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Sugars. Polysaccharides. Fatty acids. Fats/lipids/Membranes. Amino acids. Proteins. Nucleotides. Nucleic acids. Small organic molecules are the building blocks of biological macromolecules …. Building blocks. Larger units. Adapted from ECB figure 2-15 (Garland Publishing).

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small organic molecules are the building blocks of biological macromolecules

Sugars

Polysaccharides

Fatty acids

Fats/lipids/Membranes

Amino acids

Proteins

Nucleotides

Nucleic acids

Small organic molecules are the building blocks of biological macromolecules…

Buildingblocks

Largerunits

Adapted from ECB figure 2-15 (Garland Publishing)

fatty acids

Hydrophilic

Carboxylic acid

head group

Hydrophobic

hydrocarbon

tail

Fatty Acids

(Amphipathic)

fatty acids are distinguished by chain length and double bonds

Stearic acid

18 carbons

Saturated = no double bonds

Oleic Acid

(common in fats)

18 carbons

Unsaturated 1 double bond,

(common in oils)

Fatty acids are distinguished by chain length and double bonds
most lipids in cells are formed by covalent bonds between fatty acids and glycerol
Most lipids in cellsare 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

phospholipid bilayer

Phospholipid

Hydrophilic

region

PhospholipidBilayer

Hydrophobictail region

lipid bilayer forms sphere in aqueous solution
Lipid bilayer forms sphere in aqueous solution

Forms barrier defining

inside and outside spaces

cell membrane more complex

Outer leaflet

Lipids

Inner

leaflet

Protein

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

three types of membrane lipid molecules all amphipathic

Glycolipids

(sugar lipid)

Phospholipids

Sterols (cholesterol)

serine

Three Types of Membrane Lipid Moleculesall amphipathic

ECB 11-7

galactocerebroside

phosphatidylserine

lecture 4
Lecture 4

Membranes

Fatty Acids

Phospholipids

Lipid bilayer

Other membrane lipids

Membrane properties

Proteins

Amino Acids

Peptide bond

Protein Structure

influence of fa saturation on lipid bilayer order

less ordered

ordered

Saturated straight

hydrocarbon chains

(no double bonds)

Unsaturated

hydrocarbon chains

(with double bonds)

Influence of FA saturation on lipid bilayer order

Less ordered state increases membrane fluidity

membrane fluidity viscosity

Gel state

Movement is greatly restricted (crystalline gel)

Liquid state

Hydrophobic tails free to move

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

membrane fluidity is governed by fa length and saturation

Melting points of 18-carbon Fatty Acids

Fatty Acid

Double bonds

Melting point (˚C)

Stearic acid

0

70

Oleic acid

1

13

2

-9

a-Linoleic acid

Linolenic acid

3

-17

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.

cholesterol stiffens lipid bilayers

Polar head

group

Rigid

Planar

Steroid

ring

Nonpolar

hydro-

carbon

tail

Polar head

group

Stiffened

region

Fluid

region

Cholesterol stiffens lipid bilayers

ECB 11-16

Mainly in animal cells,

Not in plants

slide17

1. Spin (fast)

2. Lateral

movement

(less fast)

3. Flip-flop

Almost never

lipid bilayer permeability

Small hydrophobic

Molecules

O2, CO2, N2, benzene

Lipid Bilayer Permeability

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

cell membrane
Cell membrane

ECB Fig. 11-4

Have discussed lipid bilayer, cholesterol, glycolipid

Now move on to proteins

slide20

Sugars

Polysaccharides

Fatty acids

Fats/lipids/Membranes

Amino acids

Proteins

Nucleotides

Nucleic acids

Small organic molecules are the building blocks of biological macromolecules…

Buildingblocks

Largerunits

Adapted from ECB figure 2-15 (Garland Publishing)

proteins serve many functions in cells
Proteins serve many functions in cells

Transport proteins - move molecules across membranes

Enzymes

Structural proteins

Motor proteins

Signaling proteins

Gene regulatory proteins

Etc.

amino acids the building blocks of proteins
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

amino acid groups

Polar Amino Acids

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)

polar charged amino acids 5

Negative charge

Aspartic

Acid (Asp, D)

Glutamic

Acid (Glu, E)

Positive charge

Histidine

(His, H)

Lysine

(Lys, K)

Arginine

(Arg, R)

Polar Charged Amino Acids (5)
polar uncharged amino acids 5

Serine

(Ser, S)

Threonine

(Thr, T)

Asparagine

(Asn, N)

Glutamine

(Gln, Q)

Tyrosine

(Tyr, Y)

Polar Uncharged Amino Acids (5)
non polar amino acids
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)

non polar amino acids cont d

Glycine

(Gly, G)

Proline

(Pro, P)

Cysteine

(Cys, C)

Non-polar amino acids (cont’d)
polymerization of amino acids to proteins

+

H2O

Peptide bond

Polymerization of Amino Acids to Proteins

Condensation rx

Carboxyl

end

Amino

end

Dipeptide

See also ECB figure 5-1

lecture 429
Lecture 4

Membranes

Fatty Acids

Phospholipids

Lipid bilayer

Other membrane lipids

Membrane properties

Proteins

Amino Acids

Peptidebond

Protein Structure

4 levels of protein structure

1˚ structure: the linear sequence of amino acids

N-terminal to C-terminal

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

higher levels of organization are determined by protein folding

Tertiary

structure

quaternary

structure

Secondary

structure

Higher levels of organization are determined by protein folding
improper protein folding is associated with disease
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

secondary structure
Secondary Structure

a-helix and b-pleated sheet

helix

H bond

C

O

H

N

helix

R groups are on outside of helix

H bond

between peptide

bonds, 4 a.a. apart

tertiary structure

Disulfide bond formation (between cysteine residues)

Tertiary Structure

3-D conformation of a singlepolypeptide chain

Driven by many types of bonds (H-bonds, hydrophobic interactions, van der Waals, etc.)

folding into tertiary structure forms domains in polypeptide
Folding into tertiary structure forms domains in polypeptide

Two different domains

Single domain

Polypeptide made up of several domains

quaternary structure

Disulfide bridge

Quaternary structure

Multiple polypeptides interact via noncovalent and covalent

(disulfide) bonds

tetramer

dimer