1. i.* Students know how chemiosmotic gradients in the mitochondria and chloroplast store
energy for ATP production.
Enzymes called ATP synthase, located within the thylakoid membranes in chloroplasts and cristae
membranes in mitochondria, synthesize most ATP within cells. The thylakoid and cristae membranes are
impermeable to protons except at pores that are coupled with the ATP synthase. The potential energy of
the proton concentration gradient drives ATP synthesis as the protons move through the ATP synthase
pores. The proton gradient is established by energy furnished by a flow of electrons passing through the
electron transport system located within these membranes.

1. j.* Students know how eukaryotic cells are given shape and internal organization by a
cytoskeleton or cell wall or both.
The cytoskeleton, which gives shape to and organizes eukaryotic cells, is composed of fine protein
threads called microfilaments and thin protein tubes called microtubules. Cilia and flagella are composed
of microtubules arranged in the 9 + 2 arrangement, in which nine pairs of microtubules surround two
single microtubules. The rapid assembly and disassembly of microtubules and microfilaments and their
capacity to slide past one another enable cells to move, as observed in white blood cells and amoebae,
and also account for movement of organelles within the cell. Students can observe prepared slides of
plant mitosis in an onion root tip to see the microtubules that make up the spindle apparatus. Prepared
slides of white fish blastula reveal animal spindle apparatus and centrioles, both of which are composed of
microtubules.