PLZ HELP ME 1. The positively charged particle in an atom is the

a. neutron. c. proton.

b. ion. d. electron.

2. Two or more different atoms are combined in

definite proportions in any

a. symbol. c. element.

b. isotope. d. compound.

3. A covalent bond is formed by the

a. transfer of electrons. c. gaining of electrons.

b. sharing of electrons. d. losing of electrons.

4. When you shake sugar and sand together in a test

tube, you cause them to form a

a. compound. c. solution.

b. mixture. d. suspension.

5. A compound that produces hydrogen ions in

solution is a(an)

a. salt. c. base.

b. acid. d. polymer.

6. In polymerization, complex molecules are formed

by the joining together of

a. macromolecules. c. polymers.

b. carbohydrates. d. monomers.

8. Proteins are polymers formed from

a. lipids.

b. carbohydrates.

c. amino acids.

d. nucleic acids.

9. An enzyme speeds up a reaction by

a. lowering the activation energy.

b. raising the activation energy.

c. releasing energy.

d. absorbing energy.

10. In a chemical reaction, a reactant binds to an

enzyme at a region known as the

a. catalyst.

b. product.

c. substrate.

d. active site.

Which plains area lies in both the united states and canada? altiplano central canadian shield coastal plains great plains

The first signs of cellular differentiation occur in the blastocyst. why is cellular differentiation important for the development of a fully formed human infant?

Rease is an enzyme used by plants to break down urea (a nitrogen-containing compound) into carbon dioxide and ammonia. urease urea > > > carbon dioxide and ammonia ammonia is broken down by plants into a nitrogen source plants need to grow. thus, plants could not use urea as a nitrogen source unless it was first converted to ammonia. in soybean plants there are two different kinds of urease, one produced in the seeds and the other produced in the leaves of the plant. three types of soybean plants were used in a set of experiments: normal soybeans and two mutant strains, one lacking the urease in the seeds only (strain 1) and one lacking urease in the leaves only (strain 2). experiment 1 separate areas in a field were planted with normal, strain 1, and strain 2 soybeans. all types of soybeans appeared to grow, flower, and produce seeds equally well. there were no externally detectable differences among the strains. experiment 2 small pieces of plant leaves of equal weight were obtained from each type of soybean plant and separately placed on media in culture dishes. tissue growing in this way will become an unorganized clump of cells referred to as callus. to provide a controlled nitrogen source, half the tissue samples of each type were placed on media containing urea, and the other half of the samples were placed on media containing ammonia. after 30 days, the weight gain for each of the callus samples was determined. results are shown in the table below.