Biological Molecules.

Presentation on theme: "Biological Molecules."— Presentation transcript:

1 Biological Molecules

2 Organic Chemistry & Functional Groups

3 Organic Compounds Carbon-based molecules
Second most abundant type of compound found in organisms Over 2 million known organic compounds Properties of organic compounds depend on its size, shape, and type of functional group attached to it

4 What is a Functional Group?
Atoms, such as nitrogen, oxygen, phosphate and sulfur covalently bonded to a carbon backbone They are groups that change both the structure and behavior of a molecule, i.e., solubility, reactivity with other molecules They help chemists and biochemists classify different molecules found in living organisms Functional groups containing nitrogen or oxygen are polar and therefore hydrophylic and thus water-soluble

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6 Functional Groups in Biological Molecules
GROUP STRUCTURAL FORMULA COMMON LOCATION H Methyl - C - H fats, oils, waxes Hydroxyl - OH sugars, other alcohols Aldehyde - C sugars OH Ketone - C = O sugars, hormones O Carboxyl - C sugars, fats, amino acids

7 Functional Groups in Biological Molecules
GROUP STRUCTURAL FORMULA COMMON LOCATION H H Amino - N or - N - H amino acids, proteins H H O- Phosphate - O - P - O- DNA, RNA, ATP, lipids O Sulfhydryl - S - H proteins

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9 Five Classes of Chemical Reactions in Biological Systems

10 Five Classes of Reactions
1. Functional-group transfer 2. Electron transfer 3. Rearrangement 4. Condensation (dehydration) 5. Cleavage (hydrolysis)

11 1. Functional-Group Transfer
one molecule gives up a functional group, which another molecule accepts seen in metabolic reactions, ex., glycolysis

12 2. Electron Transfer one or more electrons stripped from one molecule are donated to another molecule seen in metabolic reactions, ex., Kreb’s cycle, glycolysis

13 3. Rearrangement a juggling of internal bonds converts one type of organic compound into another seen in many metabolic pathways ex., glycolysis, Kreb’s cycle, etc.

14 4. Condensation (Dehydration)
through covalent bonding, two molecules combine to form a larger molecule many successive condensation reactions leads to polymerization cells undergo condensation reactions to produce complex carbohydrates, lipids and proteins

15 Polymerization & Condensation/Dehydration Reactions

16 5. Cleavage (Hydrolysis)
a molecule splits into two smaller ones hydrolysis, is a very common biological cleavage. It is like condensation in reverse cells hydrolyze large polymers like starch and proteins, then use the released subunits as building blocks or energy sources

17 Hydrolysis/Cleavage Reactions

18 Carbohydrates

19 Carbohydrates a simple sugar or a molecule composed of two or more sugar units can be used as either an immediate energy source, stored energy source or structural material 3 classes are: 1) monosaccharides, 2) oligosaccharides, 3) polysaccharides

20 Monosaccharides Simplest carbohydrates Also called simple sugars
Suffix - ose Glucose, Fructose, Galactose (hexoses) Ribose (pentose) Empirical formula is generally CH2O Usually form ring structures in aqueous solution functional groups include: hydroxyl and aldehyde or ketone

21 Aldehyde vs. Keytone ISOMERS both have chemical formula of C6H12O6

22 Glucose Ring Structures

23 Oligosaccharide Is a short chain of two or more covalently bonded sugar units Two or more monosaccharides join by dehydration reactions Disaccharide = two sugars lactose - milk sugar (glucose + galactose) sucrose - fruit sugar (glucose + fructose) maltose - beer, seeds (glucose + glucose)

24 Sucrose

25 Dehydration Reaction in Maltose Formation

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27 Complex Carbohydrates Polysaccharides
straight or branched chain of hundreds or thousands of the same or different sugar units (monomers) glucose-based polysaccharides: starch - plant energy storage cellulose - plant structural form glycogen - animal energy storage

28 Polymers of Glucose

29 Fats & Lipids

30 Five Classes of Lipids Fatty Acids Triglycerides Phospholipids Waxes
Sterols

31 Fatty Acids Contains a carbon backbone of up to 36 carbon atoms
Contains a carboxyl group at one end Can be saturated (only single bonds) Can be unsaturated (may have one or more double or triple bonds) Saturated are solid at room temperature Unsaturated are liquid

32 Saturated vs. Unsaturated Fatty Acids

33 Saturated & Unsaturated Fatty Acids

34 Trans Fatty Acids Increases the « bad » LDL cholesterol (low-density lipoprotein) and decreases the good HDL (high-density lipoprotein) Suggested that you should not consume more than 2 g of trans fat/day in a 2000 kcal/day diet

35 Oleic Acid in olive oil – cis-fatty acid Elaidic Acid - a
OH O Myristic Acid – a Saturated fatty-acid OH O Oleic Acid in olive oil – cis-fatty acid O OH Elaidic Acid - a Trans- fatty acid

36 Other Effects of Trans Fats
Cancer Type 2 diabetes Obesity Liver Dysfunction Ovulatory Infertility

37 What if Trans fats are not labelled?
add up the values for saturated, polyunsaturated and monounsaturated fats. If the number is less than the "Total fats" shown on the label, the unaccounted is trans fat.

