Unit 4 Bio Test

Ligand

A cytokines, hormone, or other signaling molecule (ligand) binds with a receptor on the cell membrane. Since the ligand never enters the cell, the chemicals in the transduction pathway are often called "secondary messengers" -the most common secondary messengers is cAMP

G protein-coupled receptors (GPCRs)

A ligand binds to the receptor, the inside portion of receptor changes shape-this activates a G protein (on/off switch) which uses GTP to transfer a phosphate to proteins to activate them... and usually a long biochemical cascade (most often involving cAMP) ending in a specific cellular response.

checkpoint

A point to stop and check to see everything is in line

Transduction

A series of inactive proteins are activated, which in turn activates more proteins, this biochemical cascade passes an extra cellular signal to the inside of the cell (nucleus or cytoplasm) with the intention of triggering a specific cellular response.

Describe the effects of disruptions to the cell cycle on the cell or organism

A) Disruptions (mutations) to the cell cycle may result in cancer and or programmed cell death (apoptosis)

Describe the role of checkpoints in regulating the cell cycle

A) a number of internal controls or checkpoints regulate progression through the cycle B) Interactions between cycling and cycling-dependent kinases control the cell

Receptor Tyrosine Kinases (RTKs)

Cell receptors that involve enzymatic transfer of phosphate groups from ATP to the amino acid tyrosine. In inactive form, receptors are alone- after activation the receptors combine into a dimmer. This movement activates tyrosine and triggers signal transduction.

Cells communicate with one another through direct contact with other cells or from a distance via chemical signaling

Cells communicate by contact Ex. Immune cells interact by cell-to-cell contact, antigen-presenting cells (APCs), helper T-cells, and killer T-cells.

Explain how cells communicate with one another over short and long distances.

Cells communicate over short distances by using local regulators that target cells in the vicinity of the signal-emitting cell. Ex. Neurotransmitters

Explain how a change in the structure of any signaling molecule affects the activity of the signaling pathway

Changes in signal transduction pathways can alter cellular response Chemicals that interfere with any component of the signaling pathway may activate or inhibit the pathway.

Describe positive and or negative feedback mechanisms

Organisms use feedback mechanisms to maintain their internal environments and respond to internal and external environmental changes

Explain how positive feedback affects homeostasis

Positive feedback mechanisms a,policy responses and processes in biological organisms. The variable initiating the response is moved farther away from the initial set point. Amplification occurs when the stimulus is further activated, which, in turn, initiates an additional response that produces system change. Ex. Lactation in mammals

Apoptosis

Programmed cell death. Signal transduction -> gene expression -> apoptosis

ion channel receptors

Receptors that open and close a transport protein, thereby allowing ions to rush through at a high rate

Describe the different types of cellular responses elicited by a signal transduction pathway

Signal Transduction may result in changes in gene expression and cell function, which may alter phenotype or result in programmed cell death (apoptosis) Ex. Apoptosis or SRY gene

SRY gene

Signal transduction -> gene expression -> phenotype Male = XY Female = XX Y = SRY gene that signal sex stem cells to make male sex cells

Describe the role of the environment in eliciting a cellular response

Signal transduction pathways influence how the cell responds to its environment Ex. Epinephrine stimulation of glycogen breakdown in mammals.

Telophase

Back to chromatin. The chromosomes de-condense back into chromatin and nuclear envelopes reform

Anaphase

Chromatids are pulled a pasty by centrioles and spindle fibers

Prophase

Chromatin turn into chromosomes Nuclear envelope digested by enzymes Centrioles migrate towards poles (connect to sister chromatid)

Chromatin

Clusters of DNA, RNA, and proteins in the nucleus of a cell

Cell Cycle Steps

Interphase: 1. G1 phase (Gap 1) 2. S phase : synthesis of DNA 3. G2 phase (Gap 2) 4. M phase a) mitosis (PMAT) b) cytokinesis

# of Chromosomes during cell cycle

Interphase: 46 Prophase: 46 Metaphase: 46 Anaphase: 92 Telophase: 92 Cytokinesis: 46

Metaphase

Lined up middle Sister chromatids connected by spindle fiber

Mutations

Mutations in any domain of the receptor protein or in any component of the signaling pathway may affect the downstream components by altering the subsequent transduction of the signal.

