Apotassium-40 sample starts with 50 atoms, and 1.25 billion years later, there are 25 atoms. what is the half life of potassium-40?

a. 25 years
b. 40 years
c. 1.25 years
d. 2.5 years

Match the descriptions / definitions with the term they best describe 1. three dimensional relationship of the different polypeptide chains in a multisubunit protein or protein complex 2. common folding pattern in proteins in which a linear sequence of amino acids folds into a right-handed coil stabilized by internal hydrogen-bonding between polypeptide backbone atoms. 3. the amino acid sequence of a protein 4. a region on the surface of a protein that can interact with another molecule through noncovalent bonding. 5. three-dimensional arrangement of alpha-helices and beta-sheets within a single polypeptide, typically stabilized by a variety of noncovalent bonds, including ionic and hydrogen bonds, and nonpolar interactions / hydrophobic force. 6. the chain of repeating carbon and nitrogen atoms, linked by peptide bonds, in a protein. 7. common structural motif in proteins in which different sections of the polypeptide chain run alongside each other and are joined together by hydrogen bonding between atoms of the polypeptide backbone. 8. portion of a polypeptide chain that has a discrete tertiary structure of its own and can often fold independently of the rest of the chain 9. regular local folding patterns in a protein, including alpha-helix and beta-sheet a. primary structure b. beta-sheet c. protein d. coiled-coil e. polypeptide backbone f. secondary structure g. side chain h. tertiary structure i. binding site j. alpha-helix k. quaternary structure l. protein domain

Which organelles are labeled d, and what is one feature that distinguishes them from the other labeled organelles chloroplasts the only organelles that produce sugars from sunlight mosomes, only found in animal and bacterial cells centricles only found in animal cells mitochondra, the only energo-generating structures found in cells

What organ systems are working to you cool down after a workout?