Biology

Front 1

Chloroplasts

Back 1

site of photosynthesis. Consists of a double membrane, Stroma and grana (made of thylakoids)

Front 2

Stroma

Back 2

gelatinous fluid inside inner membrane – contains DNA, RNA, ribosomes. Grana: stack of thylakoids suspended in the stroma.

Front 3

Thylakoid

Back 3

membrane studded with photosynthetic pigment, surrounding an enclosed space called the “thylakoid space

Front 4

Photosynthesis requires:

Back 4

H2O – splitting it supplies energy for chlorophyll

Front 5

Gas Exchange:

Back 5

CO2 Into leaf and cells (reactant for photosynthesis. O2 Out of the leaf and cells (product of photosynthesis) H2O is lost when gases can be exchanged for photosynthesis.

Front 6

Stomata:

Back 6

openings in the epidermis and cuticle of the leaf or stem of plant where gas exchange can occur.

Front 7

Guard Cells:

Back 7

specialized cells found on either side of the stomata.

Front 8

a. When their central vacuole fills with water guard cells swell, becoming turgid, leaving the stomata opened.

Back 8

b. When turgor pressure drops (enough water is not available) the guard cells become flaccid and collapse together, blocking the stomata.

Front 9

Basic Formula of Photosynthesis: (Sunlight)

Back 9

6CO2 + 6H2O  C6H12O6 + 6O2 Carbon Dioxide + Water (in the presence of sunlight) yields Glucose and Oxygen

Front 10

Properties of Light - Why plants are green Light acts as a particle (photon) and a wave, with the amount of energy varying based on the wavelength

Back 10

Long wavelength = low energy Short wavelength = high energy Photosynthesis utilized mid-range wavelengths of light in the visible light spectrum.

Front 11

Chlorophyll a and b:

Back 11

pigment molecules that absorb the light. The range of the spectrum that is not absorbed is reflected back.

Front 12

Chlorophyll a and b pigments will appear green, they do not absorb green light. (They absorb red and blue light)

Back 12

.

Front 13

Carotenoids:

Back 13

absorb purple to green light, and reflect yellow to red, therefore they appear orange or red. (carrots, tomatoes, etc)

Front 14

Chlorophyll a is the most abundant and is the primary photosynthetic pigment in plants

Back 14

.

Front 15

Photosystem:

Back 15

In the Thylakoid Membrane - Consists of a reaction center and antenna pigments Molecules of chlorophyll b, carotenoids, and proteins

Front 16

Reaction Center:

Back 16

a pair chlorophyll a molecules and associated proteins. This pair of chlorophyll a molecules uses the energy collected by the entire system for photosynthetic reactions

Front 17

Antenna Pigments:

Back 17

all other pigments in the photosystem – collect energy and send it to the reaction center where it can be released

Front 18

Light Reaction:

Back 18

occur in the thylakoid membrane, convert solar energy into chemical energy – storing it in ATP and NADPH

Front 19

Carbon Reactions (formerly called dark reactions):

Back 19

occur in the stroma, using ATP and NADPH to reduce CO2 to glucose (remember reduced molecules gain electrons, thus gaining energy).

Front 20

H2O is split by chlorophyll a – 2 molecules split = releasing energy, O, and 2 H+ (single protons) End Result

Back 20

.

Front 21

Light reaction:

Back 21

produces ATP, NADPH (both used to power the Calvin Cycle) and O2 (from water being split for photosystem II)

Front 22

Note: ATP is a result of the proton gradient created by the electrons that leave photosystem II and the reduction of NADPH comes from photosystem I

Back 22

.

Front 23

How is energy lost?

Back 23

1. Loss of energy as heat 2. Photorespiration: Rubisco uses O2 instead of CO2. This removes up to 30% of the carbon that has already been fixed by the Calvin cycle. (essentially undoing the work of photosynthesis)

Front 24

The enzyme Rubisco’s active site will bind with O2 or CO2. When O2 is the substrate; photorespiration occurs.

Back 24

.

Front 25

Low concentration of O2 decreases the chance that photorespiration will occur.

Back 25

.

Front 26

To keep the O2 concentration low, stomata must be open for gas exchange.

Back 26

.

Front 27

Decreases O2 and increase CO2 via diffusion

Back 27

.

Front 28

Open stomata = transpiration

Back 28

.

Front 29

Transpiration:

Back 29

loss of water from a plant through the stomata. In dry arid regions, keeping the stomata open will cause the plant to lose too much water, wilt and die. Keeping the stomata closed will result in photorespiration...so: