Summary BGZ2024 Food for Life
Content
PBL Cases ................................................................................................................................................. 2
Case 1 introduction to macro- and micro nutrients. ........................................................................... 2
Case 2 digestive tract, digestion and absorption .............................................................................. 11
Case 3 transport, storage, release and oxidation of nutrients.......................................................... 31
Case 4 oxidation (in depth, process by process) ............................................................................... 49
Case 5 presentations ......................................................................................................................... 64
Case 6 biomarkers ............................................................................................................................. 69
Case 7 fat storages, fat types and link to diabetes ........................................................................... 74
Case 8 cholesterol metabolism and types of dietary fatty acids (MUFA vs PUFA) ........................... 85
Case 9 Glycemic index and load and types of sugars and the effects ............................................... 94
Case 10 Muscle synthesis and breakdown ........................................................................................ 99
Case 11 Circadian rhythms and patters........................................................................................... 102
Lectures ............................................................................................................................................... 105
Response lecture ............................................................................................................................. 105
Introduction lecture ........................................................................................................................ 108
Anatomy and physiology of the human digestive tract .................................................................. 115
Biomarkers ...................................................................................................................................... 124
Integration of carbohydrate and fat metabolism ........................................................................... 131
Basic aspects of protein metabolism............................................................................................... 140
Fat and metabolic health/Ectopic fat .............................................................................................. 148
Carbohydrates & fat & metabolic disease....................................................................................... 154
Protein, aging and chronic metabolic disease................................................................................. 161
Timing of food intake and metabolic risk ........................................................................................ 163
, PBL Cases
Case 1 introduction to macro- and micro nutrients.
Food
Nutrients water
Macronutrients micronutrients
* Carbohydrates * vitamins
* fats * minerals
* Proteins .
* alcohol .
Provide energy .
Macronutrients nutrients that deliver calories or energy/fuel to the body. The body needs these
nutrients for growth, its metabolism and other body functions. Macro means large/big, it are
nutrients that the body needs in huge amounts.
Micronutrients nutrients that the body needs in smaller amounts in order for the body to function
properly.
Nutrients have three general functions in the body
Function Nutrients description
Regulate body processes Vitamins, lipids, proteins, minerals, Body processes such as blood pressure, energy
water production and temperature
Contribute to cell and body Lipids, proteins, minerals, water Provide structure to bone, muscle and other cells
structure
Supply energy Carbohydrates, lipids, proteins Supply energy to power muscle contractions and
cellular functions.
Macronutrients
1 kcal is the amount of energy that will raise the temp of 1 kg of water
by 1°C
* carbohydrates 4.2 kcal / 1 gram of carbohydrates
* fats 9.4 Kcal / 1 gram of fats
* proteins 4.2 kcal / 1 gram of proteins.
Carbohydrates
Carbohydrates are made of carbon, hydrogen and oxygen ( C H O ) and are a major source of fuel for
the body. Dietary carbohydrates are starches and sugars found in grains, vegetables, legumes (dry
beans and peas) and fruits.
The body converts most dietary carbohydrates to glucose, a simple sugar compound. It is glucose
that can be found in the circulation, providing a source of energy for cells and tissues.
Simple carbohydrates are naturally present as simple sugars in fruits, milk and other foods.
Simple sugars are monosaccharides (glucose, fructose and galactose) or disaccharides.
,Mono-saccharides consists of a single sugar molecule. These are any sugars that aren’t broken down
during digestion and these have the general formula CnHnOn, where n = 3 – 7.
All (glucose, fructose, galactose) have 6 carbons and the chemical formula formula C6H12O6 but each
has a different arrangement of these atoms.
Glucose is the most abundant simple carbohydrate unit in nature. Glucose makes up at least one of
the two sugar molecules in every disaccharide. In the body glucose supplies energy to the cells. The
body closely regulates blood glucose (blood sugar) levels to ensure a constant fuel source for vital
body functions. It is the only fuel used by the brain (except during prolonged starvation).
Disaccharides consist of two sugar molecules chemically joined together by a glycosidic bond. This
process of chemically joining is called condensation.
These include sucrose (common table sugar), lactose (milk sugar) and maltose.
Complex carbohydrates are chains of more than two sugar molecules.
