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Bio I > Chapter 7 > Flashcards

Chapter 7 Flashcards

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1
Q

What types of signals do cells receive?

A

Cells receive autocrine, juxtacrine, paracrine signals, and hormones.

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2
Q

What are autocrine signals?

A

Autocrine signals affect the cells that make them.

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3
Q

What are juxtacrine signals?

A

Juxtacrine signals affect adjacent cells.

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4
Q

What are paracrine signals?

A

Paracrine signals diffuse to and affect nearby cells.

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5
Q

What are hormones?

A

Hormones are carried through the circulatory system of animals or the vascular system of plants.

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6
Q

What is a signal transduction pathway?

A

A signal transduction pathway involves the interaction of a signal molecule with a receptor, the transduction of the signal via a series of steps within the cell, and effects on the function of the cell.

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7
Q

What law does the binding of a signal ligand to its receptor obey?

A

The binding of a signal ligand to its receptor obeys the chemical law of mass action.

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8
Q

What is a key measurement of the strength of binding?

A

A key measurement of the strength of binding is the dissociation constant (Ko).

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9
Q

Where can receptors be located in relation to the target cell?

A

A receptor may be located in the cell membrane or inside the target cell.

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10
Q

What types of receptors are located in the cell membrane?

A

Receptors located in the cell membrane include ion channels, protein kinases, and G protein-coupled receptors.

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11
Q

What are intracellular receptors?

A

Intracellular receptors include steroid hormone receptors in animals.

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12
Q

How can a lipid-soluble ligand such as a steroid hormone interact with a cell?

A

A lipid-soluble ligand such as a steroid hormone may enter the cytoplasm or the nucleus before binding.

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13
Q

What amplifies the response to receptor binding?

A

A protein kinase cascade amplifies the response to receptor binding.

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14
Q

What are the second messengers involved in signal transduction?

A

Second messengers include cyclic AMP (cAMP), Inositol trisphosphate (IP3), diacylglycerol (DAG), nitric oxide, and calcium ions.

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15
Q

How can signal transduction be regulated?

A

Signal transduction can be regulated in several ways.

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16
Q

What are the cellular responses to signals?

A

The cellular responses to signals may include the opening of ion channels, the alteration of enzyme activities, or changes in gene expression.

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17
Q

What happens when enzymes are activated in a signal transduction pathway?

A

Activated enzymes may activate other enzymes in a signal transduction pathway, leading to impressive amplification of a signal.

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18
Q

What are gap junctions?

A

Small pores in animal cell membranes that allow communication between adjacent cells.

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19
Q

What structures form gap junctions?

A

Protein structures called connexons.

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20
Q

What can pass through gap junctions?

A

Small signal molecules and ions.

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21
Q

What are plasmodesmata?

A

Larger pores in plant cells that connect adjacent cells.

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22
Q

What do plasmodesmata traverse?

A

Both cell membranes and cell walls.

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23
Q

What narrows the opening of a plasmodesma?

A

The desmotubule.

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24
Q

What can be inferred from existing organisms about cell communication?

A

The evolution of cell communication and tissue formation.

