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General Bio 1 for science majors > Chapter 11 > Flashcards

Chapter 11 Flashcards

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1
Q

What is quorum sensing?

A

A concentration of signaling molecules allows bacteria to sense local population density.

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2
Q

What is an example of quorum sensing?

A

Formations of biofilm. It is an aggregation of bacterial cells adhered to a surface.

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3
Q

What can be an approach for alternative antiobiotic treatment?

A

Interfering with the signaling pathways used in quorum sensing.

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4
Q

What do the Saccharomyces cerevisiae yeast cells use when mating?

A

A series of steps called signal transduction pathway.

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5
Q

How do cells in multicellular organisms communicate?

A

Signaling molecules; local or broad.

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6
Q

What is the local signaling in animal cells?

A

Direct contact through cell junctions that directly connect the cytoplasm of adjacent cells. Signaling substances in the cytosol can pass between adjacent cells.

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7
Q

When is local signaling important?

A

In embryonic development, immune response, and maintaining adult stem cell populations.

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8
Q

What is a type of local signaling?

A

Paracrine signaling.

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9
Q

What is paracrine signaling?

A

Animal cells communicate using secreted messenger molecules that travel only short distances.

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10
Q

What is an example of paracrine signaling?

A

Growth factors that stimulate nearby target cells to grow and divide.

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11
Q

What is synaptic signaling?

A

A neurotransmitter is released in response to an electric signal.

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12
Q

What can affect synaptic signaling?

A

Drugs used to treat depression, anxiety, and post traumatic stress disorder (PTSD).

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13
Q

What is used during long distance signaling?

A

Hormones.

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14
Q

How do hormones reach their target?

A

By traveling to target cells via the circulatory system.

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15
Q

What were the three processes Earl W. Sutherland discovered?

A

Signal reception, signal transduction, cellular response.

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16
Q

What happens in signal reception?

A

The target cell detects a signaling molecule that binds to a receptor protein on the cell surface.

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17
Q

What happens in signal transduction?

A

The binding of the signaling molecule alters the receptor and initiates a signal transduction pathway; often in a series of steps.

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18
Q

What happens in cellular response?

A

The transduced signal triggers a specific response in the target cell.

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19
Q

What is a ligand?

A

A signal molecule that is highly specific.

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20
Q

What is usually the first step in transduction of the signal?

A

A shape change in a receptor.

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21
Q

Where are signal receptors located?

A

Most are plasma membrane proteins, but others are located inside the cell.

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22
Q

What are GPCRs?

A

G protein coupled receptors. They are the largest family of cell surface receptors.

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23
Q

What are the three main types of membrane receptors?

A

G protein coupled receptors, receptor tyrosine kinases, and ion channel receptors.

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24
Q

What do GPCRs do?

A

They are transmembrane cell surface receptors that work with G proteins. They use GTP, and are extremely widespread and diverse in function.