- Oligosaccharides = short chain carbohydrates containing between 3 and 10 sugar molecules
- Polysaccharides = long carbohydrate chains, can contain hundreds or thousands. 1`11
Some form straight chains whereas others branch off in all directions.
The way monosaccharides are linked makes them digestible (starch) or non-digestible (fiber).
Starch (‘’zetmeel’’) plants store energy as starch for usage during growth and reproduction.
Sources of starch are grains (wheat, rice, corn and oats), legumes (peas, beans and lentils) and tubers
(potatoes, yams and cassava).
In plants, starch takes two main forms amylose and amyloceptin.
- Amylose is made up of long unbranched chains of glucose molecules.
- Amylopectin is made up of branched chains of glucose molecules.
Amylose has lower digestibility than amylopectin, but amylopectin is more abundant in foods.
,Glycogen (‘’animal starch’’) it is the storage form of carbohydrates in living animals. It is composed
of long, highly branched chains of glucose molecules.
Fibers dietary fibers are non-digestible carbohydrates that are intact and intrinsic in plants. These
fibers go intact through our intestinal system and help to remove waste out of the body.
Characteristics of fibers
There are soluble (gums, pectins, beta-glucans, psyllium) and there are insoluble fibers
(cellulose, lignin)
Fibers have different functions
Fermentation by intestinal flora yields short-chain fatty acids
Dietary soluble fiber ensures gel forms a gel in the stomach that slows down the emptying
of the stomach and therefore slows down the glucose intake.
Lipids
Lipids refer to substances known as fat and oils but also to fatlike substances in foods such as
cholesterol and phospholipids. Lipids are generally hydrophobic (‘’water-fearing’’) and lipophilic
(‘’fat-loving’’). Lipids are organic compounds and contain carbon, hydrogen and oxygen.
Fats and oils also called triglycerides.
A triglyceride is an ester derived from glycerol and 3 fatty acids and is stored in adipose tissue by fat
cells.They are another major fuel source for the body. In addition, triglycerides, cholesterol and
phospholipids have other important functions such as providing structure for body cells, carrying the
fat-soluble vitamins (A, D, E and K) and providing starting material (cholesterol) for making many
hormones. The main classes of lipids found in foods and in the body are triglycerides, phospholipids
and sterols.
2% of dietary lipids are phospholipids, found in both plant and animal foods and made by the body.
Phospholipids are soluble in both fat and water. Only a small percentage is sterols, but the body
makes cholesterol (a form of sterol). Cholesterol is an important component of cell membranes.
The fatty acids determines the characteristic of a fat, such as whether it is solid or liquid at room
temperature. Fatty acids that aren’t joined with another compound (e.g. glycerol) are ‘free’ fatty
acids. There are many kinds of fatty acids but they are all basically chains of carbon atoms with an
organic acid / carboxyl group (-COOH) at one end and a methyl group (-CH3) at the other end.
These fatty acids differ in chain length (number of C’s in the chain).
- Short chain fatty acids have < 6 carbons.
- Medium chain fatty acids have between 6 and 10 carbons.
- Long chain fatty acids have > 12 carbons.
The shorter the carbon chain the more liquid the fatty acid (lower melting point). Shorter fatty acids
are also more water-soluble, a property that affects their absorption in the digestive tract.
The scientific naming of fatty acids: Counting from the carbon at the acid end (alpha carbon) and the
carbon at the methyl end (omega carbon).
Within a fatty acid chain each carbon has 4 bonds. When a carbon is joined to adjacent carbons with
single bonds (-C-C-C-), it still has two bonds available for other atoms (H).
- Saturated fatty acid if all the carbons in the chain are joined with single bonds and the
remaining bonds are filled with hydrogen.
- Unsaturated fatty acid if adjoining carbons are connected by a double bond (C=C), there
are fewer bonds holding the hydrogen and the chain isn’t saturated with hydrogen.
Monounsaturated fatty acid (MUFA) = a fatty acid with one double bond
Polyunsaturated fatty acid (PUFA) = a fatty acid with two or more double bonds.
,Foods never contain only unsaturated or only saturated fatty acids, it is always a mixture. Foods rich
in saturated fatty acids tend to be solid at room temp and have higher melting points.
