5-mastering biology

an enzyme speeds up a reaction by lowering the ___.

activation energy

an enzyme is specific because the shape of its __________ matches only particular reactants.

active site

utah's great salt lake had an average salinity 7 times higher than that of the oceans. very few multicellular organisms live in this harsh environment. ex; brine shrimp must donate a large portion of its metabolic energy to osmoregulation. this brine shrimp must ___.

actively pump water back into their cells to counter its loss due to osmosis

cells a & b are the same size and shape, but cell a is metabolically quiet and cell b is actively consuming oxygen. oxygen will diffuse more quickly into cell ___ because ____ .

b; the diffusion gradient there is steeper

an enzyme is considered a ___ because it speeds up chemical reactions without being used up.

catalyst

the ___ between an active site and its substrate often strains bonds and helps the reaction succeed.

co-enzyme

azt is an antiretroviral drug used in the treatment of hiv. it shares a structural similarity to a nucleotide. what might be the mode of action of this drug?

competitive inhibition

high temperatures or changes in pH can ___ an enzyme, causing it to lose its shape.

denature

a nursing infant is able to obtain disease-fighting antibodies, which are large protein molecules, from its mothers milk. these molecules probably enter the cells lining the baby's digestive tract via ___.

endocytosis

why doesn't the antibiotic penicillin harm humans?

human cells do not have cell walls.

a plant cell placed in a ___ solution will lose water and plasmolyze

hypertonic

there is a net diffusion of water out of an animal cell when it is placed in a ___ solution

hypertonic

an animal cell placed in a ____ solution will gain water, swell, and possibly burst

hypotonic

the ideal osmotic environment for a plant cell is a ___ environment

hypotonic

endocytosis moves a material ___ a cell via ___.

into; membranous vesicles

a plant cell surrounded by a __ solution will be flaccid (limp)

isotonic

the ideal osmotic environment for a animal cell is a ___ environment

isotonic

in a catalyzed reaction, a reactant is often called a ___.

substrate

you can recognize the process of pinocytosis when ___.

the cell is engulfing extracellular fluid