BIOLOGY 1A03 Chapter Notes - Chapter 3: Peptide Bond, Hydrogen Bond, Amine

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Biology Chapter 3: Protein Structure and Function
Beginning of Life
Theory can be broken down into four steps
o Chemical evolution began with production of small organic compounds
o Simple organic compounds reacted to form mid-sized molecules called amino
acids, sugars and nitrogenous bases
Accumulated in the waters of ancient oceans, forming prebiotic soup
o Mid-sized building block molecules linked to form the types of large molecules
found in cells today (proteins, nucleic acids, complex carbohydrates)
o Life became possible when one of these large, complex molecules acquired the
ability to self-replicate
Functions of Proteins
Function
Protein Type
Role in Cell or Organism
Defence
Antibodies and
complement proteins
Destruction of disease causing viruses and
bacteria
Movement
Contractile proteins and
motor proteins
Moving the cell itself or for moving large
molecules and other types of cargo inside the
cell (Actin and myosin)
Catalysis
Enzymes
Catalyze chemical reactions (salivary amylase)
Signalling
Hormones/Receptor
proteins
Act as signals that help coordinate the
activities of many cells
Receive chemical signals from outside cell and
initiate response
Structure
Structural proteins
Provide support for cells and tissues; form
structures such as hair, feathers, cocoons and
spider webs
Keeps cells flexible and in their normal shape
Transport
Transport proteins
Move substances across cell membrane and
throughout body (haemoglobin)
Origin of Life Experiments
Miller experimented to see if complex organic compounds could be synthesized from
simple molecules present in Earth’s early atmosphere and ocean
Large glass flask containing methane, ammonia and hydrogen, all of which have high
free energy
Connected to a smaller flask by glass tubing; flask held liquid water (ocean)
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o Miller boiled water constantly so water vapour was added to mix of gases in
large flask and as vapour cooled and condensed, it would flow back into small
flask
Miller sent electrical discharges across the electrodes he had inserted into the
atmosphere (lightning)
o Added pulses of intense electrical energy
After some time, the solution in the boiling flask became pink, then red and cloudy
He found large quantities of HCN and H2CO as well as several complex carbon-carbon
compounds and most importantly, amino acids
Results and those of subsequent researchers supported chemical evolution
Other hypotheses included hydrothermal vents and meteorites
Amino Acids
All 21 amino acids have a similar backbone structure
o Central carbon attached to a NH2 functional group, a COOH functional group, a
hydrogen atom and an R group
At pH 7, amino group gains a proton to become NH3+ and carboxyl group loses a proton
to become COO- (zwitterion)
Amino acids with nonpolar side chains cannot form hydrogen bonds with water and
thus are hydrophobic
o Tend to coalesce in aqueous solution
Amino acids with polar or charged side chains interact readily with water and are
hydrophilic
o Dissolve easily in water
Nature of side chain influences chemical reactivity
o R groups consisting of mainly carbon and hydrogen atoms rarely participate in
chemical reactions
Chemical behaviour thus depends primarily on size and shape
o R groups containing hydroxyl, amino, carboxyl or sulfhydryl functional groups are
more reactive
Isomers
Structural isomers
o Same atoms, but differ in order in which covalently bonded atoms are attached
Geometric isomers
o Same atoms, but differ in the arrangement of atoms or groups on either side of a
double bond or ring structure (trans vs. cis)
Optical isomers
o Same atoms, but differ in arrangement of atoms or groups around a central
carbon atom that has four different groups attached (mirror images)
o In cells, only the “left handed” form of amino acids exist
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Document Summary

Theory can be broken down into four steps: chemical evolution began with production of small organic compounds, simple organic compounds reacted to form mid-sized molecules called amino acids, sugars and nitrogenous bases. Moving the cell itself or for moving large molecules and other types of cargo inside the cell (actin and myosin) Act as signals that help coordinate the activities of many cells. Receive chemical signals from outside cell and initiate response. Provide support for cells and tissues; form structures such as hair, feathers, cocoons and spider webs. Keeps cells flexible and in their normal shape. Move substances across cell membrane and throughout body (haemoglobin) Miller experimented to see if complex organic compounds could be synthesized from simple molecules present in earth"s early atmosphere and ocean. Large glass flask containing methane, ammonia and hydrogen, all of which have high free energy.

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