Unsaturated fatty acids can exist in isomers cis and trans fatty acids.
The cis fatty acid’s carbon chain is bent. The trans fatty acid’s carbon chain is straighter.
The location of the double bond closest to the omega (methyl) end of the fatty acid chain identifies a
fatty acid’s family.
Omega-9-fatty acid oleic acid Oleic acid has one double bond at carbon 9 (counting from
omega end)
Omega-6-fatty acid Linoleic acid has double bonds both at carbon 6 and carbon 9. First
double bond occurs at carbon 6.
Omega-3-fatty acid Alpha-linoleic acid has a double bond at carbon 3, plus two or more
additional bonds.
Hydrogenation a chemical reaction in which hydrogen atoms are added to carbon-carbon double
bonds, converting them to single bonds. Hydrogenation of MUFA and PUFA reduces the number of
double bonds they contain, thereby making them more saturated.
Essential vs non-essential fatty acids.
The liver adds carbons in a process called elongation to build storage and structural fats. The body
also synthesizes oleic acid (omega 9 fatty acid) by removing hydrogens from carbons 9 and 10 of
saturated stearic acid thus creating a double bond at carbon 9, this process is called desaturation.
Oleic acid can be elongated further and desaturated to create other necessary fatty acids. The body
can’t produce double bonds before the 9 carbon from the methyl end.
Non-essential acids = body can make itself, omega-9.
Essential fatty acids (EFA) = fatty acids that the body can’t produce, omega-6 and omega-3.
(summary) Lipids can be divided into: saturated and unsaturated (mono and poly).
Saturated = often animal fats, have a solid shape. Don’t have a double bound.
Unsaturated = fat which is soft/liquid at room temp. Is vegetal and has a double bound.
(healthy). There are mono-unsaturated and poly-unsaturated fats
Trans fats = unhealthy unsaturated fats. It’s the hardening of fats. They act as saturated fatty
acid and are created when an otherwise naturally unsaturated fat is hydrogenated (hydrogen
atoms are added to the food). This solidifies fats that would otherwise be liquids. One of the
hydrogen atoms moves from it’s original position from cis to trans.
, Saturated fats Unsaturated fats
Type of bonds Consist of single bond Consist of at least 1 double bond
Melting point High Low
Cholesterol Increase LDL (bad cholesterol) Increase HDL (good cholesterol)
Sources Animal fats and animal products Plant and nut-based, nuts, whole-grain breads, fish.
Types / Trans fats
Mono-unsaturated fats
Poly-unsaturated fats (omega-3 and omega-6)
Triglyceride structure:
Triglycerides are major lipids in both the diet and the body. A triglyceride consists of 3 fatty acids
attached to a molecule of glycerol. Glycerol is an alcohol, a simple three-carbon molecule with an
alcohol (hydroxyl) group (-OH) at each carbon. Glycerol is the backbone of a triglyceride. A
triglyceride is an ester, a combination of an alcohol and an organic acid (e.g. fatty acid). An ester
forms when a hydrogen and an oxygen from the fatty acid’s carboxyl (acid) group combine with a
hydrogen from the alcohol’s hydroxyl (alcohol) group. This is a condensation reaction
(water is produced). An ester linkage chemically joins the altered fatty acid and alcohol, a process
called esterification.
Esterification produces triglycerides, diglycerides (2 fatty acids) and monoglycerides (1 fatty acid).
Functions of triglycerides:
Energy source fat is a rich and efficient source of calories. Under normal circumstances
dietary and stored fat supply about 60% of the body’s resting energy needs.
Fat is protein-sparing, fat is burned for energy, sparing valuable proteins for their important
roles (e.g. muscle tissue, enzymes, antibodies).
Energy reserve excess dietary fat is stored as body fat to tide us over during periods of
calorie deficit. The fat is stored inside fat cells called adipocytes which form body fat tissue.
Types of fat:
- Visceral fat fat stores that cushion body organs.
- Subcutaneous fat fat stores under the skin.
, Proteins
Proteins are organic compounds made of smaller building blocks named amino acids. Amino acids
contain nitrogen, carbon, hydrogen and oxygen. Body proteins help build and maintain body
structures and regulate body processes. Protein can also be used for energy.
