Chapter 5 The Structure and Function of Macromolecules

1
Chapter 5The Structure and Function of
Macromolecules

• 3 themes are emphasized
• Hierarchy of structural levels
• Emergent properties
• Form fits function

2
Polymers

• Monomers- units that comprise a polymer
• Polymer- long molecule consisting of many similar
  or identical building blocks linked by covalent
  bonds

3
Polymer formation

• Condensation reaction- linking of monomers
  through the loss of a water molecule (dehydration
  reaction)

4
Polymer formation

• One molecules provides the hydroxyl group (-OH)
  and the other the hydrogen (-H).
• Requires energy and enzymes

5
Polymer disassembly

• Hydrolysis- dissemble polymers
• Water is added to break a bond
• Ex digestion- food polymers broken down by
  enzymes

6
(No Transcript)
7
Classes of Polymers

• Carbohydrates
• Lipids
• Proteins
• Nucleic Acids
• Other

8
Carbohydrates

• Monomers called monosaccharides
• Cellular use energy, energy storage, structure
• (C, 2H, O)n
• Monosaccharides, disaccharides, and
  polysaccharides

9
Monosaccharides

• Glucose
• Aldehydes and ketones
• Linear and ring forms

10
(No Transcript)
11
Disaccharides

• 2 monosaccharides, sucrose glucosefructose
• Joined by a condensation synthesis called a
  glycosidic linkage.

12
(No Transcript)
13
Polysaccharides

• Several hundred or more monosaccharides
• Energy storage starch and glycogen
• Structural cellulose and chitin

14
Starch

• Storage of polysaccaharides in plants, made up
  glucose monomers
• Provides a way to store surplus glucose, energy
  can be withdrawn by hydrolysis
• Humans have enzymes that can hydrolyze plant
  starch. High sources of starch found in potatoes,
  grains (wheat, corn, rice).

15
Glycogen

• Used by animals to store glucose.
• More extensively branched than plant starch.
• Stored mainly in liver and muscle cells. Humans
  can only store enough energy for about a day.

16
Cellulose

• Polysaccharide used by plants from structure.
• Similar to starch except in the location of the
  glucose bond
• Starch- alpha linkage, helical shape
• Cellulose- beta linkage, straight shape
• Opposing hydroxyl groups bond with other strands,
  creating strong fibers.

17
(No Transcript)
18
Why dont humans eat grass?
19
(No Transcript)
20
Chitin

• structural polysaccharide used by arthropods
  (insects, spiders, crustaceans) to build their
  exoskeleton
• Also used by fungi rather than cellulose for
  their cell walls.
• Similar to cellulose except has a nitrogen
  appendage to the glucose.

21
(No Transcript)
22
Lipids

• Fats
• Not polymers but
• Large molecules, composed of smaller molecules,
  assembled by dehydration reactions
• Not soluble in water. C-H bonds are non polar

23
Triglycerides

• Fat molecule Triacylglycerol (or triglyceride)
• Triacyglycerol Glycerol 3 fatty acids
• Linked by ester linkage (condensation reaction)
• Oils and fats

24
Animal fat vs. Plant and Fish fat

• Saturated fat vs unsaturated fat
• Animal fat- usually saturated- solid at room
  temperature
• Plant and fish fat- usually unsaturated- liquid
  at room temperature

25
(No Transcript)
26
Fat- what is it good for?

• Fat- stores energy
• 1 gram of fat stores 2x energy as starch
• Stored in adipose cells
• Cushions vital organs
• Provide insulation

27
Phospholipids

• 2 fatty acids phosphate group glycerol

28
Phospholipids

• Various molecules attach to the phosphate group 
• Tails are hydrophobic
• Heads are hydrophilic
• What do they do in water?

