General Biology: Cells and Biological Macromolecules (Nucleic Acids Focus)

Cells and Biological Macromolecules

Introduction to Biological Macromolecules

Biological macromolecules are large, complex molecules essential for life. They include carbohydrates, proteins, nucleic acids, and lipids. These molecules play critical roles in cell structure, function, and information storage.

• Macromolecule: A large molecule composed of smaller subunits (monomers).

• Polymer: A long molecule consisting of many similar or identical monomers linked together.

• Monomer: The basic building block of a polymer.

• Examples: Proteins (polymers of amino acids), nucleic acids (polymers of nucleotides), carbohydrates (polymers of monosaccharides).

Most Common Elements in Living Organisms

Living organisms are primarily composed of a few key elements that form the backbone of biological molecules.

• Carbon (C)

• Hydrogen (H)

• Oxygen (O)

• Nitrogen (N)

• Phosphorus (P)

• Sulfur (S)

These elements are found in proteins, nucleic acids, carbohydrates, and lipids.

Nucleic Acids: Structure and Function

Definition and Components

Nucleic acids are polymers made up of nucleotide monomers. They are responsible for storing and transmitting genetic information in cells.

• Nucleotide: The monomer of nucleic acids, consisting of a phosphate group, a five-carbon sugar (ribose or deoxyribose), and a nitrogenous base.

• Nucleic Acid: The polymer formed by linking nucleotides via covalent bonds.

• Types: DNA (deoxyribonucleic acid) and RNA (ribonucleic acid).

Primary and Secondary Structure

Nucleic acids have distinct levels of structure that determine their function.

• Primary Structure: The linear sequence of nucleotides in a DNA or RNA strand.

• Secondary Structure: The folding or pairing of nucleic acid strands due to hydrogen bonding between bases (e.g., double helix in DNA, stem-loop structures in RNA).

In DNA, secondary structure is the double helix formed by complementary base pairing. In RNA, secondary structures include hairpins and loops.

Base Pairing and Chargaff's Rules

Nitrogenous bases pair in specific ways, which is crucial for the structure and function of nucleic acids.

• Pyrimidines: Cytosine (C), Thymine (T), Uracil (U)

• Purines: Adenine (A), Guanine (G)

• Base Pairing: In DNA, A pairs with T, and G pairs with C. In RNA, A pairs with U.

• Chargaff's Rules: In DNA, the amount of A equals T, and the amount of G equals C.

Central Dogma of Molecular Biology

The central dogma describes the flow of genetic information in cells.

• DNA: Stores genetic information.

• RNA: Acts as a messenger (mRNA) to carry genetic instructions from DNA to the ribosome.

• Protein: The functional product that carries out cellular activities.

The process can be summarized as:

• DNA → RNA → Protein

Polymerization and Enzymes

Polymers are formed and broken down by specific chemical reactions, often catalyzed by enzymes.

• Dehydration Reaction: Joins monomers by removing a water molecule, forming a covalent bond.

• Hydrolysis: Breaks polymers into monomers by adding water.

• Enzymes: Biological catalysts (usually proteins) that speed up chemical reactions, including polymerization and hydrolysis.

Polymerase Chain Reaction (PCR)

PCR is a laboratory technique used to amplify DNA outside of living cells.

• Purpose: To increase the amount of DNA for analysis (e.g., forensic science, ancient DNA studies).

• Key Enzyme: DNA polymerase.

Comparison of Biological Macromolecules

Macromolecule	Monomer	Polymer	Main Function
Carbohydrates	Monosaccharide	Polysaccharide	Energy storage, structure
Proteins	Amino acid	Polypeptide	Catalysis, structure, transport
Nucleic Acids	Nucleotide	DNA/RNA	Information storage, transmission
Lipids	Fatty acid (not a true polymer)	Triglyceride, phospholipid	Energy storage, membranes

Key Biological Concepts

ATP and Energy Transfer

Adenosine Triphosphate (ATP) is the primary energy carrier in cells. When ATP is used for energy, it is typically converted to ADP (Adenosine Diphosphate):

• Reaction: $\text{ATP} \rightarrow \text{ADP} + \text{P}_i$

• Function: Provides energy for cellular processes.

Enzymes

Enzymes are proteins that act as biological catalysts, speeding up chemical reactions without being consumed.

• Function: Lower activation energy, increase reaction rate.

• Example: DNA polymerase (replicates DNA), amylase (breaks down starch).

Photosynthesis

Photosynthesis is the process by which plants, algae, and some bacteria convert light energy into chemical energy.

• Location: Occurs in chloroplasts (in plant cells).

• Equation: $6\text{CO}_2 + 6\text{H}_2\text{O} + \text{light energy} \rightarrow \text{C}_6\text{H}_{12}\text{O}_6 + 6\text{O}_2$

Summary Table: Key Features of Nucleic Acids

Feature	DNA	RNA
Sugar	Deoxyribose	Ribose
Bases	A, T, G, C	A, U, G, C
Strands	Double	Single (usually)
Function	Genetic information storage	Messenger, protein synthesis

Additional info:

• Survey results and quiz questions in the slides reinforce understanding of basic biology concepts, such as the role of enzymes, ATP, and the structure of macromolecules.

• Some slides reference the importance of knowing why students are taking the course, which is useful for motivation but not directly academic content.