All About Proteins

Question 1

What is a protein?

Answer 1

Macromolecules built from amino acids that provide cells with their shape and structure + perform most of their activities

Question 2

What determines a protein’s function?

Answer 2

Shape and its unique sequence of amino acids (20 types)

Question 3

Describe the structure of a protein.

Answer 3

Protein molecules consist of a polypeptide backbone held together by covalent peptide bonds with attached side chains of amino acids

Question 4

What holds amino acids together to form polypeptides?

Answer 4

Peptide bonds

Question 5

Describe what a peptide bond is.

Answer 5

The carboxyl group of one amino acid binds with the amine group of another amino acid, 1 water molecule is removed to form the bond

Question 6

What effect do hydrogen bonds, Van der Waals interactions, hydrophobic effects, and electrostatic interactions have on proteins?

Answer 6

They stabilize their structure

Question 7

Primary structure of a protein

Answer 7

Sequence of a chain of amino acids

Question 8

Secondary structure of a protein

Answer 8

Alpha helices and beta sheets (folding patterns) form within certain segments of the polypeptide chain

Question 9

How does an alpha helix form?

Answer 9

A single polypeptide chain turns around itself to form a structurally rigid cylinder

Question 10

How do beta sheets form?

Answer 10

Hydrogen bonds form between segments of a chain that lay side by side

Question 11

Tertiary protein structure

Answer 11

3D folding conformation of a single polypeptide chain due to side chain interactions

Question 12

Quaternary protein structure

Answer 12

Protein consisting of 1+ polypeptide chains interacting with one another

Question 13

What is a protein conformation?

Answer 13

The unique 3D structure of a protein based on the location of its atoms relative to one another

Question 14

The folded shape of a protein is done to minimize ____?

Answer 14

Its free energy (G)

Question 15

What is Gibbs Free Energy?

Answer 15

The overall driving force of a reaction, a state function so it’s a quantity not dependent of the path taken just its state

Question 16

Equation relating Gibbs free energy (G), enthalpy (H), and entropy (S)

Answer 16

ΔG=ΔH-ΔTS

Question 17

Types of proteins (5)

Answer 17

enzymes, transporters + carriers, proteins of the immune system, structure proteins, signaling + messenger

Question 18

What are enzymes?

Answer 18

Proteins that catalyze chemical reactions (convert organic substrates into other organic products)

Question 19

Enzyme characteristics

Answer 19

• Active site to which the substrate binds
• Active site has a pocket in the surface of the enzyme that complements the substrates shape
• Lowers the energy requirement of a reaction by stabilizing the transition state

Question 20

What’s a transition state?

Answer 20

Maximum potential energy, unstable intermediate, peak must be overcome for the product to be formed

Question 21

What are transporters and carrier proteins?

Answer 21

Transmembrane proteins used for active transport or facilitated diffusion to help with transport across the cell membrane

Question 22

Examples of carrier proteins (2):

Answer 22

1. Serum albumin - transports water-insoluble lipids through the bloodstream
2. Connexins - component proteins in + form gap junctions

Question 23

Proteins of the immune system (2)

Answer 23

Immunoglobulins and cytokines

Question 24

What are immunoglobulins?

Answer 24

• AKA antibodies
• globular plasma proteins produced by white blood cells

Question 25

Characteristics and functions of immunoglobulins

Answer 25

- Attached to surface of effector B cells or circulate in the blood - Bind to neutralize foreign molecules - Initiate the destruction of pathogens via macrophages

Question 26

Characteristics and functions of cytokines

Answer 26

- Signaling molecules produced by helper T cells - Drive progression of inflammatory processes by recruiting immune cells and macrophages to the site of injury or infection

Question 27

Structure protein example

Answer 27

Collagen - Most abundant protein in humans - Found in tissues providing structural support (bone, cartilage, ligaments)

Question 28

Provide an example of how collagen is used in the body.

Answer 28

- During bone remodeling, osteoblasts build bone by secreting collagen - Osteoclasts breaks down and remove damaged bone

Question 29

Signaling and messenger protein example

Answer 29

Receptor Tyrosine Kinases (RTKs) - Initiate signal transduction when a ligand binds to a receptor on the outside of cells - Triggers proteins inside the cell to initiate autophosphorylation

Question 30

What are kinases?

Answer 30

Enzymes that transfer a phosphate group from a donor to a substrate

Question 31

How can X-ray crystallography be used to visualize protein structures?

Answer 31

- Angles and intensities of beams allow for the reconstruction of a 3D picture of the density of electron with crystals - Gives a 3D structure of crystalized proteins