DNA Replication, Transcription, and the Genetic Code
DNA Replication
DNA replication is a semiconservative process that occurs on the double helix. It produces new DNA molecules, with one original strand and one new strand. The new strand comprises the polymerization of free nucleotides, complementing the template strand’s nucleobases. DNA can be bicatenary (double-stranded) and, more rarely, single-stranded.
Initiation
The initiation signal is a sequence of nucleotides in DNA called the origin of replication. Replication is circular and occurs in three
Read MoreAnomalous Expansion of Water and Food Chemistry
Water’s Anomalous Expansion
It is said that water has anomalous dilation. This occurs at 4 degrees Celsius, and between 0 and 4°C. Experience tells us that when we heat a body, it expands, and when cooled, it contracts. However, water does not always behave this way. When water freezes, it expands. That is, a mass of ice has a greater volume than the same mass of liquid water. This phenomenon is called the anomalous expansion of water.
The density of water varies with temperature, so that the maximum
Read MoreMolecular Diagrams: Glucose, Ribose, Fatty Acids & Metabolism
Molecular Diagrams & Biochemicals
Drawing Molecular Diagrams
Amino Acids
- Composed of an amine (NH2) group, a carboxyl (COOH) group, and an R group.
- 20 amino acids exist that compose all proteins.
- Each amino acid differs because the R groups are different.
Glucose
- Is a reducing sugar that contains C6H12O6.
- Most commonly found in a ringed structure and is the main product formed by photosynthesis.
- Energy molecule used in aerobic respiration.
- Monomer of starch, glycogen, and cellulose.
Ribose
- Pentose (5 carbon)
Refuting Spontaneous Generation: Redi, Spallanzani, Pasteur
The Fallacy of Spontaneous Generation
Spontaneous generation was a long-held belief, even described by Aristotle. Observation suggested that worms, flies, and other organisms emerged from mud, rotting meat, and moist places. The idea that life continuously arose from organic matter became commonplace in science. Today, the scientific community considers this theory refuted.
Francesco Redi’s Experiment
Francesco Redi, an Italian physician, conducted an experiment in 1668. He placed pieces of snake,
Read MoreUnderstanding Cells: Structure, Function, and Chemical Composition
The cell is the fundamental unit of life, capable of autonomous function. All living organisms are composed of cells, and it is generally accepted that no entity is considered alive without at least one cell. Some microscopic organisms, such as bacteria and protozoa, are single-celled, while animals and plants are composed of millions of cells organized into tissues and organs. Although viruses and cell-free extracts perform many functions of living cells, their lack of independence, growth, and
Read MoreUnderstanding Plant Tissues, Reproduction, and More
Plant Tissues
Plant tissues are groups of similar cells performing specific functions in plants. They are broadly classified into dermal, ground, vascular, and meristematic tissues.
1. Dermal Tissue
Dermal tissue forms the outer protective covering of the plant. It consists of:
- Epidermis: Covers the external parts of herbaceous plants. Epidermal cells secrete a waxy cuticle, protecting against water loss. It is the outermost layer of the primary plant body, covering roots, stems, leaves, floral parts,