AP Biology Unit 4

Endocrine system

Secretes hormones into blood from ductless glands that coordinate slower but longer-acting responses

Paracrine

Signals act on cells near the secreting cell

Local regulators

Chemical signals that travel over short distances due to diffusion

Autocrine

Signals act on the secreting cell itself (usually for apoptosis)

Pheromones

Chemical signals that are released from the body and are used to communicate with other individuals

Signal Transduction

The linkage of mechanical, chemical, or electromagnetic stimulus to a specific cellular response

Hormone

A regulatory substance produced in an organism and transported in tissue fluids such as blood or sap to stimulate specific cells or tissues into action.

Neurohormones

A hormone produced by nerve cells and secreted into the circulation.

Epinephrine

A hormone secreted by the adrenal glands, especially in conditions of stress.

Negative Feedback

The diminution or counteraction of an effect by its own influence on the process giving rise to it, as when a high level of a particular hormone in the blood may inhibit further secretion of that hormone, or where the result of a certain action may inhibit further performance of that action.

Growth Hormone

hormone secreted by anterior pituitary gland that usually stimulates growth of bones

second messengers

Small, non-protein water soluble molecules or ions that send messages throughout the cells by diffusion.

Plant growth regulator

Organic compounds other than nutrients (like hormones that affect plant growth.

plant hormone

abscisic acid, auxin, cytokinins, ethylene, gibberellins act as chemical messengers

tropism

A growth response that results in the curvature of whole plant organs toward or away from stimuli owing to differential rates of cell elongation.

phototropism

Growth of a plant shoot toward or away from light.

circadian rhythms

The 24-hour biological cycles found in humans and many other species.

action potential

A neural impulse; a brief electrical charge that travels down an axon.

abiotic stresses

Stresses that come from non-living factors such as wind, temperature, drought or pollution

biotic stresses

Stresses caused by living factors, such as bacteria, fungi, animals, other plants.

heat-shock proteins

Proteins that help maintain integrity of other proteins that would normally be denatured in extreme heat.

anaphase

fourth stage of mitosis, in which the chromatids of each chromosome have separated and the daughter chromosomes are moving to the poles of the cell

binary fission

the type of cell division by which prokaryotes reproduce; each dividing daughter cell receives a copy of the single parental chromosome

cell cycle

an ordered sequence of events in the life of a eukaryotic cell, from its origin in the division of a parent cell until its own division into two; composed of M, G1, S, G2

cell cycle control system

a cyclically operating set of molecules in the cell that triggers and coordinates key events in the cell cycle

cell division

reproduction of a cell

cell plate

a double membrane across the midline of a dividing plant cell, between which the new cell wall form during cytokinesis

centromere

the centralized region joining two chromatids

centrosome

material present in the cytoplasm of all eukaryotic cells, important during cell division; the microtubule organizing center

checkpoint

a critical control point in the cell cycle where stop and go-ahead signals regulate the cycle

chromatin

complex of DNA and proteins that makes up a eukaryotic chromosome; when a cell is not diving it exists as a mass of very long, thin fibers that are not visible with a light microscope

chromosome

a threadlike, gene-carrying structure found in the nucleus; each consists of one very long DNA molecule and associated proteins

cleavage

the process of cytokinesis in animal cells, characterized by pinching of the plasma membrane. Also, the succession of rapid cell divisions without growth during early embryonic development that converts the zygote into ball of cells

cleavage furrow

the first sign of cleavage in an animal cell;a shallow groove in the cell surface near the old metaphase plate

cyclin

a regulatory protein whose concentration fluctuates cyclically

cyclin-dependent kinase (Cdk)

a protein kinase that is only active when attached to a particular cyclin

cytokinesis

the division of the cytoplasm to form two separate daughter cells immediately following mitosis

density-dependent inhibition

the phenomenon observed in normal animal cells that causes them to stop dividing when they come into contact with one another

G0 phase

a nondividing state in which a cell has left the cell cycle

G1 phase

The first gap, or growth phase, of the cell cycle, consisting of the portion of interphase before DNA synthesis begins.

G2 phase

the second growth phase of the cell cycle, consisting of the portion of interphase after DNA synthesis occur

genome

the complete set of genes or genetic material present in a cell or organism.

growth factor

a protein that must be present in the extracellular environment for growth and normal development of certain types of cells; a local regulator that acts on nearby cells to stimulate cell proliferation and differentiation

interphase

the period in the cell cycle when the cell is not dividing; cellular metabolic activity is high, chromosomes and organelles are duplicated, and cell size may increase. 90% of the cell cycle

M phase

mitotic phase; the phase of the cell cycle that includes mitosis and cytokinesis

meiosis

a two-stage type of cell division in sexually reproducing organisms that results in cells with half the chromosome number of the original cell

metaphase

the third stage of mitosis, in which the spindle is complete and the chromosomes, attached to the microtubules at their kinetochores, are all aligned at the plate

mitosis

a process of nuclear division in eukaryotic cells conventionally divided into 5 stages; prophase, prometaphase, metaphase, anaphase, and telophase; conserves chromosome number by equally allocating replicated chromosomes to each of the daughter nuclei

mitotic (M) phase

the phase of the cell cycle that includes mitosis and cytokinesis

mitotic spindle

an assemblage of microtubules and associated proteins that is involved in the movements of chromosomes during mitosis

