1. Lecture 11: Lipids and Proteins
Chemistry - SPRING 2017
Course lecturer :
Jasmin Šutković
10th May 2017

2. Content Molecules of life! Lipids? Types of lipids? Fatty acids
Triglycerides and Waxes and their properties
Phospholipids
Steroids and health examples
Cell membrane
Proteins
Essential Amino Acids
Polypeptides bonds
Protein structure
Enzymes and their activity

3. Introduction
Lipids are biomolecules that are soluble in organic solvents and insoluble in water.
They are found in many varieties, so having many functions!
Common lipids include triacylglycerols in vegetable oils, cholesterol in egg yolk, and vitamin E in leafy greens.

4. The word lipid comes from the Greek word
lipos for fat.

5. Lipids contain a large number of nonpolar C–C and C–H bonds
Lipids contain a large number of nonpolar C–C and C–H bonds. In addition, most lipids have a few polar bonds that may be found in a variety of functional groups.
For example, a triacylglycerol contains three esters, cholesterol possesses a hydroxyl group, and vitamin E has both a phenol (an OH group on a benzene ring) and an ether.

6. Types of lipids
Lipids can be categorized as hydrolyzable or nonhydrolyzable.

8. Roles
In biological systems.
Lipids release over twice the amount of energy per gram than carbohydrates or proteins (9 kcal/g for lipids compared to 4 kcal/g for carbohydrates and proteins, Section 6.1), lipids are an excellent source of energy

9. Moreover, lipids are key components of the cell membrane, and they serve as chemical messengers in the body.
A lipid coating protects a leaf’s surface and keeps it from drying out. Ducks are insulated by a protective layer of lipids on their feathers.

10. Lipid bilayer in a cell

11. FATTY ACIDS
Hydrolyzable lipids are derived from fatty acids, carboxylic acids that were first discussed in Section 13.3B.
Fatty acids are carboxylic acids (RCOOH) with long carbon chains of 12–20 carbon atoms.

12. Palmitic acid
Palmitic acid is a common 16-carbon fatty acid whose structure is given in condensed, skeletal, and three-dimensional representations.

13. The nonpolar part of the molecule (comprised of C-C and C-H bonds) is not attracted to water, so it is said to be hydrophobic (water fearing). The polar part of the molecule is attracted to water, so it is said to be hydrophilic (water loving). In a lipid, the hydrophobic portion is always much larger than the hydrophilic portion.

14. Two types of fatty acids :
Saturated fatty acids have no double bonds in their long hydrocarbon chains.
Unsaturated fatty acids have one or more double bonds in their long hydrocarbon chains. Generally, double bonds in naturally occurring fatty acids are cis.

15. WAXES Waxes are the simplest hydrolyzable lipids.
Waxes are esters (RCOOR') formed from a fatty acid (RCOOH) and a high molecular weight alcohol (R'OH). 15

16. Because of their long nonpolar carbon chains, waxes are very hydrophobic.
They form a protective coating on the feathers of birds to make them water repellent, and on leaves to prevent water evaporation.
Lanolin is a wax thatcoats the wool fibers of sheep.
Beeswax, a complex mixture of over 200 different compounds, contains the wax myricyl palmitate as its major component

17. TRIACYLGLYCEROLS—FATS AND OILS
Animal fats and vegetable oils, the most abundant lipids, are composed of triacylglycerols
Triacylglycerols, or triglycerides, are triesters formed from glycerol and three molecules of fatty acids.

19. FOCUS ON HEALTH & MEDICINE FATS AND OILS IN THE DIET
Fats and oils in our diet come from a variety of sources—meat, dairy products, seeds and nuts, salad dressing, fried foods, and any baked good or packaged food made with oil.
Some fat is required in the diet. Fats are the building blocks of cell membranes, and stored body fat insulates an organism and serves as an energy source that can be used at a later time.

