Honors Biology - Unit 2: Biochemistry Check & Challenges

Page 27:

1. What is the relationship between atoms and elements?

The relationship between atoms and elements is that atoms are the smallest unit of an element that still retains the chemical properties of said element. So, each single atom represents one element. Elements are made up of only one type of atom.

2. What are the particles of an atom and how do they interact?

The smaller subatomic particles of an atom are electrons, protons, and neutrons. Electrons carry a negative charge, protons carry a positive charge, and neutrons carry no charge. Protons and neutrons remain in the nucleus, while electrons are all over the place (not in the nucleus), though they tend to stay in a negatively charged cloud around the nucleus because they are attracted to the positive charge of the protons. Electrons are distributed around the cloud based on differing levels of energy/attraction (electron shells). Also, electrons in shells closer to the nucleus are held more tightly than those in shells farther from the nucleus. Vacancy of electrons in a shell makes it susceptible to a reaction.

3. What six elements are most important in organisms?

The six elements most important in organisms are Carbon (C), Hydrogen (H), Oxygen (O), Nitrogen (N), Phosphorous (P), and Sulfur (S).

Page 33:

1. How are chemical reactions important in cells?

Chemical reactions are important in cells because they are the only way to form new molecules that the cell needs for growth and maintenance, and the making and breaking of bonds involve changes in energy. Chemical reactions occur in the cells of all living organisms.

2. Distinguish among the various types of chemical bonds.

The types of chemical bonds include ionic, covalent, and hydrogen bonds. Ionic bonds are the attraction between oppositely charged ions due to the gain or loss of electrons. Covalent bonds occur when two atoms share one or more pairs of electrons. Hydrogen bonds are a weak attraction between a slightly positive hydrogen atom in a molecule and a close slightly negative atom of another molecule, or possibly even the same molecule if it is large enough.

3. Describe the law of conservation of matter.

The law of conservation of matter states that matter is neither created nor destroyed in chemical reactions. For example, the number of hydrogen atoms stays the same throughout cellular respiration.

4. Why is pH important to living organisms?

pH is important to living organisms because the pH of a cell’s interior helps to regulate its chemical reactions. All cells must rely on these chemical reactions in order to grow and survive. Organisms have ways to control pH and adapt & respond to changes in the pH of the environment.

5. How does the polarity of water assist the movement of molecules?

The polarity of water assists in the movement of molecules by allowing hydrogen bonds to form, which provides an attractive force between water molecules. The polarity of water also allows other polar substances to dissolve easily, as there is a positive-negative end of molecule attraction.

Page 42:

1. Describe how building-block molecules combine to form each of the four types of biological macromolecules.

Carbohydrates contain compounds of carbon atoms and the same two-to-one ratio as water for hydrogen and oxygen atoms. The simplest carbohydrates (or sugars) are called monosaccharides, which contain 3-7 carbon atoms in their carbon skeleton. Important sugars will have a phosphate group attached to the carbon skeleton. Two simple sugar molecules (monosaccharides) can bond to form a double sugar (disaccharide). Several glucose molecules may then bond to form polysaccharides. Most macromolecules are made from building blocks (monomers). Lipids contain hydrogen, carbon, and oxygen, but not at a fixed ratio. Three fatty-acid molecules and a glycerol molecule join to form a simple fat (triglyceride). Unsaturated fatty acids have some double bonds that join some of the carbon atoms. Saturated fatty acids have single bonds that join the carbon atoms, which are saturated with hydrogen. Unsaturated fats are liquid at room temperature, while saturated fats are solid. Phospholipids are made up of a glycerol molecule, two fatty acids, and a phosphate group. Proteins are made by cells by linking amino acids, which are small molecules containing oxygen hydrogen, carbon, and nitrogen atoms; two contain sulfur ones. Any two amino acid molecules can combine when a chemical bond forms between the acid group and the amino group of both. Covalent bonds of this kind are called peptide bonds. More peptide bonds may form, creating a long chain of amino acids - polypeptides. Then, longer polypeptide chains form proteins. Nucleic acids are made of nucleotides, which are connected to form long chains. Each nucleotide then has three parts: a pentose sugar (ribose or deoxyribose), nitrogenous base, and a phosphate group. Nucleic acids containing deoxyribose form deoxyribonucleic acids (DNA), while ribose forms RNA. The four bases in DNA include adenine, thymine, cytosine, and guanine. In RNA, uracil replaces thymine. DNA is double stranded, while RNA is single stranded.

2. What is the relationship between the primary and tertiary structure of a protein?

The relationship between the primary and tertiary structure of a protein is that the primary is a sequence of amino acids in a polypeptide chain, more chain folding and twisting results in secondary structures, and complex folding creates a tertiary structure. In summary, the primary structure determines the three-dimensional shape of the secondary and tertiary structure.

3. Describe the three-part structure of a nucleotide.

The three-part structure of a nucleotide includes a 5-carbon sugar (pentose), nitrogenous base, and a phosphate group.  Nucleotides include either RNA or DNA (pentose). With DNA, the nitrogenous bases are adenine, thymine, cytosine, and guanine. With RNA, uracil replaces thymine. RNA has a single stranded helix, while DNA is double stranded.

4. How do the chemical structures of ribose and deoxyribose differ?

The chemical structures of ribose and deoxyribose differ by the fact that ribose in nucleotides is RNA, while deoxyribose in nucleotides is DNA, the nitrogenous bases are slightly different, and RNA is single stranded while DNA is double stranded. Also, compared to ribose, deoxyribose is missing one oxygen atom, and ribose has a hydroxyl group (OH), whereas deoxyribose only has a hydrogen atom at the same carbon.

Page 47:

1. What determines which nitrogen bases form pairs in DNA?

Base pairing rules determine which nitrogen bases form pairs in DNA. Adenine (A) will only pair with Thymine (T), and Cytosine (C) will only pair with Guanine (G). These bases will only pair with a specific type of other base because of interactions between the surfaces of the nucleotide molecules.

2. If one DNA strand has the sequence AGTTC, what is the sequence of the opposite, or complementary, strand?

The sequence of the opposite/complementary strand will be TCAAG.

3. List four life processes in which DNA plays an important role.

Four life processes in which DNA plays an important role are RNA synthesis, protein synthesis (translations), DNA synthesis (replication), and storing genetic information through the formation of genes. Genes are composed of DNA, which stores genetic information. DNA’s role in producing copies of genes may lead to new genes that arise through mutations and recombination.