General Biology Study Guide: Chapters 4-7 (Nucleic Acids, Carbohydrates, Lipids, Cell Structure)

Chapter 4: Nucleic Acids

Structure and Function of Nucleic Acids

Nucleic acids are essential biomolecules responsible for the storage and transmission of genetic information. The two main types are DNA (deoxyribonucleic acid) and RNA (ribonucleic acid).

• Monomers of Nucleic Acids: Nucleic acids are polymers made up of monomers called nucleotides. Each nucleotide consists of three parts: a nitrogenous base, a pentose sugar, and a phosphate group.

• DNA Double Helix: The structure of DNA is a double helix, with two strands running in opposite directions and held together by hydrogen bonds between complementary bases.

• Ribonucleotides vs. Deoxyribonucleotides: Ribonucleotides (in RNA) contain ribose sugar, while deoxyribonucleotides (in DNA) contain deoxyribose sugar.

• Pyrimidines and Purines: Nitrogenous bases are classified as pyrimidines (cytosine, thymine, uracil) and purines (adenine, guanine).

• Polymerization Reactions: Nucleic acids are formed by condensation reactions that link nucleotides via phosphodiester bonds.

• Polarity of Nucleic Acids: Nucleic acids have directionality, with a 5' end (phosphate group) and a 3' end (hydroxyl group).

• DNA Replication: DNA replication is the process by which DNA makes a copy of itself, allowing genetic information to be passed to new cells.

• RNA as the First Self-Replicating Molecule: RNA is hypothesized to have been the first genetic material due to its ability to both store information and catalyze reactions.

Example: The sequence of nucleotides in DNA encodes the instructions for building proteins.

Chapter 5: Carbohydrates

Structure and Function of Carbohydrates

Carbohydrates are organic molecules composed of carbon, hydrogen, and oxygen. They serve as energy sources and structural components in cells.

• Monosaccharides: The simplest carbohydrates, also known as simple sugars (e.g., glucose, fructose).

• Polysaccharides: Complex carbohydrates formed by linking monosaccharides via glycosidic bonds. Examples include starch, glycogen, and cellulose.

• Structure of Polysaccharides: Polysaccharides can be linear or branched, affecting their function and digestibility.

• Role in Energy Storage: Carbohydrates such as starch (in plants) and glycogen (in animals) are used for energy storage.

• Table: Comparison of Polysaccharides

Polysaccharide	Monomer	Function	Organism
Starch	Glucose	Energy storage	Plants
Glycogen	Glucose	Energy storage	Animals
Cellulose	Glucose	Structural support	Plants

Example: Glycogen is stored in the liver and muscles of animals for quick energy release.

Chapter 6: Lipids

Types and Functions of Lipids

Lipids are hydrophobic molecules that play key roles in energy storage, membrane structure, and signaling.

• Phospholipids: Major components of cell membranes, consisting of a hydrophilic head and hydrophobic tails.

• Types of Lipids: Includes fats (triglycerides), phospholipids, steroids, and membrane lipids.

• Steroids: Lipids with a characteristic four-ring structure; examples include cholesterol and hormones.

• Membrane Lipids: Phospholipids and cholesterol contribute to membrane fluidity and integrity.

Example: Phospholipids form bilayers that make up the cell membrane, creating a barrier between the cell and its environment.

Chapter 7: Cell Structure and Function

Eukaryotic Cell Structures and Transport

Cells are the basic units of life, with eukaryotic cells containing membrane-bound organelles that perform specialized functions.

• Glut-1: A glucose transporter protein important for cellular uptake of glucose.

• Eukaryotic Cell Structures: Organelles such as the nucleus, mitochondria, and chloroplasts have distinct functions. Table 7.1 summarizes these structures.

• Nuclear Transport: The movement of molecules into and out of the nucleus through nuclear pores. Section 7.4 covers the mechanisms involved.

• Mitochondria and Chloroplasts: These organelles are unique due to their double membranes and roles in energy conversion.

• Endomembrane System: A network of membranes within the cell, including the endoplasmic reticulum, Golgi apparatus, and vesicles, involved in synthesis and transport of biomolecules.

• Prokaryotic vs. Eukaryotic Cells: Prokaryotic cells lack membrane-bound organelles, while eukaryotic cells possess them.

• Actin Filaments and Myosin: Cytoskeletal elements involved in cell movement and shape. Section 7.6 discusses different cytoskeletal elements.

• Figure 7.27: Illustrates cytoskeletal structures and their functions in the cell.

Example: The endomembrane system coordinates the production and transport of proteins and lipids within the cell.

Additional info:

• Some details, such as the specific content of Table 5.1 and Figure 7.27, were inferred based on standard biology textbooks.

• Key terms and processes were expanded for clarity and completeness.