Cell Biology Essentials: DNA, Translation, Cells & Metabolism

Sulfur in Prokaryotes

In prokaryotes, sulfur is most often stored as elemental (S0) granules that can be deposited intracellularly or extracellularly. Sulfur granules are especially common in bacteria that use hydrogen sulfide as an electron source.

DNA Structural Components

Do you know the specific structural setup for the DNA molecule? Bases, phosphate, sugar, etc.

A nucleoside consists of a sugar and a nitrogenous base. A nucleotide consists of a phosphate group, a five-carbon sugar, and a nitrogenous base (purines: adenine and guanine; pyrimidines: cytosine and thymine).

Function of Cellulose

Makes cell walls. Cellulose is the main structural component of plant cell walls and provides rigidity and support.

Translating mRNA Codons

Know how to translate mRNA sequences from the codon table.

Four phases:

• Initiation - The start codon (AUG) is near the 5′ end of mRNA. Each codon, except the three stop codons, corresponds to a particular tRNA that carries a specific amino acid.
• Elongation - Involves movement of tRNAs and the ribosome, bringing amino acids to the mRNA and adding them to the growing polypeptide chain.
• Translocation - In translation, translocation refers to the movement of the ribosome along the mRNA during elongation. (Note: "translocation" can also refer to chromosomal abnormalities; see below.)
• Termination - A terminator is a sequence of nucleotides that, when transcribed, causes RNA polymerase to detach from the DNA.

Chromosomal Translocation and Centric Fusion

Translocation can also mean chromosomal abnormalities that occur when chromosomes break and fragments rejoin to other chromosomes. A centric fusion is a translocation in which the centromeres of two acrocentric chromosomes fuse to generate one large metacentric chromosome.

Oxidation and Reduction Reactions

What happens in oxidation and reduction reactions? What happens to the electrons?

OIL RIG: Oxidation Involves Loss, Reduction Involves Gain (of electrons).

Examples of Disaccharides

Examples: Lactose, Sucrose, Maltose.

Cell Theory Principles

• All cells come from preexisting cells.
• Cells are the basic unit of life.
• All living things are made up of cells.

Prokaryote vs Eukaryote Characteristics

Prokaryote

• DNA is circular and typically lacks histone proteins; DNA is free in the cytoplasm (nucleoid).
• No mitochondria.
• 70S ribosomes.
• No internal compartmentalization; no membrane-bound organelles.
• Generally less than 10 micrometers.

Eukaryote

• DNA with proteins as chromosomes/chromatin; DNA is enclosed in a nuclear envelope (nucleus).
• Mitochondria present.
• 80S ribosomes.
• Internal compartmentalization with many organelles.
• Generally more than 10 micrometers.

Diffusion and Osmosis

Diffusion - Substances other than water move between phospholipid molecules or through membrane proteins with channels.

Osmosis - Only water moves through the membrane, often via aquaporins (proteins with specialized channels for water movement).

General Stages of Mitosis

• Prophase: Chromatin coils into chromosomes, centrioles move toward opposite ends of the cell, the nuclear envelope breaks up, spindle fibers form, and chromosomes begin moving toward the cell center.
• Metaphase: Chromosomes align at the metaphase plate; spindle fibers attach to centromeres; centrosomes are at opposite poles.
• Anaphase: Paired centromeres divide; daughter chromosomes move further apart along kinetochore fibers toward opposite poles.
• Telophase: Polar fibers continue to lengthen, nuclei begin to reform at opposite poles, chromatin fibers uncoil, and mitosis is largely complete.