Chapter 10

Plant Metabolism

I. Introduction

This chapter will only deal with basic primary metabolism which includes:

A. Photosynthesis

B. Respiration

II. Photosynthesis

A. The Essence of Photosynthesis

1. Photosynthesis defined • energy from sunlight is converted into chemical bond

energy in the form of carbohydrates

2. Summary equation for photosynthesis

chlorophyll6CO2 + 12 H2O + light energy --------------> C6H12O6 + 6 O2 + 6 H2O

enzymes

3. Principle ingredients

a. Carbon dioxide (CO2)

b. Water

c. Light

d. Chlorophyll

1) Several types

2) All magnesium containing molecules

3) Light harvesting complex called a photosynthetic unit• 250-400 pigment molecules

B. Introduction to the Major Steps of Photosynthesis 1. The Light reactions a. Reactions take place in thylakoid membranes of

chloroplast • light required

b. Water split, producing hydrogen ions and electrons, O2 gas released

c. ATP created d. NADPH + H+ created

2. The Dark reactions (Calvin cycle) a. Reactions take place in stroma of chloroplast • light not required, hence "dark" reactions b. Calvin cycle 1) Carbon dioxide from air combined with 5-carbon

sugar 2) Glucose formed through several reaction steps

C. A Closer Look at Photosynthesis 1. Historical perspective

2. The Light reactions reexamined a. Nature of light 1) Wave and particle theory of light 2) Photoelectric effect 3) Photons • discrete packets of light energy

b. Chlorophyll pigments • each pigment has typical absorption spectrum

c. Consequences of light absorption by chlorophyll

1) Emit light immediately (fluorescence) 2) Emit light after a delay (phosphorescence) 3) Absorbed energy converted to heat 4) Absorbed energy converted and stored in chemical

bond energy (photosynthesis)

d. Photosystem I contains 1) 200 or more chlorophyll a molecules 2) Small amount of chlorophyll b 3) Carotenoid pigment with protein attached 4) Special reaction-center molecule of chlorophyll a

called P700 5) Iron-sulfur proteins (electron acceptors)

e. Photosystem II contains 1) Chlorophyll a molecules 2) ß-carotene pigments attached to protein 3) Small amount of chlorophyll b 4) Special reaction-center molecule of chlorophyll a

called P680 5) Primary electron acceptor molecule called pheophytin

f. Photolysis

g. Photophosphorylation

h. Chemiosmosis

3. The Dark reactions reexamined

a. The Calvin cycle (3-carbon pathway)

b. The 4-carbon pathway

4. CAM photosynthesis

III. Respiration

A. The Essence of Respiration

1. Respiration defined

• energy releasing process where simple sugars are broken down during a series of stages controlled by enzymes

2. Summary equation for respiration

enzymesC6H12O6 + 6 O2 --------------> 6 CO2 + 6 H2O + nenergy

3. Anaerobic respiration and fermentation

Two forms

enzymes

C6H12O6 -----------------> ethyl alcohol + carbon dioxide + energy (ATP)

enzymes

C6H12O6 ------------------> lactic acid + energy (ATP)

B. Introduction to the Major Steps of Respiration

1. Glycolysis

2. Aerobic respiration

a. The Krebs cycle

b. The Electron transport chain

3. Anaerobic respiration and fermentation

4. Factors affecting the rate of respiration a. Temperature b. Water c. Oxygen

C. A Closer Look at Respiration

1. Glycolysis reexamined

a. Phosphorylation

b. Sugar cleavage

c. Pyruvic acid formation

2. The Krebs cycle reexamined

3. The Electron transport chain and oxidative phosphorylation

IV. Assimilation and Digestion

A. Assimilation Defined

• use of photosynthetic products in the building of protoplasm and cell walls

B. Digestion Defined

• conversion of starch and other insoluble carbohydrates to soluble forms

C. Examples