Proteins

Proteins

AP Biology

Proteins include a diversity of structures, resulting in a wide range of functions

Proteins

Molecule consisting of polypeptides (polymers of amino acids) folded into a 3D shape

- Comprised of C, H, O, N, and S
- Shape determine function

Monomer: Amino Acids

Molecules that have an amino
group and a carboxyl group

- 20 different amino acids

Amino Acids

○ Unique aspects of the AA are based on the side

chain’s physical and chemical properties

○ Side chains can be grouped as:

■ Nonpolar
■ Polar
■ charged/ionic

Amino Acids

Side chains interact, which determine the shape and function of the protein

Formation of Peptide Bonds

A carboxyl group of one AA must be positioned next to the amino group of another AA

Polypeptides

Many AA linked by peptide bonds

Each polypeptide has a unique sequence of AAs and directionality

- One end is a free amino group called the N-terminus
- One end is a free carboxyl group called the C-terminus

Multiple Choice

How is the unique sequence of AAs determined for a polypeptide?

• genes

• monomers

• DNA

• amino acids

Functions of Proteins

○ Antibody-help protect the body from disease
○ Enzyme- carry out chemical reactions or assist in creating new molecules

○ Messenger- transmit signals (ie hormones)
○ Structural- provide structure and support
○ Transport/storage- bind to and carry small atoms and

molecules through the body

​Primary Structure

Linear chain of AA

• Determined via genes

• Dictates secondary and tertiary forms

Secondary

Coils and folds due to hydrogen bonding within the polypeptide chain

Tertiary

3D folding due to interactions between the side chains of AAs

-Reinforced by hydrophobic interactions and disulfide bridges of the side chains

​R-Groups and their characteristics

Quaternary

Association of 2 or more polypeptides

- Found in only some proteins

Multiple Select

Which of the following element(s) are found in proteins? Click all that apply

• carbon/hydrogen

• oxygen

• phosphorus

• nitrogen

• sulfur

Multiple Choice

Which of the following is the monomer of a protein?

• Amino Acid

• Monosaccharide

• Nucleotide

• Steroid

Multiple Select

Which of the following functional groups is found in all amino acids? Choose two!

• amino

• carboxyl

• hydroxyl

• sulfhydryl

Multiple Choice

Which of the following describes the dehydration reaction of two amino acids?

• Carboxyl group of first amino acid binds with carboxyl group of second amino acid

• Carboxyl group of first amino acid binds with amino group of second amino acid

• R group of first amino acid binds with R group of second amino acid

• Amino group of first amino acid binds with amino group of second amino acid

Multiple Choice

Which of the following bonds is found in the secondary structure of a protein?

• hydrogen

• peptide

• covalent

• ionic

Multiple Choice

Which of the following structures involves the R groups interacting in a single polypeptide?

• primary

• secondary

• tertiary

• quaternary

Multiple Choice

The amino acid glutamic acid has a R group with a negative charge. During folding, which of the following describes the orientation of the R group?

• Exterior of protein due to negative charge providing hydrophilic properties

• Exterior of protein due to negative charge providing hydrophobic properties

• Interior of protein due to negative charge providing hydrophobic properties

• Interior of protein due to negative charge providing hydrophilic properties

Multiple Choice

In terms of directionality of the protein, which of the following provides naming for the side with the amino group?

• A - terminus

• C - terminus

• N - terminus

• S - terminus

Multiple Choice

In terms of directionality of the protein, which of the following provides naming for the side with the carboxyl group?

• A - terminus

• C - terminus

• N - terminus

• S - terminus

Multiple Choice

Which of the following identifies the number of water molecules needed to remove the amino acids from a polypeptide with 20 amino acids?

• 19

• 20

• 21

• 22

Open Ended

1. Cystic fibrosis is a serious, life-threatening disease that affects the lungs and digestive system of affected individuals. This disease results from the deletion of three nucleotides on the Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) gene. This gene codes for a transmembrane protein that regulates ion channels in epithelial tissue. Provide an explanation for how this deletion could result in cystic fibrosis.