AP Biology 4.1 Cell Communication

Practise AP Biology 4.1 questions by distinguishing direct contact, local regulators, synaptic signals and long-distance hormone communication.

Exam points

distinguish direct-contact, local-regulator and long-distance hormone signaling
identify synaptic chemical communication and endocrine transport to distant targets
classify juxtacrine and paracrine signaling from cell-contact or diffusion evidence

A portion of the human immune system response to an invading

pathogen is shown below.

Macrophages are white blood cells that ingest invading pathogens.

After digesting the pathogen, macrophages present the antigens from

the pathogen to helper T cells in the immune system. These helper T

cells then secrete chemical signals called cytokines. The cytokines can

travel short distances to activate nearby cytotoxic T cells, which will

kill infected cells. Some cytokines will activate the enzyme adenylyl

cyclase in nearby B cells to produce cyclic AMP (cAMP). cAMP will

then activate the production of antibodies in the B cells.

(a)

Part A

(i)

(i) Describe the characteristics of juxtacrine signaling.

(ii)

(ii) Draw a square around the step (1, 2, 3, or 4) in the figure that

illustrates an example of juxtacrine signaling.

[Maximum number: 1]

Based on the information provided, which of the following best justifies the claim that osteocalcin is a hormone?

The phosphorylation of the insulin receptor causes a response in osteoblast bone cells.

The osteoblasts in the bone secrete osteocalcin, which causes cells in the pancreas to change their activity.

The change in expression of E s p changes the insulin receptor activity of the osteoblast.

The activation of the osteocalcin by a bone cell is pH dependent.

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