Biology 1113: Lecture 4 (proteins)

Question 2

What are proteins made of?

Answer 2

Long strings of amino acids (monomers linked together).

Question 3

How do the type and arrangement of monomers affect proteins?

Answer 3

They determine the molecule’s shape, which in turn determines its function.

Question 4

How many amino acids are used in human proteins?

Answer 4

20 amino acids.

Question 5

What is the basic structure of an amino acid?

Answer 5

A central carbon bonded to:
- A hydrogen atom (H)
- An amino group (NH₂)
- A carboxyl group (COOH)
- A variable R group (side chain).

Question 6

What determines the properties of an amino acid?

Answer 6

Its R group (hydrophilic, hydrophobic, acidic, basic, etc.).

Question 7

What happens to hydrophobic R groups in water?

Answer 7

They cluster toward the protein’s interior.

Question 8

What are the four levels of protein structure?

Answer 8

Primary: Sequence of amino acids.
Secondary: 3D shapes like α-helix and β-pleated sheets formed by hydrogen bonds.
Tertiary: Overall 3D shape formed by interactions between R groups.
Quaternary: Structure formed by multiple polypeptides.

Question 9

What bonds are involved in secondary and tertiary structures?

Answer 9

Secondary: Hydrogen bonds.
Tertiary: Hydrogen bonds, ionic bonds, disulfide bonds, hydrophobic interactions, van der Waals forces.

Question 10

What is a peptide bond?

Answer 10

A covalent bond between the carboxyl group of one amino acid and the amino group of another.

Question 11

What distinguishes proteins, polypeptides, and peptides?

Answer 11

Peptides: Short chains (<50 amino acids).
Polypeptides: Longer chains (≥50 amino acids).
Proteins: Fully functional molecules, sometimes consisting of multiple polypeptides.

Question 12

What happens when a protein denatures?

Answer 12

It loses its 3D shape and function, usually due to heat or chemical changes.

Question 13

List the main functions of proteins.

Answer 13

Structural (e.g., hair, cartilage).
Protection/Defense (e.g., antibodies).
Signaling/Regulation (e.g., hormones).
Movement/Contraction (e.g., muscle proteins).
Transport (e.g., hemoglobin).
Catalysis (e.g., enzymes).

Question 14

What is an enzyme?

Answer 14

A protein that speeds up biological reactions by reducing activation energy.

Question 15

What is the active site of an enzyme?

Answer 15

The location where substrates bind and reactions occur.

Question 16

Why are enzymes specific?

Answer 16

Their active site’s shape and chemical properties match specific substrates.

Question 17

Why is the amino acid sequence important?

Answer 17

It determines the protein’s 3D shape and function.

Question 18

What can a single amino acid change do to a protein?

Answer 18

It can drastically affect the protein’s shape and function, especially if the replacement is dissimilar (e.g., polar vs. nonpolar).

Question 19

How do proteins fold into their functional shapes?

Answer 19

Through interactions between amino acids (e.g., hydrogen bonds, ionic bonds).

Question 20

What are molecular chaperones?

Answer 20

Proteins that help other proteins fold correctly by preventing inappropriate interactions.

Question 21

What causes protein misfolding diseases like prion diseases?

Answer 21

Misfolded proteins that induce other proteins with the same sequence to misfold.

Question 22

What are essential amino acids?

Answer 22

Amino acids that the human body cannot produce and must be obtained through diet.

Question 23

What is a complete protein?

Answer 23

A food containing adequate amounts of all essential amino acids.

Question 24

How can you meet your essential amino acid needs without complete proteins?

Answer 24

By combining complementary foods (e.g., rice and beans).

Question 25

How do enzymes speed up reactions?

Answer 25

By lowering the activation energy required for the reaction.

Question 26

What suffix do most enzymes have?

Answer 26

“-ase” (e.g., lactase, cellulase).

Question 27

What happens if an enzyme is missing or defective?

Answer 27

The reaction it catalyzes cannot proceed (e.g., lactose intolerance).

Question 28

What makes peptide bonds unique?

Answer 28

They are stable and inflexible, giving proteins structural integrity.

Question 29

What are α-helix and β-pleated sheets?

Answer 29

Common shapes in secondary structure due to hydrogen bonding.

Question 30

How does denaturation affect bonds in proteins?

Answer 30

It disrupts weaker bonds (e.g., hydrogen bonds) but not the sequence of amino acids.