20. Currently, the United States Food and Drug Administration recommends that no more than 20–35% of an individual’s calorie intake come from lipids.
Moreover, a high intake of saturated triacylglycerols is linked to an increased incidence of heart disease.

22. FOCUS ON THE HUMAN BODY METABOLISM OF TRIACYLGLYCEROLS
Humans store energy in the form of triacylglycerols, kept in a layer of fat cells, called adipose cells, below the surface of the skin, in bone marrow, in the breast area (of women), around the kidneys, and in the pelvis (Figure 19.2).
Adipose tissue contains large groups of adipose cells, some of which may be with lipid molecules that the remainder of the cell—the cytoplasm and the nucleus—occupies only a small volume on one side.
In adulthood, the number of adipose cells is constant. When weight is lost or gained the amount of stored lipid in each cell changes, but the number of adipose cells does not change.

23. PHOSPHOLIPIDS Phospholipids are lipids that contain a phosphorus atom.
Two common types of phospholipids are phosphoacylglycerols and sphingomyelins.
Both classes are found almost exclusively in the cell membranes of plants and animals .

24. Cholesterol – most abudant steroid
Steroids are lipids whose carbon skeletons contain three six-membered rings and one five membered ring.

25. Cholesterol, the most prominent member of the steroid family, is synthesized in the liver and found in almost all body tissues.
It is a vital component for healthy cell membranes, and it serves as the starting material for the synthesis of all other steroids and vitamin D.

26. Health ?
Cholesterol is obtained in the diet from a variety of sources, including meat, cheese, butter, and eggs.
Table 19.4 lists the cholesterol content in some foods. 4
While the American Heart Association currently recommends that the daily intake of cholesterol should be less than 300 mg, the average American diet includes 400–500 mg of cholesterol each day.

28. Fat soluble vitamins The fat-soluble vitamins are lipids.
The four fat-soluble vitamins—A, D, E, and K—are found in fruits and vegetables, fi sh, liver, and dairy products. Although fat-soluble vitamins must be obtained from the diet, they do not have to be ingested every day.
Excess vitamins are stored in adipose cells, and then used when needed.
Table 19.5 summarizes the dietary sources and recommended daily intake of the fatsoluble vitamins.

30. Proteins
• Proteins are biologically active polymers formed from amino acids linked together by amide bonds; in addition to an amine group and a carboxylic acid group, each amino acid contains a characteristic R group
The nature of the R group determines the particular chemical properties of each amino acid !!!
• Some proteins are enzymes that catalyze biological reactions

31. Essential, Nonessential, and Conditional
Essential – must be consumed in the diet
Nonessential – can be synthesized in the body
Conditionally essential – cannot be synthesized due to illness or lack of necessary precursors
Premature infants lack sufficient enzymes needed to create arginine

33. Introduction
The word protein comes from the Greek proteios meaning “of first importance.”
Fibrous proteins, like keratin in hair, skin, and nails and collagen in connective tissue, give support and structure to tissues and cells.
Protein hormones and enzymes regulate the body’s metabolism!!!
Transport proteins carry substances through the blood, and storage proteins store elements and ions in organs.

34. AMINO ACIDS
To understand protein properties and structure, we must first learn about the amino acids that compose them.
Amino acids contain two functional groups—an amino group (NH2) and a carboxyl group (COOH). In most naturally occurring amino acids, the amino group is bonded to the α carbon, the carbon adjacent to the carbonyl group, making them 𝛂-amino acids.

36. Humans can synthesize only 10 of the 20 amino acids needed for proteins. The remaining 10, called essential amino acids, must be obtained from the diet and consumed on a regular, almost daily basis.
Diets that include animal products readily supply all of the needed amino acids.

