12.11.1 Human Regulation: Endocrine Control and Signal-Transduction Pathways Flashcards Preview

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Flashcards in 12.11.1 Human Regulation: Endocrine Control and Signal-Transduction Pathways Deck (23)
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1
Q

Human Regulation: Endocrine Control and Signal-Transduction Pathways

A

• A signal molecule causes a response in a target cell in two basic ways:
1. The signal molecule will bind to a membrane receptor that will transmit the message
into the cell.
2. The signal molecule will enter the cell and bind to a receptor in the cytoplasm,
eliciting a response.
• A signaling pathway, such as the epinephrine pathway, can amplify a signal by activating several copies of the next enzyme in the pathway, triggering a dramatic response to a single signal.
• Signal-transduction pathways are mechanisms that link a chemical or mechanical stimulus to a

2
Q

endocrine system

A
  • To maintain homeostasis, cells must communicate. The
    endocrine system targets messages to specific organs using chemical signals. A signal can cause different responses depending on its target. For example, acetylcholine causes skeletal muscle to contract, but it causes heart muscle to relax.
  • Fat-soluble hormones can pass through the plasma membrane into the target cell, where they will bind to a receptor. The hormone-receptor complex may then act as a transcription factor.
  • The diagram to the right illustrates the operations of a
    G protein-linked receptor. The receptor protein is
    associated with a G protein, which is attached to GDP. The signal molecule binds to the receptor, which changes conformation and binds the G protein. The G protein activates by losing GDP and binding GTP. The activated G protein can activate another enzyme such as adenylate cyclase. Activated adenylate cyclase can convert ATP to cyclic AMP. Cyclic AMP acts as a second messenger, transmitting messages in the cell.
  • Signal amplification often involves lengthy signaling
    pathways. With each step the number of activated products increases. In the example to the left, note that for every epinephrine molecule that binds to a G protein-linked receptor, 100 G proteins activate. By the end of the cascade there are one million active glycogen phosphorylase enzymes! This mechanism allows the cell to use relatively small amounts of signal molecule to get a big response.
3
Q

Steroid hormones differ from other hormones because they

A
  • have intracellular receptors
4
Q

Homeostasis is

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  • a stable internal environment.
5
Q

The enzyme activated by cAMP is a

A
  • kinase

- protein kinase

6
Q

In the epinephrine signal pathway, one molecule of epinephrine can generate approximately _________________________molecule(s) of glucose from glycogen.

A
  • 1,000,000
7
Q

After a steroid passes through the cell membrane and binds with a receptor protein

A
  • the steroid/receptor complex passes into the nucleus and stimulates a transcription factor for a targeted piece of DNA.
8
Q

Steroid hormones

A
  • promote the transcription of certain regions of DNA
9
Q

True or false?

The hormone epinephrine enters target cells and triggers a signal-transduction pathway.

A
  • false
10
Q

A __________ is a mechanism that links a chemical or mechanical stimulus to a cellular response.

A
  • signal-transduction pathway
11
Q

Acetylcholine causes

A
  • cardiac tissue to relax
  • skeletal muscle to contract
  • stimulation of the release of other hormones
12
Q

In a non-steroid hormone signal, cAMP acts as a __________________________, which is able to transmit messages inside the cell.

A
  • second messenger
13
Q

True or false?

A hormone will always elicit the same response from every cell that it targets.

A
  • false
14
Q

In a G protein mediated signal, the G protein is activated when _________________________.

A
  • certain hormones link with a G-linked receptor
15
Q

Endocrine cells are capable of __________ chemical signals.

A
  • both sending and receiving
16
Q

True or false?

An example of a steroid hormone is testosterone.

A
  • true
17
Q

Which of the following is not part of the adenylate cyclase signal transduction pathway?

A
  • ADP
18
Q

A signal can be transmitted to a cell in two ways. If the signal is __________, it will bind to a receptor protein in the cell membrane. If the signal is _________, it will bind to a receptor protein within the cytoplasm of the cell.

A
  • water soluble; fat soluble
19
Q

Phosphorylation cascades are useful for cell signal transduction because

A
  • They amplify the signal
20
Q

The second messenger molecule formed by the enzyme adenylate cyclase from ATP is

A
  • cAMP

- cyclic AMP

21
Q

An activated G protein will in turn activate _____________________, which will convert ATP to __________________.

A
  • adenylate cyclase; cAMP
22
Q

Once the signal molecule has bound to the receptor, the following event occurs at the G protein-linked receptor:

A
  • displacement of GDP by GTP
23
Q

The endocrine system targets messages to specific organs using __________ signals.

A
  • chemical

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