The addition and removal of phosphate groups can serve critical functions in the regulation of protein activity. The binding or uncoupling of phosphate groups frequently serves to activate or deactivate proteins.

A phosphatase removes a phosphate group from its ligand.

A kinase is an enzyme that phosphorylates—or adds a phosphate group to—its ligand.

Several different types of proteins can change the structure of a ligand, such as isomerases, and ubiquitin ligases add ubiquitin to their ligands.

Sister chromatids are two identical copies of the same chromosome. They are attached to each other at a region called the centromere. Homologous chromosomes are not identical. Rather, they are chromosomes that look alike, and have the same genes at the same loci, but not necessarily the same versions of those genes. For example, we all have two copies of chromosome number 1. Assume eye color is coded on this chromosome. One copy may have the brown allele, while the other copy might have the green allele. Both chromosomes have loci that code for eye color, but they are not identical since one came from each parent.

Sister chromatids are two identical copies of the same chromosome. They are attached to each other at a region called the centromere. Homologous chromosomes are not identical. Rather, they are chromosomes that look alike, and have the same genes at the same loci, but not necessarily the same versions of those genes. For example, we all have two copies of chromosome number 1. Assume eye color is coded on this chromosome. One copy may have the brown allele, while the other copy might have the green allele. Both chromosomes have loci that code for eye color, but they are not identical since one came from each parent.

One way to divide prokaryotes is into aerobes and anaerobes. Aerobes are organisms that can survive and grow in the presence of oxygen while anaerobes did not require oxygen for survival and growth. All aerobes can produce ATP with or without oxygen (though they may need oxygen for survival. However some anaerobes are harmed by the presence of oxygen (obligate anaerobes). These anaerobes can produce ATP through glycolysis or anaerobic respiration, where another molecule besides oxygen is used as the final electron acceptor for the electron transport chain.

The law of independent assortment states that inheritance of one gene does not influence inheritance of another gene. Thus, inheritance of seed color does not affect the inheritance of seed shape.

The DNA will appear uncondensed and restricted to the nucleus. This is because a majority of the cells found in the sample will be in interphase, the longest stage of the cell cycle. Since it is the longest phase in the cell cycle, a majority of cells will be undergoing this phase at any given sample time. It is a point when the cell is undergoing normal cell processes and preparing for replication. During this phase, the DNA is uncondensed, allowing for transcription and giving DNA replication enzymes easy access to the nucleotide sequence.

DNA is condensed into 46 discrete chromosomes and restricted to the nucleus during early prophase, which makes up only a short period of the cell cycle. DNA is never condensed into 23 discrete chromosomes in somatic cells (such as epithelium), since 23 chromosomes would indicate a haploid cell. In humans, haploid cells only exist in the gametes, or sex cells. While prokaryotes have a single circular chromosome floating in the cytoplasm, such structure for a eukaryotic genome is not possible.

The pyruvate decarboxylation reaction is pyruvate+ CoA-SH+ NAD+ -> NADH+ CO2+ acetyl CoA.

Glycolysis is the first step of cellular respiration where glucose is broken down down into pyruvate. It occurs in the cytosol. In the presence of oxygen, pyruvate is exported to the mitochondria where it is further oxidized. In the absence of oxygen, pyruvate is converted into ethyl alcohol or lactic acid (fermentation) in the cytoplasm.

Prokaryotic cells, mitochondria, and chloroplasts have 70S ribosomes, whereas eukaryotic cells have 80S ribosomes. This provides support for the Endosymbiotic Theory, which states that the mitochondria and chloroplast in eukaryotic cells were once aerobic bacteria (prokaryote) that were ingested by a large anaerobic bacteria (prokaryote).

Prokaryotic cells, mitochondria, and chloroplasts have 70S ribosomes, whereas eukaryotic cells have 80S ribosomes. This provides support for the Endosymbiotic Theory, which states that the mitochondria and chloroplast in eukaryotic cells were once aerobic bacteria (prokaryote) that were ingested by a large anaerobic bacteria (prokaryote).