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Biochemistry Ch. 3 - Nonenzymatic protein function and...
MCAT
29
Biochemistry
Undergraduate 3
03/22/2016

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Term
collagen
Definition
structural protein; has trihelical fiber that makes up most of the extracellular matrix of connective tissue; provides strength and flexiblity
Term
elastin
Definition
structural protein; most important role is to stretch and recoil like a spring
Term
keratins
Definition
structural protein; intermediate filament proteins in epithelial cell; makes up hair and nails
Term
actin
Definition
structural protein; composes microfilaments and thin filaments in myofibrils. Most abundant protein in eukaryotic cells. Has positive and negative end to allow motor proteins to travel along it like one way street
Term
tubulin
Definition
structural protein; makes up microtubules important for chromosome separation in mitosis and meiosis and intracellular transport with kinesin and dynein
Term
myosin
Definition
primary motor protein that interacts with actin and makes up the thick filament in a myofibril. each subunit is a single head and neck that moves during the power stroke of sarcomere contraction
Term
kinesins and dyneins
Definition
associated with microtubules. Each has two heads, one of which is always attached to the microtubule.

Kinesins play a key role in aligning chromosomes during metaphase.
Dyneins are involved in sliding movement of cilia and flagella.

Kinesins and Dyneins move down the microtubules in opposite directions
Term
binding proteins
Definition
bind a specific substrate, either to sequester it in the body or hold its concentration at steady state
Term
What are cell adhesion molecules and what are the three major families?
Definition
Cell adhesion molecules allow cells to bind to other cells or surfaces

-cadherins
-integrins
-selectins
Term
Cadherins
Definition
cell adhesion molecule; mediate calcium dependent cell adhesion and often hold together similar types of cells
Term
integrins
Definition
cell adhesion molecule; have two membrane-spanning chains and permit cells to adhere to proteins in the extracellular matrix. Some also have signaling capabilities. important for WBC migration and anchoring to epithelia
Term
selectins
Definition
cell adhesion molecules; bind to carbohydrate molecules that project from other cell surfaces. Expressed in WBCs and endothelial cells lining blood vessels to grab WBCs for inflammation
Term
What are antibodies and what do they do?
Definition
aka immunoglobulins, made of two heavy and two light chains. Antigen binding region found at tips of the 'Y' and is specific to one antigen.

-neutralize antigen
-opsonize pathogen (mark for destruction)
-Agglutinate, clump together, on the antigen with other antibodies to be phagocytized
Term
ungated channels
Definition
unregulated pores that allow molecules to cross membrane down their gradient
Term
voltage-gated channels
Definition
regulated by the membrane potential and open within a range of potential
Term
ligand-gated channels
Definition
the binding of a specific substance to the channel causes it to open or close
Term
enzyme-linked receptors
Definition
participate in cell signaling through extracellular ligand binding which activates a second messenger cascade
Term
G protein-coupled receptors
Definition
contain 7 membrane spanning alpha helices. The ligand binding to the receptor increases the proteins affinity for a heterotrimeric G protein (GDP and GTP) which activate the receptor and cause a second messenger cascade
Term
electrophoresis
Definition
separates proteins based on size and shape using their charge to move them.
Term
Native PAGE
Definition
polyacrylamide gel electrophoresis (PAGE) separates proteins in their native states based on size and charge. proteins can be recovered
Term
SDS-PAGE
Definition
sodium dodecyl sulfate polyacrylamide gel electrophoresis denatures the proteins and separates them based on mass alone.
Term
isoelectric focusing
Definition
uses a gel with a pH gradient. As the proteins travel along they will become protonated and deprotonated. Once a protein reaches its pI and becomes neutral it will stop moving. Separates on basis of pI
Term
chromatography
Definition
uses a stationary phase and mobile phase. The sample will move through the column based on its affinity for the stationary and mobile phases
Term
column chromatography
Definition
column is filled with beads that separate samples based on polarity and somewhat on size
Term
ion-exchange chromatography
Definition
beads coated with a charge substance are used so they will bind something with the opposite charge. After all the sample as been run it can be eluted by washing the column with a salt gradient
Term
size-exclusion chromatography
Definition
uses beads that contain pores of varying sizes. Smaller proteins will be able to access more pores making them move more slowly. Larger proteins will have access to fewer pores and will run more quickly.
Term
affinity chromatography
Definition
uses bound receptor or ligand on the column beads to bind protein of interest. eluent disrupts binding of protein to column but can sometimes remain bound to the protein and be difficult to remove
Term
Edman degradation
Definition
uses cleavage to sequence proteins of up to 50 to 70 amino acids
Term
How can you determine the concentration of a protein?
Definition
UV spectroscopy, colorimetric changes from assays ie Bradford protein assay
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