Unit 4 Exam

Question 1

On the following sketches, label the guard cell,
stomata, K+ , and H2O. Explain why the stoma
opens when K + accumulates in the guard cells
and closes when the guard cells lose K+ .

Answer 1

water follows k+. If they enter, the cell is turgid and full of water, and stomata open. Stomata close when cells lose
K+ and water.

Question 2

What plant hormone is produced in response to
water deficiency?

Answer 2

Abscisic acid (ABA)

Question 3

How does ABA help deal w drought

Answer 3

It travels from roots to rest of plants. It produces NO to tell the guard cells to close the stoma to conserve water.

Question 4

What does NO do?

Answer 4

It closes stoma to conserve water. It maintains seed dormancy.

Question 5

What plant hormone is responsible for ripening
of fruit?

Answer 5

ethylene

Question 6

What environmental conditions would we expect
stomata to be open? Closed?
Why do plants close their stomata when CO2
levels are high inside the leaf?
Why do plants open their stomata when exposed
to light?

Answer 6

Open: In the daytime (light), high humidity, low CO2

Closed: nighttime, drought, low humidity, windy, high CO2, ABA.

high CO2 concentration tells the plant that they have sufficient supply for photosynthesis. They don’t need more CO2.

In the light, plants are undergoing photosynthesis, thye need CO2.

Question 7

Are the number of genes that turn on/off the
same in roots and leaves for the different
stresses?

Answer 7

plant tissues respond differently to each stress and the length of time they experience the stressful environment.

Question 8

Which stress generally resulted in the greatest
number of genes that were turned on/off?

Answer 8

Cold stress resulted in more genes changing their expression.

Question 9

Which two stresses generally resulted in
dissimilar number of genes that were turned
on/off in leaves and roots?

Answer 9

3 and 27 hours of Salt and osmotic stress exposure led to very dissimilar gene expression in roots and leaves makes sense because they experience stresses very differently.

Question 10

How do plants respond to environmental stress?

Answer 10

plants change their gene expression to respond to environmentaln sicne they cant move. They have more genes for more genetic plasticity.

Question 11

How does this figure highlight that response?

Answer 11

It shows that plants can either increase or decrease expression of gene is response to differfent stresses. they cAN also change over time.

Question 12

What is the main conclusion that you can draw
from this results figure with environmental stressors

Answer 12

different genes respond differently to same environmental stressor. same gene does not resond to different stressors the same.

Question 13

What does this figure suggest about guard cells
and light?

Answer 13

guard cells respond to light via changes in membrane potential. stomata open in response to lgiht,

Question 14

guard cell resting membrane potential

Answer 14

-50mV

Question 15

Can guard cells change the
membrane potential when exposed to light? What happens to membrane potential when light
hits guard cells?

Answer 15

Their membrane potential becomes more negative (hyperpolarizes). Positively charged ions (H+) move out of guard cell. K+ moves in and replaces lost H+ and water follows K+ causing guard cells to swell and open stomata.

Question 16

What hormone do plants release when water
stressed?

Answer 16

ABA

Question 17

What part of the plant releases ABA? Does ABA cause guard cells to close?

Answer 17

roots release when plant is water stressed. it travels to guard cells to signal them to close. ABA does not cause guard cells to close. It is NO. ABA stimulates production of NO which causes the guard cells to close the stomata.

Question 18

Based on this figure how does a plant respond to
high levels of CO2?

Answer 18

Plants close stomata in High CO2. High CO2 conc tells plant that they have enough CO2 for photosynthesis. They don’t need more CO2, so they close stomata and conserve water.`

Question 19

Which direction are
potassium ions and sucrose moving in the guard
cells when exposed to high CO2?

Answer 19

K+ and sucrose move out of cells in high CO2. They will move back in once CO2 returns to normal.

Question 20

Do more genes tend to increase or decrease
transcription in response to stress?

Answer 20

mroe decrease transcription.

Question 21

Do more genes tend to change transcription
levels when stressed for short periods of time or
long periods of time?

Answer 21

The longer a plant is stressed, the more genes that start to chnage transcription levels.

Question 22

Do plants generally have smaller or larger
genomes and number of genes compared to
animals? Explain the difference

Answer 22

plants hace more genes and larger genomes than animals because they can’t move and need to be more genetically plastic to respond to enviornmental changes.

Question 23

What is the important role guard cells play in
plants? How is their role related to
photosynthesis, water transport, and water
conservation?

Answer 23

Co2 moves into plants at the stomata and O2 leaves via stomata.
Water moves from roots to rest of plant due to transpiration of water at stomata. stomata must be open for water to flow.
If the plant is water stressed, stomata will close to conserve water.
No photosynthesis and no water transport thruout plant.
guard cells help balance photosynthesis and water transpirtation trade-offs.

Question 24

What causes water to move from the roots to
the leaves in a plant?

Answer 24

evaporation (transpiration) of water through stoma results in pulling of water thoruh all the vessles (like a straw)

Question 25

Explain what emergent property of
hemoglobin explains this pattern. Why is
hemoglobin able to carry more oxygens than water?

