Cell Bio: Chapter 4 Flashcards
(45 cards)
What determines protein function?
The 3D structure of the protein and its chemical properties.
What are the four separate levels of protein structure?
Primary, secondary, tertiary and quaternary.
How many amino acids are commonly used to build peptides or proteins?
20.
What four functional groups are attached to amino acids?
A hydrogen, amino, carboxyl and R (side chain) with a central carbon in the middle.
What are the four classes of amino acids?
Acidic, basic, polar, and nonpolar.
What reactions join amino acids together to form new peptide bonds?
Condensation reactions.
What is the primary structure of a protein?
The individual amino acids (linear sequence) of a protein linked with covalent peptide bonds.
Does the primary sequence have a defined polarity?
Yes; listed from the amino (N) terminus with a free amino group to the carboxyl (C) terminus with a free carboxylic acid group.
What does the backbone of the protein include?
The amino groups, central carbons and carboxyl groups.
What are the two common folding patterns arising from regular hydrogen bonding between the N-H and C=O groups?
Alpha helices and Beta sheets.
What does an Alpha helix form?
The transmembrane domain of proteins spanning a lipid bilayer.
What are Beta sheets?
Extended strands with hydrogen bonds holding parallel/antiparallel strands together.
Where are the R groups on the Alpha helices and Beta sheets?
R groups on Alpha helices project out of the backbone. R groups in Beta sheets project above and below its plane.
What is the tertiary structure of a protein?
The 3D structure of its polypeptide chain.
Where are polar and nonpolar amino acids found regarding tertiary structure?
Polar amino acids are charged, and able to interact with the aqueous environment. Nonpolar hydrophobic amino acids are buried in the center of the folded protein.
What stabilizes the tertiary structure of a protein?
Bonds between R groups, and R groups and the backbone including hydrogen, covalent, ionic bonds and Van der Waals forces.
What is a protein domain?
A region of the whole proteins forming an independently folding stable structure.
What is the quaternary structure of a protein?
The complete structure; including multiple polypeptide chain subunits.
What is the active site on an enzyme?
The region of interaction and catalysis.
How do enzymes accelerate the rate of chemical reactions?
By lowering the activation energy, not being changed themselves.
Do enzymes affect the equilibrium of reactions they are catalyzing?
No, they are regulated, and stabilize transition sites.
Why are enzymes regulated?
You don’t want all enzymes working all the time.
What are some ways cells regulate enzymes?
Cofactors, feedback regulation, competitive inhibition, allosteric regulation.
What are cofactors?
Small molecules like heme or ions binding to an enzyme’s active site to help it work.
