Human Nutrition Flashcards

Flashcards based on Dr. Ceddia's lecture notes on human nutrition, covering topics such as fiber, lipids, fatty acids, cholesterol, digestion, absorption, and protein metabolism.

What is the generic daily fiber recommendation for adults?

25 g to 40 g

Name four food categories that can help meet daily fiber recommendations.

Whole-grain products, vegetables, fruits, and legumes

List four main types of lipids found in foods.

Fatty acids, triglycerides (TG), phospholipids, and sterols

What percentage of daily energy intake should be provided by lipids, according to Health Canada?

20 to 35%

Where is cholesterol found?

Only in animal foods

What are the three classifications of fatty acids, according to chain size?

Short-chain (2 to 4 carbons), medium-chain (6 to 12 carbons), and long-chain (14 to 26 carbons)

What is the difference between saturated and unsaturated fatty acids?

Saturated fatty acids lack double covalent bonds between carbons, while unsaturated fatty acids have one or more double bonds.

What does MUFA stand for?

Monounsaturated Fatty Acid

What does PUFA stand for?

Polyunsaturated Fatty Acid

What are the two systems used to identify the position of double bonds within a hydrocarbon chain?

Delta (A) and omega (w) systems

In the omega (w) system, from which end of the molecule is carbon counting initiated?

Methyl end

What two factors influence a fatty acid's solubility and melting point?

Length of fatty acid and degree of unsaturation

How does chain length affect water solubility?

Shorter fatty acids tend to be more water-soluble than longer ones.

How does the number of double bonds affect water solubility?

The greater the number of double bonds, the greater the polarity and water solubility.

What is the relationship between chain length and the melting point of fatty acids?

The greater the chain length, the higher its melting point.

What is the relationship between saturation and the melting point of fatty acids?

The more saturated a fatty acid is, the higher its melting point.

Name two essential fatty acids.

Linoleic and alpha-linolenic acids

What is the reason linoleic and alpha-linolenic acids are essential?

Humans lack the enzymes (A12 and A15 desaturases) necessary to incorporate double bonds at the required positions.

Name three health benefits associated with regular consumption of omega-3 fatty acids.

Reduced blood pressure and blood clots, reduced risks of heart disease and stroke, and improved defense against inflammatory diseases.

What is the recommendation by the Canadian Food Guide for fish consumption?

Two servings of fish per week

What are some concerns associated with omega-3 supplements?

Excessive intake, bleeding, interference with wound healing, raised LDL, and suppressed immune function

What is the chemical difference between cis- and trans- fatty acids?

Cis-fatty acids have hydrogens next to the double bond on the same side. Trans-fatty acids have them on the opposite side.

What are some health risks associated with trans-fat intake?

Increased heart disease, raised LDL, lowered HDL, increased weight gain, promotes visceral fat accumulation, and induces inflammation

What is the composition of triglycerides (TGs)?

Three fatty acids esterified to one glycerol molecule

Name three functions of triglycerides.

Energy storage, insulation, and carriers of lipid-soluble vitamins (A, D, E, and K)

What are NEFAs?

Non-esterified fatty acids, also referred to as free fatty acids.

What protein do NEFAs bind to for transport?

Albumin

What two products are yielded from the hydrolysis of triglycerides (TGs)?

Glycerol and three fatty acids

What is the function of carnitine in fatty acid oxidation?

Carrier molecule for long-chain fatty acids to pass into the mitochondrial matrix

What happens to acyl-CoA during beta-oxidation?

Fatty acids are sequentially cleaved in two-carbon units (acetyl-CoA)

What makes them ideal structural components for cellular membranes?

Phospholipids are amphiphilic molecules, meaning they attract both water- and fat-soluble substances.

What are the components of phospholipds?

Glycerol, two fatty acids, and a phosphate group (PO4)

Name four common variants of phospholipids.

Phosphatidylcholine (lecithin), phosphatidylethanolamine (cephalin), phosphatidylserine, and phosphatidylinositol

What kind of structure characterizes sterols?

A four-ring core structure (cyclopentanoperhydrophenanthrene) or steroid nucleus

What is the most common sterol in animals?

Cholesterol

Give two uses for cholesterol in liver cells.

Liver cells make about 800 to 1500 mg of cholesterol every day, contributing more to total body cholesterol than the diet itself, and they produce bile from it.

