Cellular Structure and Macromolecules

Studying Cellular Structure

• Studying the hierarchical organization of life can help us understand how cells work and create organisms

• Cells are made of atoms, which bond together to form the molecules, which then form larger structures, ultimately creating complex organisms

• Covalent bonds are strong and stable, formed by sharing electrons (example: water H20)

• Ionic bonds happen when an atom loses or gains an electron (example: NaCl salt)

• Noncovalent bonds are weaker, and can be broken easily, but are important for holding together large molecules (example: hydrogen bond in DNA)

The Importance of Macromolecules

• The cell is composed of four major families of small organic molecules: carbohydrates, lipids, proteins and nucleic acids.

• Each macromolecule is a polymer formed from small molecules called monomers or subunits

• Carbohydrates provide energy for the cell and are the building blocks for polysaccharides, like sugars

• Lipids have a hydrophobic hydrocarbon tail (often called a "fatty acid") and a hydrophilic carboxyl group. The most crucial function of lipids is for constructing cell membranes.

• Proteins are formed by multiple amino acids linked with peptide bonds. They provide structural support and perform functions as enzymes.

• Nucleic acids are made up of nucleotides, which include a sugar, a phosphate group, and a nitrogenous base. The most familiar are DNA (provides genetic information for building proteins and other cellular molecules) and RNA (involved in protein synthesis)

• ATP (adenosine triphosphate) is both an energy molecule and a molecular bond used for energy transfer.

• Dehydration (condensation) reactions form bonds between monomers, releasing water.

• Hydrolysis reactions break bonds by adding water.

Understanding Enzymes

• Enzymes are proteins that catalyze reactions (accelerate the rate of a chemical reaction).

• Enzymes are highly selective, can bind to one or more substrates, and have a catalytic site (the region where they bind to a substrate).

• Enzymes lower activation energy of chemical reactions, which is the required energy for the reaction to occur.

• Reaction coupling is used to drive energetically unfavorable reactions by pairing them with spontaneous, favorable reactions.

• Activated carriers can store and transfer energy in a form that a cell can use (ATP is a common example).

Model Organisms & Why They Matter

• Model organisms are non-human species extensively researched to understand biological mechanisms that are also conserved in humans.

• Model organisms are used to understand the fundamental mechanisms of life, and how they are conserved across different species.

• The choice of model organism depends on the specific process being studied, and whether the gene, protein or organelle is conserved across species.

• Examples of common model organisms:

  • Bacteria ( E.coli) – Ideal for studying bacterial gene control and protein function, cell cycle, and bacterial metabolism.

  • Yeast (Saccharomyces cerevisiae) - Ideal for understanding cell cycle & division, aging, protein secretion, and chromosome structure.

  • Plant (Arabidopsis thaliana) – Ideal for understanding the development and physiology of agricultural species.

  • Fruit fly (Drosophila melanogaster) - Ideal for researching embryonic development, body plan formation, nervous system, and heart & muscle formation.

  • Roundworm (Caenorhabditis elegans) - Ideal for cell lineage studies, nervous system formation & function, and body plan development.

  • Zebrafish (Danio rerio) – Ideal for cell lineage, nervous system formation & function, and body plan development.

  • Frog (Xenopus laevis) - Ideal for developmental biology, egg fertilization and embryogenesis, and cell fate tracking.

  • Mouse (Mus musculus) -.Ideal for understanding cancer, human disease models and immune responses.

• Many genes that control developmental processes are similar in humans and other animals, meaning that many findings from model organisms can be applicable to humans, but not all genes are conserved.

Explore the fundamental concepts of cellular structure and the importance of macromolecules in living organisms. This quiz covers essential topics such as covalent, ionic, and noncovalent bonds, as well as the four major families of organic molecules that make up cells. Test your knowledge on how these components contribute to the organization of life.