29
Phospholipids

• When added to water- they self assemble so that
  they shield their hydrophobic tails
• Micelle- phospholipid droplet, phosphate heads on
  the outside, tails are restricted to the
  water-free interior
• Phospholipid bilayer- major component of cell
  membranes

30
Steroids

• Four interlocking carbon rings
• Regulatory molecules- sex hormones
• Cholesterol-precursor of many steroids
• Cholesterol is a component of cell membranes
• Cholesterol can contribute to atherosclerosis

31
(No Transcript)
32
Proteins

• Monomers called amino acids
• 20 different amino acids
• Joined by peptide linkage
• Chains of amino acids- polypeptide
• Function as support, storage, transport,
  signaling, defense, movement, and catalysts
• C, H, O, N, S
• Make up 50 of cellular DRY weight

33

• Tens of thousands different types in humans
• Enzymes- regulate metabolism, accelerate chemical
  reactions

34
Amino Acid Structure

• Contains 3 functional groups
• Amino, carboxyl and R groups
• Polar, nonpolar, charged and uncharged

35
(No Transcript)
36
(No Transcript)
37
Amino acid linkage

• Peptide bond- covalent bond catalyzed by a
  dehydration reaction

38
(No Transcript)
39
Amino end N-terminus Carboxyl end C-terminus
40
(No Transcript)
41
Polypeptide vs Protein

• Protein- one or more polypeptides twisted,
  folded, and coiled.

42
Four Levels of Protein Organization

• Primary- sequence of amino acids

43
(No Transcript)
44
Sequence determines function

• 20 different amino acids
• Lysozyme- protein that helps fight bacteria
• 129 amino acids long
• 20129 possible combinations
• Sickle cell disease is caused by one protein
  substitution in the structure of hemoglobin.

45
Four Levels of Protein Organization

• Primary- sequence of amino acids
• Secondary- coils or folds

46
Secondary- coils and folds

• Result from hydrogen bonding on the backbone of
  the chain (not the R groups)
• Oxygen and nitrogen are electronegative with
  partial negative charges.
• Hydrogen molecules attached to Nitrogen have
  partial positive charges.

47
Secondary coil

• Alpha helix- delicate coil held together by
  hydrogen bonding between every fourth amino acid

48
Secondary Fold

• Beta pleated sheet- two or more parallel chains.
  Held together by hydrogen bonds of the backbone.

49
(No Transcript)
50
Four Levels of Protein Organization

• Primary- sequence of amino acids
• Secondary- coils or folds
• Tertiary- R group interaction

51
Tertiary structure

• R groups interact
• Hydrophobic interaction
• Hydrophobic (nonpolar) R groups cluster at the
  core
• Held together by van der Waals interactions

52
Tertiary structure

• Disulfide bridges-
• Two sulfhyryl groups (-SH) form covalent bond

53
Four Levels of Protein Organization

• Primary- sequence of amino acids
• Secondary- coils or folds
• Tertiary- R group interaction
• Quaternary

54
Quaternary Structure

• Overall shape of the protein- determines its
  function.
• Denaturation- unraveling of a protein
• Reversable?

55
(No Transcript)
56
Protein Research

• 100,000 amino acid sequence is known
• 10,000- 3D shape is known
• X-Ray crystallography

57
Chaperonins- (chaperone proteins)

• Help proteins fold correctly
• Keeps them away from bad influences

58
Nucleic Acids

• Monomers are nucleotides
• Polymers are 2 types RNA and DNA
• Function
• 1) control heredity
• 2) control cell functions

59
DNA -gt RNA -gt Protein
60
(No Transcript)
61
Purines and Pyrimidines

• Purines
• 1) adenine and guanine
• 2) double ring structure
• Pyrimidines
• 1) thymine, uracil, and cytosine
• 2) single ring

62

• Deoxyribose- lacks an oxygen atom on its number 2
  carbon
• Ribose

63

• Phosphodiester linkages- links between phosphate
  of one nucleotide to the sugar of the next

64
DNA and RNA shape

• DNA- double stranded, double helix
• Shaped discovered by James Watson and Francis
  Crick in 1953
• RNA- single stranded

65
Nucleotides

• 3 parts 5-C sugar, phosphate and nitrogenous
  base
• 2 types of sugars ribose and deoxyribose
• 2 types of nitrogenous bases purines and
  pyrimidines

66
Evolutionary relationships

• Taxonomy- based on characteristics
• DNA sequencing- allows for taxonomy based on
  genetic closeness