2. Macromolecules Flashcards
Macromolecules
Huge, highly organized molecules that form the structure and carry out the activities of cells
Macromolecules can be divided into four major categories
- lipids
- carbohydrates
- nucleic acids
- proteins
Carbohydrates, nucleic acids, and proteins are ______
polymers
polymers
composed of a large number of low-molecular-weight building blocks, or monomers
Lipids
a. small, diverse organic molecules that are insoluble in
H2O (polar) but soluble in nonpolar organic liquids
b.hydrophobic (water fearing) or contain significant hydrophobic regions
polar
different parts of the molecule have net negative or positive charge
micelle
an arrangement of lipids in water
soluble
able to be dissolved, especially in water
Biological roles of lips (4)
a) source of NRG in the diet and serve to store NRG in the body
(eg. fats [solid] and oils [liquid])
b) some hormones (chemical messengers) are lipids
(eg. steroids and prostaglandins)
c) many vitamins
(eg. A, D, E)
d) the basic structural elements of biological membranes
(eg. phospholipids-lipid layer on outside, membrane bound)
Lipids:
FATTY ACIDS
- unbranched hydrocarbon chains with a carboxyl group at one end
- chains are typically 14 to 20 carbons
- chain is hydrophobic
- saturated(no double bonds)
- unsaturated(double bonds)
- carboxyl group is hydrophilic
- fatty acids are amphipathic
- they can form micelles in water- note how water is ordered around micelles (all in same orientation)
amphipathic
both hydrophobic and hydrophilic
Carbohydrates
- have general formula (CH2O)n
* includes simple sugars (monosaccharides) and all larger molecules constructed of sugar building blocks
monosaccharides
simple sugars
energy source and source of carbon
polysaccharides definition
very long chains of monosaccharide units
a) energy-storing molecules:
- glycogen in animals cells (usually stored in liver and muscle cells)
- every time a branch breaks off, that is a little bit of energy
- starch in plant cells - non branched
Structural polysaccharides:
Cellulose
- linear polymer of several 100-1000 glucose units
- an insoluble, rigid structural polymer
- makes up cell wall of plants
- plants have cellulase to break down cell wall in order to expand
- we cannot digest links between monomers of cellulose (the bonds differ from those of starch)
- we get no NRG from cellulose
- healthy fiber which helps move things along
glycogen carbon chain is ______
branched
starch carbon chain is ______
spiral
What species can digest cellulose?
cows and termites don’t actually have cellulase (the enzyme that digest cellulose); it is their symbiotic bacteria and protozoa that digest cellulose
Nucleic acids
polymers of nucleotides
nucleotides consist of three units:
- nitrogenous base (ringed structured with N)
- pentose sugar (5 C sugar)
- phosphate group (PO4)
nucleotides are attached to each other through the _________ backbone
sugar-phosphate
nucleotides are involved in 3 major cellular functions
- nucleotides are monomeric units from which DNA and RNA are made (i.e. the molecules that encode the blueprints to life. Informations storage)
- second messengers in cell signalling (eg. cAMP)
- Agents of energy transfer for metabolism
nucleotides are agents of energy transfer for metabolism which does 2 things:
a. cleaving of phosphate groups releases energy (ATP)
b. Co-enzymes in energy transfer reactions (NAD)
(co-enzymes are non-protein compounds needed for enzyme action)
NAD
nicotinamide adenine dinucleotide
Ribonucleic acid (RNA)
- chain of ribonucleotides
-sugar is ribose (5 carbon ring)
-usually single stranded (not always)
even though it is single stranded, it can have 3 dimensional structure; it folds over and bases can pair with each other
RNA has 4 nitrogenous bases:
adenine
guanin
cytosine
uracil
Deoxyribonucleic acid- DNA
-Chain of deoxyribonucleotides
-sugar is deoxyribose (O atom is missing at the C2 carbon) missing a hydroxyl group which RNA has
refer to slide 2 page 11
DNA has 4 nitrogenous bases
Adenine
cytosine
guanine
thymine (instead of uracil)
DNA is double stranded:
-DNA is a double-stranded helix
-two strands held together by H bonds between bases
-H bonds are between complementary pairs of purines and pyrimidines
-pairing rules: a-t
g-c
purines
adenine and guanine
pyrimidines
thymine and cytosine
Overview of Proteins
- Consist of one or more polypeptide chains
- a polypeptide is a polymer of amino acids linked together by peptide bonds
- our cells may have as many as 10,000 different proteins
- proteins have a diverse array of functions
without co-enzymes, enzymes would work ________________.
very slow or not at all
General functions of proteins (8)
- enzymes- protein catalysts
- structural elements- cytoskeleton=framework
- contractile elements-movement
- control activity of genes-genes being interpreted by proteins (transcription factors )
- transport material across membranes
- carriers- bind to whatever its meant to carry, if available
- hormones-insulin
- antibodies
Amino Acids
- building blocks of proteins
- organic acids that contain an amino group, carboxylic acid group and a R group
R groups - amino acid side chains
R= side chain of variable structure
=any of 20 different groups
-difference is R groups account for different properties of amino acids and proteins
R groups can be broadly classified as:
- polar charged
- polar uncharged
- nonpolar
- R groups with unique properties
Structure of proteins
Primary structure
secondary structure
tertiary structure
quaternary structure
Primary structure
- the sequence of amino acids in a polypeptide
- most polypeptides contain over 100 amino acids
- in a polypeptide chain, amino acids are termed residues
- amino acids joined by peptide bonds
secondary structure
beta sheets or
alpha helices
how to depict secondary structure
alpha helices are represented by helical ribbons
beta sheets as flattened arrows
connecting segments as thin strands
tertiary structure
- The way that regions of secondary structure our oriented with respect to each other
- predominates in globular proteins
- tertiary structure results from side chain interactions
van der waals forces
In physical chemistry, the van der Waals forces (or van der Waals’ interaction), named after Dutch scientist Johannes Diderik van der Waals, is the sum of the attractive or repulsive forces between molecules (or between parts of the same molecule) other than those due to covalent bonds, or the electrostatic interaction of ions with one another, with neutral molecules, or with charged molecules.[1] The resulting van der Waals forces can be attractive or repulsive.[2]
The term includes:
force between two permanent dipoles (Keesom force)
force between a permanent dipole and a corresponding induced dipole (Debye force)
force between two instantaneously induced dipoles (London dispersion force).
Side chain interactions are
Hydrogen bonds
hydrophobic bonds
ionic bonds
disulfide bonds (covalent between two cysteines)
(non covalent bond takes little NRG to break, therefore are weak)
quaternary structure
-multimeric proteins contain several polypeptide subunits
-often the subunits can be independently folded
-quaternary structure is the spatial arrangement of these subunits
(slide 2 page 21)
why is protein structure important?
a protein structure determines its function
Tertiary and quaternary structures can be determined using __________and _________.
x-ray crystallography
nuclear magnetic resonance
subtle changes in a protein’s structure can have a _____ impact on on its ability to ____________ its function within the cell.
huge
perform
Cell _______ modify _________ structures to regulate _________.
routinely
protein
activities
_________can be (are not always) damaging to the proteins structure.
mutations
a changed amino acid can alter a protein’s ability to_______________________.
interact with other molecules