38 Triglycerides Composed of a glycerol molecule and three fatty acids
Body’s most abundant lipid & best source of energy FAT!!! Adipose tissue contains high concentrations of triglycerides

39 Condensation Reaction in Triglycerides

40 Phospholipids Main component of cell membrane
Hydrophilic head - glycerol + phosphate Hydrophobic tail - 2 fatty acids

41 Phospholipid

42 WAXES

43 Waxes Long-chain fatty acids linked to an alcohol or carbon rings
Very water repellent

44 Paraffin Wax Breathing in paraffin candle wax may be carcinogenic

45 Bee’s Wax

46 Sterols/Steroids No fatty acid tails! Backbone of 4 fused carbon rings
Sterols differ functional group types and positions Examples: cholesterol and hormones

47 Cholesterol

48 Anabolic Steroids Synthetic variants of testosterone
Overdosing causes: Mood swings Liver damage leading to cancer High blood pressure Shrinks testicles, reduces sex drive & causes infertility & breast enlargement in men Disrupts menstral cycle & leads to male characteristics in females Stunts growth & stops bone growth in teens

49 Proteins

50 Silk Proteins

51 Protein Biological polymer constructed from amino acid monomers
Tens of thousands of proteins found in the human body Each protein has its unique three-dimensional structure that corresponds to a specific function Seven classes of proteins

52 Classes of Proteins Protein
Structural – silk, hair, fibers, ligaments Contractile – muscle Storage – ovalbumin Defensive – antibodies Transport – hemoglobin, membrane Signal – certain hormones Enzymes - catalyst

53 Protein Shape Consists of one or more polypeptide chains
Either globular or fibrous in shape Can be denatured (unraveled) by heat, changes in salt concentration and pH

54 Basic Structure of an Amino Acid

55 Water vs. Fat-Soluble Amino Acids

56 Peptide-Bond Formation

57 Structural Levels Primary 1° Secondary 2° Tertiary 3° Quaternary 4°

58 Primary Structure Amino acid sequence

59 Secondary Structure Either alpha helix or pleated sheet
Patterns maintained by hydrogen bonding between the –N-H groups and – C=O groups

60 Tertiary Structure Globular – contain mixture of  -helix and pleated sheets Fibrous – almost entirely helical Maintained by hydrogen bonding and ionic bonding between R groups of the amino acids.

61 Quaternary Structure Results from bonding interactions between different polypeptides or subunits

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63 Quaternary Structure of Collagen

64 Ribbon vs. Space-filling Models of Proteins

65 Enzymes

66 Enzymes in General speed up metabolic reactions that would normally take years to undergo by lowering the “activation energy” needed for a reaction to occur are named by adding the suffix “ase” to part of the name of the substrate (ex. sucrase)

67 Enzymes Decrease the Activation Energy
Mexican Jumping Bean analogy for energy of activation (EA) and the role of enzymes

68 Characteristics of Enzymes
Do not make any reaction occur that would not normally occur naturally Do not get used up during the reaction Can work both in the forward and reverse directions of a reaction Are highly selective to specific substrates

69 Induced-Fit Model Enzymes have specifically shaped “active sites” on their surfaces that interact with the substrate(s) As the substrate enters this active site it induces the enzyme to change shape so that the active site fits even more snugly around the substrate (clasping handshake) This “induced-fit” strains the pre-existing bonds within the substrate(s) and promotes the formation of new bonds (in products)

70 The role of sucrase in sucrose cleavage

71 Hexokinase is an enzyme that catalyzes the ATP-dependent phosphorylation of glucose to glucose-6-phosphate. This is the first step and the first rate-limiting step the glycolytic pathway

72 Induced-Fit Model of Hexokinase

73 Factors Affecting Enzyme Activity
Temperature - causes denaturation of the secondary & tertiary structures of the enzyme, hence changing the shape of the active site, therefore destroying enzymatic action pH - same as above Salinity - same as above

74 Effect of Temperature on Different Enzymes

75 Allosteric Control allo - different steric - structure
enzymes can be activated or inhibited when a specific substance combines with them at a site other than the active site or within the active site

76 Enzyme Inhibitors

77 Feedback Inhibition When an end product accumulates, some of the excess product binds to an enzyme molecule, hence acting as an allosteric inhibitor and therefore blocking the production of more product

78 Coenzymes A coenzyme can alter the shape of the enzyme’s active site allowing a better fit with its substrate they can also serve as transfer agents of atoms, electrons, H+ ions or functional groups.

79 Nucleic Acids

80 What is the problem with the figure of the double helix?