bio test 12/8

process of photosynthesis (explanation)

Plants use carbon dioxide, water and light energy to produce high-energy sugar (glucose). Oxygen is also given off in the process.

chemical formula of photosynthesis

6CO2 + 6H20 + light energy -> C6H12O6 + 6O2

main purpose of photosynthesis

To produce glucose (energy) to support all the food chains on earth

autotroph

-makes own food to meet energy needs

-plants

heterotroph

-consume organisms to meet energy needs

-animals

cuticle

Prevents water loss; located on top of the upper epidermis.

Epidermis

The upper and lower outer layer of cells; each only 1 cell thick

Xylem

Xylem transports water through the plant. Located in a vein in the mesophyll layer

Phloem

Phloem transports food (glucose) through the plant. Located in a vein in the mesophyll layer.

Mesophyll (palisade & spongy cells)

The middle layer where photosynthesis takes place. Lots of chloroplasts located in these cells for photosynthesis.

Stomata

Openings in the lower epidermis that take in CO2

guard cells

The two cells around the stomata that control the opening and closing of the stomata. When the plant has enough water, the guard cells stay open so that CO2 can enter. When the plant is losing water, the guard cells close to conserve water.

what is in the vein?

xylem and phloem

diagram leaf

remember: palisade mesophyll is on top of the spongy mesophyll

chloroplast diagram

granum is a stake of thylakoids

The MESOPHYLL layer contain the most chloroplasts. What does this mean for photosynthesis?

The process of photosynthesis mostly occurs within the mesophyll layer of the leaf since these cells contain the most chloroplasts. Recall that chloroplasts are the organelles within the cell where photosynthesis takes place.

what is a pigment

a molecule that absorbs light

principal pigment of plants

chlorophyll

-- but breaks down in the fall revealing other pigments like carotenoids and xanthophyll

what does this pigment (chlorophyll) reflect?

green

what color does this pigment absorb well?

-blue

-red

relationship between wavelength and energy:

the shorter the wavelength the more energy

2 main phases of photosynthesis:

-light reactions

-calvin cycle (dark reactions)

explain the light reactions

occur in the THYLAKOID MEMBRANES with in a chloroplast. Chlorophyll in the thylakoid membrane captures light energy from the sun and uses it to produce ATP and NADPH (these are energy molecules). Also, during the light reactions, water is split into H+ and oxygen

what is a photosystem

a collection of pigments that capture light energy

when light energy is absorbed by chlorophyll a in the reaction center, what happens to its electrons?

The electrons become excited and move through the electron transport chain. Ultimately, ATP and NADPH are made

What occurs in the Calvin Cycle

occurs in the STROMA. It uses the ATP energy and NADPH from the light reactions to convert CO2 into glucose

enzyme that "fixes" carbon in the Calvin Cycle

Rubisco

Molecule that starts and ends the Calvin Cycle

RuBP

What are the two 3-carbon intermediates that are formed after carbon is "fixed" in the Calvin Cycle?

PGA and PGAL

why the cell only gets 1 glucose for 6 turns of the cycle

Each CO2 delivers 1 carbon to the Calvin Cycle. Since glucose is C6H12O6, it takes 6 turns of the cycle create get the 6 carbons needed to make glucose

In what part of photosynthesis is oxygen produced from splitting water?

Light reactions

In what part of photosynthesis is CO2 used?

Calvin Cycle

What compound (molecule) is formed from CO2?

glucose

Explain how the Calvin Cycle depends on the Light Reactions.

The Calvin Cycle is powered by the energy molecules (ATP and NADPH) that are produced during the Light Reactions. If those molecules are not produced, the Calvin Cycle cannot occur.

What is transpiration?

Evaporation off of leaves. In other words, transpiration is when leaves lose water.

What factors can affect transpiration rates?

Wind, temperature, humidity. Higher winds increase the rate of transpiration. Higher humidity decreases the rate of transpiration. Higher temperatures increase the rate of transpiration.

On a dry, hot day would the stomata most likely be open or closed? What is the drawback of this?

The stomata would close because the plant is losing water due to transpiration on a hot, dry day. The stomata close to prevent more water loss. The drawback is that the plant cannot take in CO2 which is needed for photosynthesis.

What effect does closing stomata have on a plant's CO2 and O2 levels?

Closing the stomata would decrease the plants CO2 levels because CO2 would not be able to enter the leaf. The CO2 that is already in the leaf would get used for photosynthesis. O2 levels would increase as photosynthesis occurs and the O2 cannot leave the leaf.

Name 4 environmental factors and how they affect the rate of photosynthesis.

As light increases rate increases until it reaches full capacity

As temp increases rate increases until peak is reached and enzyme denatures

As O2 level increases rate decreases

As CO2 level increases rate increases until it reaches full capacity