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Flashcards in Unit 4 Test Deck (74):

What is cell signaling?

A cell detects a signal (reception), converts the extracellular signal into an intracellular signal (signal transduction), and then some action occurs (response).


What is signal transduction?

The transformation of an extracellular signal to an intracellular signal.


What happens in an Exocrine gland?

Non-hormonal products are secreted from ducts onto a surface.


What happens in an Endocrine gland?

Hormones are secreted into tissue, fluid, or blood.


What happens in the nervous system?

Electrical impulses are sent down neurons to form a neurotransmitter that will be sent across a gap to the next neuron


What is the synapse?

The gap separating individual neurons.


What is a paracrine signal?

When a cell releases a signal to a neighboring cell. Short distance and specific, local mediator.


What is an autocrine signal?

When a cell receives a signal it created. Short distance and specific, local mediator.


What is a juxtacrine signal?

Cell-to-cell contact signaling. Short distance and specific, local mediator


What is an endocrine signal categorized as?

Long distance, can be specific or general, is a hormone.


What is a nervous signal categorized as?

Short distance (but travels long distances in the cell), specific


What is the difference between hormones and local mediators?

Hormones travel through the blood, and local mediators do not.


What main factor does the speed of a signal depend on?

The source of the signal.


Are nerve signals fast or slow?



Are endocrine signals fast or slow?

Fast if proteins need to be activated or deactivated, or slow if proteins need to be transcribed.


What determines how different cells respond to similar signals?

Which proteins are present or absent in the cell.


What does it mean for a signal to be amplified?

The secondary messenger activates more than one thingy and each of those activate more than one protein.


How do primary messengers differ from secondary messengers?

The first one is the ligand, which is extracellular, and the second one is intracellular (like cAMP and epinephrine)


What type of cells does mitosis occur in?

Somatic Cells (body cells) and in some gametes (sex cells)


What are the ultimate purposes of mitosis in the body?

Growth, repair/regeneration, asexual reproduction


What is the cell cycle?

A series of events including growth, replication, and the division of the nucleus.


What is mitosis?

The division of the nucleus


How are mitosis and the cell cycle different?

The cell cycle is much broader; mitosis is only really one step of the cell cycle.


What are the four phases of the cell cycle?

G1, S, G2, and M.


What is the G1 phase of the cell cycle?

The Growth 1 or Gap 1 phase, where growth and production occurs within the cell.


What is the S phase of the cell cycle?

The Synthesis phase, where chromosomes and centrosomes are duplicated


What is the G2 phase of the cell cycle?

The Growth 2 or Gap 2 phase, where the cell checks for errors that may have taken place during the S phase.


What is the M phase of the cell cycle?

Mitosis, where the nucleus is split (also includes cytokinesis, where the cytoplasm is divided)


What is the ultimate purpose of the Gap Phases?

During these phases there are several regulatory events that make sure that the cell is ready to enter the S phase or the M phase.


What are centrosomes?

The place where microtubules develop, each containing two centrioles.


What is chromatin?

The name for chromosomes in the nucleus before they are bundled up during prophase


How is cytokinesis in plant cells different from animal cells?

In animal cells, pinching occurs by a contractile ring made from myosin and actin, called the cleavage furrow. In plant cells, the Golgi apparatus releases vesicles filled with glycoproteins and cellulose to meet in the center of the cell, forming a new cell wall, called the cell plate.


What are Chi Square Tests for?

Deciding whether a difference from an expected and observed outcome is due to change or an outside factor. It tests the null hypothesis.


What is the null hypothesis for Chi Square analysis?

Any difference between observed and expected data is due to chance


Which is better: a small sample size or a large sample size? Why?

A large sample size, since a small sample size would not give a clear picture of whether the difference between observed and expected data is significant.


The larger the chi-square value, the _________ the difference between observed and expected values.



What are the "degrees of freedom"?

The number of Chi-Squared categories you have minus 1


If a difference between observed and expected data occurs more than ______ percent of the time, then the difference is due to chance.



How does the amount of chromosomes in a cell change from the G1 phase to the G2 phase?

The number of chromosomes stays the same, but the amount of DNA present doubles.


