21. B. recessive
22. D. DD and dd
23. D. FF and ff
The correct answers are:
2) Peptide bonds form from nucleophilic attack by an electron pair on an alpha - amino nitrogen atom on an alpha - carboxyl carbon atom of another amino acid and
4) Peptides are polymers of amino acids.
A peptide bond is an amide type of covalent chemical bond. It is formed between two amino acids: C1 (carbon end) of one alpha-amino acid and N2 (nitrogen end) of another. Peptide bonds are the basis for the formation of a peptide chain and consequently protein. Formation of peptide bond is a condensation process, meaning that when two amino acids combine and link, water molecule is released and dipeptide is a product of that reaction.
Answer;
-Bone tissue becoming stronger.
The mechanical stress applied to bones during moderate physical exercise leads to bone tissue becoming stronger.
Explanation;
-Bones and muscles both become stronger when muscles push and tug against bones during physical activity.Swimming and bicycling are not weight-bearing activities, so they do not directly help build bones. But swimming and bicycling do help build strong muscles, and having strong muscles helps build strong bones.
-Weight-bearing physical activity causes new bone tissue to form, and this makes bones stronger. This kind of physical activity also makes muscles stronger. Bones and muscles both become stronger when muscles push and tug against bones during physical activity.
Latitude and ocean currents are the ones i know.
