Chapter 10: Photosynthesis: Part 2

Examples of CAM Metabolism plants

(1) Jade, (2) Agave (3) Cactus (4) Orchids (5) Pineapple (6) Spanish Moss (7) Some Ferns

Xerophytes include

(1) Roseate Pattern, (2) Stomata - Few on the bottom of leaf or sunken, (3) Waxy cuticle, (4) Small leaves, (5) Pubescent, (6) Silver color (7) Thick and leathery texture, (8) Curled Leaves

what do Hydrophytes look like?

(1) Stomata is mainly on top of Leaf, (2) Waxy Cuticle, (3) Larger leaves.

What does mesophyte look like?

(1) Stomata is on top and bottom of the leaf, (2) Moderate Sized Leaves, (3) Usually not waxy.

Photosynthesis makes an estimated

160 Billion metric tons of carbohydrate per year.

H2O =

2H+, 2e, and 1/2 O2

Calvin cycle produces

3-carbon sugar called glyceraldehyde-3-phosphate (G3P).

Product of reaction

6-carbon intermediate so unstable that it immediately splits in haly, forming 3-phospho-glycerate.

Photorespiration

A metabolic pathway that consumes oxygen and ATP, releases CO2 and decreases photosynthetic output. Photorespiration generally occurs on hot, dry days when stoma closes and oxygen concentration in the leaf exceeds that of carbon dioxide.

Next reaction

A pair of electrons donated from NADPH reduces 1-3-biphosphoglycerate, which also loses a phosphate group becoming G3P.

C3 plants

A plant that uses the Calvin cycle for the initial steps that incorporate CO2 into organic material, forming a 3-carbon compound as the first stable intermediate.

Glyceraldehyde-3-phosphate

A three-carbon carbohydrate that is the direct product of the Calvin Cycle; it is also an intermediate in glycolysis.

Calvin Cycle spends

ATP as an energy source and consumes NADPH as reducing power for adding high energy electrons to make the sugar.

In CAM Met., CO2 is

Absorbed and converted to malate at night (pH of 4).

Crassulean Acid Metabolism (CAM)

Adaptation for photosynthesis in arid conditions. I nthis process, a plants takes up CO2 at night; during the day, CO2 is released from organic acids for use in Calvin Cycle.

PEP Carboxylase has a higher

Affinity for CO2 than does rubisco and no affinity for O2. Can fix carbon efficiently when rubisco cannot.

Phloem goes in

All directions (H2O and food).

Calvin Cycle is

Anabolic, building carbohydrates from smaller molecules and consuming energy.

Plants impaired in ability to carry out photorespiration

Are more susceptible to damage caused by light.

Xerophytes are in

Arid environments.

Photorespiration could be evolutionary relic from when

Atmosphere had less O2 and more CO2 than it does today.

Cyclic electron flow may

Be photoprotective, protecting cells from light induced damage.

Phycocyanin

Blue.

Fucocxanthin

Brown.

Malic acid diffuses to the

Bundle Sheath cells releasing CO2.

C4 plants' two disctinct types of photosynthetic cells

Byndle-sheath cells and mesophyll cells.

Malate releases

CO2 in the bundle sheath cells when C3 photosynthesis is completed.

For net synthesis of one G3P molecule

Calvin Cycle consumes a total of 9 molecules of ATP and 6 molecules of NADPH.

Rubisco

Calvin Cycle enzyme that adds CO2 to ribulose biphosphate.

The light reactions of photosynthesis

Capture solar energy and use it to make ATP and transfer electrons from water to NADP+ forming NADPH.

Calvin Cycle divides into three phases

Carbon fixation, reduction, and regeneration of the CO2 acceptor.

Carotenoids include

Carotene (orange) and xanthophyll (yellow).

Chloroplasts and mitochondria generate ATP by

Chemiosmosis.

In CAM Met., stomata are

Closed during the day and open only at night.

CAM Metabolism allows plants to

Conserve water

Heterotrophic Nutrition

Consumers, Decompsosers (Fungi & Bacteria)

Mesophyll and Byndle Sheath Cells

Contain PS I but no PS II, so cyclicelectron flow is their only photosynthetic mode of generating ATP.

Reduction

Each molecule of 3-phosphoglycerate receives an additional group from ATP, becoming 1-3 biphosphoglycerate.

The CO2 needed for photosynthesis

Enters a leaf via stomata, the pores through the leaf surface.

PEP Carboxylase

Enzyme present only in mesophyll cells that adds CO2 to phosphoenol-pyruvate, forming the 4-carbon product oxaloacetate.

Rubisco (RuBP carboxylase)

Enzyme that catalyzes the first step of the Calvin Cycle.

The blade is the

Flattened portion of the leaf that collects light energy for photosynthesis.

Electron flow pushes electrons

From water, where they are at a low state of potential energy, to NADPH, where they're at high potential energy.

