Molecular & Cell Biology For Dummies

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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Four 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, phosopholipids, 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.

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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)

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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: actin microfilaments, microtubules, and intermediate filaments. Cytoskeletal proteins support the structure of the cell, help with cell division, and control cellular movements.

  
  

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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 linking step; NADH to ETC
Linking step (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	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, linking step & Krebs, FAD to Krebs

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