Biological Molecules Great and Small

1
Chapter 3
Biological Molecules Great and Small
Chapter Goal Understanding how cells use small
building blocks to build
larger molecules and how
some of those molecules then fold into
3-D shapes
2
Key Questions

• How do organisms use carbon atoms decorated with
  functional groups to build basic molecules of
  life?
• What are the categories of building block
  molecules?
• What reactions link and unlink building blocks?
• How are fatty acids, polysaccharides, nucleic
  acids and proteins formed?

3
Biological Molecules

• Size either small (MWlt300) or large (MWgt10,000)
• Organic molecules based on hydrogen, carbon,
  nitrogen, oxygen, rarely phosphorus and sulfur
• Are built of subunits building blocks

4
Biological Molecules are Organic Compounds

• Common elements in living systems
• C, H, O, N are the great majority atoms (96.3)
  in living things.
• Important ions Na, K, Mg, Ca, P, S, Cl,
• Trace ions and minerals Zn, Cu, Mn, Fe, I, and
  others

5
Subunits and Macromolecules

• Polysaccharides
• Fats and cholesterol
• Proteins
• DNA and RNA

• Sugars
• Lipids
• Amino acids
• Nucleotides

6
Carbon

• Carbon chains and rings are linked by single and
  double covalent bonds

7
Carbon Rings

• Carbon rings can be flat
• Carbon rings can be boat or chair

8
Chemical Interactions of Molecules

• Determined by
• Shape
• Charge distribution
• Interactions with water
• Interactions with other molecules

9
Functional Groups

• Small groups of atoms
• Contribute to the chemical properties of a
  molecule
• Usually attached to the carbon backbone

10
Examples of Functional Groups

• -OH hydroxyl
• -CO carbonyl
• -COOH carboxyl
• -NH2 amine
• -SH sulfhydryl
• -PO4 phosphate

11
Shapes of Biomolecules

• Lipids do not form chains of subunits
• Proteins, nucleic acids and carbohydrates can
  form long chains
• Carbohydrate chains may be branched

12
Linking Subunits to Make Macromolecules

• Macromolecule subunits are linked by removing
  water dehydration condensation

13
Breaking Macromolecules

• Subunits are broken apart by adding water to a
  bond hydrolysis

14
Macromolecules
15
Lipids

• Contain high levels of chemical energy
• Do not dissolve in water
• Have few polar functional groups
• Major component of biological membranes

16
The 6 Lipids Used in Cells
17
Fatty Acids

• Are amphipathic contain some polar groups
• Saturated (no double bonds) or unsaturated (some
  double bonds)

18
Health Effects

• Saturated fats increase cholesterol levels in the
  blood
• Unsaturated fats have less effect on cholesterol
  levels
• Omega-3 fatty acids (from fish and sea weed)
  inhibit inflammation response in blood vessels
  and joints

19
(No Transcript)
20
Forming Triglycerides

• Subunits
• Glycerol
• 3 fatty acids
• Linked by condensation reactions

21
Forming Phospholipids

• Subunits
• Glycerol
• 2 fatty acids

• Head with phosphate group

• Amphipathic
• Linked by condensation reactions

22
Phospholipids in Membranes

• Amphipathic structure causes formation of a
  bilayer
• Charged groups associate with water
• Hydrophobic tails clump together

23
Steroids

• Structure is 4 rings
• Based on cholesterol
• Functional groups determine biological activity

24
Carbohydrates

• Fundamental energy storage molecule
• Subunits are simple sugars 3 9 Carbons
  monosaccharides
• Ex. Glucose, fructose, ribose, deoxyribose
• Linked by dehydration condensation into
  disaccharide and polysaccharides glycosidic
  bond
• Disaccharide sucrose (table sugar)
• Polysaccharide starch, cellulose,
  glycogen,chitin

25
Formation of Polysaccharides

• 2 sugars link to form disaccharide
• Ex. sucrose
• Several sugars oligosaccharide
• Long chains of sugars polysaccharide
• Ex. Starch in bread
• Cellulose in wood and paper

26
Structure of Carbohydrates

• Chemical formula (CH2O)n
• For each carbon
• 1 oxygen
• 2 hydrogens
• Many hydroxyl groups make sugars hydrophilic
• Ribose and deoxyribose building blocks for RNA
  and DNA

27
Carbohydrates and Energy

• Glucose (blood sugar) is the basis of most energy
  releasing reactions
• Short term energy mono- and di-saccharides
• Long term energy storage glycogen in animals,
  starch in plants
• Sugar in coke (15 square sugars or 28g sugar/can)