37. ACID–BASE BEHAVIOR OF AMINO ACIDS
As mentioned in Section 21.2, an amino acid contains both a basic amino group (NH2) and an acidic carboxyl group (COOH). As a result, proton transfer from the acid to the base forms a zwitterion, a salt that contains both a positive and a negative charge.
The zwitterion is neutral; that is, the net charge on the salt is zero.
pH = 6 – no net charge

38. PEPTIDES
When amino acids are joined together by amide bonds, they form larger molecules called peptides and proteins.
A dipeptide has two amino acids joined together by one amide bond.
A tripeptide has three amino acids joined together by two amide bonds

39. Polypeptides and proteins both have many amino acids joined together in long linear chains, but the term protein is usually reserved for polymers of more than 40 amino acids.

40. FOCUS ON THE HUMAN BODY BIOLOGICALLY ACTIVE PEPTIDES
NEUROPEPTIDES—ENKEPHALINS for PAIN RELIEF
Enkephalins, pentapeptides synthesized in the brain, act as pain killers and sedatives by binding to pain receptors.
The addictive narcotic analgetics morphine and heroin bind to the same receptors as the enkephalins, and thus produce a similar physiologica response.
Enkephalins are related to a group of larger polypeptides called endorphins that contain 16–31 amino acids. Endorphins also block pain and are thought to produce the feeling of well-being experienced by an athlete after excessive or strenuous exercise.

41. Protein STRUCTURE

42. 42

43. TERTIARY AND QUATERNARY STRUCTURE
The three-dimensional shape adopted by the entire peptide chain is called its tertiary structure.
A peptide generally folds into a shape that maximizes its stability.
In addition, polar functional groups hydrogen bond with each other (not just water), and amino acids with charged side chains like –COO– and –NH3 + can stabilize tertiary structure by electrostatic interactions.
Finally, disulfide bonds are the only covalent bonds that stabilize tertiary structure

44. Celluloze

46. FOCUS ON THE HUMAN BODY COMMON PROTEIN
Proteins are generally classified according to their three-dimensional shapes.
Fibrous proteins are composed of long linear polypeptide chains that are bundled together to form rods or sheets. These proteins are insoluble in water and serve structural roles, giving strength and protection to tissues and cells.
Globular proteins are coiled into compact shapes with hydrophilic outer surfaces that make them water soluble. Enzymes and transport proteins are globular to make them soluble in blood and other aqueous environments.

47. α-KERATINS
α-Keratins are the proteins found in hair, hooves, nails, skin, and wool.
They are composed almost exclusively of long sections of α-helix units, having large numbers of alanine and leucine residues.
Since these nonpolar amino acids extend outward from the α-helix, these proteins are very insoluble in water.
Two α-keratin helices coil around each other, forming a structure called a supercoil or superhelix

49. COLLAGEN
Collagen, the most abundant protein in vertebrates, is found in connective tissues such as bone, cartilage, tendons, teeth, and blood vessels.
Glycine and proline account for a large fraction of its amino acid residues.
Collagen forms an elongated left-handed helix, and then three of these helices wind around each other to form a right-handed superhelix or triple helix.
Two views of the collagen superhelix are shown in Figure

50. HEMOGLOBIN AND MYOGLOBIN
Hemoglobin and myoglobin, two globular proteins, are called conjugated proteins because they are composed of a protein unit and a nonprotein molecule.
In hemoglobin and myoglobin, the nonprotein unit is called heme, a complex organic compound containing the Fe2+ ion complexed with a large nitrogen-containing ring system.
The Fe2+ ion of hemoglobin and myoglobin binds oxygen.
Hemoglobin, which is present in red blood cells, transports oxygen to wherever it is needed in the body, whereas myoglobin stores oxygen in tissues.

52. Sickle cell anemia
Is a hereditary blood disorder, characterized by red blood cells that assume an abnormal, rigid, sickle shape.
Sickling decreases the cells' flexibility and results in a risk of various complications.
The sickling occurs because of a mutation in the haemoglobin gene. Individuals with one copy of the defunct gene display both normal and abnormal haemoglobin!

53. Quiz II
15th June
Starting with lecture 6 to 11!
Good luck.