate, acetone, and β-hydroxybutyrate; produced in the liver.
What is the condition called when there is excessive production of ketone bodies?
Ketosis.
What is ketoacidosis?
A condition caused by excess acetoacetate and β-hydroxybutyrate lowering blood pH.
Fill in the blank: Fatty acids are liberated from glycerol to be oxidized to provide _______.
energy.
What is the process by which fatty acids cross the inner mitochondrial membrane?
Carnitine shuttle system.
What is the end product of β-oxidation of a 16-carbon fatty acid like palmitate?
Eight molecules of acetyl-CoA.
What is the role of cyclic AMP in lipid metabolism?
It initiates a kinase cascade that activates lipases.
What is the relationship between lipid metabolism and energy yield from fats compared to carbohydrates?
Oxidation of fats yields more energy due to a greater number of C-H bonds.
What is the effect of prolonged fasting on oxaloacetate levels?
Oxaloacetate is consumed to produce glucose, leading to acetyl-CoA accumulation.
What is the primary function of HDL?
Transport cholesterol from tissues back to the liver.
What is the significance of β-oxidation for energy production?
It generates acetyl-CoA, NADH, and FADH2, which are key for ATP production.
Where does fatty acid synthesis occur in the cell?
In the cytoplasm
What is the first step in fatty acid synthesis?
The export of acetyl-CoA from the matrix to the cytoplasm via a citrate intermediate
What is the main precursor for fatty acid synthesis?
Malonyl-CoA
What catalyzes the formation of malonyl-CoA from acetyl-CoA?
Acetyl-CoA carboxylase (ACCase) complex
What are the requirements for the acetyl-CoA carboxylase reaction?
- Biotin
- Mn2+
- ATP
What is the significance of carboxylating an acetyl group to a malonyl group?
It is necessary for the synthesis of fatty acids
What does ACP stand for in fatty acid synthesis?
Acyl Carrier Protein
What does the condensation reaction in fatty acid synthesis involve?
Favorable decarboxylation and release of CO2
What is reduced by NADPH during fatty acid synthesis?
Subsequent steps in the fatty acid synthesis cycle
What is the role of the second cycle of fatty acid synthesis?
Plays the same role as acetyl-ACP in the first cycle
What are the enzymes involved in palmitate synthesis?
- AT: Acetyl Transferase
- KS: Ketoacyl ACP Synthase
- KR: Ketoacyl ACP Reductase
- HD: Hydroxyacyl ACP Dehydratase
- ER: Enoyl ACP Reductase
Where does the synthesis of triacylglycerols and phospholipids occur?
In the endoplasmic reticulum of liver or fat cells
What is the main point of regulatory control in fatty acid metabolism?
ACCase
What reaction is catalyzed by glycerol-3-phosphate dehydrogenase?
Conversion of dihydroxyacetone phosphate to glycerol-3-phosphate
What is the initial step in cholesterol synthesis?
Condensation of isoprene units
What is the total number of reactions required to convert squalene to cholesterol?
21 reactions
What is the physiological effect of statins?
Lower serum cholesterol levels by blocking mevalonate synthesis
What is the role of HMG-CoA reductase in cholesterol biosynthesis?
Catalyzes the committed, highly regulated step
What are the fates of newly synthesized cholesterol?
- Stored as an ester
- Used in membrane synthesis
- Converted to steroid hormones
What is correlated with the development of heart disease?
High levels of LDL and low levels of HDL
What effect does regular strenuous exercise have on HDL levels?
Increases HDL levels and decreases the probability of heart disease
What do steroid hormones influence?
- Inflammation reactions
- Carbohydrate, protein, and lipid metabolism
- Excretion of salt and water by the kidneys
- Development of secondary sexual characteristics
What is the SREBP regulatory system responsible for?
Coordinating cholesterol production and transport among tissues
Fill in the blank: The synthesis of phosphatidylserine is a _______ reaction.
head-group exchange
True or False: Free fatty acids exist in large quantities in the cell.
False
