Regents Biology Proteins Regents Biology 2006-2007 Proteins: Multipurpose molecules.
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Transcript of Regents Biology Proteins Regents Biology 2006-2007 Proteins: Multipurpose molecules.
Regents Biology
Proteins
Regents Biology 2006-2007
Proteins:
Multipurpose molecules
Regents Biology
Functions of proteins/amino acids:
collagen (skin)
hemoglobin
structural– claws, nails, hair, hooves (keratin), outer layer of skin (collagen)
transport - hemoglobin, cell membrane transport proteins
movement contractile proteins actin & myosin regulatory - hormones catalytic – enzymes that speed up reactions
allowing them to occur immunological – antibodies, antigens on the
exterior of a cell storage of amino acids
Regents Biology
Proteins
Building block =
aminoacid
aminoacid–
aminoacid–
aminoacid–
aminoacid–
—N—H
H
H|
—C—|
C—OH
||O
variable group
amino acids
20 different amino acids
Regents Biology
H
H
N C C
OH
O
H
R
amino group carboxyl group
R group
General structure of an amino acid
(basic) (acidic)
Regents Biology
You do NOT need to know their names!
There are 20 amino acids naturally incorporated into proteins
AlanineArginine
AsparagineAspartic acid
CysteineGlutamic acid
Glutamine
Glycine HistidineIsoleucineLeucineLysine
MethioninePhenylalanine
ProlineSerine
ThreonineTryptophan
TyrosineValine
Regents Biology
Other amino acids do exist…
CH2H
H
N C C
OH
O
H
O
II
II
Thyroxine:used in the human body as a hormone
to regulate metabolic rate
…but are not normally found in proteins
Regents Biology
Humans can synthesis some amino acids by altering other amino acids, however…
…some amino acids cannot be synthesised and are therefore needed in the diet.
These are the essential amino acids
ArginineHistidine
IsoleucineLeucine
LysineMethionine
Phenylalanine
ThreonineTryptophan
Valine
Regents Biology
Regents Biology
Phenylketonuria or Maple Syrup Urine Disease
Patients lack the enzyme phenylalanine hydroxylase – needed to dispose of the amino acid phenylalanine properly
Penylalanine rapidly builds up in the blood stream
- it converted to unusual metabolites which give the patient’s urine a characteristic smell
- it also rapidly causes brain damage!
Treatment: A diet low in phelylalanine
No meat, fish, poultry, eggs, cheese, milk, beans, or peas
Regents Biology
Water-fearing amino acids Hydrophobic
“water fearing” amino acids try to get away from water in cell
the protein folds
Regents Biology
Different amino acids have different R groups
Their different properties depend on their R groups
Hydrophobic (‘Water-hating’) R groups
CH3H
H
N C C
OH
O
H
alanine
CH2H
H
N C C
OH
O
Hphenylalanine (aromatic)
Regents Biology
Water-loving amino acids Hydrophillic
“water loving” amino acids try to stay in water in cell
the protein folds
Regents Biology
Hydrophillic (‘Water-loving’) R groups
CH2H
H
N C C
OH
O
H
SH
cysteine
CH2H
H
N C C
OH
O
H
OH
serine
Regents Biology
Amino acid chains Proteins
amino acids chained into a polymer
Each amino acid is different some “like” water & dissolve in it
some “fear” water & separate from it
amino acid amino acid amino acid amino acid amino acid
Regents Biology
Formation of a dipeptide: carboxyl group of one amino acid reacts with amino group of second amino acid
H2Owater
molecule formed
H
H
N C C
OH
O
H
R2H
H
N C C
OH
O
H
R1
H
H
N C C
O
H
R1 H
N C C
OH
O
H
R2
peptide linkage
a dipeptide
Regents Biology
H
H
N C C
OH
O
H
R1 H
H
N C C
OH
O
H
R2
H
H
N C C
O
H
R1 H
N C C
OH
O
H
R2
H2O
Formation of a dipeptide produces
a molecule of water, therefore…
…this is a condensation
reaction
2 amino acids dipeptide + water
Regents Biology
H
H
N C C
OH
O
H
R1 H
H
N C C
OH
O
H
R2
H
H
N C C
O
H
R1 H
N C C
OH
O
H
R2
H2O
Splitting a dipeptide to form two amino acids consumes one molecule of
water, therefore…
…this is a hydrolysis reaction
dipeptide + water 2 amino acids
Regents Biology pepsin
3-D protein structure
collagen
Proteins fold & twist into 3-D shape that’s what happens in the cell!
hemoglobingrowthhormone
Regents Biology
Its shape that matters! Proteins do their jobs, because
of their shape Unfolding a protein destroys its shape
wrong shape = can’t do its job unfolding proteins = “denature”
temperature pH (acidity) folded
unfolded“denatured”
Regents Biology 2006-2007
Let’s eat some
Proteins!