Download Proteins and Amino Acids: Function Follows Form

Proteins and Amino Acids:
Function Follows Form
BIOL 103, Chapter 7-1
Today’s Topics
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Why is Protein Important?
Amino Acids are building blocks of proteins
Functions of Body Proteins
Protein Digestion and Absorption
Proteins in the Body
Why is Protein Important?
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A part of every cell
Needed in thousands of chemical reactions
Keep us “together” structurally
In short, proteins have many, many functions
from replacing skin cells, producing antibodies
to assisting in nutrient transport and muscle
contractions.
Food Sources of Proteins
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Beef
Chicken
Fish
Milk
Plant foods: beans, peas,
grains, nuts, seeds, and
vegetables (garlic, green
peas, mushrooms)
Amino Acids are Building Blocks of
Proteins
• Proteins are sequences of amino acids
• There are _____ amino acids:
1. _______________________ (9)
2. _______________________ (11)
3. _______________________ (6)
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Amino acids that are normally dispensable, but
become indispensable under certain circumstances
such as during critical illness.
• Table 7.1 List of Amino Acids
Amino Acids Identified by Side Chains
• Identified by side chains
– Made up of: _____________________________
– _____________ gives AA its identity
Protein structure: unique 3D shapes
and functions
• Amino Acid Sequence
– Amino acids are linked by ______________:
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Dipeptide: ____ amino acids
Oligopeptide: _____amino acids
Polypeptide: _____ amino acids
Protein: ___________________________________
– Protein shape
• A sequence of AA determines protein _____________
• Shape of protein determines its __________________
Protein Denaturalization: Destabilizing
a Protein’s Shape
• There are factors that can cause
a protein to unfold and lose
shape (denature)
1. Changes in Acidic or Alkalinity in
environment
2. _____________________
3. Alcohol
4. _____________________
• Denatured proteins lose _____
_________________________
– e.g. egg protein, avidin
Functions of Body Protein
1. ___________________________________
– _______________: fibrous protein found in bones,
teeth, connective tissue, blood vessel structure.
– _______________: water-soluble fibrous proteins
found in hair, nails, and outer layer of skin.
– _______________: proteins that use energy and
convert it to mechanical work (e.g. muscle
contraction, cell division, sperm movement)
2. ___________________________________
– _______________: infection-fighting protein
molecules that tag, neutralize, and help destroy
bacteria/viruses or toxins.
Functions of Body Proteins
3. ________________
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Catalyze (speed up) chemical reactions
4. ________________
– “chemical messengers”
– Regulate ______________
5. ________________
– Proteins as _____________________ by picking up H+
or donate H+
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Too acidic/low pH: Acidosis
Too basic/high pH: Alkalosis
Functions of Body Proteins
6. _____________________
– ____________________ (e.g. active transport)
– ____________________ (e.g. lipoproteins)
7. ____________________________
– Fluids inside (intracellular), between (interstital),
and outside (intravascular) of body cells must be
balanced.
– If diet lacks proteins ___________________
____________________ _______________
Functions of Body Proteins
8. __________________________________
– Although your body prefers using fat and
carbohydrates, if necessary, your body will break
down protein  ___________________
– Protein can be broken down for energy:
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Removes nitrogen from amino acids so that only
carbon skeleton is left.
Protein Digestion
• Protein digestion
– Cells produce proteases (protein-digesting
enzymes) as proenzymes (inactive forms of
enzymes)
– In the stomach:
• Proteins are denatured by ____________
• Pepsin begins digestion: _____________ of proteins
• Which one is a protease? A proenzyme?
Protein Digestion and Absorption
• In the small intestine:
– ____________ (from pancreas) break down
remaining proteins  _______________
– ________________ break down small peptides 
_________________________
– Amino acids are then absorbed into your
_________________  travel via portal vein to
___________________  released to
_____________________
Undigested Proteins
• If not digested, continues down the GI tract 
_________________
• Diseases of the intestinal tract cause problems
with digestion/absorption of proteins
1. Celiac disease: _________________________
2. Cystic fibrosis: ______________ prevents
digestive enzymes (e.g. proteases) from reaching
small intestine  __________________ 
nutrients are not absorbed  malnutrition
Proteins in the Body
• Protein Synthesis:
– Draws on AA pool as needed. If your body is
missing…
• Non-essential AA:
• Essential AA:
Proteins in the Body
• Amino Acid Pool and Protein Turnover
– Cells in your body constantly build and breakdown
proteins  ______________________________
• ____________________: because we are always
recycling our proteins, we need so little protein in our
diet!
– When cells make proteins, they use amino acids
from ______________________ : available amino
acids in body tissues and fluids that can be used to
make new proteins.
Proteins in the Body
• Synthesis of nonprotein molecules
– Proteins are precursors of ___________________
______________
• Protein and Nitrogen Excretion
– Breakdown of amino acids by removing ________
_ ________________
– Amino groups converted to ___________
– Urea + water = _________  excretion (in kidney)
Nitrogen Balance
• We can evaluate our nitrogen balance to evaluate what is
happening in our body
– Nitrogen intake vs. nitrogen output
• Nitrogen equilibrium
– Nitrogen intake _____ nitrogen output
– ______________________________________
• Positive nitrogen balance
– Nitrogen intake _____ Nitrogen output
– ______________________________________
• Negative nitrogen balance
– Nitrogen intake _____ Nitrogen output
– ______________________________________