Explain how negative feedback helps to maintain homeostasis

Negative feedback mechanisms maintain homeostasis for a particular condition by regulating physiological processes. If a system is perturbed, negative feedback mechanisms return the system back to its target set point. These processes operate at the molecular and cellular levels Ex. Blood sugar regulation by insulin/glucagon

Chromatids are

duplicate halves of a chromosome

Response

The message reaches its target and a specific cellular response occurs (ex. Gene expression is altered, or a chemical is broken down, etc.)

Chromosomes

condensed chromatin

Describe events that occur in cell cycle

- in eukaryotes, cells divide and transmit genetic information via two highly regulated processes - the cell cycle is a highly regulated series of events for the growth and reproduction of cells - the cell cycle consists of sequential stages of interphase (G1, S, G2), mitosis, and cytokinesis - a cell can enter a stage (G0) where it no longer divides, but it can renter the cell cycle in response to appropriate cues. Non-dividing cells may exit the cell cycle or be held at a particular stage in the cell cycle.

Explain how mitosis results in the transmission of chromosomes from one generation to the next.

-Mitosis is a process that ensures the transfer of a complete genome from a parent cell to two genetically identical daughter cells. - mitosis plays a role in growth, tissue repair, and asexual reproduction - mitosis alternates with interphase in the cell cycle - mitosis occurs in a sequential series of steps (prophase, metaphase, anaphase, telophase)

3 ways cells communicate

1. Cell to cell (no distance) 2. Short distance 3. Long distance

3 types of transduction

1. Ion channel 2. G-protein 3. RTK's

Cellular communication pathway

1. Ligand Bind 2. Transduction 3. Response

Steps of Receptor Tyrosine Kinases (RTKs)

1. Ligand binds to receptor 2. Dimmer forms when ligand binds 3. Dimmer activates a kinase by putting 6 phosphates on Dimer (Tyrosine amino acid) 4. Phosphorylated dimer activates enzyme that cascade and amplify signal.

Steps of G Protein-Coupled Receptors

1. Ligand cause change in G-protein 2. Cyclone activated by alpha g-protein 3. ATP transfers phosphate to activate cAMP 4. Cascade and amplification of proteins

Describe the components of a signal transduction pathway

1. Signal Transduction pathways link signal reception with cellular responses 2. Many signal transduction pathways include protein modification and phosphorylation cascades.

Describe the role of components of a signal transduction pathway in producing a cellular response.

Signaling begins with the recognition of a chemical messenger -a ligand- by a receptor protein in a target cell. -the ligand-binding domain of a receptor recognizes a specific chemical messenger, which can be a peptides a small chemical, or protein, in a specific one-to-one relationship -G protein-coupled receptors are an example of a receptor protein in eukaryotes Signaling cascades relay signals from receptors to cell targets, often amplifying the incoming signals, resulting in the appropriate responses by the cell, which could include cell growth, secretion of molecules, or gene expression. - after the ligand binds, the intracellular domain of a receptor protein changes shape, initiating transduction of the signal. - second messengers (such as cyclic cAMP) are molecules that relay and amplify the intracellular signal - binding of ligand-to-ligand-g@ted channels can cause the channel to open or close

Explain how cells communicate with each other over long distances

Signals released by one cell type can travel long distances to target cells of another cell type. Ex. Hormones in the endocrine system Insulin Testosterone *send hormones throughout the body

Two main types of hormones

Steroid hormones and Peptide hormones

Positive feedback loop

Stimulus: child starts to suck on mammary gland Sensor: Macha o receptor signals the brain that the child wants milk Control: brain receives signal from mechanoreceptors and releases OT/Pro Effect: mammary gland releases milk Send back to stimulus

Negative Feedback Loop

Stimulus: food is digested and adds glucose to blood sugar level Sensor: chemoreceptors that monitor blood glucose levels signal the level is above the set point Control: the brain signals the pancreas to release insulin Effector: insulin signals muscle cells and liver to take in glucose from blood. Stop signal and reset to stimulus.

Cytokinesis

division of the cytoplasm to form two separate daughter cells