Nonenzymatic Protein Function and Protein Analysis

Question 1

What is collagen?

Answer 1

contains a trihelical fiber and makes up most of the extracellular matrix of connective tissue and is important for providing strength and flexibility

Question 2

What is elastin?

Answer 2

important component of extracellular matrix of connective tissue; acts like a spring

Question 3

What is keratins?

Answer 3

intermediate filament proteins found in epithelial cells; contribute to the mechanical integrity of the cell and function as regulatory proteins

Question 4

What is actin?

Answer 4

makes up microfilaments and thin filaments in myofibrils

Question 5

What is tubulin?

Answer 5

protein that makes up microtubules

Question 6

What are motor proteins?

Answer 6

display enzymatic activity, acting as ATPases that power the conformational change necessary for motor function

Question 7

What is myosin?

Answer 7

primary motor protein that interacts with actin; acts as thick filament in myofibril, also involved in cellular transport

Question 8

What are kinesins?

Answer 8

play a role in aligning chromosomes during metaphase and depolymerizing microtubules during anaphase of mitosis, important for vesicle transport in the cell - move neurotransmitters toward the synaptic gap

Question 9

What are dyneins?

Answer 9

involved in the sliding movement of cilia and flagella, important for vesicle transport in the cell - reuptake neurotransmitters towards the soma

Question 10

What are binding proteins?

Answer 10

these are proteins that stabilize functions in individual cells and the body and transport or sequester molecules by binding to them

Question 11

What are examples of binding proteins?

Answer 11

hemoglobin, calcium-binding proteins, DNA-binding proteins

Question 12

What are cell adhesion molecules (CAMs)?

Answer 12

proteins found on the surface of most cells and aid in binding the cell to the extracellular matrix or other cells

Question 13

What are cadherins?

Answer 13

a group of glycoproteins that mediate calcium-dependent cell adhesion; hold similar cell types together

Question 14

What are integrins?

Answer 14

a group of proteins that all have two membrane-spanning chains called alpha and beta that help with binding and communicated with the extracellular matrix; also play role in cellular signaling and can greatly impact cellular function by promoting cell division, apoptosis, or other processes

Question 15

What is selectins?

Answer 15

bind to carbohydrate molecules that project from other cell surfaces; expressed on white blood cells and endothelial cells that line blood vessels; host defense

Question 16

What are antibodies?

Answer 16

proteins produced by B-cells that function to neutralize targets in the body, such as toxins and bacteria, and then recruit other cells to help eliminate the threat

Question 17

What keeps the heavy and light chains of antibodies together?

Answer 17

disulfide linkages and noncovalent interactions

Question 18

What is biosignaling?

Answer 18

a process in which cells receive and act on signals; act as extracellular ligands, transporters for facilitated diffusion, receptor proteins and second messengers

Question 19

What is an ion channel?

Answer 19

proteins that create specific pathways for charged molecules

Question 20

What is facilitated diffusion?

Answer 20

the diffusion of molecules down a concentration gradient through a pore in the membrane created by this transmembrane protein (ie ion channel); used for molecules that are impermeable

Question 21

What is an example of an ungated ion channel?

Answer 21

potassium channels which exist in every cells

Question 22

What are voltage-gated ion channels?

Answer 22

gate is regulated by the membrane potential change near the channel

Question 23

What are ligand-gated channels?

Answer 23

the binding of a specific substance or ligand to the channel causes it to open or close

Question 24

What is an example of a ligand-gated channel?

Answer 24

chloride channel that needs GABA to bind to it

Question 25

What is a membrane-spanning domain?

Answer 25

anchors the receptors in the cell membrnae

Question 26

What is the ligand-binding domain?

Answer 26

stimulated by the appropriate ligand and induces a conformational change that activated the catalytic domain which initiates a second messenger cascade

Question 27

What are G protein-coupled receptors?

Answer 27

are a large family of integral membrane proteins involved in signal transduction; characterized by seven membrane spanning alpha helices

Question 28

What is the formula for migration velocity of electrophoresis?

Answer 28

V = E*z/f
E = electric field strength
z = net charge on the molecule
f = frictional coefficient

Question 29

What is polyacrylamide gel electrophoresis (PAGE)?

Answer 29

method for analyzing proteins in their native states; most useful to compare the molecular size or the charge of proteins

Question 30

What is sodium dodecyl sulfate - polyacrylamide gel electrophoresis (SDS-PAGE)?

Answer 30

separates proteins on the basis of size alone. Adds detergent that denatures the protein and neutralizes its charge so only the size affects its movement

Question 31

What is the isoelectric point?

Answer 31

the pI is the pH at which the protein or amino acid is electrically neutral, with an equal number of positive and negative charges

Question 32

What is isoelectric focusing?

Answer 32

proteins that are positively charged migrate to the cathode and proteins that are negatively charged move to the anode; they stop when they reach the portion of the gel where the pH is equal to the pI