U1L6: Proteins and Enzymes

Question 1

What are the characteristics of a protein?

Answer 1

A macromolecule made of amino acid monomers.

Question 2

What is the structure of amino acids (think composition)

Answer 2

made of a central carbon bonded to a carboxyl group, amino group, and an “R” group (can be different atoms/molecules),and an H atom.

Question 3

Amino acids that are non polar have…

Answer 3

R groups that are hydrophobic

Question 4

Amino acids that are polar have…

Answer 4

R groups that are hydrophilic

Question 5

What do proteins contain?

Answer 5

They contain many amino acids and are often amphiphilic (both hydrophobic & philic)

Question 6

What are peptides?

Answer 6

• A polymer of 2 or more amino acids
• Named for the number of amino acids they contain

◦ dipeptides have 2, tripeptides have 3

◦ oligopeptides have fewer than 10 to 15

◦ polypeptides have more than 15

◦ proteins have more than 100

Question 7

What kind of rxn creates a peptide?

Answer 7

Dehydration synthesis creates a peptide bond that joins amino acid

Question 8

What does an amino group do in water?

Answer 8

In solution, the amino group bonds to an H+ while the carboxyl group releases an H+

Question 9

What is the primary structure?

Answer 9

a linear sequence of amino acids

Question 10

What is the secondary structure?

Answer 10

When the amino acids (aa) in a primary structure interact with each via hydrogen bonds, the linear chain coils into an alpha helix or fold into a fan shape (beta pleated sheet)

Question 11

What is the Tertiary Structure?

Answer 11

when continued interactions among R groups of aa and between R groups and water cause the peptide to take on a 3D structure

Question 12

What is the Quaternary Structure?

Answer 12

when multiple polypeptides interact

Question 13

What is protein conformation?

Answer 13

Overall 3D shape is crucial to function - important property of proteins is the ability to change their conformation.

(Example: opening and closing of cell membrane pore)

Question 14

What is protein denaturation?

Answer 14

Its the drastic conformational change that destroys the function of a protein

● occurs with extreme heat or pH

● often permanent

Question 15

What are the protein functions?

Answer 15

Structure (collagen, keratin - maintains hair, fingernails, and skin) Communication (some hormones, cell receptors)

Membrane Transport (form channels, carriers - for solute across membranes)

Catalysis (enzymes are catalysts that speed up the rates of reactions)

Question 16

What do enzymes do?

Answer 16

Enzymes speed up a chemical reaction by lowering the activation energy required for the rxn to proceed.

Question 17

What are Enzyme-catalyzed Reactions?

Answer 17

• Provide alternative pathway of lower activation energy, thus speeding up the rate of the reaction
• Do not undergo permanent change during the reaction, therefore they can be reused
• Very specific to reactions and substrates

◦ Specificity is due to complementary shape, hydrophobic/hydrophylic characteristics (and charge)

Question 18

What are active sites?

Answer 18

Recall that enzymes are proteins (made of amino acids). There are indentations on their surfaces called active sites which have a unique shape that interacts with the reactant (substrate). The substrate joins with the enzyme to form an enzyme-substrate complex.

Question 19

What are the factors that affect the Rate of Enzyme Activity?

Answer 19

• Presence of cofactors (metal ions) and coenzymes (specific helper molecules req’d for enzyme function)
• pH
• Temperature
• Concentration of substrate
• Concentration of enzymes (active sites available)