NSC 308 Unit 2 Study Guide (Ch 6 & 7)

Fatty Acids

Long chains of carbon atoms with a methyl group (CH3) at one end (the omega end) and a carboxylic acid group (C=O with OH) at the other end.

Methyl End

CH3 (omega end).

Carboxylic Acid End

C=O with OH (carboxyl group).

Saturated Fatty Acid

No double bonds between carbons, linear structure.

Unsaturated Fatty Acid

Contains double bonds between carbons, causing a kink or bend.

Monounsaturated Fatty Acid

One double bond.

Polyunsaturated Fatty Acid

Two or more double bonds.

Triglyceride

Glycerol backbone with three fatty acids attached.

Omega-3 and Omega-6

Position of the first double bond in the fatty acid, counting from the methyl end (omega end) of the carbon chain.

Energy Storage (Fats)

Stored as triglycerides in adipose tissue.

Energy Source (Fats)

Broken down via beta oxidation.

Eicosanoid Production (Fats)

Used to produce eicosanoids.

Essential Fatty Acids (EFAs)

Linoleic Acid (LA), an omega-6 fatty acid, and Alpha-Linolenic Acid (ALA), an omega-3 fatty acid.

Phospholipids

Similar to triglycerides, with a glycerol backbone, two fatty acids attached instead of three, and a phosphate group and choline group replacing the third fatty acid.

Polar Head (Phospholipids)

Charged, water-loving.

Nonpolar Tails (Phospholipids)

Uncharged, water-fearing.

Phospholipids as Emulsifiers

Function like bile, acting as emulsifiers.

Types of Sterols

Phytosterols (plants) and cholesterol (animals).

Structure of Sterols

Ring structures and a fatty acid tail.

Functions of Cholesterol

Starting point for other compounds; structural component of cell membranes; precursor to bile acids, steroid hormones, and Vitamin D.

Structure of Triglycerides (TG)

Glycerol backbone attached to three fatty acids.

Structure of Phospholipids

Glycerol backbone attached to two fatty acids, with a phosphate group and choline group attached to the third carbon of the glycerol backbone.

Structure of Sterols (Cholesterol)

Characterized by a ring structure and a fatty acid tail.

Emulsifiers

Substances that help to mix two liquids that normally don't mix, like oil and water; have a polar (water-soluble) end and a nonpolar (fat-soluble) end.

Why Phospholipids are Emulsifiers

Polar head (phosphate and choline group) is hydrophilic (water-loving), while the nonpolar tails (fatty acids) are hydrophobic (fat-loving).

Triglyceride Digestion - Organs and Enzymes

Salivary glands produce lingual lipase (limited activity); Stomach: Gastric lipase (limited activity); Small Intestine: Pancreatic lipase (major enzyme).

End Products of Triglyceride Digestion

Fatty acids, glycerol, and monoglycerides.

Absorption of Triglycerides

Triglycerides are broken down into fatty acids and glycerol to cross the enterocyte membrane; inside the cell, they are reassembled into triglycerides and packaged into lipoproteins called chylomicrons.

Lipoproteins

Carrier molecules for fat and cholesterol in the watery environment of the body; consist of phospholipids, proteins, triglycerides, and cholesterol.

Types of Lipoproteins

Chylomicrons, VLDL, LDL, HDL.

Lipoprotein Lipase

An enzyme that breaks down triglycerides from chylomicrons and VLDL to fatty acids, which can be taken up by cells.

Function of Chylomicrons

Transport dietary fats from the intestines to the rest of the body; carries exogenous fat.

Function of VLDL

Carries triglycerides and cholesterol from the liver to cells; carries endogenous fat.

Function of LDL

Transports cholesterol to cells.

Function of HDL

Picks up cholesterol from cells and returns it to the liver; higher levels help decrease the risk of heart disease.

LDL Uptake via the Receptor Pathway

LDL binds to B-100 receptors on cells; the cell engulfs and takes in LDL completely; the cell uses the cholesterol and phospholipids.

Scavenger Pathway

Excess LDL circulates in the blood and becomes oxidized; monocytes turn into macrophages and take up oxidized LDL, forming foam cells; foam cells accumulate and die, forming plaque in arteries (atherosclerosis).

Lipoproteins and Heart Disease

High levels of LDL cholesterol contribute to the development of atherosclerosis, increasing the risk of heart attacks and strokes. HDL cholesterol is considered protective, reducing this risk.

Protein Structure

Long chain of amino acids (polypeptide chain).

Amino Acids Structure

Contain carbon, hydrogen, oxygen, and nitrogen (amine group, NH2), an acid group (carboxylic acid), and a variable side chain or R-group.

Dipeptide

Joined by a peptide bond.

Tripeptide

Joined by peptide bonds.

Polypeptide

Many amino acids joined by peptide bonds; another term for protein.

Primary Structure (Protein)

The amino acid chain.

Essential Amino Acids

Histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine.

Building Proteins (Proteogenesis)

Amino acids are used to synthesize new proteins for various structural and functional purposes.

Making Non-Protein Nitrogen-Containing Compounds

Amino acids are used to synthesize other essential nitrogen-containing compounds like epinephrine and niacin.

Making Glucose (Gluconeogenesis)

Certain amino acids can be converted into glucose to provide energy when needed.

Forming Fat (Lipogenesis)

Excess protein can be converted into fatty acids and stored as fat.

Denature a Protein

To change its structure, often unfolding it, which can be caused by factors like heat or acid.

Blood Proteins as Fluid Regulators

Blood proteins, especially albumin, help maintain fluid balance by holding fluid inside blood vessels.

Protein Digestion

Hydrochloric acid (HCl) denatures proteins and pepsin breaks peptide bonds in the stomach. Proteases are released into the small intestine to further digest these proteins. Brush border enzymes in the small intestine break down peptides into amino acids, dipeptides, and tripeptides.

Protein Absorption

Amino acids are absorbed into the bloodstream and transported to the liver.

Nitrogen Processing

The amine group (NH2) becomes ammonia (NH3) when removed. Ammonia is toxic and needs to be processed and is converted to urea by the liver, released into the bloodstream, and excreted by the kidneys in the urine.

Nitrogen Balance

Nitrogen intake versus nitrogen excretion. Protein is approximately 16% nitrogen.