Studying molecular and cell biology can be challenging, but it’s necessary if you want to pursue microbiology, biotechnology, or genetics. Understanding molecular and cell biology entails knowing the four groups of macromolecules; the processes of central dogma and cellular respiration; and essential components of eukaryotic cells.
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©Anna Kireieva/Shutterstock.comFour groups of macromolecules
Macromolecules are just that — large molecules. The four groups of macromolecules, shown in the table below, are essential to the structure and function of a cell.
| Group (Building Block) | Large Molecule | Function | To Identify, Look for . . . |
| Carbohydrate (Monosaccharide) | Polysaccharide | Energy storage, receptors, structure of plant cell wall | Made of C,H, and O; –OH’s on all carbons except one |
| Protein (Amino acid) | Polypeptide or protein | Enzymes, structure, receptors, transport, and more | Contain N, have N-C-C backbone |
| Nucleic acid (Nucleotide) | Polynucleotide or nucleic acid | Information storage and transfer | Contain N in rings, nucleotides made of sugar, phosphate and nitrogenous base |
| Lipid * (Glycerol, fatty acids) | Fats, oils, waxes, phospholipids, steroids | Membrane structure, energy storage, insulation | Made of C,H, and O; lots of C-H bonds; may have some C=C bonds (unsaturated); steroids have 4 rings |
*Lipids are not polymers.
Central dogma of molecular biology
In molecular and cell biology, central dogma is the passage of information from DNA to RNA to protein. Here’s a brief breakdown of central dogma’s process:
| Process | What Is Made? | What Is Template? | Important Molecules | Starts At Ends When |
| Replication | DNA | DNA | DNA polymerase, primase, helicase, DNA ligase, topoisomerase | Origin of replication (ORI) Replication forks meet |
| Transcription | RNA | DNA | RNA polymerase | Promoter Termination sequence |
| Translation | Polypeptide (protein) | mRNA | Ribosome, tRNA | Start codon (AUG) Stop codon (UAA, UGA, UAG) |
Important parts of eukaryotic cells
All eukaryotic cells have organelles, a nucleus, and many internal membranes. These components divide the eukaryotic cell into sections, with each specializing in different functions. Each function is vital to the cell’s life.
- The plasma membrane is made of phospholipids and protein and serves as the selective boundary of the cell.
- The nucleus is surrounded by a nuclear envelope with nuclear pores. The nucleus stores and protects the DNA of the cell.
- The endomembrane system consists of the endoplasmic reticulum, the Golgi apparatus, and vesicles. It makes lipids, membrane proteins, and exported proteins and then “addresses” them and ships them where they need to go.
- Mitochondria are surrounded by two membranes and have their own DNA and ribosomes. They transfer energy from food molecules to ATP.
- Chloroplasts are surrounded by two membranes, contain thylakoids, and have their own DNA and protein. They transform energy from the sun and CO2 from atmosphere into food molecules (sugars).
- The cytoskeleton is a network of proteins: microfilaments (actin), microtubules (tubulin), and intermediate filaments (keratin, laminin, and others). Cytoskeletal proteins support the structure of the cell, help with cell division, and control cellular movements.
Cellular respiration in molecular biology
Cellular respiration is your body’s way of breaking down food molecules (carbohydrates, proteins, and fats) and making their stored energy available to the cell. Here’s a brief overview:
| Phase | Location in Eukaryotic Cell? | Molecules That Enter? | Molecules Produced? | Links to Other Phases? |
| Glycolysis | Cytoplasm | Glucose, 2 NAD+, 2 ADP + P | 2 pyruvate, Net 2 ATP, 2 NADH + H+ | Pyruvate to pyruvate oxidation; NADH to ETC |
| Pyruvate oxidation | Matrix of mitochondrion | 2 pyruvate, 2NAD+ | 2 NADH + H+, 2 CO2, 2 acetyl-coA | NADH to ETC, acetyl-coA to Krebs |
| Krebs cycle (TCA cycle, citric acid cycle) | Matrix of mitochondrion | 2 Acetyl-coA, 6 NAD+, 2 FAD | 6 NADH + H+, 2 FADH2, 2 ATP, 4 CO2 | NADH to ETC, FADH2 to ETC |
| Electron transport chain (ETC) | Inner membrane of mitochondrion | NADH, FADH2, ADP + P | 3 ATP per NADH, 2 ATP per FADH2 | NAD+ to glycolysis, pyruvate oxidation and Krebs, FAD to Krebs |
