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Wize University Biology Textbook > Photosynthesis

Plant Structures for Photosynthesis

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Plant Structures for Light-Dependent Reactions

The main organelle responsible for the light-dependent reactions of photosynthesis is the chloroplast. It harvests energy light to produce sugar. Chloroplasts are separated into three compartments by three membranes:
  • Outer Chloroplast Membrane – Highly permeable.
  • Intermembrane Space – Space found between the inner and outer membranes.
  • Inner Chloroplast Membrane – Highly impermeable except where specific transporters are present. Impermeable to ATP and NADPH.
  • Stroma – The aqueous fluid within the inner chloroplast membrane; analogous to the matrix of mitochondria. Site of sugar production.
  • Thylakoid Membrane – Highly folded membrane which forms a set of flattened, disc-like sacs (thylakoids) which are arranged in stacks (grana). Contains chlorophyll, site of electron transport chain, and ATP synthase.
  • Thylakoid Space – Internal compartment of thylakoid.


Chlorophyll

  • Chlorophyll – Light-capturing pigments found in chloroplast, are responsible for the first step in photosynthesis.
  • When pigment absorbs light an electron jumps to a higher energy level; as it returns to its ground state, the released energy is transferred to the neighboring chlorophyll molecule.
  • Pigments are organized into antennae complexes that associate with the two photosystems of photosynthesis.

Practice: Light Absorption Location

Where does light absorption occur in plants?

Practice: Plant Structures

The pigment called ___________ present in chloroplasts is able to absorb light from the sun. They are organized in ___________ complexes on the ____________ membrane.
Extra Practice
Biochemists can lyse thylakoid membranes into fragments, which can fold on themselves to form vesicles. The vesicles can be either inside-out or right-side-out. Suppose you isolated a vesicle and found that the pH outside of the vesicle was very high and the pH inside the vesicle was low. What does that tell you about the orientation of the vesicle?
Practice: Light Absorption Location
Where does light absorption occur in plants?
The light reaction in photosynthesis occur in the
Photosynthesis
Which of the following is primarily responsible for photosynthesis?
Practice: Light Absorption Location
Where does light absorption occur in plants?
Light is measured in wavelengths and different wavelengths of light can activate photosynthesis to varying degrees. Which of the following parts of photosynthesis are wavelength dependent?
You pull leaves from a plant and put them in a jar containing water and atmospheric air, and close the lid. The lid has a sensor that can measure the percentage of oxygen in the jar. You are trying to determine which wavelengths of light are the best to maximize the rate of photosynthesis. Which of the following best describes your result?
You are in the lab and want to determine if a population of single celled eukaryotes are undergoing photosynthesis or cellular respiration, which of the following experiments would successfully help you answer this question?
The given figure shows the effect of different compounds on the amount of chlorophyll in a Chlamydomonas cell, a single cells photosynthetic eukaryote. Based on the figure, which of the following statements most accurately describes what the amount of chlorophyll is indicating?
Where does light absorption occur in plant chloroplast?
Biochemists can lyse thylakoid membranes into fragments, which can fold on themselves to form vesicles. The vesicles can be either inside-out or right-side-out. Suppose you isolated a vesicle and found that the pH outside of the vesicle was very high and the pH inside the vesicle was low. What does that tell you about the orientation of the vesicle?