28
Carbohydrates and Structure

• Glycogen
• Animal energy, branched
• Starch
• Plant energy, branched or unbranched
• Amyrose unbranched, amylopectin branched
• Cellulose
• Structural support for plant cells
• Glucose polysaccharide with bonds in straight
  orientation
• Chitin
• Exoskeleton of arthropods such as butterfly and
  crab
• Modified sugars in chains

29
Carbohydrates in Plants
30
Glycoproteins and Glycolipids

• Glycoproteins have short chains of sugars
  attached to proteins
• Glycolipids have short chains of sugars attached
  to lipids
• Both found on the exterior surface of cells
• Glycoproteins are signs that help cells to
  recognize one another and communicate,
• Glycoproteins attached to newly made proteins act
  as address labels to tell a cell where to ship
  new proteins

31
Polypeptides

• Protein working molecules of a cell, carry out
  biological activities encoded by genes
• Classifications of Functions of Proteins
• -Enzymes catalysts that accelerate the rates
  of biological reactions.
• oxidoreductase, transferase, hydrolase,
  lyase, isomerase, ligase
• -Regulatory proteins sensors and switches,
  control protein activity and gene functions
• hormones, insulin, transcriptional factor,
  lac repressor
• -Transport proteins control the flow of
  materials across cellular membrane.
• Mb Hb (O2), ion channel, serum albumin
  (FA from adipose tissue to organs)
• -Storage proteins as a reservoir of an
  essential nutrients.
• ovalbumin (egg white), casein (???,milk),
  zeins (corn), ferritin (Fe2)
• -Motor proteins cause motion, cell division,
  muscle contraction, cell motility.
• myosin, actin, tubulin, dynein/kinesin
• -Structural proteins provide structural
  rigidity and protection to the cells and tissues.
  
• keratin, collagen, elastin, fibroin
• -Signaling proteins transmit external signals
  to the cell interior.
• receptors, protein kinase/phosphatase, two
  component system
• -Protective or exploitive protein play active
  role in cell defense, protection
• Ig (antibody), thrombin (blood-clotting
  protein), antifreeze protein, toxin

32
Polypeptides

• Structure
• Unbranched chains of amino acids
• Bend into unique shapes

33
Amino Acids

• Subunits of polypeptides
• 20 different types
• Structure
• Amino group
• Carboxyl (acid) group
• R groups differ

34
Amino Acids
35
Formation of Polypeptides

• Linked by dehydration condensation
• Bonds are peptide bonds

36
Protein Shapes

• Globular irregular shapes, non-repeating amino
  acid sequence
• Hemoglobin
• Fibrous regular shapes, repeating sequences
• Keratin, collagen, elastin

37
Protein Structure

• 4 levels of folding
• Primary structure is sequence of amino acids

38
Protein Structure

• Secondary coils or folds of sections of protein
• Alpha helix
• Beta sheet
• Stabilized by hydrogen bonds
• Collagen helix three polypeptide chains wound
  around each other

39
Protein Structure

• Tertiary
• 3-dimensional conformation of entire protein
• Stabilized by covalent, hydrogen and ionic bonds

40
Protein Structure

• Quaternary
• Multiple peptide chains fitted together to make 1
  functional protein

41
Levels of Protein Folding
42
Protein Folding

• Some proteins fold spontaneously into their
  correct 3-dimensional shape
• Some proteins need chaperone proteins to fold
  correctly

43
Nucleic Acids

• Functions
• Contain genetic information (DNA and RNA)
• Some nucleotides used for energy storage ATP
• Some nucleotide used as signal transduction
  cAMP, cGMP

44
Nucleic Acids

• Structure
• Subunits nucleotides
• 3 building blocks for each nucleotide
• Sugar
• Phosphate
• Nitrogenous base

45
Nitrogenous Bases

• 2 types
• Pyrimidines, single ring
• Purines, 2 rings
• Differ in functional groups attached to the rings

46
Sugars and Phosphates

• 5 carbon sugars
• Ribose in RNA (ribonucleic acid)
• Deoxyribose in DNA (deoxyribonucleic acid)
• Phosphate groups link nucleotides together
  phosphodiester bond

47
Formation of Nucleic Acids

• Linked by dehydration condensation
• Bond is called a phosphodiester linkage

48
Nucleic Acid Structure
49
DNA Structure
50
Key Concepts

• 4 building blocks lipids, sugars, amino acids,
  nucleotides
• Functional groups determine chemistry
• Dehydration reactions link small molecules
• Protein shape is determined by R-groups