Cell Bio Test Review

The enzyme that adds phosphates is called a kinase. This enzyme catalyzes the transfer of a phosphate group from ATP to a substrate molecule. This phosphorylation reaction can result in a conformational change in the substrate, altering its shape and function. This change in conformation is often crucial for the regulation of various cellular processes, such as signal transduction pathways and enzyme activity.

Dephosphorylation refers to the process of removing a phosphate group from a molecule. This process can occur through enzymatic reactions or other chemical processes. By removing the phosphate group, dephosphorylation can regulate the activity of proteins and other molecules, altering their function and signaling pathways.

An enzyme that removes phosphates is called a phosphatase. Phosphatases are a group of enzymes that catalyze the hydrolysis of phosphate ester bonds, resulting in the removal of a phosphate group from a molecule. These enzymes play a crucial role in various cellular processes, including signal transduction, metabolism, and DNA repair. By removing phosphates, phosphatases regulate the activity of proteins and other molecules, influencing their function and cellular processes.

When a phosphate group is added to a protein, it can either activate or inhibit the protein's function. The addition of a phosphate group can activate a protein by changing its shape or structure, allowing it to carry out its intended function. On the other hand, the addition of a phosphate group can also inhibit a protein by altering its activity or preventing it from performing its normal function. Therefore, the addition of a phosphate group can have dual effects on protein function, either activating or inhibiting it.

Proteins can exist in three possible states when it comes to their interaction with nucleotides such as ATP (adenosine triphosphate) or GTP (guanosine triphosphate). The first state is when the protein is bound to ATP or GTP, indicating that it is actively engaged in a cellular process. The second state is when the protein is bound to ADP (adenosine diphosphate) or GDP (guanosine diphosphate), which suggests that it has completed its function and is in the process of releasing the nucleotide. The third state is when the protein is unbound or dissociated, meaning it is not interacting with any nucleotide and is available for other cellular processes.

Flippases – move lipids from one leaflet to another (always the same direction)
Scramblases - flip lipids from either leaflet to the other leaflet- direction is random

Often flippases generate asymmetry and scramblases oppose it –balance achieved

Phosphorylation refers to the process of adding a phosphate group to a protein. This modification is crucial for regulating protein activity, as it can change the protein's structure, function, and interactions with other molecules. Phosphorylation is a common post-translational modification that plays a key role in various cellular processes such as signal transduction, enzyme activation, and gene expression. It is mediated by enzymes called kinases, which transfer a phosphate group from ATP to specific amino acid residues on the protein. Overall, phosphorylation is essential for the proper functioning and control of proteins within cells.

Phosphates come from ATP, which stands for adenosine triphosphate. ATP is a molecule that stores and releases energy in cells. It consists of a nucleotide base (adenosine) and three phosphate groups. When one of the phosphate groups is hydrolyzed, it releases energy and becomes adenosine diphosphate (ADP). This process of breaking down ATP into ADP and phosphate releases energy that can be used for various cellular processes. Therefore, ATP is the source of phosphates in cells.

B and E describe prokaryotes, d is incorrect because while some exist in multicellular organisms, many are single-cellular.