Light-driven electron current

Generates ATP.

Mesophyll cells

In C4 plants, a type of loosely arranged photosynthetic cell located between bundle sheath and leaf surface.

Bundle-sheath cells

In C4 plants, a type of photosynthetic cell arranged into tightly packed sheath around the beins of a leaf.

Difference between CAM and C4 pathway

In C4 plants, the initial steps of carbon fixation are separated structurally from the Calvin Cycle, whereas in CAM plants, the two steps occur at separate times but same cell.

Regeneration of the CO2 acceptor (RuBP)

In complex series of reaction carbon skeletons of five molecules of G3P are arearrganed by the Calvin Cycle into 3 molecules of RuBP, spending 3 more molecules of ATP.

Carbon enters the Calvin Cycle

In form of CO2 and leaves in form of sugar.

Carbon fixation

Intial incorporation of carbon from CO2 into organic compund by an autotrophic organism.

Spongy mesophyll

Leaf layer involved in gas exchange.

Palisade mesophyll

Leaf layer involved in photosynthesis.

Thylakoid membrane converts

Light energy to chemical energy stored in ATP and NADPH,

Examples of Hydrophytes

Lily, lotus, horsetail, duckweed.

Neither of the light reactions nor the Calvin Cycle can

Make sugar from CO2.

No Light + CO2+3c =

Malate + H2 > Sugar

Most photosynthesis occurs in

Mesophyll of the blade.

C4 photosynthesis

Minimizes photorespiration and enhances sugar production.

Mesophytes appear in

Moderate Environments.

Upper epidermis

Non-photosynthetic layer involved in protection from insects, water, evaporation and fungi. May contain guard cells that regulate gas exchange.

In C4 photosynthesis CO2 bonds to PEP forming

Oxaloaceteate, which becomes malic acid.

Photosynthesis is responsible for

Oxygen in out atmosphere.

Autotrophic nutrition

Photoautotrophs, chemoautotrophs.

In many plants

Photorespiration drains away as much as 50% of the carbon fixed by the Calvin Cycle.

The leaf is the organ of

Photosynthesis in most plants.

C4 plants

Preface Calvin Cycle with an alternate made of carbon fixation that forms a 4-carbon compund as its first product.

Epidermis can be modified into

Prickles.

C4 photosynthesis is solution to

Problem of photorespiration.

Calvin Cycle uses ATP and NADH to

Produce sugar from CO2.

In C4 photosynthesis, CO is

Pumped from the mesophyll to the bundle sheath cells as an organic acid, malate (4c).

C4 Photosynthesis Pathway

Pyruvate+Pi > PEP + CO2 >Oxaloacetate + 2H > Malate

Phycoerythrin

Red.

Phycobilins

Reds and Blues.

As CO2 becomes source within air spaces of leaf

Rubisco adds O2 to the Calvin Cycle instead of CO2. Peroxisomes and mitochondria rearrange and split this compund, releasing CO2.

Leaf of cactus is modified into

Spine.

Mesophyll cells of CAM plants

Store the organic acids they make during the night in their vacuoles until morning, when the stomata close.

In plants, ATP is formed in the

Stroma, where it is used to help drive sugar synthesis during the Calvin Cycle.

Plants stockpile extra sugar by

Synthesizing starch, storing some in the chloroplasts themselves and some in storage cells of roots, tubers, seeds and fruits.

Within bundle-sheath cells

The 4-carbon compunds release CO2, which is reassimilated into organic materal by rubisco and the Calvin Cycle.

Calvin cycle is confined to

The chloroplasts of the bundle sheath cells.

For next synthesis of one molecule of G3P

The cycle must take place 3 times, fixing three molecules of CO2.

In Cam Met., malate is released during

The day.

Stomata are also

The main avenues of transpiration, the evaporative loss of water from leaves.

Cellulose is

The main ingredient of cell walls and most abundant organic molecule in plant.

Green cells are

The only autotropic parts of the plant.

When chloroplasts in an environmental setting are illuminated

The pH in the thylakoid space drops to about 5 (concentration increases) and pH of stroma increases to about 8 (H+ decreases).

NADPH, like ATP, is produced on

The side of the membrane facing the stroma which is where the Calvin Cycle takes place.

Internal tissue can be modified into

Thorns.

Mesophyll cells export their 4-carbon products

To bundle sheath cells through plasmodesmata after C4 plant fixes carbon from CO2.

Mitochondria use chemiosmosis to

Transfer chemical energy from food molecules to ATP; whereas chloroplasts transform light energy into chemical energy in ATP.

Xylem goes in

Upward direction (H2O and minerals).

Cuticle

Wavy layer involved in proection from insects, water, evaporation, and fungi.

Hydrophytes appear in

Wet Environments.

79% N2 + 21% O2

Zero.