Small organic molecules are the building blocks of biological macromolecules

1
Small organic molecules are the building blocks
of biological macromolecules
Building blocks
Larger units
Adapted from ECB figure 2-15 (Garland Publishing)
2
Most lipids are in membranes
3
Fatty Acids
(Amphipathic)
4
Fatty acids are distinguished by chain length and
double bonds
5
Most lipids in cells are formed by covalent bonds
between fatty acids and glycerol
ECB Fig. 11-10
Triacyl Glycerol 3 fatty acids bonded to
glycerol Ester bond - carboxylic acid and
alcohol (animal fat, plant oils) Energy storage
Very Hydrophobic
6
Phospholipid - 3 partsMajor component of
membranes
7
PhospholipidBilayer
Hydrophilic region
Hydrophobic tail region
8
Lipid bilayer forms sphere in aqueous solution
Forms barrier defining inside and outside spaces
9
Cell Membrane-more complex
Contains a variety of lipids, proteins, and
carbohydrates
Lipid bilayer 5 nm
Multiple types of lipids are found in membranes
Cytosol (inside)
ECB Fig. 11-4
10
Three Types of Membrane Lipid Moleculesall
amphipathic
ECB 11-7
galactocerebroside
phosphatidylserine
11
Lecture 4
Membranes
Fatty Acids
Phospholipids
Lipid bilayer
Other membrane lipids
Membrane properties
Proteins
Amino Acids
Peptide bond
Protein Structure
12
Influence of FA saturation on lipid bilayer order
Less ordered state increases membrane fluidity
13
Membrane Fluidity (viscosity)
Describes the physical state of the membrane
Pure lipid bilayer - two states
Transition temperature
Liquid at temperatures Above the transition temp.
Crystalline gel at temperatures below the
transition temp
Living cells require a fluid membrane, but not
too fluid Membrane fluidity is regulated by the
cell
11.2-membrane_fluidity.mov
14
Membrane fluidity is governed by FA length and
saturation
1. Fatty acid length - shorter the FA, the lower
the transition temperature (melting point),
favors liquid state
2. Fatty acid saturation - the more saturated,
the higher the transition temperature, favors gel
state
3. Presence of cholesterol - broadens the
temperature over which transition occurs.
15
Cholesterol stiffens lipid bilayers
ECB 11-16
Mainly in animal cells, Not in plants
16
Lipid composition varies in inner and outer
leaflet
17
(No Transcript)
18
Lipid Bilayer Permeability
Small hydrophobic Molecules O2, CO2, N2, benzene
Small Uncharged polar molecules H2O, glycerol,
ethanol
Large, uncharged Polar molecules Amino acids,
glucose, nucleotides
IONS H, Na, HCO3-, K, Ca2, Cl-, Mg2
ECB Fig.12-2
19
Cell membrane
ECB Fig. 11-4
Have discussed lipid bilayer, cholesterol,
glycolipid Now move on to proteins
20
Small organic molecules are the building blocks
of biological macromolecules
Building blocks
Larger units
Adapted from ECB figure 2-15 (Garland Publishing)
21
Proteins serve many functions in cells
Transport proteins - move molecules across
membranes Enzymes Structural proteins Motor
proteins Signaling proteins Gene regulatory
proteins Etc.
22
Amino Acids - the building blocks of proteins
20 different amino acids
All amino acids have the same backbone, but the
R group varies.
See ECB Fig. 2-21
23
Amino Acid Groups
Based on chemical characteristics of R groups
1. Polar and negative charge (aspartic acid and
glutamic acid)
2. Polar and positive charge (arginine, lysine,
histidine)
3. Polar and uncharged (asparagine, glutamine,
serine, threonine, tyrosine)
4. Nonpolar (alanine, glycine, valine, leucine,
isoleucine, proline, phenylalanine, methionine,
tryptophan, cysteine)
24
Polar Charged Amino Acids (5)
25
Polar Uncharged Amino Acids (5)
26
Non-polar amino acids
(10 total)
Alanine (Ala, A)
Valine (Val, V)
Leucine (Leu, L)
Tryptophan (Trp, W)
Phenylalanine (Phe, F)
Methionine (Met, M)
Isoleucine (Ile, I)
27
Non-polar amino acids (contd)
28
Polymerization of Amino Acids to Proteins
Condensation rx
Carboxyl end
Amino end
Dipeptide
See also ECB figure 5-1
29
Lecture 4
Membranes
Fatty Acids
Phospholipids
Lipid bilayer
Other membrane lipids
Membrane properties
Proteins
Amino Acids
Peptide bond
Protein Structure
30
4 Levels of Protein Structure
2 structure stretches of the polypeptide chain
that fold into a-helix or b-sheet (H-bonding)
3 structure 3-dimensional conformation of a
polypeptide chain
4 structure multiple polypeptide chains
interacting to form a complex
31
1 structure sequence of amino acids
(ECB Fig. 4-2)
32
Higher levels of organization are determined by
protein folding
33
Improper protein folding is associated with
disease
Prion diseases - scrapie (sheep), mad cow
(bovine), chronic wasting disease (deer, elk),
Creutzfeldt-Jacob disease (CJD, humans)
Alzheimers and Huntingtons diseases - aggregated
proteins in brain
34
Secondary Structure
a-helix and b-pleated sheet
35
??helix
R groups are on outside of helix
H bond between peptide bonds, 4 a.a. apart
36
? pleated sheet
37
Tertiary Structure
3-D conformation of a single polypeptide chain
Driven by many types of bonds (H-bonds,
hydrophobic interactions, van der Waals, etc.)
38
Folding into tertiary structure forms domains in
polypeptide
Two different domains
Single domain
Polypeptide made up of several domains
39
Quaternary structure
Multiple polypeptides interact via noncovalent
and covalent (disulfide) bonds
tetramer
dimer