Answer 25

Hemoglobin is a protein composed of four subunits. These individual proteins show emergent property of cooperativity. Hemoglobin carries more oxygen than water because of the cooperativity emergent property among the four independent hemoglobin protiens.

Question 26

Where is this property of cooperativity of hemoglobin easily observable on the
graph?

Answer 26

At lower concentrations of oxygen between 3kpa and 10kpa. The amount of oxygen that is bound to hemoglobin increases very dramitcally in small increase in oxygen concentration.

Question 27

How is hemoglobin’s emergent property,
cooperativity, produced?

Answer 27

Once first of 4 hemoglobin molecues binds to oxygen, the other proteins change shape and increase their affinity for oxygen.

Question 28

What environmental factors trigger the switchover
from lysogenic to lytic mode?

Answer 28

during lysogeny a phage is essentially silent and undetected unitl there is an enviornmental signal such as UV radiation that damages host DNA and activates proteases to trigger a switchover from lysogenic to lytic mode. Also, if there are many host cells and “food” viruses could switch to lytic. Phages in lysogenic do not kill hosts. the phage genome repliactes when host replicates itself.

Question 29

describe lytic mode of repro

Answer 29

results in release of new phages by lysis (and death) of the host cell)

Question 30

describe lysogenic mode of repro

Answer 30

the viral genome becomes incorporated into the bacterial host chromosome as a phropahge, is repliacted along with the chromosome, and does not kill the host.

Question 31

What does a hill plot quantify? A slope = 1 suggests
what? What does a slope that is greater than 1 suggest? Where on this graph is hemoglobin’s
emergent property apparent? Why does myoglobin
have a slope of 1? Does it have cooperativity?

Answer 31

hill plots are used to quanitfy cooperativigty among molecules. Slope =1 means no cooperativity. Myoglobin has a slope of 1 because it is made of one proten and has no quarternary structure,s o no opportunity to be cooperative. slopes >1 mean positive cooperativity. Hemoglobin slope = 3 so once first heme binds to oxygen, other 3 increase affinity to oxygen due to positie cooperativity.
Hemoglobin has no copperativity (slope = 1) when no oxygen or when all 4 are bound.

Question 32

Explain the role of cooperativity in both loading and
unloading oxygen using this graph

Answer 32

Hemoglobin binds to O2 reversibily lodaing O2 in the lungs or gills and unloading elsewhere int he body. It is enhanced by cooperativigty between hemoglobin subunits. when O2 binds to one subunit, the shape changes slightly and icnreases affinity on all other subunits. When foru O2 are bound and one unloads, the other 3 more readily unload O2 because the shape change decreases their affinity.

Question 33

Why is cooperativity good for delivery and pick up of
oxygen in the body

Answer 33

It lets. hemoglobin release more O2 in tissues w low O2 (muscles) because it has less affinity, but when O2 concentrations are high (lungs) they have high affinity, allowing them to pick up more O2.

Question 34

As pH of the blood decreases, the affinity of
hemoglobin for oxygen decreases, and oxygen is
released from hemoglobin. What is this called

Answer 34

bohr shift

Question 35

Based on the figure above, when oxygen
concentration is 40mmHg, is more oxygen bound to
hemoglobin in pH 7.2 or 7.6? Why does that make
sense? Where is pH in blood low?

Answer 35

AT 40mmHg, more O2 is bound to hemoglobin when pH is 7.6. Blood near muscles and other cells that perform cellular respiration is more acidic due to more CO2 in blood. Hemoglobin will lose affinity for O2 and drops off O2 to cells that need it for cellular respiration.

Basically, at lower pHs, hemoglobin has less of an affinity for O2 because the other cells need it for CR,

Question 36

What is a prophage? Is it part of the lytic or
lysogenic lifecycle?

Answer 36

a prophage is viral DNA that has integrated into bacterial chromosome as part of LYSOGENIC cycle.

Question 37

Fetal hemoglobin and adult hemoglobin are
different, as the dissociation curves indicate in the
figure. Describe how they differ in their ability to
bind to oxygen at low oxygen levels.

Answer 37

Fetal hemo is saturated at lower O2 partial pressure.
It has a greater affinity for O2 when O2 conc is low compared to adults. This allows it to absorb O2 from mother’s blood.

Question 38

What determines whether lambda phage is in lytic
or lysogenic life cycles?

Answer 38

Conc of cro and c1 proteins detwermind if phage is lytic or lysogenic

Question 39

What are the two proteins that act as the molecular
switch for phages to enter lytic and lysogenic
stages?

Answer 39

Cro promotes lytic cycle.
C1 Promotes lysogenic.
If cl is abundant, then cro is turned off and virus is lyso.
If cro is abundant, cl is turned off and virus is lytic

Question 40

How many promoter sequences are involved? How
many operator sequences are involved? If cI is
bound to operator 1, can RNA polymerase bind to
the Pr promoter and make cro protein?