Proteins Flashcards
proteins functions
enzymes
defensive (antibodies)
hormonal and regulatory (physiologial processes)
Receptor (receive and respond to molecular signals)
storage
structural
transport
genetic regulatory
chemical structures
polypeptide chain
chains folded into 3D shapes defind by amino acid sequence
structural formula
HN3+ - C - COO-
C attached to R and H
C is an alpha carbon
which two isomeric forms do amino acids exist in
D amino acids (right)
L amino acids (left) - in organisms
methionine functions
initiates chains of amino acids
Proline
causes kinks in chains of amino acids
Cysteine
links amino acid chains together
Disulphide bridges
Terminal SH of cysteine react with another cysteine to form disulphide bridge
needed for protein folding
How do the amino acids bond together
covalently in a condensation reaction by peptide bonds
peptide bond is inflexible = no rotation
What is the protein primary structure
amino acid sequence
alpha helix protein secondary structure
right handed coil resulting
H2 bonding between N-H groups on one amino acid and C=O groups on another
beta pleated sheet protein secondary structure
two or more polypeptide chains are aligned
H2 bonding from between chains
tertiary structure of proteins
contains beta pleated sheet, alpha helix, h2 bonding and disulfide bridge
folded
what is tertiary structure determined by
- Disulfide bridges
- Hydrogen bonds
- Aggregation of hydrophobic side chains
- van der Waals forces
- Ionic bonds
what conditions affect secondary and tertiary structure
High temperature
* pH changes
* High concentrations of polar molecules
* Nonpolar substances
potential energy
stored energy
chemical bonds, conc gradient, charge imbalance
metabolism definition
sum total of all chemical reactions in an organism
anabolic reactions def
complex molecules made from simple molecules, energy input is required
catabolic reactions
complex molecules broken down to simpler ones and energy released
what principles affect biological energy transformations
law of thermodynamics
understand how cells harvest and transform energy
What is the first law of thermodynamics
enegry is neither created nor destroyed
second law of thermo
energy converted from one form to another, some energy unavailable to do work
no energy transformation is 100% efficient
(some energy is not usable)
what is entropy
chaos and disorder in a system
takes energy to impose order on system, unless energy applied to system it will be disordered
equation for figuring out total energy
total energy = usable energy + unusuable energy
gibbs equation
ΔG = ΔH – TΔS
* If ΔG is negative, free energy is released
* If ΔG is positive, free energy is consumed
* If free energy is not available, the reaction does not occur.
exergonic vs endergonic
exergonic = reactions release energy (–ΔG)
endergonic = reactions consume free energy (+ΔG)
Exergonic and endergonic reactions on graph
Ex = reactions and products, S shape curve from high to low (energy released)
En = low to high (energy gained)
three mechanisms used for enzymes to work
Orientation
physical strain
chemical change
of the substrate
orientation
enzymes orient substrate molecules, bringing together the atoms that will bond
Physical strain
enzymes stretch the bonds in substrate molecules, making them unstable
chemical charge
enzymes can temporrily add chemical groups to substrates
what is a lysozyme
enzyme found in egg white, saliva and tears
acts as antibiotic because it catalyses the cutting of polysaccharide chains in bacterial cell walls so they rupture
what reaction does lysos=zyme catalyse
hydrolysis reaction = forms water
that is spontaneous but not instantaneous
how are enzyme reactions organised
metabolic pathways that are interconnected
maintaining internal homeostasis
feedback inhibition
final products from metabolic pathways act as a noncompetitive inhibitor of the first enzyme which shuts down the pathwya
how to figure out optimal temp and maximum rate of graph
maximum rate is height of peak
optimum temp = reaction rate is 0 line directly below curve
what are ribozymes
enzymes are proteins
ribozymes are made from rna
forms cleaved mRNA
