1. Proteins!

2. Learning Targets
Amino acids are linked together by condensation reactions to form polypeptides
There are 20 different amino acids used in polypeptides synthesized by ribosomes
Amino acid sequence is coded for by genes
Draw a generalized amino acid
Draw molecular diagrams to show the formation of a peptide bond

3. What are proteins?
Proteins are biological macromolecules that carry out a large number of tasks within organisms. They catalyze metabolic reactions, replicate DNA, transport materials, and help an organism respond to stimuli. Basically, whenever you ask the question, “Wow, what molecule does that?” the answer is a protein.

4. Amino Acids and the Proteins they Build
Proteins are polymers of amino acids.
Proteins form very specific shapes, depending on the order of amino acids in the polypeptide chain that make up the protein.
It is the shape of the protein that determines its function
A third group of biomolecules are proteins. Proteins are polymers of amino acids.
Proteins form very specific shapes, depending on the order of amino acids in the polypeptide chain that makes up the protein. It is the shape of the protein that determines its function.

5. Amino Acids: the monomers of proteins
#MustMemorize

6. Amino Acids all have the same basic structure

7. The 20 amino acids

8. Molecule building!
Every student build an amino acid! Everyone at your table must build a different amino acid. Use your resources to look up the structures of different R groups

9. Proteins are long chains of amino acids
A “polypeptide” – long chain of amino acids

10. Proteins are constructed by way of dehydration synthesis reactions, forming a peptide bond
Just like the other polymers we have looked at so far, amino acids bond together through condensation reactions. The covalent bond that forms between amino acids is called a peptide bond. Here are two amino acids bonding together to form a “dipeptide.”

11. A Dipeptide with a peptide bond
Here is another amino acid being added to the growing chain.

12. A Polypeptide with two peptide bonds and a third one on the way.
Another amino acid is added. This is the formation of a “polypeptide.”
A “polypeptide” – long chain of amino acids

13. Dehydration synthesis
Connect all of the amino acids at your table with a condensation reaction to form peptide bonds

14. Clean up the molecule building kits!
Some atoms may have moved around. Try to make sure that each kit has an equal number of atoms and bonds.

15. Ok, drawing time!
Everyone choose an amino acid, and draw it on a piece of paper. Look at all of the amino acids at your table group Time to connect all of the amino acids at your table! Each person must diagram all of the condensation reactions and show the resulting polypeptide. Indicate the peptide bonds by highlighting them. Raise your hand when you are done so I can check.

16. The many levels of protein structure
primary structure c
tertiary structure
b secondary
structure
A- The polypeptide chain is the primary structure of protein.
B - The polypeptide folds onto itself into either a helix or sheet structure because of hydrogen bonds that form between amino acids. This is its secondary structure.
C- The secondary structure then bends and folds further depending on the characteristics of the “R” groups in the amino acid chain. Some “R” groups are attracted to each other. Some are hydrophic or hydrophillic, so will fold toward or away from the water on the outside. The specific shape it forms is called its tertiary structure.
D- In some proteins (not all), several tertiary structures combine to form a quaternary structure as well.
d quaternary
structure

17. Activity time!
We will now briefly explain the different levels of protein structure with long amino acids sequences and tape.

18. Protein shape is a big deal because…
A protein’s shape is what determines it’s function

19. What level of protein structure ultimately determines the shape of the protein?
Primary!
The specific amino acid sequence is coded for by genes.

20. Enzymes!
Proteins serve many different functions, but one of these is to act as enzymes. Enzymes catalyze (speed up or facilitate) chemical reactions.

21. Here, sucrase catalyzes a hydrolysis reaction and metabolizes sucrose to glucose and fructose.
Proteins serve many different functions, but one of these is to act as enzymes.
Enzymes catalyze (speed up or facilitate) chemical reactions. In this picture, the purple shape represents an enzyme called sucrase. Notice that the shape fits with the molecule sucrose.
(note: enzymes are often named after the chemical reaction they catalyze. Here, sucrase, breaks down sucrose into it’s monomer subunits)
Remember, sucrose is a dissaccharide (composed of one glucose and one fructose covalently bonded together). In order to break apart the covalent bond holding the glucose to the fructose, sucrose “fits” with sucrase. You can see that water is added in this chemical reaction because it is a hydrolysis reaction.
Some enzyme terminology: The molecule that binds to the enzyme is called the substrate (in this case, sucrose).
The site on the enzyme that binds to the substrate is called the active site.

22. Enzymes are a type of protein that acts as a catalyst, speeding up chemical reactions. Here, hexokinase attaches a phosphate to a glucose molecule, trapping it inside a cell.
You can see that the active site on this huge enzyme is relatively small, considering the size of the protein. Glucose and a phosphate group fit inside the enzyme in a way that facilitates the bonding of the phosphate to the glucose molecule.
We will learn more about this enzyme and the importance of this particular chemical reaction when we talk about how our cells use glucose for energy (cellular respiration).

23. Enzymes work by lowering the activation energy of a reaction, allowing it to proceed.
Many chemical reactions can occur without enzymes, but they would occur much more slowly than what is required for the function of processes within your cells and tissues. Therefore, we say that many enzymes catalyze (speed up) reactions by lowering the amount of energy required to get the reaction started, or the activation energy.

24. Enzymes have optimum temperatures and pH at which they work most efficiently.
Remember that our bodies need to maintain homeostasis of pH and temperature. A primary reason why this is necessary is because of all of the enzymes our body needs to function normally.
Remember that enzymes are proteins, and proteins function because of their very specific shapes. If the temperature increases too much, it could cause the hydrogen bonds holding the shape of the protein to break, causing the protein to unravel, or denature.
The same can occur if the environment in which the protein is found is too acidic or too basic. Because enzymes are proteins, therefore, they are very sensitive to changes in pH and temperature.
Here is an interesting thought, however… not all enzymes function best at the same temperature or pH. Look at the graph on the bottom, which shows the level of enzyme activity for three different enzymes. Why do you think Pepsin functions optimally at a much lower pH than salivary amylase?