Botany – Plant Metabolism

I. Metabolism – __________________________________________________

A. ______________________ – the process by which plant cells capture

the radiant energy (E) of sunlight & store it in sugar (in the form of

carbohydrates).

B. ______________________ – the process by which plant cells release

the E stored in sugar & capture it in ATP.

1. ATP – ____________________________________________

II. Photosynthesis begins with light

A. What makes up light?

1. Review the diagram over the visible spectrum of light

2. As wavelength _____________________, energy

_____________________________

a. Red has the ____________ wavelength, but carries the

________________ energy

b. Violet has the ___________ wavelength, but carries the

________________ energy

c. UV light carries ___________ energy then visible light

1) Why is UV light dangerous?

d. Infrared light carries _________ energy than visible light.

1) This is the same thing as ________

B. Why do we see colors?

Why are plants green?

Why should a greenhouse never have green glass?

C. Not all light that reaches plants is the same.

Review how light level changes as you pass through the strata of a

tropical rain forest.

Images modified from the following sources: http://homepages.paradise.net.nz/hellyer/images/Rainforeststrata.jpg

http://www.yellowheadcs.ca/images/Sun%20clip%20art.gif

Emergent layer - ______ light quality; therefore it is the _____ efficient.

These plants primarily rely upon just have __________________.

Undergrowth - _______ light quality. Mostly only the high energy

Wavelengths of violet, blue, and green get through. These plants

must be the _____ efficient. They primarily rely upon

__________________.

III. Plants capture the E of light with photosynthetic pigments

A. Review the diagram over the absorption of the photosynthetic

pigments

1. ________________________, in land plants, is the main light-

capturing pigment.

a. Chlorophyll a is a _________________________pigment

b. It is most efficient at ___________________________&

_____________________________ wavelengths

2. Chlorophyll b serves as an accessory pigment

a. Chlorophyll b is a _______________________ pigment

b. It is most efficient at __________________________ &

_____________________________wavelengths

3. Chlorophyll transmits & reflects light in the

_________________________ & ________________________

wavelengths, giving plants their green color

4. Chlorophyll is located in the __________________________of

chloroplasts

5. __________________________ (carotene & xanthophylls) are

accessory pigments that allow the utilization of a wider variety of

wavelengths of light.

a. Carotenoids are yellow, orange, or red pigments

b. They are most efficient at _________________________

& _____________________________ wavelengths

6. Why do shaded plants have more carotenoids?

IV. Overview of Photosynthesis

A. A SUM OF THE REACTION OF PHOTOSYNTHESIS

B. Review of the structures of a chloroplast

1. Double membrane bound, stacks of

____________________________ membranes called

____________________________, & a fluid called the

_____________________________.

Image modified from: http://micro.magnet.fsu.edu/cells/chloroplasts/images/chloroplastsfigure1.jpg

C. Photosynthesis can be viewed as a coupled oxidation / reduction

reaction

1. Oxidation – the loss of ___________________________ &/or

_____________________________ (the loss of ______________)

a. water is oxidized as free ________________________ is

created

2. _____________________________ – the gain of electrons &/or

hydrogen (the gain of E)

a. carbon dioxide is reduced as it is changed to

_____________________________ (carbohydrates)

D. Photosynthetic reactions can be divided into light-dependent & light-

Independent. THESE REACTIONS BOTH OCCUR IN EVERY SINGLE

PLANT SIMULTANEOUSLY DURING THE DAY.

1. Light-dependent reactions (require light or they will not occur)

a. Take place on the ______________________________

b. Water molecules are split (oxidized) to produce oxygen

and H⁺

1) H⁺ + NADP⁺ à NADPH

c. The energy of sunlight excites the photosynthetic

pigments of _____________________________

1) They eject electrons, which travel down the

electron transport system, releasing energy.

2) Some of the E is used to create a H⁺ gradient

across the thylakoid membrane that drives

_____________________________

a) ADP + P_i à ATP

2. Light-independent reactions (can occur in the dark, don’t

require light)

a. Take place in the _____________________________

b. The energy stored in ATP is used to reduce carbon

dioxide to form glucose

1) NADPH donates H to CO₂

a) NADPH à NADP⁺

2) The energy required to reduce CO₂ is derived from

ATP

b) ATP à ADP + P_i

3. Overview of Reactants and Products

	Uses (________________________)	Produces (________________________)
Light-dependent (occurs on thylakoid membranes)
Light-independent (occurs in the stroma)

E. _____________________________ – a group of protein, chlorophyll,

& carotenoid molecules contained on the thylakoid membranes. The

photosystems were numbered as they were discovered, but they are

actually used in reverse order.

1. Photosystem II

a. A photon of light strikes photosystem II, energizing an

electron

b. The energized electron moves down the electron

transport system

1) This E is used to convert ADP + P_i to ATP

c. The electron is passed to photosystem I

2. Photosystem I

a. The electron is re-energized by sunlight and passes to a

carrier molecule NADP⁺. H⁺ from the stroma combines with

electrons to form NADPH.

b. The NADPH will be utilized in the light-independent

reactions to form _____________________________.