What is the purpose of cell-cycle checkpoints?

To ensure that the cell is ready for replication, mitosis, or Cytokenisis


What does the G1 checkpoint determine?

It makes sure that the cell is ready to undergo DNA replication


What are the requirements for a cell to meet in order to enter the S phase?

The cell must be the appropriate size, there needs to be enough energy readily available, and the cell can't have any damaged DNA


How long might a halt in the G1 phase last?

The cell can halt for months (or years) until conditions are suitable.


What does the G2 checkpoint determine?

It makes sure that the DNA is not damaged and is replicated properly, and that the cell is large enough and has enough energy for mitosis.


What does the M checkpoint determine?

It makes sure that the spindle apparatus is properly attached to the kinetochores; each kinetochore has to be attached to at least one spindle.


When does the M checkpoint take place?

Towards the end of mitosis


What is the cell-cycle control system?

A complex network of regulatory proteins that makes sure that the cell-cycle occurs properly.


How does the cell-cycle work?

Through the cyclical activating and deactivating of proteins at the proper times.


What are two important proteins involved in the cell-cycle?

Cyclins and Cyclin-dependent protein kinase (Cdks)


What are Cyclins?

Proteins that do not have enzymatic activity but are responsible for activating Cyclin-dependent protein kinases (Cdks)


What are Cyclin-dependent protein kinases (Cdks)?

A kinase that can only act after being bound to a Cyclin


How are Cdks different from other kinases?

It must have the right phosphorylation state in order to hydrolize


What does Cdks phosphorylation depend on?

Other kinases.


What does Cdks dephosphorylation depend on?



How do kinases work?

They hydrolyze ATP in order to phosphorylate a protein.


What is the M-Cyclin Cdk complex?

The combination of M-Cyclin and M-Cdk that regulates the transition into mitosis


When does synthesis of M-Cyclin take place?

Before entering mitosis. The concentration will begin to increase immediately after Cytokenisis.


Why is M-Cdk inactive when it is formed?

To make sure that the cell is ready for mitosis.


What makes M-Cdk inactive when it is first created?

There will be both an activating and inhibitory phosphate attached.


How does M-Cdk become active?

The inhibitory phosphate is removed by an activating Phosphatase


What happens when the DNA is damaged or not replicated?

CHK1 and CDS1 become activated.


What happens once CHK1 and CDS1 become activated?

They phosphorylate Wee and Cdc25. Wee will become inactive, and Cdc25 will become active.


What is the role of Cdc25 in the cell?

It adds inhibitory phosphates to M-Cdk.


Why is it important for Cdc25 to be activated when DNA is damaged?

It inhibits M-Cdk, which will prevent the cell from moving forwards with the cell-cycle.


What is the role of Wee in the cell?

It removes inhibitory phosphates from M-Cdk.


Why is it important for Wee to be inactivated when DNA is damaged?

It activates M-Cdk, which would cause the cell to continue moving through the cell-cycle with damaged DNA.


Where does DNA replication begin?

The origin of replication


What is the Origin Replication Complex (ORC)?

A multi-protein complex made of regulatory proteins that are continually attached to the origin and act as a landing pad for other regulatory proteins.


What is Cdc6?

A regulatory protein involved in DNA replication.


Generally, what is the concentration of Cdc6 within a cell?

Low, but it rises in the beginning of the G1 phase.


Why does Cdc6 need to be present in the cell?

Cdc6 allows for the arrival of other Mcm proteins, which form the Pre-Replicative Complex (Pre-RC)


What is the S-Cyclin-Cdk Complex Pathway?

The pathway that takes place after the necessary proteins are in place for the S-Cdk to initiate DNA replication


What happens in the S-CDK Pathway?

S-Cdk and another kinase will phosphorylate the Origin Recognition Complex.


What prevents double replication from occurring in the S-CDK Pathway?

S-Cdk will phosphorylate the Cdc6 so that the Cdc6 disassembles from the pre-RC complex, phosphorylate the Mcm proteins and export them out of the nucleus, and stay in high concentration during G2 so that the Cdc6 and Mcm remain phosphorylated.