AP Biology 4.1 Cell Communication Study Notes - New Syllabus Effective 2025
AP Biology 4.1 Cell Communication Study Notes- New syllabus
AP Biology 4.1 Cell Communication Study Notes – AP Biology – per latest AP Biology Syllabus.
LEARNING OBJECTIVE
Describe the ways that cells can communicate with one another.
Key Concepts:
- Cell Communication
4.1.A.1 – Cell communication
Cells typically communicate using chemical signals. These chemical signals, which are proteins or other molecules produced by a sending cell, are often secreted from the cell and released into the extracellular space. There, they can float – like messages in a bottle – over to neighboring cells.
Not all cells can “hear” a particular chemical message. In order to detect a signal (that is, to be a target cell), a neighbor cell must have the right receptor for that signal. When a signaling molecule binds to its receptor, it alters the shape or activity of the receptor, triggering a change inside of the cell. Signaling molecules are often called ligands, a general term for molecules that bind specifically to other molecules (such as receptors).
The message carried by a ligand is often relayed through a chain of chemical messengers inside the cell. Ultimately, it leads to a change in the cell, such as alteration in the activity of a gene or even the induction of a whole process, such as cell division. Thus, the original intercellular (between-cells) signal is converted into an intracellular (within-cell) signal that triggers a response.
4.1.B.1 – Paracrine Signaling
Often, cells that are near one another communicate through the release of chemical messengers (ligands that can diffuse through the space between the cells). This type of signaling, in which cells communicate over relatively short distances, is known as paracrine signaling.
Paracrine signaling allows cells to locally coordinate activities with their neighbors. Although they’re used in many different tissues and contexts, paracrine signals are especially important during development, when they allow one group of cells to tell a neighboring group of cells what cellular identity to take on.
4.1.B.2 – Endocrine Signaling
Hormones are signaling molecules that travel in the bloodstream throughout the body to reach the specific receptor on the membrane of the effector cell or bind to the receptor intracellularly. Long-range signaling is also is called endocrine signaling. Hormones of the endocrine system are the best example of long-range signaling. For example, epinephrine is secreted by the adrenal medulla into the blood. In the bloodstream, it can interact with many receptors (alpha and beta-adrenergic receptors). These receptors are distributed in several tissues, including the heart, blood vessels, lungs, liver, and kidneys. Adrenoceptors belong to the GPCR superfamily and divide into alpha and beta. Further subdivided as alpha-1, alpha-2, beta-1, beta-2 and beta-3. They regulate several physiological processes, like blood pressure, heart rate, and vasoconstriction. Another example is the hormone erythropoietin, secreted by specialized cells in the kidney. It stimulates erythroid progenitor cells in the bone marrow to produce more erythrocytes (erythropoiesis).
B. GEnome Structure
➢ Genetic code is the sequence of the base pairs
➢ Gene codes for a specific protein
➢ Prokaryotes: single DNA molecule
➢ Eukaryotes: multiple DNA molecules
➢ An species entire DNA sequence is its genome
➢ Chromosome is each separate chunk of DNA
➢ Prokaryotes have one circular chromosome, and eukaryotes have linear chromosomes
➢ chromosomes wrapped around proteins called histones, and histones are bunched in groups called a nucleosome
➢ How Tightly DNA is packaged depend on the section of DNA and what is going on in the cell at the time
- Euchromatin is extremely loose genetic material
- Heterochromatic is extremely tight genetic material with inactive genes