3. The original electron from Photosystem II is replaced by splitting

water.

a. H₂O à 2H⁺ + 2 e^- + ½ O₂

F. There are 3 types of photosynthesis: __________________________

photosynthesis

1. Photosynthesis always involves taking C from 6 CO₂ and

“_______________” it to form a 6 C molecule, glucose.

a. Remember, plants get CO₂ from the air. They must open

their somata in order allow CO₂ into the leaf’s mesophyll

where photosynthesis is taking place.

b. When the stomata are open, water vapor leaves the plant

through transpiration

2. C₃ photosynthesis is the ancestral pathway for carbon fixation

and occurs in all taxonomic plant groups.

a. C₃ photosynthesis initially fixes CO₂ into a 3 C molecule

that will eventually become glucose.

b. Benefits of C₃ photosynthesis

i. _________________________ system (it takes

the least ATP to make glucose).

c. Costs of C₃ photosynthesis

i. _______________ must be abundant. In order for

C₃ photosynthesis to be efficient, the stomata must

stay open to let in lots of CO₂.

ii. When temperatures are high, and water is low, C₃

plants begin to go through photorespiration.

d. ___________________________ consumes oxygen,

releases carbon dioxide, generates no ATP, and

decreases photosynthetic output.

i. Generally occurs on hot, dry, bright days, when

the stomata close to conserve water.

ii. This allows the concentration of O₂ to exceed that

of CO₂ in the leaf.

e. In C₃ plants, the ____________________________ cells

(cells that surround and protect leaf veins) usually do not

contain chloroplasts.

f. Examples of C₃ plants: most trees, grain crops, potatoes,

sugar beets.

3. C₄ photosynthesis occurs in the more advanced plant taxa and

is especially common among ______________, such as grasses

and sedges, but not very common among dicots.

a. C₄ photosynthesis initially fixes CO₂ into a 4 C molecule

that will eventually become glucose.

b. Benefits of C₄ photosynthesis

i. At ________________________, C₄ plants have

photosynthetic rates that are two to three times

faster than those of C₃ plants.

ii. C₄ plants lose less water during photosynthesis.

c. Costs of C₄ photosynthesis

i. Under milder climatic conditions, C₃ plants are

more efficient at fixing carbon dioxide.

d. In C₄ plants, the bundle sheath cells usually do have

chloroplasts.

4. Crassulacean Acid Metabolism (______________) – usually

found in succulents & other dry environment plants. The process

allows C fixation while maximally conserving H₂O.

a. During the day, the light-dependent reactions produce

ATP & NADPH, but the ____________________________.

C fixation cannot occur.

b. At night, the stomata open, allowing CO₂ to enter. Using

CO₂ + ATP + NADPH, ________________ is formed.

3. The next day, malate is broken down, freeing CO₂ to

produce ______________.

V. Glucose metabolism – how plant cells release & utilize the E stored in sugar

A. Remember a few things…

1. Cells can’t directly use the E stored in sugar

2. Cells break the sugar molecule, releasing its stored E

3. Cells store that released E by making ____________

4. ATP can be used by the cells to do any work

B. All cells begin the breakdown of sugar through ___________________

1. Glycolysis occurs in the _______________________ of the cell.

2. Glycolysis is an anaerobic (not requiring O₂) oxidation of glucose

to produce ____________________________________________.

3. SUM of the formula of GLYCOLYSIS…

Glucose (a 6 C molecule) à2 Pyruvic acid (a 3 C molecule) + _________

4. If you are a bacteria or yeast cell, this may be all the E that you

need, but complex plant & animal cells must be more efficient.

a. Complex cells use _____________________________

to carry out ___________________________________.

C. Review of the structure of a mitochondria

1. Double-membrane bound organelle. The inner membrane is

folded into _________________________.

2. The cristae provide the surface upon which cellular respiration

occurs.

Image modified from: http://www.cartage.org.lb/en/themes/sciences/zoology/AnimalPhysiology/Anatomy/AnimalCellStructure/Mitochondria/mitochondria.jpg

D. Cellular respiration – requires the presences of O₂

1. Occurs on the inner membrane of the mitochondria

2. _______________________________

a. The two pyruvic acids from glycolysis are converted to

two __________________________ (This is a 2 C sugar)

b. The acetyl groups are caught by a carrier molecule,

coenzyme A (_____________).

c. SUM of the TRANSITION STEP

2 Pyruvic acids à 2 CO₂ + 2 Acetyl Groups

2 Acetyl Groups + 2 Coenzyme A à 2 Acetyl CoA

d. The 2 Acetyl CoA enter the _____________________

(also known as the Kreb’s cycle).

3. TCA Cycle

a. This is a complex chemical reaction that can be summed

up as follows…

2 Acetyl CoA à CO₂ + H₂O + _________________

4. In conclusion, the YIELD of CELLULAR RESPIRATION can be

summed up in the following formula…