Name a therapeutic approach to treat hypercholesterolemia that involves the biliary system.

The removal of bile salts through unabsorbable resins that bind bile salts in the intestinal lumen

What is the precursor utilized to synthesize cholesterol?

Acetyl-CoA

What is the rate-limiting enzyme in cholesterol synthesis and how is it regulated?

HMG-CoA reductase. It is inhibited by cholesterol as the sterol rises in the cytoplasm.

What class of drugs is used to inhibit HMG-CoA reductase activity?

Statins

What enzyme starts the process of TG hydrolysis in the oral cavity?

Lingual lipase

What two substances are required in the intestine for most TGs to be digested?

Bile salts and pancreatic lipase

What is emulsification?

Emulsification turns fat into small droplets with greatly increased surface area for the subsequent action of pancreatic lipases.

What is the role of colipase?

Colipase binds lipase and reverses the inhibition by bile salts, ensuring adhesion of lipase to the lipid droplet.

What products are contained in the partial digestion of lipids?

2-MAGs, 1-MAGs, lysolecithin, cholesterol and free fatty acids

How are fatty acids absorbed?

Diffussion model and mediated by fatty acid transport proteins, FATPs 1-4, as well as by FAT/CD36.

What transporter protein enables free cholesterol absorption?

Nieman-Pick C1 or NPC1L1

What is the "enterohepatic circulation"?

The process by which bile salts are reabsorbed in the gut.

What is the diet-heart hypothesis?

The diet-heart hypothesis stated that saturated fats were the cause of atherosclerosis on the basis that it would elevate cholesterolemia

During cooking, which type of oils are suseptible to oxidation?

Oils that are high in PUFAs

What process has prompted great interest in understanding which lipids are transported and processed in the organism?

The fact that lipids are part of the atherogenic plaque

How do lipids travel in the bloodstream?

Lipids are transported in the bloodstream as constituents of lipoproteins, with the exception of NEFAs.

Name four lipoproteins that circulate in the blood.

VLDL, IDL, LDL, and HDL

What role to apoproteins play in lipid transport?

Apoproteins confer water solubility and regulate the activity of key enzymes in lipoprotein metabolism and also mediate particle removal.

What apoprotein do chylomicrons contain?

ApoB-48

What apoprotein do VLDL and LDL contain?

ApoB-100

What role do chylomicrons play?

To deliver dietary lipids to tissues other than the liver

What is the purpose of VLDLs?

VLDLs are responsible for delivering endogenous rather than dietary TG to peripheral tissues.

What enzyme acts to remove TG from chylomicrons, VLDL, and IDL?

Lipoprotein lipase (LPL)

What is required for LPL activation?

Apo-CII

What process occurs as TGs are cleaved and fatty acids donated to tissues that makes VLDLs transiently become IDLs?

Removal of TGs

What is the function of LDLs?

To deliver cholesterol to tissues where it may be used for membrane construction, as well as to produce steroid hormones

What is the function of HDL?

HDL removes unesterified cholesterol from cells and other lipoproteins and transports them to the liver (reverse cholesterol transport) to be excreted in the bile.

What protein is responsible for the transfer of cholesterol from cell membranes to HDL?

ABC-A1

Name a function of the PCSK9.

The PCSK9 seems to be important to regulate the abundance of LDL receptors at the cell surface and the clearance of LDL-C particles from the circulation.

Name three components that proteins contribute to.

Cell growth, repair and maintenance

What is the RDA for the intake of proteins?

0.8 g per kg of body weight per day

From where are proteins obtained?

Meats, eggs, and dairy products, although whole grains, legumes, nuts, and soy products also contain significant amounts.

What type of bond links amino acids?

Peptide bonds

Name the three phases of protein synthesis.

Initiation, elongation, and termination

What is the purpose of the hormone insulin, when pertaining to protein synthesis?

Insulin ultimately promotes the uptake and inhibits the degradation of amino acids and favors proteins synthesis.

Would increasing ones daily protein intake promote protein synthesis and muscle growth?

No, unless someone is not acquiring the daily recommended allowance of protein, simply increasing the availability of amino acids through supplementation will not by itself promote protein synthesis and muscle growth.

What is the protein RDA for vegetarian endurance athletes?

1.3 to 1.5 g/kg BW/day

Is animal protein or plant protein more effective?

There was a favoring effect of animal protein on percent lean mass.