General Biology Study Guide: Chapter 4 out of 4,5,6 & 7
→ ← (Please keep in mind THAT THIS IS AN OVERVIEW)
Content we’re covering → CHAPTER 4: Nucleotides, CHAPTER 5: Carbohydrates, CHAPTER 6: Lipids, and CHAPTER 7: The Components of Eukaryotic and Prokaryotic Cells.
CHAPTER 4 Nucleotides:
Nucleic Acids store the information that encode for life.
Nucleic acids= monomers; assembled from monomers called nucleotides. There are three components of a nucleotide:
1. A phosphate group
2. Five carbon sugar
3. A nitrogenous base
Ribonucleotides: monomers of ribonucleic acid (RNA) The sugar in this is called, “ribose.”
Deoxyribonucleotides: monomers of deoxyribonucleic acids (DNA) “Deoxy” in this means, “lacking oxygen.”
Both RNA and DNA are long and linear polymers.
Both sugars have an OH bonded to a 3’ carbon, but ribose has an OH group bonded to a 2’ carbon and deoxyribose has an H at the same locationa difference of an oxygen atom.
Both sugars also differ with their nitrogenous bases.
RNA C (cytosine) bonds with G (guanine) while A (adenine) bonds with U (uracil.) → DNA C (cytosine) bonds with G (guanine), but A (adenine) bonds with T (Thymine.) → These eight bases (cytosine, guanine, adenine, and thymine) are used to create nucleic acids.
Don't forget about the age old question of Which type of cell division occurs in the embryonic development and growth of vertebrates?
Nucleotide Polymerization to Form Nucleotides:
Nucleotides polymerize by a condensation reaction between a hydroxyl on the sugar part of the nucleotide and the phosphate group of another nucleotide. This reaction causes a phosphodiester linkage (a phosphodiester bond) between the nucleotides. This releases a water molecule.
Phosphodiester linkage a type of covalent bond. Its formation is explained above. (Consider it → a molecular glue.)
DNA AND RNA STRANDS ARE DIRECTIONAL:
The sugarphosphate backbone of a nucleic acid is directional.
In a DNA or RNA strand, one end has an unlinked 5’ phosphate while the other has an unlinked 3’ hydroxyl group. What this means: This means that that the groups are NOT bounded to another nucleotide. Don't forget about the age old question of Does arrhenius constant change with temperature?
Order of different nucleotides for the primary structure of a nucleic acid.
The structure primary structure of a strands of DNA or RNA is always written like this: 5’ 3’ → direction.
In cells, RNA and DNA are always synthesized in this direction (5’ 3’). Nucleotides will be → added at the 3’ of the molecule. If you want to learn more check out What are some examples of cultural syncretism?
THE ANTIPARALLEL DOUBLE HELIX:
This was developed by Watson and Crick. The created a series of models to experiment with different helical configurations. As they experimented, they discovered three things: We also discuss several other topics like How do ecosystem services contribute to humans' well-being?
We also discuss several other topics like What is meant by measure of central tendency?
1. Only purinepyrimidine pairs will fit inside of the DNA’s double helix. (Purine A and G will pair with Pyrimidine C and T.)
2. Purinepyrimidine allows hydrogen bonds that form between the nitrogenous bases A, T, G, and C. A and T will form two hydrogen bonds. C and G will form three hydrogen
bonds (C and G are stronger than A and T because of the three hydrogen bonds.) 3. In doublestranded DNA, the backbones must be antiparallel. This means that if one
DNA strand runs from 5’ 3’, then the other side must run from 3’ 5’. This allows for → → hydrogen bonds to form between A, T, C, and G. IMPORTANT NOTE: HYDROGEN BONDS CANNOT FORM BETWEEN THE DNA NITROGENOUS BASES OTHERWISE.