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25
What are receptor tyrosine kinases (RTKs)?
Membrane receptors that catalyze the transfer of phosphate groups from ATP to another protein. It can trigger multiple signal transduction pathways at once.
26
What is the abnormal functioning of RTKs associated with?
Many types of cancers.
27
What is a ligand gated ion channel receptor?
It acts as a gate that opens and closes when the receptor changes shape. When a signal molecule binds as a ligand to the receptor, the gate allows specific ions (like Na+ or Ca2+) through a channel in the receptor.
28
Where are intracellular receptor proteins found?
In the cytoplasm or nucleus of target cells.
29
What kind of chemical messengers can readily cross the membrane and activate receptors?
Small or hydrophobic chemical messengers.
30
What are examples of hydrophobic messengers?
Steroids and thyroid hormones of animals.
31
What can act as a transcription factor?
An activated hormone receptor complex is capable of turning on or off specific genes.
32
What can multistep pathways do?
Amplify a signal. They provide more opportunities for coordination and regulation of the cellular response.
33
What initiates the first step in molecular interaction chains?
The binding of a signaling molecule to a receptor.
34
What is commonly used for regulating protein activity?
Phosphorylation and dephosphorylation of proteins.
35
What do protein kinases do?
Transfer phosphates from ATP to protein, a process called phosphorylation.
36
What creates a phosphorylation cascade?
Relay molecules in a signal transduction are protein kinases.
37
What is dephosphorylation?
Protein phosphatases rapidly remove the phosphates from proteins.
38
What are second messengers?
Small, nonprotein, water soluble molecules or ions that spread throughout a cell by diffusion.
39
When do second messengers participate in pathways?
When initiated by GPCRs and RTKs.
40
What are common second messengers?
Cyclic AMP and calcium ions.
41
What is cyclic AMP (cAMP)?
A small molecule produced from ATP, and is one of the most widely used second messengers.
42
What is adenylyl cyclase?
An enzyme in the plasma membrane that converts ATP to cAMP in response to an extracellular signal.
43
What are components of cAMP pathways?
G proteins, GPCRs, and protein kinases. cAMP usually activates protein kinase A, which phosphorylates various other proteins.
44
What inhibits adenylyl cyclase?
G protein systems.
45
What can help explain how certain microbes cause disease?
The role of cAMP in G protein signaling pathways.
46
What does the cholera bacterium Vibrio cholerae do?
Produces a toxin that modifies a G protein so that it is stuck in its active form. This protein continually makes cAMP, causing intestinal cells to secrete large amounts of salt into the intestines. Water follows by osmosis, and an untreated person can die from loss of water and salt.
47
What second messenger is used more than cAMP?
Calcium ions (Ca2+).
48
Why are calcium ions able to act as second messengers?
Because its concentration in the cytosol is normally much lower than the concentration outside the cell. A small change in number of calcium ions thus represents a relatively large percentage change in calcium concentration.
49
What are additional second messengers?
Inositol triphosphate (IP3) and diacylglycerol (DAG). They are produced by cleavage of a certain kind of phospholipid in the plasma membrane.
50
What is the output response?
The cell's response to an extracellular signal.
51
Where does a signal transduction pathway lead to?
Regulation of one or more cellular activities. The response may occur in the nucleus or in the cytoplasm.
52
What regulates the synthesis of enzymes or other proteins?
Signaling pathways turning genes on or off in the nucleus.
53
What else can a signal cause?
Regulate the activity of proteins rather than synthesis. A signal could cause opening or closing of an ion channel in the plasma membrane or a change in the activity of a metabolic enzyme.
54
What are four aspects of signal regulation?
Amplification of the signal (and response), specificity of the response, overall efficiency of response enhanced by scaffolding proteins, termination of the signal.
55
What do enzyme cascades do?
Amplify the cell's response to the signal. At each step, the number of activated products can be much greater than in the preceding step.
56
What are scaffolding proteins?
Large relay proteins that several other relay proteins are attached to. They can increase the signal transduction efficiency by grouping together different proteins involved in the same pathway. They may also help activate some of the relay proteins.
57
What are inactivation mechanisms?
An essential aspect of cell signaling. If the concentration of external signaling molecules falls, fewer receptors will be bound and unbound receptors revert to an inactive state.
58
What happens when cells are infected, damaged, or at the end of their functional life?
Programmed cell death, apoptosis being the best understood type.
59
What happens in programmed cell death and apoptosis?
Components of the cell are chopped up and packaged into vesicles that are digested by scavenger cells. Apoptosis prevents enzymes from leaking out of a dying cell and damaging neighboring cells.
60
How is apoptosis triggered?
In worms and other organisms, it is triggered by signals that activate a cascade of "suicide" proteins in the cells destined to die.
61
Can apoptosis be stopped?
In the nematode worm C. elegans, a protein called C e d-9 in the outer mitochondrial membrane serves as a master regulator of apoptosis. C e d-9 acts as a brake in the absence of a signal promoting apoptosis.
62
What is the apoptotic pathway?
Activates proteases and nucleases that cut up proteins and DNA of the cell. The main proteases of apoptosis are called caspases. The chief caspase in the nematode is called C e d-3.
63
What can apoptosis be triggered by?
In humans and other mammals, it can be triggered by signals from outside the cell or inside it. Internal signals can result from irreparable DNA damage or excessive protein misfolding.
64
What is apoptosis important for?
It is essential for the development and maintenance of all animals. It is a normal part of development of hands and feet (and paws).
65
What could apoptosis be involved in?
Some diseases, like Parkinson's and Alzheimer's. Interference with apoptosis may contribute to some cancers.

General Bio 1 for science majors (11 decks)

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