Amino acids (except proline) uniformly consist of a central carbon atom chemically bonded to one
hydrogen atom (H), one carboxylic acid group (-COOH), one amino group (-NH2) and one side group
unique to each amino acid (R).
- Dispensable amino acids = AA that the body can make if supplied with adequate nitrogen.
Don’t need to be supplied in the diet.
- Conditionally indispensable amino acids = AA that are normally made in the body
(dispensable) but become indispensable under certain circumstances (e.g. critical illness.)
In the proteins from humans there are 20 different amino acids, in adults 8 of these amino acids are
not formed or are insufficiently formed (essential amino acids). These have to come in through food.
The 8 essential amino acids are: valine, osileucine, leucine, phenylalanine, threonine, tryptophan,
methionine and lysine.
The other not-essential amino acids can be formed in the liver out of other amino acids.
Amino acids link in a specific sequence to form strand of protein (peptides) up to 100’s of amino
acids long. A peptide-bond links amino acids into a protein. To form a peptide bond, the carboxyl (-
COOH) group of one amino acids bonds to the amino (-NH) group of another. In this process water
(H2O) is released.
Oligopeptide = chain of 4 to 10 amino acids
Polypeptide = chain of more than 10 amino acids.
Complete protein contains all the essential amino acids.
Incomplete protein = contains a few of the essential amino acids. Lack
one or more essential.
Functions of body proteins:
The human body contains 1000’s of different proteins, each with a specific function determined by
its unique shape.
Function Description
Catalyst Enzymes, these speed up chemical reactions.
Transport Transports many key substances such as oxygen, vitamins and minerals to target cells
throughout the body
Structure structures such as bone, skin and hair owe their physical properties to unique proteins.
(e.g. Collagen). Hair and nails are made of keratin.
Mobility Sperm cell movement
Immunity Antibodies made of protein protect us from foreign substances
Maintaining of fluid balance By pumping molecules across cell membranes and attracting water
Maintaining of acid and base By taking up or giving off hydrogen ions as needed
balance
Communication Hormones, a kind of chemical messengers
Content
PBL Cases ................................................................................................................................................. 2
Case 1 introduction to macro- and micro nutrients. ........................................................................... 2
Case 2 digestive tract, digestion and absorption .............................................................................. 11
Case 3 transport, storage, release and oxidation of nutrients.......................................................... 31
Case 4 oxidation (in depth, process by process) ............................................................................... 49
Case 5 presentations ......................................................................................................................... 64
Case 6 biomarkers ............................................................................................................................. 69
Case 7 fat storages, fat types and link to diabetes ........................................................................... 74
Case 8 cholesterol metabolism and types of dietary fatty acids (MUFA vs PUFA) ........................... 85
Case 9 Glycemic index and load and types of sugars and the effects ............................................... 94
Case 10 Muscle synthesis and breakdown ........................................................................................ 99
Case 11 Circadian rhythms and patters........................................................................................... 102
Lectures ............................................................................................................................................... 105
Response lecture ............................................................................................................................. 105
Introduction lecture ........................................................................................................................ 108
Anatomy and physiology of the human digestive tract .................................................................. 115
Biomarkers ...................................................................................................................................... 124
Integration of carbohydrate and fat metabolism ........................................................................... 131
Basic aspects of protein metabolism............................................................................................... 140
Fat and metabolic health/Ectopic fat .............................................................................................. 148
Carbohydrates & fat & metabolic disease....................................................................................... 154
Protein, aging and chronic metabolic disease................................................................................. 161
Timing of food intake and metabolic risk ........................................................................................ 163
, PBL Cases
Case 1 introduction to macro- and micro nutrients.
Food
Nutrients water
Macronutrients micronutrients
* Carbohydrates * vitamins
* fats * minerals
* Proteins .
* alcohol .
Provide energy .
Macronutrients nutrients that deliver calories or energy/fuel to the body. The body needs these
nutrients for growth, its metabolism and other body functions. Macro means large/big, it are
nutrients that the body needs in huge amounts.
Micronutrients nutrients that the body needs in smaller amounts in order for the body to function
properly.
