AP Bio Unit 4 Vocabulary

Covers topics of cell communication, signal transduction, signal transduction pathways, feedback and feedback loops, the cell cycle, and regulation of the cell cycle.

Direct contact

Communication through cell junctions. When signaling substances and other material dissolved in the cytoplasm can freely pass between adjacent cells.

• Animals: Gap junctions

• Plants: Plasmodesmata

Gap junctions

The mode of direct contact in animal cells

Plasmodesmata

The mode of direct contact in plant cells

Hormones

Regulatory substances produced in organisms that are used for long distance signaling in both plants (via vascular tissue or through the air) and animals (via endocrine signaling and the circulatory system).

• Ex: Insulin (released into bloodstream by pancreas, allowing it to circulate through the body and bind to target cells)

Reception

The detection and receiving of a ligand by a receptor in the target cell

Receptor

Macromolecule that binds to a signal molecule (ligand)

Second Messengers

Small, non-protein molecules and ions that help relay the message during transduction and amplify the response.

Transduction

The conversion of an extracellular signal to an intracellular signal that will bring about a cellular response.

• Requires a sequence of changes in a series of molecules known as a signal transduction pathway.

Response

In signal transduction, this is when the final molecule in the signaling pathway converts the signal to a response that will alter a cellular process.

• Ex: (A) Protein that can alter membrane permeability

• Ex: (B) Enzyme that will change a metabolic process

• Ex: (C) Protein that turns genes on or off

Homeostasis

The state of relatively stable internal conditions. In other words: BALANCE.

• Maintained through feedback loops

• Detection and response to stimuli is important

Set Points

Values for various physiological conditions that the body tries to maintain.

• Has a normal range for which it may fluctuate

• Ex: Body temp: SP=98.6, NR=97-99

Stimulus

A variable that will cause a response

Receptor/Sensor

Sensory organs that detect a stimulus.

• This info is sent to the control center (brain)

Effector

Muscle or gland that will respond

Negative Feedback

Reduces the effect of the stimulus

• Most common feedback mechanism

• Ex: Sweat, blood sugar, breathing rate

• Body temp ex: Cold stimulus, temp receptors in skin as receptors, muscles as effectors, shivering as the response

Positive Feedback

Increases the effect of a stimulus

• Ex: Childbirth, blood clotting, fruit ripening

• Childbirth ex: Stimulus is baby pushing on cervix, receptor is nerve cells in cervix sending signals to the brain, effector is the pituitary gland releasing oxytocin, response is oxytocin stimulating contractions

Disease

When the body is unable to maintain homeostasis

• Ex: Cancer (body cannot regulate cell growth)

• Ex: Diabetes (body cannot regulate blood glucose levels)

Cell cycle

The life of a cell from its formation until it divides

Histones

The proteins that DNA associates with and wraps around to form nucleosomes

Nucleosomes

Formed by DNA wrapping around histone proteins. Strings of these form chromatin.

Chromatin

Formed by strings of nucleosomes. When a cell isn’t actively dividing, they are not condensed. When a cell is dividing, they condense to form a chromosome.

Chromosome

Condensed form of chromatin that is densely packed to allow for easier cell division.

Sister Chromatids

After DNA replication, each chromosome has a duplicated copy. The copies join together to form these.

DNA

The molecule that carries genetic information for organisms. Highly important in the development, functioning, and reproduction of organisms.

• Short for: Deoxyribonucleic acid

Centromere

The region on each sister chromatid where they are most closely attached.

Kinetochore

Proteins attached to the centromere that link each sister chromatic to the mitotic spindle.

Genome

All of a cell’s genetic information (DNA)

• Prokaryotes: Singular, circular DNA

• Eukaryotes: One or more linear chromosomes, with each eukaryote having a specific number (ex: humans have 46)

Somatic Cells

Body cells

• Diploid (2n): Two sets of chromosomes with one set from each parent

• Divide by mitosis

• Humans: 2n=46, 23 from mom, 23 from dad

Gametic Cells

Reproductive cells (eggs/sperm)

• Haploid (n): One set of chromosomes

• Divide by meiosis

• Humans: n=23

Tumor

A mass of tissue formed by abnormal cells / abnormal cell growth

Benign (tumor)

Cells are abnormal, but not considered to be cancerous (yet).

• Cells remain at only the tumor site and are unable to spread elsewhere in the body.

Malignant (tumor)

Mass of cancerous cells that may lose their anchorage dependency and can leave the tumor site (metastasize).

Metastasis

When cells separate from the tumor and spread elsewhere in the body

Growth Factors

Hormones released by cells that stimulate cell growth.

• Signal transduction pathway is initiated, CDKs are activated which leads to progression through the cell cycle

• An external cell cycle regulator

Contact (or density) Inhibition

Cell surface receptors recognize contact with other cells.

• Initiates signal transduction pathway that stops the cell cycle in G1 phase

• An external cell cycle regulator

Anchorage Dependency

Cells rely on attachment to other cells or the extracellular matrix to divide.

• An external cell cycle regulator

Checkpoints

Control points that regulate the cell cycle throughout it.

• The cell receives stop/go signals.

• Major ones located at G1, G0, G2, and M(Spindle)

Apoptosis

Programmed cell death

• Occurs if the damage detected at the G2 checkpoint cannot be repaired

(DNA) Mutation

Changes in the DNA

• Cells become cancerous through these

Cyclins

Proteins that are synthesized and degraded at specific stages of the cell cycle as a form of internal cell cycle regulation.

• Concentrations of these vary from cell to cell and throughout each cell cycle phase

Cyclin Dependent Kinases (CDKs)

Enzymes that are active only when specific cyclins are present.

• Act as an internal cell cycle regulator

• Concentration remains constant through each phase of the cell cycle

Ligands

Signal molecules that binds to receptors in a highly specific manner

Protein Kinase

Relays signal inside cell through phosphorylation

Protein Phosphatase

Shuts off pathways through dephosphorylation

Ligand-gated Ion Channels

Channels located in the plasma membrane that are important in the nervous system and act as a “gate” for ions. When a ligand binds to the receptor, the “gate” opens or closes, allowing for the diffusion of specific ions. This initiates a series of events that lead to a cellular response.

GPCR(s)

The largest category of cell surface receptors, which is important in animal sensory systems. They bind to a G protein that can bind to GTP (an energy molecule similar to ATP).

• Short for G coupled protein receptor(s)

cAMP

A second messenger used in many types of cells. It is made from ATP, and is short for cyclic adenosine monophosphate.