Chapter 2: Protein Function

Question 1

Ribozymes

Answer 1

• Catalytic potential of RNA

Question 2

Enzymes

Answer 2

• Accelerate the rate at which cellular reactions proceed
• Lower activation energy
• Increase the rate of metabolic reactions by over 10^17 times
• Accelerate the speed at which equilibrium is reached by increasing the rate of forward and reverse reactions to the same extent
• Minimize production of unwanted side products

Question 3

Proteases

Answer 3

• Classified according to the specific amino acid involved in catalysis at the enzyme active site
• Serine, aspartate, and cysteine identified

Question 4

Zymogenic proenzymes

Answer 4

• Inactive
• Synthesized by serine proteases
• Require limited prtoeolysis for activation

Question 5

Serine proteases

Answer 5

• Important in various processes such as the blood coagulation cascade resulting in clot formation and proteolytic digestion
• Some have preference for particular peptide bonds

Question 6

Myoglobin

Answer 6

• Serves as a high affinity oxygen storage protein in muscle
• Lacks a quaternary structure
• Consists of a single polypeptide chain

Question 7

Hemoglobin

Answer 7

• Composed of 4 globin chains, 2 alphas and 2 betas

- Tetramer with quaternary structure

Question 8

Sickle cell anemia

Answer 8

• Genetic disorder of the hemoglobin structure

- Amino acid primary structure is altered

Question 9

Thalassemias

Answer 9

• Production of the globin chains is reduced or eliminated
• Alpha chains under produced (alpha ***)
• Beta globin chains affected (beta ***)

Question 10

Iron chelation therapy

Answer 10

• Helps manage various forms of thalassemias
• Iron transported in circulation
• Attaches to hepatic glycoprotein (transferrin)
• Transferrin binds to dimeric cell surface receptors, facilitating phosphorylation and internalization
• Iron is released within the cell and transferrin is recycled

Question 11

Transferrin

Answer 11

• Hepatic glycoprotei
• Possesses 2 non-cooperative iron binding sites (Fe3+)
• Binds to dimeric cell surface receptors, facilitating phosphorylation and internalization (in iron chelation therapy)

Question 12

Ferritin

Answer 12

• Can bind to excess iron to be stored in the liver

Question 13

Saturation kinetics

Answer 13

• Movement of molecules across a membrane to increase content on other side

Question 14

Symport

Answer 14

• Two molecules move across membrane simultaneously in one direction

Question 15

Antiport

Answer 15

• Two molecules move across membrane in opposite directions

Question 16

Uniport

Answer 16

• A single molecule moves in one direction across a membrane

Question 17

Collagens

Answer 17

• Strengthens skin and bone
• Fibrous proteins
• Unique structure consisting of 2 helical alpha chains
• Can be 1000 amino residues in length
• Chains wrapped around each other and stabilized by hydrogen bonds

Question 18

Alpha-keratin

Answer 18

• Fibrous protein with simple alpha helical structure

- Rich in hydrophobic amino acids (phenylalanine, isoleucine, and valine)

Question 19

Protofilaments

Answer 19

• Two alpha-keratin chains combine to form a coil that is associated with other coils
• Increase the tensile strength of fibrous structures

Question 20

Antibodies

Answer 20

• Specialized group of proteins that defend the body from attack by harmful antigens
• Can be proteins, nucleic acids, bacteria, or viruses
• Similar Y-shaped structures among them
• Up to 1 x 10^8 produced in human body

Question 21

Antibody structure

Answer 21

• Composed of 2 identical heavy chains and 2 light chains

- Chains are connected by non-covalent and disulfide bonds

Question 22

Receptor proteins

Answer 22

• Bind ligands and mediate cellular responses to external stimuli

Question 23

3 domains of cell surface receptors

Answer 23

• Extracellular ligand-binding
• Transmembrane hydrophobic
• Intracellular

Question 24

Beta 2 - adrenergic receptor

Answer 24

• Serpentine 7-pass receptor protein
• Consists of polypeptide chain that spans the cell membrane 7 times
• Signal transduction is mediated through action of other membrane proteins (G-proteins and adenylate cyclase)

Question 25

Intracellular receptors

Answer 25

• Receptors proteins for hydrophobic steroid hormones and thyroid hormones

Question 26

Growth factors

Answer 26

• Proteinaceous in nature
• Mediate cell growth and development
• Derived from large precursor molecules
• Stimulate cell growth by effecting receptor dimeriazation and autophosphorylation

Question 27

Transcription factors

Answer 27

• Bind non-covalently to selected regions of a cell’s DNA

- Controls selective gene expression and cell differentiation

Question 28

Primary structure review

Answer 28

• This protein state is closely linked with the protein’s function

Question 29

Classification review

Answer 29

• Proteins can be organized on the basis of their function

Question 30

Protein functions review

Answer 30

• Proteins possess catalytic potential and may also serve as transport and storage vesicles
• Crucial for movement, mechanical support, and defense of our bodies
• Integral part of signal transduction

Question 31

Growth factors review

Answer 31

• Play a role in cell division

Question 32

Transcription factors review

Answer 32

• Crucial to gene expression