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Proteins
Biology I
Proteins:
Multipurpose molecules
Regents Biology
2006-2007
Proteins
Examples


muscle
skin, hair, fingernails, claws
 collagen, keratin

insulin
pepsin
pepsin
 digestive enzyme
in stomach

insulin
 hormone that controls blood
sugar levels
Biology I
collagen (skin)
Proteins
 Function:

Biology I
many, many functions
 hormones
 signals from one body system to another
 insulin
 movement
 muscle
 immune system
 protect against germs
 enzymes
 help chemical reactions
Proteins
 Building block = amino acids
amino amino amino amino amino
acid – acid – acid – acid – acid

20 different amino acids
H O
H
| ||
—N—
—C—C—OH
|
H variable
Biology I
group
There’s
20 of us…
like 20 different
letters in an
alphabet!
Can make lots of
different
words
Amino acid chains
 Proteins

amino acid
amino acids chained into a polymer
amino acid
amino acid
amino acid
amino acid
 Each amino acid is different
Biology I

some “like” water & dissolve in it

some “fear” water & separate from it
Water-fearing amino acids
 Hydrophobic
“water fearing” amino acids
 try to get away from water in cell

 the protein folds
Biology I
Water-loving amino acids
 Hydrophillic
“water loving” amino acids
 try to stay in water in cell

 the protein folds
Biology I
For proteins: SHAPE matters!
 Proteins fold & twist into 3-D shape

that’s what happens in the cell!
 Different shapes = different jobs
growth
hormone
Biology I
hemoglobin
pepsin
collagen
It’s 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
unfolded
“denatured”
 pH (acidity)
In Biology
it’s the SHAPE
that matters!
Biology I
folded
Let’s EAT some
Proteins!
Biology I
Activities
 demo raw egg vs. cooked egg
drop raw egg into boiling water, like egg
drop soup
 compare raw egg to hard-boiled egg

 demo cheese-making with heated milk

Biology I
& vinegar
make yogurt