Nutrients have three general functions in the body
Function Nutrients description
Regulate body processes Vitamins, lipids, proteins, minerals, Body processes such as blood pressure, energy
water production and temperature
Contribute to cell and body Lipids, proteins, minerals, water Provide structure to bone, muscle and other cells
structure
Supply energy Carbohydrates, lipids, proteins Supply energy to power muscle contractions and
cellular functions.
Macronutrients
1 kcal is the amount of energy that will raise the temp of 1 kg of water
by 1°C
* carbohydrates 4.2 kcal / 1 gram of carbohydrates
* fats 9.4 Kcal / 1 gram of fats
* proteins 4.2 kcal / 1 gram of proteins.
Carbohydrates
Carbohydrates are made of carbon, hydrogen and oxygen ( C H O ) and are a major source of fuel for
the body. Dietary carbohydrates are starches and sugars found in grains, vegetables, legumes (dry
beans and peas) and fruits.
The body converts most dietary carbohydrates to glucose, a simple sugar compound. It is glucose
that can be found in the circulation, providing a source of energy for cells and tissues.
Simple carbohydrates are naturally present as simple sugars in fruits, milk and other foods.
Simple sugars are monosaccharides (glucose, fructose and galactose) or disaccharides.
,Mono-saccharides consists of a single sugar molecule. These are any sugars that aren’t broken down
during digestion and these have the general formula CnHnOn, where n = 3 – 7.
All (glucose, fructose, galactose) have 6 carbons and the chemical formula formula C6H12O6 but each
has a different arrangement of these atoms.
Glucose is the most abundant simple carbohydrate unit in nature. Glucose makes up at least one of
the two sugar molecules in every disaccharide. In the body glucose supplies energy to the cells. The
body closely regulates blood glucose (blood sugar) levels to ensure a constant fuel source for vital
body functions. It is the only fuel used by the brain (except during prolonged starvation).
Disaccharides consist of two sugar molecules chemically joined together by a glycosidic bond. This
process of chemically joining is called condensation.
These include sucrose (common table sugar), lactose (milk sugar) and maltose.
Complex carbohydrates are chains of more than two sugar molecules.
- Oligosaccharides = short chain carbohydrates containing between 3 and 10 sugar molecules
- Polysaccharides = long carbohydrate chains, can contain hundreds or thousands. 1`11
Some form straight chains whereas others branch off in all directions.
The way monosaccharides are linked makes them digestible (starch) or non-digestible (fiber).
Starch (‘’zetmeel’’) plants store energy as starch for usage during growth and reproduction.
Sources of starch are grains (wheat, rice, corn and oats), legumes (peas, beans and lentils) and tubers
(potatoes, yams and cassava).
In plants, starch takes two main forms amylose and amyloceptin.
- Amylose is made up of long unbranched chains of glucose molecules.
- Amylopectin is made up of branched chains of glucose molecules.
Amylose has lower digestibility than amylopectin, but amylopectin is more abundant in foods.
,Glycogen (‘’animal starch’’) it is the storage form of carbohydrates in living animals. It is composed
of long, highly branched chains of glucose molecules.
Fibers dietary fibers are non-digestible carbohydrates that are intact and intrinsic in plants. These
fibers go intact through our intestinal system and help to remove waste out of the body.
Characteristics of fibers
There are soluble (gums, pectins, beta-glucans, psyllium) and there are insoluble fibers
(cellulose, lignin)
Fibers have different functions
Fermentation by intestinal flora yields short-chain fatty acids
Dietary soluble fiber ensures gel forms a gel in the stomach that slows down the emptying
of the stomach and therefore slows down the glucose intake.
Lipids
Lipids refer to substances known as fat and oils but also to fatlike substances in foods such as
cholesterol and phospholipids. Lipids are generally hydrophobic (‘’water-fearing’’) and lipophilic
(‘’fat-loving’’). Lipids are organic compounds and contain carbon, hydrogen and oxygen.
Fats and oils also called triglycerides.
A triglyceride is an ester derived from glycerol and 3 fatty acids and is stored in adipose tissue by fat
cells.They are another major fuel source for the body. In addition, triglycerides, cholesterol and
phospholipids have other important functions such as providing structure for body cells, carrying the
fat-soluble vitamins (A, D, E and K) and providing starting material (cholesterol) for making many
hormones. The main classes of lipids found in foods and in the body are triglycerides, phospholipids
and sterols.