Hydrogen Base Pairings It is how nitrogenous bases are able to pair up. It is based on hydrogen → bonding and can also be called WatsonCrick Pairings. This explains the purinepyrimidine ratios that Chargaff discovered. (Chargaff’s Rule located below.) We also discuss several other topics like Is sahelanthropus a hominin?
Also: There is a major groove in DNA that is 50% wider than the minor groove. The groove geometry of DNA is important when it comes to interacting with proteins that bind DNA.
DNA= A Tertiary Structure.
DNA Double Helix= A Stable Structure.
PEOPLE TO KNOW:
1. Watson and Crick: Discovered the double helix structure of DNA.
2. Friedrich Miescher: The first to extract DNA. He found that the substance for DNA was
different from proteins It didn’t have any sulfur and had a high phosphorus content. → 3. Phoebus Levene Created some correct and incorrect discovered. The → correct ones are
that: 1.) nucleic acids are made of nucleotides and 2.) that a nucleotide has a nitrogen base, a pentose (5 ringed sugar), and a phosphate group. The wrong are that: 1.) Nucleodie sequences are all the same and that 2.) DNA does not carry hereditary
information because it lacks complexity.
4. Chargaff: Made the rule that nucleotide composition varies for different species. All species= A to T and G to C. Purines will equal (A+G) while the pyrimidines will equal (C+T).
5. Franklin and Gosling: Rosalind Franklin and Maurice Wilkins calculated the distance between atom groups in a DNA molecule by using Xrays on the DNA and examining the radiation. This technique is called Xray crystallography. By using this method, they concluded that DNA molecules had a repeating structure (helical, spiral,
6. Sidney Altman and Thomas Cech: Showed that organisms have catalytic RNAs.
Functions of DNA:
DNA’s primary structure has information showing it how to copy itself and how to be
made. The steps for synthesis of a complimentary strand are below:
1. The two strands of DNA can separate. It uses heat or enzymecatalyzed reactions
to break its hydrogen bonds and separate.
2. Template Strands the original strand of DNA. Free deoxyribonucleotides will form hydrogen bonds with complimentary strands (the new strand). When this happens, sugar phosphate groups for phosphodiester linkages to create new
3. Complementary base pairings allow each strand of the DNA double helix to be copied completely. This will then produce two identical daughter molecules.
Structures and Functions of RNA:
3 structures: primary, secondary, tertiary structures of RNA.
1. Primary: Has four types of nitrogenous bases that extend from the sugarphosphate backbone. It has ribose instead of deoxyribose (like DNA). It has Uracil instead of Thymine. It has an additional hydroxyl. This causes it to attach phosphate linkages between nucleotides and break its backbone. The extra hydroxyl causes RNA to be less
stable than DNA.
2. Secondary: A binds to U and has two hydrogens. C still binds to G and has 3 hydrogens. However, RNA can bind with complementary bases (forms on the same strand). This formation is antiparallel and resembles a DNA’s double helix. This is called a hairpin. Forms spontaneously. Stabilized by hydrogen bonds and van der Waals reactions.
3. Tertiary: This is when secondary structures fold into more complex shapes. In summary, RNA molecules are more diverse than DNA when it comes to size, shape, and reactivity.
Because of their variety of shapes, sizes, and reactivity, they have many different functions:
1. RNAs are called ribozymes because, like proteins enzymes (think ribosomes), they can catalyze reactions. (Such as catalyzing certain reactions in a cell.) The threedimensional
nature of ribozymes is important to its catalytic activity.
2. Help process information stored in DNA.
3. Help synthesize proteins.
New Questions Answered:
This information helped to solidify three of the five characteristics of life: 1. Information: Proteins and ribozymes process information stored in nucleic acids in order
to create more proteins.
2. Replication: Enzymes, and possibly ribozymes, replicate the nucleic acids which stored
the hereditary information.
3. Evolution: Changes in nucleic acids= the creation of different proteins and ribozymes. Some advantages from these changes caused the evolution of new functions.