Plant Cells and Intro to Photosynthesis

Objectives

• Explain the function of the cell wall
• Summarize the role of the central vacuole
• Describe the structure and function of the chloroplast
• Summarize photosynthesis
• Explain the significance of the electron transport chain

Things Plant cells have that animal cells lack

• A cell wall
• A large central vacuole
• Plastids like chloroplasts

Cell wall

• Found OUTSIDE the cell membrane
• Contains cellulose, protein, and polysaccharides
• Provides structural support
• Pores allow nutrients in and out
• Keeps the cell from bursting

Central vacuole

• Occupies 30-90% of cell
• Surrounded by membrane called tonoplast
• Maintains turgor pressure against cell wall
• Stores pigments that color flowers
• Contains cell sap, which may contain toxins

Plastids

• Can change their function
• Contain their own DNA
• Have some ribosomes
• May have descended from photosynthetic bacteria

Types of plastids

• Chloroplasts
• Chromoplasts
• Leucoplasts

Chromoplasts make and store pigments that give petals and fruits their orange and yellow colors.

Leucoplasts

• Located in non-photosynthetic locations
• May store starch, lipids, or proteins
• May make fatty acids or amino acids

Chloroplasts

• Capture light energy to make sugar
• Look like flat discs
• 2-10 micrometers in diameter
• Fluid inside is called stroma
• Pigments and electron carriers are found in thylakoids

Chloroplasts

• Stacks of thylakoids are sites of photosynthesis
• Contain ribosomes and circular DNA

The endosymbiotic theory holds that chloroplasts were once independently living bacteria.

Photosynthesis

The light reactions capture energy from sunlight, which plants change to chemical energy that is stored in molecules of NADPH and ATP.

The light reactions also release oxygen gas as a waste product.

The reactions of the Calvin cycle add carbon (from carbon dioxide in the atmosphere) to a simple five-carbon molecule called RuBP.

The Calvin cycle reactions use chemical energy from NADPH and ATP that were produced in the light reactions.

The final product of the Calvin cycle is glucose.