2% of dietary lipids are phospholipids, found in both plant and animal foods and made by the body.
Phospholipids are soluble in both fat and water. Only a small percentage is sterols, but the body
makes cholesterol (a form of sterol). Cholesterol is an important component of cell membranes.
The fatty acids determines the characteristic of a fat, such as whether it is solid or liquid at room
temperature. Fatty acids that aren’t joined with another compound (e.g. glycerol) are ‘free’ fatty
acids. There are many kinds of fatty acids but they are all basically chains of carbon atoms with an
organic acid / carboxyl group (-COOH) at one end and a methyl group (-CH3) at the other end.
These fatty acids differ in chain length (number of C’s in the chain).
- Short chain fatty acids have < 6 carbons.
- Medium chain fatty acids have between 6 and 10 carbons.
- Long chain fatty acids have > 12 carbons.
The shorter the carbon chain the more liquid the fatty acid (lower melting point). Shorter fatty acids
are also more water-soluble, a property that affects their absorption in the digestive tract.
The scientific naming of fatty acids: Counting from the carbon at the acid end (alpha carbon) and the
carbon at the methyl end (omega carbon).
Within a fatty acid chain each carbon has 4 bonds. When a carbon is joined to adjacent carbons with
single bonds (-C-C-C-), it still has two bonds available for other atoms (H).
- Saturated fatty acid if all the carbons in the chain are joined with single bonds and the
remaining bonds are filled with hydrogen.
- Unsaturated fatty acid if adjoining carbons are connected by a double bond (C=C), there
are fewer bonds holding the hydrogen and the chain isn’t saturated with hydrogen.
Monounsaturated fatty acid (MUFA) = a fatty acid with one double bond
Polyunsaturated fatty acid (PUFA) = a fatty acid with two or more double bonds.
,Foods never contain only unsaturated or only saturated fatty acids, it is always a mixture. Foods rich
in saturated fatty acids tend to be solid at room temp and have higher melting points.
Unsaturated fatty acids can exist in isomers cis and trans fatty acids.
The cis fatty acid’s carbon chain is bent. The trans fatty acid’s carbon chain is straighter.
The location of the double bond closest to the omega (methyl) end of the fatty acid chain identifies a
fatty acid’s family.
Omega-9-fatty acid oleic acid Oleic acid has one double bond at carbon 9 (counting from
omega end)
Omega-6-fatty acid Linoleic acid has double bonds both at carbon 6 and carbon 9. First
double bond occurs at carbon 6.
Omega-3-fatty acid Alpha-linoleic acid has a double bond at carbon 3, plus two or more
additional bonds.
Hydrogenation a chemical reaction in which hydrogen atoms are added to carbon-carbon double
bonds, converting them to single bonds. Hydrogenation of MUFA and PUFA reduces the number of
double bonds they contain, thereby making them more saturated.
Essential vs non-essential fatty acids.
The liver adds carbons in a process called elongation to build storage and structural fats. The body
also synthesizes oleic acid (omega 9 fatty acid) by removing hydrogens from carbons 9 and 10 of
saturated stearic acid thus creating a double bond at carbon 9, this process is called desaturation.
Oleic acid can be elongated further and desaturated to create other necessary fatty acids. The body
can’t produce double bonds before the 9 carbon from the methyl end.
Non-essential acids = body can make itself, omega-9.
Essential fatty acids (EFA) = fatty acids that the body can’t produce, omega-6 and omega-3.
(summary) Lipids can be divided into: saturated and unsaturated (mono and poly).
Saturated = often animal fats, have a solid shape. Don’t have a double bound.
Unsaturated = fat which is soft/liquid at room temp. Is vegetal and has a double bound.
(healthy). There are mono-unsaturated and poly-unsaturated fats
Trans fats = unhealthy unsaturated fats. It’s the hardening of fats. They act as saturated fatty
acid and are created when an otherwise naturally unsaturated fat is hydrogenated (hydrogen
atoms are added to the food). This solidifies fats that would otherwise be liquids. One of the
hydrogen atoms moves from it’s original position from cis to trans.
