Problem Set #11

Question 1

What is a receptor?

Answer 1

proteins that are activated or deactivated in the presence of the signal to trigger a cellular change

Question 2

What is a ligand?

Answer 2

bind chemicals (used by receptors) that provide a stimulus

Question 3

What are two common ways plants accomplish this signal transduction for many different receptors?

Answer 3

Plants often use calcium ions or protein kinases for signal transduction.

1. nucleus to change gene expression
2. proteosome to modulate protein degradation

Question 4

From what 4 cellular (or extracellular) compartments can calcium be imported into the cytosol under stress condition

Answer 4

1. extracellular
2. mitochondria
3. vacuole
4. ER

Question 5

4) Blue light is perceived by plants using __________ receptors and red light is perceived using ___________ receptors. Both of these receptors consist of chromophores covalently linked to proteins. The chromophore of phytochrome is a ___________ that undergoes a __________ isomerization when it absorbs red light.

Answer 5

1. cryptochrome
2. phytochrome
3. tetra pyrole
4. trans to cis
5. far red

Question 6

Why are hormones important for multicellular organisms? In general, how do hormones work?

Answer 6

Hormones allow cells in a multicellular organism to communicate, and coordinate responses.
They bind receptor proteins at the plasma membrane or inside the cell and often have multiple receptors, it’s all very complicated and tightly regulated

Question 7

What is the major form of auxin in plants? What form of auxin is used for rooting plant shoot cuttings?

Answer 7

IAA; IBA

Question 8

Indole acetic acid is made in the shoot tip and moves down through the rest of the plant. Does auxin passively diffuse or is it actively transported? What is this movement of auxin through the plant called?

Answer 8

Polar transport; actively transported

Question 9

Name a describe 5 types of plant trophic movements mediated by auxin.

Answer 9

Gravitropism: direction of gravity
Hydrotropism: toward water
Phototropism: towards light
Chemotropism: toward chemical signal
Thigmotropism

Question 10

Indole acetic acid can be synthesized from what amino acid?

Answer 10

tryptophan

Question 11

list 5 horticultural uses for auxins

Answer 11

1. prolonging dormancy
2. promote root growth on cuttings
3. weed removal
4. prevent premature falling of fruit
5. induce parthenocarpy

Question 12

There are many different compounds that are active cytokinins. What chemical core is common to all cytokinins?

Answer 12

Adenine

Question 13

The last enzyme in ethylene biosynthesis is called?

Answer 13

ACC synthase

Question 14

If ACC synthase is made inactive in a fruit bearing plant will the fruit rot more quickly or slowly than the same fruit from a plant with a functional enzyme?

Answer 14

more slowly

Question 15

Which 2 hormones are important for regulating plant defenses against herbivory and infection?

Answer 15

salicylic aci

jasmonic acid

Question 16

The biosynthesis of which 4 phytohormones use the terpenoid pathway?

Answer 16

1. cytokinins
2. gibberellins
3. bassinosteroids
4. abscisic acid

Question 17

2 phytohormones use a histidine kinase type receptor. what are they?

Answer 17

ethylene and cytokinin

Question 18

3 phytohormones use a receptor that stimulates proteasome-dependent degradation of a repressor protein to activeate gene transcription. what are they?

Answer 18

auxin, gibberellin and jasmonic acid receptors