Chapter 9

Question 1

What is an activated carrier?

Answer 1

cofactor, non protein chemical compound that is bound to a protein and required for the protein’s biological activity
- commonly enzymes and cofactors -> considered “helper molecules” that assist in biochemical transformations

Question 2

How do cells communicate with each other? What are 4 categories of signaling as defined in the first few pages of chapter 9? What are examples of each?

Answer 2

Cell receptors detect external signals
-may involve direct contact with another cell or detection of a signal molecule

1. ) Endocrine Signaling - long distance (testosterone, insulin)
2. ) Paracrine Signaling - short distance ( signal traveling up and down spinal cord of developing embryo)
3. ) Synaptic Signaling - signal travels across a synapse ( nervous system signaling)
4. ) Direct Contact - cells must be in contact with each other, often binded by receptor

Question 3

Why is phosphorylation useful in intracellular signaling cascades? Give 3 examples from your textbook.

Answer 3

Phosphorylation acts as an on/off switch for protein enzymes - causes a conformational change -> alters substrate

Growth factor (see fig 9.10)
Insulin receptor and glycogen synthesis (see fig 9.7 and 9.8)
RTK’s and MAPK pathway

Question 4

Define: kinase, phosphatase

Answer 4

Kinase - adds phosphates (phosphorylate) -> enzyme that catalyzes transfer of a phosphate group from ATP to a specified molecule

Phosphatase - removes phosphates (de-phosphorylate) -> enzyme that catalyzes hydrolysis of organic phosphates in a specific (acidic or alkaline) reactions

Question 5

Why are intracellular signaling cascades such as the MAP kinase pathway necessary?

Answer 5

amplify intracellular messages –> leads to cellular responses, produce multiple intracellular signals for every one receptor that is bound

Question 6

Describe how the binding of a molecule of insulin to a cellular receptor leads to the conversion of glucose to glycogen

Answer 6

When insulin binds to insulin receptor, the receptor is phosphorylated –> another molecule can bind within that receptor after its phosphorylated –> new enzyme binds to molecule glucose synthase –> glucose is then synthesized and converted to glycogen inside the cells

Question 7

Look up an additional example of an intracellular signaling cascade in your textbook. Describe the signal, the intracellular signaling pathway, and the cellular response that occurs as a result.

Answer 7

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