5.2.2 The Structure of a Chloroplast

Question 1

chloroplasts

Answer 1

• organelles found primarily in mesophyll cells and are the site of photosynthesis.
• double-membrane organelles that have green spots within them. These spots are interconnected stacks of hollowed out membrane called granum (the plural is grana). Each granum is made up of individual units of
  enclosed membrane called thylakoids. Thus, there is a third membrane within the two outer membranes.
• Each thylakoid is composed of a lipid bilayer with proteins embedded in it. The proteins are accumulated into aggregates. The aggregates are the light-harvesting antennae of the chloroplasts. Chlorophyll is also found there.
• Chlorophyll is a pigment that absorbs light. The porphyrin ring, shown in the diagram to the left, is the
  light-reactive end of the molecule. This ring is involved in the light reactions of photosynthesis.
• At the lower end (not shown) of the molecule is the nonpolar, hydrocarbon tail. This region interacts with other nonpolar regions of proteins and the membrane to anchor the molecule into the membrane.

Question 2

The fluid outside of the granum in a chloroplast is called the ___________.

Answer 2

• stroma

Question 3

Stacks of membranous compartments in chlorplasts are referred to as

Answer 3

• grana

Question 4

Chlorophyll is a green pigment found embedded in

Answer 4

• the membrane that makes up the grana.

Question 5

True or false?

Chloroplasts are organelles that are composed of three membranes.

Answer 5

• true

Question 6

Chlorophyll contains a porphyrin ring that has a hydrocarbon tail attached.

Which of the following atoms is found in the center of the porphyrin ring?

Answer 6

• Mg

Question 7

Which structure is found within the thylakoid membrane?

Answer 7

• a light-harvesting antenna