Download Protein: A polymer of amino acids Amino Acid Structure

9/29/2014
}
Greek word meaning “of first importance”
◦ Most versatile molecule in the body
}
Protein: A polymer of amino acids
◦ Monomer: 1 of 23 different amino acids
◦ Polymer: String of many monomers
◦ Different combinations of amino acids = different
proteins
}
Amino Acid Structure
◦ Contains an Amino Group (NH2)
◦ Contains an Acid Group (COOH)
◦ Vary only by the R Group
1
9/29/2014
1.
2.
Primary Structure
– Linear Amino Acid Sequence
Secondary Structure
– Coiled or folded shape held together by hydrogen
bonds
◦ Most common secondary structures are:
– Alpha helix – spring like shape
– Beta helix – pleated, ribbon-like
– Functional Conformation = 3 dimensional shape
3.
Tertiary Structure: Further bending and
folding of proteins into globular or fibrous
shapes
–
Globular proteins – compact tertiary structure well
suited for proteins that must move around freely
–
–
–
–
4.
EX: Hemoglobins
Fibrous proteins – slender filaments better suited for
roles such as muscle contraction and strengthening
the skin.
EX: collogen - most abundant protein in body
(connective tissue)
Keratin – supports hair and skin
Quaternary Structure:
◦ Association of 2 or more separate polypeptide
chains
◦ Gives protein their mature (and functional) shapes
2
9/29/2014
}
Conformation: unique 3-dimentional shape
of a protein
– Crucial to function
◦ Have the ability to reversibly change their
conformation
– Enzyme Function
– Muscle Contraction
– Opening and Closing of cell membrane pores
}
}
Denaturation: Destroy
Renaturation: Rebuild
– Extreme conformational change that destroys function
– Ex: Heat, pH, Salinity concentrations
Due on Friday, October 3
3
9/29/2014
1.
◦
◦
2.
◦
◦
3.
◦
◦
Provide Cell Structure
EX: Keratin: tough structural protein. Give
strength to hair, nails, and skin surface
EX: Collagen: durable protein contained in deeper
layers of skin, bones, cartilage, and teeth
Communication of Cell
EX: Protein hormones and other cell-to-cell
signals
EX: Receptors: signaling molecules bind to R’s
Membrane Transport
EX: Channels: in cell membrane that governs
input/output
EX: Carrier proteins: transports solute particles to
other side of membrane
–
4.
◦
Turns nerve and muscle activity “On” or “Off”
Catalysis
EX: Enzymes
4
9/29/2014
5.
6.
7.
◦
◦
◦
Recognition and Protection
Ex: Immune recognition, antibodies, clotting
proteins
Movement
EX: motor proteins: molecules with the ability to
change shape repeatedly (myosin and actin
filaments are responsible for muscle contraction)
Cell Adhesion
–
–
}
Proteins that bind cells together
Immune cells bind to cancer cells and “hangs on”
until a machrophage can destroy it
Keeps tissues from falling apart
Enzymes: proteins that function as biological
catalysts
◦ Permits reactions to occur rapidly at normal body
temperature
◦ How? By lowering activation energy needed to get
reaction started
}
}
}
Substrate: substance an enzyme acts upon
Naming: named for substrate with –ase as the
suffix (EX: amylase enzyme digests amylose
(starch))
Protease? Lipase?
5
9/29/2014
}
Reusability of Enzymes
}
Astonishing speed
◦ Enzymes are not consumed by the reactions
◦ One enzyme molecule can consume millions of
substrate molecules per minute
6
9/29/2014
}
Factors that affect Enzyme Function
◦ pH, salinity, and temperature
}
What happens?
◦ Alters or destroys the ability of the enzyme to bind
to substrate
◦ Enzymes work in optimum pH
– Salivary amylase works best at pH 7.0 (saliva is
between 6.5 and 7.5)
– Pepsin woks best at pH of 2.0 Where?
◦ Temperature optimum for human enzymes = body
temp (37° C)
}
}
Act as biological catalysts
Increase the rate of chemical reaction
7
9/29/2014
}
Inorganic “partners” of enzymes
◦ About 2/3 of human enzymes require a nonprotein cofactor
◦ EX: Iron, Copper, Zinc, Magnesium, Calcium ions
– Many cofactors are “trace elements”
}
What do cofactors do?
◦ Some bind to enzymes and induce a change in
shape = activates the active site
}
Organic cofactors derived from H2O soluble
vitamins
◦ EX: Riboflavin (FADH) and Niacin (NAD+)
– NAD+ is used in making some ATP
◦ Accept electrons from an enzyme in one metabolic
pathway and transfer them to an enzyme in another
8