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25
Which organisms provide insight into the evolution of cell communication?
Certain green algae.
26
What do modern organisms provide clues about?
The evolution of cell-cell interactions and multicellularity.
27
How many eukaryotic cells does a human have?
About 60 trillion eukaryotic cells.
28
What are the components that make up a human or a rose plant?
Groups of cells specialized into tissues and groups of tissues in organs.
29
What are the steps in the embryonic development of tissues and organs?
1. Migration of cells to form a group 2. Organization of cells in the cluster 3. Specialization of cells into tissues 4. Connections between cells.
30
What has evolved over time along with complex multicellular organisms?
The division of biological labor among specialized cells.
31
When did single-celled organisms arise after the formation of Earth?
About 500 million to a billion years after the formation of Earth.
32
When is the first evidence of true multicellular organisms dated from?
More than a billion years after single-celled organisms.
33
How many times did multicellularity probably arise?
Several times.
34
What is a challenge in studying the evolutionary origin of multicellularity?
It happened so long ago, and the closest unicellular relatives of modern animals and plants probably existed hundreds of millions of years ago.
35
What are the steps in the transition from single-celled to multicellular organisms?
1. Aggregation of cells into a cluster 2. Intercellular communication within the cluster 3. Specialization of some cells within the cluster 4. Organization of specialized cells into groups (tissues)
36
What key event is necessary for the coordination of activities in multicellular organisms?
The evolution of intercellular communication.
37
How can we visualize the evolution of multicellularity?
By examining the Volvocine line of aquatic green algae (Chlorophyta), which ranges from single cells to complex multicellular organisms with differentiated cell clusters.
38
What are some examples of organisms in the Volvocine line?
1. Chlamydomonas (single-celled organism) 2. Gonium (small cell clusters) 3. Pandorina and Eudorina (larger cell clusters) 4. Pleodorina (a colony of somatic and reproductive cells)
39
What are plasmodesmata?
Plasmodesmata are channels that allow communication and transport between plant cells.
40
Why are plasmodesmata vital in plants?
They are vital because the vascular system in plants lacks tiny vessels (capillaries) for transporting gases and nutrients.
41
How do plants transport hormones?
Plants rely on rapid diffusion through plasmodesmata to transport hormones from the site of production to the site of action.
42
What is inadequate for hormone movement in plants?
Simple diffusion from plant cell to cell across cell membranes is inadequate for hormone movement.
43
Can larger molecules pass through plasmodesmata?
Yes, larger molecules or particles can pass between cells via plasmodesmata.
44
How can some viruses move through plasmodesmata?
Some viruses can move through plasmodesmata by using 'movement proteins' to assist their passage.
45
What are connexons?
Connexons are channel structures composed of six subunits of the integral membrane protein connexin.
46
What do connexons form between adjacent cells?
Connexons come together to form a gap junction that links the cytoplasms of the two cells.
47
What is the diameter of the channel pores in gap junctions?
The channel pores are about 1.5 nanometers (nm) in diameter.
48
What can pass through gap junctions?
Gap junctions allow the passage of small molecules and ions, but not large molecules.
49
How do gap junctions function in the lens of the mammalian eye?
Gap junctions allow rapid and efficient diffusion of materials between lens cells, which are connected by numerous gap junctions. ## Footnote This is crucial as only peripheral lens cells are close enough to the blood supply for adequate nutrient diffusion.
50
What are plasmodesmata?
Plasmodesmata are membrane-lined tunnels that traverse the thick cell walls separating plant cells.
51
How do plasmodesmata differ from gap junctions?
Plasmodesmata are lined by the fused cell membranes themselves, unlike gap junctions which are made of integral membrane proteins.
52
What is the diameter of a plasmodesma?
The diameter of a plasmodesma is about 6 nm.
53
What fills most of the opening of a plasmodesma?
A tubule called the desmotubule, derived from the endoplasmic reticulum, fills most of the opening of the plasmodesma.
54
What can move between plant cells through plasmodesmata?
Typically, only small metabolites and ions can move between plant cells through plasmodesmata.
55
What is the hallmark of multicellular organisms?
Their ability to have specialized functions in subsets of cells within their bodies.
56
How do cells communicate with one another?
Cells communicate through intercellular signals that can travel through the circulatory system or through direct communication methods.
57
What are the specialized intercellular junctions in animal cells?
Gap junctions.
58
What are the specialized intercellular junctions in plant cells?
Plasmodesmata.
59
The final protein kinase in the Ras signaling cascade
MAPK
60
What changes enzyme activities?
Enzyme activities change in response to signals.
61
How are enzymes modified during signal transduction?
Enzymes are often modified either covalently or noncovalently.
62
What is an example of a covalent modification of an enzyme?
Addition of a phosphate group to an enzyme by a protein kinase is a covalent change.
63
What is an example of a noncovalent modification of an enzyme?
cAMP binding is a noncovalent modification.
64
What effect do modifications have on enzymes?
Both types of modifications change the enzyme's shape, activating or inhibiting its function.
65
What happens during enzyme activation?
The shape change exposes a previously inaccessible active site, allowing the enzyme to perform a new cellular role.
66
What does the G protein-mediated protein kinase cascade stimulated by epinephrine result in?
It results in the activation by cAMP of protein kinase A.
67
What is the effect of protein kinase A on glycogen synthase?
Glycogen synthase is inactivated when a phosphate group is added to it by protein kinase A.
68
What is the consequence of inhibiting glycogen synthase?
The epinephrine signal prevents glucose from being stored in the form of glycogen.
69
What happens to phosphorylase kinase when a phosphate group is added?
Phosphorylase kinase is activated.
70
What is the role of glycogen phosphorylase?
Glycogen phosphorylase results in the liberation of glucose molecules from glycogen.
71
What do ion channels respond to?
Ion channels respond to signals by opening or closing.
72
How do ion channels function in cell signaling?
Ion channels can function as receptors in cell signaling.
73
What happens when a receptor is stimulated in the nervous system?
Stimulation of a receptor by light, sound, or touch can lead to channel opening.
74
What is the role of Ca+ channels in muscle contraction?
Ca+ channels in the ER membrane open in response to signal transduction to modulate muscle contraction.
75
What is oxytocin's role in ion channel responses?
Oxytocin binds to a G protein-coupled receptor, leading to signal transduction and ion channel activity.
76
Where is the G protein-coupled receptor for oxytocin expressed?
The receptor is expressed in brain tissue as well as muscles involved in birth and lactation.
77
What pathway does oxytocin activate?
Oxytocin activates the IP3-DAG pathway.
78
What does the activation of the oxytocin receptor release?
It releases Ca2+ into the cytoplasm via ion channels.
79
How does Ca2+ affect nerve cell activity in the brain?
Ca2+ indirectly stimulates nerve cell activity by opening ion channels for Na+.
80
What is the first step in the signaling pathway involving oxytocin?
Oxytocin
81
What does oxytocin bind to?
Receptor
82
What is activated by the receptor after oxytocin binds?
G protein activation
83
What is the next step after G protein activation?
IP3 signal transduction
84
What occurs after IP3 signal transduction?
Ca channel opening
85
What channel opens after the Ca channel?
Na* channel opening
86
What do liver cells respond to?
Liver cells respond to epinephrine.
87
What do G proteins activate in liver cells?
G proteins activate the synthesis of the second messenger CAMP.
88
What does cyclic AMP initiate?
Cyclic AMP initiates a protein kinase cascade.
89
What is the effect of the protein kinase cascade?
The cascade amplifies the epinephrine signal.
90
What processes does the cascade affect?
The cascade inhibits the conversion of glucose to glycogen and stimulates the release of previously stored glucose.

Bio I (4 decks)

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