, Saturated fats Unsaturated fats
Type of bonds Consist of single bond Consist of at least 1 double bond
Melting point High Low
Cholesterol Increase LDL (bad cholesterol) Increase HDL (good cholesterol)
Sources Animal fats and animal products Plant and nut-based, nuts, whole-grain breads, fish.
Types / Trans fats
Mono-unsaturated fats
Poly-unsaturated fats (omega-3 and omega-6)
Triglyceride structure:
Triglycerides are major lipids in both the diet and the body. A triglyceride consists of 3 fatty acids
attached to a molecule of glycerol. Glycerol is an alcohol, a simple three-carbon molecule with an
alcohol (hydroxyl) group (-OH) at each carbon. Glycerol is the backbone of a triglyceride. A
triglyceride is an ester, a combination of an alcohol and an organic acid (e.g. fatty acid). An ester
forms when a hydrogen and an oxygen from the fatty acid’s carboxyl (acid) group combine with a
hydrogen from the alcohol’s hydroxyl (alcohol) group. This is a condensation reaction
(water is produced). An ester linkage chemically joins the altered fatty acid and alcohol, a process
called esterification.
Esterification produces triglycerides, diglycerides (2 fatty acids) and monoglycerides (1 fatty acid).
Functions of triglycerides:
Energy source fat is a rich and efficient source of calories. Under normal circumstances
dietary and stored fat supply about 60% of the body’s resting energy needs.
Fat is protein-sparing, fat is burned for energy, sparing valuable proteins for their important
roles (e.g. muscle tissue, enzymes, antibodies).
Energy reserve excess dietary fat is stored as body fat to tide us over during periods of
calorie deficit. The fat is stored inside fat cells called adipocytes which form body fat tissue.
Types of fat:
- Visceral fat fat stores that cushion body organs.
- Subcutaneous fat fat stores under the skin.
, Proteins
Proteins are organic compounds made of smaller building blocks named amino acids. Amino acids
contain nitrogen, carbon, hydrogen and oxygen. Body proteins help build and maintain body
structures and regulate body processes. Protein can also be used for energy.
Amino acids (except proline) uniformly consist of a central carbon atom chemically bonded to one
hydrogen atom (H), one carboxylic acid group (-COOH), one amino group (-NH2) and one side group
unique to each amino acid (R).
- Dispensable amino acids = AA that the body can make if supplied with adequate nitrogen.
Don’t need to be supplied in the diet.
- Conditionally indispensable amino acids = AA that are normally made in the body
(dispensable) but become indispensable under certain circumstances (e.g. critical illness.)
In the proteins from humans there are 20 different amino acids, in adults 8 of these amino acids are
not formed or are insufficiently formed (essential amino acids). These have to come in through food.
The 8 essential amino acids are: valine, osileucine, leucine, phenylalanine, threonine, tryptophan,
methionine and lysine.
The other not-essential amino acids can be formed in the liver out of other amino acids.
Amino acids link in a specific sequence to form strand of protein (peptides) up to 100’s of amino
acids long. A peptide-bond links amino acids into a protein. To form a peptide bond, the carboxyl (-
COOH) group of one amino acids bonds to the amino (-NH) group of another. In this process water
(H2O) is released.
Oligopeptide = chain of 4 to 10 amino acids
Polypeptide = chain of more than 10 amino acids.
Complete protein contains all the essential amino acids.
Incomplete protein = contains a few of the essential amino acids. Lack
one or more essential.
Functions of body proteins:
The human body contains 1000’s of different proteins, each with a specific function determined by
its unique shape.
Function Description
Catalyst Enzymes, these speed up chemical reactions.
Transport Transports many key substances such as oxygen, vitamins and minerals to target cells
throughout the body
Structure structures such as bone, skin and hair owe their physical properties to unique proteins.
(e.g. Collagen). Hair and nails are made of keratin.
Mobility Sperm cell movement
Immunity Antibodies made of protein protect us from foreign substances
Maintaining of fluid balance By pumping molecules across cell membranes and attracting water
Maintaining of acid and base By taking up or giving off hydrogen ions as needed
balance
Communication Hormones, a kind of chemical messengers
