Molecular Biology Basics: From Molecules to Cellular Processes

Posted on Apr 29, 2024 in Biology

Molecular Bonds and Structures

Water Molecule Bonds

Two water molecules are held together by hydrogen bonds, while the hydrogen and oxygen atoms within a single water molecule are connected by polar covalent bonds.

Biological Molecule Structures

Peptides

Peptide molecules are short chains of amino acids linked by peptide bonds. These bonds form between the carboxyl group of one amino acid and the amino group of another.

Carbohydrates

Carbohydrates are organic compounds composed of carbon, hydrogen, and oxygen, typically in the ratio of Cm(H2O)n. Examples include sugars and starches.

Lipids

Lipids are non-polar organic molecules, often containing long hydrocarbon chains. They include fats, oils, and waxes.

Nucleic Acids

Nucleic acids, such as DNA and RNA, are chains of nucleotides. Each nucleotide consists of a phosphate group, a sugar, and a nitrogenous base.

Chargaff’s Rules

Chargaff’s rules state that in DNA:

  • The amount of cytosine (C) is equal to the amount of guanine (G).
  • The amount of adenine (A) is equal to the amount of thymine (T).

Photosynthesis and Cellular Respiration

Oxygen Source in Photosynthesis

The oxygen released during photosynthesis comes from water. The process can be summarized by the equation: 6H2O + 6CO2 → 6O2 + C6H12O6

Galactose vs. Lactose

  • Galactose is a monosaccharide and a component of lactose.
  • Lactose is a disaccharide composed of glucose and galactose.

Light and Plants

Green light is the least useful for photosynthesis, as plants reflect or transmit green wavelengths, making them appear green to our eyes.

Cellular Respiration

Stages

  • Glycolysis: Occurs in the cytoplasm and breaks down glucose into pyruvate, producing 2 ATP.
  • Anaerobic Respiration: Occurs without oxygen and produces a small amount of ATP.
  • Aerobic Respiration: Requires oxygen and occurs in the mitochondria, producing a large amount of ATP.

Properties of Water

  • Cohesion: Water molecules stick together due to hydrogen bonding.
  • Adhesion: Water sticks to other polar surfaces.
  • Polarity: Water molecules have a positive and negative end due to the unequal sharing of electrons.
  • Solvent: Water dissolves many substances due to its polarity.
  • High Specific Heat: Water resists changes in temperature.

DNA Structure and Function

Okazaki Fragments

Okazaki fragments are short DNA fragments formed on the lagging strand during DNA replication.

DNA to RNA Base Pairing

In DNA, adenine (A) pairs with thymine (T), and cytosine (C) pairs with guanine (G). In RNA, uracil (U) replaces thymine and pairs with adenine.

Codons

Codons are three-base sequences in DNA and RNA that code for specific amino acids.

Mitochondria and Cellular Respiration

Cellular respiration, the process of converting food into energy (ATP), occurs in the mitochondria.

Chlorophyll Location

Chlorophyll, the green pigment involved in photosynthesis, is located in the chloroplasts of plant cells.

Products of Photosynthesis

Light-dependent reactions produce oxygen, ATP, and NADPH.

Calvin cycle produces glyceraldehyde-3-phosphate (G3P), which can be used to make glucose.

DNA vs. RNA

Both DNA and RNA contain a phosphate, a sugar, and a base. DNA has deoxyribose sugar and thymine, while RNA has ribose sugar and uracil.

Sulfur in Prokaryotes

Prokaryotes often store sulfur as elemental sulfur granules.

DNA Structure

DNA is a double helix composed of nucleotides. Each nucleotide consists of a phosphate group, a deoxyribose sugar, and a nitrogenous base (A, T, C, or G).