MPF

maturation-promoting factor (M-phase promoting factor); a protein complex required for a cell to progress from late interphase to mitosis. The active form consists of cyclin and a protein kinase

prophase

the first stage of mitosis, in which the chromatin is condensing and the mitotic spindle begin to form, but the nuclei and nucleolus are still intact

S phase

the synthesis phase of the cell cycle; the portion of interphase during which DNA is replicated

sister chromatids

replicated forms of chromosomes joined together by the centromere and eventually separating during mitosis or meiosis II

somatic cell

any cell in multicellular organisms except a sperm or egg cell

telophase

the fifth and final stage of mitosis, in which daughter cells are forming and cytokinesis has typically begun

amplification

The strengthening of stimulus energy during transduction.

apoptosis

A program of controlled cell suicide, which is brought about by signals that trigger the activation of a cascade of suicide proteins in the cell destined to die.

cytoplasm

The contents of the cell, exclusive of the nucleus and bounded by the plasma membrane.

epinephrine

water soluble ligand molecule; A catecholamine that, when secreted by the adrenal medulla, mediates "fight-or-flight" responses to short-term stresses; also released by some neurons as a neurotransmitter; also known as adrenaline.

G protein

A GTP-binding protein that relays signals from a plasma membrane signal receptor, known as a G protein-coupled receptor, to other signal transduction proteins inside the cell.

gap junction

A type of intercellular junction in animals that allows the passage of materials between cells.

glycogen

An extensively branched glucose storage polysaccharide found in the liver and muscle of animals; the animal equivalent of starch.

ligand

A molecule that binds specifically to another molecule; often first step in cell communication. Water soluble ligands typically do not enter cell. Lipid soluble ligands (such as steroids) do enter the cell.

ligand-gated ion channel

A protein pore in cellular membranes that opens or closes in response to A signaling chemical (its ligand), allowing or blocking the flow of specific ions.

local regulator

A secreted molecule that influences cells near where it is secreted. Used in paracrine and synaptic signaling.

protein kinase

An enzyme that transfers phosphate groups from ATP to a protein, thus phosphorylating the protein.

protein phosphatase

An enzyme that removes phosphate groups from (dephosphorylates) proteins, often functioning to reverse the effect of a protein kinase.

receptor tyrosine kinase

A receptor protein in the plasma membrane, the cytoplasmic (intracellular) part of which can catalyze the transfer of a phosphate group from ATP to a tyrosine on another protein. Receptor tyrosine kinases often respond to the binding of a signaling molecule by dimerizing and then phosphorylating a tyrosine on the cytoplasmic portion of the other receptor in the dimer. The phosphorylated tyrosines on the receptors then activate other signal transduction proteins within the cell.

scaffolding protein

A type of large relay protein to which several other relay proteins are simultaneously attached, increasing the efficiency of signal transduction.

second messenger

A small, nonprotein, water-soluble molecule or ion, such as a calcium ion (Ca2+) or cyclic AMP, that relays a signal to a cell's interior in response to a signaling molecule bound by a signal receptor protein.

signal transduction

The linkage of a mechanical, chemical, or electromagnetic stimulus to a specific cellular response.

signal transduction pathway

A series of steps linking a mechanical or chemical stimulus to a specific cellular response. There are four types that we studied: g-protein linked reception; hormonal reception; receptor tyrosine kinase reception; pathways using second messengers (cAMP; calcium ions).

transcription factor

A regulatory protein that binds to DNA and affects transcription of specific genes. The hormone-receptor complex becomes a transcription factor in the steroid transduction pathway.

three stages of cell communication

1. reception - receptor responds to binding of ligand molecule; 2. transduction - translation and amplification of message; 3. response - activation of cellular response

g-linked protein receptor

receives message for g-linked protein signaling pathway. Consists of seven alpha helices that span the plasma membrane. Changes shape when ligand molecule binds.

signal transduction pathway

The process by which a signal on a cell's surface is converted into a specific cellular response.

local regulators

These regulators influence cells in the vicinity of them.

hormones

Circulating chemical signals that are formed in specialized cells, travel in body fluids, and act on specific target cells.

adenylyl cyclase

Converts ATP to cyclic AMP in response to an extracellular signal.

reception

The target cell's detection of a signal molecule coming from outside the cell.

transduction

The binding of the signal molecule changes the receptor protein in some way.

response

The transduced signal finally triggers a specific cellular response.

G-protein-linked receptor

A plasma membrane receptor that works with the help of a G-protein.

quorum sensing

the regulation of gene expression in response to fluctuations in cell-population density

paracrine signaling

a form of cell- to-cell communication in which a cell produces a signal to induce changes in nearby cells, altering the behavior or differentiation of those cells.

autocrine signaling

form of cell signaling in which a cell secretes a hormone or chemical messenger that binds to a receptor on the same cell leading to changes in the cell

juxtacrine signaling

Type of cell to cell signalling in multicellular organisms that requires close contact (AKA contact-dependent signalling)

synaptic signalling

Type of signalling that occurs over a very short distance called a synapse such as between 2 neurons.

Dimer

This is formed when two receptor polypeptides associate closely with each other

cAMP

Common second messenger which is a derivative of ATP and used for intracellular signal transduction in many different organisms