5 Main Types of Lipids
1 - Fatty Acids
2 - Triacyglycerols / Triglycerides
3 - Steroids
4 - Glycerophospholipids
5 - Sphingolipids
Define the major chemical properties of lipids (4)
1. They have long hydrophobic hydrocarbon chains attached to carboxylic acids
2. Even number of Carbon Atoms
3. Saturated (no double bonds) or Unsaturated (1 ore more double bonds
4. Fatty Acyl Chain = rich source of energy *
2 Essential Fatty Acids
1. Linoleic (Omega-6) → PRO inflammatory in that it makes molecules in inflammatory processes, abundant in vegetable oil
2. LinoLENIC (Omega - 3) → ANTI- inflammatory and cardio protective, abundant in fish oils and flax seeds
1. List different substrates for Fatty Acid Synthesis
2. Where does it mostly occur?
1. Carbs, Proteins and Acetyl CoA
**Synthesis is also under the control of Insulin and Glucagon
2. Cytoplasm of Hepatocytes
1- Describe the process by which more Acetyl CoA is made to make more lipids.
2- Successive FA synthesis reactions occur to eventually form ___________.
1 - Acetyl CoA made in the mitochondrial matrix is exported to the cytoplasm and covered to Malonyl coA which is used fatty acid or sterol biosynthesis.
2 - Palmitic Acid
Functions of Fatty Acids (4)
1. Building blocks for Phospholipids and Glycolipids which make up the cell membrane?
2. Added to proteins to make → lipoproteins (FA become water soluble)
3. Serves as a fuel molecule
4. Hormones or 2nd messengers
1. In what form are lipids usually ingested in our diet?
2. What enzyme breaks this lipid down? What are the products?
1. Triglycerides or TAGs
2. Enzyme → Lipase
Products → FA and Glycerol
List the substrate sources of triacylglycerol synthesis in the intestine and liver.
Intestine → DIETARY FAT
Liver → Excess Carbs (Glycogen) and AA
Define how fatty acids are stored in adipose tissue.
They are stored as Triacylglycerol (TAG) or Triglycerides
1- Explain the major pathways of fatty acid oxidation.
2- What are the organs involved?
1. Triacylglyceros is first broken down to glycerol and 3 fatty acids. These fatty acid then enters β-oxidation where 2 C units (Acetyl CoA) are removed at a time. Acetyl coA then enters the Kreb Cycle to produce a high yield of ATP.
2 - Liver and Muscle
What are the products formed in 1) the β-Oxidation pathway and 2) Krebs cycle?
1) β-Oxidation Pathway → Acetyl CoA, FADH, NADH
2) Krebs Cycle → NADH, FADH, ATP
List the physiologic ketone bodies (3)
1 - Acetoacetate
2 - β−Hydroxybutyrate
3 - Acetone
Why do we make Ketone Bodies? (2)
1 - For Energy during starvation
2 - It is water soluble so it can be used in other parts of the body when needed
Describe the basic process of Ketone Body synthesis
Ketone bodies are synthesized in the liver mitochondria from acetyl CoA derived from β-Oxidation
Describe the major pathway taken by ketone bodies to produce ATP
Ketone Bodies are converted to Acetyl CoA which then enters the Krebs cycle to produce more ATP
List the main anatomic structures that can utilize ketone bodies as an energy source (3)
2 - Heart Muscle
3 - Skeletal Muscle
List 3 clinical processes that can lead to ketoacidosis
1 - Starvation
2 - Excessive Fasting
3 - Diabetes Mellitus
_________ are a large category of chemicals that hare a common molecular backbone and include hormones, bile salts and cholesterol
1. What is Cholesterol an essential component of? (2)
Cell membranes and Lipoproteins
List sources of cholesterol - Endogenous sources and Exogenous sources
Endogenous → Liver, intestine, adrenal gland, testes and ovaries (1g/day)
Exogenous → Diet (300 mg/day)
Identify the key substrate involved in cholesterol synthesis, and the major rate limiting enzyme
Key Substrate → Acetyl CoA
Limiting Enzyme → HMG-CoA reductase (target of statin drugs)
True or False - Intake of Dietary Cholesterol can inhibit de novo synthesis
True. BUT limiting dietary cholesterol decreases blood cholesterol levels by only as much as 10%
1 - Define Lipoprotein
2- Describe their structure
1 - Lipoproteins transport cholesterol and other lipids in the blood.
2 - They are made up of Proteins and Lipids and are characterized by their density
What is the function of Chylomicron?
1 - It is an example of a lipoprotein made in the liver, which transports TAG from intestine to tissues.
What is the difference between VLDL (Very Low Density Lipoproteins) and LDL?
VLDL transports liver TAG
LDL transports liver CHOLESTEROL to peripheral tissue
What is the function of HDL?
HDL takes excess cholesterol back to the liver for disposal
List other cholesterol functions (2)
1. It is a vitamin D precursor
2. Bile acids are made by Cholesterol in the Liver
Function of Bile Acids (2)
1. Fxn as strong detergents - helps to emulsify cholesterol and other lipids within intestine
2. Involved in the major pathway of elimination for body's cholesterol and derivatives
98% of Bile acids are reabsorbed & returned to the liver via the ____________
Unabsorbed cholesterol and bile acids are converted to fecal sterols by __________
1 - _______ is another type of FA which is a main component of the cell membrane (lipid bilayer)
2 - _______ are enzymes that breakdown pieces of cell membrane for another use
1 - Glycerophospholipids
2 - Phospholipases
________ are a 2nd main component of cell membranes - often cell surface markers and are abundant in the CNS
Sphingolipids (Don't have to know for exam)