What is the defining characteristic of an allosteric protein?
A. They contain two polypeptide chains, with each being an exact mirror image of the other.
B. They contain only one ligand-binding site, but because the specificity is low, many different ligands can bind to it.
C. They contain two ligand-binding sites, one that activates the protein when a ligand binds, and the other that inactivates the protein when the same ligand binds.
D. They contain more than one ligand-binding site, and noncovalent binding of a ligand to one site alters the shape of other ligand-binding sites.
E. They contain no binding sites of their own, but act by modulating the activity of other proteins.
D
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Which of the following vessels supplies 80% of the cerebrum with oxygenated blood?
A. Superficial temporal artery B. Occipital artery C. Middle cerebral artery D. Anterior cerebral artery E. Internal carotid artery
Active immunity is a natural process, whereas passive immunity is generated artificially.
Answer the following statement true (T) or false (F)
__________ of a population occurs when environmental stressors favor survival of certain genotypes, leading to their increased levels of reproduction
Fill in the blank with correct word
________ increase surface area to facilitate absorption of extracellular materials
A) Microvilli B) Cilia C) Centrioles D) Endoplasmic reticulum E) Mitochondria